BERKLEY W R CORP, 10-Q filed on 8/2/2024
Quarterly Report
v3.24.2.u1
Cover Page - shares
 6 Months Ended
Jun. 30, 2024
Jul. 29, 2024
Entity Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2024  
Document Transition Report false  
Entity File Number 1-15202  
Entity Registrant Name W. R. BERKLEY CORP  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 22-1867895  
Entity Address, Address Line One 475 Steamboat Road  
Entity Address, City or Town Greenwich  
Entity Address, State or Province CT  
Entity Address, Postal Zip Code 06830  
City Area Code (203)  
Local Phone Number 629-3000  
Title of 12(b) Security Common Stock, par value $.20 per share  
Trading Symbol WRB  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   380,550,600
Entity Central Index Key 0000011544  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2024  
Document Fiscal Period Focus Q2  
Amendment Flag false  
5.700% Subordinated Debentures due 2058    
Entity Information [Line Items]    
Title of 12(b) Security 5.700% Subordinated Debentures due 2058  
Trading Symbol WRB-PE  
Security Exchange Name NYSE  
5.100% Subordinated Debentures due 2059    
Entity Information [Line Items]    
Title of 12(b) Security 5.100% Subordinated Debentures due 2059  
Trading Symbol WRB-PF  
Security Exchange Name NYSE  
4.250% Subordinated Debentures due 2060    
Entity Information [Line Items]    
Title of 12(b) Security 4.250% Subordinated Debentures due 2060  
Trading Symbol WRB-PG  
Security Exchange Name NYSE  
4.125% Subordinated Debentures due 2061    
Entity Information [Line Items]    
Title of 12(b) Security 4.125% Subordinated Debentures due 2061  
Trading Symbol WRB-PH  
Security Exchange Name NYSE  
v3.24.2.u1
Consolidated Balance Sheets Consolidated Balance Sheets - USD ($)
$ in Thousands
Jun. 30, 2024
Dec. 31, 2023
Investments:    
Debt Securities, Available-for-Sale and Held-to-Maturity, after Allowance for Credit Loss $ 21,082,676 $ 20,178,308
Investment funds 1,589,119 1,621,655
Real estate 1,279,306 1,249,874
Equity securities 1,078,092 1,090,347
Arbitrage trading account 1,221,861 938,049
Loans receivable (net of allowance for expected credit losses of $1,813 and $3,004 at June 30, 2024 and December 31, 2023, respectively) 349,325 201,271
Total investments 26,600,379 25,279,504
Cash and cash equivalents 1,580,270 1,363,195
Premiums and fees receivable (net of allowance for expected credit losses of $37,279 and $35,110 at June 30, 2024 and December 31, 2023, respectively) 3,430,991 3,109,334
Due from reinsurers (net of allowance for expected credit losses of $10,255 and $8,404 at June 30, 2024 and December 31, 2023, respectively) 3,501,892 3,534,527
Deferred policy acquisition costs 939,453 861,609
Prepaid reinsurance premiums 814,858 758,927
Trading account receivables from brokers and clearing organizations 40,705 303,614
Property, furniture and equipment 477,034 426,803
Goodwill 184,089 174,597
Accrued investment income 225,214 213,408
Current and deferred federal and foreign income taxes 220,080 220,756
Other assets 894,954 865,556
Total assets 38,909,919 37,111,830
Liabilities:    
Reserves for losses and loss expenses 19,567,190 18,739,652
Unearned premiums 6,332,699 5,922,326
Due to reinsurers 730,407 631,164
Trading account securities sold but not yet purchased 81,273 9,357
Other liabilities 1,573,428 1,503,053
Senior notes and other debt 1,828,422 1,827,951
Subordinated debentures 1,009,449 1,009,090
Total liabilities 31,122,868 29,642,593
Equity:    
Perferred stock, par value $.10 per share: Authorized 5,000,000 shares; issued and outstanding - none 0 0
Common stock, par value $.20 per share: Authorized 500,000,000 shares, issued and outstanding, net of treasury shares, 177,930,502 and 183,411,907 shares, respectively 158,705 158,705
Additional paid-in capital 986,892 964,789
Retained earnings 11,669,567 11,040,908
Accumulated other comprehensive loss (1,033,640) (925,838)
Treasury stock, at cost, 412,875,299 and 408,704,807 shares, respectively (4,007,742) (3,783,133)
Total stockholders’ equity 7,773,782 7,455,431
Noncontrolling interests 13,269 13,806
Total equity 7,787,051 7,469,237
Total liabilities and equity $ 38,909,919 $ 37,111,830
v3.24.2.u1
Consolidated Balance Sheets Consolidated Balance Sheets (Parenthetical) - USD ($)
$ in Thousands
Jun. 30, 2024
Dec. 31, 2023
Statement of Financial Position [Abstract]    
Fixed maturity securities, amortized cost $ 21,911,417 $ 20,915,245
Fixed maturity securities, allowance for credit loss 21,871 36,751
Cumulative effect adjustment resulting from changes in accounting principles 1,813 3,004
Cumulative effect adjustment resulting from changes in accounting principles 37,279 35,110
Reinsurance recoverable, allowance for credit loss $ 10,255 $ 8,404
Preferred stock, par value (in dollars per share) $ 0.10 $ 0.10
Preferred stock issued (in shares) 5,000,000 5,000,000
Preferred stock outstanding (in shares) 0 0
Common stock, par value (in dollar per share) $ 0.20 $ 0.20
Common shares authorized (in shares)   1,250,000,000
Common shares issued (in shares) 380,646,644 384,817,136
Common shares outstanding (in shares) 380,646,644 384,817,136
Treasury stock issued at cost (in shares) 412,875,299 408,704,807
v3.24.2.u1
Consolidated Statements Income (Unaudited) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
REVENUES:        
Net premiums written $ 3,126,779 $ 2,811,515 $ 5,978,070 $ 5,386,339
Change in net unearned premiums (280,364) (258,788) (367,308) (342,180)
Net premiums earned 2,846,415 2,552,727 5,610,762 5,044,159
Net investment income 372,129 245,152 691,967 468,551
Net realized and unrealized (losses) gains on investments (60,306) 68,647 (48,803) 91,258
Change in allowance for expected credit losses on investments 1,794 (9,993) 16,070 (9,594)
Net investment (losses) gains (58,512) 58,654 (32,733) 81,664
Revenues from non-insurance businesses 125,705 113,910 246,696 238,110
Insurance service fees 27,597 25,471 52,917 58,328
Other income 698 0 1,196 106
Total revenues 3,314,032 2,995,914 6,570,805 5,890,918
OPERATING COSTS AND EXPENSES:        
Losses and loss expenses 1,780,596 1,569,654 3,444,374 3,108,409
Other operating costs and expenses 892,935 823,682 1,761,524 1,649,255
Expenses from non-insurance businesses 121,120 113,538 239,727 236,306
Interest expense 31,708 31,856 63,436 63,692
Total operating costs and expenses 2,826,359 2,538,730 5,509,061 5,057,662
Income before income taxes 487,673 457,184 1,061,744 833,256
Income tax expense (115,788) (101,460) (247,824) (181,803)
Net income before noncontrolling interests 371,885 355,724 813,920 651,453
Noncontrolling interests 24 584 460 (1,019)
Net income to common stockholders $ 371,909 $ 356,308 $ 814,380 $ 650,434
NET INCOME PER SHARE:        
Basic (in dollar per share) $ 0.93 $ 0.88 $ 2.03 $ 1.59
Diluted (in dollar per share) $ 0.92 $ 0.87 $ 2.01 $ 1.58
v3.24.2.u1
Consolidated Statements of Comprehensive Income (Unaudited) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Statement of Comprehensive Income [Abstract]        
Net income before noncontrolling interests $ 371,885 $ 355,724 $ 813,920 $ 651,453
Other comprehensive (loss) income:        
Change in unrealized currency translation adjustments 3,227 10,528 (24,343) 15,394
Change in unrealized investment (losses) gains, net of taxes (13,338) (113,284) (83,460) 67,515
Other comprehensive (loss) income (10,111) (102,756) (107,803) 82,909
Comprehensive income 361,774 252,968 706,117 734,362
Noncontrolling interests 23 584 459 (1,018)
Comprehensive income to common stockholders $ 361,797 $ 253,552 $ 706,576 $ 733,344
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Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($)
$ in Thousands
Total
Common stock
Additional paid-in capital
Retained earnings
Accumulated Other Comprehensive Income (Loss)
Unrealized investment losses:
Currency Translation Adjustments
Treasury stock
Noncontrolling interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Cumulative effect adjustment resulting from changes in accounting principles   $ 158,705 $ 944,632 $ 10,161,005 $ (1,264,581) $ (892,905) $ (371,676) $ (3,251,429) $ 19,829
Beginning of period at Dec. 31, 2022   158,705 944,632 10,161,005 (1,264,581) (892,905) (371,676) (3,251,429) 19,829
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Restricted stock units issued     (2)            
Restricted stock units expensed     23,286            
Net income before noncontrolling interests $ 651,453     650,434         1,019
Dividends ($0.41, $0.07, $0.49 and $0.47 per share, respectively)       (186,921)          
Change in unrealized (losses) gains on securities without an allowance for expected credit losses 67,515         60,364      
Change in unrealized (losses) gains on securities with an allowance for expected credit losses           7,150      
Net change in period 15,394           15,394    
Stock exercised/vested               992  
Stock repurchased               (427,619)  
Other (4,225)                
(Distribution) contributions                 320
Other comprehensive income (loss), net of tax $ 82,909       82,909 67,515 15,394   (1)
End of period at Jun. 30, 2023     967,916 10,624,518 (1,181,673) (825,391) (356,282) (3,682,281) 21,167
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Common stock dividends, per share, cash paid (in dollars per share) $ 0.47                
Cumulative effect adjustment resulting from changes in accounting principles   158,705 955,226 10,296,539 (1,078,917) (712,107) (366,810) (3,387,538) 21,608
Beginning of period at Mar. 31, 2023   158,705 955,226 10,296,539 (1,078,917) (712,107) (366,810) (3,387,538) 21,608
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Restricted stock units issued     1,198            
Restricted stock units expensed     11,492            
Net income before noncontrolling interests $ 355,724     356,308         (584)
Dividends ($0.41, $0.07, $0.49 and $0.47 per share, respectively)       (28,329)          
Change in unrealized (losses) gains on securities without an allowance for expected credit losses (113,284)         (116,978)      
Change in unrealized (losses) gains on securities with an allowance for expected credit losses           3,694      
Net change in period 10,528           10,528    
Stock exercised/vested               597  
Stock repurchased               (292,467)  
Other (2,873)                
(Distribution) contributions                 143
Other comprehensive income (loss), net of tax $ (102,756)       (102,756) (113,284) 10,528   0
End of period at Jun. 30, 2023     967,916 10,624,518 (1,181,673) (825,391) (356,282) (3,682,281) 21,167
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Common stock dividends, per share, cash paid (in dollars per share) $ 0.07                
Cumulative effect adjustment resulting from changes in accounting principles     967,916 10,624,518 (1,181,673) (825,391) (356,282) (3,682,281) 21,167
Cumulative effect adjustment resulting from changes in accounting principles $ 7,469,237 158,705 964,789 11,040,908 (925,838) (586,354) (339,484) (3,783,133) 13,806
Beginning of period at Dec. 31, 2023 7,469,237 158,705 964,789 11,040,908 (925,838) (586,354) (339,484) (3,783,133) 13,806
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Restricted stock units issued     (3,145)            
Restricted stock units expensed     25,248            
Net income before noncontrolling interests 813,920     814,380         (460)
Dividends ($0.41, $0.07, $0.49 and $0.47 per share, respectively)       (185,721)          
Change in unrealized (losses) gains on securities without an allowance for expected credit losses (83,460)         (76,763)      
Change in unrealized (losses) gains on securities with an allowance for expected credit losses           (6,696)      
Net change in period (24,343)           (24,343)    
Stock exercised/vested               1,324  
Stock repurchased               (223,763)  
Other (2,170)                
(Distribution) contributions                 (78)
Other comprehensive income (loss), net of tax (107,803)       (107,803) (83,460) (24,343)   1
End of period at Jun. 30, 2024 $ 7,787,051   986,892 11,669,567 (1,033,640) (669,813) (363,827) (4,007,742) 13,269
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Common stock dividends, per share, cash paid (in dollars per share) $ 0.49                
Cumulative effect adjustment resulting from changes in accounting principles   158,705 977,573 11,455,158 (1,023,530) (656,476) (367,054) (3,783,074) 13,680
Beginning of period at Mar. 31, 2024   $ 158,705 977,573 11,455,158 (1,023,530) (656,476) (367,054) (3,783,074) 13,680
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Restricted stock units issued     (2,950)            
Restricted stock units expensed     12,269            
Net income before noncontrolling interests $ 371,885     371,909         (24)
Dividends ($0.41, $0.07, $0.49 and $0.47 per share, respectively)       (157,500)          
Change in unrealized (losses) gains on securities without an allowance for expected credit losses (13,338)         (5,654)      
Change in unrealized (losses) gains on securities with an allowance for expected credit losses           (7,683)      
Net change in period 3,227           3,227    
Stock exercised/vested               1,265  
Stock repurchased               (223,763)  
Other (2,170)                
(Distribution) contributions                 (388)
Other comprehensive income (loss), net of tax (10,111)       (10,111) (13,338) 3,227   1
End of period at Jun. 30, 2024 $ 7,787,051   986,892 11,669,567 (1,033,640) (669,813) (363,827) (4,007,742) 13,269
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Common stock dividends, per share, cash paid (in dollars per share) $ 0.41                
Cumulative effect adjustment resulting from changes in accounting principles $ 7,787,051   $ 986,892 $ 11,669,567 $ (1,033,640) $ (669,813) $ (363,827) $ (4,007,742) $ 13,269
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Consolidated Statements of Cash Flows (Unaudited) - USD ($)
$ in Thousands
 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
CASH FROM OPERATING ACTIVITIES:    
Net income to common stockholders $ 814,380 $ 650,434
Adjustments to reconcile net income to net cash from operating activities:    
Net investment losses (gains) 32,733 (81,664)
Depreciation and (accretion) amortization (145,062) 6,900
Noncontrolling interests (460) 1,019
Investment funds 3,873 (993)
Stock incentive plans 26,856 25,085
Change in:    
Arbitrage trading account 51,013 (30,331)
Premiums and fees receivable (332,640) (272,849)
Reinsurance accounts 81,755 (242,376)
Deferred policy acquisition costs (77,772) (68,414)
Income taxes 27,699 (5,703)
Reserves for losses and loss expenses 852,523 914,169
Unearned premiums 422,409 398,563
Other (129,742) (139,771)
Net cash from operating activities 1,627,565 1,154,069
CASH USED IN INVESTING ACTIVITIES:    
Proceeds from sale of fixed maturity securities 1,089,183 623,886
Proceeds from sale of equity securities 253,498 97,916
Distributions from investment funds 21,011 12,963
Proceeds from maturities and prepayments of fixed maturity securities 2,133,775 1,824,819
Purchase of fixed maturity securities (4,203,540) (2,833,467)
Purchase of equity securities (180,350) (62,485)
Real estate purchased (44,603) (7,049)
Change in loans receivable (148,241) 13,767
Net purchases of property, furniture and equipment (78,468) (25,720)
Change in balances due to security brokers 165,430 99,976
Cash received in connection with business disposition 0 94,076
Other 0 127
Net cash used in investing activities (992,305) (161,191)
CASH USED IN FINANCING ACTIVITIES:    
Repayment of senior notes and other debt 0 (1,954)
Net proceeds from issuance of debt 420 160
Cash dividends to common stockholders (185,721) (186,921)
Purchase of common treasury shares (223,763) (427,619)
Other, net 943 324
Net cash used in financing activities (408,121) (616,010)
Net impact on cash due to change in foreign exchange rates (10,064) (2,656)
Net change in cash and cash equivalents 217,075 374,212
Cash and cash equivalents at beginning of period 1,363,195 1,449,346
Cash and cash equivalents at end of period $ 1,580,270 $ 1,823,558
v3.24.2.u1
General
 6 Months Ended
Jun. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
General General
    The unaudited consolidated financial statements, which include the accounts of W. R. Berkley Corporation and its subsidiaries (the “Company”), have been prepared on the basis of U.S. generally accepted accounting principles (“GAAP”) for interim financial information. Accordingly, they do not include all the information and notes required by GAAP for annual financial statements. The unaudited consolidated financial statements reflect all adjustments, consisting only of normal recurring items, which are necessary to present fairly the Company’s financial position and results of operations on a basis consistent with the prior audited consolidated financial statements. Operating results for interim periods are not necessarily indicative of the results that may be expected for the year. All significant intercompany accounts and transactions have been eliminated.
The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the revenues and expenses reflected during the reporting period. For further information related to areas of judgment and estimates and other information necessary to understand the Company’s financial position and results of operations, refer to the audited consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023.
Reclassifications have been made in the 2023 financial statements as originally reported to conform to the presentation of the 2024 financial statements. The Company reclassified a program management business from the Insurance segment to the Reinsurance & Monoline Excess segment. The reclassified business is a program management business offering support on a nationwide basis for commercial casualty and property program administrators. In addition, share and per share amounts have been adjusted to reflect the 3-for-2 common stock split effected on July 10, 2024.
The income tax provision has been computed based on the Company’s estimated annual effective tax rate. The effective income tax rate differs from the federal income tax rate of 21% primarily due to the geographical mix of earnings and larger amounts being subject to tax at a rate greater than the U.S. statutory rate, which was partially offset by tax benefits related to tax-exempt investment income.
v3.24.2.u1
Per Share Data
 6 Months Ended
Jun. 30, 2024
Earnings Per Share [Abstract]  
Per Share Data Per Share Data
    The Company presents both basic and diluted net income per share (“EPS”) amounts. Basic EPS is calculated by dividing net income by the weighted average number of common shares outstanding during the period (including 17,495,175 and 17,125,284 common shares held in a grantor trust as of June 30, 2024 and 2023, respectively). The common shares held in the grantor trust are for delivery upon settlement of vested but mandatorily deferred restricted stock units ("RSUs"). Shares held by the grantor trust do not affect diluted shares outstanding since the shares deliverable under vested RSUs were already included in diluted shares outstanding. Diluted EPS is based upon the weighted average number of basic and common equivalent shares outstanding during the period and is calculated using the treasury stock method for stock incentive plans. Common equivalent shares are excluded from the computation in periods in which they have an anti-dilutive effect.
    The weighted average number of common shares used in the computation of basic and diluted earnings per share was as follows:
For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Basic400,273 406,296 401,295 409,364 
Diluted403,737 409,643 404,679 412,819 
v3.24.2.u1
Recent Accounting Pronouncements and Accounting Policies
 6 Months Ended
Jun. 30, 2024
Accounting Policies [Abstract]  
Recent Accounting Pronouncements and Accounting Policies Recent Accounting Pronouncements and Accounting Policies
Recently adopted accounting pronouncements:
    All accounting and reporting standards that became effective in 2024 were either not applicable to the Company or their adoption did not have a material impact on the Company.
Accounting and reporting standards that are not yet effective:
    All recently issued but not yet effective accounting and reporting standards are either not applicable to the Company or are not expected to have a material impact on the Company.
v3.24.2.u1
Consolidated Statements of Comprehensive (Loss) Income
 6 Months Ended
Jun. 30, 2024
Equity [Abstract]  
Consolidated Statements of Comprehensive (Loss) Income Consolidated Statements of Comprehensive (Loss) Income
    The following table presents the components of the changes in accumulated other comprehensive (loss) income ("AOCI"):

(In thousands)Unrealized Investment (Losses) GainsCurrency Translation AdjustmentsAccumulated Other Comprehensive
(Loss) Income
As of and for the six months ended June 30, 2024
Changes in AOCI
Beginning of period$(586,354)$(339,484)$(925,838)
Other comprehensive loss before reclassifications(156,023)(24,343)(180,366)
Amounts reclassified from AOCI72,563 — 72,563 
Other comprehensive loss(83,460)(24,343)(107,803)
Unrealized investment gain related to noncontrolling interest1 — 1 
End of period$(669,813)$(363,827)$(1,033,640)
Amounts reclassified from AOCI
Pre-tax$91,852 (1)$— $91,852 
Tax effect (19,289)(2)— (19,289)
After-tax amounts reclassified$72,563 $— $72,563 
Other comprehensive loss
Pre-tax$(109,937)$(24,343)$(134,280)
Tax effect26,477 — 26,477 
Other comprehensive loss$(83,460)$(24,343)$(107,803)
As of and for the three months ended June 30, 2024
Changes in AOCI
Beginning of period$(656,476)$(367,054)$(1,023,530)
Other comprehensive (loss) income before reclassifications(54,711)3,227 (51,484)
Amounts reclassified from AOCI41,373 — 41,373 
Other comprehensive (loss) income(13,338)3,227 (10,111)
Unrealized investment gain to noncontrolling interest1 — 1 
Ending balance$(669,813)$(363,827)$(1,033,640)
Amounts reclassified from AOCI
Pre-tax$52,371 (1)$— $52,371 
Tax effect (10,998)(2)— (10,998)
After-tax amounts reclassified$41,373 $— $41,373 
Other comprehensive (loss) income
Pre-tax$(20,640)$3,227 $(17,413)
Tax effect7,302 — 7,302 
Other comprehensive (loss) income$(13,338)$3,227 $(10,111)
(In thousands)Unrealized Investment (Losses) GainsCurrency Translation AdjustmentsAccumulated Other Comprehensive
(Loss) Income
As of and for the six months ended June 30, 2023
Changes in AOCI
Beginning of period$(892,905)$(371,676)$(1,264,581)
Other comprehensive income before reclassifications99,093 15,394 114,487 
Amounts reclassified from AOCI(31,578)— (31,578)
Other comprehensive income67,515 15,394 82,909 
Unrealized investment loss related to noncontrolling interest(1)— (1)
End of period$(825,391)$(356,282)$(1,181,673)
Amounts reclassified from AOCI
Pre-tax$(39,972)(1)$— $(39,972)
Tax effect 8,394 (2)— 8,394 
After-tax amounts reclassified$(31,578)$— $(31,578)
Other comprehensive income
Pre-tax$87,978 $15,394 $103,372 
Tax effect(20,463)— (20,463)
Other comprehensive income$67,515 $15,394 $82,909 
As of and for the three months ended June 30, 2023
Changes in AOCI
Beginning of period$(712,107)$(366,810)$(1,078,917)
Other comprehensive (loss) income before reclassifications(56,122)10,528 (45,594)
Amounts reclassified from AOCI(57,162)— (57,162)
Other comprehensive (loss) income(113,284)10,528 (102,756)
Unrealized investment loss related to noncontrolling interest— — — 
Ending balance$(825,391)$(356,282)$(1,181,673)
Amounts reclassified from AOCI
Pre-tax$(72,357)(1)$— $(72,357)
Tax effect 15,195 (2)— 15,195 
After-tax amounts reclassified$(57,162)$— $(57,162)
Other comprehensive (loss) income
Pre-tax$(144,043)$10,528 $(133,515)
Tax effect30,759 — 30,759 
Other comprehensive (loss) income$(113,284)$10,528 $(102,756)
____________
(1) Net investment (losses) gains in the consolidated statements of income.
(2) Income tax expense in the consolidated statements of income.
v3.24.2.u1
Statements of Cash Flows
 6 Months Ended
Jun. 30, 2024
Supplemental Cash Flow Elements [Abstract]  
Statements of Cash Flows Statements of Cash Flows    Interest payments were $63,051,000 and $62,983,000 for the six months ended June 30, 2024 and 2023, respectively. Income taxes paid were $165,739,000 and $158,000,000 for the six months ended June 30, 2024 and 2023, respectively.
v3.24.2.u1
Investments In Fixed Maturity Securities
 6 Months Ended
Jun. 30, 2024
Investments, Debt and Equity Securities [Abstract]  
Investments In Fixed Maturity Securities Investments in Fixed Maturity Securities
    At June 30, 2024 and December 31, 2023, investments in fixed maturity securities were as follows:
 
(In thousands)Amortized
Cost		Allowance for Expected Credit Losses (1)Gross UnrealizedFair
Value		Carrying
Value
GainsLosses
June 30, 2024
Held to maturity:
State and municipal$40,983 $(34)$1,766 $— $42,715 $40,949 
Residential mortgage-backed2,615 — 60 — 2,675 2,615 
Total held to maturity43,598 (34)1,826 — 45,390 43,564 
Available for sale:
U.S. government and government agency1,869,971 — 6,877 (54,472)1,822,376 1,822,376 
State and municipal:
Special revenue1,586,511 — 2,558 (80,860)1,508,209 1,508,209 
State general obligation416,788 — 1,862 (15,926)402,724 402,724 
Pre-refunded88,086 — 269 (377)87,978 87,978 
Corporate backed171,007 (339)582 (9,918)161,332 161,332 
Local general obligation390,455 — 1,254 (12,685)379,024 379,024 
Total state and municipal2,652,847 (339)6,525 (119,766)2,539,267 2,539,267 
Mortgage-backed:
Residential2,206,563 — 7,330 (178,950)2,034,943 2,034,943 
Commercial567,094 (1,140)313 (8,216)558,051 558,051 
Total mortgage-backed2,773,657 (1,140)7,643 (187,166)2,592,994 2,592,994 
Asset-backed4,071,678 (889)5,279 (61,622)4,014,446 4,014,446 
Corporate:
Industrial4,026,477 — 9,683 (142,415)3,893,745 3,893,745 
Financial3,253,805 — 7,899 (65,121)3,196,583 3,196,583 
Utilities735,920 — 1,614 (25,567)711,967 711,967 
Other616,007 — 1,247 (7,129)610,125 610,125 
Total corporate8,632,209 — 20,443 (240,232)8,412,420 8,412,420 
Foreign government1,867,457 (19,469)3,306 (193,685)1,657,609 1,657,609 
Total available for sale21,867,819 (21,837)50,073 (856,943)21,039,112 21,039,112 
Total investments in fixed maturity securities$21,911,417 $(21,871)$51,899 $(856,943)$21,084,502 $21,082,676 
____________
(1) Represents the amount of impairment that has resulted from credit-related factors. The change in the allowance for expected credit losses is recognized in the consolidated statements of income. Amount excludes unrealized losses relating to non-credit factors.
(In thousands)Amortized
Cost		Allowance for Expected Credit Losses (1)Gross UnrealizedFair
Value		Carrying
Value
GainsLosses
December 31, 2023
Held to maturity:
State and municipal$50,547 $(43)$3,132 $— $53,636 $50,504 
Residential mortgage-backed2,868 — 107 — 2,975 2,868 
Total held to maturity53,415 (43)3,239 — 56,611 53,372 
Available for sale:
U.S. government and government agency1,762,997 — 11,403 (57,669)1,716,731 1,716,731 
State and municipal:
Special revenue1,682,550 — 5,651 (82,006)1,606,195 1,606,195 
State general obligation394,429 — 3,550 (16,405)381,574 381,574 
Pre-refunded103,029 — 1,634 (185)104,478 104,478 
Corporate backed166,873 (757)696 (11,973)154,839 154,839 
Local general obligation396,041 — 3,188 (11,893)387,336 387,336 
Total state and municipal2,742,922 (757)14,719 (122,462)2,634,422 2,634,422 
Mortgage-backed:
Residential1,773,206 — 12,780 (163,844)1,622,142 1,622,142 
Commercial657,157 (158)626 (13,312)644,313 644,313 
Total mortgage-backed2,430,363 (158)13,406 (177,156)2,266,455 2,266,455 
Asset-backed4,252,883 (1,164)8,527 (73,206)4,187,040 4,187,040 
Corporate:
Industrial3,679,219 (40)24,312 (143,936)3,559,555 3,559,555 
Financial2,838,220 (4,986)14,681 (68,681)2,779,234 2,779,234 
Utilities701,865 — 6,471 (23,412)684,924 684,924 
Other635,975 — 1,605 (7,234)630,346 630,346 
Total corporate7,855,279 (5,026)47,069 (243,263)7,654,059 7,654,059 
Foreign government1,817,386 (29,603)15,865 (137,419)1,666,229 1,666,229 
Total available for sale20,861,830 (36,708)110,989 (811,175)20,124,936 20,124,936 
Total investments in fixed maturity securities$20,915,245 $(36,751)$114,228 $(811,175)$20,181,547 $20,178,308 
____________
(1) Represents the amount of impairment that has resulted from credit-related factors. The change in the allowance for expected credit losses is recognized in the consolidated statements of income. Amount excludes unrealized losses relating to non-credit factors.

The following table presents the rollforward of the allowance for expected credit losses for held to maturity securities for the six months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$43 $114 
Provision for expected credit losses(9)(61)
Allowance for expected credit losses, end of period$34 $53 

The following table presents the rollforward of the allowance for expected credit losses for held to maturity securities for the three months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$38 $107 
Provision for expected credit losses(4)(54)
Allowance for expected credit losses, end of period$34 $53 
The following table presents the rollforward of the allowance for expected credit losses for available for sale securities for the six months ended June 30, 2024 and 2023:
20242023
(In thousands)Foreign GovernmentCorporateMortgage-backedAsset-backedState and MunicipalTotalForeign GovernmentCorporateMortgage-backedAsset-backedTotal
Allowance for expected credit losses, beginning of period$29,603 $5,026 $158 $1,164 $757 $36,708 $32,633 $4,701 $18 $— $37,352 
Expected credit losses on securities for which credit losses were not previously recorded300 — 1,701 — — 2,001 — 186 861 1,444 2,491 
Expected credit (gains) losses on securities for which credit losses were previously recorded(10,434)(5,026)(158)(275)(418)(16,311)419 3,987 6 — 4,412 
Reduction due to disposals— — (561)— — (561)— (7)— — (7)
Allowance for expected credit losses, end of period$19,469 $— $1,140 $889 $339 $21,837 $33,052 $8,867 $885 $1,444 $44,248 
During the six months ended June 30, 2024, the Company decreased the allowance for expected credit losses for available for sale securities utilizing its credit loss assessment process and inputs used in its credit loss model, primarily due to improved pricing associated with foreign government securities and corporate securities. During the six months ended June 30, 2023, the Company increased the allowance for expected credit losses for available for sale securities due to changes in economic assumptions utilized in its credit loss model, primarily affecting the financial services and real estate sectors.
The following table presents the rollforward of the allowance for expected credit losses for available for sale securities for the three months ended June 30, 2024 and 2023:
20242023
(In thousands)Foreign GovernmentCorporateMortgage-backedAsset-backedState and MunicipalTotalForeign GovernmentCorporateMortgage-backedAsset-backedTotal
Allowance for expected credit losses, beginning of period$20,479 $— $562 $1,097 $693 $22,831 $33,324 $3,795 $23 $— $37,142 
Expected credit losses on securities for which credit losses were not previously recorded300 — 1,139 — — 1,439 — — 861 1,444 2,305 
Expected credit (gains) losses on securities for which credit losses were previously recorded(1,310)— — (208)(354)(1,872)(272)5,074 1 — 4,803 
Reduction due to disposals— — (561)— — (561)— (2)— — (2)
Allowance for expected credit losses, end of period$19,469 $— $1,140 $889 $339 $21,837 $33,052 $8,867 $885 $1,444 $44,248 
The amortized cost and fair value of fixed maturity securities at June 30, 2024, by contractual maturity, are shown below. Actual maturities may differ from contractual maturities because certain issuers may have the right to call or prepay obligations.
(In thousands)Amortized
Cost (1)		Fair
Value
Due in one year or less$1,943,246 $1,884,790 
Due after one year through five years9,983,542 9,601,275 
Due after five years through ten years4,262,692 4,152,066 
Due after ten years2,945,631 2,850,702 
Mortgage-backed securities2,776,272 2,595,669 
Total$21,911,383 $21,084,502 
_______________
(1) Amortized cost is reduced by the allowance for expected credit losses of $34 thousand related to held to maturity securities.    
At June 30, 2024 and December 31, 2023, there were no investments that exceeded 10% of common stockholders' equity, other than investments in United States government and government agency securities.
v3.24.2.u1
Investments in Equity Securities
 6 Months Ended
Jun. 30, 2024
Debt Securities, Available-for-sale [Line Items]  
Investments in Equity Securities Investments in Fixed Maturity Securities
    At June 30, 2024 and December 31, 2023, investments in fixed maturity securities were as follows:
 
(In thousands)Amortized
Cost		Allowance for Expected Credit Losses (1)Gross UnrealizedFair
Value		Carrying
Value
GainsLosses
June 30, 2024
Held to maturity:
State and municipal$40,983 $(34)$1,766 $— $42,715 $40,949 
Residential mortgage-backed2,615 — 60 — 2,675 2,615 
Total held to maturity43,598 (34)1,826 — 45,390 43,564 
Available for sale:
U.S. government and government agency1,869,971 — 6,877 (54,472)1,822,376 1,822,376 
State and municipal:
Special revenue1,586,511 — 2,558 (80,860)1,508,209 1,508,209 
State general obligation416,788 — 1,862 (15,926)402,724 402,724 
Pre-refunded88,086 — 269 (377)87,978 87,978 
Corporate backed171,007 (339)582 (9,918)161,332 161,332 
Local general obligation390,455 — 1,254 (12,685)379,024 379,024 
Total state and municipal2,652,847 (339)6,525 (119,766)2,539,267 2,539,267 
Mortgage-backed:
Residential2,206,563 — 7,330 (178,950)2,034,943 2,034,943 
Commercial567,094 (1,140)313 (8,216)558,051 558,051 
Total mortgage-backed2,773,657 (1,140)7,643 (187,166)2,592,994 2,592,994 
Asset-backed4,071,678 (889)5,279 (61,622)4,014,446 4,014,446 
Corporate:
Industrial4,026,477 — 9,683 (142,415)3,893,745 3,893,745 
Financial3,253,805 — 7,899 (65,121)3,196,583 3,196,583 
Utilities735,920 — 1,614 (25,567)711,967 711,967 
Other616,007 — 1,247 (7,129)610,125 610,125 
Total corporate8,632,209 — 20,443 (240,232)8,412,420 8,412,420 
Foreign government1,867,457 (19,469)3,306 (193,685)1,657,609 1,657,609 
Total available for sale21,867,819 (21,837)50,073 (856,943)21,039,112 21,039,112 
Total investments in fixed maturity securities$21,911,417 $(21,871)$51,899 $(856,943)$21,084,502 $21,082,676 
____________
(1) Represents the amount of impairment that has resulted from credit-related factors. The change in the allowance for expected credit losses is recognized in the consolidated statements of income. Amount excludes unrealized losses relating to non-credit factors.
(In thousands)Amortized
Cost		Allowance for Expected Credit Losses (1)Gross UnrealizedFair
Value		Carrying
Value
GainsLosses
December 31, 2023
Held to maturity:
State and municipal$50,547 $(43)$3,132 $— $53,636 $50,504 
Residential mortgage-backed2,868 — 107 — 2,975 2,868 
Total held to maturity53,415 (43)3,239 — 56,611 53,372 
Available for sale:
U.S. government and government agency1,762,997 — 11,403 (57,669)1,716,731 1,716,731 
State and municipal:
Special revenue1,682,550 — 5,651 (82,006)1,606,195 1,606,195 
State general obligation394,429 — 3,550 (16,405)381,574 381,574 
Pre-refunded103,029 — 1,634 (185)104,478 104,478 
Corporate backed166,873 (757)696 (11,973)154,839 154,839 
Local general obligation396,041 — 3,188 (11,893)387,336 387,336 
Total state and municipal2,742,922 (757)14,719 (122,462)2,634,422 2,634,422 
Mortgage-backed:
Residential1,773,206 — 12,780 (163,844)1,622,142 1,622,142 
Commercial657,157 (158)626 (13,312)644,313 644,313 
Total mortgage-backed2,430,363 (158)13,406 (177,156)2,266,455 2,266,455 
Asset-backed4,252,883 (1,164)8,527 (73,206)4,187,040 4,187,040 
Corporate:
Industrial3,679,219 (40)24,312 (143,936)3,559,555 3,559,555 
Financial2,838,220 (4,986)14,681 (68,681)2,779,234 2,779,234 
Utilities701,865 — 6,471 (23,412)684,924 684,924 
Other635,975 — 1,605 (7,234)630,346 630,346 
Total corporate7,855,279 (5,026)47,069 (243,263)7,654,059 7,654,059 
Foreign government1,817,386 (29,603)15,865 (137,419)1,666,229 1,666,229 
Total available for sale20,861,830 (36,708)110,989 (811,175)20,124,936 20,124,936 
Total investments in fixed maturity securities$20,915,245 $(36,751)$114,228 $(811,175)$20,181,547 $20,178,308 
____________
(1) Represents the amount of impairment that has resulted from credit-related factors. The change in the allowance for expected credit losses is recognized in the consolidated statements of income. Amount excludes unrealized losses relating to non-credit factors.

The following table presents the rollforward of the allowance for expected credit losses for held to maturity securities for the six months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$43 $114 
Provision for expected credit losses(9)(61)
Allowance for expected credit losses, end of period$34 $53 

The following table presents the rollforward of the allowance for expected credit losses for held to maturity securities for the three months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$38 $107 
Provision for expected credit losses(4)(54)
Allowance for expected credit losses, end of period$34 $53 
The following table presents the rollforward of the allowance for expected credit losses for available for sale securities for the six months ended June 30, 2024 and 2023:
20242023
(In thousands)Foreign GovernmentCorporateMortgage-backedAsset-backedState and MunicipalTotalForeign GovernmentCorporateMortgage-backedAsset-backedTotal
Allowance for expected credit losses, beginning of period$29,603 $5,026 $158 $1,164 $757 $36,708 $32,633 $4,701 $18 $— $37,352 
Expected credit losses on securities for which credit losses were not previously recorded300 — 1,701 — — 2,001 — 186 861 1,444 2,491 
Expected credit (gains) losses on securities for which credit losses were previously recorded(10,434)(5,026)(158)(275)(418)(16,311)419 3,987 6 — 4,412 
Reduction due to disposals— — (561)— — (561)— (7)— — (7)
Allowance for expected credit losses, end of period$19,469 $— $1,140 $889 $339 $21,837 $33,052 $8,867 $885 $1,444 $44,248 
During the six months ended June 30, 2024, the Company decreased the allowance for expected credit losses for available for sale securities utilizing its credit loss assessment process and inputs used in its credit loss model, primarily due to improved pricing associated with foreign government securities and corporate securities. During the six months ended June 30, 2023, the Company increased the allowance for expected credit losses for available for sale securities due to changes in economic assumptions utilized in its credit loss model, primarily affecting the financial services and real estate sectors.
The following table presents the rollforward of the allowance for expected credit losses for available for sale securities for the three months ended June 30, 2024 and 2023:
20242023
(In thousands)Foreign GovernmentCorporateMortgage-backedAsset-backedState and MunicipalTotalForeign GovernmentCorporateMortgage-backedAsset-backedTotal
Allowance for expected credit losses, beginning of period$20,479 $— $562 $1,097 $693 $22,831 $33,324 $3,795 $23 $— $37,142 
Expected credit losses on securities for which credit losses were not previously recorded300 — 1,139 — — 1,439 — — 861 1,444 2,305 
Expected credit (gains) losses on securities for which credit losses were previously recorded(1,310)— — (208)(354)(1,872)(272)5,074 1 — 4,803 
Reduction due to disposals— — (561)— — (561)— (2)— — (2)
Allowance for expected credit losses, end of period$19,469 $— $1,140 $889 $339 $21,837 $33,052 $8,867 $885 $1,444 $44,248 
The amortized cost and fair value of fixed maturity securities at June 30, 2024, by contractual maturity, are shown below. Actual maturities may differ from contractual maturities because certain issuers may have the right to call or prepay obligations.
(In thousands)Amortized
Cost (1)		Fair
Value
Due in one year or less$1,943,246 $1,884,790 
Due after one year through five years9,983,542 9,601,275 
Due after five years through ten years4,262,692 4,152,066 
Due after ten years2,945,631 2,850,702 
Mortgage-backed securities2,776,272 2,595,669 
Total$21,911,383 $21,084,502 
_______________
(1) Amortized cost is reduced by the allowance for expected credit losses of $34 thousand related to held to maturity securities.    
At June 30, 2024 and December 31, 2023, there were no investments that exceeded 10% of common stockholders' equity, other than investments in United States government and government agency securities.
Equity securities  
Debt Securities, Available-for-sale [Line Items]  
Investments in Equity Securities Investments in Equity Securities
    At June 30, 2024 and December 31, 2023, investments in equity securities were as follows:
 
(In thousands)CostGross UnrealizedFair
Value		Carrying
Value
GainsLosses
June 30, 2024
Common stocks$603,574 $139,146 $(46,165)$696,555 $696,555 
Preferred stocks374,409 19,762 (12,634)381,537 381,537 
Total$977,983 $158,908 $(58,799)$1,078,092 $1,078,092 
December 31, 2023
Common stocks$664,997 $191,806 $(18,749)$838,054 $838,054 
Preferred stocks284,335 3,075 (35,117)252,293 252,293 
Total$949,332 $194,881 $(53,866)$1,090,347 $1,090,347 
v3.24.2.u1
Arbitrage Trading Account
 6 Months Ended
Jun. 30, 2024
Debt Securities, Trading, and Equity Securities, FV-NI [Abstract]  
Arbitrage Trading Account Arbitrage Trading Account
    At June 30, 2024 and December 31, 2023, the fair and carrying values of the arbitrage trading account were $1,222 million and $938 million, respectively. The primary focus of the trading account is merger arbitrage. Merger arbitrage is the business of investing in the securities of publicly held companies which are the targets in announced tender offers and mergers. Arbitrage investing differs from other types of investing in its focus on transactions and events believed likely to bring about a change in value over a relatively short time period (usually four months or less).
    The Company uses put options and call options in order to mitigate the impact of potential changes in market conditions on the merger arbitrage trading account. These options are reported at fair value. As of June 30, 2024, the fair value of long option contracts outstanding was $3 million (notional amount of $401 million) and the fair value of short option contracts was $81 million (notional amount of $401 million). Other than with respect to the use of these trading account securities, the Company does not make use of derivatives.
v3.24.2.u1
Net Investment Income
 6 Months Ended
Jun. 30, 2024
Net Investment Income [Abstract]  
Net Investment Income Net Investment Income
    Net investment income consisted of the following: 
 For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Investment income (loss) earned on:
Fixed maturity securities, including cash and cash equivalents and loans receivable$324,136 $217,830 $659,384 $413,473 
Arbitrage trading account (1)16,682 17,037 34,693 35,293 
Equity securities12,386 15,254 23,721 29,000 
Investment funds25,476 (1,186)(3,873)993 
Real estate(3,705)(2,123)(16,868)(5,834)
Gross investment income374,975 246,812 697,057 472,925 
Investment expense(2,846)(1,660)(5,090)(4,374)
Net investment income$372,129 $245,152 $691,967 $468,551 
(1) Net investment income includes earnings from trading account receivables from brokers and clearing organizations.
v3.24.2.u1
Investment Funds
 6 Months Ended
Jun. 30, 2024
Equity Method Investments and Joint Ventures [Abstract]  
Investment Funds Investment Funds
    The Company evaluates whether it is an investor in a variable interest entity ("VIE"). Such entities do not have sufficient equity at risk to finance their activities without additional subordinated financial support, or the equity investors, as a group, do not have the characteristics of a controlling financial interest (primary beneficiary). The Company determines whether it is the primary beneficiary of an entity subject to consolidation based on a qualitative assessment of the VIE's capital structure, contractual terms, nature of the VIE's operations and purpose, and the Company's relative exposure to the related risks of the VIE on the date it becomes initially involved in the VIE and on an ongoing basis. The Company is not the primary beneficiary in any of its investment funds, and accordingly, carries its interests in investment funds under the equity method of accounting.    
    The Company’s maximum exposure to loss with respect to these investments is limited to the carrying amount reported on the Company’s consolidated balance sheet and its unfunded commitments, which were $275 million as of June 30, 2024.
    Investment funds consisted of the following:
Carrying Value as of Income (Loss) from
Investment Funds
June 30,December 31,For the Six Months
Ended June 30,
(In thousands)2024202320242023
Financial services$436,057 $433,407 $(18,231)$(20,321)
Transportation306,485 344,278 (3,732)23,843 
Real Estate198,111 201,625 12,880 2,963 
Infrastructure140,699 130,589 7,828 5,936 
Energy131,719 114,794 8,505 3,439 
Other funds376,048 396,962 (11,123)(14,867)
Total$1,589,119 $1,621,655 $(3,873)$993 
    The Company's share of the earnings or losses from investment funds is generally reported on a one-quarter lag in order to facilitate the timely completion of the Company's consolidated financial statements.
Financial services investment funds include the minority investment in Lifson Re, a Bermuda reinsurance company. Effective January 1, 2021, Lifson Re participated on a fully collateralized basis in a majority of the Company’s reinsurance placements for a 22.5% share of placed amounts. The percentage increased from 22.5% to 30.0% effective July 1, 2022. This pertains to all traditional reinsurance/retrocessional placements for both property and casualty business where there is more than
one open market reinsurer participating. For the six months ended June 30, 2024 and 2023, the Company ceded approximately $206 million and $281 million, respectively, of written premiums to Lifson Re.
Other funds include deferred compensation trust assets of $41 million and $36 million as of June 30, 2024 and December 31, 2023, respectively. These assets support other liabilities reflected in the balance sheet of an equal amount for employees who have elected to defer a portion of their compensation. The change in the net asset value of the trust is recorded in other funds within net investment income with an offsetting equal amount within corporate expenses.
v3.24.2.u1
Real Estate
 6 Months Ended
Jun. 30, 2024
Real Estate [Abstract]  
Real Estate Real Estate
    Investment in real estate represents directly owned property held for investment, as follows:
Carrying Value
June 30,December 31,
(In thousands)20242023
Properties in operation$1,051,755 $1,022,654 
Properties under development227,551 227,220 
Total$1,279,306 $1,249,874 

    As of June 30, 2024, properties in operation included a long-term ground lease in Washington, D.C., an office complex in New York City and the completed portion of a mixed-use project in Washington D.C. Properties in operation are net of accumulated depreciation and amortization of $35,389,000 and $32,745,000 as of June 30, 2024 and December 31, 2023, respectively. Related depreciation expense was $4,164,000 and $4,394,000 for the six months ended June 30, 2024 and 2023, respectively. Future minimum rental income expected on operating leases relating to properties in operation is $15,013,195 in 2024, $32,278,604 in 2025, $33,991,743 in 2026, $32,850,623 in 2027, $33,376,327 in 2028, $31,999,237 in 2029 and $416,884,751 thereafter.
    A mixed-use project in Washington, D.C. had been under development in 2024 and 2023, with the completed portion reported in properties in operation as of June 30, 2024.
v3.24.2.u1
Loans Receivable
 6 Months Ended
Jun. 30, 2024
Receivables [Abstract]  
Loans Receivable Loans Receivable
At June 30, 2024 and December 31, 2023, loans receivable were as follows:
(In thousands)June 30,
2024		December 31,
2023
Amortized cost (net of allowance for expected credit losses):
Real estate loans$347,742 $200,381 
Commercial loans1,583 890 
Total$349,325 $201,271 
Fair value:
Real estate loans$347,727 $197,354 
Commercial loans1,583 890 
Total$349,310 $198,244 
The real estate loans are secured by commercial and residential real estate primarily located in the UK and New York. These loans generally earn interest at fixed or stepped interest rates and have maturities through 2026. The commercial loans are with small business owners who have secured the related financing with the assets of the business. Commercial loans primarily earn interest on a fixed basis and have varying maturities generally not exceeding 10 years.
The following table presents the rollforward of the allowance for expected credit losses for loans receivable for the six months ended June 30, 2024 and 2023:
20242023
(In thousands)Real Estate LoansCommercial LoansTotalReal Estate LoansCommercial LoansTotal
Allowance for expected credit losses, beginning of period$2,983 $21 $3,004 $1,100 $691 $1,791 
Change in expected credit losses(1,190)(1)(1,191)2,558 201 2,759 
Allowance for expected credit losses, end of period$1,793 $20 $1,813 $3,658 $892 $4,550 
During the six months ended June 30, 2024, the Company decreased the allowance for expected credit losses due to a decrease in the weighted average life of the loan portfolio. During the six months ended June 30, 2023, the Company increased the allowance for expected credit losses due to changes in economic assumptions utilized in its credit loss model.
The following table presents the rollforward of the allowance for expected credit losses for loans receivable for the three months ended June 30, 2024 and 2023:
20242023
(In thousands)Real Estate LoansCommercial LoansTotalReal Estate LoansCommercial LoansTotal
Allowance for expected credit losses, beginning of period$2,587 $22 $2,609 $1,039 $570 $1,609 
Change in expected credit losses(794)(2)(796)2,619 322 2,941 
Allowance for expected credit losses, end of period$1,793 $20 $1,813 $3,658 $892 $4,550 
The Company monitors the performance of its loans receivable and assesses the ability of the borrower to pay principal and interest based upon loan structure, underlying property values, cash flow and related financial and operating performance of the property and market conditions.
    In evaluating the real estate loans, the Company considers their credit quality indicators, including loan to value ratios, which compare the outstanding loan amount to the estimated value of the property, the borrower’s financial condition and performance with respect to loan terms, the position in the capital structure, the overall leverage in the capital structure and other market conditions.
v3.24.2.u1
Net Investment (Losses) Gains
 6 Months Ended
Jun. 30, 2024
Realized and Unrealized Investment Gains (Losses) [Abstract]  
Net Investment (Losses) Gains Net Investment (Losses) Gains
     Net investment (losses) gains were as follows:
For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Net investment (losses) gains:  
Fixed maturity securities:  
Gains$3,092 $115 $6,649 $1,058 
Losses(5,362)(3,640)(7,685)(21,770)
Equity securities (1):
Net realized gains on investment sales (2)61,521 111,072 101,798 112,132 
Change in unrealized (losses) gains(66,717)21,260 (40,905)64,664 
Investment funds217 (98)1,210 (88)
Real estate (3)(1,958)(55,449)(4,174)(44,710)
Loans receivable— — — — 
Other (4)(51,099)(4,613)(105,696)(20,028)
Net realized and unrealized (losses) gains on investments in earnings before allowance for expected credit losses(60,306)68,647 (48,803)91,258 
Change in allowance for expected credit losses on investments:
Fixed maturity securities998 (7,052)14,879 (6,835)
Loans receivable796 (2,941)1,191 (2,759)
Change in allowance for expected credit losses on investments1,794 (9,993)16,070 (9,594)
Net investment (losses) gains(58,512)58,654 (32,733)81,664 
Income tax benefit12,401 (12,587)5,769 (17,437)
After-tax net investment (losses) gains$(46,111)$46,067 $(26,964)$64,227 
Change in unrealized investment (losses) gains on available for sale securities:  
Fixed maturity securities without allowance for expected credit losses$(11,394)$(148,021)$(99,988)$79,094 
Fixed maturity securities with allowance for expected credit losses(7,683)3,694 (6,696)7,150 
Investment funds(1,338)462 (3,041)2,398 
Other(225)(178)(212)(664)
Total change in unrealized investment (losses) gains(20,640)(144,043)(109,937)87,978 
Income tax benefit (expense)7,302 30,759 26,477 (20,463)
Noncontrolling interests1 — 1 (1)
After-tax change in unrealized investment (losses) gains of available for sale securities$(13,337)$(113,284)$(83,459)$67,514 
______________________
(1) The net realized gains or losses on investment sales represent the total gains or losses from the purchase dates of the equity securities. The change in unrealized (losses) gains consists of two components: (i) the reversal of the gain or loss recognized in previous periods on equity securities sold and (ii) the change in unrealized gain or loss resulting from mark-to-market adjustments on equity securities still held.
(2) In June 2023, the Company completed a sale of the property and casualty insurance services division of Breckenridge IS, Inc. and recognized a pre-tax net realized gain on investment of $88 million on the sale (proceeds from the sale is presented on the business disposition line within the Consolidated Statements of Cash Flows).
(3) During the second quarter of 2023, the Company recognized an impairment loss of $51 million on a real estate investment.
(4) Primarily relates to realized foreign currency losses upon the disposition of fixed maturity securities.
v3.24.2.u1
Fixed Maturity Securities In An Unrealized Loss Position
 6 Months Ended
Jun. 30, 2024
Investments, Debt and Equity Securities [Abstract]  
Fixed Maturity Securities In An Unrealized Loss Position Fixed Maturity Securities in an Unrealized Loss Position
    The following tables summarize all fixed maturity securities in an unrealized loss position at June 30, 2024 and December 31, 2023 by the length of time those securities have been continuously in an unrealized loss position:
  Less Than 12 Months12 Months or GreaterTotal
(In thousands)Fair
Value		Gross
Unrealized Losses		Fair
Value		Gross
Unrealized Losses		Fair
Value		Gross
Unrealized Losses
June 30, 2024
U.S. government and government agency$422,945 $3,391 $795,297 $51,081 $1,218,242 $54,472 
State and municipal357,529 4,935 1,758,572 114,831 2,116,101 119,766 
Mortgage-backed530,802 4,258 1,356,573 182,908 1,887,375 187,166 
Asset-backed947,780 4,434 1,079,695 57,188 2,027,475 61,622 
Corporate2,068,015 17,788 4,333,968 222,444 6,401,983 240,232 
Foreign government563,150 15,565 759,174 178,120 1,322,324 193,685 
Fixed maturity securities$4,890,221 $50,371 $10,083,279 $806,572 $14,973,500 $856,943 
December 31, 2023
U.S. government and government agency$384,392 $6,655 $614,623 $51,014 $999,015 $57,669 
State and municipal264,273 3,013 1,680,034 119,449 1,944,307 122,462 
Mortgage-backed278,819 2,025 1,360,748 175,131 1,639,567 177,156 
Asset-backed413,511 2,070 2,176,035 71,136 2,589,546 73,206 
Corporate874,754 11,975 4,418,309 231,288 5,293,063 243,263 
Foreign government204,908 1,758 794,174 135,661 999,082 137,419 
Fixed maturity securities$2,420,657 $27,496 $11,043,923 $783,679 $13,464,580 $811,175 
    Substantially all of the securities in an unrealized loss position are rated investment grade, except for the securities in the foreign government classification. A significant amount of the unrealized loss on foreign government securities is the result of changes in currency exchange rates. 
    A summary of the Company’s non-investment grade fixed maturity securities that were in an unrealized loss position at June 30, 2024 is presented in the table below:
($ in thousands)Number of
Securities		Aggregate
Fair Value		Gross
Unrealized Loss
Foreign government51 $99,230 $159,930 
State and municipal5 24,865 4,838 
Corporate30 42,131 2,651 
Mortgage-backed16 4,107 201 
Total102 $170,333 $167,620 
    For fixed maturity securities that management does not intend to sell or to be required to sell, the portion of the decline in value that is considered to be due to credit factors is recognized in earnings, and the portion of the decline in value that is considered to be due to non-credit factors is recognized in other comprehensive income (loss).
     The Company has evaluated its fixed maturity securities in an unrealized loss position and believes the unrealized losses are due primarily to temporary market and sector-related factors rather than to issuer-specific factors. None of these securities are delinquent or in default under financial covenants. Based on its assessment of these issuers, the Company expects them to continue to meet their contractual payment obligations as they become due.
v3.24.2.u1
Fair Value Measurements
 6 Months Ended
Jun. 30, 2024
Fair Value Disclosures [Abstract]  
Fair Value Measurements Fair Value Measurements
    The Company’s fixed maturity available for sale securities, equity securities and its arbitrage trading account securities are carried at fair value. Fair value is defined as “the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.” The Company utilizes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three broad levels, as follows:
Level 1 - Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.
Level 2 - Quoted prices for similar assets or valuations based on inputs that are observable.
Level 3 - Estimates of fair value based on internal pricing methodologies using unobservable inputs. Unobservable inputs are only used to measure fair value to the extent that observable inputs are not available.
    Substantially all of the Company’s fixed maturity securities were priced by independent pricing services. The prices provided by the independent pricing services are estimated based on observable market data in active markets utilizing pricing models and processes, which may include benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, sector groupings, matrix pricing and reference data. The pricing services may prioritize inputs differently on any given day for any security based on market conditions, and not all inputs are available for each security evaluation on any given day. The pricing services used by the Company have indicated that they will only produce an estimate of fair value if objectively verifiable information is available. The determination of whether markets are active or inactive is based upon the volume and level of activity for a particular asset class. The Company reviews the prices provided by pricing services for reasonableness and periodically performs independent price tests of a sample of securities to ensure proper valuation.
    If prices from independent pricing services are not available for fixed maturity securities, the Company estimates the fair value. For Level 2 securities, the Company utilizes pricing models and processes which may include benchmark yields, sector groupings, matrix pricing, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, bids, offers and reference data. Where broker quotes are used, the Company generally requests two or more quotes and sets a price within the range of quotes received based on its assessment of the credibility of the quote and its own evaluation of the security. The Company generally does not adjust quotes received from brokers. For securities traded only in private negotiations, the Company determines fair value based primarily on the cost of such securities, which is adjusted to reflect prices of recent placements of securities of the same issuer, financial projections, credit quality and business developments of the issuer and other relevant information.
    For Level 3 securities, the Company generally uses a discounted cash flow model to estimate the fair value of fixed maturity securities. The cash flow models are based upon assumptions as to prevailing credit spreads, interest rate and interest rate volatility, time to maturity and subordination levels. Projected cash flows are discounted at rates that are adjusted to reflect illiquidity, where appropriate.
    
    The following tables present the assets and liabilities measured at fair value on a recurring basis as of June 30, 2024 and December 31, 2023 by level:
(In thousands)TotalLevel 1Level 2Level 3
June 30, 2024
Assets:
Fixed maturity securities available for sale:
U.S. government and government agency$1,822,376 $— $1,822,376 $— 
State and municipal2,539,267 — 2,539,267 — 
Mortgage-backed2,592,994 — 2,592,994 — 
Asset-backed4,014,446 — 4,014,446 — 
Corporate8,412,420 — 8,412,420 — 
Foreign government1,657,609 — 1,657,609 — 
Total fixed maturity securities available for sale21,039,112 — 21,039,112 — 
Equity securities:
Common stocks696,555 693,294 1,116 2,145 
Preferred stocks381,537 — 377,901 3,636 
Total equity securities1,078,092 693,294 379,017 5,781 
Arbitrage trading account1,221,861 1,061,891 156,377 3,593 
Total$23,339,065 $1,755,185 $21,574,506 $9,374 
Liabilities:
Trading account securities sold but not yet purchased$81,273 $81,273 $— $— 
December 31, 2023
Assets:
Fixed maturity securities available for sale:
U.S. government and government agency$1,716,731 $— $1,716,731 $— 
State and municipal2,634,422 — 2,634,422 — 
Mortgage-backed2,266,455 — 2,266,455 — 
Asset-backed4,187,040 — 4,187,040 — 
Corporate7,654,059 — 7,654,059 — 
Foreign government1,666,229 — 1,666,229 — 
Total fixed maturity securities available for sale20,124,936 — 20,124,936 — 
Equity securities:
Common stocks838,054 835,338 1,158 1,558 
Preferred stocks252,293 — 248,598 3,695 
Total equity securities1,090,347 835,338 249,756 5,253 
Arbitrage trading account938,049 546,110 388,167 3,772 
Total$22,153,332 $1,381,448 $20,762,859 $9,025 
Liabilities:
Trading account securities sold but not yet purchased$9,357 $9,357 $— $— 
    The following tables summarize changes in Level 3 assets and liabilities for the six months ended June 30, 2024 and for the year ended December 31, 2023:
Gains (Losses) Included In:
(In thousands)Beginning
Balance		Earnings (Losses)Other
Comprehensive
Income (Losses)		ImpairmentsPurchasesSalesPaydowns / MaturitiesTransfers In / (Out)Ending
Balance
Six Months Ended June 30, 2024
Assets:
Equity securities:
Common stocks$1,558 $715 $— $— $— $(128)$— $— $2,145 
Preferred stocks3,695 (2)— — — (57)— — 3,636 
Total5,253 713 — — — (185)— — 5,781 
Arbitrage trading account3,772 (178)— — — (38)— 37 3,593 
Total$9,025 $535 $— $— $— $(223)$— $37 $9,374 
Year Ended
December 31, 2023
Assets:
Equity securities:
Common stocks$2,599 $(1,041)$— $— $— $— $— $— $1,558 
Preferred stocks11,299 (3)— (7,601)— — — — 3,695 
Total13,898 (1,044)— (7,601)— — — — 5,253 
Arbitrage trading account3,590 117 — — — — — 65 3,772 
Total$17,488 $(927)$— $(7,601)$— $— $— $65 $9,025 
    For both the six months ended June 30, 2024 and the year ended December 31, 2023, one security within the arbitrage trading account portfolio that no longer had a publicly traded price was transferred into Level 3.
Fair Value of Financial Instruments
    The following table presents the carrying amounts and estimated fair values of the Company’s financial instruments:
  June 30, 2024December 31, 2023
(In thousands)Carrying ValueFair ValueCarrying ValueFair Value
Assets:
Fixed maturity securities$21,082,676 $21,084,502 $20,178,308 $20,181,547 
Equity securities1,078,092 1,078,092 1,090,347 1,090,347 
Arbitrage trading account1,221,861 1,221,861 938,049 938,049 
Loans receivable349,325 349,310 201,271 198,244 
Cash and cash equivalents1,580,270 1,580,270 1,363,195 1,363,195 
Trading account receivables from brokers and clearing organizations40,705 40,705 303,614 303,614 
     Due from broker— — 36,747 36,747 
Liabilities:
Due to broker128,563 128,563 — — 
Trading account securities sold but not yet purchased81,273 81,273 9,357 9,357 
Senior notes and other debt1,828,422 1,422,506 1,827,951 1,480,076 
Subordinated debentures1,009,449 825,344 1,009,090 929,598 
    The estimated fair values of the Company’s fixed maturity securities, equity securities and arbitrage trading account securities are based on various valuation techniques that rely on fair value measurements as described in Note 15. The fair value of loans receivable are estimated by using current institutional purchaser yield requirements for loans with similar credit characteristics, which is considered a Level 2 input. The fair value of the senior notes and other debt and the subordinated debentures is based on spreads for similar securities, which is considered a Level 2 input.
v3.24.2.u1
Reserves for Loss and Loss Expenses
 6 Months Ended
Jun. 30, 2024
Insurance [Abstract]  
Reserves for Loss and Loss Expenses Reserves for Loss and Loss Expenses
    The Company's reserves for losses and loss expenses are comprised of case reserves and incurred but not reported liabilities ("IBNR"). When a claim is reported, a case reserve is established for the estimated ultimate payment based upon known information about the claim. As more information about the claim becomes available over time, case reserves are adjusted up or down as appropriate. Reserves are also established on an aggregate basis to provide for IBNR liabilities and expected loss reserve development on reported claims.
    Loss reserves included in the Company’s financial statements represent management’s best estimates based upon an actuarially derived point estimate and other considerations. The Company uses a variety of actuarial techniques and methods to derive an actuarial point estimate for each operating unit. These methods include paid loss development, incurred loss development, paid and incurred Bornhuetter-Ferguson methods and frequency and severity methods. In circumstances where one actuarial method is considered more credible than the others, that method is used to set the point estimate. The actuarial point estimate may also be based on a judgmental weighting of estimates produced from each of the methods considered. Industry loss experience is used to supplement the Company’s own data in selecting “tail factors” in areas where the Company’s own data is limited. The actuarial data is analyzed by line of business, coverage and accident or policy year, as appropriate, for each operating unit.
    The establishment of the actuarially derived loss reserve point estimate also includes consideration of qualitative factors that may affect the ultimate losses. These qualitative considerations include, among others, the impact of re-underwriting initiatives, changes in the mix of business, changes in distribution sources and changes in policy terms and conditions.
    The key assumptions used to arrive at the best estimate of loss reserves are the expected loss ratios, rate of loss cost inflation, and reported and paid loss emergence patterns. Expected loss ratios represent management’s expectation of losses at the time the business is priced and written, before any actual claims experience has emerged. This expectation is a significant determinant of the estimate of loss reserves for recently written business where there is little paid or incurred loss data to consider. Expected loss ratios are generally derived from historical loss ratios adjusted for the impact of rate changes, loss cost trends and known changes in the type of risks underwritten. Expected loss ratios are estimated for each key line of business within each operating unit. Expected loss cost inflation is particularly important for the long-tail lines, such as excess casualty, and claims with a high medical component, such as workers’ compensation. Reported and paid loss emergence patterns are used to project current reported or paid loss amounts to their ultimate settlement value. Loss development factors are based on the historical emergence patterns of paid and incurred losses, and are derived from the Company’s own experience and industry data. The paid loss emergence pattern is also significant to excess and assumed workers’ compensation reserves because those reserves are discounted to their estimated present value based upon such estimated payout patterns.
    Loss frequency and severity are measures of loss activity that are considered in determining the key assumptions described in our discussion of loss and loss expense reserves, including expected loss ratios, rate of loss cost inflation and reported and paid loss emergence patterns. Loss frequency is a measure of the number of claims per unit of insured exposure, and loss severity is a measure of the average size of claims. Factors affecting loss frequency include the effectiveness of loss controls and safety programs and changes in economic activity or weather patterns. Factors affecting loss severity include changes in policy limits, retentions, rate of inflation and judicial interpretations.
    Another factor affecting estimates of loss frequency and severity is the loss reporting lag, which is the period of time between the occurrence of a loss and the date the loss is reported to the Company. The length of the loss reporting lag affects our ability to accurately predict loss frequency (loss frequencies are more predictable for lines with short reporting lags) as well as the amount of reserves needed for incurred but not reported losses (less IBNR is required for lines with short reporting lags). As a result, loss reserves for lines with short reporting lags are likely to have less variation from initial loss estimates. For lines with short reporting lags, which include auto, primary workers’ compensation, other liability (claims-made) and property business, the key assumption is the loss emergence pattern used to project ultimate loss estimates from known losses paid or reported to date. For lines of business with long reporting lags, which include other liability (occurrence), products liability, excess workers’ compensation and liability reinsurance, the key assumption is the expected loss ratio since there is often little paid or incurred loss data to consider. Historically, the Company has experienced less variation from its initial loss estimates for lines of business with short reporting lags than for lines of business with long reporting lags.
    The key assumptions used in calculating the most recent estimate of the loss reserves are reviewed each quarter and adjusted, to the extent necessary, to reflect the latest reported loss data, current trends and other factors observed.
    The table below provides a reconciliation of the beginning and ending reserve balances:
June 30,
(In thousands)20242023
Net reserves at beginning of period$15,661,820 $14,248,879 
Net provision for losses and loss expenses:
Claims occurring during the current year (1)3,411,888 3,064,046 
Increase in estimates for claims occurring in prior years (2) (3)14,700 28,853 
Loss reserve discount accretion 17,786 15,510 
Total3,444,374 3,108,409 
Net payments for claims:  
Current year383,639 375,365 
Prior years2,205,566 2,019,371 
Total2,589,205 2,394,736 
Foreign currency translation(56,143)5,929 
Net reserves at end of period16,460,846 14,968,481 
Ceded reserves at end of period3,106,344 2,951,515 
Gross reserves at end of period$19,567,190 $17,919,996 
_______________________________________
(1) Claims occurring during the current year are net of loss reserve discounts of $26 million and $22 million for the six months ended June 30, 2024 and 2023, respectively.
(2) The change in estimates for claims occurring in prior years is net of loss reserve discount. On an undiscounted basis, the estimates for claims occurring in prior years increased by $7 million and decreased by $6 million for the six months ended June 30, 2024 and 2023, respectively.
(3) For certain retrospectively rated insurance policies and reinsurance agreements, reserve development is offset by additional or return premiums. Favorable development, net of additional and return premiums, was $2 million and adverse development was $21 million for the six months ended June 30, 2024 and 2023, respectively.
The ultimate net impact of COVID-19 on the Company’s reserves remains uncertain. As of June 30, 2024, the Company had recognized losses for COVID-19-related claims activity, net of reinsurance, of approximately $388 million, of which $329 million relates to the Insurance segment and $59 million relates to the Reinsurance & Monoline Excess segment. Such $388 million of COVID-19-related losses included $385 million of reported losses and $3 million of IBNR.
During the six months ended June 30, 2024, favorable prior year development (net of additional and return premiums) of $2 million included $7 million for the Reinsurance & Monoline Excess segment partially offset by $5 million of adverse prior year development for the Insurance segment.
For the Insurance segment, the adverse development during the first half of 2024 was driven by commercial auto liability and other liability (mainly umbrella and excess liability), and was partially offset by favorable development for workers’ compensation and professional liability. The adverse commercial auto liability development was concentrated in accident years 2020 through 2023. The other liability development was mainly driven by umbrella and excess liability claims, and was focused in accident years 2017 through 2021. A significant portion of the umbrella and excess liability development related to underlying commercial auto exposures. The Company believes that commercial auto-related claims are being particularly impacted by social inflation, which is contributing to an increase in the frequency of large losses beyond expectations. Social inflation can include higher settlement demands from plaintiffs, use of aggressive actions by the plaintiffs’ bar such as litigation funding, negative public sentiment towards large businesses and corporations, and erosion of tort reforms, among other factors.
The favorable workers’ compensation development for the Insurance segment was mainly related to accident years 2016 through 2023, while the favorable professional liability development was mainly in accident years 2018 through 2022. For workers’ compensation, favorable reported claim frequency, below expectations, continued to be the main driver of the favorable reserve development. For professional liability, reported loss experience for accident years 2018 through 2022 was better than expected, which drove the favorable reserve development. Accident years 2020 through 2022 also feature business written at peak pricing levels, which the Company now believes will result in higher profitability than initially anticipated.
For the Reinsurance & Monoline Excess segment, the favorable development during the first half of 2024 was driven mainly by favorable development in excess workers’ compensation, partially offset by adverse development in the non-proportional reinsurance assumed liability line of business. The favorable excess workers’ compensation development was driven by continued lower claim frequency and reported losses relative to expectations, and to favorable claim settlements
spread across many prior accident years. The unfavorable development for non-proportional reinsurance was concentrated mainly in accident years 2017 through 2019 and was associated primarily with our U.S. and U.K. excess general liability reinsurance businesses, including coverage for cedants insuring construction projects.
During the six months ended June 30, 2023, adverse prior year development (net of additional and return premiums) of $21 million included $19 million for the Insurance segment and $2 million for the Reinsurance & Monoline Excess segment.
Overall adverse development was recognized during the first quarter of 2023 in both business segments due to property catastrophe losses related to 2022 events that were still being adjusted and settled. In particular, losses related to U.S. winter storms that occurred in December were a significant driver of the development, as information gathering and evaluation of these losses were still ongoing into the first quarter. As a result, prior year reserve development (net of additional and return premiums) overall was adverse by $24 million in the first quarter, but was favorable by $3 million during the second quarter of 2023.
For the Insurance segment, in addition to the property prior year adverse development discussed above, the adverse development during the six months ended June 30, 2023 included adverse prior year development on casualty lines for the 2016 through 2019 accident years, which was largely offset by favorable prior year development on casualty lines for the 2021 and 2022 accident years. The adverse development on the 2016 through 2019 accident years was concentrated in the other liability line of business, and to a lesser degree, professional liability, including medical professional. The development, which particularly impacted business attaching excess of primary policy limits, was driven by a larger than expected number of large losses reported. The Company believes social inflation is contributing to an increase in the frequency of large losses for these accident years. Social inflation can include higher settlement demands from plaintiffs, use of tactics such as litigation funding by the plaintiffs’ bar, negative public sentiment towards large businesses and corporations, and erosion of tort reforms, among others.
The favorable prior year development on casualty lines for the 2021 and 2022 accident years in the Insurance segment was concentrated in the professional liability, workers’ compensation, and other liability lines of business, partially offset by adverse development in commercial auto liability. Due to uncertainty regarding incurred loss frequency and severity in light of ongoing social inflation and the impacts of the COVID-19 pandemic, the Company set its initial loss ratios for the 2021 and 2022 accident years prudently, and largely maintained these estimates through the end of each respective accident year. The reported loss experience for these lines of business for the 2021 and 2022 accident years has been better than was expected, and the Company has begun to react to this favorable emergence as the accident years mature beyond 12 months. Commercial auto liability experienced adverse prior year development during the six months ended June 30, 2023 for the 2021 accident year, which was driven by a larger than expected number of large losses reported.
For the Reinsurance & Monoline Excess segment, the adverse development during the six months ended June 30, 2023 was driven mainly by adverse development in property (discussed above) and non-proportional reinsurance assumed liability lines of business, largely offset by favorable development in excess workers' compensation. The favorable excess workers’ compensation development was driven by continued lower claim frequency and reported losses relative to our expectations, and to favorable claim settlements. The favorable development was spread across many prior accident years. The adverse development on reinsurance assumed liability was associated primarily with our U.S. assumed reinsurance business, and related to accounts reinsuring excess and umbrella business and construction projects. The adverse development was concentrated mainly in accident years 2017 through 2020.
v3.24.2.u1
Fair Value Of Financial Instruments
 6 Months Ended
Jun. 30, 2024
Fair Value Disclosures [Abstract]  
Fair Value Of Financial Instruments Fair Value Measurements
    The Company’s fixed maturity available for sale securities, equity securities and its arbitrage trading account securities are carried at fair value. Fair value is defined as “the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.” The Company utilizes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three broad levels, as follows:
Level 1 - Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.
Level 2 - Quoted prices for similar assets or valuations based on inputs that are observable.
Level 3 - Estimates of fair value based on internal pricing methodologies using unobservable inputs. Unobservable inputs are only used to measure fair value to the extent that observable inputs are not available.
    Substantially all of the Company’s fixed maturity securities were priced by independent pricing services. The prices provided by the independent pricing services are estimated based on observable market data in active markets utilizing pricing models and processes, which may include benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, sector groupings, matrix pricing and reference data. The pricing services may prioritize inputs differently on any given day for any security based on market conditions, and not all inputs are available for each security evaluation on any given day. The pricing services used by the Company have indicated that they will only produce an estimate of fair value if objectively verifiable information is available. The determination of whether markets are active or inactive is based upon the volume and level of activity for a particular asset class. The Company reviews the prices provided by pricing services for reasonableness and periodically performs independent price tests of a sample of securities to ensure proper valuation.
    If prices from independent pricing services are not available for fixed maturity securities, the Company estimates the fair value. For Level 2 securities, the Company utilizes pricing models and processes which may include benchmark yields, sector groupings, matrix pricing, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, bids, offers and reference data. Where broker quotes are used, the Company generally requests two or more quotes and sets a price within the range of quotes received based on its assessment of the credibility of the quote and its own evaluation of the security. The Company generally does not adjust quotes received from brokers. For securities traded only in private negotiations, the Company determines fair value based primarily on the cost of such securities, which is adjusted to reflect prices of recent placements of securities of the same issuer, financial projections, credit quality and business developments of the issuer and other relevant information.
    For Level 3 securities, the Company generally uses a discounted cash flow model to estimate the fair value of fixed maturity securities. The cash flow models are based upon assumptions as to prevailing credit spreads, interest rate and interest rate volatility, time to maturity and subordination levels. Projected cash flows are discounted at rates that are adjusted to reflect illiquidity, where appropriate.
    
    The following tables present the assets and liabilities measured at fair value on a recurring basis as of June 30, 2024 and December 31, 2023 by level:
(In thousands)TotalLevel 1Level 2Level 3
June 30, 2024
Assets:
Fixed maturity securities available for sale:
U.S. government and government agency$1,822,376 $— $1,822,376 $— 
State and municipal2,539,267 — 2,539,267 — 
Mortgage-backed2,592,994 — 2,592,994 — 
Asset-backed4,014,446 — 4,014,446 — 
Corporate8,412,420 — 8,412,420 — 
Foreign government1,657,609 — 1,657,609 — 
Total fixed maturity securities available for sale21,039,112 — 21,039,112 — 
Equity securities:
Common stocks696,555 693,294 1,116 2,145 
Preferred stocks381,537 — 377,901 3,636 
Total equity securities1,078,092 693,294 379,017 5,781 
Arbitrage trading account1,221,861 1,061,891 156,377 3,593 
Total$23,339,065 $1,755,185 $21,574,506 $9,374 
Liabilities:
Trading account securities sold but not yet purchased$81,273 $81,273 $— $— 
December 31, 2023
Assets:
Fixed maturity securities available for sale:
U.S. government and government agency$1,716,731 $— $1,716,731 $— 
State and municipal2,634,422 — 2,634,422 — 
Mortgage-backed2,266,455 — 2,266,455 — 
Asset-backed4,187,040 — 4,187,040 — 
Corporate7,654,059 — 7,654,059 — 
Foreign government1,666,229 — 1,666,229 — 
Total fixed maturity securities available for sale20,124,936 — 20,124,936 — 
Equity securities:
Common stocks838,054 835,338 1,158 1,558 
Preferred stocks252,293 — 248,598 3,695 
Total equity securities1,090,347 835,338 249,756 5,253 
Arbitrage trading account938,049 546,110 388,167 3,772 
Total$22,153,332 $1,381,448 $20,762,859 $9,025 
Liabilities:
Trading account securities sold but not yet purchased$9,357 $9,357 $— $— 
    The following tables summarize changes in Level 3 assets and liabilities for the six months ended June 30, 2024 and for the year ended December 31, 2023:
Gains (Losses) Included In:
(In thousands)Beginning
Balance		Earnings (Losses)Other
Comprehensive
Income (Losses)		ImpairmentsPurchasesSalesPaydowns / MaturitiesTransfers In / (Out)Ending
Balance
Six Months Ended June 30, 2024
Assets:
Equity securities:
Common stocks$1,558 $715 $— $— $— $(128)$— $— $2,145 
Preferred stocks3,695 (2)— — — (57)— — 3,636 
Total5,253 713 — — — (185)— — 5,781 
Arbitrage trading account3,772 (178)— — — (38)— 37 3,593 
Total$9,025 $535 $— $— $— $(223)$— $37 $9,374 
Year Ended
December 31, 2023
Assets:
Equity securities:
Common stocks$2,599 $(1,041)$— $— $— $— $— $— $1,558 
Preferred stocks11,299 (3)— (7,601)— — — — 3,695 
Total13,898 (1,044)— (7,601)— — — — 5,253 
Arbitrage trading account3,590 117 — — — — — 65 3,772 
Total$17,488 $(927)$— $(7,601)$— $— $— $65 $9,025 
    For both the six months ended June 30, 2024 and the year ended December 31, 2023, one security within the arbitrage trading account portfolio that no longer had a publicly traded price was transferred into Level 3.
Fair Value of Financial Instruments
    The following table presents the carrying amounts and estimated fair values of the Company’s financial instruments:
  June 30, 2024December 31, 2023
(In thousands)Carrying ValueFair ValueCarrying ValueFair Value
Assets:
Fixed maturity securities$21,082,676 $21,084,502 $20,178,308 $20,181,547 
Equity securities1,078,092 1,078,092 1,090,347 1,090,347 
Arbitrage trading account1,221,861 1,221,861 938,049 938,049 
Loans receivable349,325 349,310 201,271 198,244 
Cash and cash equivalents1,580,270 1,580,270 1,363,195 1,363,195 
Trading account receivables from brokers and clearing organizations40,705 40,705 303,614 303,614 
     Due from broker— — 36,747 36,747 
Liabilities:
Due to broker128,563 128,563 — — 
Trading account securities sold but not yet purchased81,273 81,273 9,357 9,357 
Senior notes and other debt1,828,422 1,422,506 1,827,951 1,480,076 
Subordinated debentures1,009,449 825,344 1,009,090 929,598 
    The estimated fair values of the Company’s fixed maturity securities, equity securities and arbitrage trading account securities are based on various valuation techniques that rely on fair value measurements as described in Note 15. The fair value of loans receivable are estimated by using current institutional purchaser yield requirements for loans with similar credit characteristics, which is considered a Level 2 input. The fair value of the senior notes and other debt and the subordinated debentures is based on spreads for similar securities, which is considered a Level 2 input.
v3.24.2.u1
Premiums and Reinsurance Related Information
 6 Months Ended
Jun. 30, 2024
Insurance [Abstract]  
Premiums and Reinsurance Related Information Premiums and Reinsurance Related Information
The following is a summary of insurance and reinsurance financial information:
For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Written premiums:
Direct$3,380,470 $2,985,563 $6,419,537 $5,724,317 
Assumed337,302 351,210 660,991 661,773 
Ceded(590,993)(525,258)(1,102,458)(999,751)
Total net premiums written$3,126,779 $2,811,515 $5,978,070 $5,386,339 
Earned premiums:
Direct$3,048,872 $2,725,650 $5,985,516 $5,392,712 
Assumed328,114 302,431 666,024 597,661 
Ceded(530,571)(475,354)(1,040,778)(946,214)
Total net premiums earned$2,846,415 $2,552,727 $5,610,762 $5,044,159 
Ceded losses and loss expenses incurred$327,243 $333,795 $633,194 $649,271 
Ceded commissions earned$123,647 $117,523 $244,701 $235,941 
    The following table presents the rollforward of the allowance for expected credit losses for premiums and fees receivable for the six months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$35,110 $30,660 
Change in expected credit losses2,169 2,110 
Allowance for expected credit losses, end of period$37,279 $32,770 
The following table presents the rollforward of the allowance for expected credit losses for premiums and fees receivable for the three months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$35,039 $32,353 
Change in expected credit losses2,240 417 
Allowance for expected credit losses, end of period$37,279 $32,770 
The Company reinsures a portion of its insurance exposures in order to reduce its net liability on individual risks and catastrophe losses. The Company also cedes premiums to state assigned risk plans and captive insurance companies. Estimated amounts due from reinsurers are reported net of an allowance for expected credit losses.
The following table presents the rollforward of the allowance for expected credit losses associated with due from reinsurers for the six months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$8,404 $8,064 
Change in expected credit losses1,851 1,301 
Allowance for expected credit losses, end of period$10,255 $9,365 
The following table presents the rollforward of the allowance for expected credit losses associated with due from reinsurers for the three months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$9,185 $8,703 
Change in expected credit losses1,070 662 
Allowance for expected credit losses, end of period$10,255 $9,365 
v3.24.2.u1
Restricted Stock Units
 6 Months Ended
Jun. 30, 2024
Share-Based Payment Arrangement [Abstract]  
Restricted Stock Units Restricted Stock Units
    Pursuant to its stock incentive plan, the Company may issue restricted stock units ("RSUs") to employees of the Company and its subsidiaries. The RSUs generally vest three to five years from the award date and are subject to other vesting and forfeiture provisions contained in the award agreement. RSUs are expensed pro-ratably over the vesting period. RSU expenses were $25 million and $23 million for the six months ended June 30, 2024 and 2023, respectively. A summary of RSUs issued in the six months ended June 30, 2024 and 2023 follows:
($ in thousands)
UnitsFair Value
20242,277 $125 
20238,381 $332 
v3.24.2.u1
Litigation and Contingent Liabilities
 6 Months Ended
Jun. 30, 2024
Commitments and Contingencies Disclosure [Abstract]  
Litigation and Contingent Liabilities Litigation and Contingent Liabilities
    In the ordinary course of business, the Company is subject to disputes, litigation and arbitration arising from its insurance and reinsurance businesses. These matters are generally related to insurance and reinsurance claims and are considered in the establishment of loss and loss expense reserves. In addition, the Company may also become involved in legal actions which seek extra-contractual damages, punitive damages or penalties, including claims alleging bad faith in handling of insurance claims. The Company expects its ultimate liability with respect to such matters will not be material to its financial condition. However, adverse outcomes on such matters are possible, from time to time, and could be material to the Company’s results of operations in any particular financial reporting period.
On December 22, 2023, one of the Company’s subsidiaries filed a lawsuit against certain reinsurers to recover in excess of $90 million in respect of certain losses paid to its policyholders under certain event cancellation and related insurance policies. The Company believes its claims against the reinsurers are meritorious and expects a positive resolution to its lawsuit. While an adverse outcome is possible, the Company believes that the outcome, in any case, will not be material to the Company’s financial condition.
v3.24.2.u1
Leases
 6 Months Ended
Jun. 30, 2024
Leases [Abstract]  
Leases Leases
    Lessees are required to recognize a right-of-use asset and a lease liability for leases with terms of more than 12 months on the balance sheet. All leases disclosed within this footnote are classified as operating leases. Recognized right-of-use asset and lease liability are reported within other assets and other liabilities, respectively, in the consolidated balance sheet. Lease expense is reported in other operating costs and expenses in the consolidated statement of income and accounted for on a straight-line basis over the lease term.
    To determine the discount rate used to calculate present value of future minimum lease payments, the Company uses its incremental borrowing rate during the lease commencement period in line with the respective lease duration. In certain cases, the Company has the option to renew the lease. Lease renewal future payments are included in the present value of the future minimum lease payments when the Company determines it is reasonably certain to renew.
The main leases entered into by the Company are for office space used by the Company’s operating units across the world. Additionally, the Company, to a lesser extent, has equipment leases mainly for office equipment. Further information relating to operating lease expense and other operating lease information are as follows:
 For the Three Months Ended
June 30,		For the Six Months Ended June 30,
(In thousands)2024202320242023
Leases:
Lease cost$11,326 $10,138 $22,403 $20,326 
Cash paid for amounts included in the measurement of lease liabilities reported in operating cash flows$12,364 $11,281 $24,596 $21,844 
Right-of-use assets obtained in exchange for new lease liabilities$8,853 $2,633 $33,548 $7,946 

As of June 30,
($ in thousands)20242023
Right-of-use assets$190,207$157,991
Lease liabilities$231,128$191,576
Weighted-average remaining lease term7.5 years7.0 years
Weighted-average discount rate5.51 %4.49 %
Contractual maturities of the Company’s future minimum lease payments are as follows:
(In thousands)June 30, 2024
Contractual Maturities:
2024$26,008 
202545,629 
202639,117 
202730,117 
202828,576 
Thereafter107,255 
Total undiscounted future minimum lease payments276,702 
Less: Discount impact45,574 
Total lease liability$231,128 
v3.24.2.u1
Business Segments
 6 Months Ended
Jun. 30, 2024
Segment Reporting [Abstract]  
Business Segments Business Segments
    The Company’s reportable segments include the following two business segments, plus a corporate segment:
•Insurance - predominantly commercial insurance business, including excess and surplus lines, admitted lines and specialty personal lines throughout the United States, as well as insurance business in Asia, Australia, Canada, Continental Europe, Mexico, Scandinavia, South America and the United Kingdom.
•Reinsurance & Monoline Excess - reinsurance business on a facultative and treaty basis, primarily in the United States, the United Kingdom, Continental Europe, Australia, the Asia-Pacific Region and South Africa, as well as operations that solely retain risk on an excess basis and certain program management business.
    The accounting policies of the segments are the same as those described in the summary of significant accounting policies. Income tax expense and benefits are calculated based upon the Company's overall effective tax rate.
    Summary financial information about the Company's reporting segments is presented in the following tables. Income (loss) before income taxes by segment includes allocated investment income. Identifiable assets by segment are those assets used in or allocated to the operation of each segment.
  Revenues  
(In thousands)Earned
Premiums (1)		Investment
Income 		OtherTotal (2)Pre-Tax Income (Loss)Net Income (Loss) to Common Stockholders
Three months ended June 30, 2024
Insurance$2,484,569 $303,561 $9,591 $2,797,721 $490,053 $374,247 
Reinsurance & Monoline Excess361,846 58,472 — 420,318 124,449 97,638 
Corporate, other and eliminations (3)— 10,096 144,409 154,505 (68,317)(53,865)
Net investment losses— — (58,512)(58,512)(58,512)(46,111)
Total$2,846,415 $372,129 $95,488 $3,314,032 $487,673 $371,909 
Three months ended June 30, 2023
Insurance$2,215,186 $185,327 $8,853 $2,409,366 $386,350 $300,239 
Reinsurance & Monoline Excess337,541 42,187 — 379,728 105,420 82,317 
Corporate, other and eliminations (3)— 17,638 130,528 148,166 (93,240)(72,315)
Net investment gains— — 58,654 58,654 58,654 46,067 
Total$2,552,727 $245,152 $198,035 $2,995,914 $457,184 $356,308 
Six months ended June 30, 2024
Insurance$4,883,338 $548,338 $19,014 $5,450,690 $968,202 $739,337 
Reinsurance & Monoline Excess727,424 111,683 — 839,107 252,074 199,764 
Corporate, other and eliminations (3)— 31,946 281,795 313,741 (125,799)(97,757)
Net investment losses— — (32,733)(32,733)(32,733)(26,964)
Total$5,610,762 $691,967 $268,076 $6,570,805 $1,061,744 $814,380 
Six Months Ended June 30, 2023
Insurance$4,358,110 $348,886 $18,427 $4,725,423 $738,977 $574,347 
Reinsurance & Monoline Excess686,049 96,770 — 782,819 206,704 164,674 
Corporate, other and eliminations (3)— 22,895 278,117 301,012 (194,089)(152,814)
Net investment gains— — 81,664 81,664 81,664 64,227 
Total$5,044,159 $468,551 $378,208 $5,890,918 $833,256 $650,434 
_________________
(1) Certain amounts included in earned premiums of each segment are related to inter-segment transactions.
(2) Revenues for Insurance from foreign operations for the three months ended June 30, 2024 and 2023 were $368 million and $280 million, respectively, and for the six months ended June 30, 2024 and 2023 were $762 million and $554 million, respectively. Revenues for Reinsurance & Monoline Excess from foreign operations for the three months ended June 30, 2024 and 2023 were $117 million and $102 million, respectively, and for the six months ended June 30, 2024 and 2023 were $228 million and $209 million, respectively.
(3) Corporate, other and eliminations represent corporate revenues and expenses that are not allocated to business segments.

Identifiable Assets
(In thousands)June 30,
2024		December 31,
2023
Insurance$31,264,338 $29,923,282 
Reinsurance & Monoline Excess5,557,232 5,545,249 
Corporate, other and eliminations2,088,349 1,643,299 
Consolidated$38,909,919 $37,111,830 


    Net premiums earned by major line of business are as follows:
 For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Insurance:
Other liability$1,001,987 $890,984 $1,969,247 $1,744,456 
Short-tail lines (1)538,797 444,834 1,049,606 857,368 
Auto361,580 307,578 715,593 601,694 
Workers' compensation310,564 299,149 612,060 604,710 
Professional liability271,641 272,641 536,832 549,882 
Total Insurance2,484,569 2,215,186 4,883,338 4,358,110 
Reinsurance & Monoline Excess:
Casualty (2)199,080 202,348 396,924 417,060 
Property (2)97,255 76,348 199,638 151,500 
Monoline excess (3)65,511 58,845 130,862 117,489 
Total Reinsurance & Monoline Excess361,846 337,541 727,424 686,049 
Total$2,846,415 $2,552,727 $5,610,762 $5,044,159 
______________
(1) Short-tail lines include commercial multi-peril (non-liability), inland marine, accident and health, fidelity and surety, boiler and machinery, high net worth homeowners and other lines.
(2) Includes reinsurance casualty and property and certain program management business.
(3) Monoline excess includes operations that solely retain risk on an excess basis.
v3.24.2.u1
Pay vs Performance Disclosure - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Pay vs Performance Disclosure        
Net Income (Loss) to Common Stockholders $ 371,909 $ 356,308 $ 814,380 $ 650,434
v3.24.2.u1
Insider Trading Arrangements
 3 Months Ended
Jun. 30, 2024
Trading Arrangements, by Individual  
Rule 10b5-1 Arrangement Adopted false
Non-Rule 10b5-1 Arrangement Adopted false
Rule 10b5-1 Arrangement Terminated false
Non-Rule 10b5-1 Arrangement Terminated false
v3.24.2.u1
Recent Accounting Pronouncements and Accounting Policies (Policies)
 6 Months Ended
Jun. 30, 2024
Accounting Policies [Abstract]  
Per Share Data Per Share Data
    The Company presents both basic and diluted net income per share (“EPS”) amounts. Basic EPS is calculated by dividing net income by the weighted average number of common shares outstanding during the period (including 17,495,175 and 17,125,284 common shares held in a grantor trust as of June 30, 2024 and 2023, respectively). The common shares held in the grantor trust are for delivery upon settlement of vested but mandatorily deferred restricted stock units ("RSUs"). Shares held by the grantor trust do not affect diluted shares outstanding since the shares deliverable under vested RSUs were already included in diluted shares outstanding. Diluted EPS is based upon the weighted average number of basic and common equivalent shares outstanding during the period and is calculated using the treasury stock method for stock incentive plans. Common equivalent shares are excluded from the computation in periods in which they have an anti-dilutive effect.
    The weighted average number of common shares used in the computation of basic and diluted earnings per share was as follows:
For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Basic400,273 406,296 401,295 409,364 
Diluted403,737 409,643 404,679 412,819 
Recent Accounting Pronouncements Recent Accounting Pronouncements and Accounting Policies
Recently adopted accounting pronouncements:
    All accounting and reporting standards that became effective in 2024 were either not applicable to the Company or their adoption did not have a material impact on the Company.
Accounting and reporting standards that are not yet effective:
    All recently issued but not yet effective accounting and reporting standards are either not applicable to the Company or are not expected to have a material impact on the Company.
v3.24.2.u1
Per Share Data (Tables)
 6 Months Ended
Jun. 30, 2024
Earnings Per Share [Abstract]  
Weighted average number of common shares The weighted average number of common shares used in the computation of basic and diluted earnings per share was as follows:
For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Basic400,273 406,296 401,295 409,364 
Diluted403,737 409,643 404,679 412,819 
v3.24.2.u1
Consolidated Statements of Comprehensive (Loss) Income (Tables)
 6 Months Ended
Jun. 30, 2024
Equity [Abstract]  
Components of changes in accumulated other comprehensive income (loss) The following table presents the components of the changes in accumulated other comprehensive (loss) income ("AOCI"):
(In thousands)Unrealized Investment (Losses) GainsCurrency Translation AdjustmentsAccumulated Other Comprehensive
(Loss) Income
As of and for the six months ended June 30, 2024
Changes in AOCI
Beginning of period$(586,354)$(339,484)$(925,838)
Other comprehensive loss before reclassifications(156,023)(24,343)(180,366)
Amounts reclassified from AOCI72,563 — 72,563 
Other comprehensive loss(83,460)(24,343)(107,803)
Unrealized investment gain related to noncontrolling interest1 — 1 
End of period$(669,813)$(363,827)$(1,033,640)
Amounts reclassified from AOCI
Pre-tax$91,852 (1)$— $91,852 
Tax effect (19,289)(2)— (19,289)
After-tax amounts reclassified$72,563 $— $72,563 
Other comprehensive loss
Pre-tax$(109,937)$(24,343)$(134,280)
Tax effect26,477 — 26,477 
Other comprehensive loss$(83,460)$(24,343)$(107,803)
As of and for the three months ended June 30, 2024
Changes in AOCI
Beginning of period$(656,476)$(367,054)$(1,023,530)
Other comprehensive (loss) income before reclassifications(54,711)3,227 (51,484)
Amounts reclassified from AOCI41,373 — 41,373 
Other comprehensive (loss) income(13,338)3,227 (10,111)
Unrealized investment gain to noncontrolling interest1 — 1 
Ending balance$(669,813)$(363,827)$(1,033,640)
Amounts reclassified from AOCI
Pre-tax$52,371 (1)$— $52,371 
Tax effect (10,998)(2)— (10,998)
After-tax amounts reclassified$41,373 $— $41,373 
Other comprehensive (loss) income
Pre-tax$(20,640)$3,227 $(17,413)
Tax effect7,302 — 7,302 
Other comprehensive (loss) income$(13,338)$3,227 $(10,111)
(In thousands)Unrealized Investment (Losses) GainsCurrency Translation AdjustmentsAccumulated Other Comprehensive
(Loss) Income
As of and for the six months ended June 30, 2023
Changes in AOCI
Beginning of period$(892,905)$(371,676)$(1,264,581)
Other comprehensive income before reclassifications99,093 15,394 114,487 
Amounts reclassified from AOCI(31,578)— (31,578)
Other comprehensive income67,515 15,394 82,909 
Unrealized investment loss related to noncontrolling interest(1)— (1)
End of period$(825,391)$(356,282)$(1,181,673)
Amounts reclassified from AOCI
Pre-tax$(39,972)(1)$— $(39,972)
Tax effect 8,394 (2)— 8,394 
After-tax amounts reclassified$(31,578)$— $(31,578)
Other comprehensive income
Pre-tax$87,978 $15,394 $103,372 
Tax effect(20,463)— (20,463)
Other comprehensive income$67,515 $15,394 $82,909 
As of and for the three months ended June 30, 2023
Changes in AOCI
Beginning of period$(712,107)$(366,810)$(1,078,917)
Other comprehensive (loss) income before reclassifications(56,122)10,528 (45,594)
Amounts reclassified from AOCI(57,162)— (57,162)
Other comprehensive (loss) income(113,284)10,528 (102,756)
Unrealized investment loss related to noncontrolling interest— — — 
Ending balance$(825,391)$(356,282)$(1,181,673)
Amounts reclassified from AOCI
Pre-tax$(72,357)(1)$— $(72,357)
Tax effect 15,195 (2)— 15,195 
After-tax amounts reclassified$(57,162)$— $(57,162)
Other comprehensive (loss) income
Pre-tax$(144,043)$10,528 $(133,515)
Tax effect30,759 — 30,759 
Other comprehensive (loss) income$(113,284)$10,528 $(102,756)
____________
(1) Net investment (losses) gains in the consolidated statements of income.
(2) Income tax expense in the consolidated statements of income.
v3.24.2.u1
Investments in Fixed Maturity Securities (Tables)
 6 Months Ended
Jun. 30, 2024
Investments, Debt and Equity Securities [Abstract]  
Schedule of investments in fixed maturity securities At June 30, 2024 and December 31, 2023, investments in fixed maturity securities were as follows:
 
(In thousands)Amortized
Cost		Allowance for Expected Credit Losses (1)Gross UnrealizedFair
Value		Carrying
Value
GainsLosses
June 30, 2024
Held to maturity:
State and municipal$40,983 $(34)$1,766 $— $42,715 $40,949 
Residential mortgage-backed2,615 — 60 — 2,675 2,615 
Total held to maturity43,598 (34)1,826 — 45,390 43,564 
Available for sale:
U.S. government and government agency1,869,971 — 6,877 (54,472)1,822,376 1,822,376 
State and municipal:
Special revenue1,586,511 — 2,558 (80,860)1,508,209 1,508,209 
State general obligation416,788 — 1,862 (15,926)402,724 402,724 
Pre-refunded88,086 — 269 (377)87,978 87,978 
Corporate backed171,007 (339)582 (9,918)161,332 161,332 
Local general obligation390,455 — 1,254 (12,685)379,024 379,024 
Total state and municipal2,652,847 (339)6,525 (119,766)2,539,267 2,539,267 
Mortgage-backed:
Residential2,206,563 — 7,330 (178,950)2,034,943 2,034,943 
Commercial567,094 (1,140)313 (8,216)558,051 558,051 
Total mortgage-backed2,773,657 (1,140)7,643 (187,166)2,592,994 2,592,994 
Asset-backed4,071,678 (889)5,279 (61,622)4,014,446 4,014,446 
Corporate:
Industrial4,026,477 — 9,683 (142,415)3,893,745 3,893,745 
Financial3,253,805 — 7,899 (65,121)3,196,583 3,196,583 
Utilities735,920 — 1,614 (25,567)711,967 711,967 
Other616,007 — 1,247 (7,129)610,125 610,125 
Total corporate8,632,209 — 20,443 (240,232)8,412,420 8,412,420 
Foreign government1,867,457 (19,469)3,306 (193,685)1,657,609 1,657,609 
Total available for sale21,867,819 (21,837)50,073 (856,943)21,039,112 21,039,112 
Total investments in fixed maturity securities$21,911,417 $(21,871)$51,899 $(856,943)$21,084,502 $21,082,676 
____________
(1) Represents the amount of impairment that has resulted from credit-related factors. The change in the allowance for expected credit losses is recognized in the consolidated statements of income. Amount excludes unrealized losses relating to non-credit factors.
(In thousands)Amortized
Cost		Allowance for Expected Credit Losses (1)Gross UnrealizedFair
Value		Carrying
Value
GainsLosses
December 31, 2023
Held to maturity:
State and municipal$50,547 $(43)$3,132 $— $53,636 $50,504 
Residential mortgage-backed2,868 — 107 — 2,975 2,868 
Total held to maturity53,415 (43)3,239 — 56,611 53,372 
Available for sale:
U.S. government and government agency1,762,997 — 11,403 (57,669)1,716,731 1,716,731 
State and municipal:
Special revenue1,682,550 — 5,651 (82,006)1,606,195 1,606,195 
State general obligation394,429 — 3,550 (16,405)381,574 381,574 
Pre-refunded103,029 — 1,634 (185)104,478 104,478 
Corporate backed166,873 (757)696 (11,973)154,839 154,839 
Local general obligation396,041 — 3,188 (11,893)387,336 387,336 
Total state and municipal2,742,922 (757)14,719 (122,462)2,634,422 2,634,422 
Mortgage-backed:
Residential1,773,206 — 12,780 (163,844)1,622,142 1,622,142 
Commercial657,157 (158)626 (13,312)644,313 644,313 
Total mortgage-backed2,430,363 (158)13,406 (177,156)2,266,455 2,266,455 
Asset-backed4,252,883 (1,164)8,527 (73,206)4,187,040 4,187,040 
Corporate:
Industrial3,679,219 (40)24,312 (143,936)3,559,555 3,559,555 
Financial2,838,220 (4,986)14,681 (68,681)2,779,234 2,779,234 
Utilities701,865 — 6,471 (23,412)684,924 684,924 
Other635,975 — 1,605 (7,234)630,346 630,346 
Total corporate7,855,279 (5,026)47,069 (243,263)7,654,059 7,654,059 
Foreign government1,817,386 (29,603)15,865 (137,419)1,666,229 1,666,229 
Total available for sale20,861,830 (36,708)110,989 (811,175)20,124,936 20,124,936 
Total investments in fixed maturity securities$20,915,245 $(36,751)$114,228 $(811,175)$20,181,547 $20,178,308 
Debt Securities, Held-to-maturity, Allowance for Credit Loss
The following table presents the rollforward of the allowance for expected credit losses for held to maturity securities for the six months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$43 $114 
Provision for expected credit losses(9)(61)
Allowance for expected credit losses, end of period$34 $53 
Debt Securities, Available-for-sale, Allowance for Credit Loss
The following table presents the rollforward of the allowance for expected credit losses for held to maturity securities for the three months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$38 $107 
Provision for expected credit losses(4)(54)
Allowance for expected credit losses, end of period$34 $53 
The following table presents the rollforward of the allowance for expected credit losses for available for sale securities for the six months ended June 30, 2024 and 2023:
20242023
(In thousands)Foreign GovernmentCorporateMortgage-backedAsset-backedState and MunicipalTotalForeign GovernmentCorporateMortgage-backedAsset-backedTotal
Allowance for expected credit losses, beginning of period$29,603 $5,026 $158 $1,164 $757 $36,708 $32,633 $4,701 $18 $— $37,352 
Expected credit losses on securities for which credit losses were not previously recorded300 — 1,701 — — 2,001 — 186 861 1,444 2,491 
Expected credit (gains) losses on securities for which credit losses were previously recorded(10,434)(5,026)(158)(275)(418)(16,311)419 3,987 6 — 4,412 
Reduction due to disposals— — (561)— — (561)— (7)— — (7)
Allowance for expected credit losses, end of period$19,469 $— $1,140 $889 $339 $21,837 $33,052 $8,867 $885 $1,444 $44,248 
Amortized cost and fair value of fixed maturity securities by contractual maturity
The amortized cost and fair value of fixed maturity securities at June 30, 2024, by contractual maturity, are shown below. Actual maturities may differ from contractual maturities because certain issuers may have the right to call or prepay obligations.
(In thousands)Amortized
Cost (1)		Fair
Value
Due in one year or less$1,943,246 $1,884,790 
Due after one year through five years9,983,542 9,601,275 
Due after five years through ten years4,262,692 4,152,066 
Due after ten years2,945,631 2,850,702 
Mortgage-backed securities2,776,272 2,595,669 
Total$21,911,383 $21,084,502 
_______________
(1) Amortized cost is reduced by the allowance for expected credit losses of $34 thousand related to held to maturity securities.
v3.24.2.u1
Investments in Equity Securities (Tables)
 6 Months Ended
Jun. 30, 2024
Equity securities  
Debt Securities, Available-for-sale [Line Items]  
Schedule of Investments in Equity Securities At June 30, 2024 and December 31, 2023, investments in equity securities were as follows:
 
(In thousands)CostGross UnrealizedFair
Value		Carrying
Value
GainsLosses
June 30, 2024
Common stocks$603,574 $139,146 $(46,165)$696,555 $696,555 
Preferred stocks374,409 19,762 (12,634)381,537 381,537 
Total$977,983 $158,908 $(58,799)$1,078,092 $1,078,092 
December 31, 2023
Common stocks$664,997 $191,806 $(18,749)$838,054 $838,054 
Preferred stocks284,335 3,075 (35,117)252,293 252,293 
Total$949,332 $194,881 $(53,866)$1,090,347 $1,090,347 
v3.24.2.u1
Net Investment Income (Tables)
 6 Months Ended
Jun. 30, 2024
Net Investment Income [Abstract]  
Schedule of Net Investment Income Net investment income consisted of the following: 
 For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Investment income (loss) earned on:
Fixed maturity securities, including cash and cash equivalents and loans receivable$324,136 $217,830 $659,384 $413,473 
Arbitrage trading account (1)16,682 17,037 34,693 35,293 
Equity securities12,386 15,254 23,721 29,000 
Investment funds25,476 (1,186)(3,873)993 
Real estate(3,705)(2,123)(16,868)(5,834)
Gross investment income374,975 246,812 697,057 472,925 
Investment expense(2,846)(1,660)(5,090)(4,374)
Net investment income$372,129 $245,152 $691,967 $468,551 
(1) Net investment income includes earnings from trading account receivables from brokers and clearing organizations.
v3.24.2.u1
Investment Funds (Tables)
 6 Months Ended
Jun. 30, 2024
Equity Method Investments and Joint Ventures [Abstract]  
Schedule of Investment Funds Investment funds consisted of the following:
Carrying Value as of Income (Loss) from
Investment Funds
June 30,December 31,For the Six Months
Ended June 30,
(In thousands)2024202320242023
Financial services$436,057 $433,407 $(18,231)$(20,321)
Transportation306,485 344,278 (3,732)23,843 
Real Estate198,111 201,625 12,880 2,963 
Infrastructure140,699 130,589 7,828 5,936 
Energy131,719 114,794 8,505 3,439 
Other funds376,048 396,962 (11,123)(14,867)
Total$1,589,119 $1,621,655 $(3,873)$993 
v3.24.2.u1
Real Estate (Tables)
 6 Months Ended
Jun. 30, 2024
Real Estate [Abstract]  
Schedule of Real Estate Investments Investment in real estate represents directly owned property held for investment, as follows:
Carrying Value
June 30,December 31,
(In thousands)20242023
Properties in operation$1,051,755 $1,022,654 
Properties under development227,551 227,220 
Total$1,279,306 $1,249,874 
v3.24.2.u1
Loans Receivable Loans Receivable (Tables)
 6 Months Ended
Jun. 30, 2024
Receivables [Abstract]  
Schedule of Loans Receivable
At June 30, 2024 and December 31, 2023, loans receivable were as follows:
(In thousands)June 30,
2024		December 31,
2023
Amortized cost (net of allowance for expected credit losses):
Real estate loans$347,742 $200,381 
Commercial loans1,583 890 
Total$349,325 $201,271 
Fair value:
Real estate loans$347,727 $197,354 
Commercial loans1,583 890 
Total$349,310 $198,244 
Financing Receivable, Allowance for Credit Loss
The following table presents the rollforward of the allowance for expected credit losses for loans receivable for the six months ended June 30, 2024 and 2023:
20242023
(In thousands)Real Estate LoansCommercial LoansTotalReal Estate LoansCommercial LoansTotal
Allowance for expected credit losses, beginning of period$2,983 $21 $3,004 $1,100 $691 $1,791 
Change in expected credit losses(1,190)(1)(1,191)2,558 201 2,759 
Allowance for expected credit losses, end of period$1,793 $20 $1,813 $3,658 $892 $4,550 
During the six months ended June 30, 2024, the Company decreased the allowance for expected credit losses due to a decrease in the weighted average life of the loan portfolio. During the six months ended June 30, 2023, the Company increased the allowance for expected credit losses due to changes in economic assumptions utilized in its credit loss model.
The following table presents the rollforward of the allowance for expected credit losses for loans receivable for the three months ended June 30, 2024 and 2023:
20242023
(In thousands)Real Estate LoansCommercial LoansTotalReal Estate LoansCommercial LoansTotal
Allowance for expected credit losses, beginning of period$2,587 $22 $2,609 $1,039 $570 $1,609 
Change in expected credit losses(794)(2)(796)2,619 322 2,941 
Allowance for expected credit losses, end of period$1,793 $20 $1,813 $3,658 $892 $4,550 
v3.24.2.u1
Net Investment (Losses) Gains (Tables)
 6 Months Ended
Jun. 30, 2024
Realized and Unrealized Investment Gains (Losses) [Abstract]  
Realized And Unrealized Investment Gains (Losses) Net investment (losses) gains were as follows:
For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Net investment (losses) gains:  
Fixed maturity securities:  
Gains$3,092 $115 $6,649 $1,058 
Losses(5,362)(3,640)(7,685)(21,770)
Equity securities (1):
Net realized gains on investment sales (2)61,521 111,072 101,798 112,132 
Change in unrealized (losses) gains(66,717)21,260 (40,905)64,664 
Investment funds217 (98)1,210 (88)
Real estate (3)(1,958)(55,449)(4,174)(44,710)
Loans receivable— — — — 
Other (4)(51,099)(4,613)(105,696)(20,028)
Net realized and unrealized (losses) gains on investments in earnings before allowance for expected credit losses(60,306)68,647 (48,803)91,258 
Change in allowance for expected credit losses on investments:
Fixed maturity securities998 (7,052)14,879 (6,835)
Loans receivable796 (2,941)1,191 (2,759)
Change in allowance for expected credit losses on investments1,794 (9,993)16,070 (9,594)
Net investment (losses) gains(58,512)58,654 (32,733)81,664 
Income tax benefit12,401 (12,587)5,769 (17,437)
After-tax net investment (losses) gains$(46,111)$46,067 $(26,964)$64,227 
Change in unrealized investment (losses) gains on available for sale securities:  
Fixed maturity securities without allowance for expected credit losses$(11,394)$(148,021)$(99,988)$79,094 
Fixed maturity securities with allowance for expected credit losses(7,683)3,694 (6,696)7,150 
Investment funds(1,338)462 (3,041)2,398 
Other(225)(178)(212)(664)
Total change in unrealized investment (losses) gains(20,640)(144,043)(109,937)87,978 
Income tax benefit (expense)7,302 30,759 26,477 (20,463)
Noncontrolling interests1 — 1 (1)
After-tax change in unrealized investment (losses) gains of available for sale securities$(13,337)$(113,284)$(83,459)$67,514 
______________________
(1) The net realized gains or losses on investment sales represent the total gains or losses from the purchase dates of the equity securities. The change in unrealized (losses) gains consists of two components: (i) the reversal of the gain or loss recognized in previous periods on equity securities sold and (ii) the change in unrealized gain or loss resulting from mark-to-market adjustments on equity securities still held.
(2) In June 2023, the Company completed a sale of the property and casualty insurance services division of Breckenridge IS, Inc. and recognized a pre-tax net realized gain on investment of $88 million on the sale (proceeds from the sale is presented on the business disposition line within the Consolidated Statements of Cash Flows).
(3) During the second quarter of 2023, the Company recognized an impairment loss of $51 million on a real estate investment.
(4) Primarily relates to realized foreign currency losses upon the disposition of fixed maturity securities.
v3.24.2.u1
Fixed Maturity Securities In An Unrealized Loss Position (Tables)
 6 Months Ended
Jun. 30, 2024
Investments, Debt and Equity Securities [Abstract]  
Securities in an unrealized loss position The following tables summarize all fixed maturity securities in an unrealized loss position at June 30, 2024 and December 31, 2023 by the length of time those securities have been continuously in an unrealized loss position:
  Less Than 12 Months12 Months or GreaterTotal
(In thousands)Fair
Value		Gross
Unrealized Losses		Fair
Value		Gross
Unrealized Losses		Fair
Value		Gross
Unrealized Losses
June 30, 2024
U.S. government and government agency$422,945 $3,391 $795,297 $51,081 $1,218,242 $54,472 
State and municipal357,529 4,935 1,758,572 114,831 2,116,101 119,766 
Mortgage-backed530,802 4,258 1,356,573 182,908 1,887,375 187,166 
Asset-backed947,780 4,434 1,079,695 57,188 2,027,475 61,622 
Corporate2,068,015 17,788 4,333,968 222,444 6,401,983 240,232 
Foreign government563,150 15,565 759,174 178,120 1,322,324 193,685 
Fixed maturity securities$4,890,221 $50,371 $10,083,279 $806,572 $14,973,500 $856,943 
December 31, 2023
U.S. government and government agency$384,392 $6,655 $614,623 $51,014 $999,015 $57,669 
State and municipal264,273 3,013 1,680,034 119,449 1,944,307 122,462 
Mortgage-backed278,819 2,025 1,360,748 175,131 1,639,567 177,156 
Asset-backed413,511 2,070 2,176,035 71,136 2,589,546 73,206 
Corporate874,754 11,975 4,418,309 231,288 5,293,063 243,263 
Foreign government204,908 1,758 794,174 135,661 999,082 137,419 
Fixed maturity securities$2,420,657 $27,496 $11,043,923 $783,679 $13,464,580 $811,175 
Non-Investment Grade Fixed Maturity Securities A summary of the Company’s non-investment grade fixed maturity securities that were in an unrealized loss position at June 30, 2024 is presented in the table below:
($ in thousands)Number of
Securities		Aggregate
Fair Value		Gross
Unrealized Loss
Foreign government51 $99,230 $159,930 
State and municipal5 24,865 4,838 
Corporate30 42,131 2,651 
Mortgage-backed16 4,107 201 
Total102 $170,333 $167,620 
v3.24.2.u1
Fair Value Measurements (Tables)
 6 Months Ended
Jun. 30, 2024
Fair Value Disclosures [Abstract]  
Assets And Liabilities Measured At Fair value, On A Recurring Basis The following tables present the assets and liabilities measured at fair value on a recurring basis as of June 30, 2024 and December 31, 2023 by level:
(In thousands)TotalLevel 1Level 2Level 3
June 30, 2024
Assets:
Fixed maturity securities available for sale:
U.S. government and government agency$1,822,376 $— $1,822,376 $— 
State and municipal2,539,267 — 2,539,267 — 
Mortgage-backed2,592,994 — 2,592,994 — 
Asset-backed4,014,446 — 4,014,446 — 
Corporate8,412,420 — 8,412,420 — 
Foreign government1,657,609 — 1,657,609 — 
Total fixed maturity securities available for sale21,039,112 — 21,039,112 — 
Equity securities:
Common stocks696,555 693,294 1,116 2,145 
Preferred stocks381,537 — 377,901 3,636 
Total equity securities1,078,092 693,294 379,017 5,781 
Arbitrage trading account1,221,861 1,061,891 156,377 3,593 
Total$23,339,065 $1,755,185 $21,574,506 $9,374 
Liabilities:
Trading account securities sold but not yet purchased$81,273 $81,273 $— $— 
December 31, 2023
Assets:
Fixed maturity securities available for sale:
U.S. government and government agency$1,716,731 $— $1,716,731 $— 
State and municipal2,634,422 — 2,634,422 — 
Mortgage-backed2,266,455 — 2,266,455 — 
Asset-backed4,187,040 — 4,187,040 — 
Corporate7,654,059 — 7,654,059 — 
Foreign government1,666,229 — 1,666,229 — 
Total fixed maturity securities available for sale20,124,936 — 20,124,936 — 
Equity securities:
Common stocks838,054 835,338 1,158 1,558 
Preferred stocks252,293 — 248,598 3,695 
Total equity securities1,090,347 835,338 249,756 5,253 
Arbitrage trading account938,049 546,110 388,167 3,772 
Total$22,153,332 $1,381,448 $20,762,859 $9,025 
Liabilities:
Trading account securities sold but not yet purchased$9,357 $9,357 $— $— 
Summarize Changes In Level 3 Assets The following tables summarize changes in Level 3 assets and liabilities for the six months ended June 30, 2024 and for the year ended December 31, 2023:
Gains (Losses) Included In:
(In thousands)Beginning
Balance		Earnings (Losses)Other
Comprehensive
Income (Losses)		ImpairmentsPurchasesSalesPaydowns / MaturitiesTransfers In / (Out)Ending
Balance
Six Months Ended June 30, 2024
Assets:
Equity securities:
Common stocks$1,558 $715 $— $— $— $(128)$— $— $2,145 
Preferred stocks3,695 (2)— — — (57)— — 3,636 
Total5,253 713 — — — (185)— — 5,781 
Arbitrage trading account3,772 (178)— — — (38)— 37 3,593 
Total$9,025 $535 $— $— $— $(223)$— $37 $9,374 
Year Ended
December 31, 2023
Assets:
Equity securities:
Common stocks$2,599 $(1,041)$— $— $— $— $— $— $1,558 
Preferred stocks11,299 (3)— (7,601)— — — — 3,695 
Total13,898 (1,044)— (7,601)— — — — 5,253 
Arbitrage trading account3,590 117 — — — — — 65 3,772 
Total$17,488 $(927)$— $(7,601)$— $— $— $65 $9,025 
v3.24.2.u1
Reserves for Loss and Loss Expenses (Tables)
 6 Months Ended
Jun. 30, 2024
Insurance [Abstract]  
Reserve Balances The table below provides a reconciliation of the beginning and ending reserve balances:
June 30,
(In thousands)20242023
Net reserves at beginning of period$15,661,820 $14,248,879 
Net provision for losses and loss expenses:
Claims occurring during the current year (1)3,411,888 3,064,046 
Increase in estimates for claims occurring in prior years (2) (3)14,700 28,853 
Loss reserve discount accretion 17,786 15,510 
Total3,444,374 3,108,409 
Net payments for claims:  
Current year383,639 375,365 
Prior years2,205,566 2,019,371 
Total2,589,205 2,394,736 
Foreign currency translation(56,143)5,929 
Net reserves at end of period16,460,846 14,968,481 
Ceded reserves at end of period3,106,344 2,951,515 
Gross reserves at end of period$19,567,190 $17,919,996 
_______________________________________
(1) Claims occurring during the current year are net of loss reserve discounts of $26 million and $22 million for the six months ended June 30, 2024 and 2023, respectively.
(2) The change in estimates for claims occurring in prior years is net of loss reserve discount. On an undiscounted basis, the estimates for claims occurring in prior years increased by $7 million and decreased by $6 million for the six months ended June 30, 2024 and 2023, respectively.
(3) For certain retrospectively rated insurance policies and reinsurance agreements, reserve development is offset by additional or return premiums. Favorable development, net of additional and return premiums, was $2 million and adverse development was $21 million for the six months ended June 30, 2024 and 2023, respectively.
v3.24.2.u1
Fair Value of Financial Instruments (Tables)
 6 Months Ended
Jun. 30, 2024
Fair Value Disclosures [Abstract]  
Carrying Amounts And Estimated Fair Values Of Financial Instruments The following table presents the carrying amounts and estimated fair values of the Company’s financial instruments:
  June 30, 2024December 31, 2023
(In thousands)Carrying ValueFair ValueCarrying ValueFair Value
Assets:
Fixed maturity securities$21,082,676 $21,084,502 $20,178,308 $20,181,547 
Equity securities1,078,092 1,078,092 1,090,347 1,090,347 
Arbitrage trading account1,221,861 1,221,861 938,049 938,049 
Loans receivable349,325 349,310 201,271 198,244 
Cash and cash equivalents1,580,270 1,580,270 1,363,195 1,363,195 
Trading account receivables from brokers and clearing organizations40,705 40,705 303,614 303,614 
     Due from broker— — 36,747 36,747 
Liabilities:
Due to broker128,563 128,563 — — 
Trading account securities sold but not yet purchased81,273 81,273 9,357 9,357 
Senior notes and other debt1,828,422 1,422,506 1,827,951 1,480,076 
Subordinated debentures1,009,449 825,344 1,009,090 929,598 
v3.24.2.u1
Premiums and Reinsurance Related Information (Tables)
 6 Months Ended
Jun. 30, 2024
Insurance [Abstract]  
Reinsurance Financial Information
The following is a summary of insurance and reinsurance financial information:
For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Written premiums:
Direct$3,380,470 $2,985,563 $6,419,537 $5,724,317 
Assumed337,302 351,210 660,991 661,773 
Ceded(590,993)(525,258)(1,102,458)(999,751)
Total net premiums written$3,126,779 $2,811,515 $5,978,070 $5,386,339 
Earned premiums:
Direct$3,048,872 $2,725,650 $5,985,516 $5,392,712 
Assumed328,114 302,431 666,024 597,661 
Ceded(530,571)(475,354)(1,040,778)(946,214)
Total net premiums earned$2,846,415 $2,552,727 $5,610,762 $5,044,159 
Ceded losses and loss expenses incurred$327,243 $333,795 $633,194 $649,271 
Ceded commissions earned$123,647 $117,523 $244,701 $235,941 
Premium receivable, allowance for credit loss The following table presents the rollforward of the allowance for expected credit losses for premiums and fees receivable for the six months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$35,110 $30,660 
Change in expected credit losses2,169 2,110 
Allowance for expected credit losses, end of period$37,279 $32,770 
The following table presents the rollforward of the allowance for expected credit losses for premiums and fees receivable for the three months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$35,039 $32,353 
Change in expected credit losses2,240 417 
Allowance for expected credit losses, end of period$37,279 $32,770 
Reinsurance Recoverable, Allowance for Credit Loss
The following table presents the rollforward of the allowance for expected credit losses associated with due from reinsurers for the six months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$8,404 $8,064 
Change in expected credit losses1,851 1,301 
Allowance for expected credit losses, end of period$10,255 $9,365 
The following table presents the rollforward of the allowance for expected credit losses associated with due from reinsurers for the three months ended June 30, 2024 and 2023:
(In thousands)20242023
Allowance for expected credit losses, beginning of period$9,185 $8,703 
Change in expected credit losses1,070 662 
Allowance for expected credit losses, end of period$10,255 $9,365 
v3.24.2.u1
Restricted Stock Units (Tables)
 6 Months Ended
Jun. 30, 2024
Share-Based Payment Arrangement [Abstract]  
Summary Of Restricted Stock Units Issued A summary of RSUs issued in the six months ended June 30, 2024 and 2023 follows:
($ in thousands)
UnitsFair Value
20242,277 $125 
20238,381 $332 
v3.24.2.u1
Leases (Tables)
 6 Months Ended
Jun. 30, 2024
Leases [Abstract]  
Lease, Cost Further information relating to operating lease expense and other operating lease information are as follows:
 For the Three Months Ended
June 30,		For the Six Months Ended June 30,
(In thousands)2024202320242023
Leases:
Lease cost$11,326 $10,138 $22,403 $20,326 
Cash paid for amounts included in the measurement of lease liabilities reported in operating cash flows$12,364 $11,281 $24,596 $21,844 
Right-of-use assets obtained in exchange for new lease liabilities$8,853 $2,633 $33,548 $7,946 
Supplemental Balance Sheet Information
As of June 30,
($ in thousands)20242023
Right-of-use assets$190,207$157,991
Lease liabilities$231,128$191,576
Weighted-average remaining lease term7.5 years7.0 years
Weighted-average discount rate5.51 %4.49 %
Maturities of Operating Lease Liabilities
Contractual maturities of the Company’s future minimum lease payments are as follows:
(In thousands)June 30, 2024
Contractual Maturities:
2024$26,008 
202545,629 
202639,117 
202730,117 
202828,576 
Thereafter107,255 
Total undiscounted future minimum lease payments276,702 
Less: Discount impact45,574 
Total lease liability$231,128 
v3.24.2.u1
Business Segments (Tables)
 6 Months Ended
Jun. 30, 2024
Segment Reporting [Abstract]  
Financial Information Of Company Operating Segments
  Revenues  
(In thousands)Earned
Premiums (1)		Investment
Income 		OtherTotal (2)Pre-Tax Income (Loss)Net Income (Loss) to Common Stockholders
Three months ended June 30, 2024
Insurance$2,484,569 $303,561 $9,591 $2,797,721 $490,053 $374,247 
Reinsurance & Monoline Excess361,846 58,472 — 420,318 124,449 97,638 
Corporate, other and eliminations (3)— 10,096 144,409 154,505 (68,317)(53,865)
Net investment losses— — (58,512)(58,512)(58,512)(46,111)
Total$2,846,415 $372,129 $95,488 $3,314,032 $487,673 $371,909 
Three months ended June 30, 2023
Insurance$2,215,186 $185,327 $8,853 $2,409,366 $386,350 $300,239 
Reinsurance & Monoline Excess337,541 42,187 — 379,728 105,420 82,317 
Corporate, other and eliminations (3)— 17,638 130,528 148,166 (93,240)(72,315)
Net investment gains— — 58,654 58,654 58,654 46,067 
Total$2,552,727 $245,152 $198,035 $2,995,914 $457,184 $356,308 
Six months ended June 30, 2024
Insurance$4,883,338 $548,338 $19,014 $5,450,690 $968,202 $739,337 
Reinsurance & Monoline Excess727,424 111,683 — 839,107 252,074 199,764 
Corporate, other and eliminations (3)— 31,946 281,795 313,741 (125,799)(97,757)
Net investment losses— — (32,733)(32,733)(32,733)(26,964)
Total$5,610,762 $691,967 $268,076 $6,570,805 $1,061,744 $814,380 
Six Months Ended June 30, 2023
Insurance$4,358,110 $348,886 $18,427 $4,725,423 $738,977 $574,347 
Reinsurance & Monoline Excess686,049 96,770 — 782,819 206,704 164,674 
Corporate, other and eliminations (3)— 22,895 278,117 301,012 (194,089)(152,814)
Net investment gains— — 81,664 81,664 81,664 64,227 
Total$5,044,159 $468,551 $378,208 $5,890,918 $833,256 $650,434 
_________________
(1) Certain amounts included in earned premiums of each segment are related to inter-segment transactions.
(2) Revenues for Insurance from foreign operations for the three months ended June 30, 2024 and 2023 were $368 million and $280 million, respectively, and for the six months ended June 30, 2024 and 2023 were $762 million and $554 million, respectively. Revenues for Reinsurance & Monoline Excess from foreign operations for the three months ended June 30, 2024 and 2023 were $117 million and $102 million, respectively, and for the six months ended June 30, 2024 and 2023 were $228 million and $209 million, respectively.
(3) Corporate, other and eliminations represent corporate revenues and expenses that are not allocated to business segments
Identifiable Assets By Segment
(In thousands)June 30,
2024		December 31,
2023
Insurance$31,264,338 $29,923,282 
Reinsurance & Monoline Excess5,557,232 5,545,249 
Corporate, other and eliminations2,088,349 1,643,299 
Consolidated$38,909,919 $37,111,830 
Net Premiums Earned By Major Line Of Business Net premiums earned by major line of business are as follows:
 For the Three Months
Ended June 30,		For the Six Months
Ended June 30,
(In thousands)2024202320242023
Insurance:
Other liability$1,001,987 $890,984 $1,969,247 $1,744,456 
Short-tail lines (1)538,797 444,834 1,049,606 857,368 
Auto361,580 307,578 715,593 601,694 
Workers' compensation310,564 299,149 612,060 604,710 
Professional liability271,641 272,641 536,832 549,882 
Total Insurance2,484,569 2,215,186 4,883,338 4,358,110 
Reinsurance & Monoline Excess:
Casualty (2)199,080 202,348 396,924 417,060 
Property (2)97,255 76,348 199,638 151,500 
Monoline excess (3)65,511 58,845 130,862 117,489 
Total Reinsurance & Monoline Excess361,846 337,541 727,424 686,049 
Total$2,846,415 $2,552,727 $5,610,762 $5,044,159 
______________
(1) Short-tail lines include commercial multi-peril (non-liability), inland marine, accident and health, fidelity and surety, boiler and machinery, high net worth homeowners and other lines.
(2) Includes reinsurance casualty and property and certain program management business.
(3) Monoline excess includes operations that solely retain risk on an excess basis.
v3.24.2.u1
Per Share Data (Narrative) (Details) - shares
 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Earnings Per Share [Abstract]    
Weighted average number of shares held in grantor trust (in shares) 17,495,175,000 17,125,284
v3.24.2.u1
Per Share Data (Weighted Average Number of Common Shares Used In the Computation of Basic and Diluted Earnings per Share) (Details) - shares
shares in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Earnings Per Share [Abstract]        
Basic (shares) 400,273 406,296 401,295 409,364
Diluted (shares) 403,737 409,643 404,679 412,819
v3.24.2.u1
Consolidated Statements of Comprehensive (Loss) Income (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning of period     $ 7,469,237  
Other comprehensive (loss) income $ (10,111) $ (102,756) (107,803) $ 82,909
End of period 7,787,051   7,787,051  
Net realized and unrealized (losses) gains on investments (60,306) 68,647 (48,803) 91,258
Income before income taxes 487,673 457,184 1,061,744 833,256
Tax effect (115,788) (101,460) (247,824) (181,803)
Net income before noncontrolling interests 371,885 355,724 813,920 651,453
Total change in unrealized investment (losses) gains (20,640) (144,043) (109,937) 87,978
Net change in period 3,227 10,528 (24,343) 15,394
Other comprehensive income (loss), pre-tax (17,413) (133,515) (134,280) 103,372
Other comprehensive income (loss), tax effect 7,302 30,759 26,477 (20,463)
Other comprehensive income (loss), net of tax (10,111) (102,756) (107,803) 82,909
Accumulated Other Comprehensive Income (Loss)        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning of period (1,023,530) (1,078,917) (925,838) (1,264,581)
Other comprehensive loss before reclassifications (51,484) (45,594) (180,366) 114,487
Amounts reclassified from AOCI 41,373 (57,162) 72,563 (31,578)
Other comprehensive (loss) income (10,111) (102,756) (107,803) 82,909
Unrealized investment gain related to noncontrolling interest 1 0 1 (1)
End of period (1,033,640) (1,181,673) (1,033,640) (1,181,673)
Other comprehensive income (loss), net of tax (10,111) (102,756) (107,803) 82,909
Accumulated Other Comprehensive Income (Loss) | Amounts reclassified from AOCI        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Income before income taxes 52,371 (72,357) 91,852 (39,972)
Tax effect (10,998) 15,195 (19,289) 8,394
Net income before noncontrolling interests 41,373 (57,162) 72,563 (31,578)
Unrealized investment losses:        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning of period (656,476) (712,107) (586,354) (892,905)
Other comprehensive loss before reclassifications (54,711) (56,122) (156,023) 99,093
Amounts reclassified from AOCI 41,373 (57,162) 72,563 (31,578)
Other comprehensive (loss) income (13,338) (113,284) (83,460) 67,515
Unrealized investment gain related to noncontrolling interest 1 0 1 (1)
End of period (669,813) (825,391) (669,813) (825,391)
Total change in unrealized investment (losses) gains (20,640) (144,043) (109,937) 87,978
Unrealized investment gains, tax effect 7,302 30,759 26,477 (20,463)
Unrealized investment gains (losses), after-tax amounts (13,338) (113,284) (83,460) 67,515
Other comprehensive income (loss), net of tax (13,338) (113,284) (83,460) 67,515
Unrealized investment losses: | Amounts reclassified from AOCI        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Net realized and unrealized (losses) gains on investments 52,371 (72,357) 91,852 (39,972)
Tax effect (10,998) 15,195 (19,289) 8,394
Net income before noncontrolling interests 41,373 (57,162) 72,563 (31,578)
Currency Translation Adjustments        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Beginning of period (367,054) (366,810) (339,484) (371,676)
Other comprehensive loss before reclassifications 3,227 10,528 (24,343) 15,394
Amounts reclassified from AOCI 0 0   0
Other comprehensive (loss) income 3,227 10,528 (24,343) 15,394
Unrealized investment gain related to noncontrolling interest   0 0 0
End of period (363,827) (356,282) (363,827) (356,282)
Currency translation adjustment, pre-tax 3,227 10,528 (24,343) 15,394
Currency translation adjustment, tax effect 0 0 0 0
Net change in period 3,227 10,528 (24,343) 15,394
Other comprehensive income (loss), net of tax 3,227 10,528 (24,343) 15,394
Currency Translation Adjustments | Amounts reclassified from AOCI        
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]        
Income before income taxes 0 0 0 0
Tax effect 0 0 0 0
Net income before noncontrolling interests $ 0 $ 0 $ 0 $ 0
v3.24.2.u1
Statements of Cash Flows (Details) - USD ($)
 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Supplemental Cash Flow Elements [Abstract]    
Interest payments $ 63,051,000 $ 62,983,000
Income taxes paid $ 165,739,000 $ 158,000,000
v3.24.2.u1
Investments in Fixed Maturity Securities (Investments in fixed maturity securities) (Details) - USD ($)
$ in Thousands
Jun. 30, 2024
Mar. 31, 2024
Dec. 31, 2023
Jun. 30, 2023
Mar. 31, 2023
Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]            
Held to maturity, Amortized cost $ 43,598   $ 53,415      
Held-to-maturity, Allowance for Credit Loss (34) $ (38) (43) $ (53) $ (107) $ (114)
Held to maturity, Gross Unrealized Gains 1,826   3,239      
Held to maturity, Gross Unrealized Losses 0   0      
Total held to maturity, Fair Value 45,390   56,611      
Held to maturity, Carrying Value 43,564   53,372      
Total available for sale, Amortized Cost 21,867,819   20,861,830      
Available-for-sale, Allowance for Credit Loss (21,837) (22,831) (36,708) (44,248) (37,142) (37,352)
Total available for sale, Gross Unrealized Gains 50,073   110,989      
Total available for sale, Gross Unrealized Losses (856,943)   (811,175)      
Total available for sale, Fair Value 21,039,112   20,124,936      
Total fixed maturity securities available for sale 21,039,112   20,124,936      
Fixed maturity securities, amortized cost 21,911,417   20,915,245      
Fixed maturity securities, allowance for credit loss (21,871)   (36,751)      
Total investments in fixed maturity securities, Gross Unrealized Gains 51,899   114,228      
Total investments in fixed maturity securities, Gross Unrealized Losses (856,943)   (811,175)      
Total investments in fixed maturity securities, Fair Value 21,084,502   20,181,547      
Total investments in fixed maturity securities, Carrying Value 21,082,676   20,178,308      
State and municipal            
Debt Securities, Available-for-sale [Line Items]            
Held to maturity, Amortized cost 40,983   50,547      
Held-to-maturity, Allowance for Credit Loss (34)   (43)      
Held to maturity, Gross Unrealized Gains 1,766   3,132      
Held to maturity, Gross Unrealized Losses 0   0      
Total held to maturity, Fair Value 42,715   53,636      
Held to maturity, Carrying Value 40,949   50,504      
Total available for sale, Amortized Cost 2,652,847   2,742,922      
Available-for-sale, Allowance for Credit Loss (339) (693) (757)      
Total available for sale, Gross Unrealized Gains 6,525   14,719      
Total available for sale, Gross Unrealized Losses (119,766)   (122,462)      
Total available for sale, Fair Value 2,539,267   2,634,422      
Total fixed maturity securities available for sale 2,539,267   2,634,422      
Residential mortgage-backed            
Debt Securities, Available-for-sale [Line Items]            
Held to maturity, Amortized cost 2,615   2,868      
Held-to-maturity, Allowance for Credit Loss 0   0      
Held to maturity, Gross Unrealized Gains 60   107      
Held to maturity, Gross Unrealized Losses 0   0      
Total held to maturity, Fair Value 2,675   2,975      
Held to maturity, Carrying Value 2,615   2,868      
Total available for sale, Amortized Cost 2,206,563   1,773,206      
Available-for-sale, Allowance for Credit Loss 0   0      
Total available for sale, Gross Unrealized Gains 7,330   12,780      
Total available for sale, Gross Unrealized Losses (178,950)   (163,844)      
Total available for sale, Fair Value 2,034,943   1,622,142      
Total fixed maturity securities available for sale 2,034,943   1,622,142      
U.S. government and government agency            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 1,869,971   1,762,997      
Available-for-sale, Allowance for Credit Loss 0   0      
Total available for sale, Gross Unrealized Gains 6,877   11,403      
Total available for sale, Gross Unrealized Losses (54,472)   (57,669)      
Total available for sale, Fair Value 1,822,376   1,716,731      
Total fixed maturity securities available for sale 1,822,376   1,716,731      
Special revenue            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 1,586,511   1,682,550      
Available-for-sale, Allowance for Credit Loss 0   0      
Total available for sale, Gross Unrealized Gains 2,558   5,651      
Total available for sale, Gross Unrealized Losses (80,860)   (82,006)      
Total available for sale, Fair Value 1,508,209   1,606,195      
Total fixed maturity securities available for sale 1,508,209   1,606,195      
State general obligation            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 416,788   394,429      
Available-for-sale, Allowance for Credit Loss 0   0      
Total available for sale, Gross Unrealized Gains 1,862   3,550      
Total available for sale, Gross Unrealized Losses (15,926)   (16,405)      
Total available for sale, Fair Value 402,724   381,574      
Total fixed maturity securities available for sale 402,724   381,574      
Pre-refunded            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 88,086   103,029      
Available-for-sale, Allowance for Credit Loss 0   0      
Total available for sale, Gross Unrealized Gains 269   1,634      
Total available for sale, Gross Unrealized Losses (377)   (185)      
Total available for sale, Fair Value 87,978   104,478      
Total fixed maturity securities available for sale 87,978   104,478      
Corporate backed            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 171,007   166,873      
Available-for-sale, Allowance for Credit Loss (339)   (757)      
Total available for sale, Gross Unrealized Gains 582   696      
Total available for sale, Gross Unrealized Losses (9,918)   (11,973)      
Total available for sale, Fair Value 161,332   154,839      
Total fixed maturity securities available for sale 161,332   154,839      
Local general obligation            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 390,455   396,041      
Available-for-sale, Allowance for Credit Loss 0   0      
Total available for sale, Gross Unrealized Gains 1,254   3,188      
Total available for sale, Gross Unrealized Losses (12,685)   (11,893)      
Total available for sale, Fair Value 379,024   387,336      
Total fixed maturity securities available for sale 379,024   387,336      
Commercial            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 567,094   657,157      
Available-for-sale, Allowance for Credit Loss (1,140)   (158)      
Total available for sale, Gross Unrealized Gains 313   626      
Total available for sale, Gross Unrealized Losses (8,216)   (13,312)      
Total available for sale, Fair Value 558,051   644,313      
Total fixed maturity securities available for sale 558,051   644,313      
Mortgage-backed            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 2,773,657   2,430,363      
Available-for-sale, Allowance for Credit Loss (1,140) (562) (158) (885) (23) (18)
Total available for sale, Gross Unrealized Gains 7,643   13,406      
Total available for sale, Gross Unrealized Losses (187,166)   (177,156)      
Total available for sale, Fair Value 2,592,994   2,266,455      
Total fixed maturity securities available for sale 2,592,994   2,266,455      
Asset-backed            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 4,071,678   4,252,883      
Available-for-sale, Allowance for Credit Loss (889) (1,097) (1,164) (1,444) 0 0
Total available for sale, Gross Unrealized Gains 5,279   8,527      
Total available for sale, Gross Unrealized Losses (61,622)   (73,206)      
Total available for sale, Fair Value 4,014,446   4,187,040      
Total fixed maturity securities available for sale 4,014,446   4,187,040      
Industrial            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 4,026,477   3,679,219      
Available-for-sale, Allowance for Credit Loss 0   (40)      
Total available for sale, Gross Unrealized Gains 9,683   24,312      
Total available for sale, Gross Unrealized Losses (142,415)   (143,936)      
Total available for sale, Fair Value 3,893,745   3,559,555      
Total fixed maturity securities available for sale 3,893,745   3,559,555      
Financial            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 3,253,805   2,838,220      
Available-for-sale, Allowance for Credit Loss 0   (4,986)      
Total available for sale, Gross Unrealized Gains 7,899   14,681      
Total available for sale, Gross Unrealized Losses (65,121)   (68,681)      
Total available for sale, Fair Value 3,196,583   2,779,234      
Total fixed maturity securities available for sale 3,196,583   2,779,234      
Utilities            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 735,920   701,865      
Available-for-sale, Allowance for Credit Loss 0   0      
Total available for sale, Gross Unrealized Gains 1,614   6,471      
Total available for sale, Gross Unrealized Losses (25,567)   (23,412)      
Total available for sale, Fair Value 711,967   684,924      
Total fixed maturity securities available for sale 711,967   684,924      
Other            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 616,007   635,975      
Available-for-sale, Allowance for Credit Loss 0   0      
Total available for sale, Gross Unrealized Gains 1,247   1,605      
Total available for sale, Gross Unrealized Losses (7,129)   (7,234)      
Total available for sale, Fair Value 610,125   630,346      
Total fixed maturity securities available for sale 610,125   630,346      
Corporate            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 8,632,209   7,855,279      
Available-for-sale, Allowance for Credit Loss 0 0 (5,026) (8,867) (3,795) (4,701)
Total available for sale, Gross Unrealized Gains 20,443   47,069      
Total available for sale, Gross Unrealized Losses (240,232)   (243,263)      
Total available for sale, Fair Value 8,412,420   7,654,059      
Total fixed maturity securities available for sale 8,412,420   7,654,059      
Foreign government            
Debt Securities, Available-for-sale [Line Items]            
Total available for sale, Amortized Cost 1,867,457   1,817,386      
Available-for-sale, Allowance for Credit Loss (19,469) $ (20,479) (29,603) $ (33,052) $ (33,324) $ (32,633)
Total available for sale, Gross Unrealized Gains 3,306   15,865      
Total available for sale, Gross Unrealized Losses (193,685)   (137,419)      
Total available for sale, Fair Value 1,657,609   1,666,229      
Total fixed maturity securities available for sale $ 1,657,609   $ 1,666,229      
v3.24.2.u1
Investments in Fixed Maturity Securities (HTM Allowance for Credit Loss) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]        
Allowance for expected credit losses, beginning of period $ 38 $ 107 $ 43 $ 114
Cumulative effect adjustment resulting from changes in accounting principles 34 53 34 53
Provision for expected credit losses (4) (54) (9) (61)
Allowance for expected credit losses, end of period $ 34 $ 53 $ 34 $ 53
v3.24.2.u1
Investments in Fixed Maturity Securities (AFS Allowance for Credit Loss) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]        
Allowance for expected credit losses, beginning of period $ 22,831 $ 37,142 $ 36,708 $ 37,352
Expected credit losses on securities for which credit losses were not previously recorded 1,439 2,305 2,001 2,491
Expected credit (gains) losses on securities for which credit losses were previously recorded (1,872) 4,803 (16,311) 4,412
Reduction due to disposals (561) (2) (561) (7)
Allowance for expected credit losses, end of period 21,837 44,248 21,837 44,248
Foreign government        
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]        
Allowance for expected credit losses, beginning of period 20,479 33,324 29,603 32,633
Expected credit losses on securities for which credit losses were not previously recorded 300 0 300 0
Expected credit (gains) losses on securities for which credit losses were previously recorded (1,310) (272) (10,434) 419
Reduction due to disposals 0 0 0 0
Allowance for expected credit losses, end of period 19,469 33,052 19,469 33,052
Corporate        
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]        
Allowance for expected credit losses, beginning of period 0 3,795 5,026 4,701
Expected credit losses on securities for which credit losses were not previously recorded 0 0 0 186
Expected credit (gains) losses on securities for which credit losses were previously recorded 0 5,074 (5,026) 3,987
Reduction due to disposals 0 (2) 0 (7)
Allowance for expected credit losses, end of period 0 8,867 0 8,867
Mortgage-backed        
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]        
Allowance for expected credit losses, beginning of period 562 23 158 18
Expected credit losses on securities for which credit losses were not previously recorded 1,139 861 1,701 861
Expected credit (gains) losses on securities for which credit losses were previously recorded 0 1 (158) 6
Reduction due to disposals (561) 0 (561) 0
Allowance for expected credit losses, end of period 1,140 885 1,140 885
Asset-backed        
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]        
Allowance for expected credit losses, beginning of period 1,097 0 1,164 0
Expected credit losses on securities for which credit losses were not previously recorded 0 1,444 0 1,444
Expected credit (gains) losses on securities for which credit losses were previously recorded (208) 0 (275) 0
Reduction due to disposals 0 0 0 0
Allowance for expected credit losses, end of period 889 $ 1,444 889 $ 1,444
State and municipal        
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]        
Allowance for expected credit losses, beginning of period 693   757  
Expected credit losses on securities for which credit losses were not previously recorded 0   0  
Expected credit (gains) losses on securities for which credit losses were previously recorded (354)   (418)  
Reduction due to disposals 0   0  
Allowance for expected credit losses, end of period $ 339   $ 339  
v3.24.2.u1
Investments in Fixed Maturity Securities (Amortized cost and fair value of fixed maturity securities) (Details) - USD ($)
$ in Thousands
Jun. 30, 2024
Mar. 31, 2024
Dec. 31, 2023
Jun. 30, 2023
Mar. 31, 2023
Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]            
Amortized Cost, Due in one year or less $ 1,943,246          
Amortized Cost, Due after one year through five years 9,983,542          
Amortized Cost, Due after five years through ten years 4,262,692          
Amortized Cost, Due after ten years 2,945,631          
Amortized Cost, Mortgaged-backed securities 2,776,272          
Total investments in fixed maturity securities, Amortized Value 21,911,383          
Fair Value, Due in one year or less 1,884,790          
Fair Value, Due after one year through five years 9,601,275          
Fair Value, Due after five years through ten years 4,152,066          
Fair Value, Due after ten years 2,850,702          
Fair Value, Mortgage-backed securities 2,595,669          
Total investments in fixed maturity securities, Fair Value 21,084,502   $ 20,181,547      
Cumulative effect adjustment resulting from changes in accounting principles $ 34 $ 38 $ 43 $ 53 $ 107 $ 114
v3.24.2.u1
Investments in Equity Securities (Details) - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2024
Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]    
Equity securities $ 1,078,092 $ 1,090,347
Fair Value    
Debt Securities, Available-for-sale [Line Items]    
Cost 977,983 949,332
Gross Unrealized, Gains 158,908 194,881
Gross Unrealized, Losses (58,799) (53,866)
Equity securities 1,078,092 1,090,347
Fair Value | Common stock    
Debt Securities, Available-for-sale [Line Items]    
Cost 603,574 664,997
Gross Unrealized, Gains 139,146 191,806
Gross Unrealized, Losses (46,165) (18,749)
Equity securities 696,555 838,054
Fair Value | Preferred stocks    
Debt Securities, Available-for-sale [Line Items]    
Cost 374,409 284,335
Gross Unrealized, Gains 19,762 3,075
Gross Unrealized, Losses (12,634) (35,117)
Equity securities 381,537 252,293
Carrying Value    
Debt Securities, Available-for-sale [Line Items]    
Equity securities 1,078,092 1,090,347
Carrying Value | Common stock    
Debt Securities, Available-for-sale [Line Items]    
Equity securities 696,555 838,054
Carrying Value | Preferred stocks    
Debt Securities, Available-for-sale [Line Items]    
Equity securities $ 381,537 $ 252,293
v3.24.2.u1
Arbitrage Trading Account (Details) - USD ($)
Jun. 30, 2024
Dec. 31, 2023
Derivative [Line Items]    
Arbitrage trading account $ 1,222,000,000 $ 938,000,000
Long | Options held    
Derivative [Line Items]    
Fair value of derivative 3,000,000  
Notional amount of derivative 401,000,000  
Short | Options held    
Derivative [Line Items]    
Fair value of derivative 81,000,000  
Notional amount of derivative $ 401,000,000  
v3.24.2.u1
Net Investment Income (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Net Investment Income [Line Items]        
Gross investment income $ 374,975 $ 246,812 $ 697,057 $ 472,925
Investment expense (2,846) (1,660) (5,090) (4,374)
Net investment income 372,129 245,152 691,967 468,551
Fixed maturity securities, including cash and cash equivalents and loans receivable        
Net Investment Income [Line Items]        
Gross investment income 324,136 217,830 659,384 413,473
Arbitrage trading account (1)        
Net Investment Income [Line Items]        
Gross investment income 25,476 (1,186) (3,873) 993
Equity securities        
Net Investment Income [Line Items]        
Gross investment income 12,386 15,254 23,721 29,000
Investment funds        
Net Investment Income [Line Items]        
Gross investment income 16,682 17,037 34,693 35,293
Real estate        
Net Investment Income [Line Items]        
Gross investment income $ (3,705) $ (2,123) $ (16,868) $ (5,834)
v3.24.2.u1
Investment Funds (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended 18 Months Ended
Jul. 01, 2022
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2022
Dec. 31, 2023
Schedule of Equity Method Investments [Line Items]              
Unfunded commitments   $ 275,000   $ 275,000      
Investment funds   1,589,119   1,589,119     $ 1,621,655
Income (Loss) from Investment Funds       (3,873) $ 993    
Written premiums ceded   590,993 $ 525,258 1,102,458 999,751    
Fair Value              
Schedule of Equity Method Investments [Line Items]              
Trading account receivables from brokers and clearing organizations   40,705   40,705     303,614
Lifson Re              
Schedule of Equity Method Investments [Line Items]              
Percentage of reinsurance placements of share placed amounts 30.00%         22.50%  
Written premiums ceded       206,000 281,000    
Financial services              
Schedule of Equity Method Investments [Line Items]              
Investment funds   198,111   198,111     201,625
Income (Loss) from Investment Funds       12,880 2,963    
Transportation              
Schedule of Equity Method Investments [Line Items]              
Investment funds   436,057   436,057     433,407
Income (Loss) from Investment Funds       (18,231) (20,321)    
Real Estate              
Schedule of Equity Method Investments [Line Items]              
Investment funds   306,485   306,485     344,278
Income (Loss) from Investment Funds       (3,732) 23,843    
Energy              
Schedule of Equity Method Investments [Line Items]              
Investment funds   131,719   131,719     114,794
Income (Loss) from Investment Funds       8,505 3,439    
Infrastructure              
Schedule of Equity Method Investments [Line Items]              
Investment funds   140,699   140,699     130,589
Income (Loss) from Investment Funds       7,828 5,936    
Other funds              
Schedule of Equity Method Investments [Line Items]              
Investment funds   376,048   376,048     396,962
Income (Loss) from Investment Funds       (11,123) $ (14,867)    
Deferred compensation trust assets   $ 41,000   $ 41,000     $ 36,000
v3.24.2.u1
Real Estate (Details) - USD ($)
$ in Thousands
Jun. 30, 2024
Dec. 31, 2023
Real Estate [Abstract]    
Properties in operation $ 1,051,755 $ 1,022,654
Properties under development 227,551 227,220
Total $ 1,279,306 $ 1,249,874
v3.24.2.u1
Real Estate (Narrative) (Details) - USD ($)
 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Dec. 31, 2023
Real Estate [Abstract]      
Accumulated depreciation and amortization on properties $ 35,389,000   $ 32,745,000
Real estate depreciation expense 4,164,000 $ 4,394,000  
Lease future minimum payments 2021 15,013,195    
Lease future minimum payments 2022 32,278,604    
Lease future minimum payments 2023 33,991,743    
Lease future minimum payments 2024 32,850,623    
Lease future minimum payments 2025 33,376,327    
Lease future minimum payments 2026 31,999,237    
Lease future minimum payments there after $ 416,884,751    
v3.24.2.u1
Loans Receivable (Details) - USD ($)
$ in Thousands
 6 Months Ended
Jun. 30, 2024
Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Loans receivable, Amortized cost $ 349,325 $ 201,271
Loans receivable, Fair value 349,310 198,244
Real estate loans    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Loans receivable, Amortized cost 347,742 200,381
Loans receivable, Fair value 347,727 197,354
Commercial loans    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Loans receivable, Amortized cost 1,583 890
Loans receivable, Fair value $ 1,583 $ 890
Loans receivable maturity term 10 years  
v3.24.2.u1
Loans Receivable - Allowance For Credit Loss (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Financing Receivable, Allowance for Credit Loss [Line Items]        
Allowance for expected credit losses, beginning of period $ 2,609 $ 1,609 $ 3,004 $ 1,791
Change in expected credit losses (796) 2,941 (1,191) 2,759
Allowance for expected credit losses, end of period 1,813 4,550 1,813 4,550
Real estate loans        
Financing Receivable, Allowance for Credit Loss [Line Items]        
Allowance for expected credit losses, beginning of period 2,587 1,039 2,983 1,100
Change in expected credit losses (794) 2,619 (1,190) 2,558
Allowance for expected credit losses, end of period 1,793 3,658 1,793 3,658
Commercial loans        
Financing Receivable, Allowance for Credit Loss [Line Items]        
Allowance for expected credit losses, beginning of period 22 570 21 691
Change in expected credit losses (2) 322 (1) 201
Allowance for expected credit losses, end of period $ 20 $ 892 $ 20 $ 892
v3.24.2.u1
Net Investment (Losses) Gains (Net Investment Gains (Losses)) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Investments, Debt and Equity Securities [Abstract]        
Fixed maturity securities, gains $ 3,092 $ 115 $ 6,649 $ 1,058
Fixed maturity securities, losses (5,362) (3,640) (7,685) (21,770)
Net realized gains on investment sales (2) 61,521 111,072 101,798 112,132
Change in unrealized (losses) gains (66,717) 21,260 (40,905) 64,664
Investment funds 217 (98) 1,210 (88)
Real estate (3) (1,958) (55,449) (4,174) (44,710)
Loans receivable 0 0 0 0
Other (4) (51,099) (4,613) (105,696) (20,028)
Net realized and unrealized (losses) gains on investments in earnings before allowance for expected credit losses (60,306) 68,647 (48,803) 91,258
Fixed maturity securities 998 (7,052) 14,879 (6,835)
Loans receivable 796 (2,941) 1,191 (2,759)
Change in allowance for expected credit losses on investments 1,794 (9,993) 16,070 (9,594)
Net investment (losses) gains (58,512) 58,654 (32,733) 81,664
Income tax benefit $ 12,401 (12,587) $ 5,769 (17,437)
After-tax net investment (losses) gains   $ 46,067   $ 64,227
v3.24.2.u1
Net Investment (Losses) Gains (Change in Unrealized Gains (Losses) of Available For Sales Securities) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Realized and Unrealized Investment Gains Losses [Line Items]        
Total change in unrealized investment (losses) gains $ (20,640) $ (144,043) $ (109,937) $ 87,978
Income tax benefit (expense) 7,302 30,759 26,477 (20,463)
Noncontrolling interests 1 0 1 (1)
Total change in unrealized gains (13,337) (113,284) (83,459) 67,514
Debt securities        
Realized and Unrealized Investment Gains Losses [Line Items]        
Total change in unrealized investment (losses) gains (11,394) (148,021) (99,988) 79,094
Fixed maturity securities with allowance for expected credit losses        
Realized and Unrealized Investment Gains Losses [Line Items]        
Total change in unrealized investment (losses) gains (7,683) 3,694 (6,696) 7,150
Investment funds        
Realized and Unrealized Investment Gains Losses [Line Items]        
Total change in unrealized investment (losses) gains (1,338) 462 (3,041) 2,398
Other        
Realized and Unrealized Investment Gains Losses [Line Items]        
Total change in unrealized investment (losses) gains $ (225) $ (178) $ (212) $ (664)
v3.24.2.u1
Fixed Maturity Securities In An Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) - USD ($)
$ in Thousands
Jun. 30, 2024
Dec. 31, 2023
Debt securities    
Debt Securities, Available-for-sale [Line Items]    
Fair value, Less than 12 months $ 4,890,221 $ 2,420,657
Gross Unrealized Losses, Less than 12 Months 50,371 27,496
Fair Value, 12 Months or Greater 10,083,279 11,043,923
Gross Unrealized Losses, 12 Months or Greater 806,572 783,679
Fair Value, Total 14,973,500 13,464,580
Gross Unrealized Losses, Total 856,943 811,175
U.S. government and government agency    
Debt Securities, Available-for-sale [Line Items]    
Fair value, Less than 12 months 422,945 384,392
Gross Unrealized Losses, Less than 12 Months 3,391 6,655
Fair Value, 12 Months or Greater 795,297 614,623
Gross Unrealized Losses, 12 Months or Greater 51,081 51,014
Fair Value, Total 1,218,242 999,015
Gross Unrealized Losses, Total 54,472 57,669
State and municipal    
Debt Securities, Available-for-sale [Line Items]    
Fair value, Less than 12 months 357,529 264,273
Gross Unrealized Losses, Less than 12 Months 4,935 3,013
Fair Value, 12 Months or Greater 1,758,572 1,680,034
Gross Unrealized Losses, 12 Months or Greater 114,831 119,449
Fair Value, Total 2,116,101 1,944,307
Gross Unrealized Losses, Total 119,766 122,462
Mortgage-backed    
Debt Securities, Available-for-sale [Line Items]    
Fair value, Less than 12 months 530,802 278,819
Gross Unrealized Losses, Less than 12 Months 4,258 2,025
Fair Value, 12 Months or Greater 1,356,573 1,360,748
Gross Unrealized Losses, 12 Months or Greater 182,908 175,131
Fair Value, Total 1,887,375 1,639,567
Gross Unrealized Losses, Total 187,166 177,156
Asset-backed    
Debt Securities, Available-for-sale [Line Items]    
Fair value, Less than 12 months 947,780 413,511
Gross Unrealized Losses, Less than 12 Months 4,434 2,070
Fair Value, 12 Months or Greater 1,079,695 2,176,035
Gross Unrealized Losses, 12 Months or Greater 57,188 71,136
Fair Value, Total 2,027,475 2,589,546
Gross Unrealized Losses, Total 61,622 73,206
Corporate    
Debt Securities, Available-for-sale [Line Items]    
Fair value, Less than 12 months 2,068,015 874,754
Gross Unrealized Losses, Less than 12 Months 17,788 11,975
Fair Value, 12 Months or Greater 4,333,968 4,418,309
Gross Unrealized Losses, 12 Months or Greater 222,444 231,288
Fair Value, Total 6,401,983 5,293,063
Gross Unrealized Losses, Total 240,232 243,263
Foreign government    
Debt Securities, Available-for-sale [Line Items]    
Fair value, Less than 12 months 563,150 204,908
Gross Unrealized Losses, Less than 12 Months 15,565 1,758
Fair Value, 12 Months or Greater 759,174 794,174
Gross Unrealized Losses, 12 Months or Greater 178,120 135,661
Fair Value, Total 1,322,324 999,082
Gross Unrealized Losses, Total $ 193,685 $ 137,419
v3.24.2.u1
Fixed Maturity Securities In An Unrealized Loss Position (Non-Investment Grade Fixed Maturity Securities) (Details) - External Credit Rating, Non Investment Grade
$ in Thousands
Jun. 30, 2024
USD ($)
Foreign government  
Debt Securities, Available-for-sale [Line Items]  
Number of Securities 51
Aggregate Fair Value $ 99,230
Gross Unrealized Loss $ 159,930
State and municipal  
Debt Securities, Available-for-sale [Line Items]  
Number of Securities 5
Aggregate Fair Value $ 24,865
Gross Unrealized Loss $ 4,838
Corporate  
Debt Securities, Available-for-sale [Line Items]  
Number of Securities 30
Aggregate Fair Value $ 42,131
Gross Unrealized Loss $ 2,651
Mortgage-backed  
Debt Securities, Available-for-sale [Line Items]  
Number of Securities 16
Aggregate Fair Value $ 4,107
Gross Unrealized Loss $ 201
Special revenue  
Debt Securities, Available-for-sale [Line Items]  
Number of Securities 102
Aggregate Fair Value $ 170,333
Gross Unrealized Loss $ 167,620
v3.24.2.u1
Fair Value Measurements (Assets and Liabilities Measured At Fair Value, On a Recurring Basis) (Details) - USD ($)
$ in Thousands
Jun. 30, 2024
Dec. 31, 2023
Assets:    
Total fixed maturity securities available for sale $ 21,039,112 $ 20,124,936
Equity securities 1,078,092 1,090,347
Arbitrage trading account 1,222,000 938,000
Fair Value, Measurements, Recurring    
Assets:    
Total fixed maturity securities available for sale 21,039,112 20,124,936
Equity securities 1,078,092 1,090,347
Arbitrage trading account 1,221,861 938,049
Total 23,339,065 22,153,332
Liabilities:    
Trading account securities sold but not yet purchased 81,273 9,357
Fair Value, Measurements, Recurring | U.S. government and government agency    
Assets:    
Total fixed maturity securities available for sale 1,822,376 1,716,731
Fair Value, Measurements, Recurring | State and municipal    
Assets:    
Total fixed maturity securities available for sale 2,539,267 2,634,422
Fair Value, Measurements, Recurring | Mortgage-backed    
Assets:    
Total fixed maturity securities available for sale 2,592,994 2,266,455
Fair Value, Measurements, Recurring | Asset-backed    
Assets:    
Total fixed maturity securities available for sale 4,014,446 4,187,040
Fair Value, Measurements, Recurring | Corporate    
Assets:    
Total fixed maturity securities available for sale 8,412,420 7,654,059
Fair Value, Measurements, Recurring | Foreign government    
Assets:    
Total fixed maturity securities available for sale 1,657,609 1,666,229
Fair Value, Measurements, Recurring | Common stocks    
Assets:    
Equity securities 696,555 838,054
Fair Value, Measurements, Recurring | Preferred stocks    
Assets:    
Equity securities 381,537 252,293
Level 1 | Fair Value, Measurements, Recurring    
Assets:    
Total fixed maturity securities available for sale 0 0
Equity securities 693,294 835,338
Arbitrage trading account 1,061,891 546,110
Total 1,755,185 1,381,448
Liabilities:    
Trading account securities sold but not yet purchased 81,273 9,357
Level 1 | Fair Value, Measurements, Recurring | U.S. government and government agency    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 1 | Fair Value, Measurements, Recurring | State and municipal    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 1 | Fair Value, Measurements, Recurring | Mortgage-backed    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 1 | Fair Value, Measurements, Recurring | Asset-backed    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 1 | Fair Value, Measurements, Recurring | Corporate    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 1 | Fair Value, Measurements, Recurring | Foreign government    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 1 | Fair Value, Measurements, Recurring | Common stocks    
Assets:    
Equity securities 693,294 835,338
Level 1 | Fair Value, Measurements, Recurring | Preferred stocks    
Assets:    
Equity securities 0 0
Level 2 | Fair Value, Measurements, Recurring    
Assets:    
Total fixed maturity securities available for sale 21,039,112 20,124,936
Equity securities 379,017 249,756
Arbitrage trading account 156,377 388,167
Total 21,574,506 20,762,859
Liabilities:    
Trading account securities sold but not yet purchased 0 0
Level 2 | Fair Value, Measurements, Recurring | U.S. government and government agency    
Assets:    
Total fixed maturity securities available for sale 1,822,376 1,716,731
Level 2 | Fair Value, Measurements, Recurring | State and municipal    
Assets:    
Total fixed maturity securities available for sale 2,539,267 2,634,422
Level 2 | Fair Value, Measurements, Recurring | Mortgage-backed    
Assets:    
Total fixed maturity securities available for sale 2,592,994 2,266,455
Level 2 | Fair Value, Measurements, Recurring | Asset-backed    
Assets:    
Total fixed maturity securities available for sale 4,014,446 4,187,040
Level 2 | Fair Value, Measurements, Recurring | Corporate    
Assets:    
Total fixed maturity securities available for sale 8,412,420 7,654,059
Level 2 | Fair Value, Measurements, Recurring | Foreign government    
Assets:    
Total fixed maturity securities available for sale 1,657,609 1,666,229
Level 2 | Fair Value, Measurements, Recurring | Common stocks    
Assets:    
Equity securities 1,116 1,158
Level 2 | Fair Value, Measurements, Recurring | Preferred stocks    
Assets:    
Equity securities 377,901 248,598
Level 3 | Fair Value, Measurements, Recurring    
Assets:    
Total fixed maturity securities available for sale 0 0
Equity securities 5,781 5,253
Arbitrage trading account 3,593 3,772
Total 9,374 9,025
Liabilities:    
Trading account securities sold but not yet purchased 0 0
Level 3 | Fair Value, Measurements, Recurring | U.S. government and government agency    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 3 | Fair Value, Measurements, Recurring | State and municipal    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 3 | Fair Value, Measurements, Recurring | Mortgage-backed    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 3 | Fair Value, Measurements, Recurring | Asset-backed    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 3 | Fair Value, Measurements, Recurring | Corporate    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 3 | Fair Value, Measurements, Recurring | Foreign government    
Assets:    
Total fixed maturity securities available for sale 0 0
Level 3 | Fair Value, Measurements, Recurring | Common stocks    
Assets:    
Equity securities 2,145 1,558
Level 3 | Fair Value, Measurements, Recurring | Preferred stocks    
Assets:    
Equity securities $ 3,636 $ 3,695
v3.24.2.u1
Fair Value Measurements (Summarize Changes in Level 3 Assets) (Details) - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2024
Dec. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Assets, Impairments   $ (7,601)
Level 3    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Assets, beginning balance $ 9,025 17,488
Assets, earnings 535 (927)
Assets, other comprehensive income 0 0
Assets, Impairments 0  
Assets, purchases 0 0
Assets, (sales) (223) 0
Assets, maturities 0 0
Assets. transfers out 37 65
Assets, ending balance 9,374 9,025
Level 3 | Equity securities    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Assets, beginning balance 5,253 13,898
Assets, earnings 713 (1,044)
Assets, other comprehensive income 0 0
Assets, Impairments 0 (7,601)
Assets, purchases 0 0
Assets, (sales) (185) 0
Assets, maturities 0 0
Assets. transfers out 0 0
Assets, ending balance 5,781 5,253
Level 3 | Common stock    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Assets, beginning balance 1,558 2,599
Assets, earnings 715 (1,041)
Assets, other comprehensive income 0 0
Assets, Impairments 0 0
Assets, purchases 0 0
Assets, (sales) (128) 0
Assets, maturities 0 0
Assets. transfers out 0 0
Assets, ending balance 2,145 1,558
Level 3 | Preferred stocks    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Assets, beginning balance 3,695 11,299
Assets, earnings (2) (3)
Assets, other comprehensive income 0 0
Assets, Impairments 0 (7,601)
Assets, purchases 0 0
Assets, (sales) (57) 0
Assets, maturities 0 0
Assets. transfers out 0 0
Assets, ending balance 3,636 3,695
Level 3 | Arbitrage trading account    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Assets, beginning balance 3,772 3,590
Assets, earnings (178) 117
Assets, other comprehensive income 0 0
Assets, Impairments 0 0
Assets, purchases 0 0
Assets, (sales) (38) 0
Assets, maturities 0 0
Assets. transfers out 37 65
Assets, ending balance $ 3,593 $ 3,772
v3.24.2.u1
Reserves for Loss and Loss Expenses (Details) - USD ($)
$ in Thousands
 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Dec. 31, 2023
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]      
Net reserves at beginning of period $ 15,661,820 $ 14,248,879  
Net provision for losses and loss expenses:      
Claims occurring during the current year 3,411,888 3,064,046  
Decrease in estimates for claims occurring in prior years 14,700 28,853  
Loss reserve discount accretion 17,786 15,510  
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims 3,444,374 3,108,409  
Net payments for claims:      
Current year 383,639 375,365  
Prior years 2,205,566 2,019,371  
Total 2,589,205 2,394,736  
Foreign currency translation (56,143) 5,929  
Net reserves at end of period 16,460,846 14,968,481 $ 15,661,820
Ceded reserves at end of period 3,106,344 2,951,515  
Gross reserves at end of period $ 19,567,190 $ 17,919,996 $ 18,739,652
v3.24.2.u1
Reserves for Loss and Loss Expenses (Narrative) (Details) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 30, 2023
Mar. 31, 2023
Jun. 30, 2024
Jun. 30, 2023
Liability for Claims and Claims Adjustment Expense [Line Items]        
Net of loss reserves discount $ 22,000,000   $ 26,000,000 $ 22,000,000
Increase (decrease) in estimates for claims     7,000,000 (6,000,000)
Adjustment expense   $ 24,000,000 2,000,000 21,000,000
Liability recognized for best estimate net of reinsurance     388,000,000  
Liability recognized for best estimate net of reinsurance, reported losses     385,000,000  
Liability recognized for best estimate net of reinsurance, incurred but not reported (IBNR)     3,000,000  
Insurance        
Liability for Claims and Claims Adjustment Expense [Line Items]        
Liability recognized for best estimate net of reinsurance     329,000,000  
Unfavorable reserve development net of premium offsets     5,000,000 19,000,000
Reinsurance & Monoline Excess        
Liability for Claims and Claims Adjustment Expense [Line Items]        
Liability recognized for best estimate net of reinsurance     59,000,000  
Unfavorable reserve development net of premium offsets       $ 2,000,000
Favorable reserve development net of premium offsets $ 3,000,000   $ 7,000,000  
v3.24.2.u1
Fair Value of Financial Instruments (Carrying Amounts and Estimated Fair Values of Financial Instruments) (Details) - USD ($)
$ in Thousands
Jun. 30, 2024
Dec. 31, 2023
Assets:    
Equity securities $ 1,078,092 $ 1,090,347
Arbitrage trading account 1,222,000 938,000
Carrying Value    
Assets:    
Fixed maturity securities 21,082,676 20,178,308
Equity securities 1,078,092 1,090,347
Arbitrage trading account 1,221,861 938,049
Loans receivable 349,325 201,271
Cash and cash equivalents 1,580,270 1,363,195
Trading account receivables from brokers and clearing organizations 40,705 303,614
Due from broker 0 36,747
Liabilities:    
Due to broker 128,563 0
Trading account securities sold but not yet purchased 81,273 9,357
Senior notes and other debt 1,828,422 1,827,951
Subordinated debentures 1,009,449 1,009,090
Fair Value    
Assets:    
Fixed maturity securities 21,084,502 20,181,547
Equity securities 1,078,092 1,090,347
Arbitrage trading account 1,221,861 938,049
Loans receivable 349,310 198,244
Cash and cash equivalents 1,580,270 1,363,195
Trading account receivables from brokers and clearing organizations 40,705 303,614
Due from broker 0 36,747
Liabilities:    
Due to broker 128,563 0
Trading account securities sold but not yet purchased 81,273 9,357
Senior notes and other debt 1,422,506 1,480,076
Subordinated debentures $ 825,344 $ 929,598
v3.24.2.u1
Premiums and Reinsurance Related Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Written premiums:        
Written premiums, direct $ 3,380,470 $ 2,985,563 $ 6,419,537 $ 5,724,317
Written premiums, assumed 337,302 351,210 660,991 661,773
Written premiums, ceded (590,993) (525,258) (1,102,458) (999,751)
Total net premiums written 3,126,779 2,811,515 5,978,070 5,386,339
Earned premiums:        
Earned premiums, direct 3,048,872 2,725,650 5,985,516 5,392,712
Earned premiums, assumed 328,114 302,431 666,024 597,661
Earned premiums, ceded (530,571) (475,354) (1,040,778) (946,214)
Net premiums earned 2,846,415 2,552,727 5,610,762 5,044,159
Ceded losses and loss expenses incurred 327,243 333,795 633,194 649,271
Ceded commissions earned $ 123,647 $ 117,523 $ 244,701 $ 235,941
v3.24.2.u1
Premiums and Reinsurance Related Information - Premiums and Reinsurance, Allowance For Credit Loss (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Premium Receivable, Allowance for Credit Loss [Roll Forward]        
Allowance for expected credit losses, beginning of period $ 35,039 $ 32,353 $ 35,110 $ 30,660
Cumulative effect adjustment resulting from changes in accounting principles 37,279 32,770 37,279 32,770
Change in expected credit losses 2,240 417 2,169 2,110
Allowance for expected credit losses, end of period 37,279 32,770 37,279 32,770
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]        
Allowance for expected credit losses, beginning of period 9,185 8,703 8,404 8,064
Cumulative effect adjustment resulting from changes in accounting principles 10,255 9,365 10,255 9,365
Reinsurance Recoverable, Credit Loss Expense (Reversal) 1,070 662 1,851 1,301
Allowance for expected credit losses, end of period $ 10,255 $ 9,365 $ 10,255 $ 9,365
v3.24.2.u1
Restricted Stock Units (Summary of Restricted Stock Units Issued) (Details) - USD ($)
$ in Thousands
 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Share-Based Compensation Arrangement by Share-based Payment Award [Line Item]    
Share based compensation expense $ 25,000 $ 23,000
Restricted stock    
Share-Based Compensation Arrangement by Share-based Payment Award [Line Item]    
Restricted stock units (in units) 2,277 8,381
Fair Value $ 125 $ 332
Minimum | Restricted stock    
Share-Based Compensation Arrangement by Share-based Payment Award [Line Item]    
Award vesting period 3 years  
Maximum | Restricted stock    
Share-Based Compensation Arrangement by Share-based Payment Award [Line Item]    
Award vesting period 5 years  
v3.24.2.u1
Leases (Lease Cost) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Leases [Abstract]        
Lease cost $ 11,326 $ 10,138 $ 22,403 $ 20,326
Cash paid for amounts included in the measurement of lease liabilities reported in operating cash flows 12,364 11,281 24,596 21,844
Right-of-use assets obtained in exchange for new lease liabilities $ 8,853 $ 2,633 $ 33,548 $ 7,946
v3.24.2.u1
Leases (Supplemental Balance Sheet Information) (Details) - USD ($)
$ in Thousands
Jun. 30, 2024
Jun. 30, 2023
Leases [Abstract]    
Operating lease, right-of-use asset $ 190,207 $ 157,991
Operating lease, liability $ 231,128 $ 191,576
Weighted-average remaining lease term 7 years 6 months 7 years
Weighted-average discount rate 5.51% 4.49%
v3.24.2.u1
Leases (Maturities of Operating Lease Liabilities) (Details) - USD ($)
$ in Thousands
Jun. 30, 2024
Jun. 30, 2023
Leases [Abstract]    
2024 $ 26,008  
2025 45,629  
2026 39,117  
2027 30,117  
2028 28,576  
Thereafter 107,255  
Total undiscounted future minimum lease payments 276,702  
Less: Discount impact 45,574  
Total lease liability $ 231,128 $ 191,576
v3.24.2.u1
Business Segments (Financial Information of Company Operating Segments) (Details)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
USD ($)
Jun. 30, 2023
USD ($)
Jun. 30, 2024
USD ($)
segment
Jun. 30, 2023
USD ($)
Segment Reporting [Abstract]        
Number of reportable segments | segment     2  
Segment Reporting Information [Line Items]        
Earned Premiums (1) $ 2,846,415 $ 2,552,727 $ 5,610,762 $ 5,044,159
Investment Income  372,129 245,152 691,967 468,551
Other 95,488 198,035 268,076 378,208
Total revenues 3,314,032 2,995,914 6,570,805 5,890,918
Pre-Tax Income (Loss) 487,673 457,184 1,061,744 833,256
Net Income (Loss) to Common Stockholders 371,909 356,308 814,380 650,434
Net investment gains (58,512) 58,654 (32,733) 81,664
Net investment gains, net of tax (46,111) 46,067 (26,964) 64,227
Corporate, other and eliminations        
Segment Reporting Information [Line Items]        
Earned Premiums (1) 0 0 0 0
Investment Income  10,096 17,638 31,946 22,895
Other 144,409 130,528 281,795 278,117
Total revenues 154,505 148,166 313,741 301,012
Pre-Tax Income (Loss) (68,317) (93,240) (125,799) (194,089)
Net Income (Loss) to Common Stockholders (53,865) (72,315) (97,757) (152,814)
Insurance        
Segment Reporting Information [Line Items]        
Earned Premiums (1)   2,215,186   4,358,110
Insurance | Operating Segments        
Segment Reporting Information [Line Items]        
Earned Premiums (1) 2,484,569 2,215,186 4,883,338 4,358,110
Investment Income  303,561 185,327 548,338 348,886
Other 9,591 8,853 19,014 18,427
Total revenues 2,797,721 2,409,366 5,450,690 4,725,423
Pre-Tax Income (Loss) 490,053 386,350 968,202 738,977
Net Income (Loss) to Common Stockholders 374,247 300,239 739,337 574,347
Insurance | Operating Segments | Non-US        
Segment Reporting Information [Line Items]        
Total revenues 368,000 280,000 762,000 554,000
Reinsurance & Monoline Excess        
Segment Reporting Information [Line Items]        
Earned Premiums (1)   337,541   686,049
Reinsurance & Monoline Excess | Operating Segments        
Segment Reporting Information [Line Items]        
Earned Premiums (1) 361,846 337,541 727,424 686,049
Investment Income  58,472 42,187 111,683 96,770
Other 0 0 0 0
Total revenues 420,318 379,728 839,107 782,819
Pre-Tax Income (Loss) 124,449 105,420 252,074 206,704
Net Income (Loss) to Common Stockholders 97,638 82,317 199,764 164,674
Reinsurance & Monoline Excess | Operating Segments | Non-US        
Segment Reporting Information [Line Items]        
Total revenues 117,000 102,000 228,000 209,000
Net investment gains        
Segment Reporting Information [Line Items]        
Earned Premiums (1) 0 0 0 0
Investment Income  $ 0 $ 0 $ 0 $ 0
v3.24.2.u1
Business Segments (Identifiable Assets by Segment) (Details) - USD ($)
$ in Thousands
Jun. 30, 2024
Dec. 31, 2023
Segment Reporting, Asset Reconciling Item [Line Items]    
Consolidated Assets $ 38,909,919 $ 37,111,830
Operating Segments | Insurance    
Segment Reporting, Asset Reconciling Item [Line Items]    
Consolidated Assets 31,264,338 29,923,282
Operating Segments | Reinsurance & Monoline Excess    
Segment Reporting, Asset Reconciling Item [Line Items]    
Consolidated Assets 5,557,232 5,545,249
Corporate Reconciling Items And Eliminations    
Segment Reporting, Asset Reconciling Item [Line Items]    
Consolidated Assets $ 2,088,349 $ 1,643,299
v3.24.2.u1
Business Segments (Net Premiums Earned By Major Line of Business) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Revenue from External Customer [Line Items]        
Net premiums earned $ 2,846,415 $ 2,552,727 $ 5,610,762 $ 5,044,159
Insurance        
Revenue from External Customer [Line Items]        
Net premiums earned   2,215,186   4,358,110
Insurance | Operating Segments        
Revenue from External Customer [Line Items]        
Net premiums earned 2,484,569 2,215,186 4,883,338 4,358,110
Insurance | Other liability        
Revenue from External Customer [Line Items]        
Net premiums earned 1,001,987 890,984 1,969,247 1,744,456
Insurance | Short-tail lines        
Revenue from External Customer [Line Items]        
Net premiums earned 538,797 444,834 1,049,606 857,368
Insurance | Auto        
Revenue from External Customer [Line Items]        
Net premiums earned 361,580 307,578 715,593 601,694
Insurance | Workers' compensation        
Revenue from External Customer [Line Items]        
Net premiums earned 310,564 299,149 612,060 604,710
Insurance | Professional liability        
Revenue from External Customer [Line Items]        
Net premiums earned 271,641 272,641 536,832 549,882
Reinsurance & Monoline Excess        
Revenue from External Customer [Line Items]        
Net premiums earned   337,541   686,049
Reinsurance & Monoline Excess | Operating Segments        
Revenue from External Customer [Line Items]        
Net premiums earned 361,846 337,541 727,424 686,049
Reinsurance & Monoline Excess | Casualty        
Revenue from External Customer [Line Items]        
Net premiums earned 199,080 202,348 396,924 417,060
Reinsurance & Monoline Excess | Property        
Revenue from External Customer [Line Items]        
Net premiums earned 97,255 76,348 199,638 151,500
Reinsurance & Monoline Excess | Monoline excess        
Revenue from External Customer [Line Items]        
Net premiums earned $ 65,511 $ 58,845 $ 130,862 $ 117,489