ARGO GROUP INTERNATIONAL HOLDINGS, LTD., 10-Q filed on 8/6/2021
Quarterly Report
v3.21.2
Cover - shares
 6 Months Ended
Jun. 30, 2021
Aug. 04, 2021
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2021  
Document Transition Report false  
Entity File Number 1-15259  
Entity Registrant Name ARGO GROUP INTERNATIONAL HOLDINGS, LTD.  
Entity Incorporation, State or Country Code D0  
Entity Tax Identification Number 98-0214719  
Entity Address, Address Line One 90 Pitts Bay Road  
Entity Address, City or Town Pembroke  
Entity Address, Postal Zip Code HM08  
Entity Address, Country BM  
City Area Code 441  
Local Phone Number 296-5858  
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   34,852,439
Entity Central Index Key 0001091748  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2021  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Common Shares    
Document Information [Line Items]    
Title of 12(b) Security Common Stock, par value of $1.00 per share  
Trading Symbol ARGO  
Security Exchange Name NYSE  
Guarantee of Argo Group U.S., Inc. 6.500% Senior Notes due 2042    
Document Information [Line Items]    
Title of 12(b) Security Guarantee of Argo Group U.S., Inc.  6.500% Senior Notes due 2042  
Trading Symbol ARGD  
Security Exchange Name NYSE  
Depositary Shares    
Document Information [Line Items]    
Title of 12(b) Security Depositary Shares, each representing a 1/1000th Interest in a shareof Series A 7.00% Non-Cumulative Preference Shares, par value $1.00 per share  
Trading Symbol ARGOPrA  
Security Exchange Name NYSE  
v3.21.2
Condensed Consolidated Balance Sheets - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Investments:    
Fixed maturities available-for-sale, at fair value (cost: 2021 - $3,981.2, 2020 - $3,981.1; allowance for expected credit losses: 2021 - $6.4, 2020 - $6.6) $ 4,057.7 $ 4,107.1
Equity securities, at fair value (cost: 2021 - $129.5; 2020 - $162.5) 185.7 176.7
Other investments (cost: 2021 - $412.3; 2020 - $429.4) 412.3 429.4
Short-term investments, at fair value (cost: 2021 - $529.2; 2020 - $541.4) 530.2 542.6
Total investments 5,185.9 5,255.8
Cash 190.7 148.8
Accrued investment income 20.8 21.8
Premiums receivable 681.7 679.8
Reinsurance recoverables 2,859.9 3,009.0
Goodwill 147.3 147.3
Intangible assets, net of accumulated amortization 60.5 60.5
Current income taxes receivable, net 0.0 3.0
Deferred tax asset, net 32.3 16.7
Deferred acquisition costs, net 168.2 163.6
Ceded unearned premiums 591.0 575.1
Operating lease right-of-use assets 78.8 82.0
Other assets 348.0 294.7
Assets held for sale 3.2 7.7
Total assets 10,368.3 10,465.8
Liabilities and Shareholders' Equity    
Reserves for losses and loss adjustment expenses 5,238.6 5,406.0
Unearned premiums 1,473.7 1,464.8
Accrued underwriting expenses and other liabilities 207.4 167.6
Ceded reinsurance payable, net 920.2 950.4
Funds held 73.0 64.7
Senior unsecured fixed rate notes 140.2 140.2
Other indebtedness 60.4 60.7
Junior subordinated debentures 258.0 257.8
Current income taxes payable, net 5.3 0.0
Operating lease liabilities 93.6 95.8
Total liabilities 8,470.4 8,608.0
Commitments and contingencies (Note 14)
Shareholders' equity:    
Preferred shares and additional paid-in capital - $1.00 par, 30,000,000 shares authorized; 6,000 shares issued at June 30, 2021 and December 31, 2020, respectively; liquidation preference $25,000 144.0 144.0
Common shares - $1.00 par, 500,000,000 shares authorized; 46,158,916 and 46,009,966 shares issued at June 30, 2021 and December 31, 2020, respectively 46.2 46.0
Additional paid-in capital 1,383.1 1,380.2
Treasury shares (11,315,889 shares at June 30, 2021 and December 31, 2020, respectively) (455.1) (455.1)
Retained earnings 756.5 684.1
Accumulated other comprehensive income, net of taxes 23.2 58.6
Total shareholders' equity 1,897.9 1,857.8
Total liabilities and shareholders' equity $ 10,368.3 $ 10,465.8
v3.21.2
Condensed Consolidated Balance Sheets (Parenthetical) - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Statement of Financial Position [Abstract]    
Fixed maturities available-for-sale, at cost $ 3,981.2 $ 3,981.1
Allowance for expected credit losses 6.4 6.6
Equity securities, cost 129.5 162.5
Other investments, cost 412.3 429.4
Short-term investments, cost $ 529.2 $ 541.4
Preferred shares, par value (in dollars per share) $ 1.00 $ 1.00
Preferred shares, shares authorized (in shares) 30,000,000 30,000,000
Preferred shares, shares issued (in shares) 6,000 6,000
Liquidation preference (in dollars per share) $ 25,000 $ 25,000
Common shares, par value (in dollars per share) $ 1.00 $ 1.00
Common shares, shares authorized (in shares) 500,000,000 500,000,000
Common shares, shares issued (in shares) 46,158,916 46,009,966
Treasury shares (in shares) 11,315,889 11,315,889
v3.21.2
Condensed Consolidated Statements of Income (Loss) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Premiums and other revenue:        
Earned premiums $ 470.3 $ 433.4 $ 936.4 $ 868.4
Net investment income 52.7 1.4 97.1 37.0
Net realized investment gains (losses):        
Net realized investment gains 4.0 10.6 2.7 38.4
Change in fair value of equity securities 20.3 15.1 35.8 (24.2)
Credit gains (losses) on fixed maturity securities 0.4 (7.8) (0.7) (32.5)
Net realized investment gains (losses) 24.7 17.9 37.8 (18.3)
Total revenue 547.7 452.7 1,071.3 887.1
Expenses:        
Losses and loss adjustment expenses 271.6 273.2 579.2 554.1
Underwriting, acquisition and insurance expenses 177.3 159.8 353.7 327.9
Non-operating expenses 10.8 3.5 12.7 6.8
Interest expense 5.7 7.0 10.8 14.8
Fee and other (income) expense, net (0.8) (1.0) (0.7) (1.9)
Foreign currency exchange losses 4.4 4.3 5.7 5.2
Total expenses 469.0 446.8 961.4 906.9
Income (loss) before income taxes 78.7 5.9 109.9 (19.8)
Income tax provision 8.9 11.3 10.3 10.3
Net income (loss) 69.8 (5.4) 99.6 (30.1)
Dividends on preferred shares 2.7 0.0 5.3 0.0
Net income (loss) attributable to common shareholders 67.1 (5.4) 94.3 (30.1)
Net income (loss) attributable to common shareholders $ 67.1 $ (5.4) $ 94.3 $ (30.1)
Net income (loss) attributable to common shareholders per common share:        
Basic (in dollars per share) $ 1.93 $ (0.16) $ 2.72 $ (0.87)
Diluted (in dollars per share) 1.92 (0.16) 2.70 (0.87)
Dividends declared per common share (in dollars per share) $ 0.31 $ 0.31 $ 0.62 $ 0.62
Weighted average common shares:        
Basic (in shares) 34,820,649 34,634,353 34,766,948 34,551,935
Diluted (in shares) 35,012,780 34,634,353 34,983,804 34,551,935
v3.21.2
Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Statement of Comprehensive Income [Abstract]        
Net income (loss) $ 69.8 $ (5.4) $ 99.6 $ (30.1)
Other comprehensive income (loss):        
Foreign currency translation adjustments 3.4 (4.2) 2.5 (7.6)
Defined benefit pension plans:        
Net gain arising during the year 1.9 0.0 1.9 0.0
Unrealized gains (losses) on fixed maturity securities:        
Gains (losses) arising during the year 33.3 152.9 (28.8) 30.1
Reclassification adjustment for (gains) losses included in net income (15.2) (16.5) (19.2) (19.9)
Other comprehensive income (loss) before tax 23.4 132.2 (43.6) 2.6
Income tax provision related to other comprehensive income (loss):        
Net gain arising during the year 0.4 0.0 0.4 0.0
Gains (losses) arising during the year 5.5 27.0 (6.3) 5.9
Reclassification adjustment for gains included in net income (1.5) (2.6) (2.3) (0.7)
Income tax provision (benefit) related to other comprehensive income (loss) 4.4 24.4 (8.2) 5.2
Other comprehensive income (loss), net of tax 19.0 107.8 (35.4) (2.6)
Comprehensive income (loss) $ 88.8 $ 102.4 $ 64.2 $ (32.7)
v3.21.2
Condensed Consolidated Statements of Shareholders' Equity - USD ($)
$ in Millions
Total
Cumulative Effect, Period of Adoption, Adjustment
Preferred Shares and Additional Paid-in Capital
Common Shares
Additional Paid-In Capital
Treasury Shares
Retained Earnings
Retained Earnings
Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
Cumulative Effect, Period of Adoption, Adjustment
Beginning Balance at Dec. 31, 2019 $ 1,763.7     $ 45.7 $ 1,376.6 $ (455.1) $ 793.7   $ 2.8 $ 5.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]                    
Net income (loss) (30.1)           (30.1)      
Other comprehensive income - Change in fair value of fixed maturities, net of taxes 5.0               5.0  
Other comprehensive loss, net - Other (7.6)               (7.6)  
Activity under stock incentive plans 5.3     0.4 4.9          
Retirement of common shares (tax payments on equity compensation) (6.5)     (0.1) (6.4)          
Employee stock purchase plan 1.4       1.4          
Cash dividend declared - common shares $ (21.3)           (21.3)      
Accounting Standards Update [Extensible List] us-gaap:AccountingStandardsUpdate201613Member                  
Ending Balance at Jun. 30, 2020 $ 1,707.7 $ (2.2)   46.0 1,376.5 (455.1) 734.4 $ (7.9) 5.9 5.7
Beginning Balance at Mar. 31, 2020 1,613.5     45.9 1,374.2 (455.1) 750.4   (101.9)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                    
Net income (loss) (5.4)           (5.4)      
Other comprehensive income - Change in fair value of fixed maturities, net of taxes 112.0               112.0  
Other comprehensive loss, net - Other (4.2)               (4.2)  
Activity under stock incentive plans 2.2     0.1 2.1          
Retirement of common shares (tax payments on equity compensation) (0.7)     0.0 (0.7)          
Employee stock purchase plan 0.9       0.9          
Cash dividend declared - common shares (10.6)           (10.6)      
Ending Balance at Jun. 30, 2020 1,707.7 $ (2.2)   46.0 1,376.5 (455.1) 734.4 $ (7.9) 5.9 $ 5.7
Beginning Balance at Dec. 31, 2020 1,857.8   $ 144.0 46.0 1,380.2 (455.1) 684.1   58.6  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                    
Net income (loss) 99.6           99.6      
Preferred shares issued 0.0   0.0              
Other comprehensive income - Change in fair value of fixed maturities, net of taxes (39.4)               (39.4)  
Other comprehensive loss, net - Other 4.0               4.0  
Activity under stock incentive plans 4.5     0.2 4.3          
Retirement of common shares (tax payments on equity compensation) (2.4)     0.0 (2.4)          
Employee stock purchase plan 1.0       1.0          
Dividends on preferred shares (5.3)           (5.3)      
Cash dividend declared - common shares (21.9)           (21.9)      
Ending Balance at Jun. 30, 2021 1,897.9   144.0 46.2 1,383.1 (455.1) 756.5   23.2  
Beginning Balance at Mar. 31, 2021 1,821.0   144.0 46.1 1,381.3 (455.1) 700.5   4.2  
Increase (Decrease) in Stockholders' Equity [Roll Forward]                    
Net income (loss) 69.8           69.8      
Other comprehensive income - Change in fair value of fixed maturities, net of taxes 14.1               14.1  
Other comprehensive loss, net - Other 4.9               4.9  
Activity under stock incentive plans 2.3     0.1 2.2          
Retirement of common shares (tax payments on equity compensation) (1.0)     0.0 (1.0)          
Employee stock purchase plan 0.6       0.6          
Dividends on preferred shares (2.7)           (2.7)      
Cash dividend declared - common shares (11.1)           (11.1)      
Ending Balance at Jun. 30, 2021 $ 1,897.9   $ 144.0 $ 46.2 $ 1,383.1 $ (455.1) $ 756.5   $ 23.2  
v3.21.2
Condensed Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares
 3 Months Ended 6 Months Ended
May 06, 2021
May 07, 2020
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Statement of Stockholders' Equity [Abstract]            
Cash dividend declared - common shares (in dollars per share) $ 0.31 $ 0.31 $ 0.31 $ 0.31 $ 0.62 $ 0.62
v3.21.2
Condensed Consolidated Statements of Cash Flows - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Cash flows from operating activities:    
Net income (loss) $ 99.6 $ (30.1)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:    
Amortization and depreciation 14.8 14.1
Share-based payments expense 4.5 5.4
Deferred income tax benefit, net (6.8) (10.9)
Net realized investment (gains) losses (37.8) 18.3
Undistributed earnings from alternative investment portfolio (50.6) 20.9
Loss on disposals of long-lived assets, net 1.7 0.2
Change in:    
Accrued investment income 1.1 2.3
Receivables 151.3 37.3
Deferred acquisition costs (4.4) 5.1
Ceded unearned premiums (15.0) (115.6)
Reserves for losses and loss adjustment expenses (170.9) 98.5
Unearned premiums 6.6 82.2
Ceded reinsurance payable and funds held (22.5) (148.1)
Income taxes 8.5 18.8
Accrued underwriting expenses and other liabilities 23.8 (63.8)
Other, net (16.4) (37.7)
Cash provided by (used in) operating activities (12.5) (103.1)
Cash flows from investing activities:    
Sales of fixed maturity investments 616.4 746.0
Maturities and mandatory calls of fixed maturity investments 394.8 255.0
Sales of equity securities 33.5 8.1
Sales of other investments 62.3 94.2
Purchases of fixed maturity investments (983.3) (1,103.6)
Purchases of equity securities (1.8) (59.5)
Purchases of other investments (31.5) (14.3)
Change in foreign regulatory deposits and voluntary pools 35.9 5.0
Change in short-term investments 12.5 212.5
Settlements of foreign currency exchange forward contracts (8.8) 7.0
Proceeds from sale of Trident assets 0.0 38.0
Purchases of fixed assets (13.3) (7.6)
Other, net (37.6) (5.0)
Cash (used in) provided by investing activities 79.1 175.8
Cash flows from financing activities:    
Activity under stock incentive plans 0.8 1.0
Payment of cash dividends to preferred shareholders (5.3) 0.0
Payment of cash dividends to common shareholders (21.9) (21.3)
Cash used in financing activities (26.4) (20.3)
Effect of exchange rate changes on cash 1.7 (2.5)
Change in cash 41.9 49.9
Cash, beginning of year 148.8 137.8
Cash, end of period $ 190.7 $ 187.7
v3.21.2
Basis of Presentation
 6 Months Ended
Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Basis of Presentation Basis of Presentation
The accompanying consolidated financial statements of Argo Group International Holdings, Ltd. and its subsidiaries (“Argo Group,” “Argo,” “we,” “us,” “our” or the “Company”) have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions for Form 10-Q and Article 10 of Regulation S-X. Argo Group is an underwriter of specialty insurance products in the property and casualty market.
The preparation of interim financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. The major estimates reflected in our consolidated financial statements include, but are not limited to, reserves for losses and loss adjustment expenses; reinsurance recoverables, including the reinsurance recoverables allowance for expected credit losses; estimates of written and earned premiums; reinsurance premium receivable; fair value of investments and assessment of potential impairment, including the allowance for credit losses on fixed maturity securities; valuation of goodwill and intangibles and our deferred tax asset valuation allowance. Actual results could materially differ from those estimates. Certain financial information that is normally included in annual financial statements, including certain financial statement footnotes, prepared in accordance with GAAP, is not required for interim reporting purposes and has been condensed or omitted. These statements should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2020, filed with the Securities and Exchange Commission ("SEC") on March 15, 2021.
The interim financial information as of, and for, the three and six months ended, June 30, 2021 and 2020 is unaudited. However, in the opinion of management, the interim information includes all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results presented for the interim periods. The operating results for the interim periods are not necessarily indicative of the results to be expected for the full year. All significant intercompany amounts have been eliminated in consolidation. Certain reclassifications have been made to financial information presented for prior years to conform to the current year’s presentation.
Update on Trident Transaction
On April 30, 2020, we sold our Trident Public Risk Solutions (“Trident”) brand and underwriting platform. During the second quarter of 2021, the parties to the transaction agreed to amend the transaction and other related agreements associated with the sale of Trident to eliminate certain lines of business from the transaction. As a result, we recognized a $16.5 million reduction in the original gain on sale during the second quarter of 2021. Additionally, we recognized a $5.0 million gain during the second quarter of 2021 related to meeting certain post-closing performance conditions. This transaction is included in "Net realized investment gains (losses)" in our Consolidated Statements of Income (Loss) for the three and six months ended June 30, 2021.
v3.21.2
Recently Issued Accounting Pronouncements
 6 Months Ended
Jun. 30, 2021
Accounting Policies [Abstract]  
Recently Issued Accounting Pronouncements Recently Issued Accounting PronouncementsThe Company has evaluated recently issued accounting pronouncements and determined none are material to our results of operations or financial position reported herein.
v3.21.2
Investments
 6 Months Ended
Jun. 30, 2021
Investments, Debt and Equity Securities [Abstract]  
Investments InvestmentsIncluded in “Total investments” in our Consolidated Balance Sheets at June 30, 2021 and December 31, 2020 is $93.0 million and $140.3 million, respectively, of assets managed on behalf of the trade capital providers, who are third-party participants that provide underwriting capital to the operations of Syndicates 1200 and 1910.
Fixed Maturities
The amortized cost, gross unrealized gains, gross unrealized losses, allowance for credit losses, and fair value of fixed maturity investments were as follows:
June 30, 2021
(in millions)Amortized
Cost		Gross
Unrealized
Gains		Gross
Unrealized
Losses		Allowance for Credit LossesFair
Value
Fixed maturities
U.S. Governments$350.7 $8.6 $1.5 $— $357.8 
Foreign Governments209.9 4.1 1.1 0.2 212.7 
Obligations of states and political subdivisions185.5 7.5 0.5 — 192.5 
Corporate bonds1,956.0 55.4 11.0 6.2 1,994.2 
Commercial mortgage-backed securities342.2 10.6 1.7 — 351.1 
Residential mortgage-backed securities510.8 12.0 3.6 — 519.2 
Asset-backed securities121.1 2.6 0.4 — 123.3 
Collateralized loan obligations305.0 2.6 0.7 — 306.9 
Total fixed maturities$3,981.2 $103.4 $20.5 $6.4 $4,057.7 
December 31, 2020
(in millions)Amortized
Cost		Gross
Unrealized
Gains		Gross
Unrealized
Losses		Allowance for Credit LossesFair
Value
Fixed maturities
U.S. Governments$385.4 $14.7 $0.3 $— $399.8 
Foreign Governments284.1 11.6 0.7 0.2 294.8 
Obligations of states and political subdivisions163.1 7.7 0.3 0.1 170.4 
Corporate bonds1,925.9 75.3 13.3 6.1 1,981.8 
Commercial mortgage-backed securities324.8 15.2 0.3 — 339.7 
Residential mortgage-backed securities491.4 17.4 0.6 — 508.2 
Asset-backed securities120.5 2.9 0.4 0.2 122.8 
Collateralized loan obligations285.9 4.9 1.2 — 289.6 
Total fixed maturities$3,981.1 $149.7 $17.1 $6.6 $4,107.1 
Contractual Maturity
The amortized cost and fair values of fixed maturity investments as of June 30, 2021, by contractual maturity, were as follows:
(in millions)Amortized
Cost		Fair
Value
Due in one year or less$284.5 $288.7 
Due after one year through five years1,596.3 1,630.2 
Due after five years through ten years714.6 729.9 
Due after ten years106.7 108.4 
Structured securities1,279.1 1,300.5 
Total$3,981.2 $4,057.7 
The expected maturities may differ from the contractual maturities because debtors may have the right to call or prepay obligations.
Other Investments
Details regarding the carrying value and unfunded investment commitments of other investments as of June 30, 2021 and December 31, 2020 were as follows:
June 30, 2021
(in millions)Carrying
Value		Unfunded
Commitments
Investment Type
Hedge funds$99.4 $— 
Private equity243.1 67.9 
Overseas deposits65.1 — 
Other4.7 — 
Total other investments$412.3 $67.9 
December 31, 2020
(in millions)Carrying
Value		Unfunded
Commitments
Investment Type
Hedge funds$111.2 $— 
Private equity211.4 80.0 
Overseas deposits102.1 — 
Other4.7 — 
Total other investments$429.4 $80.0 
The following describes each investment type:
•Hedge funds: Hedge funds include funds that primarily buy and sell stocks, including short sales, multi-strategy credit, relative value credit and distressed credit.
•Private equity: Private equity includes buyout funds, real asset/infrastructure funds, credit special situations funds, mezzanine lending funds and direct investments and strategic non-controlling minority investments in private companies that are principally accounted for using the equity method of accounting.
•Overseas deposits: Overseas deposits are principally invested in short-term sovereign fixed income and investment grade corporate securities and international stocks.
•Other: Other includes participation in investment pools.
Unrealized Losses
An aging of unrealized losses on our investments in fixed maturities is presented below:
June 30, 2021Less Than One YearOne Year or GreaterTotal
(in millions)Fair
Value		Unrealized
Losses		Fair
Value		Unrealized
Losses		Fair
Value		Unrealized
Losses
Fixed maturities
U.S. Governments$106.6 $1.5 $— $— $106.6 $1.5 
Foreign Governments97.6 0.9 — 0.2 97.6 1.1 
Obligations of states and political subdivisions22.4 0.3 0.4 0.2 22.8 0.5 
Corporate bonds476.9 8.6 26.9 2.4 503.8 11.0 
Commercial mortgage-backed securities76.6 1.5 7.0 0.2 83.6 1.7 
Residential mortgage-backed securities157.6 3.5 5.1 0.1 162.7 3.6 
Asset-backed securities16.4 0.4 3.1 — 19.5 0.4 
Collateralized loan obligations100.3 0.7 2.8 — 103.1 0.7 
Total fixed maturities$1,054.4 $17.4 $45.3 $3.1 $1,099.7 $20.5 
December 31, 2020Less Than One YearOne Year or GreaterTotal
(in millions)Fair
Value		Unrealized
Losses		Fair
Value		Unrealized
Losses		Fair
Value		Unrealized
Losses
Fixed maturities
U.S. Governments$40.6 $0.3 $— $— $40.6 $0.3 
Foreign Governments18.0 0.5 0.1 0.2 18.1 0.7 
Obligations of states and political subdivisions5.2 0.3 — — 5.2 0.3 
Corporate bonds202.5 6.7 17.5 6.6 220.0 13.3 
Commercial mortgage-backed securities21.8 0.3 — — 21.8 0.3 
Residential mortgage-backed securities74.4 0.4 3.0 0.2 77.4 0.6 
Asset-backed securities4.6 0.4 — — 4.6 0.4 
Collateralized loan obligations121.1 0.9 49.1 0.3 170.2 1.2 
Total fixed maturities$488.2 $9.8 $69.7 $7.3 $557.9 $17.1 
We hold a total of 5,244 fixed maturity securities, of which 477 were in an unrealized loss position for less than one year and 78 were in an unrealized loss position for a period one year or greater as of June 30, 2021.
Allowance for Credit Losses
For fixed maturities with a decline in the fair value between the amortized cost due to credit-related factors, an allowance is established for the difference between the estimated recoverable value and amortized cost with a corresponding charge to realized investment losses in the Statement of Income (Loss). The allowance is limited to the difference between amortized cost and fair value. The estimated recoverable value is the present value of cash flows expected to be collected, as determined by management. The difference between fair value and amortized cost that is not associated with credit-related factors is recognized in the Statement of Comprehensive Income (Loss). Accrued interest is excluded from the measurement of the allowance for credit losses.
When determining if a credit loss has been incurred, we may consider the historical performance of the security, available market information and security specific considerations such as the priority payment of the security. In addition, inputs used in our analysis include, but are not limited to, credit ratings and downgrades, delinquency rates, missed scheduled interest or principal payments, purchase yields, underlying asset performance, collateral types, modeled default rates, modeled severity rates, call/prepayment rates, expected cash flows, industry concentrations, and potential or filed bankruptcies or restructurings.
We evaluate for credit losses each quarter. If we determine that all or a portion of a fixed maturity is uncollectible, the uncollectible amortized cost is written off with a corresponding reduction to the allowance for credit losses. If we collect cash flows that were previously written off, the recovery is recognized in realized investment gains. We also consider whether we intend to sell an available-for-sale security or if it is more likely than not that we will be required to sell the security before recovery of its amortized cost. In these instances, a decline in fair value is recognized in net realized gains (losses) in the Statement of Income based on the fair value of the security at the time of assessment, resulting in a new cost basis for the security.
The following table presents a roll-forward of the changes in allowance for credit losses on available-for-sale fixed maturities by industry category:
(in millions)Foreign GovernmentsObligations of states and political subdivisionsCorporate bondsAsset backed securitiesTotal
Beginning balance, January 1, 2021$0.2 $0.1 $6.1 $0.2 $6.6 
Securities for which allowance was not previously recorded— — 2.0 — 2.0 
Securities sold during the period— — (0.9)— (0.9)
Additional net increases (decreases) in existing allowance— (0.1)(1.0)(0.2)(1.3)
Ending balance, June 30, 2020$0.2 $— $6.2 $— $6.4 
Total credit impairment (gains) losses included in net realized investment gains (losses) in the Consolidated Statement of Income was $(0.4) million and $0.7 million for the three and six months ended June 30, 2021, respectively. Total credit impairment losses included in net realized investment gains (losses) in the Consolidated Statement of Income was $7.8 million and $32.5 million for the three and six months ended June 30, 2020, respectively.
Investment Gains and Losses
The following table presents our gross realized investment gains (losses):
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Realized gains on fixed maturities and other
Fixed maturities$17.5 $2.5 $23.0 $23.3 
Other investments, including short-terms5.8 11.5 8.0 59.7 
Other assets3.3 32.5 3.3 32.5 
26.6 46.5 34.3 115.5 
Realized losses on fixed maturities and other
Fixed maturities(3.0)(10.5)(4.5)(18.2)
Other investments, including short-terms(8.8)(14.4)(14.5)(46.3)
Other assets(11.5)— (11.5)— 
Credit losses on fixed maturities0.4 (7.8)(0.7)(32.5)
(22.9)(32.7)(31.2)(97.0)
Equity securities
Net realized (losses) on equity securities0.7 (11.0)(1.1)(12.6)
Change in unrealized gains (losses) on equity securities held at the end of the period20.3 15.1 35.8 (24.2)
Net realized gains (losses) on equity securities21.0 4.1 34.7 (36.8)
Net realized investment and other gains (losses) before income taxes24.7 17.9 37.8 (18.3)
Income tax (benefit) provision5.2 6.7 7.9 (1.3)
Net realized investment gains (losses), net of income taxes$19.5 $11.2 $29.9 $(17.0)
The cost of securities sold is based on the specific identification method.
Changes in unrealized gains (losses) related to investments are summarized as follows:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Change in unrealized losses
Fixed maturities$18.0 $136.2 $(47.7)$24.4 
Other investments— — — (14.2)
Other and short-term investments0.1 0.2 (0.3)— 
Net unrealized investment gains (losses) before income taxes18.1 136.4 (48.0)10.2 
Income tax provision (benefit)4.0 24.4 (8.6)5.2 
Net unrealized investment gains (losses), net of income taxes$14.1 $112.0 $(39.4)$5.0 
Foreign Currency Exchange Forward Contracts
We enter into foreign currency exchange forward contracts to manage operational currency exposure on our Canadian dollar investment portfolio and certain catastrophic events, minimize negative impacts to investment portfolio returns and gain exposure to a total return strategy which invests in multiple currencies.  The currency forward contracts are carried at fair value in our Consolidated Balance Sheets in “Other liabilities” and “Other assets” at June 30, 2021 and December 31, 2020, respectively. The net realized gains and (losses) are included in “Net realized investment gains (losses)” in our Consolidated Statements of Income (Loss).
The fair value of our foreign currency exchange forward contracts as of June 30, 2021 and December 31, 2020 was as follows:
(in millions)June 30, 2021December 31, 2020
Operational currency exposure$(1.1)$0.4 
Asset manager investment exposure1.0 (0.2)
Total return strategy— 0.7 
Total$(0.1)$0.9 
The following table represents our gross investment realized gains and losses on our foreign currency exchange forward contracts:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Realized gains
Operational currency exposure$3.2 $0.5 $7.1 $5.9 
Asset manager investment exposure0.9 0.2 1.8 1.0 
Total return strategy— 8.2 6.1 33.2 
Gross realized investment gains4.1 8.9 15.0 40.1 
Realized losses
Operational currency exposure(3.5)(3.0)(12.7)(4.7)
Asset manager investment exposure(0.8)(0.6)(0.8)(1.0)
Total return strategy— (8.6)(5.1)(36.6)
Gross realized investment losses(4.3)(12.2)(18.6)(42.3)
Net realized investment (losses) gains on foreign currency exchange forward contracts
$(0.2)$(3.3)$(3.6)$(2.2)
Regulatory Deposits, Pledged Securities and Letters of Credit
We are required to maintain assets on deposit with various regulatory authorities to support our insurance and reinsurance operations.  We maintain assets pledged as collateral in support of irrevocable letters of credit issued under the terms of certain reinsurance agreements for reported loss and loss expense reserves. The following table presents our components of restricted assets:
(in millions)June 30, 2021December 31, 2020
Securities on deposit for regulatory and other purposes$214.5 $227.5 
Securities pledged as collateral for letters of credit and other190.6 189.4 
Securities and cash on deposit supporting Lloyd’s business353.0 409.2 
Total restricted investments$758.1 $826.1 
Fair Value Measurements
Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurement assumes that the transaction to sell the asset or transfer the liability occurs in the principal market for the asset or liability, or in the absence of a principal market, the most advantageous market. Market participants are buyers and sellers in the principal (or most advantageous) market that are independent, knowledgeable, able to transact for the asset or liability and willing to transfer the asset or liability.
Valuation techniques consistent with the market approach, income approach and/or cost approach are used to measure fair value. The inputs of these valuation techniques are categorized into three levels.
•Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that can be accessed at the reporting date. We define actively traded as a security that has traded in the past seven days. We receive one quote per instrument for Level 1 inputs.
•Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. We receive one quote per instrument for Level 2 inputs.
•Level 3 inputs are unobservable inputs. Unobservable inputs reflect our own judgments about the assumptions market participants would use in pricing the asset or liability based on the best information available in the circumstances.
We receive fair value prices from third-party pricing services and our outside investment managers. These prices are determined using observable market information such as dealer quotes, market spreads, cash flows, yield curves, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things. We have reviewed the processes used by the third-party providers for pricing the securities and have determined that these processes result in fair values consistent with GAAP requirements. In addition, we review these prices for reasonableness, and have not adjusted any prices received from the third-party providers as of June 30, 2021 and December 31, 2020. A description of the valuation techniques we use to measure assets at fair value is as follows:
Fixed Maturities (Available-for-Sale) Levels 1 and 2:
•United States Treasury securities are typically valued using Level 1 inputs. For these securities, we obtain fair value measurements from third-party pricing services using quoted prices (unadjusted) in active markets at the reporting date.
•United States Government agencies, non-U.S. Government securities, obligations of states and political subdivisions, credit securities and foreign denominated government and credit securities are reported at fair value using Level 2 inputs. For these securities, we obtain fair value measurements from third-party pricing services. Observable data may include dealer quotes, market spreads, yield curves, live trading levels, trade execution data, credit information and the security’s terms and conditions, among other things.
•Asset and mortgage-backed securities and collateralized loan obligations are reported at fair value using Level 2 inputs. For these securities, we obtain fair value measurements from third-party pricing services. Observable data may include dealer quotes, market spreads, cash flows, yield curves, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things.
Fixed Maturities (Available-for-Sale) Levels 3: We own term loans that are valued using unobservable inputs.
Equity Securities Level 1: Equity securities are principally reported at fair value using Level 1 inputs. For these securities, we obtain fair value measurements from a third-party pricing service using quoted prices (unadjusted) in active markets at the reporting date.
Equity Securities Level 3: We own certain equity securities that are reported at fair value using Level 3 inputs. The valuation techniques for these securities include the following:
•Fair value measurements for an investment in an equity fund obtained by applying final prices provided by the administrator of the fund, which is based upon certain estimates and assumptions.
•Fair value measurements from brokers and independent valuation services, both based upon estimates, assumptions and other unobservable inputs.
Other Investments Level 2: Foreign regulatory deposits are assets held in trust in jurisdictions where there is a legal and regulatory requirement to maintain funds locally in order to protect policyholders. Lloyd’s is the appointed investment manager for the funds. These assets are invested in short-term government securities, agency securities and corporate bonds and are valued using Level 2 inputs based upon values obtained from Lloyd’s.
Short-term Investments: Short-term investments are principally reported at fair value using Level 1 inputs, with the exception of short-term corporate and governmental bonds reported at fair value using Level 2 inputs as described in the fixed maturities section above. Values for the investments categorized as Level 1 are obtained from various financial institutions as of the reporting date.
Based on an analysis of the inputs, our financial assets measured at fair value on a recurring basis have been categorized as follows:
Fair Value Measurements at Reporting Date Using
(in millions)June 30,
2021
Level 1 (a)
Level 2 (b)
Level 3 (c)
Fixed maturities
U.S. Governments$357.8 $343.6 $14.2 $— 
Foreign Governments212.7 — 212.7 — 
Obligations of states and political subdivisions192.5 — 192.5 — 
Corporate bonds1,994.2 — 1,990.6 3.6 
Commercial mortgage-backed securities351.1 — 351.1 — 
Residential mortgage-backed securities519.2 — 519.2 — 
Asset-backed securities123.3 — 123.3 — 
Collateralized loan obligations306.9 — 306.9 — 
Total fixed maturities4,057.7 343.6 3,710.5 3.6 
Equity securities185.7 162.0 — 23.7 
Other investments65.6 — 65.6 — 
Short-term investments530.2 518.8 11.3 0.1 
$4,839.2 $1,024.4 $3,787.4 $27.4 
(a)Quoted prices in active markets for identical assets
(b)Significant other observable inputs
(c)Significant unobservable inputs

Fair Value Measurements at Reporting Date Using
(in millions)December 31,
2020
Level 1 (a)
Level 2 (b)
Level 3 (c)
Fixed maturities
U.S. Governments$399.8 $383.5 $16.3 $— 
Foreign Governments294.8 — 294.8 — 
Obligations of states and political subdivisions170.4 — 170.4 — 
Corporate bonds1,981.8 — 1,974.8 7.0 
Commercial mortgage-backed securities339.7 — 339.7 — 
Residential mortgage-backed securities508.2 — 508.2 — 
Asset-backed securities122.8 — 122.8 — 
Collateralized loan obligations289.6 — 289.6 — 
Total fixed maturities4,107.1 383.5 3,716.6 7.0 
Equity securities176.7 159.2 — 17.5 
Other investments102.5 0.4 102.1 — 
Short-term investments542.6 526.5 16.1 — 
$4,928.9 $1,069.6 $3,834.8 $24.5 
(a)Quoted prices in active markets for identical assets
(b)Significant other observable inputs
(c)Significant unobservable inputs
The fair value measurements in the tables above do not equal “Total investments” on our Consolidated Balance Sheets as they exclude certain other investments that are accounted for under the equity-method of accounting.
A reconciliation of the beginning and ending balances for the investments categorized as Level 3 are as follows:
Fair Value Measurements Using Observable Inputs (Level 3)
(in millions)Corporate BondsEquity
Securities		Short Term InvestmentsTotal
Beginning balance, January 1, 2021$7.0 $17.5 $— $24.5 
Transfers into Level 3— — — — 
Transfers out of Level 3— — — — 
Total gains or losses (realized/unrealized):
Included in net income — 6.2 — 6.2 
Included in other comprehensive income0.1 — — 0.1 
Purchases, issuances, sales, and settlements:
Purchases— — 0.1 0.1 
Issuances— — — — 
Sales(3.5)— — (3.5)
Settlements— — — — 
 Ending balance, June 30, 2021$3.6 $23.7 $0.1 $27.4 
Amount of total gains or losses for the year included in net income attributable to the change in unrealized gains or losses relating to assets still held at June 30, 2021$— $— $— $— 
(in millions)Credit FinancialEquity
Securities		Total
Beginning balance, January 1, 2020$7.4 $18.2 $25.6 
Transfers into Level 3— — — 
Transfers out of Level 3— — — 
Total gains or losses (realized/unrealized):
Included in net income— (5.9)(5.9)
Included in other comprehensive loss(0.5)— (0.5)
Purchases, issuances, sales, and settlements:
Purchases0.1 5.2 5.3 
Issuances— — — 
Sales— — — 
Settlements— — — 
 Ending balance, December 31, 2020$7.0 $17.5 $24.5 
Amount of total gains or losses for the year included in net income attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2020$— $— $— 
At June 30, 2021 and December 31, 2020, we did not have any financial assets or financial liabilities measured at fair value on a nonrecurring basis or any financial liabilities on a recurring basis.
v3.21.2
Allowance for Credit Losses
 6 Months Ended
Jun. 30, 2021
Credit Loss [Abstract]  
Allowance for Credit Losses Allowance for Credit Losses
Premiums receivable
The following table represents the balances of premiums receivable, net of allowance for expected credit losses, at June 30, 2021 and January 1, 2021, and the changes in the allowance for expected credit losses for the six months ended June 30, 2021.
(in millions)Premiums Receivable, Net of Allowance for Estimated Uncollectible PremiumsAllowance for Estimated Uncollectible Premiums
Balance, January 1, 2021$679.8 $9.4 
Current period change for estimated uncollectible premiums(0.1)
Write-offs of uncollectible premiums receivable(0.6)
Foreign exchange adjustments— 
Balance, June 30, 2021$681.7 $8.7 
Reinsurance Recoverables
The following table presents the balances of reinsurance recoverables, net of the allowance for estimated uncollectible reinsurance, at June 30, 2021 and January 1, 2021, and changes in the allowance for estimated uncollectible reinsurance for the six months ended June 30, 2021.
(in millions) Reinsurance Recoverables, Net of Allowance for Estimated Uncollectible ReinsuranceAllowance for Estimated Uncollectible Reinsurance
Balance, January 1, 2021$3,009.0 $4.1 
Current period change for estimated uncollectible reinsurance(0.3)
Write-offs of uncollectible reinsurance recoverables— 
Balance, June 30, 2021$2,859.9 $3.8 
We primarily utilize A.M. Best credit ratings when determining the allowance, adjusted as needed based on our historical experience with the reinsurers. Certain of our reinsurance recoverables are collateralized by letters of credit, funds held or trust agreements.
v3.21.2
Reserves for Losses and Loss Adjustment Expenses
 6 Months Ended
Jun. 30, 2021
Insurance [Abstract]  
Reserves for Losses and Loss Adjustment Expenses Reserves for Losses and Loss Adjustment Expenses
The following table provides a reconciliation of reserves for losses and loss adjustment expenses (“LAE”):
For the Six Months Ended
June 30,
(in millions)20212020
Net reserves beginning of the year$2,906.1 $2,722.7 
Net AIL reserves acquired— 27.9 
Add:
Losses and LAE incurred during current calendar year, net of reinsurance:
Current accident year579.4 549.6 
Prior accident years(0.2)4.5 
Losses and LAE incurred during calendar year, net of reinsurance579.2 554.1 
Deduct:
Net reserve ceded - reinsurance to close transaction for years of account 2017 and prior (1)
207.8 — 
Losses and LAE payments made during current calendar year, net of reinsurance:
Current accident year59.7 125.3 
Prior accident years376.0 451.5 
Losses and LAE payments made during current calendar year, net of reinsurance:435.7 576.8 
Change in participation interest (2)
12.8 33.0 
Foreign exchange adjustments6.1 (8.5)
Net reserves - end of period2,860.7 2,752.4 
Add:
Reinsurance recoverables on unpaid losses and LAE, end of period2,377.9 2,463.9 
Gross reserves - end of period$5,238.6 $5,216.3 
(1)Amount represents reserves ceded under the reinsurance to close transaction with RiverStone for Lloyd’s years of account 2017 and prior, effective January 1, 2020.
(2)Amount represents the change in reserves due to changing our participation in Syndicates 1200 and 1910.
Reserves for losses and LAE represent the estimated indemnity cost and related adjustment expenses necessary to investigate and settle claims. Such estimates are based upon individual case estimates for reported claims, estimates from ceding companies for reinsurance assumed and actuarial estimates for losses that have been incurred but not yet reported to the insurer. Any change in probable ultimate liabilities is reflected in current operating results.

The impact from the (favorable) unfavorable development of prior accident years’ loss and LAE reserves on each reporting segment is presented below: 
For the Six Months Ended
June 30,
(in millions)20212020
U.S. Operations$(0.9)$2.7 
International Operations(1.9)1.1 
Run-off Lines2.6 0.7 
Total (favorable) unfavorable prior-year development$(0.2)$4.5 
The following describes the primary factors behind each segment’s prior accident year reserve development for the six months ended June 30, 2021 and 2020:
Six months ended June 30, 2021:
•U.S. Operations: Favorable development primarily in specialty lines, largely offset by unfavorable development in liability lines.
•International Operations: Favorable development in property lines, including losses associated with prior year catastrophe losses, partially offset by unfavorable development in Argo Insurance Bermuda due to large claim movements and unfavorable development in our surety business in Europe.
•Run-off Lines: Unfavorable loss reserve development in other run-off lines.
Six months ended June 30, 2020:
•U.S. Operations: Unfavorable development in general liability, commercial auto liability and special property partially offset by favorable development in specialty related to our surety business unit.
•International Operations: Unfavorable development in general liability and surety lines offset by favorable development in special property and specialty.
•Run-off Lines: Unfavorable development in other run-off lines partially offset by favorable development in risk management workers compensation.
In the opinion of management, our reserves represent the best estimate of our ultimate liabilities, based on currently known facts, current law, current technology and reasonable assumptions where facts are not known. Due to the significant uncertainties and related management judgments, there can be no assurance that future favorable or unfavorable loss development, which may be material, will not occur.
v3.21.2
Disclosures about Fair Value of Financial Instruments
 6 Months Ended
Jun. 30, 2021
Fair Value Disclosures [Abstract]  
Disclosures about Fair Value of Financial Instruments Disclosures about Fair Value of Financial Instruments
Cash. The carrying amount approximates fair value.
Investment securities and short-term investments. See Note 3, “Investments,” for additional information.
Premiums receivable and reinsurance recoverables on paid losses. The carrying value of current receivables and reinsurance recoverables on paid losses approximates fair value.
Debt. At June 30, 2021 and December 31, 2020, the fair value of our debt instruments is determined using both Level 1 and Level 2 inputs, as previously defined in Note 3, “Investments.”
We receive fair value prices from third-party pricing services for our financial instruments as well as for similar financial instruments. These prices are determined using observable market information such as publicly traded quoted prices, and trading prices for similar financial instruments actively being traded in the current market. We have reviewed the processes used by the third-party providers for pricing the securities and have determined that these processes result in fair values consistent with GAAP requirements. In addition, we review these prices for reasonableness, and have not adjusted any prices received from the third-party providers as of June 30, 2021 and December 31, 2020. A description of the valuation techniques we use to measure these liabilities at fair value is as follows:
Senior Unsecured Fixed Rate Notes Level 1:
•Our senior unsecured fixed rate notes are valued using Level 1 inputs. For these securities, we obtain fair value measurements from a third-party pricing service using quoted prices (unadjusted) in active markets at the reporting date.
Junior Subordinated Debentures and Floating Rate Loan Stock Level 2:
•Our trust preferred debentures, subordinated debentures and floating rate loan stock are typically valued using Level 2 inputs. For these securities, we obtain fair value measurements from a third-party pricing service using quoted prices for similar securities being traded in active markets at the reporting date, as our specific debt instruments are more infrequently traded.
A summary of our financial instruments whose carrying value did not equal fair value is shown below:
June 30, 2021December 31, 2020
(in millions)Carrying
Amount		Fair
Value		Carrying
Amount		Fair
Value
Junior subordinated debentures:
Trust preferred debentures$172.7 $174.3 $172.7 $173.6 
Subordinated debentures85.3 92.7 85.1 92.3 
Total junior subordinated debentures258.0 267.0 257.8 265.9 
Senior unsecured fixed rate notes140.2 148.9 140.2 146.7 
Floating rate loan stock60.4 61.0 60.7 61.0 
458.6 476.9 458.7 473.6 
Based on an analysis of the inputs, our financial instruments measured at fair value for disclosure purposes have been categorized as follows:
Fair Value Measurements at Reporting Date Using
(in millions)June 30, 2021Level 1 (a)Level 2 (b)Level 3 (c)
Junior subordinated debentures:
Trust preferred debentures$174.3 $— $174.3 $— 
Subordinated debentures92.7 — 92.7 — 
Total junior subordinated debentures267.0 — 267.0 — 
Senior unsecured fixed rate notes148.9 148.9 — — 
Floating rate loan stock61.0 — 61.0 — 
476.9 148.9 328.0 — 
(a)Quoted prices in active markets for identical assets
(b)Significant other observable inputs
(c)Significant unobservable inputs
Fair Value Measurements at Reporting Date Using
(in millions)December 31, 2020Level 1 (a)Level 2 (b)Level 3 (c)
Junior subordinated debentures:
Trust preferred debentures$173.6 $— $173.6 $— 
Subordinated debentures92.3 — 92.3 — 
Total junior subordinated debentures265.9 — 265.9 — 
Senior unsecured fixed rate notes146.7 146.7 — — 
Floating rate loan stock61.0 — 61.0 — 
473.6 146.7 326.9 — 
(a)Quoted prices in active markets for identical assets
(b)Significant other observable inputs
(c)Significant unobservable inputs
v3.21.2
Shareholders' Equity
 6 Months Ended
Jun. 30, 2021
Equity [Abstract]  
Shareholders' Equity Shareholders’ Equity
On May 6, 2021, our Board of Directors declared a quarterly cash dividend in the amount of $0.31 on each common share outstanding. On June 4, 2021, we paid $11.1 million to our shareholders of record on May 21, 2021.

On May 6, 2021, our Board of Directors declared a quarterly cash dividend in the amount of $437.500 per share on our 7.00% Resettable Fixed Rate Preference Shares, Series A, par value of $1.00 per share, with a liquidation preference of $25,000 per share (the “Series A Preference Shares”). Holders of depositary shares, each representing a 1/1,000th interest in a Series A Preference Share (the “Depositary Shares”), received $0.437500 per Depositary Share. On June 15, 2021, we paid $2.7 million to our shareholders of record of Series A Preference Shares on May 30, 2021.
On May 7, 2020, our Board of Directors declared a quarterly cash dividend in the amount of $0.31 on each common share outstanding. On June 12, 2020, we paid $10.6 million to our shareholders of record on May 29, 2020.
On May 3, 2016, our Board of Directors authorized the repurchase of up to $150.0 million of our common shares (“2016 Repurchase Authorization”). The 2016 Repurchase Authorization supersedes all previous repurchase authorizations. As of June 30, 2021, availability under the 2016 Repurchase Authorization for future repurchases of our common shares was $53.3 million.
We did not repurchase any common shares for the six months ended June 30, 2021.
v3.21.2
Accumulated Other Comprehensive Income (Loss)
 6 Months Ended
Jun. 30, 2021
Equity [Abstract]  
Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss)
A summary of changes in accumulated other comprehensive (loss) income, net of taxes (where applicable) by component for the six months ended June 30, 2021 and 2020 is presented below:
(in millions)Foreign Currency Translation AdjustmentsUnrealized
Holding Gains
on Securities		Defined Benefit Pension PlansTotal
Balance, January 1, 2021$(37.9)$105.1 $(8.6)$58.6 
Other comprehensive loss before reclassifications2.5 (22.5)1.5 (18.5)
Amounts reclassified from accumulated other comprehensive loss— (16.9)— (16.9)
Net current-period other comprehensive loss2.5 (39.4)1.5 (35.4)
Balance, June 30, 2021$(35.4)$65.7 $(7.1)$23.2 
(in millions)Foreign Currency Translation Adjustments Unrealized
Holding Gains
on Securities		Defined Benefit Pension PlansTotal
Balance, January 1, 2020$(22.6)$33.5 $(8.1)$2.8 
Other comprehensive income before reclassifications(7.6)24.2 — 16.6 
Amounts reclassified from accumulated other comprehensive loss— (19.2)— (19.2)
Net current-period other comprehensive loss(7.6)5.0 — (2.6)
Cumulative effect of adoption of ASU 2016-13— 5.7 — 5.7 
Balance, June 30, 2020$(30.2)$44.2 $(8.1)$5.9 
The amounts reclassified from accumulated other comprehensive income (loss) shown in the above table have been included in the following captions in our Consolidated Statements of Income (Loss):
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Unrealized gains and losses on securities:
Net realized investment gains$(15.2)$(16.5)$(19.2)$(19.9)
Provision (benefit) for income taxes1.5 2.6 2.3 0.7 
Net of taxes$(13.7)$(13.9)$(16.9)$(19.2)
Income tax effects are released from accumulated other comprehensive income (loss) for unrealized gains or losses when the gains or losses are realized, and are taxed at the statutory rate based on jurisdiction of the underlying transaction.
v3.21.2
Net Income (Loss) Per Common Share
 6 Months Ended
Jun. 30, 2021
Earnings Per Share [Abstract]  
Net Income (Loss) Per Common Share Net Income (Loss) Per Common Share
The following table presents the calculation of net income (loss) per common share on a basic and diluted basis:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions, except number of shares and per share amounts)2021202020212020
Net income (loss)$69.8 $(5.4)$99.6 $(30.1)
Less: Preferred share dividends2.7 — 5.3 — 
Net income (loss) attributable to common shareholders67.1 (5.4)94.3 (30.1)
Weighted average common shares outstanding - basic34,820,649 34,634,353 34,766,948 34,551,935 
Effect of dilutive securities:
Equity compensation awards192,131 — 216,856 — 
Weighted average common shares outstanding - diluted35,012,780 34,634,353 34,983,804 34,551,935 
Net income (loss) per common share:
Basic$1.93 $(0.16)$2.72 $(0.87)
Diluted$1.92 $(0.16)$2.70 $(0.87)
Excluded from the weighted average common shares outstanding calculation at June 30, 2021 and 2020 are 11,315,889 shares, which are held as treasury shares. The shares are excluded as of their repurchase date. There were 36,219 and 48,272 weighted average shares excluded from the computation of diluted net income per common share because they were anti-dilutive for the three and six months ended June 30, 2021, respectively. Due to the net loss incurred for the three and six months ended June 30, 2020, all of the potentially dilutive securities were anti-dilutive, and therefore, omitted from the calculation.
v3.21.2
Supplemental Cash Flow Information
 6 Months Ended
Jun. 30, 2021
Supplemental Cash Flow Elements [Abstract]  
Supplemental Cash Flow Information Supplemental Cash Flow InformationInterest paid and income taxes paid (recovered) were as follows:
For the Six Months Ended
June 30,
(in millions)20212020
Senior unsecured fixed rate notes$4.7 $4.7 
Junior subordinated debentures5.0 6.7 
Other indebtedness1.1 3.4 
Total interest paid$10.8 $14.8 
Income taxes paid8.9 1.6 
Income taxes recovered(0.1)(0.7)
Income taxes paid, net$8.8 $0.9 
v3.21.2
Share-based Compensation
 6 Months Ended
Jun. 30, 2021
Share-based Payment Arrangement [Abstract]  
Share-based Compensation Share-based Compensation
Argo Group’s 2019 Omnibus Incentive Plan
In May 2019, our shareholders approved the 2019 Omnibus Incentive Plan (the “2019 Plan”), which provides equity-based and cash-based performance-related incentives to key employees, non-employee directors and other service providers. The intent of the 2019 Plan is to encourage and provide for the acquisition of an ownership interest in Argo Group, enabling us to attract and retain qualified and competent persons to serve as members of our management team and Board of Directors. The 2019 Plan authorizes 1,885,000 common shares to be granted as equity-based awards. No further grants will be made under any prior plan; however, any awards under a prior plan that are outstanding as of the effective date shall remain subject to the terms and conditions of, and be governed by, such prior plan.
Awards granted under the 2019 Plan may be in the form of stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance awards, other stock-based awards or other cash-based awards. Awards may be granted either alone, in addition to or in tandem with other awards authorized under the 2019 Plan. Awards that are settled in stock will count as one share for the purposes of reducing the share reserve under the 2019 Plan. Shares issued under this plan may be shares that are authorized and unissued or shares that we have reacquired, including shares purchased on the open market.
Stock options and stock appreciation rights are required to have an exercise price that is not less than the fair market value on the date of grant. The term of these awards is not to exceed ten years.
Restricted Shares
A summary of non-vested restricted share activity as of June 30, 2021 and changes during the six months then ended is as follows:
SharesWeighted-Average
Grant Date
Fair Value
Outstanding at January 1, 2021370,027 $44.22 
Granted159,382 $54.97 
Vested and issued(125,258)$43.40 
Expired or forfeited(65,236)$45.20 
Outstanding at June 30, 2021338,915 $49.39 
The restricted shares vest over one to four years. Expense recognized under this plan for the restricted shares was $1.4 million and $2.9 million for the three and six months ended June 30, 2021, respectively, as compared to $2.1 million and $5.2 million for the three and six months ended June 30, 2020, respectively. Compensation expense for all share-based compensation awards is included in “Underwriting, acquisition and insurance expenses” in the accompanying Consolidated Statements of Income (Loss). As of June 30, 2021, there was $13.8 million of total unrecognized compensation cost related to restricted share compensation arrangements granted by Argo Group.
Performance Shares
We have issued to certain key employees non-vested restricted stock awards whose vesting is subject to the achievement of certain performance measures. The non-vested performance share awards vest over three to four years. Market-based performance awards are valued using the Monte Carlo simulation. All other non-vested performance share awards are valued based on the fair market value as of the grant date. Vesting of the awards is subject to the achievement of defined performance measures and the number of shares vested may be adjusted based on the achievement of certain targets. We evaluate the likelihood of the employee achieving the performance condition and include this estimate in the determination of the forfeiture factor for these grants.
A summary of non-vested performance share activity as of June 30, 2021 and changes during the six months then ended is as follows:
SharesWeighted-Average
Grant Date
Fair Value
Outstanding at January 1, 2021157,847 $43.10 
Granted100,291 $54.79 
Vested and issued(8,987)$44.49 
Expired or forfeited(17,334)$45.61 
Outstanding at June 30, 2021231,817 $47.91 
Expense recognized under this plan for the performance shares was $0.9 million and $1.6 million for the three and six months ended June 30, 2021, respectively, as compared to $0.6 million and $0.7 million for the three and six months ended June 30, 2020, respectively. As of June 30, 2021, there was $7.3 million of total unrecognized compensation cost related to performance share compensation arrangements granted by Argo Group.
v3.21.2
Underwriting, Acquisition and Insurance Expenses
 6 Months Ended
Jun. 30, 2021
Underwriting, Acquisition and Insurance Expenses [Abstract]  
Underwriting, Acquisition and Insurance Expenses Underwriting, Acquisition and Insurance ExpensesUnderwriting, acquisition and insurance expenses were as follows:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Commissions$71.7 $57.2 $148.2 $122.5 
Other underwriting, acquisition and insurance expenses104.0 98.2 210.6 205.2 
175.7 155.4 358.8 327.7 
Net deferral of policy acquisition costs1.6 4.4 (5.1)0.2 
Total underwriting, acquisition and insurance expenses$177.3 $159.8 $353.7 $327.9 
v3.21.2
Income Taxes
 6 Months Ended
Jun. 30, 2021
Income Tax Disclosure [Abstract]  
Income Taxes Income Taxes
We are incorporated under the laws of Bermuda and, under current Bermuda law, are not obligated to pay any taxes in Bermuda based upon income or capital gains. We have received an undertaking from the Supervisor of Insurance in Bermuda pursuant to the provisions of the Exempted Undertakings Tax Protection Act, 2011, which exempts us from any Bermuda taxes computed on profits, income or any capital asset, gain or appreciation or any tax in the nature of estate, duty or inheritance tax, at least until the year 2035.
We do not consider Argo Group International Holdings, Ltd. to be engaged in a trade or business in the United States or the United Kingdom and, accordingly, do not expect to be subject to direct United States or United Kingdom income taxation.
We have subsidiaries based in the United Kingdom that are subject to the tax laws of that country. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Certain of the United Kingdom subsidiaries are deemed to be engaged in business in the United States, and therefore, are subject to United States corporate tax in respect of a proportion of their United States underwriting business only. Relief is available against the United Kingdom tax liabilities in respect of overseas taxes paid that arise from the underwriting business. Our United Kingdom subsidiaries file separate United Kingdom income tax returns.
We have subsidiaries based in the United States that are subject to United States tax laws. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Our United States subsidiaries generally file a consolidated United States federal income tax return.
We also have operations in Brazil, France, Ireland, Italy, Malta, Spain, and Switzerland, which also are subject to income taxes imposed by the jurisdiction in which they operate. We have operations in Barbados and the United Arab Emirates, which are not subject to income tax under the laws of those countries.
On June 10, 2021, U.K. tax legislation referred to as Finance Act 2021 received Royal Assent and was enacted. The effects of changes in tax laws and tax rates are recognized in the period of enactment. Accordingly, we recorded the impacts of Finance Act 2021 in our June 30, 2021 consolidated financial statements which primarily includes the remeasurement of our deferred tax assets and liabilities for the increased U.K. federal tax rate from 19% to 25% beginning on April 1, 2023. The remeasurement resulted in an increase of net deferred tax assets of $7.4 million.
Our expected income tax provision computed on pre-tax income (loss) at the weighted average tax rate has been calculated as the sum of the pre-tax income (loss) in each jurisdiction multiplied by that jurisdiction’s applicable statutory tax rate. For the three and six months ended June 30, 2021 and 2020, pre-tax income (loss) attributable to our operations and the corresponding operations’ effective tax rates were as follows: 
For the Three Months Ended June 30,
20212020
(in millions)Pre-Tax
Income (Loss)		Effective
Tax
Rate		Pre-Tax
Income (Loss)		Effective
Tax
Rate
Bermuda$2.3 — %$(29.2)— %
United States64.0 21.9 %66.2 23.8 %
United Kingdom9.3 (54.6)%(29.2)15.5 %
Barbados— — %— — %
Belgium— — %0.1 20.0 %
Brazil2.3 — %0.6 — %
United Arab Emirates0.1 — %0.5 — %
Ireland— 
(1)
— %— 
(1)
— %
Italy0.4 — %(1.8)— %
Malta0.3 — %(1.3)— %
Switzerland— 
(1)
— %— 
(1)
1.0 %
Pre-tax income$78.7 11.3 %$5.9 191.5 %
(1)    Pre-tax income (loss) for the respective year was less than $0.1 million.

For the Six Months Ended June 30,
20212020
(in millions)Pre-Tax
Income (Loss)		Effective
Tax
Rate		Pre-Tax
Income (Loss)		Effective
Tax
Rate
Bermuda$7.3 — %$(55.0)— %
United States105.2 19.4 %55.6 23.5 %
United Kingdom(8.9)115.3 %(27.6)10.3 %
Barbados— 
(1)
— %— — %
Belgium— — %0.1 31.0 %
Brazil4.0 — %2.8 — %
United Arab Emirates0.3 — %1.3 — %
Ireland(0.1)— %— 
(1)
— %
Italy1.2 — %1.7 — %
Malta0.9 — %1.3 — %
Switzerland— 
(1)
— %— 
(1)
0.9 %
Pre-tax income (loss)$109.9 9.3 %$(19.8)(52.0)%
(1)    Pre-tax income (loss) for the respective year was less than $0.1 million.
Our effective tax rate may vary significantly from period to period depending on the jurisdiction generating the pre-tax income (loss) and its corresponding statutory tax rate. The geographic distribution of pre-tax income (loss) can fluctuate significantly between periods given the inherit nature of our business.
A reconciliation of the difference between the provision for income taxes and the expected tax provision at the weighted average tax rate is as follows:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Income tax provision at expected rate$16.5 $8.6 22.8 9.4 
Tax effect of:
Nontaxable investment income(0.1)(0.2)(0.3)(0.3)
Foreign exchange adjustments(0.3)1.5 (0.5)(0.6)
Goodwill— 1.0 — 1.0 
Withholding taxes0.1 — (1)0.1 0.1 
Change in uncertain tax position liability0.6 — (1.8)— 
Change in valuation allowance(1.2)— (1)(2.0)— (1)
Impact of change in tax rate related to Finance Act 2021(7.4)— (7.4)— 
     Other 0.7 0.4 (0.6)0.7 
Income tax provision $8.9 $11.3 $10.3 $10.3 
(1) Tax effect of the adjustment for the respective year was less than $0.1 million.
Our gross deferred tax assets are supported by taxes paid in previous periods, reversal of taxable temporary differences and recognition of future taxable income. Management regularly evaluates the recoverability of the deferred tax assets and makes any necessary adjustments to them based upon any changes in management’s expectations of future taxable income. Realization of deferred tax assets is dependent upon our generation of future taxable income sufficient to recover tax benefits that cannot be recovered from taxes paid in the carryback period, generally for our U.S. property and casualty insurers two years for net operating losses and for all our U.S. subsidiaries three years for capital losses. If a company determines that any of its deferred tax assets will not result in future tax benefits, a valuation allowance must be established for the portion of these assets that are not expected to be realized. For the three and six months ended June 30, 2021, the net change in valuation allowance for deferred tax assets was a decrease of $1.2 million and $2.0 million, respectively, relating to the following: Internal Revenue Code Section 382 limited net operating loss carryforwards within the United States, cumulative losses incurred since inception, and valuation allowances acquired through or related to acquisitions. Based upon a review of our available evidence, both positive and negative discussed above, our management concluded that it is more-likely-than-not that the other deferred tax assets will be realized.
For any uncertain tax positions not meeting the “more-likely-than-not” recognition threshold, accounting standards require recognition, measurement and disclosure in a company’s financial statements. For the three and six months ended June 30, 2021, the Company had a net increase (decrease) of uncertain tax positions in the amount of $0.6 million and $(1.8) million, respectively. A net increase (decrease) of interest in the amount of $0.1 million and $(0.4) million has been recorded in the line item “Interest expense” in our Consolidated Statements of (Loss) Income for the three and six months ended June 30, 2021, respectively. A net increase (decrease) of penalty in the amount of $0.0 million and $(0.4) million has been recorded in the line “Underwriting, acquisition and insurance expenses” in our Consolidated Statements of Income (Loss) for the three and six months ended June 30, 2021, respectively.
Our United States subsidiaries are no longer subject to U.S. federal and state income tax examinations by tax authorities for years before 2017. Our United Kingdom subsidiaries are no longer subject to United Kingdom income tax examinations by Her Majesty’s Revenue and Customs for years before 2019.
Numerous foreign jurisdictions in which we operate have provided or proposed income-tax relief in response to the COVID-19 pandemic. The Company does not anticipate any of the recent legislative initiatives to have a material impact on its financial statements and will continue to analyze these initiatives in response to the COVID-19 pandemic.
v3.21.2
Commitments and Contingencies
 6 Months Ended
Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Commitments and ContingenciesArgo Group’s subsidiaries are parties to legal actions incidental to their business. Based on the opinion of legal counsel, management believes that the resolution of these matters will not materially affect our financial condition or results of operations.We have contractual commitments to invest up to $67.9 million related to our limited partnership investments at June 30, 2021, as further disclosed in Note 3, “Investments.” These commitments will be funded as required by the partnership agreements which can be called to be fulfilled at any time, not to exceed twelve years.
v3.21.2
Segment Information
 6 Months Ended
Jun. 30, 2021
Segment Reporting [Abstract]  
Segment Information Segment Information
We are primarily engaged in underwriting property and casualty insurance. We have two ongoing reporting segments: U.S. Operations and International Operations. Additionally, we have a Run-off Lines segment for certain products that we no longer underwrite.
We consider many factors, including the nature of each segment’s insurance and reinsurance products, production sources, distribution strategies and the regulatory environment, in determining how to aggregate reporting segments. Transactions between segments are reported in the segment that initiated the transaction.
In evaluating the operating performance of our segments, we focus on core underwriting and investing results before the consideration of realized gains or losses from investments. Realized investment gains are reported as a component of the Corporate and Other segment, as decisions regarding the acquisition and disposal of securities reside with the corporate investment function and are not under the control of the individual business segments. Identifiable assets by segment are those assets used in the operation of each segment.
Revenue and income (loss) before income taxes for each segment were as follows:
 For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Revenue:
Earned premiums
U.S. Operations$314.5 $301.6 $628.9 $604.1 
International Operations155.7 131.8 307.2 264.1 
Run-off Lines0.1 — 0.3 0.2 
Total earned premiums470.3 433.4 936.4 868.4 
Net investment income
U.S. Operations33.7 0.8 62.5 26.0 
International Operations13.9 0.5 25.9 9.1 
Run-off Lines1.1 0.1 1.9 1.3 
Corporate and Other4.0 — 6.8 0.6 
Total net investment income52.7 1.4 97.1 37.0 
Net realized investment gains (losses) 24.7 17.9 37.8 (18.3)
Total revenue$547.7 $452.7 $1,071.3 $887.1 

For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Income (loss) before income taxes
U.S. Operations$53.6 $31.2 $90.2 $68.1 
International Operations19.5 (27.5)7.7 (39.8)
Run-off Lines(0.1)(1.3)0.5 (0.8)
Total segment income before taxes 73.0 2.4 98.4 27.5 
Corporate and Other(14.6)(10.1)(20.6)(23.8)
Net realized investment and other gains (losses) 24.7 17.9 37.8 (18.3)
Foreign currency exchange losses(4.4)(4.3)(5.7)(5.2)
Total income (loss) before income taxes$78.7 $5.9 $109.9 $(19.8)
The table below presents earned premiums by geographic location for the three and six months ended June 30, 2021 and 2020. For this disclosure, we determine geographic location by the country of domicile of our subsidiaries that underwrite the business and not by the location of insureds or reinsureds from whom the business was generated.
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
United States$314.2 $301.4 $627.0 $601.1 
United Kingdom116.8 75.5 215.8 162.2 
Bermuda10.7 25.3 35.8 46.5 
Malta11.0 18.5 25.0 30.3 
All other jurisdictions17.6 12.7 32.8 28.3 
Total earned premiums$470.3 $433.4 $936.4 $868.4 
The following table represents identifiable assets:
(in millions)June 30, 2021December 31, 2020
U.S. Operations$5,704.0 $6,032.2 
International Operations3,898.4 3,899.4 
Run-off Lines253.0 335.9 
Corporate and Other512.9 198.3 
Total$10,368.3 $10,465.8 
Included in total assets at June 30, 2021 and December 31, 2020 are $602.3 million and $825.9 million, respectively, in assets associated with trade capital providers.
v3.21.2
Subsequent Event
 6 Months Ended
Jun. 30, 2021
Subsequent Events [Abstract]  
Subsequent Event Subsequent Event As previously disclosed in Argo Group’s Annual Report on Form 10-K for the year ended December 31, 2020, during the fourth quarter of 2020, we announced an agreement to sell our Italian operations, ArgoGlobal Assicurazioni S.p.A. to Perfuturo Capital AG, a Swiss Holding Company. Completion of the transaction was subject to regulatory approval. Because such regulatory approval was not received prior to July 31, 2021, the agreement terminated under its own terms.
v3.21.2
Basis of Presentation (Policies)
 6 Months Ended
Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Basis of Presentation Basis of Presentation
The accompanying consolidated financial statements of Argo Group International Holdings, Ltd. and its subsidiaries (“Argo Group,” “Argo,” “we,” “us,” “our” or the “Company”) have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions for Form 10-Q and Article 10 of Regulation S-X. Argo Group is an underwriter of specialty insurance products in the property and casualty market.
The preparation of interim financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. The major estimates reflected in our consolidated financial statements include, but are not limited to, reserves for losses and loss adjustment expenses; reinsurance recoverables, including the reinsurance recoverables allowance for expected credit losses; estimates of written and earned premiums; reinsurance premium receivable; fair value of investments and assessment of potential impairment, including the allowance for credit losses on fixed maturity securities; valuation of goodwill and intangibles and our deferred tax asset valuation allowance. Actual results could materially differ from those estimates. Certain financial information that is normally included in annual financial statements, including certain financial statement footnotes, prepared in accordance with GAAP, is not required for interim reporting purposes and has been condensed or omitted. These statements should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2020, filed with the Securities and Exchange Commission ("SEC") on March 15, 2021.
The interim financial information as of, and for, the three and six months ended, June 30, 2021 and 2020 is unaudited. However, in the opinion of management, the interim information includes all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results presented for the interim periods. The operating results for the interim periods are not necessarily indicative of the results to be expected for the full year. All significant intercompany amounts have been eliminated in consolidation.
Reclassification Certain reclassifications have been made to financial information presented for prior years to conform to the current year’s presentation.
v3.21.2
Investments (Tables)
 6 Months Ended
Jun. 30, 2021
Investments, Debt and Equity Securities [Abstract]  
Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value of Investments
The amortized cost, gross unrealized gains, gross unrealized losses, allowance for credit losses, and fair value of fixed maturity investments were as follows:
June 30, 2021
(in millions)Amortized
Cost		Gross
Unrealized
Gains		Gross
Unrealized
Losses		Allowance for Credit LossesFair
Value
Fixed maturities
U.S. Governments$350.7 $8.6 $1.5 $— $357.8 
Foreign Governments209.9 4.1 1.1 0.2 212.7 
Obligations of states and political subdivisions185.5 7.5 0.5 — 192.5 
Corporate bonds1,956.0 55.4 11.0 6.2 1,994.2 
Commercial mortgage-backed securities342.2 10.6 1.7 — 351.1 
Residential mortgage-backed securities510.8 12.0 3.6 — 519.2 
Asset-backed securities121.1 2.6 0.4 — 123.3 
Collateralized loan obligations305.0 2.6 0.7 — 306.9 
Total fixed maturities$3,981.2 $103.4 $20.5 $6.4 $4,057.7 
December 31, 2020
(in millions)Amortized
Cost		Gross
Unrealized
Gains		Gross
Unrealized
Losses		Allowance for Credit LossesFair
Value
Fixed maturities
U.S. Governments$385.4 $14.7 $0.3 $— $399.8 
Foreign Governments284.1 11.6 0.7 0.2 294.8 
Obligations of states and political subdivisions163.1 7.7 0.3 0.1 170.4 
Corporate bonds1,925.9 75.3 13.3 6.1 1,981.8 
Commercial mortgage-backed securities324.8 15.2 0.3 — 339.7 
Residential mortgage-backed securities491.4 17.4 0.6 — 508.2 
Asset-backed securities120.5 2.9 0.4 0.2 122.8 
Collateralized loan obligations285.9 4.9 1.2 — 289.6 
Total fixed maturities$3,981.1 $149.7 $17.1 $6.6 $4,107.1 
Schedule of Amortized Cost and Fair Values of Fixed Maturity Investments, by Contractual Maturity The amortized cost and fair values of fixed maturity investments as of June 30, 2021, by contractual maturity, were as follows:
(in millions)Amortized
Cost		Fair
Value
Due in one year or less$284.5 $288.7 
Due after one year through five years1,596.3 1,630.2 
Due after five years through ten years714.6 729.9 
Due after ten years106.7 108.4 
Structured securities1,279.1 1,300.5 
Total$3,981.2 $4,057.7 
Schedule of Carrying Value and Unfunded Investment Commitments of Other Invested Assets Portfolio
Details regarding the carrying value and unfunded investment commitments of other investments as of June 30, 2021 and December 31, 2020 were as follows:
June 30, 2021
(in millions)Carrying
Value		Unfunded
Commitments
Investment Type
Hedge funds$99.4 $— 
Private equity243.1 67.9 
Overseas deposits65.1 — 
Other4.7 — 
Total other investments$412.3 $67.9 
December 31, 2020
(in millions)Carrying
Value		Unfunded
Commitments
Investment Type
Hedge funds$111.2 $— 
Private equity211.4 80.0 
Overseas deposits102.1 — 
Other4.7 — 
Total other investments$429.4 $80.0 
Schedule of Aging of Unrealized Losses on Company's Investments in Fixed Maturities, Equity Securities and Other Investments An aging of unrealized losses on our investments in fixed maturities is presented below:
June 30, 2021Less Than One YearOne Year or GreaterTotal
(in millions)Fair
Value		Unrealized
Losses		Fair
Value		Unrealized
Losses		Fair
Value		Unrealized
Losses
Fixed maturities
U.S. Governments$106.6 $1.5 $— $— $106.6 $1.5 
Foreign Governments97.6 0.9 — 0.2 97.6 1.1 
Obligations of states and political subdivisions22.4 0.3 0.4 0.2 22.8 0.5 
Corporate bonds476.9 8.6 26.9 2.4 503.8 11.0 
Commercial mortgage-backed securities76.6 1.5 7.0 0.2 83.6 1.7 
Residential mortgage-backed securities157.6 3.5 5.1 0.1 162.7 3.6 
Asset-backed securities16.4 0.4 3.1 — 19.5 0.4 
Collateralized loan obligations100.3 0.7 2.8 — 103.1 0.7 
Total fixed maturities$1,054.4 $17.4 $45.3 $3.1 $1,099.7 $20.5 
December 31, 2020Less Than One YearOne Year or GreaterTotal
(in millions)Fair
Value		Unrealized
Losses		Fair
Value		Unrealized
Losses		Fair
Value		Unrealized
Losses
Fixed maturities
U.S. Governments$40.6 $0.3 $— $— $40.6 $0.3 
Foreign Governments18.0 0.5 0.1 0.2 18.1 0.7 
Obligations of states and political subdivisions5.2 0.3 — — 5.2 0.3 
Corporate bonds202.5 6.7 17.5 6.6 220.0 13.3 
Commercial mortgage-backed securities21.8 0.3 — — 21.8 0.3 
Residential mortgage-backed securities74.4 0.4 3.0 0.2 77.4 0.6 
Asset-backed securities4.6 0.4 — — 4.6 0.4 
Collateralized loan obligations121.1 0.9 49.1 0.3 170.2 1.2 
Total fixed maturities$488.2 $9.8 $69.7 $7.3 $557.9 $17.1 
Debt Securities, Available-for-sale, Allowance for Credit Loss
The following table presents a roll-forward of the changes in allowance for credit losses on available-for-sale fixed maturities by industry category:
(in millions)Foreign GovernmentsObligations of states and political subdivisionsCorporate bondsAsset backed securitiesTotal
Beginning balance, January 1, 2021$0.2 $0.1 $6.1 $0.2 $6.6 
Securities for which allowance was not previously recorded— — 2.0 — 2.0 
Securities sold during the period— — (0.9)— (0.9)
Additional net increases (decreases) in existing allowance— (0.1)(1.0)(0.2)(1.3)
Ending balance, June 30, 2020$0.2 $— $6.2 $— $6.4 
Schedule of Company's Gross Realized Investment Gains (Losses)
The following table presents our gross realized investment gains (losses):
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Realized gains on fixed maturities and other
Fixed maturities$17.5 $2.5 $23.0 $23.3 
Other investments, including short-terms5.8 11.5 8.0 59.7 
Other assets3.3 32.5 3.3 32.5 
26.6 46.5 34.3 115.5 
Realized losses on fixed maturities and other
Fixed maturities(3.0)(10.5)(4.5)(18.2)
Other investments, including short-terms(8.8)(14.4)(14.5)(46.3)
Other assets(11.5)— (11.5)— 
Credit losses on fixed maturities0.4 (7.8)(0.7)(32.5)
(22.9)(32.7)(31.2)(97.0)
Equity securities
Net realized (losses) on equity securities0.7 (11.0)(1.1)(12.6)
Change in unrealized gains (losses) on equity securities held at the end of the period20.3 15.1 35.8 (24.2)
Net realized gains (losses) on equity securities21.0 4.1 34.7 (36.8)
Net realized investment and other gains (losses) before income taxes24.7 17.9 37.8 (18.3)
Income tax (benefit) provision5.2 6.7 7.9 (1.3)
Net realized investment gains (losses), net of income taxes$19.5 $11.2 $29.9 $(17.0)
Schedule of Changes in Unrealized Appreciation (Depreciation)
Changes in unrealized gains (losses) related to investments are summarized as follows:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Change in unrealized losses
Fixed maturities$18.0 $136.2 $(47.7)$24.4 
Other investments— — — (14.2)
Other and short-term investments0.1 0.2 (0.3)— 
Net unrealized investment gains (losses) before income taxes18.1 136.4 (48.0)10.2 
Income tax provision (benefit)4.0 24.4 (8.6)5.2 
Net unrealized investment gains (losses), net of income taxes$14.1 $112.0 $(39.4)$5.0 
Schedule of Fair Value of Foreign Currency Exchange Forward Contracts
The fair value of our foreign currency exchange forward contracts as of June 30, 2021 and December 31, 2020 was as follows:
(in millions)June 30, 2021December 31, 2020
Operational currency exposure$(1.1)$0.4 
Asset manager investment exposure1.0 (0.2)
Total return strategy— 0.7 
Total$(0.1)$0.9 
Schedule of Realized Gains and Losses of Investment on Foreign Currency Exchange Forward Contracts The following table represents our gross investment realized gains and losses on our foreign currency exchange forward contracts:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Realized gains
Operational currency exposure$3.2 $0.5 $7.1 $5.9 
Asset manager investment exposure0.9 0.2 1.8 1.0 
Total return strategy— 8.2 6.1 33.2 
Gross realized investment gains4.1 8.9 15.0 40.1 
Realized losses
Operational currency exposure(3.5)(3.0)(12.7)(4.7)
Asset manager investment exposure(0.8)(0.6)(0.8)(1.0)
Total return strategy— (8.6)(5.1)(36.6)
Gross realized investment losses(4.3)(12.2)(18.6)(42.3)
Net realized investment (losses) gains on foreign currency exchange forward contracts
$(0.2)$(3.3)$(3.6)$(2.2)
Schedule of Restricted Assets The following table presents our components of restricted assets:
(in millions)June 30, 2021December 31, 2020
Securities on deposit for regulatory and other purposes$214.5 $227.5 
Securities pledged as collateral for letters of credit and other190.6 189.4 
Securities and cash on deposit supporting Lloyd’s business353.0 409.2 
Total restricted investments$758.1 $826.1 
Financial Assets Measured at Fair Value on Recurring Basis
Based on an analysis of the inputs, our financial assets measured at fair value on a recurring basis have been categorized as follows:
Fair Value Measurements at Reporting Date Using
(in millions)June 30,
2021
Level 1 (a)
Level 2 (b)
Level 3 (c)
Fixed maturities
U.S. Governments$357.8 $343.6 $14.2 $— 
Foreign Governments212.7 — 212.7 — 
Obligations of states and political subdivisions192.5 — 192.5 — 
Corporate bonds1,994.2 — 1,990.6 3.6 
Commercial mortgage-backed securities351.1 — 351.1 — 
Residential mortgage-backed securities519.2 — 519.2 — 
Asset-backed securities123.3 — 123.3 — 
Collateralized loan obligations306.9 — 306.9 — 
Total fixed maturities4,057.7 343.6 3,710.5 3.6 
Equity securities185.7 162.0 — 23.7 
Other investments65.6 — 65.6 — 
Short-term investments530.2 518.8 11.3 0.1 
$4,839.2 $1,024.4 $3,787.4 $27.4 
(a)Quoted prices in active markets for identical assets
(b)Significant other observable inputs
(c)Significant unobservable inputs

Fair Value Measurements at Reporting Date Using
(in millions)December 31,
2020
Level 1 (a)
Level 2 (b)
Level 3 (c)
Fixed maturities
U.S. Governments$399.8 $383.5 $16.3 $— 
Foreign Governments294.8 — 294.8 — 
Obligations of states and political subdivisions170.4 — 170.4 — 
Corporate bonds1,981.8 — 1,974.8 7.0 
Commercial mortgage-backed securities339.7 — 339.7 — 
Residential mortgage-backed securities508.2 — 508.2 — 
Asset-backed securities122.8 — 122.8 — 
Collateralized loan obligations289.6 — 289.6 — 
Total fixed maturities4,107.1 383.5 3,716.6 7.0 
Equity securities176.7 159.2 — 17.5 
Other investments102.5 0.4 102.1 — 
Short-term investments542.6 526.5 16.1 — 
$4,928.9 $1,069.6 $3,834.8 $24.5 
(a)Quoted prices in active markets for identical assets
(b)Significant other observable inputs
(c)Significant unobservable inputs
Schedule of Reconciliation of Beginning and Ending Balances for Investments Categorized as Level 3
A reconciliation of the beginning and ending balances for the investments categorized as Level 3 are as follows:
Fair Value Measurements Using Observable Inputs (Level 3)
(in millions)Corporate BondsEquity
Securities		Short Term InvestmentsTotal
Beginning balance, January 1, 2021$7.0 $17.5 $— $24.5 
Transfers into Level 3— — — — 
Transfers out of Level 3— — — — 
Total gains or losses (realized/unrealized):
Included in net income — 6.2 — 6.2 
Included in other comprehensive income0.1 — — 0.1 
Purchases, issuances, sales, and settlements:
Purchases— — 0.1 0.1 
Issuances— — — — 
Sales(3.5)— — (3.5)
Settlements— — — — 
 Ending balance, June 30, 2021$3.6 $23.7 $0.1 $27.4 
Amount of total gains or losses for the year included in net income attributable to the change in unrealized gains or losses relating to assets still held at June 30, 2021$— $— $— $— 
(in millions)Credit FinancialEquity
Securities		Total
Beginning balance, January 1, 2020$7.4 $18.2 $25.6 
Transfers into Level 3— — — 
Transfers out of Level 3— — — 
Total gains or losses (realized/unrealized):
Included in net income— (5.9)(5.9)
Included in other comprehensive loss(0.5)— (0.5)
Purchases, issuances, sales, and settlements:
Purchases0.1 5.2 5.3 
Issuances— — — 
Sales— — — 
Settlements— — — 
 Ending balance, December 31, 2020$7.0 $17.5 $24.5 
Amount of total gains or losses for the year included in net income attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2020$— $— $— 
v3.21.2
Allowance for Credit Losses (Tables)
 6 Months Ended
Jun. 30, 2021
Credit Loss [Abstract]  
Premium Receivable, Allowance for Credit Loss The following table represents the balances of premiums receivable, net of allowance for expected credit losses, at June 30, 2021 and January 1, 2021, and the changes in the allowance for expected credit losses for the six months ended June 30, 2021.
(in millions)Premiums Receivable, Net of Allowance for Estimated Uncollectible PremiumsAllowance for Estimated Uncollectible Premiums
Balance, January 1, 2021$679.8 $9.4 
Current period change for estimated uncollectible premiums(0.1)
Write-offs of uncollectible premiums receivable(0.6)
Foreign exchange adjustments— 
Balance, June 30, 2021$681.7 $8.7 
Reinsurance Recoverable, Allowance for Credit Loss
Reinsurance Recoverables
The following table presents the balances of reinsurance recoverables, net of the allowance for estimated uncollectible reinsurance, at June 30, 2021 and January 1, 2021, and changes in the allowance for estimated uncollectible reinsurance for the six months ended June 30, 2021.
(in millions) Reinsurance Recoverables, Net of Allowance for Estimated Uncollectible ReinsuranceAllowance for Estimated Uncollectible Reinsurance
Balance, January 1, 2021$3,009.0 $4.1 
Current period change for estimated uncollectible reinsurance(0.3)
Write-offs of uncollectible reinsurance recoverables— 
Balance, June 30, 2021$2,859.9 $3.8 
v3.21.2
Reserves for Losses and Loss Adjustment Expenses (Tables)
 6 Months Ended
Jun. 30, 2021
Insurance [Abstract]  
Reserves for Losses and Loss Adjustment Expenses
The following table provides a reconciliation of reserves for losses and loss adjustment expenses (“LAE”):
For the Six Months Ended
June 30,
(in millions)20212020
Net reserves beginning of the year$2,906.1 $2,722.7 
Net AIL reserves acquired— 27.9 
Add:
Losses and LAE incurred during current calendar year, net of reinsurance:
Current accident year579.4 549.6 
Prior accident years(0.2)4.5 
Losses and LAE incurred during calendar year, net of reinsurance579.2 554.1 
Deduct:
Net reserve ceded - reinsurance to close transaction for years of account 2017 and prior (1)
207.8 — 
Losses and LAE payments made during current calendar year, net of reinsurance:
Current accident year59.7 125.3 
Prior accident years376.0 451.5 
Losses and LAE payments made during current calendar year, net of reinsurance:435.7 576.8 
Change in participation interest (2)
12.8 33.0 
Foreign exchange adjustments6.1 (8.5)
Net reserves - end of period2,860.7 2,752.4 
Add:
Reinsurance recoverables on unpaid losses and LAE, end of period2,377.9 2,463.9 
Gross reserves - end of period$5,238.6 $5,216.3 
(1)Amount represents reserves ceded under the reinsurance to close transaction with RiverStone for Lloyd’s years of account 2017 and prior, effective January 1, 2020.
(2)Amount represents the change in reserves due to changing our participation in Syndicates 1200 and 1910.
Impact from (Favorable) Unfavorable Development of Prior Accident Years’ Loss and LAE Reserves on Each Reporting Segment
The impact from the (favorable) unfavorable development of prior accident years’ loss and LAE reserves on each reporting segment is presented below: 
For the Six Months Ended
June 30,
(in millions)20212020
U.S. Operations$(0.9)$2.7 
International Operations(1.9)1.1 
Run-off Lines2.6 0.7 
Total (favorable) unfavorable prior-year development$(0.2)$4.5 
v3.21.2
Disclosures about Fair Value of Financial Instruments (Tables)
 6 Months Ended
Jun. 30, 2021
Fair Value Disclosures [Abstract]  
Summary of Company's Financial Instruments Whose Carrying Amount Did Not Equal Fair Value
A summary of our financial instruments whose carrying value did not equal fair value is shown below:
June 30, 2021December 31, 2020
(in millions)Carrying
Amount		Fair
Value		Carrying
Amount		Fair
Value
Junior subordinated debentures:
Trust preferred debentures$172.7 $174.3 $172.7 $173.6 
Subordinated debentures85.3 92.7 85.1 92.3 
Total junior subordinated debentures258.0 267.0 257.8 265.9 
Senior unsecured fixed rate notes140.2 148.9 140.2 146.7 
Floating rate loan stock60.4 61.0 60.7 61.0 
458.6 476.9 458.7 473.6 
Fair Value, Assets Measured on Recurring and Nonrecurring Basis
Based on an analysis of the inputs, our financial instruments measured at fair value for disclosure purposes have been categorized as follows:
Fair Value Measurements at Reporting Date Using
(in millions)June 30, 2021Level 1 (a)Level 2 (b)Level 3 (c)
Junior subordinated debentures:
Trust preferred debentures$174.3 $— $174.3 $— 
Subordinated debentures92.7 — 92.7 — 
Total junior subordinated debentures267.0 — 267.0 — 
Senior unsecured fixed rate notes148.9 148.9 — — 
Floating rate loan stock61.0 — 61.0 — 
476.9 148.9 328.0 — 
(a)Quoted prices in active markets for identical assets
(b)Significant other observable inputs
(c)Significant unobservable inputs
Fair Value Measurements at Reporting Date Using
(in millions)December 31, 2020Level 1 (a)Level 2 (b)Level 3 (c)
Junior subordinated debentures:
Trust preferred debentures$173.6 $— $173.6 $— 
Subordinated debentures92.3 — 92.3 — 
Total junior subordinated debentures265.9 — 265.9 — 
Senior unsecured fixed rate notes146.7 146.7 — — 
Floating rate loan stock61.0 — 61.0 — 
473.6 146.7 326.9 — 
(a)Quoted prices in active markets for identical assets
(b)Significant other observable inputs
(c)Significant unobservable inputs
v3.21.2
Accumulated Other Comprehensive Income (Loss) (Tables)
 6 Months Ended
Jun. 30, 2021
Equity [Abstract]  
Changes in Accumulated Other Comprehensive (Loss) Income
A summary of changes in accumulated other comprehensive (loss) income, net of taxes (where applicable) by component for the six months ended June 30, 2021 and 2020 is presented below:
(in millions)Foreign Currency Translation AdjustmentsUnrealized
Holding Gains
on Securities		Defined Benefit Pension PlansTotal
Balance, January 1, 2021$(37.9)$105.1 $(8.6)$58.6 
Other comprehensive loss before reclassifications2.5 (22.5)1.5 (18.5)
Amounts reclassified from accumulated other comprehensive loss— (16.9)— (16.9)
Net current-period other comprehensive loss2.5 (39.4)1.5 (35.4)
Balance, June 30, 2021$(35.4)$65.7 $(7.1)$23.2 
(in millions)Foreign Currency Translation Adjustments Unrealized
Holding Gains
on Securities		Defined Benefit Pension PlansTotal
Balance, January 1, 2020$(22.6)$33.5 $(8.1)$2.8 
Other comprehensive income before reclassifications(7.6)24.2 — 16.6 
Amounts reclassified from accumulated other comprehensive loss— (19.2)— (19.2)
Net current-period other comprehensive loss(7.6)5.0 — (2.6)
Cumulative effect of adoption of ASU 2016-13— 5.7 — 5.7 
Balance, June 30, 2020$(30.2)$44.2 $(8.1)$5.9 
Amounts Reclassified from Accumulated Other Comprehensive (Loss) Income The amounts reclassified from accumulated other comprehensive income (loss) shown in the above table have been included in the following captions in our Consolidated Statements of Income (Loss):
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Unrealized gains and losses on securities:
Net realized investment gains$(15.2)$(16.5)$(19.2)$(19.9)
Provision (benefit) for income taxes1.5 2.6 2.3 0.7 
Net of taxes$(13.7)$(13.9)$(16.9)$(19.2)
v3.21.2
Net Income (Loss) Per Common Share (Tables)
 6 Months Ended
Jun. 30, 2021
Earnings Per Share [Abstract]  
Net Income (Loss) Per Common Share on Basic and Diluted Basis The following table presents the calculation of net income (loss) per common share on a basic and diluted basis:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions, except number of shares and per share amounts)2021202020212020
Net income (loss)$69.8 $(5.4)$99.6 $(30.1)
Less: Preferred share dividends2.7 — 5.3 — 
Net income (loss) attributable to common shareholders67.1 (5.4)94.3 (30.1)
Weighted average common shares outstanding - basic34,820,649 34,634,353 34,766,948 34,551,935 
Effect of dilutive securities:
Equity compensation awards192,131 — 216,856 — 
Weighted average common shares outstanding - diluted35,012,780 34,634,353 34,983,804 34,551,935 
Net income (loss) per common share:
Basic$1.93 $(0.16)$2.72 $(0.87)
Diluted$1.92 $(0.16)$2.70 $(0.87)
v3.21.2
Supplemental Cash Flow Information (Tables)
 6 Months Ended
Jun. 30, 2021
Supplemental Cash Flow Elements [Abstract]  
Schedule of Interest Paid and Income Taxes Paid (Recovered) Interest paid and income taxes paid (recovered) were as follows:
For the Six Months Ended
June 30,
(in millions)20212020
Senior unsecured fixed rate notes$4.7 $4.7 
Junior subordinated debentures5.0 6.7 
Other indebtedness1.1 3.4 
Total interest paid$10.8 $14.8 
Income taxes paid8.9 1.6 
Income taxes recovered(0.1)(0.7)
Income taxes paid, net$8.8 $0.9 
v3.21.2
Share-based Compensation (Tables)
 6 Months Ended
Jun. 30, 2021
Share-based Payment Arrangement [Abstract]  
Summary of Restricted Share Activity A summary of non-vested restricted share activity as of June 30, 2021 and changes during the six months then ended is as follows:
SharesWeighted-Average
Grant Date
Fair Value
Outstanding at January 1, 2021370,027 $44.22 
Granted159,382 $54.97 
Vested and issued(125,258)$43.40 
Expired or forfeited(65,236)$45.20 
Outstanding at June 30, 2021338,915 $49.39 
Schedule of Performance Shares A summary of non-vested performance share activity as of June 30, 2021 and changes during the six months then ended is as follows:
SharesWeighted-Average
Grant Date
Fair Value
Outstanding at January 1, 2021157,847 $43.10 
Granted100,291 $54.79 
Vested and issued(8,987)$44.49 
Expired or forfeited(17,334)$45.61 
Outstanding at June 30, 2021231,817 $47.91 
v3.21.2
Underwriting, Acquisition and Insurance Expenses (Tables)
 6 Months Ended
Jun. 30, 2021
Underwriting, Acquisition and Insurance Expenses [Abstract]  
Underwriting, Acquisition and Insurance Expenses Underwriting, acquisition and insurance expenses were as follows:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Commissions$71.7 $57.2 $148.2 $122.5 
Other underwriting, acquisition and insurance expenses104.0 98.2 210.6 205.2 
175.7 155.4 358.8 327.7 
Net deferral of policy acquisition costs1.6 4.4 (5.1)0.2 
Total underwriting, acquisition and insurance expenses$177.3 $159.8 $353.7 $327.9 
v3.21.2
Income Taxes (Tables)
 6 Months Ended
Jun. 30, 2021
Income Tax Disclosure [Abstract]  
Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates For the three and six months ended June 30, 2021 and 2020, pre-tax income (loss) attributable to our operations and the corresponding operations’ effective tax rates were as follows: 
For the Three Months Ended June 30,
20212020
(in millions)Pre-Tax
Income (Loss)		Effective
Tax
Rate		Pre-Tax
Income (Loss)		Effective
Tax
Rate
Bermuda$2.3 — %$(29.2)— %
United States64.0 21.9 %66.2 23.8 %
United Kingdom9.3 (54.6)%(29.2)15.5 %
Barbados— — %— — %
Belgium— — %0.1 20.0 %
Brazil2.3 — %0.6 — %
United Arab Emirates0.1 — %0.5 — %
Ireland— 
(1)
— %— 
(1)
— %
Italy0.4 — %(1.8)— %
Malta0.3 — %(1.3)— %
Switzerland— 
(1)
— %— 
(1)
1.0 %
Pre-tax income$78.7 11.3 %$5.9 191.5 %
(1)    Pre-tax income (loss) for the respective year was less than $0.1 million.

For the Six Months Ended June 30,
20212020
(in millions)Pre-Tax
Income (Loss)		Effective
Tax
Rate		Pre-Tax
Income (Loss)		Effective
Tax
Rate
Bermuda$7.3 — %$(55.0)— %
United States105.2 19.4 %55.6 23.5 %
United Kingdom(8.9)115.3 %(27.6)10.3 %
Barbados— 
(1)
— %— — %
Belgium— — %0.1 31.0 %
Brazil4.0 — %2.8 — %
United Arab Emirates0.3 — %1.3 — %
Ireland(0.1)— %— 
(1)
— %
Italy1.2 — %1.7 — %
Malta0.9 — %1.3 — %
Switzerland— 
(1)
— %— 
(1)
0.9 %
Pre-tax income (loss)$109.9 9.3 %$(19.8)(52.0)%
(1)    Pre-tax income (loss) for the respective year was less than $0.1 million.
Reconciliation of Difference Between Provision for Income Taxes and Expected Tax Provision at Weighted Average Tax Rate
A reconciliation of the difference between the provision for income taxes and the expected tax provision at the weighted average tax rate is as follows:
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Income tax provision at expected rate$16.5 $8.6 22.8 9.4 
Tax effect of:
Nontaxable investment income(0.1)(0.2)(0.3)(0.3)
Foreign exchange adjustments(0.3)1.5 (0.5)(0.6)
Goodwill— 1.0 — 1.0 
Withholding taxes0.1 — (1)0.1 0.1 
Change in uncertain tax position liability0.6 — (1.8)— 
Change in valuation allowance(1.2)— (1)(2.0)— (1)
Impact of change in tax rate related to Finance Act 2021(7.4)— (7.4)— 
     Other 0.7 0.4 (0.6)0.7 
Income tax provision $8.9 $11.3 $10.3 $10.3 
(1) Tax effect of the adjustment for the respective year was less than $0.1 million.
v3.21.2
Segment Information (Tables)
 6 Months Ended
Jun. 30, 2021
Segment Reporting [Abstract]  
Revenue and Income (Loss) Before Income Taxes for Each Segment
Revenue and income (loss) before income taxes for each segment were as follows:
 For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Revenue:
Earned premiums
U.S. Operations$314.5 $301.6 $628.9 $604.1 
International Operations155.7 131.8 307.2 264.1 
Run-off Lines0.1 — 0.3 0.2 
Total earned premiums470.3 433.4 936.4 868.4 
Net investment income
U.S. Operations33.7 0.8 62.5 26.0 
International Operations13.9 0.5 25.9 9.1 
Run-off Lines1.1 0.1 1.9 1.3 
Corporate and Other4.0 — 6.8 0.6 
Total net investment income52.7 1.4 97.1 37.0 
Net realized investment gains (losses) 24.7 17.9 37.8 (18.3)
Total revenue$547.7 $452.7 $1,071.3 $887.1 

For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
Income (loss) before income taxes
U.S. Operations$53.6 $31.2 $90.2 $68.1 
International Operations19.5 (27.5)7.7 (39.8)
Run-off Lines(0.1)(1.3)0.5 (0.8)
Total segment income before taxes 73.0 2.4 98.4 27.5 
Corporate and Other(14.6)(10.1)(20.6)(23.8)
Net realized investment and other gains (losses) 24.7 17.9 37.8 (18.3)
Foreign currency exchange losses(4.4)(4.3)(5.7)(5.2)
Total income (loss) before income taxes$78.7 $5.9 $109.9 $(19.8)
Schedule of Earned Premiums by Geographic Location The table below presents earned premiums by geographic location for the three and six months ended June 30, 2021 and 2020. For this disclosure, we determine geographic location by the country of domicile of our subsidiaries that underwrite the business and not by the location of insureds or reinsureds from whom the business was generated.
For the Three Months Ended
June 30,		For the Six Months Ended
June 30,
(in millions)2021202020212020
United States$314.2 $301.4 $627.0 $601.1 
United Kingdom116.8 75.5 215.8 162.2 
Bermuda10.7 25.3 35.8 46.5 
Malta11.0 18.5 25.0 30.3 
All other jurisdictions17.6 12.7 32.8 28.3 
Total earned premiums$470.3 $433.4 $936.4 $868.4 
Identifiable Assets The following table represents identifiable assets:
(in millions)June 30, 2021December 31, 2020
U.S. Operations$5,704.0 $6,032.2 
International Operations3,898.4 3,899.4 
Run-off Lines253.0 335.9 
Corporate and Other512.9 198.3 
Total$10,368.3 $10,465.8 
v3.21.2
Basis of Presentation - Sale of Business Unit (Details) - Disposal Group, Disposed of by Sale, Not Discontinued Operations - Trident
$ in Millions
 3 Months Ended
Jun. 30, 2021
USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]  
Gain (loss) on disposal, reduction in the original gain on sale $ 16.5
Gain on disposal $ 5.0
v3.21.2
Investments - Additional Information (Detail)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
USD ($)
security
Jun. 30, 2020
USD ($)
Jun. 30, 2021
USD ($)
security
Jun. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
Investments, Debt and Equity Securities [Abstract]          
Fair value of investments, assets managed on behalf of the trade capital providers | $ $ 93.0   $ 93.0   $ 140.3
Number of securities in an unrealized loss position, total | security 5,244   5,244    
Number of securities in an unrealized loss position for less than one year | security 477   477    
Number of securities in an unrealized loss position for a period of one year or greater | security 78   78    
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]          
Credit losses on fixed maturities | $ $ (0.4) $ 7.8 $ 0.7 $ 32.5  
Gain (Loss) on Investments          
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]          
Credit losses on fixed maturities | $ $ (0.4) $ 7.8 $ 0.7 $ 32.5  
v3.21.2
Investments - Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value of Investments (Detail) - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Fixed maturities    
Amortized Cost $ 3,981.2 $ 3,981.1
Allowance for Credit Losses 6.4 6.6
Fair Value 4,057.7 4,107.1
Fixed maturities    
Fixed maturities    
Amortized Cost 3,981.2 3,981.1
Gross Unrealized Gains 103.4 149.7
Gross Unrealized Losses 20.5 17.1
Allowance for Credit Losses 6.4 6.6
Fair Value 4,057.7 4,107.1
Fixed maturities | U.S. Governments    
Fixed maturities    
Amortized Cost 350.7 385.4
Gross Unrealized Gains 8.6 14.7
Gross Unrealized Losses 1.5 0.3
Allowance for Credit Losses 0.0 0.0
Fair Value 357.8 399.8
Fixed maturities | Foreign Governments    
Fixed maturities    
Amortized Cost 209.9 284.1
Gross Unrealized Gains 4.1 11.6
Gross Unrealized Losses 1.1 0.7
Allowance for Credit Losses 0.2 0.2
Fair Value 212.7 294.8
Fixed maturities | Obligations of states and political subdivisions    
Fixed maturities    
Amortized Cost 185.5 163.1
Gross Unrealized Gains 7.5 7.7
Gross Unrealized Losses 0.5 0.3
Allowance for Credit Losses 0.0 0.1
Fair Value 192.5 170.4
Fixed maturities | Corporate bonds    
Fixed maturities    
Amortized Cost 1,956.0 1,925.9
Gross Unrealized Gains 55.4 75.3
Gross Unrealized Losses 11.0 13.3
Allowance for Credit Losses 6.2 6.1
Fair Value 1,994.2 1,981.8
Fixed maturities | Commercial mortgage-backed securities    
Fixed maturities    
Amortized Cost 342.2 324.8
Gross Unrealized Gains 10.6 15.2
Gross Unrealized Losses 1.7 0.3
Allowance for Credit Losses 0.0 0.0
Fair Value 351.1 339.7
Fixed maturities | Residential mortgage-backed securities    
Fixed maturities    
Amortized Cost 510.8 491.4
Gross Unrealized Gains 12.0 17.4
Gross Unrealized Losses 3.6 0.6
Allowance for Credit Losses 0.0 0.0
Fair Value 519.2 508.2
Fixed maturities | Asset-backed securities    
Fixed maturities    
Amortized Cost 121.1 120.5
Gross Unrealized Gains 2.6 2.9
Gross Unrealized Losses 0.4 0.4
Allowance for Credit Losses 0.0 0.2
Fair Value 123.3 122.8
Fixed maturities | Collateralized loan obligations    
Fixed maturities    
Amortized Cost 305.0 285.9
Gross Unrealized Gains 2.6 4.9
Gross Unrealized Losses 0.7 1.2
Allowance for Credit Losses 0.0 0.0
Fair Value $ 306.9 $ 289.6
v3.21.2
Investments - Schedule of Amortized Cost and Fair Values of Fixed Maturity Investments, by Contractual Maturity (Detail)
$ in Millions
Jun. 30, 2021
USD ($)
Amortized Cost  
Due in one year or less $ 284.5
Due after one year through five years 1,596.3
Due after five years through ten years 714.6
Due after ten years 106.7
Structured securities 1,279.1
Total 3,981.2
Fair Value  
Due in one year or less 288.7
Due after one year through five years 1,630.2
Due after five years through ten years 729.9
Due after ten years 108.4
Structured securities 1,300.5
Total $ 4,057.7
v3.21.2
Investments - Schedule of Carrying Value and Unfunded Investment Commitments of Other Invested Assets Portfolio (Detail) - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Schedule of Investments [Line Items]    
Carrying Value $ 5,185.9 $ 5,255.8
Hedge funds    
Schedule of Investments [Line Items]    
Carrying Value 99.4 111.2
Unfunded Commitments 0.0 0.0
Private equity    
Schedule of Investments [Line Items]    
Carrying Value 243.1 211.4
Unfunded Commitments 67.9 80.0
Overseas deposits    
Schedule of Investments [Line Items]    
Carrying Value 65.1 102.1
Unfunded Commitments 0.0 0.0
Other    
Schedule of Investments [Line Items]    
Carrying Value 4.7 4.7
Unfunded Commitments 0.0 0.0
Other Investments    
Schedule of Investments [Line Items]    
Carrying Value 412.3 429.4
Unfunded Commitments $ 67.9 $ 80.0
v3.21.2
Investments - Schedule of Aging of Unrealized Losses on Company's Investments in Fixed Maturities, Equity Securities and Other Investments (Detail) - Fixed maturities - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Schedule of Investments [Line Items]    
Fair Value, Less Than One Year $ 1,054.4 $ 488.2
Unrealized Losses, Less Than One Year 17.4 9.8
Fair Value, One Year or Greater 45.3 69.7
Unrealized Losses, One Year or Greater 3.1 7.3
Fair Value, Total 1,099.7 557.9
Unrealized Losses, Total 20.5 17.1
U.S. Governments    
Schedule of Investments [Line Items]    
Fair Value, Less Than One Year 106.6 40.6
Unrealized Losses, Less Than One Year 1.5 0.3
Fair Value, One Year or Greater 0.0 0.0
Unrealized Losses, One Year or Greater 0.0 0.0
Fair Value, Total 106.6 40.6
Unrealized Losses, Total 1.5 0.3
Foreign Governments    
Schedule of Investments [Line Items]    
Fair Value, Less Than One Year 97.6 18.0
Unrealized Losses, Less Than One Year 0.9 0.5
Fair Value, One Year or Greater 0.0 0.1
Unrealized Losses, One Year or Greater 0.2 0.2
Fair Value, Total 97.6 18.1
Unrealized Losses, Total 1.1 0.7
Obligations of states and political subdivisions    
Schedule of Investments [Line Items]    
Fair Value, Less Than One Year 22.4 5.2
Unrealized Losses, Less Than One Year 0.3 0.3
Fair Value, One Year or Greater 0.4 0.0
Unrealized Losses, One Year or Greater 0.2 0.0
Fair Value, Total 22.8 5.2
Unrealized Losses, Total 0.5 0.3
Corporate bonds    
Schedule of Investments [Line Items]    
Fair Value, Less Than One Year 476.9 202.5
Unrealized Losses, Less Than One Year 8.6 6.7
Fair Value, One Year or Greater 26.9 17.5
Unrealized Losses, One Year or Greater 2.4 6.6
Fair Value, Total 503.8 220.0
Unrealized Losses, Total 11.0 13.3
Commercial mortgage-backed securities    
Schedule of Investments [Line Items]    
Fair Value, Less Than One Year 76.6 21.8
Unrealized Losses, Less Than One Year 1.5 0.3
Fair Value, One Year or Greater 7.0 0.0
Unrealized Losses, One Year or Greater 0.2 0.0
Fair Value, Total 83.6 21.8
Unrealized Losses, Total 1.7 0.3
Residential mortgage-backed securities    
Schedule of Investments [Line Items]    
Fair Value, Less Than One Year 157.6 74.4
Unrealized Losses, Less Than One Year 3.5 0.4
Fair Value, One Year or Greater 5.1 3.0
Unrealized Losses, One Year or Greater 0.1 0.2
Fair Value, Total 162.7 77.4
Unrealized Losses, Total 3.6 0.6
Asset-backed securities    
Schedule of Investments [Line Items]    
Fair Value, Less Than One Year 16.4 4.6
Unrealized Losses, Less Than One Year 0.4 0.4
Fair Value, One Year or Greater 3.1 0.0
Unrealized Losses, One Year or Greater 0.0 0.0
Fair Value, Total 19.5 4.6
Unrealized Losses, Total 0.4 0.4
Collateralized loan obligations    
Schedule of Investments [Line Items]    
Fair Value, Less Than One Year 100.3 121.1
Unrealized Losses, Less Than One Year 0.7 0.9
Fair Value, One Year or Greater 2.8 49.1
Unrealized Losses, One Year or Greater 0.0 0.3
Fair Value, Total 103.1 170.2
Unrealized Losses, Total $ 0.7 $ 1.2
v3.21.2
Investments - Allowance for Credit Losses (Detail)
$ in Millions
 6 Months Ended
Jun. 30, 2021
USD ($)
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]  
Beginning balance, January 1, 2021 $ 6.6
Securities for which allowance was not previously recorded 2.0
Securities sold during the period (0.9)
Additional net increases (decreases) in existing allowance (1.3)
Ending balance, June 30, 2020 6.4
Foreign Governments  
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]  
Beginning balance, January 1, 2021 0.2
Securities for which allowance was not previously recorded 0.0
Securities sold during the period 0.0
Additional net increases (decreases) in existing allowance 0.0
Ending balance, June 30, 2020 0.2
Obligations of states and political subdivisions  
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]  
Beginning balance, January 1, 2021 0.1
Securities for which allowance was not previously recorded 0.0
Securities sold during the period 0.0
Additional net increases (decreases) in existing allowance (0.1)
Ending balance, June 30, 2020 0.0
Corporate bonds  
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]  
Beginning balance, January 1, 2021 6.1
Securities for which allowance was not previously recorded 2.0
Securities sold during the period (0.9)
Additional net increases (decreases) in existing allowance (1.0)
Ending balance, June 30, 2020 6.2
Asset-backed securities  
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]  
Beginning balance, January 1, 2021 0.2
Securities for which allowance was not previously recorded 0.0
Securities sold during the period 0.0
Additional net increases (decreases) in existing allowance (0.2)
Ending balance, June 30, 2020 $ 0.0
v3.21.2
Investments - Schedule of Company's Gross Realized Investment Gains (Losses) (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Schedule of Investments [Line Items]        
Realized gains on fixed maturities and other $ 26.6 $ 46.5 $ 34.3 $ 115.5
Realized losses on fixed maturities and other (22.9) (32.7) (31.2) (97.0)
Credit gains (losses) on fixed maturity securities 0.4 (7.8) (0.7) (32.5)
Net realized (losses) on equity securities 0.7 (11.0) (1.1) (12.6)
Change in unrealized gains (losses) on equity securities held at the end of the period 20.3 15.1 35.8 (24.2)
Net realized gains (losses) on equity securities 21.0 4.1 34.7 (36.8)
Net realized investment and other gains (losses) before income taxes 24.7 17.9 37.8 (18.3)
Income tax (benefit) provision 5.2 6.7 7.9 (1.3)
Net realized investment gains (losses), net of income taxes 19.5 11.2 29.9 (17.0)
Fixed maturities        
Schedule of Investments [Line Items]        
Realized gains on fixed maturities and other 17.5 2.5 23.0 23.3
Realized losses on fixed maturities and other (3.0) (10.5) (4.5) (18.2)
Other investments        
Schedule of Investments [Line Items]        
Realized gains on fixed maturities and other 5.8 11.5 8.0 59.7
Realized losses on fixed maturities and other (8.8) (14.4) (14.5) (46.3)
Other assets        
Schedule of Investments [Line Items]        
Realized gains on fixed maturities and other 3.3 32.5 3.3 32.5
Realized losses on fixed maturities and other (11.5) 0.0 (11.5) 0.0
Credit losses on fixed maturities        
Schedule of Investments [Line Items]        
Credit gains (losses) on fixed maturity securities $ 0.4 $ (7.8) $ (0.7) $ (32.5)
v3.21.2
Investments - Schedule of Changes in Unrealized Appreciation (Depreciation) (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Schedule of Investments [Line Items]        
Net unrealized investment gains (losses) before income taxes $ 18.1 $ 136.4 $ (48.0) $ 10.2
Income tax provision (benefit) 4.0 24.4 (8.6) 5.2
Net unrealized investment gains (losses), net of income taxes 14.1 112.0 (39.4) 5.0
Fixed maturities        
Schedule of Investments [Line Items]        
Net unrealized investment gains (losses) before income taxes 18.0 136.2 (47.7) 24.4
Other investments        
Schedule of Investments [Line Items]        
Net unrealized investment gains (losses) before income taxes 0.0 0.0 0.0 (14.2)
Other and short-term investments        
Schedule of Investments [Line Items]        
Net unrealized investment gains (losses) before income taxes $ 0.1 $ 0.2 $ (0.3) $ 0.0
v3.21.2
Investments - Schedule of Fair Value of Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Schedule of Investments [Line Items]    
Foreign currency exchange, fair value $ (0.1) $ 0.9
Operational currency exposure    
Schedule of Investments [Line Items]    
Foreign currency exchange, fair value (1.1) 0.4
Asset manager investment exposure    
Schedule of Investments [Line Items]    
Foreign currency exchange, fair value 1.0 (0.2)
Total return strategy    
Schedule of Investments [Line Items]    
Foreign currency exchange, fair value $ 0.0 $ 0.7
v3.21.2
Investments - Schedule of Realized Gains and Losses of Investment on Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Schedule of Investments [Line Items]        
Gross realized investment gains $ 4.1 $ 8.9 $ 15.0 $ 40.1
Gross realized investment losses (4.3) (12.2) (18.6) (42.3)
Net realized investment (losses) gains on foreign currency exchange forward contracts (0.2) (3.3) (3.6) (2.2)
Operational currency exposure        
Schedule of Investments [Line Items]        
Gross realized investment gains 3.2 0.5 7.1 5.9
Gross realized investment losses (3.5) (3.0) (12.7) (4.7)
Asset manager investment exposure        
Schedule of Investments [Line Items]        
Gross realized investment gains 0.9 0.2 1.8 1.0
Gross realized investment losses (0.8) (0.6) (0.8) (1.0)
Total return strategy        
Schedule of Investments [Line Items]        
Gross realized investment gains 0.0 8.2 6.1 33.2
Gross realized investment losses $ 0.0 $ (8.6) $ (5.1) $ (36.6)
v3.21.2
Investments - Components of Restricted Assets (Detail) - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]    
Securities pledged as collateral for letters of credit and other $ 190.6 $ 189.4
Securities and cash on deposit supporting Lloyd’s business 353.0 409.2
Total restricted investments 758.1 826.1
Securities Deposits for Regulatory and Other Purposes    
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]    
Securities on deposit for regulatory and other purposes $ 214.5 $ 227.5
v3.21.2
Investments - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value $ 5,185.9 $ 5,255.8
Fair Value, Recurring    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 4,839.2 4,928.9
Fair Value, Recurring | Fixed maturities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 4,057.7 4,107.1
Fair Value, Recurring | Fixed maturities | Collateralized Loan Obligations    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 306.9 289.6
Fair Value, Recurring | Fixed maturities | U.S. Governments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 357.8 399.8
Fair Value, Recurring | Fixed maturities | Foreign Governments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 212.7 294.8
Fair Value, Recurring | Fixed maturities | Obligations of states and political subdivisions    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 192.5 170.4
Fair Value, Recurring | Fixed maturities | Corporate bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 1,994.2 1,981.8
Fair Value, Recurring | Fixed maturities | Commercial mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 351.1 339.7
Fair Value, Recurring | Fixed maturities | Residential mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 519.2 508.2
Fair Value, Recurring | Fixed maturities | Asset-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 123.3 122.8
Fair Value, Recurring | Equity securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 185.7 176.7
Fair Value, Recurring | Other investments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 65.6 102.5
Fair Value, Recurring | Short-term investments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 530.2 542.6
Fair Value, Recurring | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 1,024.4 1,069.6
Fair Value, Recurring | Level 1 | Fixed maturities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 343.6 383.5
Fair Value, Recurring | Level 1 | Fixed maturities | Collateralized Loan Obligations    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 1 | Fixed maturities | U.S. Governments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 343.6 383.5
Fair Value, Recurring | Level 1 | Fixed maturities | Foreign Governments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 1 | Fixed maturities | Obligations of states and political subdivisions    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 1 | Fixed maturities | Corporate bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 1 | Fixed maturities | Commercial mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 1 | Fixed maturities | Residential mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 1 | Fixed maturities | Asset-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 1 | Equity securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 162.0 159.2
Fair Value, Recurring | Level 1 | Other investments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.4
Fair Value, Recurring | Level 1 | Short-term investments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 518.8 526.5
Fair Value, Recurring | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 3,787.4 3,834.8
Fair Value, Recurring | Level 2 | Fixed maturities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 3,710.5 3,716.6
Fair Value, Recurring | Level 2 | Fixed maturities | Collateralized Loan Obligations    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 306.9 289.6
Fair Value, Recurring | Level 2 | Fixed maturities | U.S. Governments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 14.2 16.3
Fair Value, Recurring | Level 2 | Fixed maturities | Foreign Governments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 212.7 294.8
Fair Value, Recurring | Level 2 | Fixed maturities | Obligations of states and political subdivisions    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 192.5 170.4
Fair Value, Recurring | Level 2 | Fixed maturities | Corporate bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 1,990.6 1,974.8
Fair Value, Recurring | Level 2 | Fixed maturities | Commercial mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 351.1 339.7
Fair Value, Recurring | Level 2 | Fixed maturities | Residential mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 519.2 508.2
Fair Value, Recurring | Level 2 | Fixed maturities | Asset-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 123.3 122.8
Fair Value, Recurring | Level 2 | Equity securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 2 | Other investments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 65.6 102.1
Fair Value, Recurring | Level 2 | Short-term investments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 11.3 16.1
Fair Value, Recurring | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 27.4 24.5
Fair Value, Recurring | Level 3 | Fixed maturities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 3.6 7.0
Fair Value, Recurring | Level 3 | Fixed maturities | Collateralized Loan Obligations    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 3 | Fixed maturities | U.S. Governments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 3 | Fixed maturities | Foreign Governments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 3 | Fixed maturities | Obligations of states and political subdivisions    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 3 | Fixed maturities | Corporate bonds    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 3.6 7.0
Fair Value, Recurring | Level 3 | Fixed maturities | Commercial mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 3 | Fixed maturities | Residential mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 3 | Fixed maturities | Asset-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 3 | Equity securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 23.7 17.5
Fair Value, Recurring | Level 3 | Other investments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value 0.0 0.0
Fair Value, Recurring | Level 3 | Short-term investments    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value $ 0.1 $ 0.0
v3.21.2
Investments - Schedule of Reconciliation of Beginning and Ending Balances for Investments Categorized as Level 3 (Detail) - USD ($)
$ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2021
Dec. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance $ 24.5 $ 25.6
Transfers into Level 3 0.0 0.0
Transfers out of Level 3 0.0 0.0
Included in net income 6.2 (5.9)
Included in other comprehensive income 0.1 (0.5)
Purchases 0.1 5.3
Issuances 0.0 0.0
Sales (3.5) 0.0
Settlements 0.0 0.0
Ending balance 27.4 24.5
Amount of total gains or losses for the year included in net income attributable to the change in unrealized gains or losses relating to assets held 0.0 0.0
Corporate Bonds    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 7.0 7.4
Transfers into Level 3 0.0 0.0
Transfers out of Level 3 0.0 0.0
Included in net income 0.0 0.0
Included in other comprehensive income 0.1 (0.5)
Purchases 0.0 0.1
Issuances 0.0 0.0
Sales (3.5) 0.0
Settlements 0.0 0.0
Ending balance 3.6 7.0
Amount of total gains or losses for the year included in net income attributable to the change in unrealized gains or losses relating to assets held 0.0 0.0
Equity securities    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 17.5 18.2
Transfers into Level 3 0.0 0.0
Transfers out of Level 3 0.0 0.0
Included in net income 6.2 (5.9)
Included in other comprehensive income 0.0 0.0
Purchases 0.0 5.2
Issuances 0.0 0.0
Sales 0.0 0.0
Settlements 0.0 0.0
Ending balance 23.7 17.5
Amount of total gains or losses for the year included in net income attributable to the change in unrealized gains or losses relating to assets held 0.0 0.0
Short-term investments    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 0.0  
Transfers into Level 3 0.0  
Transfers out of Level 3 0.0  
Included in net income 0.0  
Included in other comprehensive income 0.0  
Purchases 0.1  
Issuances 0.0  
Sales 0.0  
Settlements 0.0  
Ending balance 0.1 $ 0.0
Amount of total gains or losses for the year included in net income attributable to the change in unrealized gains or losses relating to assets held $ 0.0  
v3.21.2
Allowance for Credit Losses - Premiums Receivable (Details) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2021
Dec. 31, 2020
Credit Loss [Abstract]    
Premiums receivable $ 681.7 $ 679.8
Premium Receivable, Allowance for Credit Loss [Roll Forward]    
Balance, January 1, 2021 9.4  
Current period change for estimated uncollectible premiums (0.1)  
Write-offs of uncollectible premiums receivable (0.6)  
Foreign exchange adjustments 0.0  
Balance, June 30, 2021 $ 8.7  
v3.21.2
Allowance for Credit Losses - Reinsurance Recoverables (Details) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2021
Dec. 31, 2020
Credit Loss [Abstract]    
Reinsurance recoverables, net $ 2,859.9 $ 3,009.0
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]    
Balance, January 1, 2021 4.1  
Current period change for estimated uncollectible reinsurance (0.3)  
Write-offs of uncollectible reinsurance recoverables 0.0  
Balance, June 30, 2021 $ 3.8  
v3.21.2
Reserves for Losses and Loss Adjustment Expenses - Reserves for Losses and Loss Adjustment Expenses (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]          
Net reserves beginning of the year     $ 2,906.1 $ 2,722.7  
Net AIL reserves acquired     0.0 27.9  
Losses and LAE incurred during current calendar year, net of reinsurance:          
Current accident year     579.4 549.6  
Prior accident years     (0.2) 4.5  
Losses and LAE incurred during calendar year, net of reinsurance $ 271.6 $ 273.2 579.2 554.1  
Net reserve ceded - reinsurance to close transaction for years of account 2017 and prior     207.8 0.0  
Losses and LAE payments made during current calendar year, net of reinsurance:          
Current accident year     59.7 125.3  
Prior accident years     376.0 451.5  
Losses and LAE payments made during current calendar year, net of reinsurance:     435.7 576.8  
Change in participation interest     12.8 33.0  
Foreign exchange adjustments     6.1 (8.5)  
Net reserves - end of period 2,860.7 2,752.4 2,860.7 2,752.4  
Reinsurance recoverables on unpaid losses and LAE, end of period 2,377.9 2,463.9 2,377.9 2,463.9  
Gross reserves - end of period $ 5,238.6 $ 5,216.3 $ 5,238.6 $ 5,216.3 $ 5,406.0
v3.21.2
Reserves for Losses and Loss Adjustment Expenses - Impact from (Favorable) Unfavorable Development of Prior Accident Years' Loss and LAE Reserves on Each Reporting Segment (Detail) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]    
Total (favorable) unfavorable prior-year development $ (0.2) $ 4.5
U.S. Operations    
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]    
Total (favorable) unfavorable prior-year development (0.9) 2.7
International Operations    
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]    
Total (favorable) unfavorable prior-year development (1.9) 1.1
Run-off Lines    
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]    
Total (favorable) unfavorable prior-year development $ 2.6 $ 0.7
v3.21.2
Disclosures about Fair Value of Financial Instruments - Summary of Company's Financial Instruments Whose Carrying Amount Did Not Equal Fair Value (Detail) - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Carrying Amount    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments $ 458.6 $ 458.7
Fair Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 476.9 473.6
Junior subordinated debentures | Carrying Amount    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 258.0 257.8
Junior subordinated debentures | Fair Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 267.0 265.9
Junior subordinated debentures | Trust preferred debentures | Carrying Amount    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 172.7 172.7
Junior subordinated debentures | Trust preferred debentures | Fair Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 174.3 173.6
Junior subordinated debentures | Subordinated debentures | Carrying Amount    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 85.3 85.1
Junior subordinated debentures | Subordinated debentures | Fair Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 92.7 92.3
Senior unsecured fixed rate notes | Carrying Amount    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 140.2 140.2
Senior unsecured fixed rate notes | Fair Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 148.9 146.7
Floating rate loan stock | Carrying Amount    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments 60.4 60.7
Floating rate loan stock | Fair Value    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial instruments $ 61.0 $ 61.0
v3.21.2
Disclosures about Fair Value of Financial Instruments - Summary of Fair Values Measured on Recurring Basis (Details) - Fair Value, Recurring - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments $ 476.9 $ 473.6
Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 148.9 146.7
Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 328.0 326.9
Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Junior subordinated debentures    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 267.0 265.9
Junior subordinated debentures | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Junior subordinated debentures | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 267.0 265.9
Junior subordinated debentures | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Junior subordinated debentures | Trust preferred debentures    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 174.3 173.6
Junior subordinated debentures | Trust preferred debentures | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Junior subordinated debentures | Trust preferred debentures | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 174.3 173.6
Junior subordinated debentures | Trust preferred debentures | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Junior subordinated debentures | Subordinated debentures    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 92.7 92.3
Junior subordinated debentures | Subordinated debentures | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Junior subordinated debentures | Subordinated debentures | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 92.7 92.3
Junior subordinated debentures | Subordinated debentures | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Senior unsecured fixed rate notes    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 148.9 146.7
Senior unsecured fixed rate notes | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 148.9 146.7
Senior unsecured fixed rate notes | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Senior unsecured fixed rate notes | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Floating rate loan stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 61.0 61.0
Floating rate loan stock | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 0.0 0.0
Floating rate loan stock | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments 61.0 61.0
Floating rate loan stock | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial instruments $ 0.0 $ 0.0
v3.21.2
Shareholders' Equity (Detail)
 3 Months Ended 6 Months Ended
Jun. 15, 2021
USD ($)
Jun. 04, 2021
USD ($)
May 06, 2021
$ / shares
Jun. 12, 2020
USD ($)
May 07, 2020
$ / shares
Jun. 30, 2021
USD ($)
$ / shares
Jun. 30, 2020
$ / shares
Jun. 30, 2021
USD ($)
$ / shares
shares
Jun. 30, 2020
$ / shares
Feb. 12, 2021
Dec. 31, 2020
$ / shares
Jul. 09, 2020
May 03, 2016
USD ($)
Class of Stock [Line Items]                          
Dividends declared per common share (in dollars per share)     $ 0.31   $ 0.31 $ 0.31 $ 0.31 $ 0.62 $ 0.62        
Payments of dividends | $   $ 11,100,000   $ 10,600,000                  
Preferred shares par value (in dollars per share)           1.00   1.00     $ 1.00    
Liquidation preference (in dollars per share)           $ 25,000   $ 25,000     $ 25,000    
Fractional interest per one preference share                   0.001   0.001  
Depositary shares, dividends per share (in dollars per share)     0.437500                    
Number of shares repurchased (in shares) | shares               0          
Series A Preferred Stock                          
Class of Stock [Line Items]                          
Payments of dividends | $ $ 2,700,000                        
Preferred stock, dividends declared (in dollars per share)     $ 437.500                    
Preferred stock, dividend rate (in percentage)     7.00%                    
Preferred shares par value (in dollars per share)     $ 1.00                    
Liquidation preference (in dollars per share)     $ 25,000                    
2016 Repurchase Authorization                          
Class of Stock [Line Items]                          
Total number of shares authorized for purchase | $                         $ 150,000,000.0
Remaining number of shares available under repurchase authorization | $           $ 53,300,000   $ 53,300,000          
v3.21.2
Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive (Loss) Income (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning Balance $ 1,821.0 $ 1,613.5 $ 1,857.8 $ 1,763.7
Other comprehensive loss before reclassifications     (18.5) 16.6
Amounts reclassified from accumulated other comprehensive loss     (16.9) (19.2)
Net current-period other comprehensive loss     (35.4) (2.6)
Ending Balance 1,897.9 1,707.7 1,897.9 1,707.7
Cumulative Effect, Period of Adoption, Adjustment        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Ending Balance   (2.2)   (2.2)
Foreign Currency Translation Adjustments        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning Balance     (37.9) (22.6)
Other comprehensive loss before reclassifications     2.5 (7.6)
Amounts reclassified from accumulated other comprehensive loss     0.0 0.0
Net current-period other comprehensive loss     2.5 (7.6)
Ending Balance (35.4) (30.2) (35.4) (30.2)
Foreign Currency Translation Adjustments | Cumulative Effect, Period of Adoption, Adjustment        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning Balance       0.0
Unrealized Holding Gains on Securities        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning Balance     105.1 33.5
Other comprehensive loss before reclassifications     (22.5) 24.2
Amounts reclassified from accumulated other comprehensive loss (13.7) (13.9) (16.9) (19.2)
Net current-period other comprehensive loss     (39.4) 5.0
Ending Balance 65.7 44.2 65.7 44.2
Unrealized Holding Gains on Securities | Cumulative Effect, Period of Adoption, Adjustment        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning Balance       5.7
Defined Benefit Pension Plans        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning Balance     (8.6) (8.1)
Other comprehensive loss before reclassifications     1.5 0.0
Amounts reclassified from accumulated other comprehensive loss     0.0 0.0
Net current-period other comprehensive loss     1.5 0.0
Ending Balance (7.1) (8.1) (7.1) (8.1)
Defined Benefit Pension Plans | Cumulative Effect, Period of Adoption, Adjustment        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning Balance       0.0
Accumulated Other Comprehensive Income (Loss)        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning Balance 4.2 (101.9) 58.6 2.8
Ending Balance $ 23.2 5.9 $ 23.2 5.9
Accumulated Other Comprehensive Income (Loss) | Cumulative Effect, Period of Adoption, Adjustment        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning Balance       5.7
Ending Balance   $ 5.7   $ 5.7
v3.21.2
Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified from Accumulated Other Comprehensive (Loss) Income (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Unrealized gains and losses on securities:        
Net of taxes     $ (16.9) $ (19.2)
Unrealized Gains and Losses on Securities        
Unrealized gains and losses on securities:        
Net realized investment gains $ (15.2) $ (16.5) (19.2) (19.9)
Provision (benefit) for income taxes 1.5 2.6 2.3 0.7
Net of taxes $ (13.7) $ (13.9) $ (16.9) $ (19.2)
v3.21.2
Net Income (Loss) Per Common Share - Net Income (Loss) Per Common Share on Basic and Diluted Basis (Detail) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Earnings Per Share [Abstract]        
Net income (loss) $ 69.8 $ (5.4) $ 99.6 $ (30.1)
Less: Preferred share dividends 2.7 0.0 5.3 0.0
Net income (loss) attributable to common shareholders 67.1 (5.4) 94.3 (30.1)
Net income (loss) attributable to common shareholders $ 67.1 $ (5.4) $ 94.3 $ (30.1)
Weighted average common shares outstanding - basic (in shares) 34,820,649 34,634,353 34,766,948 34,551,935
Effect of dilutive securities:        
Equity compensation awards (in shares) 192,131 0 216,856 0
Weighted average common shares outstanding - diluted (in shares) 35,012,780 34,634,353 34,983,804 34,551,935
Net income (loss) per common share:        
Basic (in dollars per share) $ 1.93 $ (0.16) $ 2.72 $ (0.87)
Diluted (in dollars per share) $ 1.92 $ (0.16) $ 2.70 $ (0.87)
v3.21.2
Net Income (Loss) Per Common Share - Additional Information (Detail) - shares
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2021
Dec. 31, 2020
Jun. 30, 2020
Earnings Per Share [Abstract]        
Treasury shares (in shares) 11,315,889 11,315,889 11,315,889 11,315,889
Equity compensation awards with anti-dilutive effect (in shares) 36,219 48,272    
v3.21.2
Supplemental Cash Flow Information - Schedule of Interest Paid and Income Taxes Paid (Recovered) (Detail) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Supplemental Cash Flow [Line Items]    
Total interest paid $ 10.8 $ 14.8
Income taxes paid 8.9 1.6
Income taxes recovered (0.1) (0.7)
Income taxes paid, net 8.8 0.9
Senior unsecured fixed rate notes    
Supplemental Cash Flow [Line Items]    
Total interest paid 4.7 4.7
Junior subordinated debentures    
Supplemental Cash Flow [Line Items]    
Total interest paid 5.0 6.7
Other indebtedness    
Supplemental Cash Flow [Line Items]    
Total interest paid $ 1.1 $ 3.4
v3.21.2
Share-based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
 1 Months Ended 3 Months Ended 6 Months Ended
May 31, 2019
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Restricted Stock Units (RSUs)          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based payment arrangement, expense   $ 1.4 $ 2.1 $ 2.9 $ 5.2
Employee service share-based compensation, unrecognized compensation costs on non-vested awards   13.8   $ 13.8  
Restricted Stock Units (RSUs) | Minimum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, award vesting period, years       1 year  
Restricted Stock Units (RSUs) | Maximum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, award vesting period, years       4 years  
Performance Shares          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based payment arrangement, expense   0.9 $ 0.6 $ 1.6 $ 0.7
Employee service share-based compensation, unrecognized compensation costs on non-vested awards   $ 7.3   $ 7.3  
Performance Shares | Minimum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, award vesting period, years       3 years  
Performance Shares | Maximum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, award vesting period, years       4 years  
2019 Plan          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based compensation arrangement by share-based payment award, number of shares authorized (in shares) 1,885,000        
Expiration period 10 years        
v3.21.2
Share-based Compensation - Summary of Restricted Share Activity (Detail) - Restricted Stock Units (RSUs)
 6 Months Ended
Jun. 30, 2021
$ / shares
shares
Shares  
Outstanding, beginning balance (in shares) | shares 370,027
Granted (in shares) | shares 159,382
Vested and issued (in shares) | shares (125,258)
Expired or forfeited (in shares) | shares (65,236)
Outstanding, ending balance (in shares) | shares 338,915
Weighted-Average Grant Date Fair Value  
Outstanding, beginning balance (in dollars per share) | $ / shares $ 44.22
Granted (in dollars per share) | $ / shares 54.97
Vested and issued (in dollars per share) | $ / shares 43.40
Expired or forfeited (in dollars per share) | $ / shares 45.20
Outstanding, ending balance (in dollars per share) | $ / shares $ 49.39
v3.21.2
Share-based Compensation - Summary of Performance Shares Activity (Details) - Performance Shares
 6 Months Ended
Jun. 30, 2021
$ / shares
shares
Shares  
Outstanding, beginning balance (in shares) | shares 157,847
Granted (in shares) | shares 100,291
Vested and issued (in shares) | shares (8,987)
Expired or forfeited (in shares) | shares (17,334)
Outstanding, ending balance (in shares) | shares 231,817
Weighted-Average Grant Date Fair Value  
Outstanding, beginning balance (in dollars per share) | $ / shares $ 43.10
Granted (in dollars per share) | $ / shares 54.79
Vested and issued (in dollars per share) | $ / shares 44.49
Expired or forfeited (in dollars per share) | $ / shares 45.61
Outstanding, ending balance (in dollars per share) | $ / shares $ 47.91
v3.21.2
Underwriting, Acquisition and Insurance Expenses (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Underwriting, Acquisition and Insurance Expenses [Abstract]        
Commissions $ 71.7 $ 57.2 $ 148.2 $ 122.5
Other underwriting, acquisition and insurance expenses 104.0 98.2 210.6 205.2
Underwriting, acquisition and insurance expenses, total 175.7 155.4 358.8 327.7
Net deferral of policy acquisition costs 1.6 4.4 (5.1) 0.2
Total underwriting, acquisition and insurance expenses $ 177.3 $ 159.8 $ 353.7 $ 327.9
v3.21.2
Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Income Tax Disclosure [Abstract]        
Deferred tax assets, change in federal tax rate $ 7.4   $ 7.4  
Net operating losses carryback period     2 years  
Capital losses carryback period     3 years  
Change in valuation allowance (1.2) $ 0.0 $ (2.0) $ 0.0
Unrecognized tax benefits, period increase (decrease) 0.6   (1.8)  
Interest on income taxes expense 0.1   (0.4)  
Tax penalty expense $ 0.0   $ (0.4)  
v3.21.2
Income Taxes - Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 78.7 $ 5.9 $ 109.9 $ (19.8)
Effective Tax Rate 11.30% 191.50% 9.30% (52.00%)
Bermuda        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 2.3 $ (29.2) $ 7.3 $ (55.0)
Effective Tax Rate 0.00% 0.00% 0.00% 0.00%
United States        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 64.0 $ 66.2 $ 105.2 $ 55.6
Effective Tax Rate 21.90% 23.80% 19.40% 23.50%
United Kingdom        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 9.3 $ (29.2) $ (8.9) $ (27.6)
Effective Tax Rate (54.60%) 15.50% 115.30% 10.30%
Barbados        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 0.0 $ 0.0    
Effective Tax Rate 0.00% 0.00%    
Belgium        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 0.0 $ 0.1 $ 0.0 $ 0.1
Effective Tax Rate 0.00% 20.00% 0.00% 31.00%
Brazil        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 2.3 $ 0.6 $ 4.0 $ 2.8
Effective Tax Rate 0.00% 0.00% 0.00% 0.00%
United Arab Emirates        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 0.1 $ 0.5 $ 0.3 $ 1.3
Effective Tax Rate 0.00% 0.00% 0.00% 0.00%
Ireland        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 0.0 $ 0.0 $ (0.1) $ 0.0
Effective Tax Rate 0.00% 0.00% 0.00% 0.00%
Italy        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 0.4 $ (1.8) $ 1.2 $ 1.7
Effective Tax Rate 0.00% 0.00% 0.00% 0.00%
Malta        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 0.3 $ (1.3) $ 0.9 $ 1.3
Effective Tax Rate 0.00% 0.00% 0.00% 0.00%
Switzerland        
Income Tax Examination [Line Items]        
Pre-Tax Income (Loss) $ 0.0 $ 0.0 $ 0.0 $ 0.0
Effective Tax Rate 0.00% 1.00% 0.00% 0.90%
v3.21.2
Income Taxes - Reconciliation of Difference Between Provision for Income Taxes and Expected Tax Provision at Weighted Average Tax Rate (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Income Tax Disclosure [Abstract]        
Income tax provision at expected rate $ 16.5 $ 8.6 $ 22.8 $ 9.4
Tax effect of:        
Nontaxable investment income (0.1) (0.2) (0.3) (0.3)
Foreign exchange adjustments (0.3) 1.5 (0.5) (0.6)
Goodwill 0.0 1.0 0.0 1.0
Withholding taxes 0.1 0.0 0.1 0.1
Change in uncertain tax position liability 0.6 0.0 (1.8) 0.0
Change in valuation allowance (1.2) 0.0 (2.0) 0.0
Impact of change in tax rate related to Finance Act 2021 (7.4) 0.0 (7.4) 0.0
Other 0.7 0.4 (0.6) 0.7
Income tax provision $ 8.9 $ 11.3 $ 10.3 $ 10.3
v3.21.2
Commitments and Contingencies (Detail)
$ in Millions
 6 Months Ended
Jun. 30, 2021
USD ($)
Commitments and Contingencies Disclosure [Abstract]  
Contractual commitments related to its limited partnership investments (up to) $ 67.9
Contractual commitments period (not to exceed) 12 years
v3.21.2
Segment Information - Additional Information (Detail)
$ in Millions
 6 Months Ended
Jun. 30, 2021
USD ($)
segment
Dec. 31, 2020
USD ($)
Segment Reporting [Abstract]    
Number of reportable segments | segment 2  
Assets associated with trade capital providers | $ $ 602.3 $ 825.9
v3.21.2
Segment Information - Revenue and Income (Loss) Before Income Taxes for Each Segment (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Segment Reporting Information [Line Items]        
Earned premiums $ 470.3 $ 433.4 $ 936.4 $ 868.4
Net investment income 52.7 1.4 97.1 37.0
Net realized investment gains (losses) 24.7 17.9 37.8 (18.3)
Total revenue 547.7 452.7 1,071.3 887.1
(Loss) income before income taxes 78.7 5.9 109.9 (19.8)
Foreign currency exchange losses (4.4) (4.3) (5.7) (5.2)
Operating Segments        
Segment Reporting Information [Line Items]        
(Loss) income before income taxes 73.0 2.4 98.4 27.5
Corporate and Other        
Segment Reporting Information [Line Items]        
Net investment income 4.0 0.0 6.8 0.6
(Loss) income before income taxes (14.6) (10.1) (20.6) (23.8)
U.S. Operations | Operating Segments        
Segment Reporting Information [Line Items]        
Earned premiums 314.5 301.6 628.9 604.1
Net investment income 33.7 0.8 62.5 26.0
(Loss) income before income taxes 53.6 31.2 90.2 68.1
International Operations | Operating Segments        
Segment Reporting Information [Line Items]        
Earned premiums 155.7 131.8 307.2 264.1
Net investment income 13.9 0.5 25.9 9.1
(Loss) income before income taxes 19.5 (27.5) 7.7 (39.8)
Run-off Lines | Operating Segments        
Segment Reporting Information [Line Items]        
Earned premiums 0.1 0.0 0.3 0.2
Net investment income 1.1 0.1 1.9 1.3
(Loss) income before income taxes $ (0.1) $ (1.3) $ 0.5 $ (0.8)
v3.21.2
Segment Information - Schedule of Earned Premiums by Geographic Location (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]        
Total earned premiums $ 470.3 $ 433.4 $ 936.4 $ 868.4
United States        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Total earned premiums 314.2 301.4 627.0 601.1
United Kingdom        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Total earned premiums 116.8 75.5 215.8 162.2
Bermuda        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Total earned premiums 10.7 25.3 35.8 46.5
Malta        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Total earned premiums 11.0 18.5 25.0 30.3
All other jurisdictions        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Total earned premiums $ 17.6 $ 12.7 $ 32.8 $ 28.3
v3.21.2
Segment Information - Identifiable Assets (Detail) - USD ($)
$ in Millions
Jun. 30, 2021
Dec. 31, 2020
Segment Reporting, Asset Reconciling Item [Line Items]    
Identifiable assets $ 10,368.3 $ 10,465.8
Operating Segments | U.S. Operations    
Segment Reporting, Asset Reconciling Item [Line Items]    
Identifiable assets 5,704.0 6,032.2
Operating Segments | International Operations    
Segment Reporting, Asset Reconciling Item [Line Items]    
Identifiable assets 3,898.4 3,899.4
Operating Segments | Run-off Lines    
Segment Reporting, Asset Reconciling Item [Line Items]    
Identifiable assets 253.0 335.9
Corporate and Other    
Segment Reporting, Asset Reconciling Item [Line Items]    
Identifiable assets $ 512.9 $ 198.3