PROGRESSIVE CORP/OH/, 10-Q filed on 5/6/2024
Quarterly Report
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Document and Entity Information
3 Months Ended
Mar. 31, 2024
shares
Cover [Abstract]  
Document Type 10-Q
Document Quarterly Report true
Document Period End Date Mar. 31, 2024
Document Transition Report false
Entity File Number 001-09518
Entity Incorporation, State or Country Code OH
Entity Tax Identification Number 34-0963169
Entity Address, Address Line One 6300 Wilson Mills Road,
Entity Address, City or Town Mayfield Village,
Entity Address, State or Province OH
Entity Address, Postal Zip Code 44143
City Area Code 440
Local Phone Number 461-5000
Entity Information, Former Legal or Registered Name Not Applicable
Title of 12(b) Security Common Shares, $1.00 Par Value
Trading Symbol PGR
Security Exchange Name NYSE
Entity Current Reporting Status Yes
Entity Interactive Data Current Yes
Entity Filer Category Large Accelerated Filer
Entity Small Business false
Entity Emerging Growth Company false
Entity Shell Company false
Entity Common Stock, Shares Outstanding 585,698,387
Entity Registrant Name PROGRESSIVE CORP/OH/
Entity Central Index Key 0000080661
Current Fiscal Year End Date --12-31
Document Fiscal Year Focus 2024
Document Fiscal Period Focus Q1
Amendment Flag false
v3.24.1.u1
Consolidated Statements of Comprehensive Income - USD ($)
shares in Millions, $ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Revenues    
Net premiums earned $ 16,148.6 $ 13,533.1
Investment income 617.6 419.6
Net realized gains (losses) on securities:    
Net realized gains (losses) on security sales (146.5) (30.3)
Net holding period gains (losses) on securities 302.1 104.4
Net impairment losses recognized in earnings 0.0 (2.3)
Total net realized gains (losses) on securities 155.6 71.8
Fees and other revenues 236.5 206.2
Service revenues 84.2 72.5
Total revenues 17,242.5 14,303.2
Expenses    
Losses and loss adjustment expenses 10,971.6 10,624.0
Policy acquisition costs 1,232.2 1,115.8
Other underwriting expenses 1,931.4 1,857.9
Investment expenses 5.7 5.5
Service expenses 92.1 82.3
Interest expense 69.6 63.3
Total expenses 14,302.6 13,748.8
Net Income    
Income before income taxes 2,939.9 554.4
Provision for income taxes 608.5 106.5
Net income 2,331.4 447.9
Other Comprehensive Income (Loss)    
Total net unrealized gains (losses) on fixed-maturity securities (207.8) 603.2
Net unrealized losses on forecasted transactions 0.1 0.1
Foreign currency translation adjustment (0.2) 0.0
Other comprehensive income (loss) (207.9) 603.3
Comprehensive income (loss) 2,123.5 1,051.2
Computation of Earnings Per Common Share    
Net income 2,331.4 447.9
Less: Preferred share dividends and other [1] 17.0 7.3
Net income available to common shareholders $ 2,314.4 $ 440.6
Average common shares outstanding - Basic (in shares) 585.4 584.9
Net effect of dilutive stock-based compensation (in shares) 1.9 2.1
Total average equivalent common shares - Diluted (in shares) 587.3 587.0
Basic: Earnings per common shares (in dollars per share) $ 3.95 $ 0.75
Diluted: Earnings per common share (in dollars per share) $ 3.94 $ 0.75
[1] All of our outstanding Serial Preferred Shares, Series B, were redeemed in February 2024. See Note 9 – Dividends for further discussion.
v3.24.1.u1
Consolidated Balance Sheets - USD ($)
$ in Millions
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2023
Assets      
Fixed maturities (amortized cost: $65,949.3, $53,123.9, and $62,441.9) $ 63,629.7 $ 60,378.2 $ 50,289.2
Short-term investments (amortized cost: $1,326.7, $2,524.1, and $1,789.9) 1,326.7 1,789.9 2,524.1
Total available-for-sale securities 64,956.4 62,168.1 52,813.3
Nonredeemable preferred stocks (cost: $931.1, $1,197.7, and $977.1) 886.7 902.1 1,078.8
Common equities (cost: $708.2, $740.5, and $706.0) 3,194.9 2,928.4 2,794.3
Total equity securities 4,081.6 3,830.5 3,873.1
Total investments 69,038.0 65,998.6 56,686.4
Cash and cash equivalents 154.5 84.9 273.7
Restricted cash and cash equivalents 13.4 14.7 14.9
Total cash, cash equivalents, restricted cash, and restricted cash equivalents 167.9 99.6 288.6
Accrued investment income 464.2 438.0 299.5
Premiums receivable, net of allowance for credit losses of $327.7, $340.9, and $369.1 14,192.5 11,958.2 12,411.4
Reinsurance recoverables 5,003.4 5,093.9 5,616.2
Prepaid reinsurance premiums 209.8 249.8 269.6
Deferred acquisition costs 1,818.2 1,687.4 1,626.8
Property and equipment, net of accumulated depreciation of $1,580.2, $1,576.2, and $1,655.1 756.3 880.8 949.0
Net federal deferred income taxes 1,031.8 936.0 1,057.0
Other assets 1,445.8 1,348.5 1,202.6
Total assets 94,127.9 88,690.8 80,407.1
Liabilities      
Unearned premiums 22,907.3 20,133.7 19,844.3
Loss and loss adjustment expense reserves 34,831.0 34,389.2 31,026.4
Accounts payable, accrued expenses, and other liabilities 7,688.6 7,002.2 6,278.7
Debt [1] 6,889.7 6,888.6 6,389.3
Total liabilities 72,316.6 68,413.7 63,538.7
Shareholders' Equity      
Serial Preferred Shares, Series B, no par value (cumulative, liquidation preference $1,000 per share) (authorized, issued, and outstanding of $0, $0.5, and $0.5) 0.0 493.9 493.9
Common shares, $1.00 par value (authorized 900.0; issued 797.6, including treasury shares of 211.9, 212.2, and 212.3) 585.7 585.3 585.4
Paid-in capital 2,028.7 2,013.1 1,907.7
Retained earnings 21,020.5 18,800.5 16,080.1
Accumulated other comprehensive income (loss):      
Net unrealized gains (losses) on fixed-maturity securities (1,808.6) (1,600.8) (2,183.1)
Net unrealized losses on forecasted transactions (13.9) (14.0) (14.4)
Foreign currency translation adjustment (1.1) (0.9) (1.2)
Total accumulated other comprehensive income (loss) (1,823.6) (1,615.7) (2,198.7)
Total shareholders’ equity 21,811.3 20,277.1 16,868.4
Total liabilities and shareholders’ equity $ 94,127.9 $ 88,690.8 $ 80,407.1
[1] Consists of long-term debt. See Note 4 – Debt for further discussion.
v3.24.1.u1
Consolidated Balance Sheets (Parenthetical) - USD ($)
$ in Millions
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2023
Common shares, par value (USD per share) $ 1.00 $ 1.00 $ 1.00
Common shares, authorized (shares) 900,000,000.0 900,000,000.0 900,000,000.0
Common shares, issued (shares) 797,600,000 797,600,000 797,600,000
Treasury shares 211,900,000 212,300,000 212,200,000
Fixed maturities, amortized cost $ 65,949.3 $ 62,441.9 $ 53,123.9
Short-term investments, amortized cost 1,326.7 1,789.9 2,524.1
Nonredeemable preferred stocks, cost 931.1 977.1 1,197.7
Common equities, cost 708.2 706.0 740.5
Premium receivable, allowance for credit loss 327.7 369.1 340.9
Property and equipment, accumulated depreciation $ 1,580.2 $ 1,655.1 $ 1,576.2
Serial Preferred Stock      
Preferred stock, shares authorized (shares) 20,000,000.0 20,000,000.0 20,000,000.0
Series B Preferred Stock      
Preferred stock, liquidation preference per share (USD per share) $ 1,000    
Series B Preferred Stock | Serial Preferred Stock      
Preferred stock, shares authorized (shares) 0 500,000 500,000
Preferred stock, no par value   $ 0 $ 0
Preferred stock, liquidation preference per share (USD per share)   $ 1,000 $ 1,000
Preferred stock, shares issued (shares) 0 500,000 500,000
Preferred stock, shares outstanding (shares) 0 500,000 500,000
v3.24.1.u1
Consolidated Statements of Changes in Shareholders' Equity - USD ($)
$ in Millions
Total
Serial Preferred Stock
Preferred Shares, No Par Value
Common Shares, $1.00 Par Value
Paid-In Capital
Retained Earnings
Accumulated Other Comprehensive Income (Loss)
Series B Preferred Stock
Serial Preferred Stock
Voting Preference Shares
Cash dividends declared on common stock (in dollars per share) $ 0.10                
Cash dividends declared on Serial Preferred Shares, Series B (in dollars per share)               $ 0  
Balance, Beginning of period at Dec. 31, 2022     $ 493.9 $ 584.9 $ 1,893.0 $ 15,721.2 $ (2,802.0)    
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Redemption of Serial Preferred Shares, Series B [1]     0.0            
Net income $ 447.9         447.9      
Treasury shares purchased       (0.2) (0.8) (31.7)      
Cash dividends declared on common shares ($0.10 and $0.10 per share) [1]           (58.5)      
Cash dividends declared on Serial Preferred Shares, Series B ($15.688377 and $0 per share) [1]           0.0      
Net restricted equity awards issued/vested       0.7 (0.7)        
Amortization of equity-based compensation         15.9        
Reinvested dividends on restricted stock units         0.3 (0.3)      
Other, net           1.5      
Other comprehensive income (loss) 603.3           603.3    
Balance, End of period at Mar. 31, 2023 $ 16,868.4   493.9 585.4 1,907.7 16,080.1 (2,198.7)    
Preferred stock, no par value               $ 0  
Common shares, par value (USD per share) $ 1.00                
Preferred stock, shares authorized (shares)   20,000,000.0           500,000 5,000,000.0
Preferred stock, shares issued (shares)               500,000 0
Preferred stock, no par value               $ 0  
Common shares, par value (USD per share) 1.00                
Preferred stock, shares authorized (shares)   20,000,000.0           500,000  
Preferred stock, shares issued (shares)               500,000  
Cash dividends declared on common stock (in dollars per share) $ 0.10                
Cash dividends declared on Serial Preferred Shares, Series B (in dollars per share)               $ 15.688377  
Balance, Beginning of period at Dec. 31, 2023 $ 20,277.1   493.9 585.3 2,013.1 18,800.5 (1,615.7)    
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Redemption of Serial Preferred Shares, Series B [1]     (493.9)            
Net income 2,331.4         2,331.4      
Treasury shares purchased       (0.2) (0.8) (36.1)      
Cash dividends declared on common shares ($0.10 and $0.10 per share) [1]           (58.5)      
Cash dividends declared on Serial Preferred Shares, Series B ($15.688377 and $0 per share) [1]           (7.8)      
Net restricted equity awards issued/vested       0.6 (0.6)        
Amortization of equity-based compensation         16.8        
Reinvested dividends on restricted stock units         0.2 (0.2)      
Other, net           (8.8)      
Other comprehensive income (loss) (207.9)           (207.9)    
Balance, End of period at Mar. 31, 2024 $ 21,811.3   $ 0.0 $ 585.7 $ 2,028.7 $ 21,020.5 $ (1,823.6)    
Common shares, par value (USD per share) $ 1.00                
Preferred stock, shares authorized (shares)   20,000,000.0           0 5,000,000.0
Preferred stock, shares issued (shares)               0 0
[1] See Note 9 – Dividends for further discussion.
v3.24.1.u1
Consolidated Statements of Cash Flows - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Cash Flows From Operating Activities    
Net income $ 2,331.4 $ 447.9
Adjustments to reconcile net income to net cash provided by operating activities:    
Depreciation 69.7 68.0
Net amortization (accretion) of fixed-income securities (7.5) (5.0)
Amortization of equity-based compensation 16.8 15.9
Net realized (gains) losses on securities (155.6) (71.8)
Net (gains) losses on disposition of property and equipment (1.7) 16.5
Changes in:    
Premiums receivable (2,234.3) (1,994.5)
Reinsurance recoverables 90.5 215.9
Prepaid reinsurance premiums 40.0 25.9
Deferred acquisition costs (130.8) (82.4)
Income taxes 609.5 106.6
Unearned premiums 2,773.6 2,550.7
Loss and loss adjustment expense reserves 441.8 667.1
Accounts payable, accrued expenses, and other liabilities 457.8 565.5
Other, net (65.8) (76.8)
Net cash provided by operating activities 4,235.4 2,449.5
Purchases:    
Fixed maturities (13,288.2) (6,119.5)
Equity securities (32.4) (17.8)
Sales:    
Fixed maturities 7,765.3 2,202.6
Equity securities 58.2 277.3
Maturities, paydowns, calls, and other:    
Fixed maturities 1,855.2 976.0
Equity securities 23.3 25.1
Net (purchases) sales of short-term investments 479.2 360.8
Net change in unsettled security transactions 61.8 57.2
Purchases of property and equipment (50.2) (43.2)
Sales of property and equipment 3.5 4.3
Net cash used in investing activities (3,124.3) (2,277.2)
Cash Flows From Financing Activities    
Redemption of Serial Preferred Shares, Series B (500.0) 0.0
Dividends paid to common shareholders (497.9) (58.5)
Dividends paid to preferred shareholders (7.8) (13.4)
Acquisition of treasury shares for restricted stock tax liabilities (37.1) (32.7)
Net cash used in financing activities (1,042.8) (104.6)
Increase in cash, cash equivalents, restricted cash, and restricted cash equivalents 68.3 67.7
Cash, cash equivalents, restricted cash, and restricted cash equivalents – January 1 99.6 220.9
Cash, cash equivalents, restricted cash, and restricted cash equivalents – March 31 $ 167.9 $ 288.6
v3.24.1.u1
Basis of Presentation
3 Months Ended
Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Basis of Reporting and Accounting BASIS OF REPORTING AND ACCOUNTING
The accompanying consolidated financial statements include the accounts of The Progressive Corporation and our wholly owned insurance subsidiaries and non-insurance subsidiaries and affiliates in which we have a controlling financial interest (Progressive).
The consolidated financial statements reflect all normal recurring adjustments that, in the opinion of management, were necessary for a fair statement of the results for the interim periods presented. The results of operations for the period ended March 31, 2024, are not necessarily indicative of the results expected for the full year. These consolidated financial statements and the notes thereto should be read in conjunction with Progressive’s audited financial statements and accompanying notes included in Exhibit 13 to our Annual Report on Form 10-K for the year ended December 31, 2023 (2023 Annual Report to Shareholders).
Premiums Receivable
We perform analyses to evaluate our premiums receivable for expected credit losses. See our 2023 Annual Report to Shareholders for a discussion on our premiums receivable allowance for credit loss policy. The following table summarizes changes in our allowance for credit loss exposure on our premiums receivable:
Three Months Ended March 31,
(millions)20242023
Allowance for credit losses, beginning of period$369.1 $343.3 
Increase in allowance1
106.8 116.9 
Write-offs2
(148.2)(119.3)
Allowance for credit losses, end of period$327.7 $340.9 
1 Represents the incremental increase in other underwriting expenses.
2 Represents the portion of allowance that is reversed when the premiums receivable is written off. Premiums receivable balances are written off once we have exhausted our collection efforts.
Property and Equipment
Included in other assets in our consolidated balance sheets are “held for sale” properties of $169.8 million, $67.8 million, and $77.2 million at March 31, 2024 and 2023, and December 31, 2023, respectively. When properties are determined to be “held for sale,” the property is written down to its fair value less estimated costs to sell, as applicable. The increase in the March 31, 2024, balance from December 31, 2023, was primarily driven by a decision in the first quarter to sell certain regional properties to optimize our real estate portfolio by consolidating employees into already existing alternative properties.
Earnings Per Share
We redeemed all of our outstanding Serial Preferred Shares, Series B, in February 2024. See Note 9 – Dividends for further discussion. To determine net income available to common shareholders, which is used in the calculation of the per common share amounts, we reduced net income by preferred share dividends, and, for 2024,
underwriting discounts and commissions on the preferred share issuance,
initial issuance costs related to the preferred shares, and
excise taxes related to the preferred share redemption.
New Accounting Standards
On January 1, 2024, we started to amortize the remaining original cost of tax equity investments to the provision for income taxes, since certain conditions were met, on the modified retrospective basis, pursuant to an Accounting Standards Update (ASU) issued by the Financial Accounting Standards Board. Previously, these investments were accounted for under the equity method of accounting. The adoption of the ASU had no cumulative effect on retained earnings and did not have a material impact on our financial condition or results of operations. The amount of income tax credits and investment amortization recognized for the first quarter 2024, and the carrying amount of the tax credit investments at March 31, 2024, were not material to our financial condition or results of operations and, therefore, no additional disclosure is provided.
Reclassification
Goodwill and intangible assets are included in other assets in our consolidated balance sheets and the amortization of intangible assets in other, net, in cash provided by operating activities in our consolidated statements of cash flows. The March 31, 2023, amounts, which were presented separately on the balance sheet and statement of cash flows in the prior year, were reclassified to conform to the current year presentation.
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Investments
3 Months Ended
Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract]  
Investments INVESTMENTS
The following tables present the composition of our investment portfolio by major security type. Our securities are reported in our consolidated balance sheets at fair value. The changes in fair value for our fixed-maturity securities (other than hybrid securities) are reported as a component of accumulated other comprehensive income (loss), net of deferred income taxes, in our consolidated
balance sheets. The net holding period gains (losses) reported below represent the inception-to-date changes in fair value for the hybrid and equity securities. The changes in the net holding period gains (losses) between periods are recorded as a component of net realized gains (losses) on securities in our consolidated statements of comprehensive income.
($ in millions)CostGross
Unrealized
Gains
Gross
Unrealized
Losses
Net
Holding
Period
Gains
(Losses)
Fair
Value
% of
Total
Fair
Value
March 31, 2024
Available-for-sale securities:
Fixed maturities:
U.S. government obligations$39,823.8 $66.2 $(1,327.3)$$38,562.7 55.8 %
State and local government obligations2,200.7 1.5 (142.4)2,059.8 3.0 
Foreign government obligations16.9 (1.0)15.9 0.1 
Corporate debt securities12,821.9 45.9 (328.1)(18.4)12,521.3 18.1 
Residential mortgage-backed securities390.1 0.2 (9.2)2.0 383.1 0.6 
Commercial mortgage-backed securities4,368.6 2.5 (519.3)3,851.8 5.6 
Other asset-backed securities6,146.1 9.2 (93.9)(0.2)6,061.2 8.8 
Redeemable preferred stocks181.2 (2.0)(5.3)173.9 0.2 
Total fixed maturities65,949.3 125.5 (2,423.2)(21.9)63,629.7 92.2 
Short-term investments1,326.7 1,326.7 1.9 
Total available-for-sale securities67,276.0 125.5 (2,423.2)(21.9)64,956.4 94.1 
Equity securities:
Nonredeemable preferred stocks931.1 (44.4)886.7 1.3 
Common equities708.2 2,486.7 3,194.9 4.6 
Total equity securities1,639.3 2,442.3 4,081.6 5.9 
Total portfolio1
$68,915.3 $125.5 $(2,423.2)$2,420.4 $69,038.0 100.0 %
($ in millions)CostGross
Unrealized
Gains
Gross
Unrealized
Losses
Net
Holding
Period
Gains
(Losses)
Fair
Value
% of
Total
Fair
Value
March 31, 2023
Available-for-sale securities:
Fixed maturities:
U.S. government obligations$28,490.9 $68.8 $(1,209.6)$$27,350.1 48.3 %
State and local government obligations2,222.4 0.9 (161.7)2,061.6 3.6 
Foreign government obligations16.9 (1.1)15.8 0.1 
Corporate debt securities11,195.8 45.6 (525.4)(34.7)10,681.3 18.8 
Residential mortgage-backed securities655.0 0.2 (16.3)(8.9)630.0 1.1 
Commercial mortgage-backed securities5,252.6 1.6 (751.2)4,503.0 7.9 
Other asset-backed securities5,087.8 1.8 (222.5)(1.3)4,865.8 8.6 
Redeemable preferred stocks202.5 (5.2)(15.7)181.6 0.3 
Total fixed maturities53,123.9 118.9 (2,893.0)(60.6)50,289.2 88.7 
Short-term investments2,524.1 2,524.1 4.5 
Total available-for-sale securities55,648.0 118.9 (2,893.0)(60.6)52,813.3 93.2 
Equity securities:
Nonredeemable preferred stocks1,197.7 (118.9)1,078.8 1.9 
Common equities740.5 2,053.8 2,794.3 4.9 
Total equity securities1,938.2 1,934.9 3,873.1 6.8 
Total portfolio1
$57,586.2 $118.9 $(2,893.0)$1,874.3 $56,686.4 100.0 %


($ in millions)CostGross
Unrealized
Gains
Gross
Unrealized
Losses
Net
Holding
Period
Gains
(Losses)
Fair
Value
% of
Total
Fair
Value
December 31, 2023
Available-for-sale securities:
Fixed maturities:
U.S. government obligations$37,823.2 $204.1 $(1,157.9)$$36,869.4 55.9 %
State and local government obligations2,338.4 2.8 (138.4)2,202.8 3.3 
Foreign government obligations17.3 (1.0)16.3 0.1 
Corporate debt securities11,446.0 87.2 (332.3)(17.2)11,183.7 16.9 
Residential mortgage-backed securities426.9 0.2 (10.0)0.1 417.2 0.6 
Commercial mortgage-backed securities4,535.2 2.2 (597.7)3,939.7 6.0 
Other asset-backed securities5,667.2 15.7 (107.1)(0.4)5,575.4 8.4 
Redeemable preferred stocks187.7 (2.4)(11.6)173.7 0.3 
Total fixed maturities62,441.9 312.2 (2,346.8)(29.1)60,378.2 91.5 
Short-term investments1,789.9 1,789.9 2.7 
Total available-for-sale securities64,231.8 312.2 (2,346.8)(29.1)62,168.1 94.2 
Equity securities:
Nonredeemable preferred stocks977.1 (75.0)902.1 1.4 
Common equities706.0 2,222.4 2,928.4 4.4 
Total equity securities1,683.1 2,147.4 3,830.5 5.8 
Total portfolio1
$65,914.9 $312.2 $(2,346.8)$2,118.3 $65,998.6 100.0 %
1 At March 31, 2024 and 2023, we had $16.2 million and $22.8 million, respectively, of net unsettled security purchase transactions included in other liabilities, compared to $45.6 million included in other assets at December 31, 2023.
The total fair value of the portfolio at March 31, 2024 and 2023, and December 31, 2023, included $3.2 billion, $4.1 billion, and $4.2 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of unsettled security transactions.
At March 31, 2024, bonds and certificates of deposit in the principal amount of $672.4 million were on deposit to meet state insurance regulatory requirements. We did not hold any securities of any one issuer, excluding U.S. government obligations, with an aggregate cost or fair value exceeding 10% of total shareholders’ equity at March 31, 2024 or 2023, or December 31, 2023. At March 31, 2024, we did not hold any debt securities that were non-income producing during the preceding 12 months.
Short-Term Investments Our short-term investments may include commercial paper and other investments that are expected to mature, or are redeemable, within one year.
Hybrid Securities Certain securities in our fixed-maturity portfolio are accounted for as hybrid securities because they contain embedded derivatives that are not deemed to be clearly and closely related to the host investments. These securities are reported at fair value:
 March 31,
(millions)20242023Dec. 31, 2023
Fixed Maturities:
Corporate debt securities$507.1 $548.6 $531.3 
Residential mortgage-backed securities300.0 482.1 323.9 
Other asset-backed securities9.5 33.8 13.9 
Redeemable preferred stocks141.0 132.8 141.2 
Total hybrid securities$957.6 $1,197.3 $1,010.3 
Since the embedded derivatives (e.g., change-in-control put option, debt-to-equity conversion, or any other feature unrelated to the credit quality or risk of default of the issuer that could impact the amount or timing of our expected future cash flows) do not have observable intrinsic values, we use the fair value option to record the changes in fair value of these securities through income as a component of net realized gains (losses).
Fixed Maturities The composition of fixed maturities by maturity at March 31, 2024, was:
(millions)CostFair Value
Less than one year$7,227.5 $7,084.8 
One to five years45,277.4 43,850.9 
Five to ten years13,394.2 12,645.2 
Ten years or greater50.2 48.8 
Total$65,949.3 $63,629.7 
Asset-backed securities are classified in the maturity distribution table based upon their projected cash flows. All other securities that do not have a single maturity date are reported based upon expected average maturity. Contractual maturities may differ from expected maturities because the issuers of the securities may have the right to call or prepay obligations.
Gross Unrealized Losses The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position:
 Total No. of Sec.Total
Fair
Value
Gross
Unrealized
Losses
Less than 12 Months12 Months or Greater
($ in millions)No. of Sec.Fair
Value
Unrealized
Losses
No. of Sec.Fair
 Value
Unrealized
Losses
March 31, 2024
U.S. government obligations139 $32,968.1 $(1,327.3)37 $21,634.6 $(295.1)102 $11,333.5 $(1,032.2)
State and local government obligations330 1,922.7 (142.4)41 250.7 (1.8)289 1,672.0 (140.6)
Foreign government obligations15.9 (1.0)15.9 (1.0)
Corporate debt securities363 8,094.3 (328.1)106 2,369.6 (20.6)257 5,724.7 (307.5)
Residential mortgage-backed securities35 78.0 (9.2)34 78.0 (9.2)
Commercial mortgage-backed securities181 3,741.7 (519.3)190.5 (1.8)177 3,551.2 (517.5)
Other asset-backed securities193 3,259.5 (93.9)59 1,303.5 (2.3)134 1,956.0 (91.6)
Redeemable preferred stocks32.9 (2.0)32.9 (2.0)
Total fixed maturities1,245 $50,113.1 $(2,423.2)248 $25,748.9 $(321.6)997 $24,364.2 $(2,101.6)
 Total No. of Sec.Total
Fair
Value
Gross
Unrealized
Losses
Less than 12 Months12 Months or Greater
($ in millions)No. of Sec.Fair
Value
Unrealized
Losses
No. of Sec.Fair
 Value
Unrealized
Losses
March 31, 2023
U.S. government obligations148 $19,446.8 $(1,209.6)40 $5,938.5 $(127.5)108 $13,508.3 $(1,082.1)
State and local government obligations343 1,943.6 (161.7)72 350.7 (7.4)271 1,592.9 (154.3)
Foreign government obligations15.8 (1.1)15.8 (1.1)
Corporate debt securities390 8,129.9 (525.4)93 2,239.3 (75.5)297 5,890.6 (449.9)
Residential mortgage-backed securities43 141.7 (16.3)13 10.0 (0.4)30 131.7 (15.9)
Commercial mortgage-backed securities220 4,484.5 (751.2)11 53.4 (1.5)209 4,431.1 (749.7)
Other asset-backed securities267 4,391.9 (222.5)61 884.8 (6.2)206 3,507.1 (216.3)
Redeemable preferred stocks48.8 (5.2)10.6 (1.4)38.2 (3.8)
Total fixed maturities1,416 $38,603.0 $(2,893.0)291 $9,487.3 $(219.9)1,125 $29,115.7 $(2,673.1)

 Total No. of Sec.Total
Fair
Value
Gross
Unrealized
Losses
Less than 12 Months12 Months or Greater
($ in millions)No. of Sec.Fair
Value
Unrealized
Losses
No. of Sec.Fair
 Value
Unrealized
Losses
December 31, 2023
U.S. government obligations147 $28,225.0 $(1,157.9)25 $11,890.0 $(100.0)122 $16,335.0 $(1,057.9)
State and local government obligations324 1,846.2 (138.4)31 169.9 (0.9)293 1,676.3 (137.5)
Foreign government obligations16.3 (1.0)16.3 (1.0)
Corporate debt securities313 6,642.4 (332.3)26 617.2 (14.7)287 6,025.2 (317.6)
Residential mortgage-backed securities39 88.4 (10.0)0.4 37 88.0 (10.0)
Commercial mortgage-backed securities189 3,912.2 (597.7)30.7 (2.5)188 3,881.5 (595.2)
Other asset-backed securities207 3,299.1 (107.1)41 639.4 (1.2)166 2,659.7 (105.9)
Redeemable preferred stocks32.5 (2.4)32.5 (2.4)
Total fixed maturities1,223 $44,062.1 $(2,346.8)126 $13,347.6 $(119.3)1,097 $30,714.5 $(2,227.5)
A review of the securities in an unrealized loss position indicated that the issuers were current with respect to their interest obligations and that there was no evidence of deterioration of the current cash flow projections that would indicate we would not receive the remaining principal at maturity.
We had seven securities that had their credit ratings downgraded during the first quarter 2024, with a combined fair value of $58.2 million and an unrealized loss of $8.2 million as of March 31, 2024.
Allowance For Credit and Uncollectible Losses We are required to measure the amount of potential credit losses for all fixed-maturity securities in an unrealized loss position. We did not record any allowances for credit losses or any write-offs for amounts deemed to be uncollectible during the first three months of 2024 or 2023, and did not have a material credit loss allowance balance as of March 31, 2024 and 2023, or December 31, 2023. We considered several factors and inputs related to the individual securities as part of our analysis. The methodology and significant inputs used to measure the amount of credit losses in our portfolio included:

current performance indicators on the business model or underlying assets (e.g., delinquency rates, foreclosure rates, and default rates);
credit support (via current levels of subordination);
historical credit ratings; and
updated cash flow expectations based upon these performance indicators.
In order to determine the amount of credit loss, if any, we initially reviewed securities in a loss position to determine whether it was likely that we would be required, or intended, to sell any of the securities prior to the recovery of their respective cost bases (which could be maturity). If we were likely to, or intended to, sell prior to a potential recovery, we would write off the unrealized loss. For those securities that we determined we were not likely to, or did not intend to, sell prior to a potential recovery, we performed additional analysis to determine if the loss was
credit related. For securities subject to credit related loss, we calculated the net present value (NPV) of the cash flows expected (i.e., expected recovery value) using the current book yield for each security. The NPV was then compared to the security’s current amortized value to determine if a credit loss existed. In the event that the NPV was below the amortized value, and the amount was determined to be material on any specific security, or in the aggregate, a credit loss would be deemed to exist, and either an allowance for credit losses would be created, or if an allowance currently existed, either a recovery of the previous allowance, or an incremental loss, would be recorded to net realized gains (losses) on securities.
As of March 31, 2024 and 2023, and December 31, 2023, we believe that none of the unrealized losses on our fixed-maturity securities were related to material credit losses on any specific securities, or in the aggregate. We continue to expect all the securities in our fixed-maturity portfolio to pay their principal and interest obligations.
In addition, we reviewed our accrued investment income outstanding on those securities in an unrealized loss position at March 31, 2024 and 2023, and December 31, 2023, to determine if the accrued interest amounts were uncollectible. Based on our analysis, we believe the issuers have sufficient liquidity and capital reserves to meet their current interest, and future principal, obligations and, therefore, did not write off any accrued income as uncollectible at March 31, 2024 and 2023, or December 31, 2023.
Realized Gains (Losses) The components of net realized gains (losses) for the three months ended March 31, were:
 Three Months
(millions)20242023
Gross realized gains on security sales
Available-for-sale securities:
U.S. government obligations$$3.8 
State and local government obligations0.3 
Corporate debt securities2.9 0.1 
Total available-for-sale securities3.2 3.9 
Equity securities:
Nonredeemable preferred stocks0.1 
Common equities11.2 132.0 
Total equity securities11.2 132.1 
Subtotal gross realized gains on security sales14.4 136.0 
Gross realized losses on security sales
Available-for-sale securities:
U.S. government obligations(135.3)(11.5)
State and local government obligations(0.1)
Corporate debt securities(14.8)(20.4)
Commercial mortgage-backed securities(4.3)(34.5)
Other asset-backed securities(0.1)(0.2)
Redeemable preferred stocks(0.3)
Short-term investments(0.1)
Total available-for-sale securities(154.9)(66.7)
Equity securities:
Nonredeemable preferred stocks(5.9)(101.0)
Common equities(0.1)(11.8)
Total equity securities(6.0)(112.8)
Subtotal gross realized losses on security sales(160.9)(179.5)
Net realized gains (losses) on security sales
Available-for-sale securities:
U.S. government obligations(135.3)(7.7)
State and local government obligations0.2 
Corporate debt securities(11.9)(20.3)
Commercial mortgage-backed securities(4.3)(34.5)
Other asset-backed securities(0.1)(0.2)
Redeemable preferred stocks(0.3)
Short-term investments(0.1)
Total available-for-sale securities(151.7)(62.8)
Equity securities:
Nonredeemable preferred stocks(5.9)(100.9)
Common equities11.1 120.2 
Total equity securities5.2 19.3 
Subtotal net realized gains (losses) on security sales(146.5)(43.5)
Other assets
Gain13.2 
Impairment(2.3)
Subtotal net realized gains (losses) on other assets10.9 
Net holding period gains (losses)
Hybrid securities7.2 13.9 
Equity securities294.9 90.5 
Subtotal net holding period gains (losses)302.1 104.4 
Total net realized gains (losses) on securities$155.6 $71.8 
Realized gains (losses) on securities sold are computed using the first-in-first-out method. During the first three months of 2024, the majority of our gross realized losses on security sales were U.S. Treasury Notes that were sold for duration management. We also sold corporate debt securities with less attractive risk/reward profiles and select commercial mortgage-backed securities. During the first quarter 2023, the gross gains in common equities reflected sales of securities, as part of our plan to incrementally reduce risk in the portfolio in response to our view of the potential of a more difficult economic environment. The gross loss incurred in our nonredeemable preferred stocks,
during the first quarter 2023, was primarily related to the sale of certain holdings in U.S. bank preferred stocks. In addition, during the first quarter last year, we selectively sold securities, which were primarily corporate debt securities and commercial mortgage-backed securities.

The other asset gain for the first three months of 2023, related to proceeds received as the result of litigation in conjunction with three renewable energy investments we made from 2016 through 2018 (the original investments were previously written down in full).
The following table reflects our holding period realized gains (losses) recognized on equity securities held at the respective periods ended March 31:
Three Months
(millions)20242023
Total net gains (losses) recognized during the period on equity securities$300.1 $109.8 
Less: Net gains (losses) recognized on equity securities sold during the period5.2 19.3 
Net holding period gains (losses) recognized during the period on equity securities held at period end$294.9 $90.5 
Net Investment Income The components of net investment income for the three months ended March 31, were: 
Three Months
(millions)20242023
Available-for-sale securities:
Fixed maturities:
U.S. government obligations$306.9 $163.2 
State and local government obligations12.4 10.6 
Foreign government obligations0.1 0.1 
Corporate debt securities121.5 83.6 
Residential mortgage-backed securities5.4 9.2 
Commercial mortgage-backed securities46.4 50.0 
Other asset-backed securities78.2 48.5 
Redeemable preferred stocks2.9 2.9 
Total fixed maturities573.8 368.1 
Short-term investments18.9 24.7 
Total available-for-sale securities592.7 392.8 
Equity securities:
Nonredeemable preferred stocks11.0 15.1 
Common equities13.9 11.7 
Total equity securities24.9 26.8 
Investment income617.6 419.6 
Investment expenses(5.7)(5.5)
Net investment income$611.9 $414.1 
On a year-over-year basis, investment income (interest and dividends) increased 47% and recurring investment book yield increased 23% for the three months ended March 31, 2024, compared to the same period last year. The increases primarily reflected investing new cash from operations and proceeds from maturing bonds in higher coupon rate securities.
v3.24.1.u1
Fair Value
3 Months Ended
Mar. 31, 2024
Fair Value Disclosures [Abstract]  
Fair Value FAIR VALUE
We have categorized our financial instruments, based on the degree of subjectivity inherent in the method by which they are valued, into a fair value hierarchy of three levels, as follows:
Level 1: Inputs are unadjusted, quoted prices in active markets for identical instruments at the measurement date (e.g., U.S. government obligations, which are continually priced on a daily basis, active exchange-traded equity securities, and certain short-term securities).
Level 2: Inputs (other than quoted prices included within Level 1) that are observable for the instrument either directly or indirectly (e.g., certain corporate and municipal bonds and certain preferred stocks). This includes: (i) quoted prices for similar instruments in active markets, (ii) quoted prices for identical or similar instruments in markets that are not active, (iii) inputs other than quoted prices that are
observable for the instruments, and (iv) inputs that are derived principally from or corroborated by observable market data by correlation or other means.
Level 3: Inputs that are unobservable. Unobservable inputs reflect our subjective evaluation about the assumptions market participants would use in pricing the financial instrument (e.g., certain structured securities and privately held investments).
Determining the fair value of the investment portfolio is the responsibility of management. As part of that responsibility, we evaluate whether a market is distressed or inactive in determining the fair value for our portfolio. We review certain market level inputs to evaluate whether sufficient activity, volume, and new issuances exist to create an active market. Based on this evaluation, we concluded that there was sufficient activity related to the sectors and securities for which we obtained valuations.
The composition of the investment portfolio by major security type and our outstanding debt was:
 Fair Value 
(millions)Level 1Level 2Level 3TotalCost
March 31, 2024
Fixed maturities:
U.S. government obligations$38,562.7 $$$38,562.7 $39,823.8 
State and local government obligations2,059.8 2,059.8 2,200.7 
Foreign government obligations15.9 15.9 16.9 
Corporate debt securities12,518.3 3.0 12,521.3 12,821.9 
Subtotal38,562.7 14,594.0 3.0 53,159.7 54,863.3 
Asset-backed securities:
Residential mortgage-backed383.1 383.1 390.1 
Commercial mortgage-backed3,851.8 3,851.8 4,368.6 
Other asset-backed6,061.2 6,061.2 6,146.1 
Subtotal asset-backed securities10,296.1 10,296.1 10,904.8 
Redeemable preferred stocks:
Financials23.2 23.2 24.5 
Utilities9.6 9.6 10.4 
Industrials141.1 141.1 146.3 
Subtotal redeemable preferred stocks173.9 173.9 181.2 
Total fixed maturities38,562.7 25,064.0 3.0 63,629.7 65,949.3 
Short-term investments1,326.7 1,326.7 1,326.7 
    Total available-for-sale securities39,889.4 25,064.0 3.0 64,956.4 67,276.0 
Equity securities:
Nonredeemable preferred stocks:
Financials785.3 49.2 834.5 876.1 
Utilities37.4 37.4 40.0 
Industrials14.8 14.8 15.0 
Subtotal nonredeemable preferred stocks822.7 64.0 886.7 931.1 
Common equities:
Common stocks3,148.1 22.5 3,170.6 683.9 
Other risk investments24.3 24.3 24.3 
Subtotal common equities3,148.1 46.8 3,194.9 708.2 
    Total equity securities3,148.1 822.7 110.8 4,081.6 1,639.3 
Total portfolio$43,037.5 $25,886.7 $113.8 $69,038.0 $68,915.3 
Debt$$6,297.8 $$6,297.8 $6,889.7 
 Fair Value 
(millions)Level 1Level 2Level 3TotalCost
March 31, 2023
Fixed maturities:
U.S. government obligations$27,350.1 $$$27,350.1 $28,490.9 
State and local government obligations2,061.6 2,061.6 2,222.4 
Foreign government obligations15.8 15.8 16.9 
Corporate debt securities10,681.3 10,681.3 11,195.8 
Subtotal27,350.1 12,758.7 40,108.8 41,926.0 
Asset-backed securities:
Residential mortgage-backed630.0 630.0 655.0 
Commercial mortgage-backed4,503.0 4,503.0 5,252.6 
Other asset-backed4,865.8 4,865.8 5,087.8 
Subtotal asset-backed securities9,998.8 9,998.8 10,995.4 
Redeemable preferred stocks:
Financials40.0 40.0 43.5 
Utilities8.8 8.8 10.5 
Industrials9.6 123.2 132.8 148.5 
Subtotal redeemable preferred stocks9.6 172.0 181.6 202.5 
Total fixed maturities27,359.7 22,929.5 50,289.2 53,123.9 
Short-term investments2,524.1 2,524.1 2,524.1 
    Total available-for-sale securities29,883.8 22,929.5 52,813.3 55,648.0 
Equity securities:
Nonredeemable preferred stocks:
Financials40.0 884.5 67.4 991.9 1,102.7 
Utilities70.5 70.5 80.0 
Industrials16.4 16.4 15.0 
Subtotal nonredeemable preferred stocks40.0 955.0 83.8 1,078.8 1,197.7 
Common equities:
Common stocks2,755.7 18.3 2,774.0 720.2 
Other risk investments20.3 20.3 20.3 
Subtotal common equities2,755.7 38.6 2,794.3 740.5 
    Total equity securities2,795.7 955.0 122.4 3,873.1 1,938.2 
Total portfolio$32,679.5 $23,884.5 $122.4 $56,686.4 $57,586.2 
Debt$$5,881.0 $$5,881.0 $6,389.3 
 Fair Value 
(millions)Level 1Level 2Level 3TotalCost
December 31, 2023
Fixed maturities:
U.S. government obligations$36,869.4 $$$36,869.4 $37,823.2 
State and local government obligations2,202.8 2,202.8 2,338.4 
Foreign government obligations16.3 16.3 17.3 
Corporate debt securities11,180.7 3.0 11,183.7 11,446.0 
Subtotal36,869.4 13,399.8 3.0 50,272.2 51,624.9 
Asset-backed securities:
Residential mortgage-backed417.2 417.2 426.9 
Commercial mortgage-backed3,939.7 3,939.7 4,535.2 
Other asset-backed5,575.4 5,575.4 5,667.2 
Subtotal asset-backed securities9,932.3 9,932.3 10,629.3 
Redeemable preferred stocks:
Financials23.1 23.1 24.5 
Utilities9.4 9.4 10.4 
Industrials141.2 141.2 152.8 
Subtotal redeemable preferred stocks173.7 173.7 187.7 
Total fixed maturities36,869.4 23,505.8 3.0 60,378.2 62,441.9 
Short-term investments1,757.0 32.9 1,789.9 1,789.9 
    Total available-for-sale securities38,626.4 23,538.7 3.0 62,168.1 64,231.8 
Equity securities:
Nonredeemable preferred stocks:
Financials802.7 49.2 851.9 922.1 
Utilities35.4 35.4 40.0 
Industrials14.8 14.8 15.0 
Subtotal nonredeemable preferred stocks838.1 64.0 902.1 977.1 
Common equities:
Common stocks2,885.3 22.5 2,907.8 685.4 
Other risk investments20.6 20.6 20.6 
Subtotal common equities2,885.3 43.1 2,928.4 706.0 
    Total equity securities2,885.3 838.1 107.1 3,830.5 1,683.1 
Total portfolio$41,511.7 $24,376.8 $110.1 $65,998.6 $65,914.9 
Debt$$6,431.3 $$6,431.3 $6,888.6 

Our portfolio valuations, excluding short-term investments, classified as either Level 1 or Level 2 in the above tables are priced exclusively by external sources, including pricing vendors, dealers/market makers, and exchange-quoted prices.
Our short-term investments classified as Level 1 are highly liquid, actively marketed, and have a very short duration, primarily 90 days or less to redemption. These securities are held at their original cost, adjusted for any accretion of discount, since that value very closely approximates what an active market participant would be willing to pay for such securities. The remainder of our short-term investments are classified as Level 2 and are not priced externally since these securities continually trade at par value. These securities are classified as Level 2 since they are primarily longer-dated securities issued by municipalities that contain either liquidity facilities or mandatory put features within one year.
At March 31, 2024, vendor-quoted prices represented 92% of our Level 1 classifications (excluding short-term investments), compared to 91% at March 31, 2023 and 93% at December 31, 2023. The securities quoted by vendors in Level 1 primarily represent our holdings in U.S. Treasury Notes, which are frequently traded, and the quotes are considered similar to exchange-traded quotes. The balance of our Level 1 pricing comes from quotes obtained directly from trades made on active exchanges. All Level 1 preferred stocks with active exchange quotes were sold during 2023.
At both March 31, 2024 and December 31, 2023, vendor-quoted prices comprised 100% of our Level 2 classifications (excluding short-term investments), compared to 98% at March 31, 2023; the remaining 2% at March 31, 2023 were dealer-quoted prices. In our process for selecting a source (e.g., dealer or pricing service) to provide pricing for securities in our portfolio, we reviewed documentation from the sources that detailed the pricing
techniques and methodologies used by these sources and determined if their policies adequately considered market activity, either based on specific transactions for the particular security type or based on modeling of securities with similar credit quality, duration, yield, and structure that were recently transacted. Once a source is chosen, we continue to monitor any changes or modifications to their processes by reviewing their documentation on internal controls for pricing and market reviews. We review quality control measures of our sources as they become available to determine if any significant changes have occurred from period to period that might indicate issues or concerns regarding their evaluation or market coverage.
As part of our pricing procedures, we obtain quotes from more than one source to help us fully evaluate the market price of securities. However, our internal pricing policy is to use a consistent source for individual securities in order to maintain the integrity of our valuation process. Quotes obtained from the sources are not considered binding offers to transact. Under our policy, when a review of the valuation received from our selected source appears to be outside of what is considered market level activity (which is defined as trading at spreads or yields significantly different than those of comparable securities or outside the general sector level movement without a reasonable explanation), we may use an alternate source’s price. To the extent we determine that it may be prudent to substitute one source’s price for another, we will contact the initial source to obtain an understanding of the factors that may be contributing to the significant price variance.
To allow us to determine if our initial source is providing a price that is outside of a reasonable range, we review our portfolio pricing on a weekly basis. When necessary, we challenge prices from our sources when a price provided does not match our expectations based on our evaluation of market trends and activity. Initially, we perform a review of our portfolio by sector to identify securities whose prices appear outside of a reasonable range. We then perform a more detailed review of fair values for securities disclosed as Level 2. We review dealer bids and quotes for these and/or similar securities to determine the market level context for our valuations. We then evaluate inputs relevant for each class of securities disclosed in the preceding hierarchy tables.
For structured debt securities, including commercial, residential, and other asset-backed securities, we evaluate available market-related data for these and similar securities related to collateral, delinquencies, and defaults for historical trends and reasonably estimable projections, as well as historical prepayment rates and current prepayment assumptions and cash flow estimates. We further stratify each class of our structured debt securities into more finite sectors (e.g., planned amortization class, first pay, second pay, senior, subordinated, etc.) and use duration, credit quality, and coupon to determine if the fair value is appropriate.
For corporate debt and preferred stock (redeemable and nonredeemable) portfolios, as well as the notes issued by The Progressive Corporation (see Note 4 – Debt), we review securities by duration, credit quality, and coupon, as well as changes in interest rate and credit spread movements within that stratification. The review also includes recent trades, including: volume traded at various levels that establish a market; issuer specific fundamentals; and industry-specific economic news as it comes to light.
For municipal securities (e.g., general obligations, revenue, and housing), we stratify the portfolio to evaluate securities by type, duration, credit quality, and coupon to review price changes relative to credit spread and interest rate changes. Additionally, we look to economic data as it relates to geographic location as an indication of price-to-call or maturity predictors. For municipal housing securities, we look to changes in cash flow projections, both historical and reasonably estimable projections, to understand yield changes and their effect on valuation.
For short-term securities, we look at acquisition price relative to the coupon or yield. Since our short-term securities are typically 90 days or less to maturity, with the majority listed in Level 2 being 30 days or less to redemption, we believe that acquisition price is the best estimate of fair value.
We also review data assumptions as supplied by our sources to determine if that data is relevant to current market conditions. In addition, we independently review each sector for transaction volumes, new issuances, and changes in spreads, as well as the overall movement of interest rates along the yield curve to determine if sufficient activity and liquidity exists to provide a credible source for our market valuations.
During each valuation period, we create internal estimations of portfolio valuation (performance returns), based on current market-related activity (i.e., interest rate and credit spread movements and other credit-related factors) within each major sector of our portfolio. We compare our internally generated portfolio results with those generated based on quotes we receive externally and research material valuation differences. We compare our results to index returns for each major sector adjusting for duration and credit quality differences to better understand our portfolio’s results. Additionally, we review on a monthly basis our external sales transactions and compare the actual final market sales prices to previous market valuation prices. This review provides us further validation that our pricing sources are providing market level prices, since we are able to explain significant price changes (i.e., greater than 2%) as known events occur in the marketplace and affect a particular security’s price at sale.
This analysis provides us with additional comfort regarding the source’s process, the quality of its review, and its willingness to improve its analysis based on feedback from clients. We believe this effort helps ensure that we are
reporting the most representative fair values for our securities.
After all the valuations are received and our review of Level 2 securities is complete, if the inputs used by vendors are determined to not contain sufficient observable market information, we will reclassify the affected securities to Level 3.
Except as described below, our Level 3 securities are priced externally; however, due to several factors (e.g., nature of the securities, level of activity, and lack of similar securities trading to obtain observable market level inputs), these valuations are more subjective in nature.
To the extent we receive prices from external sources (e.g., broker, valuation firm) for the Level 3 securities, we review those prices for reasonableness using internally developed assumptions and then compare our derived prices to the prices received from the external sources. Based on our review, all prices received from external sources remained unadjusted.
If we do not receive prices from an external source, we perform an internal fair value comparison, which includes a review and analysis of market-comparable securities, to determine if fair value changes are needed. Based on this analysis, certain private equity investments included in the Level 3 category remain valued at cost or were priced using a recent transaction as the basis for fair value. At least annually, these private equity investments are priced by an external source.

Our Level 3 other risk investments include securities accounted for under the equity method of accounting and, therefore, are not subject to fair value reporting. Since these securities represent less than 0.1% of our total portfolio, we will continue to include them in our Level 3 disclosures and report the activity from these investments as “other” changes in the summary of changes in fair value table and categorize these securities as “pricing exemption securities” in the quantitative information table.
At both March 31, 2024 and December 31, 2023, we held one privately held fixed-maturity security that is classified as a Level 3 investment. At March 31, 2023, we did not have any securities in our fixed-maturity portfolio listed as Level 3.
During the first three months of 2024 and for the full year of 2023, there were no material assets or liabilities measured at fair value on a nonrecurring basis.
Due to the relative size of the Level 3 securities’ fair values, compared to the total portfolio’s fair value, any changes in pricing methodology would not have a significant change in valuation that would materially impact net or comprehensive income.
The following tables provide a summary of changes in fair value associated with Level 3 assets for the three months ended March 31, 2024 and 2023:
Level 3 Fair Value
(millions)Fair Value at December 31, 2023Calls/
Maturities/
Paydowns/Other
PurchasesSalesNet Realized
(Gain)/Loss
on Sales
Change in
Valuation
Net
Transfers
In (Out)
Fair Value at March 31, 2024
Fixed maturities:
Corporate debt securities$3.0 $$$$$$$3.0 
Equity securities:
Nonredeemable preferred stocks:
Financials
49.2 49.2 
Industrials
14.8 14.8 
Common equities:
Common stocks22.5 22.5 
Other risk investments20.6 3.7 24.3 
Total Level 3 securities$110.1 $3.7 $$$$$$113.8 
Level 3 Fair Value
(millions)Fair Value at December 31, 2022Calls/
Maturities/
Paydowns/Other
PurchasesSalesNet Realized
(Gain)/Loss
on Sales
Change in
Valuation
Net
Transfers
In (Out)
Fair Value at March 31, 2023
Equity securities:
Nonredeemable preferred stocks:
Financials
$67.4 $$$$$$$67.4 
Industrials
16.4 16.4 
Common equities:
Common stocks18.3 18.3 
Other risk investments19.8 0.5 20.3 
Total Level 3 securities
$121.9 $0.5 $$$$$$122.4 
The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at March 31, 2024 and 2023, and December 31, 2023:
Quantitative Information about Level 3 Fair Value Measurements
($ in millions)Fair Value at March 31, 2024Valuation TechniqueUnobservable InputRange of Input Values Increase (Decrease)Weighted Average Increase (Decrease)
Fixed maturities:
Corporate debt securities$3.0 Market comparablesWeighted average market capitalization price change %
(2.3)% to 1.2%
(0.1)%
Equity securities:
Nonredeemable preferred stocks64.0 Market comparablesWeighted average market capitalization price change %
3.4% to 28.4%
22.6 %
Common stocks22.5 Market comparablesWeighted average market capitalization price change %
(37.9)% to 39.6%
3.4 %
Subtotal Level 3 securities89.5 
Pricing exemption securities24.3 
Total Level 3 securities$113.8 


Quantitative Information about Level 3 Fair Value Measurements
($ in millions)Fair Value at March 31, 2023Valuation TechniqueUnobservable InputRange of Input Values Increase (Decrease)Weighted Average Increase (Decrease)
Equity securities:
Nonredeemable preferred stocks$83.8 Market comparablesWeighted average market capitalization price change %
2.7% to 23.3%
9.2 %
Common stocks18.3 Market comparablesWeighted average market capitalization price change %
(51.3)% to 48.3%
15.6 %
Subtotal Level 3 securities102.1 
Pricing exemption securities20.3 
Total Level 3 securities$122.4 


Quantitative Information about Level 3 Fair Value Measurements
($ in millions)Fair Value at December 31, 2023Valuation TechniqueUnobservable InputRange of Input Values Increase (Decrease)Weighted Average Increase (Decrease)
Fixed maturities:
Corporate debt securities$3.0 Market comparablesWeighted average market capitalization price change %
0.3% to 7.7%
2.6 %
Equity securities:
Nonredeemable preferred stocks64.0 Market comparablesWeighted average market capitalization price change %
17.2% to 39.7%
21.7%
Common stocks22.5 Market comparablesWeighted average market capitalization price change %
(45.8)% to 95.6%
39.7%
Subtotal Level 3 securities89.5 
Pricing exemption securities20.6 
Total Level 3 securities$110.1 
v3.24.1.u1
Debt
3 Months Ended
Mar. 31, 2024
Debt Disclosure [Abstract]  
Debt DEBT
Debt at each of the balance sheet periods consisted of:
 March 31, 2024March 31, 2023December 31, 2023
(millions)Carrying
Value
Fair
Value
Carrying
Value
Fair
Value
Carrying
Value
Fair
Value
2.45% Senior Notes due 2027 (issued: $500.0, August 2016)
$498.7 $468.6 $498.3 $464.2 $498.6 $468.9 
2.50% Senior Notes due 2027 (issued: $500.0, March 2022)
498.2 468.5 497.7 463.8 498.1 469.1 
6 5/8% Senior Notes due 2029 (issued: $300.0, March 1999)
297.9 323.5 297.6 329.6 297.8 328.7 
4.00% Senior Notes due 2029 (issued: $550.0, October 2018)
547.1 532.5 546.5 538.5 546.9 542.6 
3.20% Senior Notes due 2030 (issued: $500.0, March 2020)
497.4 456.1 497.0 460.0 497.3 462.2 
3.00% Senior Notes due 2032 (issued: $500.0, March 2022)
496.4 435.7 496.0 446.9 496.3 446.0 
6.25% Senior Notes due 2032 (issued: $400.0, November 2002)
396.8 434.2 396.5 448.1 396.7 445.6 
4.95% Senior Notes due 2033 (issued: $500.0, May 2023)
496.5 499.2 496.4 513.0 
4.35% Senior Notes due 2044 (issued: $350.0, April 2014)
347.0 312.8 346.9 312.3 347.0 314.2 
3.70% Senior Notes due 2045 (issued: $400.0, January 2015)
395.9 327.9 395.8 324.0 395.9 325.1 
4.125% Senior Notes due 2047 (issued: $850.0, April 2017)
842.3 719.2 842.1 743.8 842.3 756.2 
4.20% Senior Notes due 2048 (issued: $600.0, March 2018)
590.7 519.8 590.4 530.0 590.6 534.1 
3.95% Senior Notes due 2050 (issued: $500.0, March 2020)
491.2 409.8 491.0 420.3 491.1 422.3 
3.70% Senior Notes due 2052 (issued: $500.0, March 2022)
493.6 390.0 493.5 399.5 493.6 403.3 
Total$6,889.7 $6,297.8 $6,389.3 $5,881.0 $6,888.6 $6,431.3 
There was no short-term debt outstanding as of the end of all the periods presented.
The Progressive Corporation has a line of credit with PNC Bank, National Association, in the maximum principal amount of $300 million. See the 2023 Annual Report to Shareholders for a discussion of the terms of this line of credit. We had no borrowings under the line of credit that was available during the periods presented.
v3.24.1.u1
Income Taxes
3 Months Ended
Mar. 31, 2024
Income Tax Disclosure [Abstract]  
Income Taxes INCOME TAXES
The effective tax rate for the three months ended March 31, 2024, was 20.7%, compared to 19.2% for the same period last year, with the change primarily due to our permanent tax differences having a lower impact on our effective rate due to increased profitability in the current year.
Deferred tax assets and liabilities are recorded based on the difference between the financial statement and tax bases of assets and liabilities at the enacted tax rates. We review our deferred tax assets regularly for recoverability. At March 31, 2024 and 2023, and December 31, 2023, we determined that we did not need a valuation allowance on our gross deferred tax assets. Although realization of the deferred tax assets is not assured, management believes that it is more likely than not the deferred tax assets will be realized based on our expectation that we will be able to fully utilize the deductions that are ultimately recognized for tax purposes. At March 31, 2024 and 2023, and December 31, 2023, the net deferred tax asset includes a
gross deferred tax asset of $482.5 million, $582.6 million, and $427.3 million, respectively, related to unrealized losses on fixed-maturity securities. We believe this deferred tax asset will be realized based on the existence of current temporary differences related to unrealized gains in our equity portfolio, prior year capital gains, and other tax planning strategies.
We had net current income taxes payable of $961.8 million, $203.3 million, and $311.8 million at March 31, 2024 and 2023, and December 31, 2023, respectively, included in accounts payable, accrued expenses, and other liabilities on our consolidated balance sheets. The increase in income taxes payable was primarily driven by the increase in profitability during the first quarter 2024.
At March 31, 2024 and 2023, and December 31, 2023, we had no reserves for uncertain tax positions.
v3.24.1.u1
Loss and Loss Adjustment Expense Reserves
3 Months Ended
Mar. 31, 2024
Loss and Loss Adjustment Expenses Reserves [Abstract]  
Loss and Loss Adjustment Expense Reserves LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES
Activity in the loss and loss adjustment expense reserves is summarized as follows:
March 31,
(millions)20242023
Balance at January 1$34,389.2 $30,359.3 
Less reinsurance recoverables on unpaid losses4,789.0 5,559.2 
Net balance at January 129,600.2 24,800.1 
Incurred related to:
Current year10,983.0 10,002.8 
Prior years(11.4)621.2 
Total incurred10,971.6 10,624.0 
Paid related to:
Current year4,421.7 3,962.6 
Prior years5,971.0 5,736.2 
Total paid10,392.7 9,698.8 
Net balance at March 31
30,179.1 25,725.3 
Plus reinsurance recoverables on unpaid losses4,651.9 5,301.1 
Balance at March 31
$34,831.0 $31,026.4 
We experienced favorable reserve development of $11.4 million during the first three months of 2024, compared to unfavorable development of $621.2 million for the same period last year, which is reflected as “incurred related to prior years in the table above.
First Quarter 2024
The favorable prior year reserve development included approximately $50 million of favorable development attributable to accident year 2023 and $15 million to accident year 2022; partially offset by unfavorable development attributable to accident years 2021 and prior.
Our personal auto products incurred about $100 million of favorable loss and loss adjustment expense (LAE) reserve development, in part due to lower than anticipated frequency in Florida following tort reform that passed in the first quarter 2023, with about 60% attributable to the Agency auto business and the balance in the Direct auto business.
Our Commercial Lines business experienced about $70 million of unfavorable development, primarily driven by higher than anticipated severity in our commercial auto business for California and New York.
First Quarter 2023
The unfavorable prior year reserve development included approximately $498 million attributable to accident year 2022, $30 million to accident year 2021, and the remainder to accident years 2020 and prior.
Our personal auto products incurred about $428 million of unfavorable loss and LAE reserve development, with the Agency and Direct auto businesses each contributing about half. The unfavorable development was primarily attributable to higher than anticipated severity in auto property and physical damage coverages, higher than anticipated late reported injury claims, and, to a lessor extent, increased loss costs in Florida injury and medical coverages in small part due to the impact of the legislation enacted in March 2023 in Florida.
Our Commercial Lines business experienced about $144 million of unfavorable development, primarily due to higher than anticipated severity of injury case reserves and higher than anticipated severity and frequency of late reported injury claims.
Our Property business experienced $42 million of unfavorable development, primarily from higher than anticipated claims expenses and higher than anticipated severity in our homeowner liability peril and umbrella products.
v3.24.1.u1
Supplemental Cash Flow Information
3 Months Ended
Mar. 31, 2024
Supplemental Cash Flow Elements [Abstract]  
Supplemental Cash Flow Information SUPPLEMENTAL CASH FLOW INFORMATION
Cash and cash equivalents include bank demand deposits and daily overnight reverse repurchase commitments of funds held in bank demand deposit accounts by certain subsidiaries. The amount of overnight reverse repurchase commitments, which are not considered part of the investment portfolio, held by these subsidiaries at March 31, 2024 and 2023, and December 31, 2023, were $107.7 million, $177.5 million, and $68.2 million, respectively. Restricted cash and restricted cash equivalents include collateral held against unpaid deductibles and cash that is restricted to pay flood claims under the National Flood Insurance Program’s “Write Your Own” program, for which certain subsidiaries are participants.
Non-cash activity included the following in the respective periods:
Three Months Ended March 31,
(millions)20242023
Common share dividends1
$58.6 $58.5 
Operating lease liabilities2
28.0 9.3 
1 Declared but unpaid. See Note 9 – Dividends for further discussion.
2 From obtaining right-of-use assets.
In the respective periods, we paid the following: 
 Three Months Ended March 31,
(millions)20242023
Income taxes$$0.1 
Interest87.9 87.9 
Operating lease liabilities21.6 21.5 
v3.24.1.u1
Segment Information
3 Months Ended
Mar. 31, 2024
Segment Reporting [Abstract]  
Segment Information SEGMENT INFORMATION
Our Personal Lines segment writes insurance for personal autos and recreational vehicles (our special lines products). Our Commercial Lines segment writes auto-related liability and physical damage insurance, business-related general liability and property insurance predominately for small businesses, and workers’ compensation insurance primarily for the transportation industry. Our Property segment writes residential property insurance for homeowners, other property owners, and renters, and
umbrella insurance. Our service businesses provide insurance-related services, including serving as an agent for homeowners, general liability, and workers’ compensation insurance, among other products, through programs in our direct Personal Lines and Commercial Lines businesses. All segment revenues are generated from external customers; all intercompany transactions are eliminated in consolidation.
Following are the operating results for the respective periods:
 Three Months Ended March 31,
 20242023
(millions)RevenuesPretax
Profit (Loss)
RevenuesPretax
Profit (Loss)
Personal Lines
Agency$5,857.7 $950.7 $4,860.2 $162.6 
Direct7,020.5 1,043.6 5,717.4 (22.1)
Total Personal Lines1
12,878.2 1,994.3 10,577.6 140.5 
Commercial Lines2,557.4 209.0 2,356.1 37.2 
Property712.8 46.9 598.7 (32.7)
Other indemnity2
0.2 (0.3)0.7 (3.4)
Total underwriting operations16,148.6 2,249.9 13,533.1 141.6 
Fees and other revenues3
236.5 NA206.2 NA
Service businesses84.2 (7.9)72.5 (9.8)
Investments4
773.2 767.5 491.4 485.9 
Interest expenseNA(69.6)NA(63.3)
Consolidated total$17,242.5 $2,939.9 $14,303.2 $554.4 
NA = Not applicable
1 Personal auto insurance accounted for 95% and 94% of the total Personal Lines segment net premiums earned during the three months ended March 31, 2024 and 2023, respectively; insurance for our special lines products (e.g., motorcycles, RVs, watercraft, and snowmobiles) accounted for the balance of the Personal Lines net premiums earned.
2 Includes other underwriting business and run-off operations.
3 Pretax profit (loss) for fees and other revenues is allocated to operating segments based on revenue.
4 Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit (loss) is net of investment expenses.
Our management uses underwriting margin and combined ratio as primary measures of underwriting profitability. The underwriting margin is the pretax underwriting profit (loss) expressed as a percentage of net premiums earned (i.e., revenues from underwriting operations). Pretax underwriting profit (loss) is calculated as net premiums earned plus fees and other revenues, less: (i) losses and loss adjustment expenses; (ii) policy acquisition costs; and (iii) other underwriting expenses. Combined ratio is the complement of the underwriting margin. Following are the underwriting margins and combined ratios for our underwriting operations for the respective periods:
 Three Months Ended March 31,
 20242023
 Under-writing
Margin
Combined
Ratio
Under-writing
Margin
Combined
Ratio
Personal Lines
Agency16.2 %83.8 3.3 %96.7 
Direct14.9 85.1 (0.4)100.4 
Total Personal Lines15.5 84.5 1.3 98.7 
Commercial Lines8.2 91.8 1.6 98.4 
Property6.6 93.4 (5.5)105.5 
Total underwriting operations13.9 86.1 1.0 99.0 
v3.24.1.u1
Dividends
3 Months Ended
Mar. 31, 2024
Dividends [Abstract]  
Dividends DIVIDENDS
Following is a summary of our common and preferred share dividends that were declared and/or paid during the three months ended March 31, 2024 and 2023:
(millions, except per share amounts)Amount
DeclaredPayablePer Share
Accrued/Paid1
Common – Annual-Variable Dividends:
December 2023January 2024$0.75 $439.3 
Common – Quarterly Dividends:
March 2024April 20240.10 58.6 
December 2023January 20240.10 58.6 
March 2023April 20230.10 58.5 
December 2022January 20230.10 58.5 
Preferred Dividends:
January 20242
February 202415.688377 7.8 
December 2022March 202326.875 13.4 
1 The accrual is based on an estimate of shares outstanding as of the record date and recorded as a component of accounts payable, accrued expenses, and other liabilities on our consolidated balance sheets until paid.
2 During the first quarter 2024, we redeemed all of the outstanding Serial Preferred Shares, Series B, at the stated amount of $1,000 per share, for an aggregate payout of $507.8 million, including accrued and unpaid dividends of $7.8 million to, but excluding, February 22, 2024, which was the redemption date.
See Note 14 Dividends in our 2023 Annual Report to Shareholders for a discussion of the dividend policies related to our common shares and our preferred shares, prior to redemption.
v3.24.1.u1
Other Comprehensive Income (Loss)
3 Months Ended
Mar. 31, 2024
Equity [Abstract]  
Other Comprehensive Income (Loss) OTHER COMPREHENSIVE INCOME (LOSS)
The components of other comprehensive income (loss), including reclassification adjustments by income statement line item, were as follows: 
    Components of Changes in
Accumulated Other
Comprehensive Income (after tax)
(millions)Pretax total
accumulated
other
comprehensive
income (loss)
Total tax
(provision)
benefit
After tax total
accumulated
other
comprehensive
income (loss)
Total net unrealized gains (losses) on securitiesNet unrealized losses on forecasted transactionsForeign
currency
translation
adjustment
Balance at December 31, 2023$(2,052.9)$437.2 $(1,615.7)$(1,600.8)$(14.0)$(0.9)
Other comprehensive income (loss) before reclassifications:
Investment securities(413.6)86.9 (326.7)(326.7)
Foreign currency translation adjustment(0.3)0.1 (0.2)(0.2)
Total other comprehensive income (loss) before reclassifications(413.9)87.0 (326.9)(326.7)(0.2)
Less: Reclassification adjustment for amounts realized in net income by income statement line item:
Net realized gains (losses) on securities(150.5)31.6 (118.9)(118.9)
Interest expense(0.1)(0.1)(0.1)
Total reclassification adjustment for amounts realized in net income(150.6)31.6 (119.0)(118.9)(0.1)
Total other comprehensive income (loss)(263.3)55.4 (207.9)(207.8)0.1 (0.2)
Balance at March 31, 2024$(2,316.2)$492.6 $(1,823.6)$(1,808.6)$(13.9)$(1.1)
Components of Changes in
Accumulated Other
Comprehensive Income (after tax)
(millions)Pretax total
accumulated
other
comprehensive
income (loss)
Total tax
(provision)
benefit
After tax total
accumulated
other
comprehensive
income (loss)
Total net
unrealized
gains
 (losses)
on securities
Net unrealized losses on forecasted transactions Foreign
currency
translation
adjustment
Balance at December 31, 2022$(3,556.9)$754.9 $(2,802.0)$(2,786.3)$(14.5)$(1.2)
Other comprehensive income (loss) before reclassifications:
Investment securities705.6 (148.2)557.4 557.4 
Total other comprehensive income (loss) before reclassifications705.6 (148.2)557.4 557.4 
Less: Reclassification adjustment for amounts realized in net income by income statement line item:
Net realized gains (losses) on securities(57.9)12.1 (45.8)(45.8)
Interest expense(0.1)(0.1)(0.1)
Total reclassification adjustment for amounts realized in net income(58.0)12.1 (45.9)(45.8)(0.1)
Total other comprehensive income (loss)763.6 (160.3)603.3 603.2 0.1 
Balance at March 31, 2023$(2,793.3)$594.6 $(2,198.7)$(2,183.1)$(14.4)$(1.2)
In an effort to manage interest rate risk, we entered into forecasted transactions on certain of Progressive’s debt issuances. We expect to reclassify $0.6 million (pretax) into interest expense during the next 12 months, related to net unrealized losses on these forecasted transactions (see Note 4 – Debt in our 2023 Annual Report to Shareholders for further discussion).
v3.24.1.u1
Litigation
3 Months Ended
Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]  
Litigation LITIGATION
The Progressive Corporation and/or its insurance subsidiaries are named as defendants in various lawsuits arising out of claims made under insurance policies written by our insurance subsidiaries in the ordinary course of business. We consider all legal actions relating to such claims in establishing our loss and loss adjustment expense reserves.
In addition, The Progressive Corporation and/or its insurance subsidiaries are named as defendants in a number of class action or individual lawsuits that challenge certain of the operations of the subsidiaries. The nature and volume of litigation pending against The Progressive Corporation and/or its insurance subsidiaries is similar to that which was disclosed in Note 12 – Litigation in our 2023 Annual Report to Shareholders.
As of March 31, 2024, lawsuits have been certified or conditionally certified as class/collective actions in cases alleging: we improperly value total loss claims in Colorado, Georgia, Indiana, New York, and Pennsylvania; we improperly fail to pay fees and taxes associated with total losses in Michigan and New York; we improperly adjust medical bills in Washington; we improperly calculate basic economic loss as it relates to wage loss coverage in New York; we improperly fail to timely process and pay personal injury protection claims in Texas; we improperly reduce or deny first-party medical benefits in Arkansas; and that certain of our compensation practices and overtime payment practices are improper, including our classification of certain employees as exempt from overtime pay requirements. Other insurance companies face many of these same issues.
We plan to contest the pending lawsuits vigorously, but may pursue settlement negotiations in some cases, as we deem appropriate. Although outcomes of pending cases are uncertain until final disposition, we establish accruals for these lawsuits when it is probable that a loss has been or will be incurred and we can reasonably estimate potential loss exposure, which may include a range of loss. As to lawsuits for which the loss is considered neither probable nor estimable, or is considered probable but not estimable, we do not establish an accrual. Nevertheless, we continue to evaluate pending litigation to determine if any losses not deemed probable and estimable become so, at which point we would establish an accrual at either our best estimate of the loss or the lower end of the range of loss.
Lawsuits arising from insurance policies and operations, including but not limited to allegations involving claims adjustment and vehicle valuation, may be filed contemporaneously in multiple states. As of March 31, 2024, we are named as defendants in class action lawsuits pending in multiple states alleging that we improperly value total loss vehicle physical damage claims through the application of a negotiation adjustment in calculating such valuations, which includes five states in which classes have been certified, as noted above, and lawsuits styled as putative class actions pending in additional states. These lawsuits, which were filed at different times by different plaintiffs, feature certain similar claims and also include different allegations and are subject to various state laws. While we believe we have meritorious defenses and we are vigorously contesting these lawsuits, an unfavorable result in, or a settlement of, a significant number of these lawsuits could, in aggregation, have a material adverse effect on our financial condition, cash flows, and/or results of operations. Based on information known at March 31, 2024, we determined that losses from these lawsuits are reasonably possible but neither probable nor reasonably estimable.
With respect to our pending lawsuits that are not related to claims under insurance policies, the accruals that we have established, if any, were not material at March 31, 2024 and 2023, or December 31, 2023, and there were no material settlements during 2023 or the first three months of 2024. For most of these lawsuits, we do not consider any losses to be both probable and estimable, and we are unable to estimate a meaningful range of loss, if any, at this time, due to the factors discussed in Note 12 – Litigation in our 2023 Annual Report to Shareholders. In the event that any one or more of these lawsuits results in a substantial judgment against us, or settlement by us, or if our accruals (if any) prove to be inadequate, the resulting liability could have a material adverse effect on our consolidated financial condition, cash flows, and/or results of operations. For a further discussion on our pending litigation and related reserving policies, see Note 12 – Litigation in our 2023 Annual Report to Shareholders.
v3.24.1.u1
Pay vs Performance Disclosure - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Pay vs Performance Disclosure    
Net income $ 2,331.4 $ 447.9
v3.24.1.u1
Insider Trading Arrangements
3 Months Ended
Mar. 31, 2024
shares
Trading Arrangements, by Individual  
Non-Rule 10b5-1 Arrangement Adopted false
Rule 10b5-1 Arrangement Terminated false
Non-Rule 10b5-1 Arrangement Terminated false
Lori Niederst [Member]  
Trading Arrangements, by Individual  
Name Lori Niederst
Title Customer Relationship Management President
Rule 10b5-1 Arrangement Adopted true
Adoption Date 2/28/2024
Termination Date 12/31/2024
Arrangement Duration 307 days
Aggregate Available 0
Susan Patricia Griffith [Member]  
Trading Arrangements, by Individual  
Name Susan Patricia Griffith
Title President and Chief Executive Officer
Rule 10b5-1 Arrangement Adopted true
Adoption Date 2/28/2024
Termination Date 2/28/2025
Arrangement Duration 366 days
Aggregate Available 13,359
Andrew J. Quigg [Member]  
Trading Arrangements, by Individual  
Name Andrew J. Quigg
Title Chief Strategy Officer
Rule 10b5-1 Arrangement Adopted true
Adoption Date 1/25/2024
Termination Date 2/3/2025
Arrangement Duration 341 days
Aggregate Available 0
Steven A. Broz [Member]  
Trading Arrangements, by Individual  
Name Steven A. Broz
Title Chief Information Officer
Rule 10b5-1 Arrangement Adopted true
Adoption Date 1/26/2024
Termination Date 11/1/2024
Arrangement Duration 280 days
Aggregate Available 16,511
John P. Sauerland [Member]  
Trading Arrangements, by Individual  
Name John P. Sauerland
Title Vice President and Chief Financial Officer
Rule 10b5-1 Arrangement Adopted true
Adoption Date 2/28/2024
Termination Date 2/28/2025
Arrangement Duration 366 days
Aggregate Available 20,000
Jonathan S. Bauer [Member]  
Trading Arrangements, by Individual  
Name Jonathan S. Bauer
Title Chief Investment Officer
Rule 10b5-1 Arrangement Adopted true
Adoption Date 3/18/2024
Termination Date 9/3/2024
Arrangement Duration 169 days
Aggregate Available 2,047
Officer Trading Arrangement [Member]  
Trading Arrangements, by Individual  
Material Terms of Trading Arrangement Below are the details of each executive's Rule 10b5-1 trading arrangement:
Executive OfficerTitleDate EnteredDate Expires*Additional Shares
Jonathan S. BauerChief Investment Officer3/18/20249/3/20242,047 
Steven A. BrozChief Information Officer1/26/202411/1/202416,511 
Susan Patricia GriffithPresident and Chief Executive Officer2/28/20242/28/202513,359 
Lori NiederstCustomer Relationship Management President2/28/202412/31/2024
Andrew J. QuiggChief Strategy Officer1/25/20242/3/2025
John P. SauerlandVice President and Chief Financial Officer2/28/20242/28/202520,000 
* subject to the plan’s earlier expiration or completion in accordance with its terms.
v3.24.1.u1
Basis of Presentation (Policies)
3 Months Ended
Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Earnings Per Share To determine net income available to common shareholders, which is used in the calculation of the per common share amounts, we reduced net income by preferred share dividends, and, for 2024,
underwriting discounts and commissions on the preferred share issuance,
initial issuance costs related to the preferred shares, and
excise taxes related to the preferred share redemption.
New Accounting Standards
New Accounting Standards
On January 1, 2024, we started to amortize the remaining original cost of tax equity investments to the provision for income taxes, since certain conditions were met, on the modified retrospective basis, pursuant to an Accounting Standards Update (ASU) issued by the Financial Accounting Standards Board. Previously, these investments were accounted for under the equity method of accounting. The adoption of the ASU had no cumulative effect on retained earnings and did not have a material impact on our financial condition or results of operations. The amount of income tax credits and investment amortization recognized for the first quarter 2024, and the carrying amount of the tax credit investments at March 31, 2024, were not material to our financial condition or results of operations and, therefore, no additional disclosure is provided.
v3.24.1.u1
Basis of Presentation (Tables)
3 Months Ended
Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Premium Receivable, Allowance for Credit Loss The following table summarizes changes in our allowance for credit loss exposure on our premiums receivable:
Three Months Ended March 31,
(millions)20242023
Allowance for credit losses, beginning of period$369.1 $343.3 
Increase in allowance1
106.8 116.9 
Write-offs2
(148.2)(119.3)
Allowance for credit losses, end of period$327.7 $340.9 
1 Represents the incremental increase in other underwriting expenses.
2 Represents the portion of allowance that is reversed when the premiums receivable is written off. Premiums receivable balances are written off once we have exhausted our collection efforts.
v3.24.1.u1
Investments (Tables)
3 Months Ended
Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract]  
Schedule of Debt and Equity Securities Reconciliation
The following tables present the composition of our investment portfolio by major security type. Our securities are reported in our consolidated balance sheets at fair value. The changes in fair value for our fixed-maturity securities (other than hybrid securities) are reported as a component of accumulated other comprehensive income (loss), net of deferred income taxes, in our consolidated
balance sheets. The net holding period gains (losses) reported below represent the inception-to-date changes in fair value for the hybrid and equity securities. The changes in the net holding period gains (losses) between periods are recorded as a component of net realized gains (losses) on securities in our consolidated statements of comprehensive income.
($ in millions)CostGross
Unrealized
Gains
Gross
Unrealized
Losses
Net
Holding
Period
Gains
(Losses)
Fair
Value
% of
Total
Fair
Value
March 31, 2024
Available-for-sale securities:
Fixed maturities:
U.S. government obligations$39,823.8 $66.2 $(1,327.3)$$38,562.7 55.8 %
State and local government obligations2,200.7 1.5 (142.4)2,059.8 3.0 
Foreign government obligations16.9 (1.0)15.9 0.1 
Corporate debt securities12,821.9 45.9 (328.1)(18.4)12,521.3 18.1 
Residential mortgage-backed securities390.1 0.2 (9.2)2.0 383.1 0.6 
Commercial mortgage-backed securities4,368.6 2.5 (519.3)3,851.8 5.6 
Other asset-backed securities6,146.1 9.2 (93.9)(0.2)6,061.2 8.8 
Redeemable preferred stocks181.2 (2.0)(5.3)173.9 0.2 
Total fixed maturities65,949.3 125.5 (2,423.2)(21.9)63,629.7 92.2 
Short-term investments1,326.7 1,326.7 1.9 
Total available-for-sale securities67,276.0 125.5 (2,423.2)(21.9)64,956.4 94.1 
Equity securities:
Nonredeemable preferred stocks931.1 (44.4)886.7 1.3 
Common equities708.2 2,486.7 3,194.9 4.6 
Total equity securities1,639.3 2,442.3 4,081.6 5.9 
Total portfolio1
$68,915.3 $125.5 $(2,423.2)$2,420.4 $69,038.0 100.0 %
($ in millions)CostGross
Unrealized
Gains
Gross
Unrealized
Losses
Net
Holding
Period
Gains
(Losses)
Fair
Value
% of
Total
Fair
Value
March 31, 2023
Available-for-sale securities:
Fixed maturities:
U.S. government obligations$28,490.9 $68.8 $(1,209.6)$$27,350.1 48.3 %
State and local government obligations2,222.4 0.9 (161.7)2,061.6 3.6 
Foreign government obligations16.9 (1.1)15.8 0.1 
Corporate debt securities11,195.8 45.6 (525.4)(34.7)10,681.3 18.8 
Residential mortgage-backed securities655.0 0.2 (16.3)(8.9)630.0 1.1 
Commercial mortgage-backed securities5,252.6 1.6 (751.2)4,503.0 7.9 
Other asset-backed securities5,087.8 1.8 (222.5)(1.3)4,865.8 8.6 
Redeemable preferred stocks202.5 (5.2)(15.7)181.6 0.3 
Total fixed maturities53,123.9 118.9 (2,893.0)(60.6)50,289.2 88.7 
Short-term investments2,524.1 2,524.1 4.5 
Total available-for-sale securities55,648.0 118.9 (2,893.0)(60.6)52,813.3 93.2 
Equity securities:
Nonredeemable preferred stocks1,197.7 (118.9)1,078.8 1.9 
Common equities740.5 2,053.8 2,794.3 4.9 
Total equity securities1,938.2 1,934.9 3,873.1 6.8 
Total portfolio1
$57,586.2 $118.9 $(2,893.0)$1,874.3 $56,686.4 100.0 %


($ in millions)CostGross
Unrealized
Gains
Gross
Unrealized
Losses
Net
Holding
Period
Gains
(Losses)
Fair
Value
% of
Total
Fair
Value
December 31, 2023
Available-for-sale securities:
Fixed maturities:
U.S. government obligations$37,823.2 $204.1 $(1,157.9)$$36,869.4 55.9 %
State and local government obligations2,338.4 2.8 (138.4)2,202.8 3.3 
Foreign government obligations17.3 (1.0)16.3 0.1 
Corporate debt securities11,446.0 87.2 (332.3)(17.2)11,183.7 16.9 
Residential mortgage-backed securities426.9 0.2 (10.0)0.1 417.2 0.6 
Commercial mortgage-backed securities4,535.2 2.2 (597.7)3,939.7 6.0 
Other asset-backed securities5,667.2 15.7 (107.1)(0.4)5,575.4 8.4 
Redeemable preferred stocks187.7 (2.4)(11.6)173.7 0.3 
Total fixed maturities62,441.9 312.2 (2,346.8)(29.1)60,378.2 91.5 
Short-term investments1,789.9 1,789.9 2.7 
Total available-for-sale securities64,231.8 312.2 (2,346.8)(29.1)62,168.1 94.2 
Equity securities:
Nonredeemable preferred stocks977.1 (75.0)902.1 1.4 
Common equities706.0 2,222.4 2,928.4 4.4 
Total equity securities1,683.1 2,147.4 3,830.5 5.8 
Total portfolio1
$65,914.9 $312.2 $(2,346.8)$2,118.3 $65,998.6 100.0 %
1 At March 31, 2024 and 2023, we had $16.2 million and $22.8 million, respectively, of net unsettled security purchase transactions included in other liabilities, compared to $45.6 million included in other assets at December 31, 2023.
The total fair value of the portfolio at March 31, 2024 and 2023, and December 31, 2023, included $3.2 billion, $4.1 billion, and $4.2 billion, respectively, of securities held in a consolidated, non-insurance subsidiary of the holding company, net of unsettled security transactions.
Hybrid Instruments Table Certain securities in our fixed-maturity portfolio are accounted for as hybrid securities because they contain embedded derivatives that are not deemed to be clearly and closely related to the host investments. These securities are reported at fair value:
 March 31,
(millions)20242023Dec. 31, 2023
Fixed Maturities:
Corporate debt securities$507.1 $548.6 $531.3 
Residential mortgage-backed securities300.0 482.1 323.9 
Other asset-backed securities9.5 33.8 13.9 
Redeemable preferred stocks141.0 132.8 141.2 
Total hybrid securities$957.6 $1,197.3 $1,010.3 
Investments Classified by Contractual Maturity Date The composition of fixed maturities by maturity at March 31, 2024, was:
(millions)CostFair Value
Less than one year$7,227.5 $7,084.8 
One to five years45,277.4 43,850.9 
Five to ten years13,394.2 12,645.2 
Ten years or greater50.2 48.8 
Total$65,949.3 $63,629.7 
Schedule of Unrealized Loss on Investments The following tables show the composition of gross unrealized losses by major security type and by the length of time that individual securities have been in a continuous unrealized loss position:
 Total No. of Sec.Total
Fair
Value
Gross
Unrealized
Losses
Less than 12 Months12 Months or Greater
($ in millions)No. of Sec.Fair
Value
Unrealized
Losses
No. of Sec.Fair
 Value
Unrealized
Losses
March 31, 2024
U.S. government obligations139 $32,968.1 $(1,327.3)37 $21,634.6 $(295.1)102 $11,333.5 $(1,032.2)
State and local government obligations330 1,922.7 (142.4)41 250.7 (1.8)289 1,672.0 (140.6)
Foreign government obligations15.9 (1.0)15.9 (1.0)
Corporate debt securities363 8,094.3 (328.1)106 2,369.6 (20.6)257 5,724.7 (307.5)
Residential mortgage-backed securities35 78.0 (9.2)34 78.0 (9.2)
Commercial mortgage-backed securities181 3,741.7 (519.3)190.5 (1.8)177 3,551.2 (517.5)
Other asset-backed securities193 3,259.5 (93.9)59 1,303.5 (2.3)134 1,956.0 (91.6)
Redeemable preferred stocks32.9 (2.0)32.9 (2.0)
Total fixed maturities1,245 $50,113.1 $(2,423.2)248 $25,748.9 $(321.6)997 $24,364.2 $(2,101.6)
 Total No. of Sec.Total
Fair
Value
Gross
Unrealized
Losses
Less than 12 Months12 Months or Greater
($ in millions)No. of Sec.Fair
Value
Unrealized
Losses
No. of Sec.Fair
 Value
Unrealized
Losses
March 31, 2023
U.S. government obligations148 $19,446.8 $(1,209.6)40 $5,938.5 $(127.5)108 $13,508.3 $(1,082.1)
State and local government obligations343 1,943.6 (161.7)72 350.7 (7.4)271 1,592.9 (154.3)
Foreign government obligations15.8 (1.1)15.8 (1.1)
Corporate debt securities390 8,129.9 (525.4)93 2,239.3 (75.5)297 5,890.6 (449.9)
Residential mortgage-backed securities43 141.7 (16.3)13 10.0 (0.4)30 131.7 (15.9)
Commercial mortgage-backed securities220 4,484.5 (751.2)11 53.4 (1.5)209 4,431.1 (749.7)
Other asset-backed securities267 4,391.9 (222.5)61 884.8 (6.2)206 3,507.1 (216.3)
Redeemable preferred stocks48.8 (5.2)10.6 (1.4)38.2 (3.8)
Total fixed maturities1,416 $38,603.0 $(2,893.0)291 $9,487.3 $(219.9)1,125 $29,115.7 $(2,673.1)

 Total No. of Sec.Total
Fair
Value
Gross
Unrealized
Losses
Less than 12 Months12 Months or Greater
($ in millions)No. of Sec.Fair
Value
Unrealized
Losses
No. of Sec.Fair
 Value
Unrealized
Losses
December 31, 2023
U.S. government obligations147 $28,225.0 $(1,157.9)25 $11,890.0 $(100.0)122 $16,335.0 $(1,057.9)
State and local government obligations324 1,846.2 (138.4)31 169.9 (0.9)293 1,676.3 (137.5)
Foreign government obligations16.3 (1.0)16.3 (1.0)
Corporate debt securities313 6,642.4 (332.3)26 617.2 (14.7)287 6,025.2 (317.6)
Residential mortgage-backed securities39 88.4 (10.0)0.4 37 88.0 (10.0)
Commercial mortgage-backed securities189 3,912.2 (597.7)30.7 (2.5)188 3,881.5 (595.2)
Other asset-backed securities207 3,299.1 (107.1)41 639.4 (1.2)166 2,659.7 (105.9)
Redeemable preferred stocks32.5 (2.4)32.5 (2.4)
Total fixed maturities1,223 $44,062.1 $(2,346.8)126 $13,347.6 $(119.3)1,097 $30,714.5 $(2,227.5)
Realized Gain (Loss) on Investments The components of net realized gains (losses) for the three months ended March 31, were:
 Three Months
(millions)20242023
Gross realized gains on security sales
Available-for-sale securities:
U.S. government obligations$$3.8 
State and local government obligations0.3 
Corporate debt securities2.9 0.1 
Total available-for-sale securities3.2 3.9 
Equity securities:
Nonredeemable preferred stocks0.1 
Common equities11.2 132.0 
Total equity securities11.2 132.1 
Subtotal gross realized gains on security sales14.4 136.0 
Gross realized losses on security sales
Available-for-sale securities:
U.S. government obligations(135.3)(11.5)
State and local government obligations(0.1)
Corporate debt securities(14.8)(20.4)
Commercial mortgage-backed securities(4.3)(34.5)
Other asset-backed securities(0.1)(0.2)
Redeemable preferred stocks(0.3)
Short-term investments(0.1)
Total available-for-sale securities(154.9)(66.7)
Equity securities:
Nonredeemable preferred stocks(5.9)(101.0)
Common equities(0.1)(11.8)
Total equity securities(6.0)(112.8)
Subtotal gross realized losses on security sales(160.9)(179.5)
Net realized gains (losses) on security sales
Available-for-sale securities:
U.S. government obligations(135.3)(7.7)
State and local government obligations0.2 
Corporate debt securities(11.9)(20.3)
Commercial mortgage-backed securities(4.3)(34.5)
Other asset-backed securities(0.1)(0.2)
Redeemable preferred stocks(0.3)
Short-term investments(0.1)
Total available-for-sale securities(151.7)(62.8)
Equity securities:
Nonredeemable preferred stocks(5.9)(100.9)
Common equities11.1 120.2 
Total equity securities5.2 19.3 
Subtotal net realized gains (losses) on security sales(146.5)(43.5)
Other assets
Gain13.2 
Impairment(2.3)
Subtotal net realized gains (losses) on other assets10.9 
Net holding period gains (losses)
Hybrid securities7.2 13.9 
Equity securities294.9 90.5 
Subtotal net holding period gains (losses)302.1 104.4 
Total net realized gains (losses) on securities$155.6 $71.8 
Components of Equity Realized Gains (Losses)
The following table reflects our holding period realized gains (losses) recognized on equity securities held at the respective periods ended March 31:
Three Months
(millions)20242023
Total net gains (losses) recognized during the period on equity securities$300.1 $109.8 
Less: Net gains (losses) recognized on equity securities sold during the period5.2 19.3 
Net holding period gains (losses) recognized during the period on equity securities held at period end$294.9 $90.5 
Components of Net Investment Income The components of net investment income for the three months ended March 31, were: 
Three Months
(millions)20242023
Available-for-sale securities:
Fixed maturities:
U.S. government obligations$306.9 $163.2 
State and local government obligations12.4 10.6 
Foreign government obligations0.1 0.1 
Corporate debt securities121.5 83.6 
Residential mortgage-backed securities5.4 9.2 
Commercial mortgage-backed securities46.4 50.0 
Other asset-backed securities78.2 48.5 
Redeemable preferred stocks2.9 2.9 
Total fixed maturities573.8 368.1 
Short-term investments18.9 24.7 
Total available-for-sale securities592.7 392.8 
Equity securities:
Nonredeemable preferred stocks11.0 15.1 
Common equities13.9 11.7 
Total equity securities24.9 26.8 
Investment income617.6 419.6 
Investment expenses(5.7)(5.5)
Net investment income$611.9 $414.1 
v3.24.1.u1
Fair Value (Tables)
3 Months Ended
Mar. 31, 2024
Fair Value Disclosures [Abstract]  
Composition of Investment Portfolio by Major Security Type
The composition of the investment portfolio by major security type and our outstanding debt was:
 Fair Value 
(millions)Level 1Level 2Level 3TotalCost
March 31, 2024
Fixed maturities:
U.S. government obligations$38,562.7 $$$38,562.7 $39,823.8 
State and local government obligations2,059.8 2,059.8 2,200.7 
Foreign government obligations15.9 15.9 16.9 
Corporate debt securities12,518.3 3.0 12,521.3 12,821.9 
Subtotal38,562.7 14,594.0 3.0 53,159.7 54,863.3 
Asset-backed securities:
Residential mortgage-backed383.1 383.1 390.1 
Commercial mortgage-backed3,851.8 3,851.8 4,368.6 
Other asset-backed6,061.2 6,061.2 6,146.1 
Subtotal asset-backed securities10,296.1 10,296.1 10,904.8 
Redeemable preferred stocks:
Financials23.2 23.2 24.5 
Utilities9.6 9.6 10.4 
Industrials141.1 141.1 146.3 
Subtotal redeemable preferred stocks173.9 173.9 181.2 
Total fixed maturities38,562.7 25,064.0 3.0 63,629.7 65,949.3 
Short-term investments1,326.7 1,326.7 1,326.7 
    Total available-for-sale securities39,889.4 25,064.0 3.0 64,956.4 67,276.0 
Equity securities:
Nonredeemable preferred stocks:
Financials785.3 49.2 834.5 876.1 
Utilities37.4 37.4 40.0 
Industrials14.8 14.8 15.0 
Subtotal nonredeemable preferred stocks822.7 64.0 886.7 931.1 
Common equities:
Common stocks3,148.1 22.5 3,170.6 683.9 
Other risk investments24.3 24.3 24.3 
Subtotal common equities3,148.1 46.8 3,194.9 708.2 
    Total equity securities3,148.1 822.7 110.8 4,081.6 1,639.3 
Total portfolio$43,037.5 $25,886.7 $113.8 $69,038.0 $68,915.3 
Debt$$6,297.8 $$6,297.8 $6,889.7 
 Fair Value 
(millions)Level 1Level 2Level 3TotalCost
March 31, 2023
Fixed maturities:
U.S. government obligations$27,350.1 $$$27,350.1 $28,490.9 
State and local government obligations2,061.6 2,061.6 2,222.4 
Foreign government obligations15.8 15.8 16.9 
Corporate debt securities10,681.3 10,681.3 11,195.8 
Subtotal27,350.1 12,758.7 40,108.8 41,926.0 
Asset-backed securities:
Residential mortgage-backed630.0 630.0 655.0 
Commercial mortgage-backed4,503.0 4,503.0 5,252.6 
Other asset-backed4,865.8 4,865.8 5,087.8 
Subtotal asset-backed securities9,998.8 9,998.8 10,995.4 
Redeemable preferred stocks:
Financials40.0 40.0 43.5 
Utilities8.8 8.8 10.5 
Industrials9.6 123.2 132.8 148.5 
Subtotal redeemable preferred stocks9.6 172.0 181.6 202.5 
Total fixed maturities27,359.7 22,929.5 50,289.2 53,123.9 
Short-term investments2,524.1 2,524.1 2,524.1 
    Total available-for-sale securities29,883.8 22,929.5 52,813.3 55,648.0 
Equity securities:
Nonredeemable preferred stocks:
Financials40.0 884.5 67.4 991.9 1,102.7 
Utilities70.5 70.5 80.0 
Industrials16.4 16.4 15.0 
Subtotal nonredeemable preferred stocks40.0 955.0 83.8 1,078.8 1,197.7 
Common equities:
Common stocks2,755.7 18.3 2,774.0 720.2 
Other risk investments20.3 20.3 20.3 
Subtotal common equities2,755.7 38.6 2,794.3 740.5 
    Total equity securities2,795.7 955.0 122.4 3,873.1 1,938.2 
Total portfolio$32,679.5 $23,884.5 $122.4 $56,686.4 $57,586.2 
Debt$$5,881.0 $$5,881.0 $6,389.3 
 Fair Value 
(millions)Level 1Level 2Level 3TotalCost
December 31, 2023
Fixed maturities:
U.S. government obligations$36,869.4 $$$36,869.4 $37,823.2 
State and local government obligations2,202.8 2,202.8 2,338.4 
Foreign government obligations16.3 16.3 17.3 
Corporate debt securities11,180.7 3.0 11,183.7 11,446.0 
Subtotal36,869.4 13,399.8 3.0 50,272.2 51,624.9 
Asset-backed securities:
Residential mortgage-backed417.2 417.2 426.9 
Commercial mortgage-backed3,939.7 3,939.7 4,535.2 
Other asset-backed5,575.4 5,575.4 5,667.2 
Subtotal asset-backed securities9,932.3 9,932.3 10,629.3 
Redeemable preferred stocks:
Financials23.1 23.1 24.5 
Utilities9.4 9.4 10.4 
Industrials141.2 141.2 152.8 
Subtotal redeemable preferred stocks173.7 173.7 187.7 
Total fixed maturities36,869.4 23,505.8 3.0 60,378.2 62,441.9 
Short-term investments1,757.0 32.9 1,789.9 1,789.9 
    Total available-for-sale securities38,626.4 23,538.7 3.0 62,168.1 64,231.8 
Equity securities:
Nonredeemable preferred stocks:
Financials802.7 49.2 851.9 922.1 
Utilities35.4 35.4 40.0 
Industrials14.8 14.8 15.0 
Subtotal nonredeemable preferred stocks838.1 64.0 902.1 977.1 
Common equities:
Common stocks2,885.3 22.5 2,907.8 685.4 
Other risk investments20.6 20.6 20.6 
Subtotal common equities2,885.3 43.1 2,928.4 706.0 
    Total equity securities2,885.3 838.1 107.1 3,830.5 1,683.1 
Total portfolio$41,511.7 $24,376.8 $110.1 $65,998.6 $65,914.9 
Debt$$6,431.3 $$6,431.3 $6,888.6 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation
The following tables provide a summary of changes in fair value associated with Level 3 assets for the three months ended March 31, 2024 and 2023:
Level 3 Fair Value
(millions)Fair Value at December 31, 2023Calls/
Maturities/
Paydowns/Other
PurchasesSalesNet Realized
(Gain)/Loss
on Sales
Change in
Valuation
Net
Transfers
In (Out)
Fair Value at March 31, 2024
Fixed maturities:
Corporate debt securities$3.0 $$$$$$$3.0 
Equity securities:
Nonredeemable preferred stocks:
Financials
49.2 49.2 
Industrials
14.8 14.8 
Common equities:
Common stocks22.5 22.5 
Other risk investments20.6 3.7 24.3 
Total Level 3 securities$110.1 $3.7 $$$$$$113.8 
Level 3 Fair Value
(millions)Fair Value at December 31, 2022Calls/
Maturities/
Paydowns/Other
PurchasesSalesNet Realized
(Gain)/Loss
on Sales
Change in
Valuation
Net
Transfers
In (Out)
Fair Value at March 31, 2023
Equity securities:
Nonredeemable preferred stocks:
Financials
$67.4 $$$$$$$67.4 
Industrials
16.4 16.4 
Common equities:
Common stocks18.3 18.3 
Other risk investments19.8 0.5 20.3 
Total Level 3 securities
$121.9 $0.5 $$$$$$122.4 
Fair Value Measurement Inputs and Valuation Techniques
The following tables provide a summary of the quantitative information about Level 3 fair value measurements for our applicable securities at March 31, 2024 and 2023, and December 31, 2023:
Quantitative Information about Level 3 Fair Value Measurements
($ in millions)Fair Value at March 31, 2024Valuation TechniqueUnobservable InputRange of Input Values Increase (Decrease)Weighted Average Increase (Decrease)
Fixed maturities:
Corporate debt securities$3.0 Market comparablesWeighted average market capitalization price change %
(2.3)% to 1.2%
(0.1)%
Equity securities:
Nonredeemable preferred stocks64.0 Market comparablesWeighted average market capitalization price change %
3.4% to 28.4%
22.6 %
Common stocks22.5 Market comparablesWeighted average market capitalization price change %
(37.9)% to 39.6%
3.4 %
Subtotal Level 3 securities89.5 
Pricing exemption securities24.3 
Total Level 3 securities$113.8 


Quantitative Information about Level 3 Fair Value Measurements
($ in millions)Fair Value at March 31, 2023Valuation TechniqueUnobservable InputRange of Input Values Increase (Decrease)Weighted Average Increase (Decrease)
Equity securities:
Nonredeemable preferred stocks$83.8 Market comparablesWeighted average market capitalization price change %
2.7% to 23.3%
9.2 %
Common stocks18.3 Market comparablesWeighted average market capitalization price change %
(51.3)% to 48.3%
15.6 %
Subtotal Level 3 securities102.1 
Pricing exemption securities20.3 
Total Level 3 securities$122.4 


Quantitative Information about Level 3 Fair Value Measurements
($ in millions)Fair Value at December 31, 2023Valuation TechniqueUnobservable InputRange of Input Values Increase (Decrease)Weighted Average Increase (Decrease)
Fixed maturities:
Corporate debt securities$3.0 Market comparablesWeighted average market capitalization price change %
0.3% to 7.7%
2.6 %
Equity securities:
Nonredeemable preferred stocks64.0 Market comparablesWeighted average market capitalization price change %
17.2% to 39.7%
21.7%
Common stocks22.5 Market comparablesWeighted average market capitalization price change %
(45.8)% to 95.6%
39.7%
Subtotal Level 3 securities89.5 
Pricing exemption securities20.6 
Total Level 3 securities$110.1 
v3.24.1.u1
Debt (Tables)
3 Months Ended
Mar. 31, 2024
Debt Disclosure [Abstract]  
Debt Table
Debt at each of the balance sheet periods consisted of:
 March 31, 2024March 31, 2023December 31, 2023
(millions)Carrying
Value
Fair
Value
Carrying
Value
Fair
Value
Carrying
Value
Fair
Value
2.45% Senior Notes due 2027 (issued: $500.0, August 2016)
$498.7 $468.6 $498.3 $464.2 $498.6 $468.9 
2.50% Senior Notes due 2027 (issued: $500.0, March 2022)
498.2 468.5 497.7 463.8 498.1 469.1 
6 5/8% Senior Notes due 2029 (issued: $300.0, March 1999)
297.9 323.5 297.6 329.6 297.8 328.7 
4.00% Senior Notes due 2029 (issued: $550.0, October 2018)
547.1 532.5 546.5 538.5 546.9 542.6 
3.20% Senior Notes due 2030 (issued: $500.0, March 2020)
497.4 456.1 497.0 460.0 497.3 462.2 
3.00% Senior Notes due 2032 (issued: $500.0, March 2022)
496.4 435.7 496.0 446.9 496.3 446.0 
6.25% Senior Notes due 2032 (issued: $400.0, November 2002)
396.8 434.2 396.5 448.1 396.7 445.6 
4.95% Senior Notes due 2033 (issued: $500.0, May 2023)
496.5 499.2 496.4 513.0 
4.35% Senior Notes due 2044 (issued: $350.0, April 2014)
347.0 312.8 346.9 312.3 347.0 314.2 
3.70% Senior Notes due 2045 (issued: $400.0, January 2015)
395.9 327.9 395.8 324.0 395.9 325.1 
4.125% Senior Notes due 2047 (issued: $850.0, April 2017)
842.3 719.2 842.1 743.8 842.3 756.2 
4.20% Senior Notes due 2048 (issued: $600.0, March 2018)
590.7 519.8 590.4 530.0 590.6 534.1 
3.95% Senior Notes due 2050 (issued: $500.0, March 2020)
491.2 409.8 491.0 420.3 491.1 422.3 
3.70% Senior Notes due 2052 (issued: $500.0, March 2022)
493.6 390.0 493.5 399.5 493.6 403.3 
Total$6,889.7 $6,297.8 $6,389.3 $5,881.0 $6,888.6 $6,431.3 
v3.24.1.u1
Loss and Loss Adjustment Expense Reserves (Tables)
3 Months Ended
Mar. 31, 2024
Loss and Loss Adjustment Expenses Reserves [Abstract]  
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense
Activity in the loss and loss adjustment expense reserves is summarized as follows:
March 31,
(millions)20242023
Balance at January 1$34,389.2 $30,359.3 
Less reinsurance recoverables on unpaid losses4,789.0 5,559.2 
Net balance at January 129,600.2 24,800.1 
Incurred related to:
Current year10,983.0 10,002.8 
Prior years(11.4)621.2 
Total incurred10,971.6 10,624.0 
Paid related to:
Current year4,421.7 3,962.6 
Prior years5,971.0 5,736.2 
Total paid10,392.7 9,698.8 
Net balance at March 31
30,179.1 25,725.3 
Plus reinsurance recoverables on unpaid losses4,651.9 5,301.1 
Balance at March 31
$34,831.0 $31,026.4 
v3.24.1.u1
Supplemental Cash Flow Information (Tables)
3 Months Ended
Mar. 31, 2024
Supplemental Cash Flow Elements [Abstract]  
Schedule of Supplemental Cash Flow Information, Non Cash Activity
Non-cash activity included the following in the respective periods:
Three Months Ended March 31,
(millions)20242023
Common share dividends1
$58.6 $58.5 
Operating lease liabilities2
28.0 9.3 
1 Declared but unpaid. See Note 9 – Dividends for further discussion.
2 From obtaining right-of-use assets.
Supplemental Cash Flow Information Table
In the respective periods, we paid the following: 
 Three Months Ended March 31,
(millions)20242023
Income taxes$$0.1 
Interest87.9 87.9 
Operating lease liabilities21.6 21.5 
v3.24.1.u1
Segment Information (Tables)
3 Months Ended
Mar. 31, 2024
Segment Reporting [Abstract]  
Reconciliation of Revenue and operating Income from Segments to Consolidated
Following are the operating results for the respective periods:
 Three Months Ended March 31,
 20242023
(millions)RevenuesPretax
Profit (Loss)
RevenuesPretax
Profit (Loss)
Personal Lines
Agency$5,857.7 $950.7 $4,860.2 $162.6 
Direct7,020.5 1,043.6 5,717.4 (22.1)
Total Personal Lines1
12,878.2 1,994.3 10,577.6 140.5 
Commercial Lines2,557.4 209.0 2,356.1 37.2 
Property712.8 46.9 598.7 (32.7)
Other indemnity2
0.2 (0.3)0.7 (3.4)
Total underwriting operations16,148.6 2,249.9 13,533.1 141.6 
Fees and other revenues3
236.5 NA206.2 NA
Service businesses84.2 (7.9)72.5 (9.8)
Investments4
773.2 767.5 491.4 485.9 
Interest expenseNA(69.6)NA(63.3)
Consolidated total$17,242.5 $2,939.9 $14,303.2 $554.4 
NA = Not applicable
1 Personal auto insurance accounted for 95% and 94% of the total Personal Lines segment net premiums earned during the three months ended March 31, 2024 and 2023, respectively; insurance for our special lines products (e.g., motorcycles, RVs, watercraft, and snowmobiles) accounted for the balance of the Personal Lines net premiums earned.
2 Includes other underwriting business and run-off operations.
3 Pretax profit (loss) for fees and other revenues is allocated to operating segments based on revenue.
4 Revenues represent recurring investment income and total net realized gains (losses) on securities; pretax profit (loss) is net of investment expenses.
Underwriting Margins and Combined Ratios for our Underwriting Operations Following are the underwriting margins and combined ratios for our underwriting operations for the respective periods:
 Three Months Ended March 31,
 20242023
 Under-writing
Margin
Combined
Ratio
Under-writing
Margin
Combined
Ratio
Personal Lines
Agency16.2 %83.8 3.3 %96.7 
Direct14.9 85.1 (0.4)100.4 
Total Personal Lines15.5 84.5 1.3 98.7 
Commercial Lines8.2 91.8 1.6 98.4 
Property6.6 93.4 (5.5)105.5 
Total underwriting operations13.9 86.1 1.0 99.0 
v3.24.1.u1
Dividends (Tables)
3 Months Ended
Mar. 31, 2024
Dividends [Abstract]  
Dividends
Following is a summary of our common and preferred share dividends that were declared and/or paid during the three months ended March 31, 2024 and 2023:
(millions, except per share amounts)Amount
DeclaredPayablePer Share
Accrued/Paid1
Common – Annual-Variable Dividends:
December 2023January 2024$0.75 $439.3 
Common – Quarterly Dividends:
March 2024April 20240.10 58.6 
December 2023January 20240.10 58.6 
March 2023April 20230.10 58.5 
December 2022January 20230.10 58.5 
Preferred Dividends:
January 20242
February 202415.688377 7.8 
December 2022March 202326.875 13.4 
1 The accrual is based on an estimate of shares outstanding as of the record date and recorded as a component of accounts payable, accrued expenses, and other liabilities on our consolidated balance sheets until paid.
2
v3.24.1.u1
Other Comprehensive Income (Loss) (Tables)
3 Months Ended
Mar. 31, 2024
Equity [Abstract]  
Components of Other Comprehensive Income (Loss)
The components of other comprehensive income (loss), including reclassification adjustments by income statement line item, were as follows: 
    Components of Changes in
Accumulated Other
Comprehensive Income (after tax)
(millions)Pretax total
accumulated
other
comprehensive
income (loss)
Total tax
(provision)
benefit
After tax total
accumulated
other
comprehensive
income (loss)
Total net unrealized gains (losses) on securitiesNet unrealized losses on forecasted transactionsForeign
currency
translation
adjustment
Balance at December 31, 2023$(2,052.9)$437.2 $(1,615.7)$(1,600.8)$(14.0)$(0.9)
Other comprehensive income (loss) before reclassifications:
Investment securities(413.6)86.9 (326.7)(326.7)
Foreign currency translation adjustment(0.3)0.1 (0.2)(0.2)
Total other comprehensive income (loss) before reclassifications(413.9)87.0 (326.9)(326.7)(0.2)
Less: Reclassification adjustment for amounts realized in net income by income statement line item:
Net realized gains (losses) on securities(150.5)31.6 (118.9)(118.9)
Interest expense(0.1)(0.1)(0.1)
Total reclassification adjustment for amounts realized in net income(150.6)31.6 (119.0)(118.9)(0.1)
Total other comprehensive income (loss)(263.3)55.4 (207.9)(207.8)0.1 (0.2)
Balance at March 31, 2024$(2,316.2)$492.6 $(1,823.6)$(1,808.6)$(13.9)$(1.1)
Components of Changes in
Accumulated Other
Comprehensive Income (after tax)
(millions)Pretax total
accumulated
other
comprehensive
income (loss)
Total tax
(provision)
benefit
After tax total
accumulated
other
comprehensive
income (loss)
Total net
unrealized
gains
 (losses)
on securities
Net unrealized losses on forecasted transactions Foreign
currency
translation
adjustment
Balance at December 31, 2022$(3,556.9)$754.9 $(2,802.0)$(2,786.3)$(14.5)$(1.2)
Other comprehensive income (loss) before reclassifications:
Investment securities705.6 (148.2)557.4 557.4 
Total other comprehensive income (loss) before reclassifications705.6 (148.2)557.4 557.4 
Less: Reclassification adjustment for amounts realized in net income by income statement line item:
Net realized gains (losses) on securities(57.9)12.1 (45.8)(45.8)
Interest expense(0.1)(0.1)(0.1)
Total reclassification adjustment for amounts realized in net income(58.0)12.1 (45.9)(45.8)(0.1)
Total other comprehensive income (loss)763.6 (160.3)603.3 603.2 0.1 
Balance at March 31, 2023$(2,793.3)$594.6 $(2,198.7)$(2,183.1)$(14.4)$(1.2)
v3.24.1.u1
Basis of Presentation - Reporting and Accounting Policies - Allowance for Credit Loss (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Premium Receivable, Allowance for Credit Loss [Roll Forward]    
Allowance for credit losses, beginning of period $ 369.1 $ 343.3
Increase in allowance 106.8 116.9
Write-offs (148.2) (119.3)
Allowance for credit losses, end of period $ 327.7 $ 340.9
v3.24.1.u1
Basis of Presentation - Additional Information (Details) - USD ($)
$ in Millions
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]      
Assets held-for-sale $ 169.8 $ 77.2 $ 67.8
v3.24.1.u1
Investments - Investment Portfolio by Major Security Type (Detail) - USD ($)
$ in Millions
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2023
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 67,276.0 $ 64,231.8 $ 55,648.0
Gross Unrealized Gains 125.5 312.2 118.9
Gross Unrealized Losses (2,423.2) (2,346.8) (2,893.0)
Net Holding Period Gains (Losses) (21.9) (29.1) (60.6)
Total available-for-sale securities $ 64,956.4 $ 62,168.1 $ 52,813.3
% of Total Fair Value 94.10% 94.20% 93.20%
Equity securities, at Fair Value      
Cost $ 1,639.3 $ 1,683.1 $ 1,938.2
Gross Unrealized Gains 0.0 0.0 0.0
Gross Unrealized Losses 0.0 0.0 0.0
Net Holding Period Gains (Losses) 2,442.3 2,147.4 1,934.9
Fair Value $ 4,081.6 $ 3,830.5 $ 3,873.1
% of Total Fair Value 5.90% 5.80% 6.80%
Debt and Equity Securities, at Fair Value      
Cost $ 68,915.3 $ 65,914.9 $ 57,586.2
Gross Unrealized Gains 125.5 312.2 118.9
Gross Unrealized Losses (2,423.2) (2,346.8) (2,893.0)
Net Holding Period Gains (Losses) 2,420.4 2,118.3 1,874.3
Fair Value $ 69,038.0 $ 65,998.6 $ 56,686.4
% of Total Fair Value 100.00% 100.00% 100.00%
Unsettled security transactions, payable $ 16.2   $ 22.8
Other receivable from broker-dealer and clearing organization   $ 45.6  
Total fair value of non-insurance subsidiary portfolio 3,200.0 4,200.0 4,100.0
Nonredeemable preferred stocks      
Equity securities, at Fair Value      
Cost 931.1 977.1 1,197.7
Gross Unrealized Gains 0.0 0.0 0.0
Gross Unrealized Losses 0.0 0.0 0.0
Net Holding Period Gains (Losses) (44.4) (75.0) (118.9)
Fair Value $ 886.7 $ 902.1 $ 1,078.8
% of Total Fair Value 1.30% 1.40% 1.90%
Common equities      
Equity securities, at Fair Value      
Cost $ 708.2 $ 706.0 $ 740.5
Gross Unrealized Gains 0.0 0.0 0.0
Gross Unrealized Losses 0.0 0.0 0.0
Net Holding Period Gains (Losses) 2,486.7 2,222.4 2,053.8
Fair Value $ 3,194.9 $ 2,928.4 $ 2,794.3
% of Total Fair Value 4.60% 4.40% 4.90%
Total fixed maturities      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 65,949.3 $ 62,441.9 $ 53,123.9
Gross Unrealized Gains 125.5 312.2 118.9
Gross Unrealized Losses (2,423.2) (2,346.8) (2,893.0)
Net Holding Period Gains (Losses) (21.9) (29.1) (60.6)
Total available-for-sale securities $ 63,629.7 $ 60,378.2 $ 50,289.2
% of Total Fair Value 92.20% 91.50% 88.70%
Total fixed maturities | U.S. government obligations      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 39,823.8 $ 37,823.2 $ 28,490.9
Gross Unrealized Gains 66.2 204.1 68.8
Gross Unrealized Losses (1,327.3) (1,157.9) (1,209.6)
Net Holding Period Gains (Losses) 0.0 0.0 0.0
Total available-for-sale securities $ 38,562.7 $ 36,869.4 $ 27,350.1
% of Total Fair Value 55.80% 55.90% 48.30%
Total fixed maturities | State and local government obligations      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 2,200.7 $ 2,338.4 $ 2,222.4
Gross Unrealized Gains 1.5 2.8 0.9
Gross Unrealized Losses (142.4) (138.4) (161.7)
Net Holding Period Gains (Losses) 0.0 0.0 0.0
Total available-for-sale securities $ 2,059.8 $ 2,202.8 $ 2,061.6
% of Total Fair Value 3.00% 3.30% 3.60%
Total fixed maturities | Foreign government obligations      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 16.9 $ 17.3 $ 16.9
Gross Unrealized Gains 0.0 0.0 0.0
Gross Unrealized Losses (1.0) (1.0) (1.1)
Net Holding Period Gains (Losses) 0.0 0.0 0.0
Total available-for-sale securities $ 15.9 $ 16.3 $ 15.8
% of Total Fair Value 0.10% 0.10% 0.10%
Total fixed maturities | Corporate debt securities      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 12,821.9 $ 11,446.0 $ 11,195.8
Gross Unrealized Gains 45.9 87.2 45.6
Gross Unrealized Losses (328.1) (332.3) (525.4)
Net Holding Period Gains (Losses) (18.4) (17.2) (34.7)
Total available-for-sale securities $ 12,521.3 $ 11,183.7 $ 10,681.3
% of Total Fair Value 18.10% 16.90% 18.80%
Total fixed maturities | Residential mortgage-backed securities      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 390.1 $ 426.9 $ 655.0
Gross Unrealized Gains 0.2 0.2 0.2
Gross Unrealized Losses (9.2) (10.0) (16.3)
Net Holding Period Gains (Losses) 2.0 0.1 (8.9)
Total available-for-sale securities $ 383.1 $ 417.2 $ 630.0
% of Total Fair Value 0.60% 0.60% 1.10%
Total fixed maturities | Commercial mortgage-backed securities      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 4,368.6 $ 4,535.2 $ 5,252.6
Gross Unrealized Gains 2.5 2.2 1.6
Gross Unrealized Losses (519.3) (597.7) (751.2)
Net Holding Period Gains (Losses) 0.0 0.0 0.0
Total available-for-sale securities $ 3,851.8 $ 3,939.7 $ 4,503.0
% of Total Fair Value 5.60% 6.00% 7.90%
Total fixed maturities | Other asset-backed securities      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 6,146.1 $ 5,667.2 $ 5,087.8
Gross Unrealized Gains 9.2 15.7 1.8
Gross Unrealized Losses (93.9) (107.1) (222.5)
Net Holding Period Gains (Losses) (0.2) (0.4) (1.3)
Total available-for-sale securities $ 6,061.2 $ 5,575.4 $ 4,865.8
% of Total Fair Value 8.80% 8.40% 8.60%
Total fixed maturities | Redeemable preferred stocks      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 181.2 $ 187.7 $ 202.5
Gross Unrealized Gains 0.0 0.0 0.0
Gross Unrealized Losses (2.0) (2.4) (5.2)
Net Holding Period Gains (Losses) (5.3) (11.6) (15.7)
Total available-for-sale securities $ 173.9 $ 173.7 $ 181.6
% of Total Fair Value 0.20% 0.30% 0.30%
Short-term investments      
Debt Securities, Available-for-Sale, at Fair Value      
Cost $ 1,326.7 $ 1,789.9 $ 2,524.1
Gross Unrealized Gains 0.0 0.0 0.0
Gross Unrealized Losses 0.0 0.0 0.0
Net Holding Period Gains (Losses) 0.0 0.0 0.0
Total available-for-sale securities $ 1,326.7 $ 1,789.9 $ 2,524.1
% of Total Fair Value 1.90% 2.70% 4.50%
v3.24.1.u1
Investments - Hybrid Securities (Detail) - USD ($)
$ in Millions
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2023
Hybrid Instruments [Line Items]      
Hybrid securities $ 957.6 $ 1,010.3 $ 1,197.3
Corporate debt securities      
Hybrid Instruments [Line Items]      
Hybrid securities 507.1 531.3 548.6
Residential mortgage-backed securities      
Hybrid Instruments [Line Items]      
Hybrid securities 300.0 323.9 482.1
Other asset-backed securities      
Hybrid Instruments [Line Items]      
Hybrid securities 9.5 13.9 33.8
Redeemable preferred stocks      
Hybrid Instruments [Line Items]      
Hybrid securities $ 141.0 $ 141.2 $ 132.8
v3.24.1.u1
Investments - Composition of Fixed Maturities by Maturity (Detail) - Total fixed maturities
$ in Millions
Mar. 31, 2024
USD ($)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract]  
Less than one year $ 7,227.5
One to five years 45,277.4
Five to ten years 13,394.2
Ten years or greater 50.2
Cost 65,949.3
Fair Value  
Less than one year 7,084.8
One to five years 43,850.9
Five to ten years 12,645.2
Ten years or greater 48.8
Fair Value $ 63,629.7
v3.24.1.u1
Investments - Gross Unrealized losses by Major Security (Detail)
$ in Millions
Mar. 31, 2024
USD ($)
security
Dec. 31, 2023
USD ($)
security
Mar. 31, 2023
USD ($)
security
Number of Securities      
Total | security 1,245 1,223 1,416
Less than 12 Months | security 248 126 291
12 Months or Greater | security 997 1,097 1,125
Fair Value      
Total $ 50,113.1 $ 44,062.1 $ 38,603.0
Less than 12 Months 25,748.9 13,347.6 9,487.3
12 Months or Greater 24,364.2 30,714.5 29,115.7
Unrealized Losses      
Total (2,423.2) (2,346.8) (2,893.0)
Less than 12 Months (321.6) (119.3) (219.9)
12 Months or Greater $ (2,101.6) $ (2,227.5) $ (2,673.1)
U.S. government obligations      
Number of Securities      
Total | security 139 147 148
Less than 12 Months | security 37 25 40
12 Months or Greater | security 102 122 108
Fair Value      
Total $ 32,968.1 $ 28,225.0 $ 19,446.8
Less than 12 Months 21,634.6 11,890.0 5,938.5
12 Months or Greater 11,333.5 16,335.0 13,508.3
Unrealized Losses      
Total (1,327.3) (1,157.9) (1,209.6)
Less than 12 Months (295.1) (100.0) (127.5)
12 Months or Greater $ (1,032.2) $ (1,057.9) $ (1,082.1)
State and local government obligations      
Number of Securities      
Total | security 330 324 343
Less than 12 Months | security 41 31 72
12 Months or Greater | security 289 293 271
Fair Value      
Total $ 1,922.7 $ 1,846.2 $ 1,943.6
Less than 12 Months 250.7 169.9 350.7
12 Months or Greater 1,672.0 1,676.3 1,592.9
Unrealized Losses      
Total (142.4) (138.4) (161.7)
Less than 12 Months (1.8) (0.9) (7.4)
12 Months or Greater $ (140.6) $ (137.5) $ (154.3)
Foreign government obligations      
Number of Securities      
Total | security 1 1 1
Less than 12 Months | security 0 0 0
12 Months or Greater | security 1 1 1
Fair Value      
Total $ 15.9 $ 16.3 $ 15.8
Less than 12 Months 0.0 0.0 0.0
12 Months or Greater 15.9 16.3 15.8
Unrealized Losses      
Total (1.0) (1.0) (1.1)
Less than 12 Months 0.0 0.0 0.0
12 Months or Greater $ (1.0) $ (1.0) $ (1.1)
Corporate debt securities      
Number of Securities      
Total | security 363 313 390
Less than 12 Months | security 106 26 93
12 Months or Greater | security 257 287 297
Fair Value      
Total $ 8,094.3 $ 6,642.4 $ 8,129.9
Less than 12 Months 2,369.6 617.2 2,239.3
12 Months or Greater 5,724.7 6,025.2 5,890.6
Unrealized Losses      
Total (328.1) (332.3) (525.4)
Less than 12 Months (20.6) (14.7) (75.5)
12 Months or Greater $ (307.5) $ (317.6) $ (449.9)
Residential mortgage-backed securities      
Number of Securities      
Total | security 35 39 43
Less than 12 Months | security 1 2 13
12 Months or Greater | security 34 37 30
Fair Value      
Total $ 78.0 $ 88.4 $ 141.7
Less than 12 Months 0.0 0.4 10.0
12 Months or Greater 78.0 88.0 131.7
Unrealized Losses      
Total (9.2) (10.0) (16.3)
Less than 12 Months 0.0 0.0 (0.4)
12 Months or Greater $ (9.2) $ (10.0) $ (15.9)
Commercial mortgage-backed securities      
Number of Securities      
Total | security 181 189 220
Less than 12 Months | security 4 1 11
12 Months or Greater | security 177 188 209
Fair Value      
Total $ 3,741.7 $ 3,912.2 $ 4,484.5
Less than 12 Months 190.5 30.7 53.4
12 Months or Greater 3,551.2 3,881.5 4,431.1
Unrealized Losses      
Total (519.3) (597.7) (751.2)
Less than 12 Months (1.8) (2.5) (1.5)
12 Months or Greater $ (517.5) $ (595.2) $ (749.7)
Other asset-backed securities      
Number of Securities      
Total | security 193 207 267
Less than 12 Months | security 59 41 61
12 Months or Greater | security 134 166 206
Fair Value      
Total $ 3,259.5 $ 3,299.1 $ 4,391.9
Less than 12 Months 1,303.5 639.4 884.8
12 Months or Greater 1,956.0 2,659.7 3,507.1
Unrealized Losses      
Total (93.9) (107.1) (222.5)
Less than 12 Months (2.3) (1.2) (6.2)
12 Months or Greater $ (91.6) $ (105.9) $ (216.3)
Redeemable preferred stocks      
Number of Securities      
Total | security 3 3 4
Less than 12 Months | security 0 0 1
12 Months or Greater | security 3 3 3
Fair Value      
Total $ 32.9 $ 32.5 $ 48.8
Less than 12 Months 0.0 0.0 10.6
12 Months or Greater 32.9 32.5 38.2
Unrealized Losses      
Total (2.0) (2.4) (5.2)
Less than 12 Months 0.0 0.0 (1.4)
12 Months or Greater $ (2.0) $ (2.4) $ (3.8)
v3.24.1.u1
Investments - Components of Net Realized Gains (Losses) (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Gain (Loss) on Securities [Line Items]    
Gross realized gains on available-for-sale securities $ 3.2 $ 3.9
Gross realized gains on equity securities 11.2 132.1
Subtotal gross realized gains on security sales 14.4 136.0
Gross realized loss on available-for-sale securities (154.9) (66.7)
Gross realized loss on equity securities (6.0) (112.8)
Subtotal gross realized losses on security sales (160.9) (179.5)
Net realized gains (losses) on available-for-sale securities sales (151.7) (62.8)
Net realized gains (losses) on equity securities sales 5.2 19.3
Subtotal net realized gains (losses) on security sales (146.5) (43.5)
Gain 0.0 13.2
Impairment 0.0 (2.3)
Subtotal net realized gains (losses) on other assets 0.0 10.9
Hybrid securities 7.2 13.9
Equity securities 294.9 90.5
Subtotal net holding period gains (losses) 302.1 104.4
Total net realized gains (losses) on securities 155.6 71.8
U.S. government obligations    
Gain (Loss) on Securities [Line Items]    
Gross realized gains on available-for-sale securities 0.0 3.8
Gross realized loss on available-for-sale securities (135.3) (11.5)
Net realized gains (losses) on available-for-sale securities sales (135.3) (7.7)
State and local government obligations    
Gain (Loss) on Securities [Line Items]    
Gross realized gains on available-for-sale securities 0.3 0.0
Gross realized loss on available-for-sale securities (0.1) 0.0
Net realized gains (losses) on available-for-sale securities sales 0.2 0.0
Corporate debt securities    
Gain (Loss) on Securities [Line Items]    
Gross realized gains on available-for-sale securities 2.9 0.1
Gross realized loss on available-for-sale securities (14.8) (20.4)
Net realized gains (losses) on available-for-sale securities sales (11.9) (20.3)
Commercial mortgage-backed securities    
Gain (Loss) on Securities [Line Items]    
Gross realized loss on available-for-sale securities (4.3) (34.5)
Net realized gains (losses) on available-for-sale securities sales (4.3) (34.5)
Other asset-backed securities    
Gain (Loss) on Securities [Line Items]    
Gross realized loss on available-for-sale securities (0.1) (0.2)
Net realized gains (losses) on available-for-sale securities sales (0.1) (0.2)
Redeemable preferred stocks    
Gain (Loss) on Securities [Line Items]    
Gross realized loss on available-for-sale securities (0.3) 0.0
Net realized gains (losses) on available-for-sale securities sales (0.3) 0.0
Short-term investments    
Gain (Loss) on Securities [Line Items]    
Gross realized loss on available-for-sale securities 0.0 (0.1)
Net realized gains (losses) on available-for-sale securities sales 0.0 (0.1)
Nonredeemable preferred stocks    
Gain (Loss) on Securities [Line Items]    
Gross realized gains on equity securities 0.0 0.1
Gross realized loss on equity securities (5.9) (101.0)
Net realized gains (losses) on equity securities sales (5.9) (100.9)
Common equities    
Gain (Loss) on Securities [Line Items]    
Gross realized gains on equity securities 11.2 132.0
Gross realized loss on equity securities (0.1) (11.8)
Net realized gains (losses) on equity securities sales $ 11.1 $ 120.2
v3.24.1.u1
Investments - Components of Equity Realized Gains (Losses) (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]    
Total net gains (losses) recognized during the period on equity securities $ 300.1 $ 109.8
Less: Net gains (losses) recognized on equity securities sold during the period 5.2 19.3
Net holding period gains (losses) recognized during the period on equity securities held at period end $ 294.9 $ 90.5
v3.24.1.u1
Investments - Components of Net Investment Income (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Net Investment Income [Line Items]    
Gross investment income $ 617.6 $ 419.6
Investment expenses (5.7) (5.5)
Net Investment Income 611.9 414.1
Available-for-sale Securities    
Net Investment Income [Line Items]    
Gross investment income 592.7 392.8
Total equity securities    
Net Investment Income [Line Items]    
Gross investment income 24.9 26.8
Total equity securities | Nonredeemable preferred stocks    
Net Investment Income [Line Items]    
Gross investment income 11.0 15.1
Total equity securities | Common equities    
Net Investment Income [Line Items]    
Gross investment income 13.9 11.7
Total fixed maturities    
Net Investment Income [Line Items]    
Gross investment income 573.8 368.1
Total fixed maturities | U.S. government obligations    
Net Investment Income [Line Items]    
Gross investment income 306.9 163.2
Total fixed maturities | State and local government obligations    
Net Investment Income [Line Items]    
Gross investment income 12.4 10.6
Total fixed maturities | Foreign government obligations    
Net Investment Income [Line Items]    
Gross investment income 0.1 0.1
Total fixed maturities | Corporate debt securities    
Net Investment Income [Line Items]    
Gross investment income 121.5 83.6
Total fixed maturities | Residential mortgage-backed securities    
Net Investment Income [Line Items]    
Gross investment income 5.4 9.2
Total fixed maturities | Commercial mortgage-backed securities    
Net Investment Income [Line Items]    
Gross investment income 46.4 50.0
Total fixed maturities | Other asset-backed securities    
Net Investment Income [Line Items]    
Gross investment income 78.2 48.5
Total fixed maturities | Redeemable preferred stocks    
Net Investment Income [Line Items]    
Gross investment income 2.9 2.9
Short-term investments    
Net Investment Income [Line Items]    
Gross investment income $ 18.9 $ 24.7
v3.24.1.u1
Investments - Additional Information (Detail)
3 Months Ended 12 Months Ended
Mar. 31, 2024
USD ($)
security
Mar. 31, 2023
USD ($)
Dec. 31, 2023
USD ($)
Investments, Debt and Equity Securities [Abstract]      
Principal amount of bonds and certificates of deposit $ 672,400,000    
Securities exceeding 10% of Shareholders' Equity 0 $ 0 $ 0
Non-income producing securities $ 0    
Debt securities, available-for-sale, unrealized loss position, number of positions downgraded | security 7    
Debt securities, available-for-sale, unrealized loss position, fair value, downgraded in period $ 58,200,000    
Debt securities, available-for-sale, unrealized loss position, accumulated loss, downgraded in period 8,200,000    
Debt securities, available-for-sale, allowance for credit loss, not previously recorded 0 0  
Debt securities, available-for-sale, allowance for credit loss 0 0 0
Debt securities, available-for-sale, allowance for credit loss, write-off $ 0 $ 0 $ 0
Recovery of impairment, other assets, number of positions | security 3    
Percent change in investment income 47.00%    
Percent change in book yield 23.00%    
v3.24.1.u1
Fair Value - Composition of Investment Portfolio by Major Security Type (Detail) - USD ($)
$ in Millions
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities $ 64,956.4 $ 62,168.1 $ 52,813.3
Equity securities 4,081.6 3,830.5 3,873.1
Investments, fair value 69,038.0 65,998.6 56,686.4
Fair value 6,297.8 6,431.3 5,881.0
Nonredeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 886.7 902.1 1,078.8
Nonredeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 834.5 851.9 991.9
Nonredeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 37.4 35.4 70.5
Nonredeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 14.8 14.8 16.4
Common equities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 3,194.9 2,928.4 2,794.3
Common equities | Common Stocks, excluding Other Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 3,170.6 2,907.8 2,774.0
Common equities | Other risk investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 24.3 20.6 20.3
Total fixed maturities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 63,629.7 60,378.2 50,289.2
Total fixed maturities | U.S. government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 38,562.7 36,869.4 27,350.1
Total fixed maturities | State and local government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 2,059.8 2,202.8 2,061.6
Total fixed maturities | Foreign government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 15.9 16.3 15.8
Total fixed maturities | Corporate debt securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 12,521.3 11,183.7 10,681.3
Total fixed maturities | Residential mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 383.1 417.2 630.0
Total fixed maturities | Commercial mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 3,851.8 3,939.7 4,503.0
Total fixed maturities | Other asset-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 6,061.2 5,575.4 4,865.8
Total fixed maturities | Debt Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 53,159.7 50,272.2 40,108.8
Total fixed maturities | Debt Securities | U.S. government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 38,562.7 36,869.4 27,350.1
Total fixed maturities | Debt Securities | State and local government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 2,059.8 2,202.8 2,061.6
Total fixed maturities | Debt Securities | Foreign government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 15.9 16.3 15.8
Total fixed maturities | Debt Securities | Corporate debt securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 12,521.3 11,183.7 10,681.3
Total fixed maturities | Asset-backed Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 10,296.1 9,932.3 9,998.8
Total fixed maturities | Asset-backed Securities | Residential mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 383.1 417.2 630.0
Total fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 3,851.8 3,939.7 4,503.0
Total fixed maturities | Asset-backed Securities | Other asset-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 6,061.2 5,575.4 4,865.8
Total fixed maturities | Redeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 173.9 173.7 181.6
Total fixed maturities | Redeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 23.2 23.1 40.0
Total fixed maturities | Redeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 9.6 9.4 8.8
Total fixed maturities | Redeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 141.1 141.2 132.8
Short-term investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 1,326.7 1,789.9 2,524.1
Fair Value, Inputs, Level 1      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 39,889.4 38,626.4 29,883.8
Equity securities 3,148.1 2,885.3 2,795.7
Investments, fair value 43,037.5 41,511.7 32,679.5
Fair value 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Nonredeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 40.0
Fair Value, Inputs, Level 1 | Nonredeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 40.0
Fair Value, Inputs, Level 1 | Nonredeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Nonredeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Common equities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 3,148.1 2,885.3 2,755.7
Fair Value, Inputs, Level 1 | Common equities | Common Stocks, excluding Other Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 3,148.1 2,885.3 2,755.7
Fair Value, Inputs, Level 1 | Common equities | Other risk investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 38,562.7 36,869.4 27,359.7
Fair Value, Inputs, Level 1 | Total fixed maturities | Debt Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 38,562.7 36,869.4 27,350.1
Fair Value, Inputs, Level 1 | Total fixed maturities | Debt Securities | U.S. government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 38,562.7 36,869.4 27,350.1
Fair Value, Inputs, Level 1 | Total fixed maturities | Debt Securities | State and local government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities | Debt Securities | Foreign government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities | Debt Securities | Corporate debt securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities | Asset-backed Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities | Asset-backed Securities | Residential mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities | Asset-backed Securities | Other asset-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities | Redeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 9.6
Fair Value, Inputs, Level 1 | Total fixed maturities | Redeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities | Redeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 1 | Total fixed maturities | Redeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 9.6
Fair Value, Inputs, Level 1 | Short-term investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 1,326.7 1,757.0 2,524.1
Fair Value, Inputs, Level 2      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 25,064.0 23,538.7 22,929.5
Equity securities 822.7 838.1 955.0
Investments, fair value 25,886.7 24,376.8 23,884.5
Fair value 6,297.8 6,431.3 5,881.0
Fair Value, Inputs, Level 2 | Nonredeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 822.7 838.1 955.0
Fair Value, Inputs, Level 2 | Nonredeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 785.3 802.7 884.5
Fair Value, Inputs, Level 2 | Nonredeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 37.4 35.4 70.5
Fair Value, Inputs, Level 2 | Nonredeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 0.0
Fair Value, Inputs, Level 2 | Common equities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 0.0
Fair Value, Inputs, Level 2 | Common equities | Common Stocks, excluding Other Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 0.0
Fair Value, Inputs, Level 2 | Common equities | Other risk investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 0.0
Fair Value, Inputs, Level 2 | Total fixed maturities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 25,064.0 23,505.8 22,929.5
Fair Value, Inputs, Level 2 | Total fixed maturities | Debt Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 14,594.0 13,399.8 12,758.7
Fair Value, Inputs, Level 2 | Total fixed maturities | Debt Securities | U.S. government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 2 | Total fixed maturities | Debt Securities | State and local government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 2,059.8 2,202.8 2,061.6
Fair Value, Inputs, Level 2 | Total fixed maturities | Debt Securities | Foreign government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 15.9 16.3 15.8
Fair Value, Inputs, Level 2 | Total fixed maturities | Debt Securities | Corporate debt securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 12,518.3 11,180.7 10,681.3
Fair Value, Inputs, Level 2 | Total fixed maturities | Asset-backed Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 10,296.1 9,932.3 9,998.8
Fair Value, Inputs, Level 2 | Total fixed maturities | Asset-backed Securities | Residential mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 383.1 417.2 630.0
Fair Value, Inputs, Level 2 | Total fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 3,851.8 3,939.7 4,503.0
Fair Value, Inputs, Level 2 | Total fixed maturities | Asset-backed Securities | Other asset-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 6,061.2 5,575.4 4,865.8
Fair Value, Inputs, Level 2 | Total fixed maturities | Redeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 173.9 173.7 172.0
Fair Value, Inputs, Level 2 | Total fixed maturities | Redeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 23.2 23.1 40.0
Fair Value, Inputs, Level 2 | Total fixed maturities | Redeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 9.6 9.4 8.8
Fair Value, Inputs, Level 2 | Total fixed maturities | Redeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 141.1 141.2 123.2
Fair Value, Inputs, Level 2 | Short-term investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 32.9 0.0
Fair Value, Inputs, Level 3      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 3.0 3.0 0.0
Equity securities 110.8 107.1 122.4
Investments, fair value 113.8 110.1 122.4
Fair value 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Nonredeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 64.0 64.0 83.8
Fair Value, Inputs, Level 3 | Nonredeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 49.2 49.2 67.4
Fair Value, Inputs, Level 3 | Nonredeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Nonredeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 14.8 14.8 16.4
Fair Value, Inputs, Level 3 | Common equities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 46.8 43.1 38.6
Fair Value, Inputs, Level 3 | Common equities | Common Stocks, excluding Other Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 22.5 22.5 18.3
Fair Value, Inputs, Level 3 | Common equities | Other risk investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 24.3 20.6 20.3
Fair Value, Inputs, Level 3 | Total fixed maturities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 3.0 3.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Debt Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 3.0 3.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Debt Securities | U.S. government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Debt Securities | State and local government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Debt Securities | Foreign government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Debt Securities | Corporate debt securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 3.0 3.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Asset-backed Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Asset-backed Securities | Residential mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Asset-backed Securities | Other asset-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Redeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Redeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Redeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Total fixed maturities | Redeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Fair Value, Inputs, Level 3 | Short-term investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 0.0 0.0 0.0
Carrying (Reported) Amount, Fair Value Disclosure      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 67,276.0 64,231.8 55,648.0
Equity securities 1,639.3 1,683.1 1,938.2
Investments, fair value 68,915.3 65,914.9 57,586.2
Long-term debt 6,889.7 6,888.6 6,389.3
Carrying (Reported) Amount, Fair Value Disclosure | Nonredeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 931.1 977.1 1,197.7
Carrying (Reported) Amount, Fair Value Disclosure | Nonredeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 876.1 922.1 1,102.7
Carrying (Reported) Amount, Fair Value Disclosure | Nonredeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 40.0 40.0 80.0
Carrying (Reported) Amount, Fair Value Disclosure | Nonredeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 15.0 15.0 15.0
Carrying (Reported) Amount, Fair Value Disclosure | Common equities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 708.2 706.0 740.5
Carrying (Reported) Amount, Fair Value Disclosure | Common equities | Common Stocks, excluding Other Risk      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 683.9 685.4 720.2
Carrying (Reported) Amount, Fair Value Disclosure | Common equities | Other risk investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity securities 24.3 20.6 20.3
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 65,949.3 62,441.9 53,123.9
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Debt Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 54,863.3 51,624.9 41,926.0
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Debt Securities | U.S. government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 39,823.8 37,823.2 28,490.9
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Debt Securities | State and local government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 2,200.7 2,338.4 2,222.4
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Debt Securities | Foreign government obligations      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 16.9 17.3 16.9
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Debt Securities | Corporate debt securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 12,821.9 11,446.0 11,195.8
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Asset-backed Securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 10,904.8 10,629.3 10,995.4
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Asset-backed Securities | Residential mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 390.1 426.9 655.0
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Asset-backed Securities | Commercial mortgage-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 4,368.6 4,535.2 5,252.6
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Asset-backed Securities | Other asset-backed securities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 6,146.1 5,667.2 5,087.8
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Redeemable preferred stocks      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 181.2 187.7 202.5
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Redeemable preferred stocks | Financials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 24.5 24.5 43.5
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Redeemable preferred stocks | Utilities      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 10.4 10.4 10.5
Carrying (Reported) Amount, Fair Value Disclosure | Total fixed maturities | Redeemable preferred stocks | Industrials      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities 146.3 152.8 148.5
Carrying (Reported) Amount, Fair Value Disclosure | Short-term investments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total available-for-sale securities $ 1,326.7 $ 1,789.9 $ 2,524.1
v3.24.1.u1
Fair Value - Summary of Changes in Fair Value Associated with Level 3 Assets (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance $ 110.1 $ 121.9
Calls/ Maturities/ Paydowns 3.7 0.5
Purchases 0.0 0.0
Sales 0.0 0.0
Net Realized (Gain)/Loss on Sales 0.0 0.0
Change in Valuation 0.0 0.0
Net Transfers In (Out)  0.0 0.0
Fair value, ending balance 113.8 122.4
Corporate debt securities    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance 3.0  
Calls/ Maturities/ Paydowns 0.0  
Purchases 0.0  
Sales 0.0  
Net Realized (Gain)/Loss on Sales 0.0  
Change in Valuation 0.0  
Net Transfers In (Out)  0.0  
Fair value, ending balance 3.0  
Nonredeemable preferred stocks | Financials    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance 49.2 67.4
Calls/ Maturities/ Paydowns 0.0 0.0
Purchases 0.0 0.0
Sales 0.0 0.0
Net Realized (Gain)/Loss on Sales 0.0 0.0
Change in Valuation 0.0 0.0
Net Transfers In (Out)  0.0 0.0
Fair value, ending balance 49.2 67.4
Nonredeemable preferred stocks | Industrials    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance 14.8 16.4
Calls/ Maturities/ Paydowns 0.0 0.0
Purchases 0.0 0.0
Sales 0.0 0.0
Net Realized (Gain)/Loss on Sales 0.0 0.0
Change in Valuation 0.0 0.0
Net Transfers In (Out)  0.0 0.0
Fair value, ending balance 14.8 16.4
Common equities | Common Stocks, excluding Other Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance 22.5 18.3
Calls/ Maturities/ Paydowns 0.0 0.0
Purchases 0.0 0.0
Sales 0.0 0.0
Net Realized (Gain)/Loss on Sales 0.0 0.0
Change in Valuation 0.0 0.0
Net Transfers In (Out)  0.0 0.0
Fair value, ending balance 22.5 18.3
Common equities | Other risk investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Fair value, beginning balance 20.6 19.8
Calls/ Maturities/ Paydowns 3.7 0.5
Purchases 0.0 0.0
Sales 0.0 0.0
Net Realized (Gain)/Loss on Sales 0.0 0.0
Change in Valuation 0.0 0.0
Net Transfers In (Out)  0.0 0.0
Fair value, ending balance $ 24.3 $ 20.3
v3.24.1.u1
Fair Value - Summary of Quantitative Information about Level 3 Fair Value Measurements (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Dec. 31, 2023
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Investments, fair value $ 69,038.0 $ 56,686.4 $ 65,998.6
Fair Value, Inputs, Level 3      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Investments, fair value 113.8 122.4 110.1
Fair Value, Inputs, Level 3 | Total Quantitative Level Three Securities      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Investments, fair value 89.5 102.1 89.5
Fair Value, Inputs, Level 3 | Third Party Pricing Exemption Securities      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Investments, fair value 24.3 20.3 20.6
Fair Value, Inputs, Level 3 | Corporate debt securities | Total Quantitative Level Three Securities      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Investments, fair value $ 3.0   $ 3.0
Fair value inputs, market cap price change percentage, range, minimum (2.30%)   0.30%
Fair value inputs, market cap price change percentage, range, maximum 1.20%   7.70%
Fair value inputs, market cap price change percentage, weighted average (0.10%)   2.60%
Fair Value, Inputs, Level 3 | Nonredeemable preferred stocks | Total Quantitative Level Three Securities      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Investments, fair value $ 64.0 $ 83.8 $ 64.0
Fair value inputs, market cap price change percentage, range, minimum 3.40% 2.70% 17.20%
Fair value inputs, market cap price change percentage, range, maximum 28.40% 23.30% 39.70%
Fair value inputs, market cap price change percentage, weighted average 22.60% 9.20% 21.70%
Fair Value, Inputs, Level 3 | Common equities | Total Quantitative Level Three Securities      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Investments, fair value $ 22.5 $ 18.3 $ 22.5
Fair value inputs, market cap price change percentage, range, minimum (37.90%) (51.30%) (45.80%)
Fair value inputs, market cap price change percentage, range, maximum 39.60% 48.30% 95.60%
Fair value inputs, market cap price change percentage, weighted average 3.40% 15.60% 39.70%
v3.24.1.u1
Fair Value - Additional Information (Detail) - USD ($)
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2023
Fair Value, Inputs, Level 1      
Fair Value Measurements [Line Items]      
Vendor quoted prices, percent of FV hierarchy level 92.00% 93.00% 91.00%
Fair Value, Inputs, Level 2      
Fair Value Measurements [Line Items]      
Vendor quoted prices, percent of FV hierarchy level 100.00% 100.00% 98.00%
Dealer quoted prices, percent of FV hierarchy level     2.00%
Fair Value, Inputs, Level 3 | Total fixed maturities      
Fair Value Measurements [Line Items]      
Number of securities 1 1 0
v3.24.1.u1
Debt - Summary of Debt (Detail) - USD ($)
Mar. 31, 2024
Dec. 31, 2023
May 31, 2023
Mar. 31, 2023
Mar. 31, 2022
Mar. 31, 2020
Oct. 31, 2018
Mar. 31, 2018
Apr. 30, 2017
Aug. 31, 2016
Jan. 31, 2015
Apr. 30, 2014
Nov. 30, 2002
Mar. 31, 1999
Debt Instrument [Line Items]                            
Debt [1] $ 6,889,700,000 $ 6,888,600,000   $ 6,389,300,000                    
Fair value 6,297,800,000 6,431,300,000   5,881,000,000                    
2.45% Senior Notes due 2027 (issued: $500.0, August 2016)                            
Debt Instrument [Line Items]                            
Long-term debt 498,700,000 498,600,000   498,300,000                    
Fair value 468,600,000 468,900,000   464,200,000                    
Debt, stated interest rate                   2.45%        
Debt, face amount                   $ 500,000,000.0        
2.50% Senior Notes due 2027 (issued: $500.0, March 2022)                            
Debt Instrument [Line Items]                            
Long-term debt 498,200,000 498,100,000   497,700,000                    
Fair value 468,500,000 469,100,000   463,800,000                    
Debt, stated interest rate         2.50%                  
Debt, face amount         $ 500,000,000.0                  
6 5/8% Senior Notes due 2029 (issued: $300.0, March 1999)                            
Debt Instrument [Line Items]                            
Long-term debt 297,900,000 297,800,000   297,600,000                    
Fair value 323,500,000 328,700,000   329,600,000                    
Debt, stated interest rate                           6.625%
Debt, face amount                           $ 300,000,000.0
4.00% Senior Notes due 2029 (issued: $550.0, October 2018)                            
Debt Instrument [Line Items]                            
Long-term debt 547,100,000 546,900,000   546,500,000                    
Fair value 532,500,000 542,600,000   538,500,000                    
Debt, stated interest rate             4.00%              
Debt, face amount             $ 550,000,000.0              
3.20% Senior Notes due 2030 (issued: $500.0, March 2020)                            
Debt Instrument [Line Items]                            
Long-term debt 497,400,000 497,300,000   497,000,000.0                    
Fair value 456,100,000 462,200,000   460,000,000.0                    
Debt, stated interest rate           3.20%                
Debt, face amount           $ 500,000,000.0                
3.00% Senior Notes due 2032 (issued: $500.0, March 2022)                            
Debt Instrument [Line Items]                            
Long-term debt 496,400,000 496,300,000   496,000,000.0                    
Fair value 435,700,000 446,000,000.0   446,900,000                    
Debt, stated interest rate         3.00%                  
Debt, face amount         $ 500,000,000.0                  
6.25% Senior Notes due 2032 (issued: $400.0, November 2002)                            
Debt Instrument [Line Items]                            
Long-term debt 396,800,000 396,700,000   396,500,000                    
Fair value 434,200,000 445,600,000   448,100,000                    
Debt, stated interest rate                         6.25%  
Debt, face amount                         $ 400,000,000.0  
4.95% Senior Notes due 2033 (issued: $500.0, May 2023)                            
Debt Instrument [Line Items]                            
Long-term debt 496,500,000 496,400,000   0                    
Fair value 499,200,000 513,000,000.0   0                    
Debt, stated interest rate     4.95%                      
Debt, face amount     $ 500,000,000.0                      
4.35% Senior Notes due 2044 (issued: $350.0, April 2014)                            
Debt Instrument [Line Items]                            
Long-term debt 347,000,000.0 347,000,000.0   346,900,000                    
Fair value 312,800,000 314,200,000   312,300,000                    
Debt, stated interest rate                       4.35%    
Debt, face amount                       $ 350,000,000.0    
3.70% Senior Notes due 2045 (issued: $400.0, January 2015)                            
Debt Instrument [Line Items]                            
Long-term debt 395,900,000 395,900,000   395,800,000                    
Fair value 327,900,000 325,100,000   324,000,000.0                    
Debt, stated interest rate                     3.70%      
Debt, face amount                     $ 400,000,000.0      
4.125% Senior Notes due 2047 (issued: $850.0, April 2017)                            
Debt Instrument [Line Items]                            
Long-term debt 842,300,000 842,300,000   842,100,000                    
Fair value 719,200,000 756,200,000   743,800,000                    
Debt, stated interest rate                 4.125%          
Debt, face amount                 $ 850,000,000.0          
4.20% Senior Notes due 2048 (issued: $600.0, March 2018)                            
Debt Instrument [Line Items]                            
Long-term debt 590,700,000 590,600,000   590,400,000                    
Fair value 519,800,000 534,100,000   530,000,000.0                    
Debt, stated interest rate               4.20%            
Debt, face amount               $ 600,000,000.0            
3.95% Senior Notes due 2050 (issued: $500.0, March 2020)                            
Debt Instrument [Line Items]                            
Long-term debt 491,200,000 491,100,000   491,000,000.0                    
Fair value 409,800,000 422,300,000   420,300,000                    
Debt, stated interest rate           3.95%                
Debt, face amount           $ 500,000,000.0                
3.70% Senior Notes due 2052 (issued: $500.0, March 2022)                            
Debt Instrument [Line Items]                            
Long-term debt 493,600,000 493,600,000   493,500,000                    
Fair value $ 390,000,000.0 $ 403,300,000   $ 399,500,000                    
Debt, stated interest rate         3.70%                  
Debt, face amount         $ 500,000,000.0                  
[1] Consists of long-term debt. See Note 4 – Debt for further discussion.
v3.24.1.u1
Debt - Additional Information (Detail) - USD ($)
3 Months Ended 12 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Dec. 31, 2023
Debt Instrument [Line Items]      
Long-term debt, current maturities $ 0 $ 0 $ 0
Discretionary Line of Credit      
Debt Instrument [Line Items]      
Maximum borrowing capacity 300,000,000    
Borrowings outstanding $ 0 $ 0 $ 0
v3.24.1.u1
Income Taxes - Additional Information (Details) - USD ($)
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Dec. 31, 2023
Income Tax Disclosure [Abstract]      
Provision for income taxes 20.70% 19.20%  
Valuation allowance $ 0 $ 0 $ 0
Gross deferred tax asset related to unrealized losses on fixed-maturity securities 482,500,000 582,600,000 427,300,000
Accrued income taxes $ 961,800,000 $ 203,300,000 $ 311,800,000
v3.24.1.u1
Loss and Loss Adjustment Expense Reserves Activity in Loss and Loss Adjustment Expense Reserves (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Dec. 31, 2023
Dec. 31, 2022
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]        
Balance at January 1 $ 34,389.2 $ 30,359.3    
Less reinsurance recoverables on unpaid losses 4,651.9 5,301.1 $ 4,789.0 $ 5,559.2
Net balance at January 1 29,600.2 24,800.1    
Incurred related to:        
Current year 10,983.0 10,002.8    
Prior years (11.4) 621.2    
Total incurred 10,971.6 10,624.0    
Paid related to:        
Current year 4,421.7 3,962.6    
Prior years 5,971.0 5,736.2    
Total paid 10,392.7 9,698.8    
Net balance at March 31 30,179.1 25,725.3    
Plus reinsurance recoverables on unpaid losses 4,651.9 5,301.1    
Balance at March 31 $ 34,831.0 $ 31,026.4    
v3.24.1.u1
Loss and Loss Adjustment Expense Reserves (Details)
$ in Millions
3 Months Ended
Mar. 31, 2024
USD ($)
Mar. 31, 2023
USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]    
Prior years $ (11.4) $ 621.2
Personal Lines | Personal auto business    
Liability for Claims and Claims Adjustment Expense [Line Items]    
Prior years $ (100.0) 428.0
Personal Lines | Personal auto business | Agency    
Liability for Claims and Claims Adjustment Expense [Line Items]    
Percent of prior year claims and claims adjustment expense 0.60  
Commercial Lines    
Liability for Claims and Claims Adjustment Expense [Line Items]    
Prior years $ 70.0 144.0
Property    
Liability for Claims and Claims Adjustment Expense [Line Items]    
Prior years   42.0
Short-Duration Insurance Contract, Accident Year 2023    
Liability for Claims and Claims Adjustment Expense [Line Items]    
Prior years (50.0)  
Short-Duration Insurance Contract, Accident Year 2022    
Liability for Claims and Claims Adjustment Expense [Line Items]    
Prior years $ (15.0) 498.0
Short-Duration Insurance Contract, Accident Year 2021    
Liability for Claims and Claims Adjustment Expense [Line Items]    
Prior years   $ 30.0
v3.24.1.u1
Supplemental Cash Flow Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Dec. 31, 2023
Operating lease liabilities $ 28.0 $ 9.3  
Income taxes 0.0 0.1  
Interest 87.9 87.9  
Operating lease liabilities 21.6 21.5  
Cash and Cash Equivalents      
Open reverse repurchase commitments 107.7 177.5 $ 68.2
Common equities | Quarterly dividend      
Common share dividends $ 58.6 $ 58.5  
v3.24.1.u1
Segment Information - Operating Results (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Segment Reporting Information [Line Items]    
Revenues $ 17,242.5 $ 14,303.2
Pretax Profit (Loss) 2,939.9 554.4
Personal Lines | Agency | Underwriting operations    
Segment Reporting Information [Line Items]    
Revenues 5,857.7 4,860.2
Pretax Profit (Loss) 950.7 162.6
Personal Lines | Direct | Underwriting operations    
Segment Reporting Information [Line Items]    
Revenues 7,020.5 5,717.4
Pretax Profit (Loss) 1,043.6 (22.1)
Operating Segments | Underwriting operations    
Segment Reporting Information [Line Items]    
Revenues 16,148.6 13,533.1
Pretax Profit (Loss) 2,249.9 141.6
Operating Segments | Personal Lines | Underwriting operations    
Segment Reporting Information [Line Items]    
Revenues 12,878.2 10,577.6
Pretax Profit (Loss) $ 1,994.3 $ 140.5
Personal auto insurance percentage of the total personal lines segment net premiums earned 95.00% 94.00%
Operating Segments | Commercial Lines | Underwriting operations    
Segment Reporting Information [Line Items]    
Revenues $ 2,557.4 $ 2,356.1
Pretax Profit (Loss) 209.0 37.2
Operating Segments | Property | Underwriting operations    
Segment Reporting Information [Line Items]    
Revenues 712.8 598.7
Pretax Profit (Loss) 46.9 (32.7)
Operating Segments | Other Indemnity | Underwriting operations    
Segment Reporting Information [Line Items]    
Revenues 0.2 0.7
Pretax Profit (Loss) (0.3) (3.4)
Segment Reconciling Items    
Segment Reporting Information [Line Items]    
Interest expense (69.6) (63.3)
Segment Reconciling Items | Fees and other revenues    
Segment Reporting Information [Line Items]    
Revenues 236.5 206.2
Segment Reconciling Items | Service businesses    
Segment Reporting Information [Line Items]    
Revenues 84.2 72.5
Pretax Profit (Loss) (7.9) (9.8)
Segment Reconciling Items | Investments    
Segment Reporting Information [Line Items]    
Revenues 773.2 491.4
Pretax Profit (Loss) $ 767.5 $ 485.9
v3.24.1.u1
Segment Information - Underwriting Margins and Combined Ratios for our Underwriting Operations (Detail) - Underwriting operations
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Personal Lines | Agency    
Segment Reporting Information [Line Items]    
Under-writing Margin 16.20% 3.30%
Combined Ratio 83.80% 96.70%
Personal Lines | Direct    
Segment Reporting Information [Line Items]    
Under-writing Margin 14.90% (0.40%)
Combined Ratio 85.10% 100.40%
Operating Segments    
Segment Reporting Information [Line Items]    
Under-writing Margin 13.90% 1.00%
Combined Ratio 86.10% 99.00%
Operating Segments | Personal Lines    
Segment Reporting Information [Line Items]    
Under-writing Margin 15.50% 1.30%
Combined Ratio 84.50% 98.70%
Operating Segments | Commercial Lines    
Segment Reporting Information [Line Items]    
Under-writing Margin 8.20% 1.60%
Combined Ratio 91.80% 98.40%
Operating Segments | Property    
Segment Reporting Information [Line Items]    
Under-writing Margin 6.60% (5.50%)
Combined Ratio 93.40% 105.50%
v3.24.1.u1
Dividends (Details) - USD ($)
$ / shares in Units, $ in Millions
1 Months Ended 3 Months Ended
Feb. 28, 2024
Jan. 31, 2024
Apr. 30, 2023
Mar. 31, 2023
Jan. 31, 2023
Mar. 31, 2024
Mar. 31, 2023
Cash dividends declared on common stock (in dollars per share)           $ 0.10 $ 0.10
Dividends paid to common shareholders           $ 497.9 $ 58.5
Dividends paid to preferred shareholders           $ 7.8 13.4
Series B Preferred Stock              
Cash dividends paid on preferred stock (in dollars per share) $ 15.688377     $ 26.875      
Dividends paid to preferred shareholders $ 7.8     $ 13.4      
Preferred stock, liquidation preference per share (USD per share)           $ 1,000  
Aggregate redemption amount           $ 507.8  
Quarterly dividend              
Cash dividends declared on common stock (in dollars per share)           $ 0.10  
Cash dividends paid on common stock (in dollars per share)   $ 0.10 $ 0.10   $ 0.10    
Dividends paid to common shareholders   $ 58.6 $ 58.5   $ 58.5    
Annual variable dividend              
Cash dividends paid on common stock (in dollars per share)   $ 0.75          
Dividends paid to common shareholders   $ 439.3          
Common equities | Quarterly dividend              
Common share dividends       $ 58.5   $ 58.6 $ 58.5
v3.24.1.u1
Other Comprehensive Income (Loss) - Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]    
Pretax total accumulated other comprehensive income (loss), beginning balance $ (2,052.9) $ (3,556.9)
Pretax total accumulated other comprehensive income (loss), Investment securities (413.6) 705.6
Pretax total accumulated other comprehensive income (loss), Foreign currency translation adjustment (0.3)  
Pretax total accumulated other comprehensive income (loss), before reclassifications (413.9) 705.6
Pretax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities (150.5) (57.9)
Pretax total accumulated other comprehensive income (loss), Interest expense (0.1) (0.1)
Total reclassification adjustment for amounts realized in net income, pre tax (150.6) (58.0)
Total other comprehensive income (loss), pre tax (263.3) 763.6
Pretax total accumulated other comprehensive income (loss), ending balance (2,316.2) (2,793.3)
Accumulated Other Comprehensive Income (Loss), Tax [Roll Forward]    
Total tax (provision) benefit, beginning balance 437.2 754.9
Total tax (provision) benefit, Investment securities 86.9 (148.2)
Total tax (provision) benefit, Foreign currency translation adjustment 0.1  
Total tax (provision) benefit, before reclassifications 87.0 (148.2)
Total tax (provision) benefit, Net realized gains (losses) on securities 31.6 12.1
Total tax (provision) benefit, Interest expense 0.0 0.0
Total reclassification adjustment for amounts realized in net income, Total tax (provision) benefit 31.6 12.1
Total other comprehensive income (loss), tax (provision) benefit 55.4 (160.3)
Total tax (provision) benefit, ending balance 492.6 594.6
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]    
After tax total accumulated other comprehensive income (loss), beginning balance (1,615.7) (2,802.0)
After tax total accumulated other comprehensive income (loss), Investment securities (326.7) 557.4
After tax total accumulated other comprehensive income (loss), Foreign currency translation adjustment (0.2) 0.0
After tax total accumulated other comprehensive income (loss), before reclassifications (326.9) 557.4
After tax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities (118.9) (45.8)
After tax total accumulated other comprehensive income (loss), Interest expense (0.1) (0.1)
Total reclassification adjustment for amounts realized in net income, after tax (119.0) (45.9)
Total other comprehensive income (loss), after tax (207.9) 603.3
After tax total accumulated other comprehensive income (loss), ending balance (1,823.6) (2,198.7)
Total net unrealized gains (losses) on securities    
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]    
After tax total accumulated other comprehensive income (loss), beginning balance (1,600.8) (2,786.3)
After tax total accumulated other comprehensive income (loss), Investment securities (326.7) 557.4
After tax total accumulated other comprehensive income (loss), Foreign currency translation adjustment 0.0  
After tax total accumulated other comprehensive income (loss), before reclassifications (326.7) 557.4
After tax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities (118.9) (45.8)
After tax total accumulated other comprehensive income (loss), Interest expense 0.0 0.0
Total reclassification adjustment for amounts realized in net income, after tax (118.9) (45.8)
Total other comprehensive income (loss), after tax (207.8) 603.2
After tax total accumulated other comprehensive income (loss), ending balance (1,808.6) (2,183.1)
Net unrealized losses on forecasted transactions    
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]    
After tax total accumulated other comprehensive income (loss), beginning balance (14.0) (14.5)
After tax total accumulated other comprehensive income (loss), Investment securities 0.0 0.0
After tax total accumulated other comprehensive income (loss), Foreign currency translation adjustment 0.0  
After tax total accumulated other comprehensive income (loss), before reclassifications 0.0 0.0
After tax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities 0.0 0.0
After tax total accumulated other comprehensive income (loss), Interest expense (0.1) (0.1)
Total reclassification adjustment for amounts realized in net income, after tax (0.1) (0.1)
Total other comprehensive income (loss), after tax 0.1 0.1
After tax total accumulated other comprehensive income (loss), ending balance (13.9) (14.4)
Foreign currency translation adjustment    
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]    
After tax total accumulated other comprehensive income (loss), beginning balance (0.9) (1.2)
After tax total accumulated other comprehensive income (loss), Investment securities 0.0 0.0
After tax total accumulated other comprehensive income (loss), Foreign currency translation adjustment (0.2)  
After tax total accumulated other comprehensive income (loss), before reclassifications (0.2) 0.0
After tax total accumulated other comprehensive income (loss), Net realized gains (losses) on securities 0.0 0.0
After tax total accumulated other comprehensive income (loss), Interest expense 0.0 0.0
Total reclassification adjustment for amounts realized in net income, after tax 0.0 0.0
Total other comprehensive income (loss), after tax (0.2) 0.0
After tax total accumulated other comprehensive income (loss), ending balance $ (1.1) $ (1.2)
v3.24.1.u1
Other Comprehensive Income (Loss) - Components of Other Comprehensive Income (Loss) Including Reclassification Adjustments by Income Statement, Additional Information (Detail)
$ in Millions
Mar. 31, 2024
USD ($)
Equity [Abstract]  
Net unrealized losses on forecasted transactions, expected to reclassify into income within the next 12 months $ 0.6
v3.24.1.u1
Litigation - Additional Information (Details)
Mar. 31, 2024
segment
Commitments and Contingencies Disclosure [Abstract]  
Number of states, classes certified 5