Argo Group International (ARGO-PA) 10-K 16 Mar 22 2021 FY Annual report Financial data

Cover

Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 14, 2022	Jun. 30, 2021
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 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 Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,796.5
Entity Common Stock, Shares Outstanding		34,888,872
Documents Incorporated by Reference	Part III of this report incorporates by reference specific portions of the Registrant's Proxy Statement relating to the 2022 Annual General Meeting of Shareholders to be filed within 120 days after the end of the fiscal year to which this report relates.
Entity Central Index Key	0001091748
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
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	6.500% Senior Notes due 2042 issued by Argo Group U.S., Inc.  and the Guarantee with respects thereto
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 7.00% Resettable Fixed Rate Preference Share, Series A, Par Value $1.00 Per Share
Trading Symbol	ARGOPrA
Security Exchange Name	NYSE

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2021
Auditor Information [Abstract]
Auditor Name	Ernst & Young LLP
Auditor Location	San Antonio, Texas
Auditor Firm ID	42

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Investments:
Fixed maturities available-for-sale, at fair value (cost: 2021 - $4,203.2, 2020 - $3,981.1; allowance for expected credit losses: 2021 - $2.5, 2020 - $6.6)	$ 4,223.3	$ 4,107.1
Equity securities, at fair value (cost: 2021 - $70.3; 2020 - $162.5)	56.3	176.7
Other investments (cost: 2021 - $387.0; 2020 - $429.4)	387.2	429.4
Short-term investments, at fair value (cost: 2021 - $655.4; 2020 - $541.4)	655.8	542.6
Investments	5,322.6	5,255.8
Cash	146.1	148.8
Accrued investment income	20.9	21.8
Premiums receivable	648.6	679.8
Reinsurance recoverables	2,966.4	3,009
Goodwill	147.3	147.3
Intangible assets, net of accumulated amortization	17.3	60.5
Current income taxes receivable, net	7.3	3
Deferred tax assets, net	73.6	16.7
Deferred acquisition costs, net	168	163.6
Ceded unearned premiums	506.7	575.1
Operating leases right-of-use assets	81.4	82
Other assets	211.6	294.7
Assets held for sale	0	7.7
Total assets	10,317.8	10,465.8
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses	5,595	5,406
Unearned premiums	1,466.8	1,464.8
Accrued underwriting expenses and other liabilities	166.6	167.6
Ceded reinsurance payable, net	724.4	950.4
Funds held	76.6	64.7
Senior unsecured fixed rate notes	140.3	140.2
Other indebtedness	57	60.7
Junior subordinated debentures	258.2	257.8
Operating lease liabilities	97.7	95.8
Total liabilities	8,582.6	8,608
Commitments and contingencies (Note 18)
Shareholders' equity:
Preferred shares and additional paid-in capital - $1.00 par, 30,000,000 shares authorized; 6,000 and 6,000 shares issued at December 31, 2021 and December 31, 2020, respectively; liquidation preference $25,000	144	144
Common shares - $1.00 par, 500,000,000 shares authorized; 46,192,867 and 46,009,966 shares issued at December 31, 2021 and December 31, 2020, respectively	46.2	46
Additional paid-in capital	1,386.4	1,380.2
Treasury shares (11,315,889 shares at December 31, 2021 and December 31, 2020, respectively)	(455.1)	(455.1)
Retained earnings	636.4	684.1
Accumulated other comprehensive income, net of taxes	(22.7)	58.6
Total shareholders' equity	1,735.2	1,857.8
Total liabilities and shareholders' equity	$ 10,317.8	$ 10,465.8

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Amortized Cost	$ 4,203.2	$ 3,981.1
Allowance for Credit Losses	2.5	6.6
Equity securities, cost	70.3	162.5
Other investments, cost	387	429.4
Short-term investments, cost	$ 655.4	$ 541.4
Preferred shares, par value (in dollars per share)	$ 1	$ 1
Preferred shares, authorized (in shares)	30,000,000	30,000,000
Preferred shares, issued (in shares)	6,000	6,000
Preferred stock, liquidation preference (in dollars per share)	$ 25,000	$ 25,000
Common shares, par value (in dollars per share)	$ 1	$ 1
Common shares, shares authorized (in shares)	500,000,000	500,000,000
Common shares, shares issued (in shares)	46,192,867	46,009,966
Treasury shares (in shares)	11,315,889	11,315,889

Consolidated Statements of Inco

Consolidated Statements of Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Premiums and other revenue:
Earned premiums	$ 1,910.1	$ 1,780.5	$ 1,729.7
Net investment income	187.6	112.7	151.1
Net realized investment gains (losses):
Net realized investment gains (losses)	72.4	26	120.9
Change in fair value recognized	(40.4)	10.3	(40.8)
Credit losses on fixed maturities	0.6	(39.9)	0
Net realized investment gains (losses)	32.6	(3.6)	80.1
Total revenue	2,130.3	1,889.6	1,960.9
Expenses:
Losses and loss adjustment expenses	1,314.6	1,208.8	1,220.7
Underwriting, acquisition and insurance expenses	702.3	667.7	666
Non-operating expenses	43.7	21.1	37.6
Interest expense	21.6	26.9	34.1
Fee and other (income) expense, net	(2)	(3.9)	(3.3)
Foreign currency exchange (gains) losses	1.6	15.4	(9.8)
Impairment of goodwill and intangibles	43.2	0	15.6
Total expenses	2,125	1,936	1,960.9
Income (loss) before income taxes	5.3	(46.4)	0
Income tax provision (benefit)	(1.4)	7.7	14.1
Net income (loss)	6.7	(54.1)	(14.1)
Dividends on preferred shares	10.5	4.6	0
Net income (loss) attributable to common shareholders, diluted	(3.8)	(58.7)	(14.1)
Net income (loss) attributable to common shareholders, basic	$ (3.8)	$ (58.7)	$ (14.1)
Net loss attributable to common shareholders per common share:
Basic (in dollars per share)	$ (0.11)	$ (1.70)	$ (0.41)
Diluted (in dollars per share)	(0.11)	(1.70)	(0.41)
Dividend declared per common share (in dollars per share)	$ 1.24	$ 1.24	$ 1.24
Weighted average common shares:
Basic (in shares)	34,816,160	34,614,813	34,205,954
Diluted (in shares)	34,816,160	34,614,813	34,205,954
Other-than-temporary impairment losses recognized in earnings:
Net realized investment gains (losses) before other-than-temporary impairment losses	$ 32.6	$ (3.6)	$ 100.4
Other-than-temporary impairment losses on fixed maturities	0	0	(20.3)
Investment impairment losses recognized in earnings	$ 0	$ 0	$ (20.3)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 6.7	$ (54.1)	$ (14.1)
Other comprehensive income (loss):
Foreign currency translation adjustments	2.6	(15.3)	(0.2)
Defined benefit pension plans:
Net gain arising during the year	1.9	(0.6)	(1.8)
Unrealized gains (losses) on fixed maturity securities:
(Losses) gains arising during the year	(94.7)	95.2	88
Reclassification adjustment for losses (gains) included in net income	(12.2)	(12.8)	9.9
Other comprehensive (loss) income before tax	(102.4)	66.5	95.9
Defined benefit pension plans:
Net gain arising during the year	0.4	(0.1)	(0.4)
Unrealized gains (losses) on fixed maturity securities:
(Losses) gains arising during the year	(17.3)	16.5	14.2
Reclassification adjustment for (gains) losses included in net income	(4.2)	0	1.2
Income tax (benefit) provision related to other comprehensive income (loss)	(21.1)	16.4	15
Other comprehensive (loss) income, net of tax	(81.3)	50.1	80.9
Comprehensive (loss) income	$ (74.6)	$ (4)	$ 66.8

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) shares in Millions, $ 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 EarningsCumulative 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, 2018	$ 1,735		$ 0	$ 45.3	$ 1,372	$ (455.1)	$ 850.9		$ (78.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(14.1)						(14.1)
Other comprehensive loss - change in fair value of fixed maturities, net of taxes	82.5								82.5
Other comprehensive income, net - other	(1.6)								(1.6)
Activity under stock incentive plans	16.3			0.6	15.7
Retirement of common shares (tax payments on equity compensation)	(13.8)			(0.2)	(13.6)
Employee stock purchase plan	2.5				2.5
Cash dividend declared - common shares	$ (43.1)						(43.1)
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Ending Balance at Dec. 31, 2019	$ 1,763.7	$ (2.2)	0	45.7	1,376.6	(455.1)	793.7	$ (7.9)	2.8	$ 5.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(54.1)						(54.1)
Preferred shares issued	144		144
Other comprehensive loss - change in fair value of fixed maturities, net of taxes	65.9								65.9
Other comprehensive income, net - other	(15.8)								(15.8)
Activity under stock incentive plans	8.1			0.4	7.7
Retirement of common shares (tax payments on equity compensation)	(6.7)			(0.1)	(6.6)
Employee stock purchase plan	2.5				2.5
Dividends on preferred shares	(4.6)						(4.6)
Cash dividend declared - common shares	(43)						(43)
Ending Balance at Dec. 31, 2020	1,857.8		144	46	1,380.2	(455.1)	684.1		58.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	6.7						6.7
Other comprehensive loss - change in fair value of fixed maturities, net of taxes	(85.4)								(85.4)
Other comprehensive income, net - other	4.1								4.1
Activity under stock incentive plans	7.1			0.2	6.9
Retirement of common shares (tax payments on equity compensation)	(2.8)			$ (0.1)	(2.7)
Employee stock purchase plan (in shares)				0.1
Employee stock purchase plan	2.1				2
Dividends on preferred shares	(10.5)						(10.5)
Cash dividend declared - common shares	(43.9)						(43.9)
Ending Balance at Dec. 31, 2021	$ 1,735.2		$ 144	$ 46.2	$ 1,386.4	$ (455.1)	$ 636.4		$ (22.7)

Consolidated Statements of Sh_2

Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Stockholders' Equity [Abstract]
Cash dividend declared - common shares, per share (in dollars per share)	$ 1.24	$ 1.24	$ 1.24

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows provided by operating activities:
Net income (loss)	$ 6.7	$ (54.1)	$ (14.1)
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Amortization and depreciation	43.4	33.2	27.3
Share-based payments expense	8	8.7	16.9
Deferred income tax benefit, net	(38.6)	(21.6)	(23.5)
Net realized investment (gains) losses	(32.6)	3.6	(80.1)
Undistributed earnings from alternative investment portfolio	(95.5)	(8.6)	(19.9)
Loss on disposals of long-lived assets, net	23.3	5.5	7.2
Impairment of goodwill and intangibles	43.2	0	15.6
Change in:
Accrued investment income	0.8	3.9	1.5
Receivables	47.4	84.8	(455.1)
Deferred acquisition costs	0.8	(4.6)	7
Ceded unearned premiums	65.7	(33.2)	(87.8)
Reserves for losses and loss adjustment expenses	210.8	280.2	509
Unearned premiums	7.2	63.7	111.7
Ceded reinsurance payable and funds held	(207.3)	(238.2)	243.3
Income taxes	(4.5)	(17.5)	11.4
Accrued underwriting expenses and other liabilities	3	(43.7)	(10.6)
Other, net	17.9	9.8	(77)
Net cash flows from operating activities	99.7	71.9	182.8
Cash flows used in investing activities:
Sales of fixed maturity investments	992.9	1,080	1,394.3
Maturities and mandatory calls of fixed maturity investments	717.7	569.8	522.2
Sales of equity securities	125.8	25.4	374.7
Sales of other investments	212.3	103.9	83.1
Purchases of fixed maturity investments	(1,932.9)	(2,038.1)	(1,859.1)
Purchases of equity securities	(5.3)	(78.9)	(61.2)
Purchases of other investments	(47.4)	(35.5)	(63.7)
Change in foreign regulatory deposits and voluntary pools	(27.1)	(5.4)	0
Change in short-term investments	(116.4)	285.4	(490.4)
Settlements of foreign currency exchange forward contracts	(1.2)	9.4	0.3
Proceeds from sale of Ariel Re, net of cash transferred	0	28.3	0
Proceeds from sale of Trident assets	0	38	0
Sale (Purchases) of fixed assets, net	18	(20.2)	(29.9)
Other, net	7.7	13.6	(13.1)
Cash used in investing activities	(55.9)	(24.3)	(142.8)
Cash flows from financing activities:
Payment of long-term debt	0	(125)	(0.6)
Issuance of preferred shares, net of issuance costs	0	144	0
Activity under stock incentive plans	1.3	1.8	1.9
Payment of cash dividends to preferred shareholders	(10.5)	(4.6)	0
Payment of cash dividends to common shareholders	(43.7)	(43)	(43.1)
Cash used in financing activities	(52.9)	(26.8)	(41.8)
Effect of exchange rate changes on cash	6.4	(9.8)	(0.1)
Change in cash	(2.7)	11	(1.9)
Cash, beginning of year	148.8	137.8	139.7
Cash, end of period	$ 146.1	$ 148.8	$ 137.8

Business and Significant Accoun

Business and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Business and Significant Accounting Policies	Business and Significant Accounting Policies Business Argo Group International Holdings, Ltd. (“Argo Group,” “we” or the “Company”) is an underwriter of specialty insurance products in the property and casualty market. Argo Group U.S., Inc. (“Argo Group U.S.”) is a subsidiary of Argo Financial Holding (Ireland) UC (“Argo Ireland”). Argo Underwriting Agency Limited (“Syndicate 1200”) is a subsidiary of Argo International Holdings, Ltd., Argo Re Ltd. (“Argo Re”), a Bermuda based company, is the parent of both Argo Ireland and Argo International Holdings, Ltd. Argo Re is directly owned by Argo Group. On February 15, 2022, we completed the sale of our Brazilian operations, Argo Seguros Brasil S.A. (“Argo Seguros”), to Spice Private Equity Ltd., an investment company focused on global private equity investments. For further disclosures see Note 2, “Recent Acquisitions, Disposals & Other Transactions.” Effective November 25, 2020, we completed the sale of Ariel Re, to Pelican Ventures and J.C. Flowers & Co. Ariel Re is the reinsurance platform through which Lloyd’s Syndicate 1910 reinsurance business is underwritten. Under the terms of the agreement, the buying group’s corporate member provided Syndicate 1910’s capital for the 2021 Lloyd’s year of account, and Argo Group has agreed to retain historical reserves and the remaining exposure for the 2020 and prior Lloyd’s years of account. We conduct our ongoing business through two primary segments - U.S. Operations and International Operations. In addition to these main business segments, we have a Run-off Lines segment for certain products we no longer underwrite. U.S. Operations is comprised of the Excess and Surplus Lines businesses focusing on the U.S.-based risks that the standard, admitted insurance market is unwilling or unable to write, and through other specialized admitted and non-admitted business distributed through retail, wholesale, and managing general brokers/agents in the specialty insurance market. Excess and Surplus Lines products are underwritten by Colony Insurance Company (“Colony”). The other U.S. specialized admitted and non-admitted businesses consist of the following operations: Argo Pro, U.S. Specialty Programs, Argo Surety, Rockwood Casualty Insurance Company (“Rockwood”), Argo Insurance and Inland Marine. International Operations is comprised of the Lloyd’s Syndicate platform (Syndicate 1200), Argo Insurance Bermuda, Continental Europe and Latin America. Syndicate 1200 insurance products are underwritten by Argo Underwriting Agency Limited based in London, under the Lloyd’s of London (“Lloyd’s”) global franchise. The additional International Operations business include ArgoGlobal SE in Malta, ArgoGlobal Assicurazoni in Italy, and Argo Seguros in Brazil. These businesses provide a broad range of commercial property, casualty, professional liability and specialty coverages in a number of countries and jurisdictions outside the United States (“U.S.”). Our Run-off Lines segment includes liabilities associated with other liability policies that were issued in the 1960s, 1970s and into the 1980s, as well as the former risk-management business and other business no longer underwritten. Basis of Presentation and Use of Estimates The consolidated financial statements of Argo Group and its subsidiaries have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The preparation of consolidated 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 differ from those estimates. Specifically, estimates for reserves for losses and loss adjustment expenses are based upon past claim experience modified for current trends as well as prevailing economic, legal and social conditions. Although management believes that amounts included in the accompanying consolidated financial statements are reasonable, such estimates may be more or less than the amounts ultimately paid when the claims are settled. The estimates are continually reviewed and any changes are reflected in current operating results. Further, the nature of loss exposures involves significant variability due to the nature of the long-tailed payments on certain claims. As such, losses and loss adjustment expenses could vary significantly from the recorded amounts. The consolidated financial statements include the accounts and operations of Argo Group and its subsidiaries. All material intercompany accounts and transactions have been eliminated. In order to conform the 2020 and 2019 consolidated statements of income (loss) to the 2021 presentation the Company has (a) offset fee income to fee expense, and (b) reclassified amounts from net realized investment gain (losses) and underwriting, acquisition and insurance expenses to non-operating expenses. Amounts related to trade capital providers, who are third-party capital participants that provide underwriting capital to Syndicate 1200 are included in the balance sheet. Trade capital providers participate on a quota share basis, assuming 100% of their contractual participation in the underwriting syndicate results and with such results settled on a year of account basis. We have evaluated our investment in our eleven statutory trusts (collectively, the “Trusts”) and one charitable foundation (the “Foundation”) under the Financial Accounting Standards Board’s (“FASB’s”) provisions for consolidation of variable interest entities under Accounting Standards Codification (“ASC”) Topic 810-10, “Consolidation,” as amended. We determined that the Trusts and the Foundation are variable interest entities due to the fact that the Trusts and the Foundation do not have sufficient equity to finance their activities without additional subordinate financial support from other parties. We do not have any power to direct the activities that impact the Trusts’ or the Foundation’s economic performance. We are not entitled to receive a majority of the residual returns of the Trusts. Additionally, we are not responsible for absorbing the majority of the expected losses of the Trusts; therefore, we are not the primary beneficiary and, accordingly, the Trusts are not included in our consolidated financial statements. The expenses and donations of the charitable foundation in Bermuda are paid by Argo Group and have been included in the consolidated results. Risks and Uncertainties Related to COVID-19 Certain risks and uncertainties are inherent to our day-to-day operations. Adverse changes in the economy could lower demand for our insurance products or negatively impact our investment results, both of which could have an adverse effect on the revenue and profitability of our operations. The global COVID-19 pandemic has resulted in and may continue to result in significant disruptions in economic activity and financial markets. The cumulative effects of COVID-19 on the Company, and the effect of any other public health outbreak, cannot be predicted at this time, but could reduce demand for our insurance policies, result in increased level of losses, settlement expenses or other operating costs, reduce the market value of invested assets held by the Company or negatively impact the fair value of our goodwill. Our liquidity and capital resources were not materially impacted by COVID-19 and related economic conditions during the year ended December 31, 2021. Cash Cash consists of cash deposited in operating accounts with commercial banks. Interest-bearing cash accounts are classified as short term investments. Investments Investments in fixed maturities at December 31, 2021 and 2020 include bonds and structured securities. Equity securities include common stocks, preferred stocks and mutual funds. Other investments consist of foreign regulatory deposits, hedge funds, private equity funds, private equity direct investments, and voluntary pools. Short-term investments consist of money market funds, certificates of deposit, bonds, sovereign debt and interest-bearing cash accounts. Investments maturing in less than one year are classified as short-term investments in our consolidated financial statements. The amortized cost of fixed maturity securities is adjusted for amortization of premiums and accretion of discounts. This amortization or accretion is included in “Net investment income” in our Consolidated Statements of Income (Loss). For the structured securities portion of the fixed maturity securities portfolio, we recognize income using a constant effective yield based on anticipated prepayments and the estimated economic life of the securities. Premium or discount on high investment grade securities (rated AA or higher) is amortized into income using the retrospective method. Premium or discount on lower grade securities (rated less than AA) is amortized into income using the prospective method. Our investments in fixed maturities are considered available-for-sale and are carried at fair value. As available-for-sale investments, changes in the fair value of fixed maturities are not recognized in income during the period, but rather are recognized as a separate component of shareholders’ equity until realized. Fair value of these investments is estimated using prices obtained from third-party pricing services, where available. For securities where we were unable to obtain fair values from a pricing service or broker, fair values were estimated using information obtained from investment advisors. We performed several processes to ascertain the reasonableness of these investment values by (1) obtaining and reviewing internal control reports for our service providers that obtain fair values from third-party pricing services, (2) obtaining and reviewing evaluated pricing methodology documentation from third-party pricing services and (3) comparing the security pricing received from a secondary third-party pricing service versus the prices used in the consolidated financial statements and obtaining additional information for variances that exceeded a certain threshold. As of December 31, 2021, investments reported at fair value for which we did not receive a fair value from a pricing service or broker accounted for less than 1% of our investment portfolio. The actual value at which such securities could be sold or settled with willing buyer or seller may differ from such estimated fair values depending on a number of factors including, but not limited to, current and future economic conditions, the quantity sold or settled, the presence of an active market and the availability of a willing buyer or seller. The cost of securities sold is based on the specific identification method. Our investments in equity securities are reported at fair value, changes in the fair value of equity securities are now included in “Net realized investment (gains) losses” in our consolidated statements of income. Changes in the value of other investments consisting of hedge funds, private equity funds, private equity direct investments and voluntary pools are principally recognized in income during the period using the equity method of accounting. Our 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. The underlying assets are invested in government securities, agency securities and corporate bonds whose values are obtained from Lloyd’s. Foreign currency future contracts held by us are valued by our counterparties using market driven foreign currency exchanges rates. We regularly review our investments to identify and evaluate those that may have credit impairments. For fixed maturity securities, the evaluation for credit losses is generally based on the present value of expected cash flows of the security as compared to the amortized book value, the financial condition, near-term and long-term prospects for the issuer, including industry conditions, implications of rating agency actions, the likelihood of principal and interest recoverability and whether it is more likely than not we will be required to sell the investment prior to the anticipated recovery in value. Effective January 1, 2020 with the adoption of ASU 2016-13 Financial Instruments-Credit Losses, we recognize credit losses on fixed maturities through an allowance account. For fixed maturities that we do not intend to sell or for which it is more likely than not we will not be required to sell prior to the anticipated recovery in value, we separate the credit component of the impairment from the component related to all other market factors and report the credit loss component to net realized investment gains (losses) in the Consolidated Statement of Income (Loss). The impairment related to all other market factors is reported as a separate component of shareholder’s equity in other comprehensive income (loss). The credit loss allowance account is adjusted for any additional credit losses or subsequent recoveries and the cost basis of the fixed maturity security is not adjusted. For fixed maturity securities that we intend to sell or for which it is more likely than not that we will be required to sell before an anticipated recovery in value, the full amount of the impairment is recognized in net realized investment gains (losses) in the Consolidated Statement of Income and the cost basis of the fixed maturity security is adjusted to reflect the recognized realized loss. The new cost basis is not adjusted for any recoveries in fair value. We report accrued investment income separately from fixed maturity securities and have elected to not measure an allowance for credit losses for accrued investment income. The write-off of investment income accrued for fixed maturities that have defaulted on interest payments is recognized as a loss in net realized investment gains (losses), in the period of the default, in the Consolidated Statement of Income (Loss). All investment balances include amounts relating to trade capital providers. The results of operations and other comprehensive income exclude amounts relating to trade capital providers. Trade capital providers’ participation in the syndicate results are included in reinsurance recoverable for ceded losses and reinsurance payable for ceded premiums. Receivables Premiums receivable, representing amounts due from insureds, are presented net of an allowance for uncollectible premiums, including expected credit losses, both dispute and credit related. Premiums receivable include amounts relating to the trade capital providers’ quota share. The allowance is based upon our ongoing review of amounts outstanding, historical loss data, including delinquencies and write-offs, current and forecasted economic conditions and other relevant factors. Credit risk is partially mitigated by our ability to cancel the policy if the policyholder does not pay the premium. Reinsurance recoverables represent amounts of paid losses and loss adjustment expenses, case reserves and incurred but not reported (“IBNR”) amounts ceded to reinsurers under reinsurance treaties. Reinsurance recoverables also reflect amounts that are due from trade capital providers. Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. We report our reinsurance recoverables net of an allowance for estimated uncollectible reinsurance, including expected credit losses. The allowance is based upon our ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors. We use the rating-based method to estimate the uncollectible reinsurance reserves due to credit losses. Under this method, reinsurance credit risk is estimated by considering the reinsurers probability of default. Reinsurance recoverables are forecasted out of the assumed billing periods and a liquidation factor is applied based on the rating of the reinsurer and adjusted as needed based on our historical experience with the reinsurers. Additionally, reinsurance receivable balances are evaluated to identify any dispute risk and when required, an additional reserve is recorded. Amounts deemed to be uncollectible, including amounts due from known insolvent reinsurers, are written off against the allowance. Changes in the allowance, as well as any subsequent collections of amounts previously written off, are reported as part of underwriting expense. We evaluate and monitor the financial condition of our reinsurers under voluntary reinsurance arrangements to minimize our exposure to significant losses from reinsurer insolvencies. Recoveries occur when subsequent collection or litigation results in the receipt of amounts previously written off. Amounts recovered are applied against the allowance for expected credit losses. For further disclosures about the allowance for expected credit losses, see Note 4, “Allowance for Credit Losses.” Earned Premiums Premium revenue is generally recognized ratably over the policy period. Premiums that have yet to be earned are reported as “unearned premiums” in our consolidated balance sheets. Unearned premium balances include cessions to reinsurers including trade capital providers, while the earned premium recognized in our consolidated statements of income (loss) excludes amounts relating to trade capital providers. The trade capital providers’ quota share amount is included in “ceded reinsurance payable, net”. Assumed reinstatement premiums that reinstate coverage are written and earned at the time the associated loss event occurs. The original premium is earned over the remaining exposure period of the contract. Reinstatement premiums are estimated based upon contract terms for reported losses and estimated for incurred but not reported losses. Retrospectively Rated Policies We have written a number of workers compensation, property and other liability policies that are retrospectively rated. Under this type of policy, the policyholder or coverholder may be entitled, subsequent to coverage expiration, to a refund or may owe additional premiums based on the amount of losses incurred under the policy. The retrospective premium adjustments on certain policies are limited to a minimum or maximum premium adjustment, which is calculated as a percentage of the standard amount of premium charged during the life of the policy. Accrued retrospectively rated premiums have been determined based on estimated ultimate loss experience of the individual policyholder accounts. The estimated liability for return of premiums under retrospectively rated policies is included in “Unearned premiums” in our consolidated balance sheets and was $4.7 million and $1.5 million at December 31, 2021 and 2020, respectively. The estimated amount included in premiums receivables for additional premiums due under retrospectively rated policies was $0.1 million and $0.1 million at December 31, 2021 and 2020, respectively. Deferred Acquisition Costs Policy acquisition costs, which include commissions, premium taxes, fees and certain other costs of underwriting policies, are deferred, when such class of policies are profitable, and amortized over the same period in which the related premiums are earned. To qualify for capitalization, the policy acquisition cost must be directly related to the successful acquisition of an insurance contract. Anticipated investment income is considered in determining whether the deferred acquisition costs are recoverable and whether a premium deficiency exists. We continually review the methods of making such estimates and establishing the deferred costs with any adjustments made in the accounting period in which the adjustment arose. The 2021 and 2020 net amortization of policy acquisition costs will not equal the change in our consolidated balance sheets as the trade capital providers’ share is not reflected in our consolidated statements of income (loss) and differences arise from foreign currency exchange rates applied to deferred acquisition costs which are treated as a nonmonetary asset. Leases We determine if a contract contains a lease at inception and recognize operating lease right-of-use assets and operating lease liabilities based on the present value of the future minimum lease payments at the commencement date. As our leases do not provide an implicit interest rate, we use our incremental borrowing rate based on the information available at the commencement date to determine the present value of future payments. Lease agreements have lease and non-lease components. We account for these components separately, therefore our operating lease right-of-use asset and operating lease liabilities represent base rent only. Lease expense is recognized on a straight-line basis over the lease term. Renewal options are evaluated prior to the expiration date and recorded upon exercise. We adopted ASU 2016-02, “Leases” (Topic 842) on the effective date of January 1, 2019 and applied the following practical expedients: • We have elected to adopt this standard using the option transition method, which allows companies to continue applying the guidance under the lease standard in effect at that time in the comparative periods presented in the consolidated financial statements. The adoption of the standard had no effect on our consolidated shareholders’ equity. Prior periods were not restated. • We have elected the “package of practical expedients,” which permits us not to reassess under the new standard our prior conclusion about lease identification, lease classification and initial direct costs. • Where we are the lessor, we have elected the practical expedient which permits us to not separate non-lease components from the associated lease components if the non-lease components otherwise would be accounted for in accordance with the new revenue standard. Reserves for Losses and Loss Adjustment Expenses Liabilities for unpaid losses and loss adjustment expenses include the accumulation of individual case estimates for claims reported as well as estimates of IBNR claims and estimates of claim settlement expenses. Reinsurance recoverables on unpaid claims and claim expenses represent estimates of the portion of such liabilities that will be recoverable from reinsurers. Amounts recoverable from reinsurers are recognized as assets at the same time and in a manner consistent with the unpaid claims liabilities associated with the reinsurance policy. Reinsurance In the normal course of business, our insurance subsidiaries cede risks above certain retention levels to other insurance companies. Reinsurance recoverables include claims we paid and estimates of unpaid losses and loss adjustment expenses that are subject to reimbursement under reinsurance and retrocessional contracts. The method for determining reinsurance recoverables for unpaid losses and loss adjustment expenses involves reviewing actuarial estimates of gross unpaid losses and loss adjustment expenses to determine our ability to cede unpaid losses and loss adjustment expenses under our existing reinsurance contracts. This method is continually reviewed and updated and any resulting adjustments are reflected in earnings in the period identified. Reinsurance premiums, commissions and expense reimbursements are accounted for on a basis consistent with those used in accounting for the original policies issued and the term of the reinsurance contracts. Amounts recoverable from reinsurers for losses and loss adjustment expenses for which our insurance and reinsurance subsidiaries have not been relieved of their legal obligations to the policyholder are reported as assets. Goodwill and Intangible Assets Goodwill and intangible assets are allocated to the segment in which the results of operations for the acquired company are reported (see Note 19, “Segment Information” for further discussion). Intangible assets with a finite life are amortized over the estimated useful life of the asset. Goodwill and intangible assets with an indefinite useful life are not amortized. Goodwill and intangible assets are tested for impairment on an annual basis or more frequently if events or changes in circumstances indicate that the carrying amount may not be recoverable. We perform our annual goodwill and intangible asset impairment test on the first day of the fourth quarter of each year, October 1, of each year. In conjunction with our annual test, the fair value of each reporting unit exceeded its carrying value for the year ended December 31, 2021, except for our Syndicate 1200 reporting unit. As a result of this testing, we determined that the carrying value of this reporting unit exceeded the fair value by $43.2 million. Goodwill assigned to this reporting unit totaled $28.7 million (pre-tax) and indefinite-lived intangible assets totaled $60.5 million (pre-tax). In accordance with ASC Topic 350-10, “Impairment and Disposal of Long-Lived Assets”, we applied the impairment against the indefinite-lived intangible asset, resulting in a carrying value of $17.3 million. Our Syndicate 1200 reporting unit in past years has been adversely impacted by catastrophe and other losses. As a result, we have exited a number of business lines, focusing on profitability. Due to the change in our business plan, we performed a stress test on our fair value testing, focusing on low to negative growth. The result of this stress testing resulted in the indication that the carrying value of the reporting unit exceeded its fair value, resulting in the impairment. For the year ended December 31, 2020, the fair value of each reporting unit exceeded its carrying value. As a result, no impairment charges were recognized. In conjunction with our annual test, the fair value of each reporting unit exceeded its carrying value for the year ended December 31, 2019, except for our Lloyd’s reporting unit. As a result of this testing, we determined that the goodwill of the Lloyd’s reporting unit, which is included in our International Operations segment, was fully impaired and recorded a pre-tax charge of $15.6 million. Our Lloyd’s reporting unit was adversely impacted by a continuing soft market. Additionally, we incurred higher than expected losses and loss adjustment expenses due to adverse prior accident year loss reserve development resulting from the receipt of new information in the second half of 2019 relating to claims trends across various lines of business, coupled with increased current accident year losses and loss adjustment expenses as a result of these claim trends. Using these facts and trends, we calculated the discounted cash flows for the Lloyd’s reporting unit, which resulted in the indication that the carrying value of the reporting unit exceeded its fair value, resulting in the impairment. On April 30, 2020, we sold our Trident Public Risk Solutions (“Trident”) brand and wrote off $4.9 million of goodwill as a result of the Trident transaction. On November 25, 2020, we sold Ariel Re’s premium renewal rights and wrote off $9.2 million of goodwill and $30.2 million of intangible assets, net of accumulated amortization, as a result of the Ariel Re transaction. For more information about these transactions, see Note 2, “Recent Acquisitions, Disposals & Other Transactions.” The following table presents our intangible assets and accumulated amortization at December 31: December 31, 2021 2020 (in millions) Gross Carrying Accumulated Gross Carrying Accumulated Lloyd's capacity $ 17.3 n/a $ 60.5 n/a Distribution network 45.5 45.5 45.5 45.5 Other 6.2 6.2 6.2 6.2 $ 69.0 $ 51.7 $ 112.2 $ 51.7 As of December 31, 2020, all of our finite-lived intangible assets had been fully amortized and we had no amortization expense for the year ended December 31, 2021. During the years ended December 31, 2020 and 2019, amortization expense was $1.1 million and $1.7 million, respectively, and is included in “underwriting, acquisition and insurance expenses” in our consolidated statements of income (loss). The entirety of the amortization expense recorded in the year 2020 relates to Ariel Re and was calculated pro-rata before the sale. Property and Equipment Property and equipment used in operations, including certain costs incurred to develop or obtain computer software for internal use, are capitalized and carried at cost less accumulated depreciation and are reported in “other assets” in our consolidated balance sheets. Depreciation is calculated using a straight-line method over the estimated useful lives of the assets, generally three Assets Held for Sale In December 2019, we entered into a series of agreements with a real estate firm to market and sell four company owned condominiums. During 2020, we sold two of the condominiums and the remaining two condominiums were sold in January 2021 and November 2021. We had classified these properties and other corporate assets as “Assets held for sale” of $7.7 million in our Consolidated Balance Sheets as of December 31, 2020. We recorded the assets at their fair market values as of December 31, 2020 based on independent appraisals and active listing prices. As a result of the reclassification to “Assets held for sale,” we recorded a pre-tax gain of $0.3 million as of December 31, 2021 and pretax losses of $0.8 million and $3.7 million for the years ended December 31, 2020 and 2019, respectively, which are included in “Non-operating expenses” in our Consolidated Statements of Income (Loss) for the years ended December 31, 2021, 2020 and 2019, respectively. These assets and the related pre-tax losses are reported as part of our Corporate and Other reporting segment in Note 19, “Segment Information.” Derivative Instruments We enter into short-term, currency spot and forward contracts to manage operational currency exposure from our non-USD insurance operations,and gain exposure to a total return strategy which invests in multiple currencies. The forward contracts are typically thirty to ninety days and are renewed as management deems necessary to accomplish the objectives of the contracts. These foreign currency forward contracts are carried at fair value in our Consolidated Balance Sheets in “Other assets” at December 31, 2021 and 2020, respectively. The realized and unrealized gains and losses are included in “Net realized investment and other gains (losses) in our Consolidated Statements of Income. The forwards contracts are not designated as hedges for accounting purposes. Share-Based Payments Compensation expense for share-based payments is recognized based on the measurement-date fair value for awards that will settle in shares. Compensation expense for awards that are settled in equity are recognized on a straight line pro rata basis over the vesting period, adjusted for expected forfeitures. See Note 14, “Share-based Compensation” for related disclosures. Foreign Currency Exchange Gain (Loss) The reporting currency of the Company is the U.S. dollar (“USD”). USD is the functional currency of all but three of our foreign operations. For foreign operations with the U.S. dollar as the functional currency, monetary assets and liabilities that are denominated in local currencies are remeasured at the exchange rates in effect at the balance sheet date. The resulting gains and losses from changes in the foreign exchange rates are reflected in net income. Non-monetary assets and liabilities are not remeasured. In the case of our non-USD denominated available-for-sale investments, the change in exchange rates between the local currency and USD at each balance sheet date represents an unrealized appreciation or depreciation in value of these securities and is included as a component of accumulated other compr

Recent Acquisitions, Disposals

Recent Acquisitions, Disposals & Other Transactions	12 Months Ended
	Dec. 31, 2021
Business Combinations [Abstract]
Recent Acquisitions, Disposals & Other Transactions	Recent Acquisitions, Disposals & Other Transactions Sale of Trident Brand and Platform On April 30, 2020, we sold our Trident brand and underwriting platform to Paragon Insurance Holdings, LLC (“Paragon”) and received $38 million in cash, with additional consideration in future periods depending on performance post-closing. In connection with the terms of agreement to sell the Trident brand, Paragon continues to write business on Argo paper (Argonaut Insurance Company, Argonaut Great Central Insurance Company, Argonaut Midwest Insurance Company and Peleus Insurance Company) through a managing general agency agreement. 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 pre-tax loss of $10.5 million reduction in the original gain on sale for the year ended December 31, 2021. This transaction is included in "Net realized investment gains (losses)" in our Consolidated Statements of Income (Loss) for the year ended December 31, 2021. We recognized a pre-tax gain of $31.8 million related to the sale, for the year ended December 31, 2020. Trident is reported within our U.S. Operations reporting segment. Acquisition of Ariel Indemnity Limited Effective June 12, 2020, Argo Group and our subsidiary Argo Re, Ltd. (“Argo Re”) acquired 100% of the capital stock of Ariel Indemnity Limited (“AIL”) for consideration of $55.6 million. The acquisition of AIL was made pursuant to the former owners (the “Sellers”) of Maybrooke Holdings, S.A. (“Maybrooke”) exercising a put option within the Administrative Services Agreement (“ASA”) between the Company and the Sellers. The ASA was part of the stock purchase agreement between the Company and the Sellers related to our February 6, 2017 acquisition of Maybrooke, the since-liquidated holding company of the Ariel Re platform. The $55.6 million sales price is equal to the 2019 year-end tangible net worth of AIL, less certain administrative costs. Upon acquiring AIL, we dissolved AIL and merged it into Argo Re. The acquisition was accounted for in accordance with ASC 805, “Business Combinations.” Purchase accounting, as defined by ASC 805, requires that the assets acquired and liabilities assumed be recognized at their fair values as of the acquisition date. The fair values disclosed herein were determined based on management’s best estimates and the finalization of certain valuation analyses during the fourth quarter of 2020. Provisional fair values were recorded in the Company’s interim consolidated financial statements and notes for the period ended September 30, 2020. AIL’s financial position, results of operations, and cash flows were not material to our consolidated financial results as of and for the year ended December 31, 2020. No goodwill or intangible assets were recognized from this transaction. Reinsurance-to-close ("RITC") of ArgoGlobal Syndicate 1200 On October 12, 2020, ArgoGlobal, the Lloyd’s insurer and member of Argo Group, announced a reinsurance-to-close (“RITC”) transaction with legacy specialist RiverStone. RiverStone provided an RITC of ArgoGlobal’s Syndicate 1200 for 2017 and prior years with net technical provision of approximately $219.7 million. The transaction received regulatory approval on January 29, 2021, with the RITC becoming effective on January 1, 2021. Sale of Ariel Re On November 25, 2020, we completed the sale of Ariel Re, to Pelican Ventures and J.C. Flowers & Co. Under the terms of the agreement, we received $30 million at closing. Ariel Re is the reinsurance platform through which Lloyd’s Syndicate 1910 reinsurance business is underwritten. We recognized a loss of $9.4 million related to the sale, which is included in "Net realized investment (losses) gains" in our Consolidated Statements of Income (Loss) for the year ended December 31, 2020. Ariel Re is one of the business units within our International Operations reporting segment. Pelican Ventures and affiliates capitalized the 2021 year of account, and Argo Group maintains responsibility for all years of account 2020 and prior. Additionally, in accordance with the transaction agreement, Ariel Re’s equity interests in ArgoGlobal Services (Hong Kong) Limited (“AGSL”) and Ariel Re Bda Limited (“ARBL”) were transferred to Pelican Ventures and J.C. Flowers & Co. AGSL is authorized in Hong Kong by the Insurance Agency of Hong Kong as an insurance agent and is a Lloyd's approved coverholder. ARBL is an exempted company limited by shares, incorporated in Bermuda and registered as an insurance agent under the Bermuda Insurance Act. Sale of Argo Seguros Brasil S.A.

Investments

Investments	12 Months Ended
	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Investments	Investments Included in “total investments” in our consolidated balance sheets at December 31, 2021 and 2020 is $89.6 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 and fair value in fixed maturity investments were as follows: December 31, 2021 (in millions) Amortized Gross Gross Allowance for Credit Losses (1) Fair Fixed maturities U.S. Governments $ 422.7 $ 5.5 $ 3.2 $ — $ 425.0 Foreign Governments 234.7 2.2 3.9 0.2 232.8 Obligations of states and political subdivisions 166.7 5.8 1.2 — 171.3 Corporate bonds 1,972.3 33.5 20.3 2.2 1,983.3 Commercial mortgage-backed securities 416.7 6.3 4.3 — 418.7 Residential mortgage-backed securities 480.7 7.5 5.7 — 482.5 Asset-backed securities 173.0 1.3 0.6 0.1 173.6 Collateralized loan obligations 336.4 1.3 1.6 — 336.1 Total fixed maturities $ 4,203.2 $ 63.4 $ 40.8 $ 2.5 $ 4,223.3 December 31, 2020 (in millions) Amortized Gross Gross Allowance for Credit Losses Fair Fixed maturities U.S. Governments $ 385.4 $ 14.7 $ 0.3 $ — $ 399.8 Foreign Governments 284.1 11.6 0.7 0.2 294.8 Obligations of states and political subdivisions 163.1 7.7 0.3 0.1 170.4 Corporate bonds 1,925.9 75.3 13.3 6.1 1,981.8 Commercial mortgage-backed securities 324.8 15.2 0.3 — 339.7 Residential mortgage-backed securities 491.4 17.4 0.6 — 508.2 Asset-backed securities 120.5 2.9 0.4 0.2 122.8 Collateralized loan obligations 285.9 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 December 31, 2021, by contractual maturity, were as follows: (in millions) Amortized Fair Due in one year or less $ 281.7 $ 284.6 Due after one year through five years 1,692.0 1,704.8 Due after five years through ten years 710.0 711.3 Thereafter 112.6 111.6 Structured securities 1,406.9 1,411.0 Total $ 4,203.2 $ 4,223.3 The expected maturities may differ from the contractual maturities because debtors may have the right to call or prepay obligations. Other Invested Assets Details regarding the carrying value and unfunded investment commitments of the other invested assets portfolio as of December 31, 2021 and 2020 were as follows: December 31, 2021 (in millions) Carrying Unfunded Investment Type Hedge funds $ 58.6 $ — Private equity 248.9 64.2 Overseas deposits 74.9 — Other 4.8 — Total other investments $ 387.2 $ 64.2 December 31, 2020 (in millions) Carrying Unfunded Investment Type Hedge funds $ 111.2 $ — Private equity 211.4 80.0 Overseas deposits 102.1 — Other 4.7 — 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 and Other-than-temporary Impairments An aging of unrealized losses on our investments in fixed maturities is presented below: December 31, 2021 Less Than One Year One Year or Greater Total (in millions) Fair Unrealized Fair Unrealized Fair Unrealized Fixed maturities U.S. Governments $ 193.4 $ 2.6 $ 14.6 $ 0.6 $ 208.0 $ 3.2 Foreign Governments 152.4 3.3 2.6 0.6 155.0 3.9 Obligations of states and political subdivisions 46.0 0.8 0.1 0.4 46.1 1.2 Corporate bonds 854.3 18.3 41.7 2.0 896.0 20.3 Commercial mortgage-backed securities 198.8 4.1 6.5 0.2 205.3 4.3 Residential mortgage-backed securities 284.2 5.6 4.0 0.1 288.2 5.7 Asset-backed securities 62.6 0.6 — 62.6 0.6 Collateralized loan obligations 176.1 1.6 0.5 176.6 1.6 Total fixed maturities $ 1,967.8 $ 36.9 $ 70.0 $ 3.9 $ 2,037.8 $ 40.8 December 31, 2020 Less Than One Year One Year or Greater Total (in millions) Fair Unrealized Fair Unrealized Fair Unrealized Fixed maturities U.S. Governments $ 40.6 $ 0.3 $ — $ — $ 40.6 $ 0.3 Foreign Governments 18.0 0.5 0.1 0.2 18.1 0.7 Obligations of states and political subdivisions 5.2 0.3 — — 5.2 0.3 Corporate bonds 202.5 6.7 17.5 6.6 220.0 13.3 Commercial mortgage-backed securities 21.8 0.3 — — 21.8 0.3 Residential mortgage-backed securities 74.4 0.4 3.0 0.2 77.4 0.6 Asset-backed securities 4.6 0.4 — — 4.6 0.4 Collateralized loan obligations 121.1 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 5,207 fixed maturity securities, of which 697 were in an unrealized loss position for less than one year and 82 were in an unrealized loss position for a period one year or greater as of December 31, 2021. For fixed maturities for which a decline in the fair value between the amortized cost is 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 period. 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. Prior to the adoption of ASU 2016-13, the evaluation for a credit loss was generally based on the present value of expected cash flows of the security as compared to the amortized cost. For structured securities, frequency and severity of loss inputs were used in projecting future cash flows of the securities. Loss frequency was measured on the credit default rate, which included factors such as loan-to-value ratios and credit scores of borrowers. If a determination was made that the unrealized loss was other-than-temporary, a realized loss was recognized in the realized investment losses in the Statement of Income (Loss) and the amortized cost basis of the security was reduced to reflect the loss. Foreign Governments Obligations of states and political subdivisions Corporate bonds Asset backed securities Total Beginning balance, January 1, 2020 $ — $ — $ — $ — $ — Additions-initial adoption of accounting standard — — 6.8 0.1 6.9 Securities for which allowance was not previously recorded 0.3 0.3 15.3 — 15.9 Securities sold during the period (0.2) — (39.0) (0.1) (39.3) Additional net increases (decreases) in existing allowance 0.1 (0.2) 23.0 0.2 23.1 Ending balance, December 31, 2020 $ 0.2 $ 0.1 $ 6.1 $ 0.2 $ 6.6 Foreign Governments Obligations of states and political subdivisions Corporate bonds Asset backed securities Total Beginning balance, January 1, 2021 $ 0.2 $ 0.1 $ 6.1 $ 0.2 $ 6.6 Securities for which allowance was not previously recorded — — 2.7 0.2 2.9 Securities sold during the period — — (3.5) — (3.5) Additional net increases (decreases) in existing allowance — (0.1) (3.1) (0.3) (3.5) Ending balance, December 31, 2021 $ 0.2 $ — $ 2.2 $ 0.1 $ 2.5 Total change in allowance for credit losses included in net realized investment gains (losses) in the Consolidated Statement of Income was $0.6 million and $(39.9) million for the year ended December 31, 2021 and 2020, respectively. Net Investment Income Investment income and expenses were as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Investment income: Interest on fixed maturities $ 98.9 $ 108.6 $ 129.5 Dividends on equity securities 3.1 2.8 11.1 Income on alternative investments 95.5 10.4 22.4 Income on short-term and other investments 3.3 3.9 8.9 Investment income 200.8 125.7 171.9 Investment expenses (13.2) (13.0) (20.8) Net investment income $ 187.6 $ 112.7 $ 151.1 Net Realized Investment Gains and Losses The following table presents our realized investment gains (losses): For the Years Ended December 31, (in millions) 2021 2020 2019 Realized gains on fixed maturities and other Fixed maturities $ 30.6 $ 37.1 $ 22.2 Other investments, including short-terms 9.8 93.8 0.1 Other assets 3.3 33.2 33.0 43.7 164.1 55.3 Realized losses on fixed maturities and other Fixed maturities (11.8) (35.2) (11.7) Other investments, including short-terms (18.5) (78.6) (31.3) Other assets (12.5) (7.2) — (42.8) (121.0) (43.0) Net (losses) recognized on fixed maturities and other Credit losses on fixed maturities 0.6 (39.9) — Other-than-temporary impairment losses — — (20.3) Other (6.3) — — (5.7) (39.9) (20.3) Equity securities Net realized gains (losses) on equity securities 71.5 (17.1) 128.9 Change in unrealized gains (losses) on equity securities held at the end of the period (34.1) 10.3 (40.8) Net realized gains (losses) on equity securities 37.4 (6.8) 88.1 Net realized investment and other gains (losses) before income taxes 32.6 (3.6) 80.1 Income tax (benefit) provision 6.2 1.3 16.2 Net realized investment gains (losses), net of income taxes $ 26.4 $ (4.9) $ 63.9 The cost of securities sold is based on the specific identification method. Changes in unrealized appreciation (depreciation) related to investments are summarized as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Change in unrealized gains (losses) Fixed maturities $ (105.9) $ 96.0 $ 93.3 Other investments — (14.3) 4.4 Other and short-term investments (1.0) 0.7 0.2 Net unrealized investment gains (losses) before income taxes (106.9) 82.4 97.9 Income tax provision (benefit) (21.5) 16.5 15.4 Net unrealized investment gains (losses), net of income taxes $ (85.4) $ 65.9 $ 82.5 Foreign Currency Exchange Forward Contracts We entered into foreign currency exchange forward contracts to manage operational currency exposure from our non-USD insurance operations, , 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 assets” at December 31, 2021 and 2020. The gains and losses are included in “net realized investment and other gains” in our consolidated statements of income (loss). The fair value of our foreign currency exchange forward contracts as of December 31 was as follows: (in millions) December 31, 2021 December 31, 2020 Operational currency exposure $ (0.3) $ 0.4 Asset manager investment exposure (0.3) (0.2) Total return strategy — 0.7 Total $ (0.6) $ 0.9 The following table presents our gross investment realized gains and losses on our foreign currency exchange forward contracts: For the Years Ended December 31, (in millions) 2021 2020 2019 Realized gains Operational currency exposure $ 16.5 $ 13.2 $ 5.7 Asset manager investment exposure 3.7 2.2 2.7 Total return strategy 13.0 61.6 22.5 Gross realized investment gains 33.2 77.0 30.9 Realized losses Operational currency exposure (28.9) (8.6) (10.6) Asset manager investment exposure (1.0) (4.0) (0.8) Total return strategy (12.0) (62.3) (17.6) Gross realized investment losses (41.9) (74.9) (29.0) Net realized investment gains (losses) on foreign $ (8.7) $ 2.1 $ 1.9 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 at December 31: (in millions) December 31, 2021 December 31, 2020 Securities on deposit for regulatory and other purposes $ 195.6 $ 227.5 Securities pledged as collateral for letters of credit and other 193.9 189.4 Securities and cash on deposit supporting Lloyd’s business (1) 296.8 409.2 Total restricted investments $ 686.3 $ 826.1 (1) Argo Group is required to maintain “Funds at Lloyd’s” or “FAL” to support its business for Syndicate 1200 and Syndicate 1910. At December 31, 2021 the amount pledged for FAL was $296.8 million, of which $140.3 million was provided by Argo Re. 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 and income 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 assumptions 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 December 31, 2021 and 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: • U.S. 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. • U.S. 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 Level 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 a broker and an independent valuation service, both based upon estimates and assumptions. 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) December 31, 2021 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities U.S. Governments $ 425.0 $ 417.4 $ 7.6 $ — Foreign Governments 232.8 — 232.8 — Obligations of states and political subdivisions 171.3 — 171.3 — Corporate bonds 1,983.3 — 1,980.5 2.8 Commercial mortgage-backed securities 418.7 — 418.7 — Residential mortgage-backed securities 482.5 — 482.5 — Asset-backed securities 173.6 — 173.6 — Collateralized loan obligations 336.1 — 336.1 — Total fixed maturities 4,223.3 417.4 3,803.1 2.8 Equity securities 56.3 41.6 — 14.7 Other investments 75.4 — 75.4 — Short-term investments 655.8 653.9 1.9 — $ 5,010.8 $ 1,112.9 $ 3,880.4 $ 17.5 (a) Quoted prices in active markets for identical asset (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 Governments 294.8 — 294.8 — Obligations of states and political subdivisions 170.4 — 170.4 — Corporate bonds 1,981.8 — 1,974.8 7.0 Commercial mortgage-backed securities 339.7 — 339.7 — Residential mortgage-backed securities 508.2 — 508.2 — Asset-backed securities 122.8 — 122.8 — Collateralized loan obligations 289.6 — 289.6 — Total fixed maturities 4,107.1 383.5 3,716.6 7.0 Equity securities 176.7 159.2 — 17.5 Other investments 102.5 0.4 102.1 — Short-term investments 542.6 526.5 16.1 — $ 4,928.9 $ 1,069.6 $ 3,834.8 $ 24.5 (a) Quoted prices in active markets for identical asset (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) Credit Financial Equity Total Beginning balance, January 1, 2021 $ 7.0 $ 17.5 $ 24.5 Transfers into Level 3 — 1.0 1.0 Transfers out of Level 3 — — — Total gains or losses (realized/unrealized): Included in net income — 4.2 4.2 Included in other comprehensive income (0.8) — (0.8) Purchases, issuances, sales, and settlements: Purchases 0.1 1.2 1.3 Issuances — — — Sales (3.5) (10.6) (14.1) Settlements — — — Ending balance, December 31, 2021 $ 2.8 $ 13.3 $ 16.1 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, 2021 $ — $ — $ — (in millions) Credit Financial Equity 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: Purchases 0.1 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 December 31, 2021 and 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.

Allowance for Credit Losses

Allowance for Credit Losses	12 Months Ended
	Dec. 31, 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 uncollectible premiums, including expected credit losses, at December 31, 2021 and January 1, 2021, and the changes in the allowance for the year ended December 31, 2021. (in millions) Premiums Receivable, Net of Allowance for Estimated Uncollectible Premiums Allowance for Estimated Uncollectible Premiums Balance, January 1, 2021 $ 679.8 $ 9.4 Current period change for estimated uncollectible premiums (3.1) Write-offs of uncollectible premiums receivable (0.6) Foreign exchange adjustments — Balance, December 31, 2021 $ 648.6 $ 5.7 Reinsurance Recoverables The following table presents the balances of reinsurance recoverables, net of the allowance for estimated uncollectible reinsurance, including expected credit losses, at December 31, 2021 and January 1, 2021, and changes in the allowance for estimated uncollectible reinsurance for the year ended December 31, 2021. (in millions) Reinsurance Recoverables, Net of Allowance for Estimated Uncollectible Reinsurance Allowance 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, December 31, 2021 $ 2,966.4 $ 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.

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	Leases Our operating lease obligations are for office facilities, corporate housing and equipment. Our leases have remaining lease terms ranging between less than 1 year and 13 years, some of which include options to extend the leases. Expenses associated with leases totaled $18.3 million for the year ended December 31, 2021, as compared to $20.3 million for the year ended December 31, 2020. The components of lease expense, and other lease information, as of and during the year ended December 31, 2021 and 2020 are as follows: December 31, (in millions) 2021 2020 Operating leases right-of-use assets $ 81.4 $ 82.0 Operating lease liabilities 97.7 95.8 Operating lease weighted-average remaining lease term 9.51 10.50 Operating lease weighted-average discount rate 3.53 % 3.77 % For the Year Ended December 31, (in millions) 2021 2020 Operating lease costs $ 14.2 $ 15.3 Variable lease costs 6.2 5.4 Sublease income (2.1) (0.4) Total lease costs $ 18.3 $ 20.3 Operating cash flows from operating leases (fixed payments) $ 14.9 $ 15.7 Operating cash flows from operating leases (liability reduction) $ 12.8 $ 12.8 Our finance leases and short-term leases as of December 31, 2021 and 2020 were not material. Future minimum lease payments under operating leases as of December 31, 2021 were as follows: December 31, (in millions) 2021 2022 13.8 2023 13.4 2024 11.8 2025 11.6 2026 11.2 Thereafter 54.4 Total future minimum lease payments $ 116.2 Future lease obligations Less imputed interest (18.5) Total operating lease liability $ 97.7 We have certain investment properties that we lease to independent, third parties. These properties consist of an office building that is currently leased through August 2026 and one condominium that was leased on a short-term basis. The carrying value of the office building is included in “Other assets” on our consolidated balance sheet. The condominium was placed for sale in December 2019, and sold in January 2021. The carrying value of this condominium is included in the “Assets held for Sale” on our consolidated balance sheet. Income for these leased properties was $1.4 million for the year ended December 31, 2021 and $2.6 million for the year ended December 31, 2020. Income for these leased properties is included in “fee and other income” on our consolidated statements of income (loss).

Reinsurance

Reinsurance	12 Months Ended
	Dec. 31, 2021
Insurance [Abstract]
Reinsurance	ReinsuranceWe reinsure certain risks with other insurance companies. Such arrangements serve to limit our maximum loss on certain individual risks as well as on catastrophes and large or unusually hazardous risks. We are liable to our insureds for reinsurance ceded in the event our reinsurers do not meet their obligations. Thus, a credit exposure exists with respect to reinsurance ceded to the extent that any reinsurer is unable or unwilling to meet the obligations assumed under the reinsurance contracts. Our allowance for uncollectible reinsurance balances receivable on paid losses and incurred claims was $3.8 million and $4.1 million as of December 31, 2021 and 2020, respectively (see Note 4, “Allowance for Credit Losses” for additional information). Under certain reinsurance agreements, collateral, including letters of credit, is held to secure performance of reinsurers in meeting their obligations. The amount of such collateral was $1,085.5 million and $1,131.4 million at December 31, 2021 and 2020, respectively. The collateral we hold does not apply to our entire outstanding reinsurance recoverable. Rather, collateral is provided on an individual contract basis, as appropriate. For each individual reinsurer, the collateral held may exceed or fall below the total outstanding recoverable from that individual reinsurer. The long-term nature of the reinsurance contracts creates a credit risk to us over time arising from potentially uncollectible reinsurance. To mitigate that counterparty risk, we evaluate our reinsurers to assess their financial condition. The factors that underlie these reviews include a financial risk assessment as well as an internal assessment of the capitalization and the operational risk of the reinsurer. As a result of these reviews, we may make changes to the approved markets that are used in both our treaty and facultative reinsurance programs. Estimated losses recoverable from reinsurers and the ceded portion of unearned premiums are reported as assets in our consolidated balance sheets. Included in “reinsurance recoverables” are paid loss recoverables of $494.6 million and $509.1 million as of December 31, 2021 and 2020, respectively. “Earned premiums” and “losses and loss adjustment expenses” are reported net of reinsurance in our consolidated statements of income (loss). Losses and loss adjustment expenses of $1,314.6 million, $1,208.8 million and $1,220.7 million for the years ended December 31, 2021, 2020 and 2019, respectively, are net of amounts ceded to reinsurers of $829.6 million, $941.3 million and $1,031.1 million, respectively. We are required to accept certain assigned risks and other legally mandated reinsurance obligations. Prior to the mid-1980s, we assumed various forms of casualty reinsurance for which we continue to maintain reserves for losses and loss adjustment expenses (see Note 8, “Run-off Lines”). For such assumed reinsurance transactions, we engage in various monitoring steps that are common with assumed reinsurance such as ongoing claims reviews. We assumed property related reinsurance primarily through, Argo Re and Ariel Re, and casualty related reinsurance primarily through Syndicate 1200. Premiums were as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Direct written premiums $ 2,990.6 $ 2,676.1 $ 2,510.4 Reinsurance ceded to other companies (1,203.9) (1,423.2) (1,375.6) Reinsurance assumed from other companies 190.6 557.2 619.8 Net written premiums $ 1,977.3 $ 1,810.1 $ 1,754.6 Direct earned premiums $ 2,917.7 $ 2,660.6 $ 2,412.4 Reinsurance ceded to other companies (1,272.7) (1,388.6) (1,286.7) Reinsurance assumed from other companies 265.1 508.5 604.0 Net earned premiums $ 1,910.1 $ 1,780.5 $ 1,729.7 Percentage of reinsurance assumed to net earned premiums 13.9 % 28.6 % 34.9 %

Reserves for Losses and Loss Ad

Reserves for Losses and Loss Adjustment Expenses	12 Months Ended
	Dec. 31, 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 Years Ended December 31, (in millions) 2021 2020 2019 Net reserves beginning of the year $ 2,906.1 $ 2,722.7 $ 2,562.9 Net AIL reserves acquired — 27.9 — Add: Losses and LAE incurred during current calendar year, net of reinsurance: Current accident year 1,176.3 1,201.1 1,082.6 Prior accident years 138.3 7.7 138.1 Losses and LAE incurred during calendar year, net of reinsurance 1,314.6 1,208.8 1,220.7 Deduct: Losses and LAE payments made during current calendar year, net of reinsurance: Current accident year 180.8 253.4 224.3 Prior accident years 688.4 866.4 806.0 Losses and LAE payments made during current calendar year, net of reinsurance: 869.2 1,119.8 1,030.3 Net reserve ceded - reinsurance to close transaction for years of account 2017 and prior (1) 219.7 — — Change in participation interest (2) 8.4 32.8 (14.4) Foreign exchange adjustments (17.0) 33.7 (16.2) Net reserves - end of period 3,123.2 2,906.1 2,722.7 Add: Reinsurance recoverables on unpaid losses and LAE, end of period 2,471.8 2,499.9 2,434.9 Gross reserves - end of period $ 5,595.0 $ 5,406.0 $ 5,157.6 (1) Amount represents a decrease in reserves due to an RITC to RiverStone, see Note 2, recent acquisitions, disposals & other transactions. (2) Amount represents (decrease) increase in reserves due to change in our Syndicate 1200 and Syndicate 1910 participation. 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. Underwriting results for the year ended December 31, 2021 included net losses and loss adjustment expenses attributed to the COVID-19 pandemic of $12.4 million, primarily resulting from contingency and property exposures in the Company’s International Operations. Property losses relate to sub-limited affirmative business interruption coverage, primarily in certain International markets, as well as expected costs associated with claims handling. The impact from the unfavorable (favorable) development of prior accident years’ losses and LAE reserves on each reporting segment is presented below: For the Years Ended December 31, (in millions) 2021 2020 2019 U.S. Operations $ 120.9 $ 2.4 $ 15.7 International Operations (26.9) (6.2) 110.4 Run-off Lines 44.3 11.5 12.0 Total (favorable) unfavorable prior-year development $ 138.3 $ 7.7 $ 138.1 The following describes the primary factors behind each segment’s prior accident year reserve development for the years ended December 31, 2021, 2020 and 2019: Year ended December 31, 2021: • U.S. Operations: Net unfavorable development in liability and professional lines, partially offset by favorable development in specialty. The liability lines and professional lines prior-year development was largely due to movements in the fourth quarter of 2021. The liability lines movement was largely due to actual incurred loss movements greater than the expected movements in business units with significant exposure to claims alleging construction defect ($112.1 million of prior year development), driven by accident years 2017 and prior. The professional lines movement was driven by evaluations of individual management liability claims. The professional lines prior-year development of $33.0 million was driven by accident years 2018 and prior. • International Operations: Net favorable development primarily related to favorable development in liability and property lines, partially offset by unfavorable development in Argo Insurance Bermuda. The unfavorable movement in Argo Insurance Bermuda was driven by liability and professional losses. • Run-off Lines: Net unfavorable loss reserve development in run-off liability lines, including asbestos and environmental lines, and risk management workers compensation. The movement on liability exposures excluding asbestos and environmental was due to analysis of individual claims. The exposures driving the change were largely the result of claims alleging abuse. A large portion of the change was due to defense costs. The movement on asbestos and environmental lines was due to higher than expected loss activity and movements on large claims alleging environmental losses. Year ended December 31, 2020: • U.S. Operations: Net unfavorable development in liability and professional lines, partially offset by favorable development in specialty and property. • International Operations: Net favorable development primarily related to favorable development in Reinsurance, partially offset by unfavorable development in Bermuda Insurance. The favorable development in Reinsurance was due to experience on catastrophe losses from recent years and decreases on claims from older accident years. The unfavorable movement in Bermuda Insurance was driven by professional and liability losses. • Run-off Lines: Net unfavorable loss reserve development in asbestos and environmental lines and other run-off lines, partially offset by favorable loss reserve development on prior accident years in risk management workers compensation. Year ended December 31, 2019: • U.S. Operations: Net unfavorable development in professional, property and liability lines partially offset by favorable development in specialty lines. The unfavorable professional lines development was driven by movements on individual large management liability claims primarily impacting accident years 2015 through 2017. The unfavorable property development was primarily driven by large excess claims resulting from the 2017 and 2018 catastrophe events. The unfavorable liability lines development was driven by actual loss activity greater than expected. The three most recent accident years showed unfavorable development partially offset by favorable development on older years. The favorable specialty lines development was driven by favorable experience in the surety business across multiple accident years. • International Operations: Net unfavorable development was primarily concentrated in liability and professional lines. The charges impacted our Bermuda casualty and professional divisions, and our Syndicate 1200 and European operations. The charges in our Bermuda business stemmed from public utility business in our casualty division, which we previously exited, as well as updated estimates on a number of other casualty and professional claims based on new information received in the last three quarters of 2019. As it relates to Syndicate 1200, the adverse development generally related to businesses that we have previously exited or where aggressive remedial underwriting actions have been taken. As it relates to Europe, the adverse development primarily related to certain coverholders whose contracts were previously terminated or where aggressive remedial underwriting actions have been taken as well as unexpected movements in large professional liability losses. This unfavorable development was primarily due to obtaining additional information on several individual claims, including investigations regarding causes of the incidents leading to the losses, reports provided by outside counsel, audits of the underlying losses and recent court decisions, settlements and jury awards. The result was an increase in the number of claims with the potential for underlying losses to reach our attachment point, particularly within our Bermuda Operations. Adverse development in Syndicate 1200 related to large claims involving the marine and energy and liability divisions. Losses on small and medium enterprise package business were also higher than expected. The unfavorable development during the year was also attributable to the results of ongoing audits, underwriting reviews, and updates from third-party coverholders, which included the identification of differences from original expectations with regard to the classes written, the distribution of writings by geography, and the rates charged by the coverholders. • Run-off Lines: Net unfavorable development in asbestos and environmental and other run-off segments partially offset by favorable development in risk management workers compensation. The change in asbestos was driven by assumed business where accounts are staying open longer than expected. The change in environmental was driven by individual claims on direct business. 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. The spread of COVID-19 and related economic shutdown has increased the uncertainty that is always present in our estimate of the ultimate cost of loss and settlement expense. Actuarial models base future emergence on historic experience, with adjustments for current trends, and the appropriateness of these assumptions involved more uncertainty as of December 31, 2021. We expect there will be impacts to the timing of loss emergence and ultimate loss ratios for certain coverages we underwrite. The industry is experiencing new issues, including the temporary suspension of civil court cases in most states, the extension of certain statutes of limitations and the impact on our insureds from a significant reduction in economic activity. Our booked reserves include consideration of these factors, but legislative, regulatory or judicial actions could result in loss reserve deficiencies and reduce earnings in future periods. Short-Duration Contract Disclosures Our basis for disaggregating short-duration contracts is by each of our two ongoing reporting segments, U.S. Operations and International Operations, with International Operations further disaggregated by operating divisions. We have chosen to disaggregate the data in this way so as to not obscure useful information by otherwise aggregating items with significantly different characteristics. See Note 19, “Segment Information,” for additional information regarding our two ongoing reporting segments. Operating Divisions Our U.S. Operations reporting segment is comprised of one primary operating division (see Note 19, “Segment Information” for additional information on U.S Operations). International Operations’ primary operating divisions are Argo Insurance Bermuda and Syndicate 1200. Each of these operating divisions are further described below. Argo Insurance Bermuda Argo Insurance Bermuda offers casualty, property and professional lines, which serves the needs of global clients by providing the following coverages: property, general and products liability, directors and officers liability, errors and omissions liability and employment practices liability. Syndicate 1200 The Syndicate 1200 division is focused on underwriting property, specialty and non-U.S. liability insurance and reinsurance through Argo Underwriting Agency, Ltd. on behalf of Lloyd’s Syndicate 1200 within the Lloyd’s of London global franchise. Lines of Business We use an underwriting committee structure to monitor and evaluate the operating performance of our lines of business. The underwriting committees are organized to allow products or coverages with similar characteristics to be managed and evaluated in distinct groups. Using this approach, our insurance business is categorized into underwriting groups, which are Liability, Professional, Property and Specialty. Noted below are descriptions of the types of characteristics considered to disaggregate our business into these groups, as well as other qualitative factors to consider when using the information contained in the following incurred and paid claims development tables. Liability Our Liability business generally covers exposures where most claims are reported without a significant time lag between the event that gives rise to a claim and the date the claim is reported to us. However, since facts and information are frequently not complete at the time claims are reported to us, and because protracted litigation is sometimes involved, it can be several years before the ultimate value of these claims is determined. In our Argo Bermuda Insurance division, much of the business covers higher layers, potentially increasing the time it takes to fully determine our exposure. Professional Much of our Professional business is written on a claims-made basis resulting in coverage only for claims that are reported to us during the year in which the policy is effective, thus reducing the number of claims that will become known to us after the end of the policy expiration date. However, facts and information are frequently not complete at the time claims are reported to us, and protracted litigation is sometimes involved. It can be several years before the ultimate value of these claims is determined. In our Argo Bermuda Insurance division, much of the business covers higher layers, potentially increasing the time it takes to fully determine our exposure. Property Property losses are generally reported within a short period of time from the date of loss, and in most instances, property claims are settled and paid within a relatively short timeframe. However, Property can be impacted by catastrophe losses which can be more complex than non-catastrophe Property claims due to factors such as difficulty accessing impacted areas and other physical, legal and regulatory impediments potentially extending the period of time it takes to settle and pay claims. The impacts of catastrophe losses can be more significant in our Reinsurance and Syndicate 1200 divisions. Specialty Specialty lines losses are generally reported within a short period of time from the date of loss, and in most instances, Specialty lines claims are settled and paid within a relatively short timeframe. However, Specialty lines can be impacted by larger losses where facts and information are frequently not complete at the time claims are reported to us. These large losses can be more complex than smaller Specialty claims due to factors such as difficulty determining actual damages and other physical, legal and regulatory impediments potentially extending the period of time it takes to settle and pay claims. Descriptions of the primary types of coverages, as disclosed in the following tables, included in the significant lines of business for each operating division are noted below: U.S Operations • Liability: primary and excess specialty casualty, general liability, commercial multi-peril, workers compensation, product liability, environmental liability, and auto liability • Professional: management liability, transaction liability and errors and omissions liability • Property: primary and excess property, inland marine and auto physical damage • Specialty: surety, animal mortality and ocean marine Argo Insurance Bermuda • Liability: directors and officers liability, errors and omissions liability and employment practices liability Syndicate 1200 • Liability : general liability, international casualty and motor treaties • Professional : professional indemnity, directors and officer’s liability, and medical malpractice • Property : direct and facultative excess insurance, North American and international binders, and residential collateral protection for lending institutions • Specialty : personal accident, aviation, cargo, yachts, and onshore and offshore marine Run-off Lines Segment We have a Run-off Lines segment for certain products that we no longer underwrite, including asbestos and environmental claims. We have excluded the Run-off Lines segment from the following disaggregated short-duration contract disclosures due to its insignificance to our consolidated financial position and results of operations, both quantitatively and qualitatively. Gross reserves for losses and LAE in Run-off Lines account for less than 5% of our consolidated gross reserves for losses and LAE, and are primarily related to accident years prior to the mid-1990s. As such, claims development tables for the most recent ten Foreign Currency Portions of the business we write in the Syndicate 1200 and Argo Bermuda Insurance is denominated in foreign currencies. We used the December 31, 2021 balance sheet foreign exchange rates to recast the incurred and paid claims information for all periods presented in the following claims development tables in order to eliminate the effects of changes in foreign currency translation rates. Lloyd’s Reinsurance to Close Process Syndicate 1200 and Syndicate 1910 are subject to the reinsurance to close process at Lloyd’s where a year of account stays open for three years and is then reinsured into the next year of account. As a result, our economic participation on the years reinsured into the next year of account can change, perhaps significantly. We recast the incurred and paid claims information for all periods presented in the following claims development tables in order to eliminate the effects of the changes in economic participation. In addition, the assets and liabilities for the 2017 and prior years of account for Syndicate 1200 were transferred to Riverstone as part of the reinsurance to close transaction effective on January 1, 2021. As a result, losses from the 2017 and prior years of account are no longer included in the Syndicate 1200 triangles. Reserves for IBNR Claims Reserves for IBNR claims are based on the estimated ultimate cost of settling claims, including the effects of inflation and other social and economic factors, using past experience adjusted for current trends and any other factors that would modify past experience. We use a variety of statistical and actuarial techniques to analyze current claims costs, including frequency and severity data and prevailing economic, social and legal factors. Each such method has its own set of assumptions and outputs, and each has strengths and weaknesses in different areas. Since no single estimation method is superior to another method in all situations, the methods and assumptions used to project loss reserves will vary by coverage and product. Given the long-tail nature of some of our claims, judgement used in selecting actuarial assumptions and weighing the indications of the various actuarial methods in developing our ultimate loss selection may have a material impact on our reserves. Construction defect and professional liability claims are two examples where determining the ultimate claims liability can be complex and challenging. Claims on these lines are subject to greater inherent variability than is typical of the remainder of the Company’s reserves, and are highly dependent upon court settlements, economic conditions, and the predictability of those results inherently have a larger range of potential outcomes. We use what we believe to be the most appropriate set of actuarial methods and assumptions for each product line grouping and coverage. While the loss projection methods may vary by product line and coverage, the general approach for calculating IBNR remains the same: ultimate losses are forecasted first, and that amount is reduced by the amount of cumulative paid claims and case reserves. Reserves established in prior years are adjusted as loss experience develops and new information becomes available. Adjustments to previously estimated reserves are reflected in the results of operations in the year in which they are made. As described above, various actuarial methods are used to determine the reserves for losses and LAE recorded in our consolidated balance sheets. Weightings of methods at a detailed level may change from evaluation to evaluation based on a number of observations, measures, and time elements. There were no significant changes to the methods and assumptions underlying our consolidated reserve estimations and selections as of December 31, 2021. Incurred & Paid Claims Development Disclosures The following tables provide information about incurred and cumulative paid losses and allocated loss adjustment expenses (“ALAE”), net of reinsurance. The following tables also include IBNR reserves plus expected development on reported claims and the cumulative number of reported claims as of December 31, 2021. Reporting Segment: U.S. Operations Line of Business: Liability (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 329.9 $ 342.3 $ 339.3 $ 336.9 $ 335.9 $ 329.7 $ 328.9 $ 327.2 $ 328.2 $ 329.3 2013 344.5 355.8 361.0 360.4 351.5 346.6 343.1 344.8 357.3 2014 328.6 337.1 330.0 326.3 323.9 321.9 327.4 341.3 2015 339.8 343.8 330.3 328.7 328.0 335.4 347.9 2016 342.6 350.5 342.4 353.0 355.3 379.0 2017 374.8 373.7 384.3 397.7 431.7 2018 426.1 430.4 414.5 420.4 2019 421.1 423.7 427.1 2020 404.2 386.7 2021 416.5 Total $ 3,837.2 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 37.3 $ 103.8 $ 169.8 $ 226.6 $ 263.2 $ 285.3 $ 295.4 $ 305.3 $ 313.2 $ 315.7 2013 36.5 109.7 174.3 228.8 266.5 289.3 306.9 318.2 325.4 2014 32.4 91.0 154.6 206.9 240.6 266.3 283.2 291.4 2015 33.7 86.9 140.2 195.6 236.4 263.9 289.3 2016 28.5 84.5 144.1 217.1 255.6 293.8 2017 27.8 83.0 158.8 238.5 295.2 2018 34.3 98.9 175.8 245.5 2019 32.4 113.6 186.1 2020 25.6 85.9 2021 27.6 Total $ 2,355.9 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance 59.4 Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 1,540.7 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 329.3 $ 35.6 27,587 2013 357.3 48.4 27,258 2014 341.3 56.3 23,473 2015 347.9 54.2 21,729 2016 379.0 60.7 18,693 2017 431.7 102.3 20,868 2018 420.4 117.0 23,150 2019 427.1 181.8 22,270 2020 386.7 261.2 17,001 2021 416.5 366.6 11,344 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. (2) During 2021, the Company revised the manner in which it measures reported claims. The cumulative number of reported claims is measured by individual claimant at a coverage level. Reported occurrences that do not result in a liability are included as reported claims. During 2021, we implemented additional processes to consolidate multiple data sources for U.S. Operations reserving. As part of that process, the level of detail used to determine the number of reported claims for some of the business units in US Operations changed. As a result, the cumulative number of reported claims for each accident year presented above as of December 31, 2021 is not comparable to the cumulative number of reported claims disclosed in previously issued financial statements. Reporting Segment: U.S. Operations Line of Business: Professional (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 27.8 $ 28.3 $ 28.6 $ 25.8 $ 24.0 $ 24.5 $ 24.9 $ 24.7 $ 24.4 $ 24.3 2013 20.9 21.5 21.1 19.0 19.8 19.5 18.3 18.1 18.0 2014 22.4 22.4 26.0 33.7 36.2 35.4 35.1 34.4 2015 29.9 29.5 33.2 34.0 37.1 37.9 38.3 2016 44.2 44.8 45.1 42.9 35.5 43.0 2017 60.1 61.8 78.3 87.9 99.5 2018 70.8 73.2 79.2 94.8 2019 94.4 96.8 105.0 2020 152.6 142.6 2021 177.9 Total 777.8 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 2.3 $ 8.6 $ 16.9 $ 19.9 $ 21.4 $ 22.6 $ 23.5 $ 24.2 $ 24.0 $ 24.3 2013 1.9 6.3 10.9 14.2 17.6 17.5 17.9 17.9 17.9 2014 2.3 5.4 15.1 24.1 25.5 32.3 33.3 33.6 2015 1.8 8.3 15.6 20.8 26.2 31.3 31.7 2016 2.4 11.9 24.6 28.9 30.8 34.4 2017 3.5 24.9 38.0 59.7 77.9 2018 4.5 16.7 43.8 62.6 2019 4.9 32.9 50.0 2020 13.3 36.4 2021 12.1 Total $ 380.9 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance 14.4 Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 411.3 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 24.3 $ 0.1 642 2013 18.0 0.1 625 2014 34.4 0.1 1,044 2015 38.3 2.2 1,831 2016 43.0 (0.1) 3,256 2017 99.5 4.2 3,759 2018 94.8 (0.5) 4,303 2019 105.0 22.5 5,091 2020 142.6 78.7 5,389 2021 177.9 149.2 5,208 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. (2) During 2021, the Company revised the manner in which it measures reported claims. The cumulative number of reported claims is measured by individual claimant at a coverage level. Reported occurrences that do not result in a liability are included as reported claims. During 2021, we implemented additional processes to consolidate multiple data sources for U.S. Operations reserving. As part of that process, the level of detail used to determine the number of reported claims for some of the business units in US Operations changed. As a result, the cumulative number of reported claims for each accident year presented above as of December 31, 2021 is not comparable to the cumulative number of reported claims disclosed in previously issued financial statements. Reporting Segment: U.S. Operations Line of Business: Property (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 103.8 $ 101.8 $ 98.7 $ 98.8 $ 98.5 $ 98.7 $ 98.7 $ 98.6 $ 98.6 $ 97.4 2013 74.5 79.9 78.7 78.2 77.8 78.2 78.4 78.2 77.2 2014 80.4 82.2 77.0 77.1 76.9 76.9 76.1 76.0 2015 74.0 73.4 69.9 68.9 69.1 69.2 69.2 2016 59.4 57.6 57.1 56.6 56.6 56.5 2017 75.2 79.6 86.9 94.9 94.5 2018 89.2 93.1 95.1 96.9 2019 91.4 88.8 98.4 2020 129.5 133.2 2021 111.7 Total $ 911.0 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 70.1 $ 97.2 $ 98.0 $ 98.2 $ 98.4 $ 98.4 $ 98.7 $ 98.6 $ 98.6 $ 97.4 2013 52.5 73.2 75.5 77.4 77.1 75.9 78.1 78.2 77.2 2014 51.6 73.1 75.7 76.4 76.3 76.4 76.1 76.0 2015 44.6 67.6 68.6 67.9 68.3 68.5 69.0 2016 39.4 55.2 55.8 56.1 56.4 56.3 2017 54.4 95.3 113.9 100.8 88.4 2018 61.3 126.7 107.0 98.8 2019 55.8 82.4 90.9 2020 75.9 116.6 2021 71.3 Total 841.9 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance (0.3) Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 68.8 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 97.4 $ 6.3 15,005 2013 77.2 0.9 10,717 2014 76.0 0.5 8,559 2015 69.2 0.8 7,746 2016 56.5 2.0 7,999 2017 94.5 — 10,388 2018 96.9 (12.9) 11,145 2019 98.4 2.1 11,724 2020 133.2 (9.3) 11,504 2021 111.7 (0.6) 9,265 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. (2) During 2021, the Company revised the manner in which it measures reported claims. The cumulative number of reported claims is measured by individual claimant at a coverage level. Reported occurrences that do not result in a liability are included as reported claims. During 2021, we implemented additional processes to consolidate multiple data sources for U.S. Operations reserving. As part of that process, the level of detail used to determine the number of reported claims for some of the business units in US Operations changed. As a result, the cumulative number of reported claims for each accident year presented above as of December 31, 2021 is not comparable to the cumulative number of reported claims disclosed in previously issued financial statements. Reporting Segment: U.S. Operations Line of Business: Specialty (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 7.5 $ 6.7 $ 4.9 $ 4.3 $ 4.0 $ 3.9 $ 3.5 $ 3.6 $ 3.3 $ 3.3 2013 10.0 8.6 4.6 2.5 1.7 0.9 0.9 0.9 0.9 2014 13.1 13.1 8.9 6.0 4.8 4.6 4.6 4.1 2015 14.8 14.3 9.5 5.5 1.2 0.5 0.3 2016 15.0 15.0 11.2 6.2 4.7 3.3 2017 16.2 16.2 7.6 0.9 0.7 2018 20.9 17.4 3.3 3.5 2019 22.7 8.5 5.6 2020 25.4 10.3 2021 27.9 Total $ 59.9 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 3.6 $ 3.3 $ 3.3 $ 3.3 $ 3.3 $ 3.4 $ 3.3 $ 3.4 $ 3.4 $ 3.4 2013 0.4 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 2014 1.1 3.3 4.0 4.0 4.1 4.1 4.0 4.1 2015 0.2 0.1 0.2 0.3 0.3 0.3 0.3 2016 1.3 1.6 2.2 2.2 2.2 2.8 2017 0.3 0.1 — 0.1 0.2 2018 — 0.7 1.7 1.2 2019 0.7 0.7 3.2 2020 0.3 7.6 2021 0.3 Total 24.0 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance 0.6 Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 36.5 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 3.3 $ — 121 2013 0.9 0.1 47 2014 4.1 — 45 2015 0.3 — 24 2016 3.3 0.9 56 2017 0.7 1.0 106 2018 3.5 2.6 142 2019 5.6 0.6 233 2020 10.3 2.3 409 2021 27.9 26.5 427 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. (2) During 2021, the Company revised the manner in which it measures reported claims. The cumulative number of reported claims is measured by individual claimant at a coverage level. Reported occurrences that do not result in a liability are included as reported claims. During 2021, we implemented additional processes to consolidate multiple data sources for U.S. Operations reserving. As part of that process, the level of detail used to determine the number of reported claims for some of the business units in US Operations changed. As a result, the cumulative number of reported claims for each accident year presented above as of December 31, 2021 is not comparable to the cumulative number of reported claims disclosed in previously issued financial statements. Reporting Segment: International Operations Operating Division: Argo Insurance Bermuda Line of Business: Liability (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 7.4 $ 7.4 $ 7.4 $ 5.6 $ 4.4 $ 1.7 $ — $ 0.6 $ 0.6 $ 0.6 2013 8.5 8.5 8.5 8.5 4.9 2.2 5.3 5.3 6.0 2014 9.8 9.8 9.8 6.2 1.5 2.3 2.3 1.6 2015 11.3 14.3 24.8 35.4 45.4 45.1 51.3 2016 13.9 14.0 14.0 6.6 6.1 0.8 2017 17.1 17.3 26.9 30.3 37.3 2018 8.9 32.1 26.6 24.2 2019 13.3 13.6 13.8 2020 23.3 24.9 2021 12.3 Total $ 172.8 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — 2.3 2.3 2.3 2.4 2.4 2014 — — 0.1 0.1 1.2 1.2 1.4 1.4 2015 — — 16.1 20.3 26.6 34.8 38.9 2016 — — — 0.1 0.1 0.2 2017 — 3.3 3.4 18.0 19.7 2018 — 13.8 18.3 18.5 2019 — 0.1 0.7 2020 0.8 7.0 2021 — Total $ 88.8 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance — Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 84.0 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 0.6 $ 0

Run-off Lines

Run-off Lines	12 Months Ended
	Dec. 31, 2021
Discontinued Operations and Disposal Groups [Abstract]
Run-off Lines	Run-off Lines We have discontinued active underwriting of certain lines of business, including those lines that were previously recorded in Argo Group’s risk-management segment. All current activity within these lines is related to the management of claims and other administrative functions. Also included in Run-off Lines are other liability reserves, which include exposure to claims for asbestos and environmental liabilities written in past years. The other liability reserves are often characterized by long elapsed periods between the occurrence of a claim and ultimate payment to resolve the claim. We use a specialized staff dedicated to administer and settle these claims. The following table presents our gross reserves for Run-off Lines as of December 31: December 31, (in millions) 2021 2020 Asbestos and Environmental: Reinsurance assumed $ 29.6 $ 29.4 Other 34.2 29.9 Total Asbestos and Environmental 63.8 59.3 Risk-management 162.6 162.4 Run-off reinsurance lines 0.5 0.5 Other run-off lines 34.3 14.3 Gross reserves - Run-off Lines $ 261.2 $ 236.5 We have received asbestos and environmental liability claims arising from other liability coverage primarily written in the 1960s, 1970s and into the early 1980s. Asbestos and environmental claims originate from policies directly underwritten by us and from reinsurance assumed during this period, including a portion assumed from the London market. Reserves for other run-off lines relate to other liability coverage primarily written in the 1970’s, with recent claim activity relating to abuse claims. The following table represents the total gross reserves for our asbestos exposure: December 31, (in millions) 2021 2020 2019 Direct written Case reserves $ 3.0 $ 3.1 $ 2.7 Unallocated loss adjustment expense ("ULAE") 0.5 0.5 0.5 Incurred but not reported ("IBNR") 19.9 20.2 16.1 Total direct written reserves 23.4 23.8 19.3 Assumed domestic Case reserves 7.4 8.4 9.1 ULAE 0.8 0.8 0.8 IBNR 11.9 12.8 11.2 Total assumed domestic reserves 20.1 22.0 21.1 Assumed London Case reserves 2.1 1.4 1.3 IBNR 2.3 1.6 1.1 Total assumed London reserves 4.4 3.0 2.4 Total asbestos reserves $ 47.9 $ 48.8 $ 42.8 The following table presents our underwriting losses for Run-off Lines: For the Years Ended December 31, (in millions) 2021 2020 2019 Asbestos and Environmental: Reinsurance assumed $ (4.7) $ (5.7) $ (4.4) Other (10.0) (11.7) (3.9) Total Asbestos and Environmental (14.7) (17.4) (8.3) Risk-management (9.9) 7.6 (4.9) Run-off reinsurance lines — 0.4 0.7 Other run-off lines (20.1) (3.4) (1.7) Total underwriting loss - Run-off Lines $ (44.7) $ (12.8) $ (14.2) Reserves for asbestos and environmental claims cannot be estimated with traditional loss reserving techniques that rely on historical accident year loss development factors. The uncertainty in the asbestos and environmental reserves estimates arises from several factors including lack of actuarially credible historical data, inapplicability of standard actuarial projection techniques, uncertainty with regards to claim costs, coverage interpretations and judicial, statutory and regulatory provisions under which the claims may be ultimately resolved. It is impossible to predict how the courts will interpret coverage issues and these resolutions may have a material impact on the ultimate resolution of the asbestos and environmental liabilities. We use a variety of estimation methods to calculate reserves as a whole; however, reserves for asbestos and environmental claims were determined using a variety of methods which rely on historical claim reporting and average claim cost information. We apply greatest weight to the method that projects future calendar period claims and average claim costs because it best captures the unique claim characteristics of our underlying exposures. Although management has recorded its best estimate of loss reserves, due to the uncertainties of estimation of liability that may arise as discussed herein, further deterioration of claims could occur in the future.

Long-term Debt

Long-term Debt	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Long-term Debt	Long-term Debt Senior Unsecured Fixed Rate Notes In September 2012, Argo Group (the “Parent Guarantor”), through its subsidiary Argo Group U.S. (the “Subsidiary Issuer”), issued $143,750,000 aggregate principal amount of the Subsidiary Issuer’s 6.5% Senior Notes due September 15, 2042 (the “Notes”). The Notes are unsecured and unsubordinated obligations of the Subsidiary Issuer and rank equally in right of payment with all of the Subsidiary Issuer’s other unsecured and unsubordinated debt. The Notes are guaranteed on a full and unconditional senior unsecured basis by the Parent Guarantor. The Notes may be redeemed, for cash, in whole or in part, on or after September 15, 2017, at the Subsidiary Issuer’s option, at any time and from time to time, prior to maturity at a redemption price equal to 100% of the principal amount of the Notes to be redeemed, plus accrued but unpaid interest on the principal amount being redeemed to, but not including, the redemption date. In accordance with ASU 2015-3, “Simplifying the Presentation of Debt Issuance Costs” (Topic 835), we present the unamortized debt issuance costs in the balance sheet as a direct deduction from the carrying value of the debt liability. At December 31, 2021 and 2020, the Notes consisted of the following: (in millions) December 31, 2021 December 31, 2020 Senior unsecured fixed rate notes Principal $ 143.8 $ 143.8 Less: unamortized debt issuance costs (3.5) (3.6) Senior unsecured fixed rate notes, less unamortized debt issuance costs $ 140.3 $ 140.2 Junior Subordinated Debentures Through a series of trusts, that are wholly-owned subsidiaries (non-consolidated), we issued debt. The debentures are variable with the rate being reset quarterly and subject to certain interest rate ceilings. Interest payments are payable quarterly. The debentures are all unsecured and are subordinated to other indebtedness. At December 31, 2021 and 2020, all debentures were eligible for redemption subject to certain terms and conditions at a price equal to 100% of the principal plus accrued and unpaid interest. A summary of our outstanding junior subordinated debentures is presented below: December 31, 2021 (in millions) Issue Date Trust Preferred Pools Maturity Rate Structure Interest Rate at December 31, 2021 Amount Argo Group 5/15/2003 PXRE Capital Statutory Trust II 5/15/2033 3M LIBOR + 4.10% 4.26% $ 18.0 11/6/2003 PXRE Capital Trust VI 9/30/2033 3M LIBOR + 3.90% 4.12% 10.3 Argo Group US 5/15/2003 Argonaut Group Statutory Trust I 5/15/2033 3M LIBOR + 4.10% 4.26% 15.5 12/16/2003 Argonaut Group Statutory Trust III 1/8/2034 3M LIBOR + 4.10% 4.22% 12.3 4/29/2004 Argonaut Group Statutory Trust IV 4/29/2034 3M LIBOR + 3.85% 4.00% 13.4 5/26/2004 Argonaut Group Statutory Trust V 5/24/2034 3M LIBOR + 3.85% 4.02% 12.4 5/12/2004 Argonaut Group Statutory Trust VI 6/17/2034 3M LIBOR + 3.80% 4.02% 13.4 9/17/2004 Argonaut Group Statutory Trust VII 12/15/2034 3M LIBOR + 3.60% 3.80% 15.5 9/22/2004 Argonaut Group Statutory Trust VIII 9/22/2034 3M LIBOR + 3.55% 3.76% 15.5 10/22/2004 Argonaut Group Statutory Trust IX 12/15/2034 3M LIBOR + 3.60% 3.80% 15.5 9/14/2005 Argonaut Group Statutory Trust X 9/15/2035 3M LIBOR + 3.40% 3.60% 30.9 Total Outstanding $ 172.7 December 31, 2020 (in millions) Issue Date Trust Preferred Pools Maturity Rate Structure Interest Rate at December 31, 2020 Amount Argo Group 5/15/2003 PXRE Capital Statutory Trust II 5/15/2033 3M LIBOR + 4.10% 4.32% $ 18.0 11/6/2003 PXRE Capital Trust VI 9/30/2033 3M LIBOR + 3.90% 4.15% 10.3 Argo Group US 5/15/2003 Argonaut Group Statutory Trust I 5/15/2033 3M LIBOR + 4.10% 4.32% 15.5 12/16/2003 Argonaut Group Statutory Trust III 1/8/2034 3M LIBOR + 4.10% 4.34% 12.3 4/29/2004 Argonaut Group Statutory Trust IV 4/29/2034 3M LIBOR + 3.85% 4.07% 13.4 5/26/2004 Argonaut Group Statutory Trust V 5/24/2034 3M LIBOR + 3.85% 4.05% 12.4 5/12/2004 Argonaut Group Statutory Trust VI 6/17/2034 3M LIBOR + 3.80% 4.03% 13.4 9/17/2004 Argonaut Group Statutory Trust VII 12/15/2034 3M LIBOR + 3.60% 3.82% 15.5 9/22/2004 Argonaut Group Statutory Trust VIII 9/22/2034 3M LIBOR + 3.55% 3.79% 15.5 10/22/2004 Argonaut Group Statutory Trust IX 12/15/2034 3M LIBOR + 3.60% 3.82% 15.5 9/14/2005 Argonaut Group Statutory Trust X 9/15/2035 3M LIBOR + 3.40% 3.62% 30.9 Total Outstanding $ 172.7 Junior Subordinated Debentures from Maybrooke Acquisition Unsecured junior subordinated debentures with a principal balance of $91.8 million were assumed through the acquisition of Maybrooke (“the acquired debt”). The acquired debt is carried on our consolidated balance sheet at $85.5 million, which represents the debt’s fair value at the date of acquisition plus accumulated accretion of discount to par value, as required by accounting for business combinations under ASC 805. At December 31, 2021, the acquired debt was eligible for redemption at par. Interest accrues on the acquired debt based on a variable rate, which is reset quarterly. Interest payments are payable quarterly. A summary of the terms of the acquired debt outstanding is presented below: (in millions) Issue Date Maturity Rate Structure Interest Rate at December 31, 2021 Principal at December 31, 2021 Carrying Value at December 31, 2021 9/13/2007 9/15/2037 3 month LIBOR + 3.15% 3.35 % $ 91.8 $ 85.5 (in millions) Issue Date Maturity Rate Structure Interest Rate at December 31, 2020 Principal at December 31, 2020 Carrying Value at December 31, 2020 9/13/2007 9/15/2037 3 month LIBOR + 3.15% 3.37 % $ 91.8 $ 85.1 Other Indebtedness Our consolidated balance sheets include various long-term debt instruments under the caption “other indebtedness,” as detailed in the table below. Information regarding the terms and principal amounts of each of these debt instruments is also provided. (in millions) December 31, Debt Type 2021 2020 Floating rate loan stock $ 57.0 $ 60.7 Total other indebtedness $ 57.0 $ 60.7 Floating Rate Loan Stock Certain unsecured, unsubordinated debt was assumed through the acquisition of Argo Underwriting Agency, Ltd. At December 31, 2021 and 2020, all notes were eligible for redemption subject to certain terms and conditions at a price equal to 100% of the principal plus accrued and unpaid interest. Interest on the U.S. dollar and euro notes is due semiannually and quarterly, respectively. A summary of the notes outstanding at December 31, 2021 and 2020 is presented below: (in millions) Currency Issue Date Maturity Rate Structure Interest Rate at December 31, 2021 Amount U.S. Dollar 12/8/2004 11/15/2034 6 month LIBOR + 4.2% 4.35% $ 6.5 U.S. Dollar 10/31/2006 1/15/2036 6 month LIBOR + 4.0% 4.15% 10.0 Total U.S. Dollar notes 16.5 Euro 9/6/2005 8/22/2035 3 month Euribor + 4.0% 3.44% 13.5 Euro 10/31/2006 11/22/2036 3 month Euribor + 4.0% 3.44% 11.8 Euro 6/8/2007 9/15/2037 3 month Euribor + 3.9% 3.30% 15.2 Total Euro notes 40.5 Total notes outstanding $ 57.0 (in millions) Currency Issue Date Maturity Rate Structure Interest Rate at December 31, 2020 Amount U.S. Dollar 12/8/2004 11/15/2034 6 month LIBOR + 4.2% 4.54% $ 6.5 U.S. Dollar 10/31/2006 1/15/2036 6 month LIBOR + 4.0% 4.34% 10.0 Total U.S. Dollar notes 16.5 Euro 9/6/2005 8/22/2035 3 month Euribor + 4.0% 3.47% 14.7 Euro 10/31/2006 11/22/2036 3 month Euribor + 4.0% 3.47% 12.9 Euro 6/8/2007 9/15/2037 3 month Euribor + 3.9% 3.36% 16.6 Total Euro notes 44.2 Total notes outstanding $ 60.7 No principal payments have been made since the acquisition of Argo Underwriting Agency, Ltd. The floating rate loan stock denominated in euros fluctuates due to foreign currency translation. The outstanding balance on these loans was $40.5 million and $44.2 million as of December 31, 2021 and 2020, respectively. The foreign currency translation adjustment is recorded in our consolidated statements of income (loss). The following table presents interest and maturities of long-term debt as of December 31, 2021: For the Years Ended (in millions) Total 2022 2023 2024 2025 2026 Thereafter Long-term debt: Junior subordinated debentures (1) 421.4 10.4 11.3 11.8 11.8 11.8 364.3 Senior unsecured fixed rate notes (2) 335.4 9.3 9.4 9.3 9.4 9.3 288.7 Floating rate loan stock (3) 88.6 2.1 2.2 2.2 2.2 2.2 77.7 (1) Interest only on Junior Subordinated Debentures through 2037. Interest calculated based on interest rate forecast. Principal due beginning May 2033. (2) Interest only on Senior Unsecured Fixed Rate Notes through 2042. Interest calculated based on the fixed rate of the notes. Principal due September 2042. (3) Interest only on Floating Rate Loan Stock through 2034. Interest calculated based on interest rate forecast. Principal due beginning November 2034. Borrowing Under Revolving Credit Facility On November 2, 2018, each of Argo Group, Argo Group U.S., Inc., Argo International Holdings Limited, and Argo Underwriting Agency Limited (the “Borrowers”) entered into a new $325 million credit agreement (the “Credit Agreement”) with JPMorgan Chase Bank, N.A., as administrative agent. The Credit Agreement includes a one-time borrowing of $125 million for a term loan (the “Term Loan”), and a $200 million revolving credit facility. The Company used most of the net proceeds from the Preferred Stock Offering (as defined in Note 11 “Shareholders’ Equity”) to pay off the Term Loan in September 2020. The Credit Agreement matures on November 2, 2023. Borrowings under the Credit Agreement may be used for general corporate purposes, including working capital, permitted acquisitions and letters of credit, and each of the Borrowers has agreed to be jointly and severally liable for the obligations of the other Borrowers under the Credit Agreement. The Credit Agreement contains customary events of default. If an event of default occurs and is continuing, the Borrowers could be required to immediately repay all amounts outstanding under the Credit Agreement. Lenders holding at least a majority of the loans and commitments under the Credit Agreement could elect to accelerate the maturity of the loans and/or terminate the commitments under the Credit Agreement upon the occurrence and during the continuation of an event of default. Included in the Credit Agreement is a provision that allows up to $200.0 million of the revolving credit facility to be used for letters of credit (“LOCs”), subject to availability. At December 31, 2021 and 2020, there were $40.3 million and $70.5 million of LOCs, respectively, issued against the Credit Facility. Letter of Credit Facilities Argo Re may be required to secure its obligations under various reinsurance contracts in certain circumstances. In order satisfy these requirements, Argo Re has entered into one committed and two uncommitted secured bilateral LOC facilities with commercial banks and generally uses these facilities to issue LOCs in support of non-admitted reinsurance obligations in the U.S. and other jurisdictions. The committed LOC facility has a term of one year and includes customary conditions and event of default provisions. Issuance of LOCs using the uncommitted LOC facilities is at the discretion of the lenders. The availability of letters of credit under these secured facilities are subject to a borrowing base requirement, determined on the basis of specified percentages of the market value of eligible categories of securities pledged to the lender. On December 31, 2021, committed and uncommitted letter of credit facilities totaled $205 million. In addition to the bilateral, secured letters of credit facilities described above, Argo Re can use other forms of collateral to secure these reinsurance obligations including trust accounts, cash deposits, LOCs issued by commercial banks on an uncommitted basis and the Credit Agreement. On December 31, 2021, LOCs totaling $167.4 million were outstanding, of which $59.2 million were issued against the committed, secured bilateral LOC facility and $108.2 million were issued by commercial banks against the uncommitted, secured bilateral LOC facilities, and $0.26 million issued by commercial bank against uncommitted, secured bilateral LOC facility. Collateral with a market value of $193.9 million was pledged to these banks as security against these LOCs. In November 2021, Argo Group executed a LOC facility with a commercial bank to issue LOCs in favor of Lloyd’s to support its Funds at Lloyd’s requirements. This facility has an initial term of one year, and is unsecured, renewable and includes customary conditions and event of default provisions. At December 31, 2021, a LOC in the amount of £26 million ($35.1 million) was issued in favor of Lloyd’s, which allowed the Company to reduce its other collateral pledged to Lloyd’s by a comparable amount. Other Debt Argo Group also has entered into agreements with commercial banks to issue unsecured LOCs that support its insurance and general operations. LOCs in the amount of $5.0 million and $3.9 million were outstanding as of December 31, 2021 and December 31, 2020, respectively.

Disclosures about Fair Value of

Disclosures about Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 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 December 31, 2021 and 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 December 31, 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: December 31, 2021 2020 (in millions) Carrying Fair Carrying Fair Junior subordinated debentures: Trust preferred debentures $ 172.7 $ 172.9 $ 172.7 $ 173.6 Subordinated debentures 85.5 91.9 85.1 92.3 Total junior subordinated debentures 258.2 264.8 257.8 265.9 Senior unsecured fixed rate notes 140.3 148.4 140.2 146.7 Floating rate loan stock 57.0 57.1 60.7 61.0 Based on an analysis of the inputs, our financial instruments measured at fair value on a recurring basis have been categorized as follows: Fair Value Measurements at Reporting Date Using (in millions) December 31, 2021 Level 1 (a) Level 2 (b) Level 3 (c) Junior subordinated debentures: Trust preferred debentures $ 172.9 $ — $ 172.9 $ — Subordinated debentures 91.9 — 91.9 — Total junior subordinated debentures 264.8 — 264.8 — Senior unsecured fixed rate notes 148.4 148.4 — — Floating rate loan stock 57.1 — 57.1 — 470.3 148.4 321.9 — (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) Junior subordinated debentures: Trust preferred debentures $ 173.6 $ — $ 173.6 $ — Subordinated debentures 92.3 — 92.3 — Total junior subordinated debentures 265.9 — 265.9 — Senior unsecured fixed rate notes 146.7 146.7 — — Floating rate loan stock 61.0 — 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

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Shareholders' Equity	Shareholders’ Equity Preferred Stock At December 31, 2021, we have issued and outstanding 6,000 shares of our Series A Preference Shares (equivalent to 6,000,000 depositary shares, each representing a 1/1,000th interest in a Series A Preference Share) with a $25,000 liquidation preference per share (equivalent to $25 per depositary share) (the “Preferred Stock Offering”). Dividends to the holders of the Series A Preference Shares will be payable on a non-cumulative basis only when, as and if declared by our Board of Directors or a duly authorized committee thereof, quarterly in arrears on the 15th of March, June, September, and December of each year, commencing on September 15, 2020, at a rate equal to 7.00% of the liquidation preference per annum (equivalent to $1,750 per Series A Preference Share and $1.75 per depositary share per annum) up to but excluding September 15, 2025. Beginning on September 15, 2025, any such dividends will be payable on a non-cumulative basis, only when, as and if declared by our Board of Directors or a duly authorized committee thereof, during each reset period, at a rate per annum equal to the Five-Year U.S. Treasury Rate as of the most recent reset dividend determination date (as described in the Company’s prospectus supplement dated July 7, 2020) plus 6.712% of the liquidation preference per annum. So long as any Series A Preference Shares remain outstanding, unless dividends on all outstanding Series A Preference Shares payable on a dividend payment date have been declared and paid or provided for in full, (1) no dividend shall be paid or declared on our common shares or any other junior shares or any parity shares, other than a dividend payable solely in our common shares, other junior shares or (solely in the case of parity shares) other parity shares, as applicable, and (2) no common shares, other junior shares or parity shares shall be purchased, redeemed or otherwise acquired for consideration by us, directly or indirectly (other than (i) as a result of a reclassification of junior shares for or into other junior shares, or a reclassification of parity shares for or into other parity shares, or the exchange or conversion of one junior share for or into another junior share or the exchange or conversion of one parity share for or into another parity share, (ii) through the use of the proceeds of a substantially contemporaneous sale of junior shares or (solely in the case of parity shares) other parity shares, as applicable, or (iii) as required by or necessary to fulfill the terms of any employment contract, benefit plan or similar arrangement with or for the benefit of one or more employees, directors or consultants), in each case, during the following dividend period. Upon any voluntary or involuntary liquidation, dissolution or winding-up of Argo Group holders of the Series A Preference Shares are entitled to receive out of our assets available for distribution to shareholders, before any distribution is made to holders of our common shares or other junior shares, a liquidating distribution in the amount of $25,000 per Series A Preference Share (equivalent to $25 per depositary share) plus the amount of declared and unpaid dividends, if any, to the date fixed for distribution, without interest on such unpaid dividends. Distributions will be made pro rata in accordance with the respective aggregate liquidation preferences of the Series A Preference Shares and any parity shares, and only to the extent of our assets, if any, that are available after satisfaction of all liabilities to creditors. Neither the depositary shares nor the underlying Series A Preference Shares will be convertible into, or exchangeable for, shares of any other class or series of stock or other securities of Argo Group or our subsidiaries. Neither the depositary shares nor the underlying Series A Preference Shares have a stated maturity or will be subject to any sinking fund, retirement fund, or purchase fund or other obligation of ours to redeem, repurchase or retire the depositary shares or the Series A Preference Shares. We may redeem the Series A Preference Shares at our option, in whole or in part, from time to time, on or after September 15, 2025, at a redemption price equal to $25,000 per share (equivalent to $25 per depositary share), plus the amount of declared and unpaid dividends, if any, without interest on such unpaid dividends. In addition, we may redeem the Series A Preference Shares in specified circumstances relating to certain corporate, regulatory, rating agency or tax events; provided that no such redemption may occur prior to September 15, 2025 unless one of the redemption requirements is satisfied. The depositary shares will be redeemed only if and to the extent the related Series A Preference Shares are redeemed by us. The Series A Preference Shares will not have voting rights, except under limited circumstances. During 2021, our Board declared quarterly cash dividends totaling $1,750.000 on each share of our Series A Preference Shares, or $1.75000 per depositary share, outstanding to our shareholders of record. For the year ended December 31, 2021, we paid cash dividends totaling $10.5 million to our preferred shareholders. We are authorized to issue 30 million shares of $1.00 par value preferred shares. As of December 31, 2021 and 2020, 6,000 preferred shares were issued and outstanding. Common Stock During 2021, our Board declared quarterly cash dividends totaling $1.24 on each share of common stock outstanding to our shareholders of record. For the year ended December 31, 2021, we paid cash dividends totaling $43.9 million to our common shareholders. During 2020, our Board declared quarterly cash dividends totaling $1.24 on each share of common stock outstanding. For the year ended December 31, 2020, we paid cash dividends totaling $43.0 million to our shareholders. During 2019, our Board declared quarterly cash dividends totaling $1.24 on each share of common stock outstanding. For the year ended December 31, 2019, we paid cash dividends totaling $43.1 million to our shareholders. On May 3, 2016, our Board authorized the repurchase of up to $150.0 million of our common shares (“2016 Repurchase Authorization”). The 2016 Repurchase Authorization supersedes all the previous Repurchase Authorizations. As of December 31, 2021, availability under the 2016 Repurchase Authorization for future repurchases of our common shares was $53.3 million. For the years ended December 31, 2021 and 2020, we did not repurchase any common shares. The repurchase of common stock is also subject to the terms of our Series A Preference Shares, pursuant to which we may not (other than in limited circumstances) purchase, redeem or otherwise acquire our common stock unless the full dividends for the latest completed dividend period on all outstanding shares of our Series A Preferred Stock have been declared and paid or provided for.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) A summary of changes in accumulated other comprehensive income (loss), net of taxes (where applicable) by component for the year ended December 31, 2021 and 2020 is presented below: (in millions) Foreign Currency Translation Adjustments Unrealized Defined Benefit Pension Plans Total Balance, January 1, 2020 $ (22.6) $ 33.5 $ (8.1) $ 2.8 Other comprehensive income (loss) before reclassifications (15.3) 78.7 (0.5) 62.9 Amounts reclassified from accumulated other comprehensive loss — (12.8) — (12.8) Net current-period other comprehensive income (loss) (15.3) 65.9 (0.5) 50.1 Cumulative effect of adoption of ASU 2016-13 — 5.7 — 5.7 Balance, December 31, 2020 (37.9) 105.1 (8.6) 58.6 Other comprehensive (loss) income before reclassifications 2.6 (77.4) 1.5 (73.3) Amounts reclassified from accumulated other comprehensive income — (8.0) — (8.0) Net current-period other comprehensive (loss) income 2.6 (85.4) 1.5 (81.3) Balance, December 31, 2021 $ (35.3) $ 19.7 $ (7.1) $ (22.7) The amounts reclassified from accumulated other comprehensive (loss) income shown in the above table have been included in the following captions in our Consolidated Statements of Income (Loss): For the Years Ended December 31, (in millions) 2021 2020 2019 Unrealized gains and losses on securities: Net realized investment losses (gains) $ (12.2) $ (12.8) $ 9.9 (Benefit) provision for income taxes 4.2 — (1.2) Net of taxes $ (8.0) $ (12.8) $ 8.7

Net (Loss) Income Per Common Sh

Net (Loss) Income Per Common Share	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net (Loss) Income Per Common Share	Net (Loss) Income Per Common Share The following table presents the calculation of net (loss) income per common share on a basic and diluted basis: For the Years Ended December 31, (in millions, except number of shares and per share amounts) 2021 2020 2019 Net income (loss) $ 6.7 $ (54.1) $ (14.1) Less: Preferred share dividends 10.5 4.6 — Net loss attributable to common shareholders (3.8) (58.7) (14.1) Weighted average common shares outstanding - basic 34,816,160 34,614,813 34,205,954 Effect of dilutive securities: Equity compensation awards — — — Weighted average common shares outstanding - diluted 34,816,160 34,614,813 34,205,954 Net income (loss) per common share: Basic $ (0.11) $ (1.70) $ (0.41) Diluted $ (0.11) $ (1.70) $ (0.41)

Share-based Compensation

Share-based Compensation	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Share-based Compensation	Share-based Compensation The fair value method of accounting is used for share-based compensation plans. Under the fair value method, compensation cost is measured based on the fair value of the award at the measurement date and recognized over the requisite service period, less estimated forfeiture. We estimate forfeitures based on historical forfeitures patterns, thereby recognizing expense only for those awards that are expected to vest. The estimate of forfeitures is adjusted as actual forfeitures differ from our estimate, resulting in recognition of compensation expense only for those awards that actually vest. The compensation expense recognized under all our share-based payment plans was $8.0 million ($6.9 million, net of tax), $8.7 million ($7.8 million, net of tax) and $16.9 million ($15.5 million, net of tax) for the years ended December 31, 2021, 2020 and 2019, respectively. The compensation expense is included in “Underwriting, acquisition and insurance expenses” in our Consolidated Statements of Income (Loss). We present all tax benefits resulting from the exercise of stock options and vesting of non-vested shares as cash flows from operating activities. Excess tax benefits are realized tax benefits from tax deductions for exercised options and vested shares in excess of the deferred tax asset attributable to stock compensation costs for such options. Such tax benefits and cash flows were immaterial for all reporting periods. 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 the Board of Directors. The 2019 Plan authorizes 1,885,000 shares of common stock 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 or 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 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. 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 A summary of non-vested performance share activity as of December 31, 2021 and changes during the year then ended is as follows: Shares Weighted-Average Outstanding at January 1, 2021 157,847 $ 43.10 Granted 100,291 $ 54.79 Vested and issued (8,987) $ 44.49 Expired or forfeited (48,587) $ 48.74 Outstanding at December 31, 2021 200,564 $ 47.52 As of December 31, 2021, there was $4.4 million of total unrecognized compensation cost related to performance share compensation arrangements granted by Argo Group. The weighted-average period over which this unrecognized expense is expected to be recognized is 1.7 years. The total fair value of shares vested during the year ended December 31, 2021 was $0.4 million. Restricted Shares A summary of restricted share activity as of December 31, 2021 and changes during the year then ended is as follows: Shares Weighted-Average Outstanding at January 1, 2021 370,027 $ 44.22 Granted 168,011 $ 55.12 Vested and issued (143,744) $ 46.08 Expired or forfeited (115,864) $ 44.88 Outstanding at December 31, 2021 278,430 $ 49.57 As of December 31, 2021, there was $9.6 million of total unrecognized compensation cost related to restricted share compensation arrangements granted by Argo Group. The weighted-average period over which this unrecognized expense is expected to be recognized is 2.4 years. The total fair value of shares vested during the year ended December 31, 2021 was $6.6 million. Stock-settled Share Appreciation Rights For the year ended December 31, 2021, 129,977 stock settled appreciation rights (“SARs”) were exercised, with an intrinsic value of $2.2 million. At December 31, 2021, 10,178 SARs remain issued and outstanding. No expense was recognized on the SARs for the year ended December 31, 2021 as all awards had previously been expensed. If not exercised, all remaining awards will expire during 2022. Employees Share Purchase Plans We have established an employee stock purchase plan for eligible employees (Argo Group’s 2007 Employee Share Purchase Plan). Under this plan, newly issued shares of our common stock may be purchased over an offering period of three months at 85% of the lower of the market value on the first day of the offering period or on the designated purchase date at the end of the offering period. We have also established a “Save As You Earn Plan” for our United Kingdom (“U.K.”) employees. Under this plan, newly issued shares of our common stock may be purchased over an offering period of three

Underwriting, Acquisition and I

Underwriting, Acquisition and Insurance Expenses	12 Months Ended
	Dec. 31, 2021
Underwriting Acquisition And Insurance Expenses [Abstract]
Underwriting, Acquisition and Insurance Expenses	Underwriting, Acquisition and Insurance Expenses Underwriting, Acquisition and Insurance Expenses Underwriting, acquisition and insurance expenses were as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Commissions $ 289.5 $ 268.0 $ 241.3 Other underwriting and insurance expenses 428.6 409.0 412.3 Total 718.1 677.0 653.6 Net deferral of policy acquisition costs (15.8) (9.3) 12.4 Total underwriting, acquisition and insurance expenses $ 702.3 $ 667.7 $ 666.0

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 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 ourselves to be engaged in a trade or business in the U.S. or the U.K. and, accordingly, do not expect to be subject to direct U.S. or U.K. income taxation. We have subsidiaries based in the U.K. that are subject to the tax laws of that country. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Certain U.K. subsidiaries are deemed to be engaged in business in the U.S., and therefore, are subject to U.S. corporate tax in respect of a proportion of their U.S. underwriting business only. Relief is available against the U.K. tax liabilities in respect of overseas taxes paid that arise from the underwriting business. Our U.K. subsidiaries file separate U.K. income tax returns. We have subsidiaries based in the U.S. that are subject to U.S. tax laws. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Our U.S. subsidiaries generally file a consolidated U.S. federal income tax return. We also have operations in Belgium, Brazil, 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. Subsequently, in the three months ended December 31, 2021 an additional increase of $0.9 million of net deferred tax assets were remeasured resulting in a cumulative deferred tax asset increase of $8.3 million for the period ending December 31, 2021. The following table presents the components of income tax provision (benefit) included in the amounts reported in our consolidated financial statements: For the Years Ended December 31, (in millions) 2021 2020 2019 Current income tax provision (benefit) related to: United States (Federal) $ 35.4 $ 28.0 $ 37.3 United States (State) $ 2.4 $ 1.4 $ 1.7 United Kingdom (2.2) (0.1) (1.5) Other jurisdictions 1.6 — (1) 0.1 Total current income tax provision 37.2 29.3 37.6 Deferred income tax provision (benefit) related to: United States (26.3) (5.1) (17.7) United Kingdom (12.3) (16.6) (5.8) Other jurisdictions — 0.1 — Total deferred income tax (benefit) (38.6) (21.6) (23.5) Income tax provision (benefit) $ (1.4) $ 7.7 $ 14.1 (1) Tax expense for the respective year was less than $0.1 million. Our expected income tax provision (benefit) 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 years ended December 31, 2021, 2020 and 2019, pre-tax income (loss) attributable to our operations and the operations’ effective tax rates were as follows: (in millions) 2021 2020 2019 Pre-Tax Effective Pre-Tax Effective Pre-Tax Effective Bermuda $ (18.0) — % $ (56.2) — % $ (34.7) — % United States 65.6 18.1 % 103.3 22.7 % 84.7 24.6 % United Kingdom (61.1) 24.4 % (100.6) 15.7 % (45.9) 14.9 % Barbados — (1) — % — (1) — % — (1) — % Belgium — — % 0.2 30.7 % — (1) 15.8 % Brazil 15.3 10.4 % 3.9 — % 5.2 — % United Arab Emirates 1.4 — % 2.1 — % 0.4 — % Ireland (0.2) — % 1.8 — % (0.1) — % Italy 1.4 — % 0.6 — % (7.4) — % Malta 0.9 — % (1.4) — % (2.0) — % Switzerland — (1) — % (0.1) — % (0.2) (0.2) % Pre-tax income (loss) $ 5.3 (26.4) % $ (46.4) (16.6) % $ — — % (2) (1) Pre-tax income for the respective year was less than $0.1 million. (2) Not meaningful. 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 inherent nature of our business. A reconciliation of the difference between the provision for income taxes and the expected tax provision (benefit) at the weighted average tax rate is as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Income tax provision (benefit) at expected rate $ 9.8 $ 4.0 $ 8.9 Tax effect of: Nontaxable investment income (0.5) (0.7) (1.2) Foreign exchange adjustments (0.7) 1.6 (0.1) Impairment of goodwill 8.2 1.0 2.9 Withholding taxes 0.1 0.1 0.2 Change in uncertain tax position liability (4.5) 0.7 1.4 Change in valuation allowance (0.7) 0.5 (1.8) Impact of change in tax rate related to Finance Act 2021 (8.3) — — Brazil Premiums and Underwriting (5.3) — — Other 0.5 0.5 3.8 Income tax provision (benefit) $ (1.4) $ 7.7 $ 14.1 The net deferred tax asset (liability) comprises the tax effects of temporary differences related to the following assets and liabilities: December 31, (in millions) 2021 2020 Deferred tax assets: Losses and loss adjustment expense reserve discounting $ 35.4 $ 29.2 Unearned premiums 27.0 25.9 Net operating loss carryforwards 31.6 27.9 Investment in limited partnership interests 21.1 7.8 Unrealized losses on equity securities 8.6 — Investments — 2.0 Right of use assets 13.5 12.7 Accrued bonus 5.8 6.3 Stock option expense 1.1 0.7 United Kingdom underwriting results 28.1 21.9 Other 10.6 9.6 Deferred tax assets, gross 182.8 144.0 Deferred tax liabilities: Unrealized gains on equity securities — (5.7) Unrealized gains on fixed maturities and other investment securities (4.8) (22.3) Unrealized gains on limited partnership interests (26.3) (14.7) Investments (5.1) — Depreciable fixed assets (7.9) (20.5) Deferred acquisition costs (21.3) (20.4) Lease liability (12.2) (11.7) TCJA reserve transitional liability (2.1) (2.7) Other (1.6) (0.7) Deferred tax liabilities, gross (81.3) (98.7) Deferred tax assets, net before valuation allowance $ 101.5 $ 45.3 Valuation allowance (27.9) (28.6) Deferred tax asset (liabilities), net $ 73.6 $ 16.7 Net deferred tax assets (liabilities) - Other jurisdictions $ 35.0 $ 21.4 Net deferred tax assets (liabilities) - United States 38.6 (4.7) Deferred tax asset (liabilities), net $ 73.6 $ 16.7 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. The valuation allowance for deferred tax assets decreased by $(0.7) million in 2021 and primarily related to the following: Internal Revenue Code Section 382 limited net operating loss carryforwards within the U.S., cumulative losses incurred since inception, and valuation allowances acquired through or related to acquisitions. Based upon a review of our available evidence our management concluded that it is more-likely-than-not that the deferred tax assets will be realized. For tax return purposes, as of December 31, 2021, we had NOL carryforwards in Brazil, Italy, Malta, United Kingdom, and the United States. The amount and timing of realizing the benefits of NOL carryforwards depend on future taxable income and limitations imposed by tax laws. Only a portion of the United States NOL carryforwards has been recognized as mentioned above in the consolidated financial statements and is included in net deferred tax assets. The NOL amounts by jurisdiction and year of expiration are as follows: (in millions) December 31, 2021 Expiration Net operating loss carryforwards by jurisdiction: Brazil 6.6 Indefinite Italy 48.4 Indefinite Malta 13.7 Indefinite United Kingdom 17.2 Indefinite United States 40.6 2025 - 2037 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. Included in the balances at December 31, 2021 and 2020 were $3.6 million and $8.2 million, respectively, of unrecognized tax benefits that, if recognized, would affect the annual effective tax rate. The Company believes it is reasonably possible th at $0.6 million of the total amount of uncertain tax benefits will decrease within the next 12 months as a result of a lapse of the statute of limitations or settlement with taxing authori ties. A net increase (decrease) of interest in the amount of $(1.0) million, $0.5 million, and $0.5 million has been recorded in the line item “Interest Expense” in our Consolidated Statements of Income (Loss) for the twelve months ended December 31, 2021, 2020, and 2019, respectively. A net increase (decrease) of penalty in the amount of $(0.8) million, $0.1 million, and $0.2 million has been recorded in the line item “Underwriting, acquisition and insurance expenses” in our Consolidated Statements of Income (Loss) for the twelve months ended December 31, 2021, 2020, and 2019, respectively. The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits for the years ended December 31, 2021 and 2020: (in millions) 2021 2020 Balance at January 1 $ 8.2 $ 7.5 Additions for tax positions of prior years $ — — Reductions for tax positions of prior years (0.3) — Additions based on tax positions related to current year $ — 0.7 Reductions based on tax positions related to current year — — Reductions based on settlements with taxing authorities (2.8) — Expiration of statute of limitations (1.5) — Balance at December 31 $ 3.6 $ 8.2 Our U.S. subsidiaries are no longer subject to U.S. federal and state income tax examinations by tax authorities for years before 2018. Our U.K. subsidiaries are no longer subject to U.K. income tax examinations by Her Majesty’s Revenue and Customs for years before 2019. As of December 31, 2021, our Texas Sales, Excise, and Use Tax returns for the periods January 1, 2017 through March 31, 2020 are under examination. At this time, the Company cannot reasonably estimate an assessment by the taxing authority. We do not expect the ultimate disposition of these audits to result in a material change in our financial position, results of operations, or liquidity. 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.

Pension Benefits and Savings Pl

Pension Benefits and Savings Plans	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Pension Benefits and Savings Plans	Pension Benefits and Savings Plans Argo Group U.S. sponsors a qualified defined benefit plan and non-qualified unfunded supplemental defined benefit plans, all of which were curtailed effective February 2004. As of December 31, 2021 and 2020, the qualified pension plan was underfunded by $2.6 million and $4.2 million, respectively. The non-qualified pension plans were unfunded by $1.8 million and $2.0 million at December 31, 2021 and 2020, respectively. Underfunded and unfunded amounts are included in “accrued underwriting expenses and other liabilities” in our consolidated balance sheets. Based on the current funding status of the pension plan, effects of the curtailment and expected changes in pension plan asset values and pension obligations, we do not believe any significant funding of the pension plan will be required during the year ending December 31, 2021. Net periodic benefit costs were $0.1 million for the years ended December 31, 2021 and 2020, and $0.3 million for the year ended December 31, 2019, respectively. Substantially all of our employees are either eligible or mandated by applicable laws to participate in employee savings plans. Under these plans, a percentage of an employee’s pay may be or is mandated based on applicable laws to be contributed to various savings alternatives. The plans also call for our contributions under several formulae. Charges to income related to our contributions were $9.3 million, $9.2 million and $8.9 million in 2021, 2020 and 2019, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Argo 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 $64.2 million related to our limited partnership investments at December 31, 2021. 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.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
Segment Information	Segment Information We are primarily engaged in underwriting property and casualty insurance and reinsurance. 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 the sales of 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 before income taxes for each segment were as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Revenue: Earned premiums U.S. Operations $ 1,283.7 $ 1,207.6 $ 1,119.9 International Operations 625.8 572.5 609.6 Run-off Lines 0.6 0.4 0.2 Total earned premiums 1,910.1 1,780.5 1,729.7 Net investment income U.S. Operations 119.4 80.3 100.0 International Operations 50.6 26.7 44.2 Run-off Lines 3.6 4.0 5.7 Corporate and Other 14.0 1.7 1.2 Total net investment income 187.6 112.7 151.1 Net realized investment gains (losses) 32.6 (3.6) 80.1 Total revenue $ 2,130.3 $ 1,889.6 $ 1,960.9 For the Years Ended December 31, (in millions) 2021 2020 2019 Income (loss) before income taxes U.S. Operations $ 61.1 $ 113.1 $ 139.3 International Operations 64.1 (75.3) (121.4) Run-off Lines (41.5) (9.6) (9.8) Total segment income before taxes 83.7 28.2 8.1 Corporate and Other (22.5) (34.5) (44.8) Net realized investment and other gains (losses) 32.6 (3.6) 80.1 Foreign currency exchange losses (1.6) (15.4) 9.8 Impairment of intangibles (43.2) — (15.6) Non-operating expense (43.7) (21.1) (37.6) Total income (loss) before income taxes $ 5.3 $ (46.4) $ — The table below presents earned premiums by geographic location for the years ended December 31, 2021, 2020 and 2019. 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 Years Ended December 31, (in millions) 2021 2020 2019 United States $ 1,277.0 $ 1,205.0 $ 1,115.8 United Kingdom 475.3 361.1 391.5 Bermuda 54.8 96.5 80.7 Malta 35.4 59.5 85.0 All other jurisdictions 67.6 58.4 56.7 Total earned premiums $ 1,910.1 $ 1,780.5 $ 1,729.7 The following table represents identifiable assets: December 31, (in millions) 2021 2020 U.S. Operations $ 5,800.1 $ 5,915.5 International Operations 3,932.3 3,911.9 Run-off Lines 314.7 337.3 Corporate and Other 270.7 301.1 Total $ 10,317.8 $ 10,465.8 Included in total assets at December 31, 2021 and 2020 are $554.2 million and $825.9 million, respectively, in assets associated with trade capital providers. The following table represents goodwill and intangible assets, net of accumulated amortization, as of December 31, 2021 and 2020: Goodwill Intangible Assets, Net of (in millions) 2021 2020 2021 2020 U.S. Operations $ 118.6 $ 118.6 $ — $ — International Operations 28.7 28.7 17.3 60.5 Total $ 147.3 $ 147.3 $ 17.3 $ 60.5 During the year ended December 31, 2021, we recorded a $43.2 million impairment charge on the intangibles related to Syndicate 1200. Management’s fourth quarter of 2021 analysis of Syndicate 1200, reflected an implied fair value which was below the reporting unit’s carrying value. As such, the intangibles impairment charge was recorded during the fourth quarter of 2021.

Statutory Accounting Principles

Statutory Accounting Principles	12 Months Ended
	Dec. 31, 2021
Statutory Accounting Principles [Abstract]
Statutory Accounting Principles	Statutory Accounting Principles Financial Information The statutory capital and surplus for our principal operating subsidiaries was as follows: Statutory capital and surplus (1) December 31, (in millions) 2021 2020 Bermuda $ 1,425.8 $ 1,483.4 United Kingdom (2) 414.8 534.7 United States 1,177.2 1,072.1 (1) Such amounts include ownership interests in affiliate insurance and reinsurance subsidiaries. (2) Capital on deposit with Lloyd’s in U.S. dollars The statutory net income (loss) for our principal operating subsidiaries was as follows: Statutory net income (loss) (1) For the Years Ended December 31, (in millions) 2021 2020 2019 Bermuda $ 14.2 $ (18.0) $ 7.1 United Kingdom (2) 8.6 (53.0) (15.1) United States 103.5 76.4 196.1 (1) Such amounts include ownership interests in affiliate insurance and reinsurance subsidiaries. (2) In U.S. dollars Dividends As an insurance holding company, we are largely dependent on dividends and other permitted payments from our insurance subsidiaries to pay cash dividends to our shareholders, for debt service and for our operating expenses. The ability of our insurance subsidiaries to pay dividends to us is subject to certain restrictions imposed by the jurisdictions of domicile that regulate our insurance subsidiaries and each jurisdiction has calculations for the amount of dividends that an insurance and company can pay without the approval of the insurance regulator. The payment of dividends to our shareholders is governed by the Bermuda Companies Act of 1981, as amended, which permits the payment of dividends so long as (i) we are not, or would not be after the payment, unable to pay our liabilities as they become due and (ii) the realizable value of our assets is in excess of our liabilities after taking such payment into account. In light of these restrictions, we have no material restrictions on dividend payments that may be made to our shareholders at December 31, 2021. Argo Re is the direct subsidiary of Argo Group, and therefore, has direct dividend paying capabilities to the parent. As of December 31, 2021, Argo Re’s solvency and liquidity margins and statutory capital and surplus were in excess of the minimum levels required by the Insurance Act. As of December 31, 2021 and 2020, the minimum statutory capital and surplus required to be maintained by Argo Re was $126.8 million and $201.3 million, respectively. Argo Re is generally prohibited from declaring or paying, in any financial year, dividends of more than 25% of its total statutory capital and surplus (as shown on its previous financial year’s statutory balance sheet) unless it files (at least seven days before payment of such dividends) with the Bermuda Monetary Authority (“BMA”) an affidavit signed by at least two directors (one of whom must be a Bermuda resident director if any of the insurer’s directors are resident in Bermuda) and the principal representative stating that it will continue to meet its solvency margin and minimum liquidity ratio. Argo Re may not reduce its total statutory capital by 15% or more, as set out in its previous year’s financial statements, unless it has received the prior approval of the BMA. Based on these regulatory restrictions, the maximum amount available for payment of dividends to Argo Group by Argo Re during 2021 without prior regulatory approval is $356.4 million. In 2021, 2020, and 2019 Argo Re paid cash dividends of $85.0 million, $58.8 million, and $52.1 million respectively, to Argo Group. The proceeds of the dividends were used to repay intercompany balances related primarily to the funding of dividend and interest payments and other corporate expenses. Our U.S. insurance subsidiaries file financial statements prepared in accordance with statutory accounting principles prescribed or permitted by insurance regulatory authorities of the state in which they are underwriting business. The differences between statutory-based financial statements and financial statements prepared in accordance with GAAP vary between jurisdictions. The principal differences are that for statutory-based financial statements, deferred policy acquisition costs are not recognized, a portion of the deferred federal income tax asset is non-admitted, bonds are generally carried at amortized cost, certain assets are non-admitted and charged directly to surplus, a collectability allowance related to reinsurance recoverables is charged directly to surplus and outstanding losses and unearned premium are presented net of reinsurance. As an intermediate insurance holding company, Argo Group U.S., Inc. is largely dependent on dividends and other permitted payments from its insurance subsidiaries to service its debt, fund operating expenses and pay dividends to Argo Ireland. Various state insurance laws restrict the amount that may be transferred to Argo Group U.S. from its subsidiaries in the form of dividends without prior approval of regulatory authorities. In addition, that portion of the insurance subsidiaries’ net equity that results from the difference between statutory insurance principles and GAAP would not be available for dividends . During 2021, Argo Group U.S., Inc. did not receive dividends from its subsidiaries. Argonaut Insurance Company is a direct subsidiary of Argo Group U.S., Inc. and is regulated by the Illinois Division of Insurance. During 2021, Argonaut Insurance Company may be permitted to pay dividends of up to $107.1 million without approval from the Illinois Division of Insurance. Rockwood, a direct subsidiary of Argo Group U.S., Inc., is regulated by the Pennsylvania Department of Insurance. Rockwood may be permitted to pay dividends of up to $10.6 million without approval from the Pennsylvania Department of Insurance during 2022. Each department of insurance may require prior approval for the payment of all dividends, based on business and regulatory conditions of the insurance companies. Argo Underwriting Agency Ltd. (“AUA”) is our wholly-owned subsidiary through which we conduct the operation of Syndicate 1200. Dividend payments from AUA to the immediate parent are not restricted by regulatory authority. Dividend payments will be subject to the earnings, operations, financial condition, capital and general business requirements of AUA. Certain assets of our subsidiaries are pledged to regulatory agencies, serve as collateral for letters of credit or are assigned as the assets of the trade capital providers of our Lloyd’s syndicate, and therefore, are not available funds that may be paid up as dividends to Argo Group. See Note 3, “Investments” and Note 19, “Segment Information” for further discussion.

Insurance Assessments

Insurance Assessments	12 Months Ended
	Dec. 31, 2021
Insurance [Abstract]
Insurance Assessments	Insurance AssessmentsWe participate in statutorily created insolvency guarantee and weather-related loss protection associations in all states where we are authorized to transact business. These associations were formed for the purpose of paying the claims of insolvent companies. We are assessed a pro-rata share of such claims based upon our premium writings, subject to a maximum annual assessment per line of insurance. Certain of these assessments can be recovered through premium tax offsets or policy surcharges. We do not believe that assessments on current insolvencies will have a material impact on our financial condition or results of operations. We have accrued assessments of $5.8 million and $6.7 million at December 31, 2021 and 2020, respectively.

Transactions with Related Parti

Transactions with Related Parties	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Transactions with Related Parties	Transactions with Related PartiesThere were no material transactions with related parties during the twelve months ended December 31, 2021.

Schedule II Condensed Financial

Schedule II Condensed Financial Information of Registrant	12 Months Ended
	Dec. 31, 2021
Condensed Financial Information Disclosure [Abstract]
Schedule II Condensed Financial Information of Registrant	ARGO GROUP INTERNATIONAL HOLDINGS, LTD. SCHEDULE II CONDENSED FINANCIAL INFORMATION OF REGISTRANT (in millions) BALANCE SHEETS December 31, 2021 2020 Assets Short-term investments $ 14.5 $ 0.6 Investment in subsidiaries 1,740.8 1,881.9 Cash 2.0 3.0 Operating lease right-of-use assets 5.3 6.2 Other assets 5.2 14.5 Total assets $ 1,767.8 $ 1,906.2 Liabilities and Shareholders' Equity Junior subordinated debentures $ 28.4 $ 28.4 Accrued underwriting expenses and other liabilities 3.6 6.3 Operating lease liabilities 5.3 6.2 Due to subsidiaries (4.7) 7.5 Total liabilities 32.6 48.4 Shareholders' equity 1,735.2 1,857.8 Total liabilities and shareholders' equity $ 1,767.8 $ 1,906.2 STATEMENTS OF INCOME (LOSS) For the Years Ended December 31, 2021 2020 2019 Revenue: Net investment expense $ — $ — $ (2.9) Net realized investment (loss) gains — (8.3) (0.1) Total revenue — (8.3) (3.0) Expenses: Interest expense 1.2 3.6 6.6 Operating expenses 6.2 20.4 1.3 Other corporate expenses 0.2 4.4 26.8 Total expenses 7.6 28.4 34.7 Net income before equity in earnings of subsidiaries (1) (7.6) (36.7) (37.7) Equity in undistributed earnings of subsidiaries 14.3 (17.4) 23.6 Net income (loss) $ 6.7 $ (54.1) $ (14.1) Dividends on preferred shares 10.5 4.6 — Net (loss) income attributable to common shareholders $ (3.8) $ (58.7) $ (14.1) (1) Argo Group is not subject to taxation. ARGO GROUP INTERNATIONAL HOLDINGS, LTD. SCHEDULE II CONDENSED FINANCIAL INFORMATION OF REGISTRANT (in millions) STATEMENTS OF CASH FLOWS For the Years Ended December 31, 2021 2020 2019 Cash flows from operating activities: Net income (loss) $ 6.7 $ (54.1) $ (14.1) Adjustments to reconcile net income to net cash provided by (used in) operating activities: Amortization and depreciation 1.5 1.1 1.3 Share-based payments expense 2.3 3.6 8.1 Net realized investment and other losses (gains) — 8.3 0.1 Loss on disposal of fixed assets (3.0) 0.1 — Undistributed (losses) earnings of subsidiaries (14.3) 17.4 (23.6) Change in: Prepaid assets 7.2 (2.2) 2.5 Accrued underwriting expenses (4.1) (9.1) 7.3 Due (to) from subsidiaries (12.1) (11.1) 16.8 Other, net (3.9) (7.8) (12.1) Cash used in operating activities (19.7) (53.8) (13.7) Cash flows from investing activities: Change in short-term investments (13.9) — 3.2 Settlements of foreign currency exchange forward contracts 0.5 0.1 (0.2) Capital contribution to subsidiaries — (145.3) — Proceed from sale of Ariel Re — 30.0 — Dividend received from subsidiaries 85.0 71.9 52.1 Cash provided by (used in) investing activities 71.6 (43.3) 55.1 Cash flows from financing activities: Issuance for preferred shares, net of issuance costs — 144.0 — Activity under stock incentive plans 1.3 1.8 1.9 Payment of cash dividend to preferred shareholders (10.5) (4.6) — Payment of cash dividend to common shareholders (43.7) (43.0) (43.1) Cash (used in) provided by financing activities (52.9) 98.2 (41.2) Change in cash (1.0) 1.1 0.2 Cash, beginning of year 3.0 1.9 1.7 Cash, end of year $ 2.0 $ 3.0 $ 1.9

Schedule III Supplemental Insur

Schedule III Supplemental Insurance Information	12 Months Ended
	Dec. 31, 2021
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Abstract]
Schedule III Supplemental Insurance Information	ARGO GROUP INTERNATIONAL HOLDINGS, LTD. SCHEDULE III SUPPLEMENTAL INSURANCE INFORMATION FOR THE YEARS ENDED DECEMBER 31, 2021, 2020 AND 2019 (in millions) Segment DAC (a) Reserves for Losses and Loss Adjustment Expenses (b) UPR (c) Premium Revenue (d) Net Investment Income (l) Loss & LAE (e) Amortization (Deferral) DAC (f) (2) Other Operating Expenses (3) Net Premiums Written (g) Year Ended December 31, 2021 U.S. Operations 103.7 3,422.4 973.7 1,283.7 119.4 908.2 (5.8) 425.1 1,304.8 International Operations 64.3 1,911.4 493.1 625.8 50.6 362.1 (10.0) 256.3 671.7 Run-off Lines — 261.2 — 0.6 3.6 44.3 — 1.0 0.8 Corporate and Other — — — — 14.0 — — 35.7 — Total $ 168.0 $ 5,595.0 $ 1,466.8 $ 1,910.1 $ 187.6 $ 1,314.6 $ (15.8) $ 718.1 $ 1,977.3 Year Ended December 31, 2020 U.S. Operations 98.2 3,091.9 939.2 1,207.6 80.3 768.7 (8.6) 398.3 1,223.0 International Operations 65.4 2,077.6 525.4 572.5 26.7 428.6 (0.7) 242.3 586.6 Run-off Lines — 236.5 0.2 0.4 4.0 11.5 — 1.7 0.5 Corporate and Other — — — — 1.7 — — 34.7 — Total $ 163.6 $ 5,406.0 $ 1,464.8 $ 1,780.5 $ 112.7 $ 1,208.8 $ (9.3) $ 677.0 $ 1,810.1 Year Ended December 31, 2019 U.S. Operations 89.7 2,775.1 896.1 1,119.9 100.0 690.4 (2.5) 371.2 1,166.3 International Operations 70.5 2,129.0 514.7 609.6 44.2 518.3 14.9 235.3 588.1 Run-off Lines — 253.5 0.1 0.2 5.7 12.0 — 2.4 0.2 Corporate and Other — — — — 1.2 — — 44.7 — Total $ 160.2 $ 5,157.6 $ 1,410.9 $ 1,729.7 $ 151.1 $ 1,220.7 $ 12.4 $ 653.6 $ 1,754.6 (a) Deferred policy acquisition costs. (b) Future policy benefits, losses, claims and loss expenses. (c) Unearned premiums. (d) Premium revenue, net (premiums earned). (e) Benefits, claims, losses and settlement expenses. (f) Amortization (deferral) of deferred policy acquisition costs. (g) Premiums written, net. (1) Net investment income allocated based upon each segment’s share of investable funds. (2) The amortization (deferral) of DAC will not equal the change in the balance sheet. See Note 1, “Business and Significant Accounting Policies” for further discussion. (3) Other insurance expenses allocated based on specific identification, where possible, and related activities.

Schedule V Valuation and Qualif

Schedule V Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2021
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule V Valuation and Qualifying Accounts	ARGO GROUP INTERNATIONAL HOLDINGS, LTD. SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS (in millions) Balance at Charged to Capital Loss Net Operating Charged to Deductions Balance at Year Ended December 31, 2021 Deducted from assets: Valuation allowance for deferred tax asset $ 28.6 $ (0.7) $ — $ — $ — $ — $ 27.9 Year Ended December 31, 2020 Deducted from assets: Valuation allowance for deferred tax asset $ 28.1 $ 0.5 $ — $ — $ — $ — $ 28.6 Year Ended December 31, 2019 Deducted from assets: Valuation allowance for deferred tax asset $ 29.9 $ (1.8) $ — $ — $ — $ — $ 28.1

Schedule VI Supplemental Inform

Schedule VI Supplemental Information for Property-Casualty Insurance Companies	12 Months Ended
	Dec. 31, 2021
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
Schedule VI Supplemental Information for Property-Casualty Insurance Companies	ARGO GROUP INTERNATIONAL HOLDINGS, LTD. SCHEDULE VI SUPPLEMENTAL INFORMATION FOR PROPERTY-CASUALTY INSURANCE COMPANIES (in millions) For the Years Ended December 31, 2021 2020 2019 Deferred acquisition costs $ 168.0 $ 163.6 $ 160.2 Reserves for losses and loss adjustment expenses $ 5,595.0 $ 5,406.0 $ 5,157.6 Unamortized discount in reserves for losses $ 18.8 $ 17.8 $ 17.9 Unearned premiums $ 1,466.8 $ 1,464.8 $ 1,410.9 Premiums earned $ 1,910.1 $ 1,780.5 $ 1,729.5 Net investment income $ 187.6 $ 112.7 $ 151.1 Losses and loss adjustment expenses incurred: Current year $ 1,176.3 $ 1,201.1 $ 1,082.6 Prior years 138.3 7.7 138.1 Losses and loss adjustment expenses incurred $ 1,314.6 $ 1,208.8 $ 1,220.7 (Deferral) amortization of policy acquisition costs (1) $ (15.8) $ (9.3) $ 12.4 Paid losses and loss adjustment expenses, net of reinsurance $ 869.2 $ 1,119.8 $ 1,030.3 Gross premiums written $ 3,181.2 $ 3,233.3 $ 3,130.2 (1) The amortization (deferral) of policy acquisition costs will not equal the change in the balance sheet. For further discussion, see Note 1, “Business and Significant Accounting Policies.”

Business and Significant Acco_2

Business and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Business	Business Argo Group International Holdings, Ltd. (“Argo Group,” “we” or the “Company”) is an underwriter of specialty insurance products in the property and casualty market. Argo Group U.S., Inc. (“Argo Group U.S.”) is a subsidiary of Argo Financial Holding (Ireland) UC (“Argo Ireland”). Argo Underwriting Agency Limited (“Syndicate 1200”) is a subsidiary of Argo International Holdings, Ltd., Argo Re Ltd. (“Argo Re”), a Bermuda based company, is the parent of both Argo Ireland and Argo International Holdings, Ltd. Argo Re is directly owned by Argo Group. On February 15, 2022, we completed the sale of our Brazilian operations, Argo Seguros Brasil S.A. (“Argo Seguros”), to Spice Private Equity Ltd., an investment company focused on global private equity investments. For further disclosures see Note 2, “Recent Acquisitions, Disposals & Other Transactions.” Effective November 25, 2020, we completed the sale of Ariel Re, to Pelican Ventures and J.C. Flowers & Co. Ariel Re is the reinsurance platform through which Lloyd’s Syndicate 1910 reinsurance business is underwritten. Under the terms of the agreement, the buying group’s corporate member provided Syndicate 1910’s capital for the 2021 Lloyd’s year of account, and Argo Group has agreed to retain historical reserves and the remaining exposure for the 2020 and prior Lloyd’s years of account. We conduct our ongoing business through two primary segments - U.S. Operations and International Operations. In addition to these main business segments, we have a Run-off Lines segment for certain products we no longer underwrite. U.S. Operations is comprised of the Excess and Surplus Lines businesses focusing on the U.S.-based risks that the standard, admitted insurance market is unwilling or unable to write, and through other specialized admitted and non-admitted business distributed through retail, wholesale, and managing general brokers/agents in the specialty insurance market. Excess and Surplus Lines products are underwritten by Colony Insurance Company (“Colony”). The other U.S. specialized admitted and non-admitted businesses consist of the following operations: Argo Pro, U.S. Specialty Programs, Argo Surety, Rockwood Casualty Insurance Company (“Rockwood”), Argo Insurance and Inland Marine. International Operations is comprised of the Lloyd’s Syndicate platform (Syndicate 1200), Argo Insurance Bermuda, Continental Europe and Latin America. Syndicate 1200 insurance products are underwritten by Argo Underwriting Agency Limited based in London, under the Lloyd’s of London (“Lloyd’s”) global franchise. The additional International Operations business include ArgoGlobal SE in Malta, ArgoGlobal Assicurazoni in Italy, and Argo Seguros in Brazil. These businesses provide a broad range of commercial property, casualty, professional liability and specialty coverages in a number of countries and jurisdictions outside the United States (“U.S.”). Our Run-off Lines segment includes liabilities associated with other liability policies that were issued in the 1960s, 1970s and into the 1980s, as well as the former risk-management business and other business no longer underwritten.
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The consolidated financial statements of Argo Group and its subsidiaries have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The preparation of consolidated 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 differ from those estimates. Specifically, estimates for reserves for losses and loss adjustment expenses are based upon past claim experience modified for current trends as well as prevailing economic, legal and social conditions. Although management believes that amounts included in the accompanying consolidated financial statements are reasonable, such estimates may be more or less than the amounts ultimately paid when the claims are settled. The estimates are continually reviewed and any changes are reflected in current operating results. Further, the nature of loss exposures involves significant variability due to the nature of the long-tailed payments on certain claims. As such, losses and loss adjustment expenses could vary significantly from the recorded amounts. The consolidated financial statements include the accounts and operations of Argo Group and its subsidiaries. All material intercompany accounts and transactions have been eliminated. In order to conform the 2020 and 2019 consolidated statements of income (loss) to the 2021 presentation the Company has (a) offset fee income to fee expense, and (b) reclassified amounts from net realized investment gain (losses) and underwriting, acquisition and insurance expenses to non-operating expenses. Amounts related to trade capital providers, who are third-party capital participants that provide underwriting capital to Syndicate 1200 are included in the balance sheet. Trade capital providers participate on a quota share basis, assuming 100% of their contractual participation in the underwriting syndicate results and with such results settled on a year of account basis. We have evaluated our investment in our eleven statutory trusts (collectively, the “Trusts”) and one charitable foundation (the “Foundation”) under the Financial Accounting Standards Board’s (“FASB’s”) provisions for consolidation of variable interest entities under Accounting Standards Codification (“ASC”) Topic 810-10, “Consolidation,” as amended. We determined that the Trusts and the Foundation are variable interest entities due to the fact that the Trusts and the Foundation do not have sufficient equity to finance their activities without additional subordinate financial support from other parties. We do not have any power to direct the activities that impact the Trusts’ or the Foundation’s economic performance. We are not entitled to receive a majority of the residual returns of the Trusts. Additionally, we are not responsible for absorbing the majority of the expected losses of the Trusts; therefore, we are not the primary beneficiary and, accordingly, the Trusts are not included in our consolidated financial statements. The expenses and donations of the charitable foundation in Bermuda are paid by Argo Group and have been included in the consolidated results.
Cash	Cash Cash consists of cash deposited in operating accounts with commercial banks. Interest-bearing cash accounts are classified as short term investments.
Investments	Investments Investments in fixed maturities at December 31, 2021 and 2020 include bonds and structured securities. Equity securities include common stocks, preferred stocks and mutual funds. Other investments consist of foreign regulatory deposits, hedge funds, private equity funds, private equity direct investments, and voluntary pools. Short-term investments consist of money market funds, certificates of deposit, bonds, sovereign debt and interest-bearing cash accounts. Investments maturing in less than one year are classified as short-term investments in our consolidated financial statements. The amortized cost of fixed maturity securities is adjusted for amortization of premiums and accretion of discounts. This amortization or accretion is included in “Net investment income” in our Consolidated Statements of Income (Loss). For the structured securities portion of the fixed maturity securities portfolio, we recognize income using a constant effective yield based on anticipated prepayments and the estimated economic life of the securities. Premium or discount on high investment grade securities (rated AA or higher) is amortized into income using the retrospective method. Premium or discount on lower grade securities (rated less than AA) is amortized into income using the prospective method. Our investments in fixed maturities are considered available-for-sale and are carried at fair value. As available-for-sale investments, changes in the fair value of fixed maturities are not recognized in income during the period, but rather are recognized as a separate component of shareholders’ equity until realized. Fair value of these investments is estimated using prices obtained from third-party pricing services, where available. For securities where we were unable to obtain fair values from a pricing service or broker, fair values were estimated using information obtained from investment advisors. We performed several processes to ascertain the reasonableness of these investment values by (1) obtaining and reviewing internal control reports for our service providers that obtain fair values from third-party pricing services, (2) obtaining and reviewing evaluated pricing methodology documentation from third-party pricing services and (3) comparing the security pricing received from a secondary third-party pricing service versus the prices used in the consolidated financial statements and obtaining additional information for variances that exceeded a certain threshold. As of December 31, 2021, investments reported at fair value for which we did not receive a fair value from a pricing service or broker accounted for less than 1% of our investment portfolio. The actual value at which such securities could be sold or settled with willing buyer or seller may differ from such estimated fair values depending on a number of factors including, but not limited to, current and future economic conditions, the quantity sold or settled, the presence of an active market and the availability of a willing buyer or seller. The cost of securities sold is based on the specific identification method. Our investments in equity securities are reported at fair value, changes in the fair value of equity securities are now included in “Net realized investment (gains) losses” in our consolidated statements of income. Changes in the value of other investments consisting of hedge funds, private equity funds, private equity direct investments and voluntary pools are principally recognized in income during the period using the equity method of accounting. Our 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. The underlying assets are invested in government securities, agency securities and corporate bonds whose values are obtained from Lloyd’s. Foreign currency future contracts held by us are valued by our counterparties using market driven foreign currency exchanges rates. We regularly review our investments to identify and evaluate those that may have credit impairments. For fixed maturity securities, the evaluation for credit losses is generally based on the present value of expected cash flows of the security as compared to the amortized book value, the financial condition, near-term and long-term prospects for the issuer, including industry conditions, implications of rating agency actions, the likelihood of principal and interest recoverability and whether it is more likely than not we will be required to sell the investment prior to the anticipated recovery in value. Effective January 1, 2020 with the adoption of ASU 2016-13 Financial Instruments-Credit Losses, we recognize credit losses on fixed maturities through an allowance account. For fixed maturities that we do not intend to sell or for which it is more likely than not we will not be required to sell prior to the anticipated recovery in value, we separate the credit component of the impairment from the component related to all other market factors and report the credit loss component to net realized investment gains (losses) in the Consolidated Statement of Income (Loss). The impairment related to all other market factors is reported as a separate component of shareholder’s equity in other comprehensive income (loss). The credit loss allowance account is adjusted for any additional credit losses or subsequent recoveries and the cost basis of the fixed maturity security is not adjusted. For fixed maturity securities that we intend to sell or for which it is more likely than not that we will be required to sell before an anticipated recovery in value, the full amount of the impairment is recognized in net realized investment gains (losses) in the Consolidated Statement of Income and the cost basis of the fixed maturity security is adjusted to reflect the recognized realized loss. The new cost basis is not adjusted for any recoveries in fair value. We report accrued investment income separately from fixed maturity securities and have elected to not measure an allowance for credit losses for accrued investment income. The write-off of investment income accrued for fixed maturities that have defaulted on interest payments is recognized as a loss in net realized investment gains (losses), in the period of the default, in the Consolidated Statement of Income (Loss). All investment balances include amounts relating to trade capital providers. The results of operations and other comprehensive income exclude amounts relating to trade capital providers. Trade capital providers’ participation in the syndicate results are included in reinsurance recoverable for ceded losses and reinsurance payable for ceded premiums.
Receivables	Receivables Premiums receivable, representing amounts due from insureds, are presented net of an allowance for uncollectible premiums, including expected credit losses, both dispute and credit related. Premiums receivable include amounts relating to the trade capital providers’ quota share. The allowance is based upon our ongoing review of amounts outstanding, historical loss data, including delinquencies and write-offs, current and forecasted economic conditions and other relevant factors. Credit risk is partially mitigated by our ability to cancel the policy if the policyholder does not pay the premium. Reinsurance recoverables represent amounts of paid losses and loss adjustment expenses, case reserves and incurred but not reported (“IBNR”) amounts ceded to reinsurers under reinsurance treaties. Reinsurance recoverables also reflect amounts that are due from trade capital providers. Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. We report our reinsurance recoverables net of an allowance for estimated uncollectible reinsurance, including expected credit losses. The allowance is based upon our ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors. We use the rating-based method to estimate the uncollectible reinsurance reserves due to credit losses. Under this method, reinsurance credit risk is estimated by considering the reinsurers probability of default. Reinsurance recoverables are forecasted out of the assumed billing periods and a liquidation factor is applied based on the rating of the reinsurer and adjusted as needed based on our historical experience with the reinsurers. Additionally, reinsurance receivable balances are evaluated to identify any dispute risk and when required, an additional reserve is recorded. Amounts deemed to be uncollectible, including amounts due from known insolvent reinsurers, are written off against the allowance. Changes in the allowance, as well as any subsequent collections of amounts previously written off, are reported as part of underwriting expense. We evaluate and monitor the financial condition of our reinsurers under voluntary reinsurance arrangements to minimize our exposure to significant losses from reinsurer insolvencies. Recoveries occur when subsequent collection or litigation results in the receipt of amounts previously written off. Amounts recovered
Earned Premiums	Earned Premiums Premium revenue is generally recognized ratably over the policy period. Premiums that have yet to be earned are reported as “unearned premiums” in our consolidated balance sheets. Unearned premium balances include cessions to reinsurers including trade capital providers, while the earned premium recognized in our consolidated statements of income (loss) excludes amounts relating to trade capital providers. The trade capital providers’ quota share amount is included in “ceded reinsurance payable, net”. Assumed reinstatement premiums that reinstate coverage are written and earned at the time the associated loss event occurs. The original premium is earned over the remaining exposure period of the contract. Reinstatement premiums are estimated based upon contract terms for reported losses and estimated for incurred but not reported losses.
Retrospectively Rated Policies	Retrospectively Rated PoliciesWe have written a number of workers compensation, property and other liability policies that are retrospectively rated. Under this type of policy, the policyholder or coverholder may be entitled, subsequent to coverage expiration, to a refund or may owe additional premiums based on the amount of losses incurred under the policy. The retrospective premium adjustments on certain policies are limited to a minimum or maximum premium adjustment, which is calculated as a percentage of the standard amount of premium charged during the life of the policy. Accrued retrospectively rated premiums have been determined based on estimated ultimate loss experience of the individual policyholder accounts.
Deferred Acquisition Costs	Deferred Acquisition Costs Policy acquisition costs, which include commissions, premium taxes, fees and certain other costs of underwriting policies, are deferred, when such class of policies are profitable, and amortized over the same period in which the related premiums are earned. To qualify for capitalization, the policy acquisition cost must be directly related to the successful acquisition of an insurance contract. Anticipated investment income is considered in determining whether the deferred acquisition costs are recoverable and whether a premium deficiency exists. We continually review the methods of making such estimates and establishing the deferred costs with any adjustments made in the accounting period in which the adjustment arose. The 2021 and 2020 net amortization of policy acquisition costs will not equal the change in our consolidated balance sheets as the trade capital providers’ share is not reflected in our consolidated statements of income (loss) and differences arise from foreign currency exchange rates applied to deferred acquisition costs which are treated as a nonmonetary asset.
Leases	Leases We determine if a contract contains a lease at inception and recognize operating lease right-of-use assets and operating lease liabilities based on the present value of the future minimum lease payments at the commencement date. As our leases do not provide an implicit interest rate, we use our incremental borrowing rate based on the information available at the commencement date to determine the present value of future payments. Lease agreements have lease and non-lease components. We account for these components separately, therefore our operating lease right-of-use asset and operating lease liabilities represent base rent only. Lease expense is recognized on a straight-line basis over the lease term. Renewal options are evaluated prior to the expiration date and recorded upon exercise. We adopted ASU 2016-02, “Leases” (Topic 842) on the effective date of January 1, 2019 and applied the following practical expedients: • We have elected to adopt this standard using the option transition method, which allows companies to continue applying the guidance under the lease standard in effect at that time in the comparative periods presented in the consolidated financial statements. The adoption of the standard had no effect on our consolidated shareholders’ equity. Prior periods were not restated. • We have elected the “package of practical expedients,” which permits us not to reassess under the new standard our prior conclusion about lease identification, lease classification and initial direct costs.
Lessor, leases	Where we are the lessor, we have elected the practical expedient which permits us to not separate non-lease components from the associated lease components if the non-lease components otherwise would be accounted for in accordance with the new revenue standard.
Reserves for Losses and Loss Adjustment Expenses	Reserves for Losses and Loss Adjustment Expenses Liabilities for unpaid losses and loss adjustment expenses include the accumulation of individual case estimates for claims reported as well as estimates of IBNR claims and estimates of claim settlement expenses. Reinsurance recoverables on unpaid claims and claim expenses represent estimates of the portion of such liabilities that will be recoverable from reinsurers. Amounts recoverable from reinsurers are recognized as assets at the same time and in a manner consistent with the unpaid claims liabilities associated with the reinsurance policy.
Reinsurance	Reinsurance In the normal course of business, our insurance subsidiaries cede risks above certain retention levels to other insurance companies. Reinsurance recoverables include claims we paid and estimates of unpaid losses and loss adjustment expenses that are subject to reimbursement under reinsurance and retrocessional contracts. The method for determining reinsurance recoverables for unpaid losses and loss adjustment expenses involves reviewing actuarial estimates of gross unpaid losses and loss adjustment expenses to determine our ability to cede unpaid losses and loss adjustment expenses under our existing reinsurance contracts. This method is continually reviewed and updated and any resulting adjustments are reflected in earnings in the period identified. Reinsurance premiums, commissions and expense reimbursements are accounted for on a basis consistent with those used in accounting for the original policies issued and the term of the reinsurance contracts. Amounts recoverable from reinsurers for losses and loss adjustment expenses for which our insurance and reinsurance subsidiaries have not been relieved of their legal obligations to the policyholder are reported as assets.
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill and intangible assets are allocated to the segment in which the results of operations for the acquired company are reported (see Note 19, “Segment Information” for further discussion). Intangible assets with a finite life are amortized over the estimated useful life of the asset. Goodwill and intangible assets with an indefinite useful life are not amortized. Goodwill and intangible assets are tested for impairment on an annual basis or more frequently if events or changes in circumstances indicate that the carrying amount may not be recoverable.
Property and Equipment	Property and EquipmentProperty and equipment used in operations, including certain costs incurred to develop or obtain computer software for internal use, are capitalized and carried at cost less accumulated depreciation and are reported in “other assets” in our consolidated balance sheets. Depreciation is calculated using a straight-line method over the estimated useful lives of the assets, generally three
Derivative Instruments	Derivative Instruments We enter into short-term, currency spot and forward contracts to manage operational currency exposure from our non-USD insurance operations,and gain exposure to a total return strategy which invests in multiple currencies. The forward contracts are typically thirty to ninety days and are renewed as management deems necessary to accomplish the objectives of the contracts. These foreign currency forward contracts are carried at fair value in our Consolidated Balance Sheets in “Other assets” at December 31, 2021 and 2020, respectively. The realized and unrealized gains and losses are included in “Net realized investment and other gains (losses) in our Consolidated Statements of Income. The forwards contracts are not designated as hedges for accounting purposes.
Share-Based Payments	Share-Based PaymentsCompensation expense for share-based payments is recognized based on the measurement-date fair value for awards that will settle in shares. Compensation expense for awards that are settled in equity are recognized on a straight line pro rata basis over the vesting period, adjusted for expected forfeitures.
Foreign Currency Exchange Gain (Loss)	Foreign Currency Exchange Gain (Loss)The reporting currency of the Company is the U.S. dollar (“USD”). USD is the functional currency of all but three of our foreign operations. For foreign operations with the U.S. dollar as the functional currency, monetary assets and liabilities that are denominated in local currencies are remeasured at the exchange rates in effect at the balance sheet date. The resulting gains and losses from changes in the foreign exchange rates are reflected in net income. Non-monetary assets and liabilities are not remeasured. In the case of our non-USD denominated available-for-sale investments, the change in exchange rates between the local currency and USD at each balance sheet date represents an unrealized appreciation or depreciation in value of these securities and is included as a component of accumulated other comprehensive income (loss). Revenues and expenses denominated in foreign currencies are translated at the prevailing exchange rate during the period with the resulting foreign exchange gains and losses included in net income for the period.
Income Taxes	Income Taxes Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in net income in the period in which the change is enacted. We recognize potential accrued interest and penalties within our global operations in “interest expense” and “underwriting, acquisition and insurance expenses,” respectively, in our consolidated statements of income (loss) related to unrecognized tax benefits.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-13, “Measurement of Credit Losses on Financial Instruments” (Topic 326), commonly referred to as current expected credit losses or "CECL." ASU 2016-13 requires organizations to estimate credit losses on certain types of financial instruments, including receivables and available-for-sale debt securities, by introducing an approach based on expected losses. The expected loss approach will require entities to incorporate considerations of historical information, current information and reasonable and supportable forecasts. The updated guidance also amends the previous other-than-temporary impairment model for available-for-sale debt securities by requiring the recognition of impairments relating to credit losses through an allowance account and limits the amount of credit loss to the difference between a security’s amortized cost basis and its fair value. In addition, the length of time a security has been in an unrealized loss position will no longer impact the determination of whether a credit loss exists. The guidance was effective for fiscal years beginning after December 15, 2019, including interim periods within the year of adoption. The guidance required a modified retrospective transition method. We adopted the updated guidance effective January 1, 2020 using the modified retrospective approach, which resulted in a $7.9 million net of tax reduction to retained earnings. Partially offsetting this reduction of retained earnings was a $5.7 million net of tax increase in other comprehensive income representing the reclassification of unrealized investment losses to credit losses under this accounting update. The cumulative effect adjustment decreased shareholders’ equity $2.2 million. Please see Note 3, “Investments” and Note 4, “Allowance for Credit Losses” for further discussion of the impact of ASU 2016-13 on our financial position and results of operations at and for the year ended December 31, 2021 and 2020, respectively.

Business and Significant Acco_3

Business and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Intangible Assets And Accumulated Amortization	The following table presents our intangible assets and accumulated amortization at December 31: December 31, 2021 2020 (in millions) Gross Carrying Accumulated Gross Carrying Accumulated Lloyd's capacity $ 17.3 n/a $ 60.5 n/a Distribution network 45.5 45.5 45.5 45.5 Other 6.2 6.2 6.2 6.2 $ 69.0 $ 51.7 $ 112.2 $ 51.7
Supplemental Cash Flow Information	Interest paid and income taxes paid (recovered) were as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Senior unsecured fixed rate notes $ 9.3 $ 9.3 $ 9.3 Junior subordinated debentures 10.0 11.9 16.2 Other indebtedness 2.5 5.2 7.6 Total interest paid $ 21.8 $ 26.4 $ 33.1 Income taxes paid 43.0 47.7 24.0 Income taxes recovered (2.6) (1.8) (0.1) Income taxes paid, net $ 40.4 $ 45.9 $ 23.9

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 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 and fair value in fixed maturity investments were as follows: December 31, 2021 (in millions) Amortized Gross Gross Allowance for Credit Losses (1) Fair Fixed maturities U.S. Governments $ 422.7 $ 5.5 $ 3.2 $ — $ 425.0 Foreign Governments 234.7 2.2 3.9 0.2 232.8 Obligations of states and political subdivisions 166.7 5.8 1.2 — 171.3 Corporate bonds 1,972.3 33.5 20.3 2.2 1,983.3 Commercial mortgage-backed securities 416.7 6.3 4.3 — 418.7 Residential mortgage-backed securities 480.7 7.5 5.7 — 482.5 Asset-backed securities 173.0 1.3 0.6 0.1 173.6 Collateralized loan obligations 336.4 1.3 1.6 — 336.1 Total fixed maturities $ 4,203.2 $ 63.4 $ 40.8 $ 2.5 $ 4,223.3 December 31, 2020 (in millions) Amortized Gross Gross Allowance for Credit Losses Fair Fixed maturities U.S. Governments $ 385.4 $ 14.7 $ 0.3 $ — $ 399.8 Foreign Governments 284.1 11.6 0.7 0.2 294.8 Obligations of states and political subdivisions 163.1 7.7 0.3 0.1 170.4 Corporate bonds 1,925.9 75.3 13.3 6.1 1,981.8 Commercial mortgage-backed securities 324.8 15.2 0.3 — 339.7 Residential mortgage-backed securities 491.4 17.4 0.6 — 508.2 Asset-backed securities 120.5 2.9 0.4 0.2 122.8 Collateralized loan obligations 285.9 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 December 31, 2021, by contractual maturity, were as follows: (in millions) Amortized Fair Due in one year or less $ 281.7 $ 284.6 Due after one year through five years 1,692.0 1,704.8 Due after five years through ten years 710.0 711.3 Thereafter 112.6 111.6 Structured securities 1,406.9 1,411.0 Total $ 4,203.2 $ 4,223.3
Schedule of Carrying Value Redemption Characteristics and Unfunded Investment Commitments of Other Invested Assets Portfolio	Details regarding the carrying value and unfunded investment commitments of the other invested assets portfolio as of December 31, 2021 and 2020 were as follows: December 31, 2021 (in millions) Carrying Unfunded Investment Type Hedge funds $ 58.6 $ — Private equity 248.9 64.2 Overseas deposits 74.9 — Other 4.8 — Total other investments $ 387.2 $ 64.2 December 31, 2020 (in millions) Carrying Unfunded Investment Type Hedge funds $ 111.2 $ — Private equity 211.4 80.0 Overseas deposits 102.1 — Other 4.7 — 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: December 31, 2021 Less Than One Year One Year or Greater Total (in millions) Fair Unrealized Fair Unrealized Fair Unrealized Fixed maturities U.S. Governments $ 193.4 $ 2.6 $ 14.6 $ 0.6 $ 208.0 $ 3.2 Foreign Governments 152.4 3.3 2.6 0.6 155.0 3.9 Obligations of states and political subdivisions 46.0 0.8 0.1 0.4 46.1 1.2 Corporate bonds 854.3 18.3 41.7 2.0 896.0 20.3 Commercial mortgage-backed securities 198.8 4.1 6.5 0.2 205.3 4.3 Residential mortgage-backed securities 284.2 5.6 4.0 0.1 288.2 5.7 Asset-backed securities 62.6 0.6 — 62.6 0.6 Collateralized loan obligations 176.1 1.6 0.5 176.6 1.6 Total fixed maturities $ 1,967.8 $ 36.9 $ 70.0 $ 3.9 $ 2,037.8 $ 40.8 December 31, 2020 Less Than One Year One Year or Greater Total (in millions) Fair Unrealized Fair Unrealized Fair Unrealized Fixed maturities U.S. Governments $ 40.6 $ 0.3 $ — $ — $ 40.6 $ 0.3 Foreign Governments 18.0 0.5 0.1 0.2 18.1 0.7 Obligations of states and political subdivisions 5.2 0.3 — — 5.2 0.3 Corporate bonds 202.5 6.7 17.5 6.6 220.0 13.3 Commercial mortgage-backed securities 21.8 0.3 — — 21.8 0.3 Residential mortgage-backed securities 74.4 0.4 3.0 0.2 77.4 0.6 Asset-backed securities 4.6 0.4 — — 4.6 0.4 Collateralized loan obligations 121.1 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
Schedule of Debt Securities, Available-for-sale, Allowance for Credit Loss	Foreign Governments Obligations of states and political subdivisions Corporate bonds Asset backed securities Total Beginning balance, January 1, 2020 $ — $ — $ — $ — $ — Additions-initial adoption of accounting standard — — 6.8 0.1 6.9 Securities for which allowance was not previously recorded 0.3 0.3 15.3 — 15.9 Securities sold during the period (0.2) — (39.0) (0.1) (39.3) Additional net increases (decreases) in existing allowance 0.1 (0.2) 23.0 0.2 23.1 Ending balance, December 31, 2020 $ 0.2 $ 0.1 $ 6.1 $ 0.2 $ 6.6 Foreign Governments Obligations of states and political subdivisions Corporate bonds Asset backed securities Total Beginning balance, January 1, 2021 $ 0.2 $ 0.1 $ 6.1 $ 0.2 $ 6.6 Securities for which allowance was not previously recorded — — 2.7 0.2 2.9 Securities sold during the period — — (3.5) — (3.5) Additional net increases (decreases) in existing allowance — (0.1) (3.1) (0.3) (3.5) Ending balance, December 31, 2021 $ 0.2 $ — $ 2.2 $ 0.1 $ 2.5
Schedule of Investment Income and Expenses	Investment income and expenses were as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Investment income: Interest on fixed maturities $ 98.9 $ 108.6 $ 129.5 Dividends on equity securities 3.1 2.8 11.1 Income on alternative investments 95.5 10.4 22.4 Income on short-term and other investments 3.3 3.9 8.9 Investment income 200.8 125.7 171.9 Investment expenses (13.2) (13.0) (20.8) Net investment income $ 187.6 $ 112.7 $ 151.1
Schedule of Company's Gross Realized Investment Gains (Losses)	The following table presents our realized investment gains (losses): For the Years Ended December 31, (in millions) 2021 2020 2019 Realized gains on fixed maturities and other Fixed maturities $ 30.6 $ 37.1 $ 22.2 Other investments, including short-terms 9.8 93.8 0.1 Other assets 3.3 33.2 33.0 43.7 164.1 55.3 Realized losses on fixed maturities and other Fixed maturities (11.8) (35.2) (11.7) Other investments, including short-terms (18.5) (78.6) (31.3) Other assets (12.5) (7.2) — (42.8) (121.0) (43.0) Net (losses) recognized on fixed maturities and other Credit losses on fixed maturities 0.6 (39.9) — Other-than-temporary impairment losses — — (20.3) Other (6.3) — — (5.7) (39.9) (20.3) Equity securities Net realized gains (losses) on equity securities 71.5 (17.1) 128.9 Change in unrealized gains (losses) on equity securities held at the end of the period (34.1) 10.3 (40.8) Net realized gains (losses) on equity securities 37.4 (6.8) 88.1 Net realized investment and other gains (losses) before income taxes 32.6 (3.6) 80.1 Income tax (benefit) provision 6.2 1.3 16.2 Net realized investment gains (losses), net of income taxes $ 26.4 $ (4.9) $ 63.9
Schedule of Changes in Unrealized Appreciation (Depreciation)	Changes in unrealized appreciation (depreciation) related to investments are summarized as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Change in unrealized gains (losses) Fixed maturities $ (105.9) $ 96.0 $ 93.3 Other investments — (14.3) 4.4 Other and short-term investments (1.0) 0.7 0.2 Net unrealized investment gains (losses) before income taxes (106.9) 82.4 97.9 Income tax provision (benefit) (21.5) 16.5 15.4 Net unrealized investment gains (losses), net of income taxes $ (85.4) $ 65.9 $ 82.5
Schedule of Fair Value of Foreign Currency Exchange Forward Contracts	The fair value of our foreign currency exchange forward contracts as of December 31 was as follows: (in millions) December 31, 2021 December 31, 2020 Operational currency exposure $ (0.3) $ 0.4 Asset manager investment exposure (0.3) (0.2) Total return strategy — 0.7 Total $ (0.6) $ 0.9
Schedule of Realized Gains and Losses of Investment on Foreign Currency Exchange Forward Contracts	The following table presents our gross investment realized gains and losses on our foreign currency exchange forward contracts: For the Years Ended December 31, (in millions) 2021 2020 2019 Realized gains Operational currency exposure $ 16.5 $ 13.2 $ 5.7 Asset manager investment exposure 3.7 2.2 2.7 Total return strategy 13.0 61.6 22.5 Gross realized investment gains 33.2 77.0 30.9 Realized losses Operational currency exposure (28.9) (8.6) (10.6) Asset manager investment exposure (1.0) (4.0) (0.8) Total return strategy (12.0) (62.3) (17.6) Gross realized investment losses (41.9) (74.9) (29.0) Net realized investment gains (losses) on foreign $ (8.7) $ 2.1 $ 1.9
Schedule of Restricted Assets	The following table presents our components of restricted assets at December 31: (in millions) December 31, 2021 December 31, 2020 Securities on deposit for regulatory and other purposes $ 195.6 $ 227.5 Securities pledged as collateral for letters of credit and other 193.9 189.4 Securities and cash on deposit supporting Lloyd’s business (1) 296.8 409.2 Total restricted investments $ 686.3 $ 826.1 (1) Argo Group is required to maintain “Funds at Lloyd’s” or “FAL” to support its business for Syndicate 1200 and Syndicate 1910. At December 31, 2021 the amount pledged for FAL was $296.8 million, of which $140.3 million was provided by Argo Re.
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) December 31, 2021 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities U.S. Governments $ 425.0 $ 417.4 $ 7.6 $ — Foreign Governments 232.8 — 232.8 — Obligations of states and political subdivisions 171.3 — 171.3 — Corporate bonds 1,983.3 — 1,980.5 2.8 Commercial mortgage-backed securities 418.7 — 418.7 — Residential mortgage-backed securities 482.5 — 482.5 — Asset-backed securities 173.6 — 173.6 — Collateralized loan obligations 336.1 — 336.1 — Total fixed maturities 4,223.3 417.4 3,803.1 2.8 Equity securities 56.3 41.6 — 14.7 Other investments 75.4 — 75.4 — Short-term investments 655.8 653.9 1.9 — $ 5,010.8 $ 1,112.9 $ 3,880.4 $ 17.5 (a) Quoted prices in active markets for identical asset (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 Governments 294.8 — 294.8 — Obligations of states and political subdivisions 170.4 — 170.4 — Corporate bonds 1,981.8 — 1,974.8 7.0 Commercial mortgage-backed securities 339.7 — 339.7 — Residential mortgage-backed securities 508.2 — 508.2 — Asset-backed securities 122.8 — 122.8 — Collateralized loan obligations 289.6 — 289.6 — Total fixed maturities 4,107.1 383.5 3,716.6 7.0 Equity securities 176.7 159.2 — 17.5 Other investments 102.5 0.4 102.1 — Short-term investments 542.6 526.5 16.1 — $ 4,928.9 $ 1,069.6 $ 3,834.8 $ 24.5 (a) Quoted prices in active markets for identical asset (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) Credit Financial Equity Total Beginning balance, January 1, 2021 $ 7.0 $ 17.5 $ 24.5 Transfers into Level 3 — 1.0 1.0 Transfers out of Level 3 — — — Total gains or losses (realized/unrealized): Included in net income — 4.2 4.2 Included in other comprehensive income (0.8) — (0.8) Purchases, issuances, sales, and settlements: Purchases 0.1 1.2 1.3 Issuances — — — Sales (3.5) (10.6) (14.1) Settlements — — — Ending balance, December 31, 2021 $ 2.8 $ 13.3 $ 16.1 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, 2021 $ — $ — $ — (in millions) Credit Financial Equity 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: Purchases 0.1 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 $ — $ — $ —

Allowance for Credit Losses (Ta

Allowance for Credit Losses (Tables)	12 Months Ended
	Dec. 31, 2021
Credit Loss [Abstract]
Premium Receivable, Allowance for Credit Loss	The following table represents the balances of premiums receivable, net of allowance for uncollectible premiums, including expected credit losses, at December 31, 2021 and January 1, 2021, and the changes in the allowance for the year ended December 31, 2021. (in millions) Premiums Receivable, Net of Allowance for Estimated Uncollectible Premiums Allowance for Estimated Uncollectible Premiums Balance, January 1, 2021 $ 679.8 $ 9.4 Current period change for estimated uncollectible premiums (3.1) Write-offs of uncollectible premiums receivable (0.6) Foreign exchange adjustments — Balance, December 31, 2021 $ 648.6 $ 5.7
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, including expected credit losses, at December 31, 2021 and January 1, 2021, and changes in the allowance for estimated uncollectible reinsurance for the year ended December 31, 2021. (in millions) Reinsurance Recoverables, Net of Allowance for Estimated Uncollectible Reinsurance Allowance 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, December 31, 2021 $ 2,966.4 $ 3.8

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Schedule of Lease Components	The components of lease expense, and other lease information, as of and during the year ended December 31, 2021 and 2020 are as follows: December 31, (in millions) 2021 2020 Operating leases right-of-use assets $ 81.4 $ 82.0 Operating lease liabilities 97.7 95.8 Operating lease weighted-average remaining lease term 9.51 10.50 Operating lease weighted-average discount rate 3.53 % 3.77 %
Schedule of Lease Cost	For the Year Ended December 31, (in millions) 2021 2020 Operating lease costs $ 14.2 $ 15.3 Variable lease costs 6.2 5.4 Sublease income (2.1) (0.4) Total lease costs $ 18.3 $ 20.3 Operating cash flows from operating leases (fixed payments) $ 14.9 $ 15.7 Operating cash flows from operating leases (liability reduction) $ 12.8 $ 12.8
Schedule of Operating Lease Maturity	Future minimum lease payments under operating leases as of December 31, 2021 were as follows: December 31, (in millions) 2021 2022 13.8 2023 13.4 2024 11.8 2025 11.6 2026 11.2 Thereafter 54.4 Total future minimum lease payments $ 116.2 Future lease obligations Less imputed interest (18.5) Total operating lease liability $ 97.7

Reinsurance (Tables)

Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2021
Insurance [Abstract]
Schedule of Reinsurance Premiums	Premiums were as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Direct written premiums $ 2,990.6 $ 2,676.1 $ 2,510.4 Reinsurance ceded to other companies (1,203.9) (1,423.2) (1,375.6) Reinsurance assumed from other companies 190.6 557.2 619.8 Net written premiums $ 1,977.3 $ 1,810.1 $ 1,754.6 Direct earned premiums $ 2,917.7 $ 2,660.6 $ 2,412.4 Reinsurance ceded to other companies (1,272.7) (1,388.6) (1,286.7) Reinsurance assumed from other companies 265.1 508.5 604.0 Net earned premiums $ 1,910.1 $ 1,780.5 $ 1,729.7 Percentage of reinsurance assumed to net earned premiums 13.9 % 28.6 % 34.9 %

Reserves for Losses and Loss _2

Reserves for Losses and Loss Adjustment Expenses (Tables)	12 Months Ended
	Dec. 31, 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 Years Ended December 31, (in millions) 2021 2020 2019 Net reserves beginning of the year $ 2,906.1 $ 2,722.7 $ 2,562.9 Net AIL reserves acquired — 27.9 — Add: Losses and LAE incurred during current calendar year, net of reinsurance: Current accident year 1,176.3 1,201.1 1,082.6 Prior accident years 138.3 7.7 138.1 Losses and LAE incurred during calendar year, net of reinsurance 1,314.6 1,208.8 1,220.7 Deduct: Losses and LAE payments made during current calendar year, net of reinsurance: Current accident year 180.8 253.4 224.3 Prior accident years 688.4 866.4 806.0 Losses and LAE payments made during current calendar year, net of reinsurance: 869.2 1,119.8 1,030.3 Net reserve ceded - reinsurance to close transaction for years of account 2017 and prior (1) 219.7 — — Change in participation interest (2) 8.4 32.8 (14.4) Foreign exchange adjustments (17.0) 33.7 (16.2) Net reserves - end of period 3,123.2 2,906.1 2,722.7 Add: Reinsurance recoverables on unpaid losses and LAE, end of period 2,471.8 2,499.9 2,434.9 Gross reserves - end of period $ 5,595.0 $ 5,406.0 $ 5,157.6 (1) Amount represents a decrease in reserves due to an RITC to RiverStone, see Note 2, recent acquisitions, disposals & other transactions. (2) Amount represents (decrease) increase in reserves due to change in our Syndicate 1200 and Syndicate 1910 participation.
Impact from (Favorable) Unfavorable Development of Prior Accident Years’ Loss and LAE Reserves on Each Reporting Segment	The impact from the unfavorable (favorable) development of prior accident years’ losses and LAE reserves on each reporting segment is presented below: For the Years Ended December 31, (in millions) 2021 2020 2019 U.S. Operations $ 120.9 $ 2.4 $ 15.7 International Operations (26.9) (6.2) 110.4 Run-off Lines 44.3 11.5 12.0 Total (favorable) unfavorable prior-year development $ 138.3 $ 7.7 $ 138.1
Summary of Information About Incurred and Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	The following tables provide information about incurred and cumulative paid losses and allocated loss adjustment expenses (“ALAE”), net of reinsurance. The following tables also include IBNR reserves plus expected development on reported claims and the cumulative number of reported claims as of December 31, 2021. Reporting Segment: U.S. Operations Line of Business: Liability (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 329.9 $ 342.3 $ 339.3 $ 336.9 $ 335.9 $ 329.7 $ 328.9 $ 327.2 $ 328.2 $ 329.3 2013 344.5 355.8 361.0 360.4 351.5 346.6 343.1 344.8 357.3 2014 328.6 337.1 330.0 326.3 323.9 321.9 327.4 341.3 2015 339.8 343.8 330.3 328.7 328.0 335.4 347.9 2016 342.6 350.5 342.4 353.0 355.3 379.0 2017 374.8 373.7 384.3 397.7 431.7 2018 426.1 430.4 414.5 420.4 2019 421.1 423.7 427.1 2020 404.2 386.7 2021 416.5 Total $ 3,837.2 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 37.3 $ 103.8 $ 169.8 $ 226.6 $ 263.2 $ 285.3 $ 295.4 $ 305.3 $ 313.2 $ 315.7 2013 36.5 109.7 174.3 228.8 266.5 289.3 306.9 318.2 325.4 2014 32.4 91.0 154.6 206.9 240.6 266.3 283.2 291.4 2015 33.7 86.9 140.2 195.6 236.4 263.9 289.3 2016 28.5 84.5 144.1 217.1 255.6 293.8 2017 27.8 83.0 158.8 238.5 295.2 2018 34.3 98.9 175.8 245.5 2019 32.4 113.6 186.1 2020 25.6 85.9 2021 27.6 Total $ 2,355.9 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance 59.4 Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 1,540.7 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 329.3 $ 35.6 27,587 2013 357.3 48.4 27,258 2014 341.3 56.3 23,473 2015 347.9 54.2 21,729 2016 379.0 60.7 18,693 2017 431.7 102.3 20,868 2018 420.4 117.0 23,150 2019 427.1 181.8 22,270 2020 386.7 261.2 17,001 2021 416.5 366.6 11,344 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. (2) During 2021, the Company revised the manner in which it measures reported claims. The cumulative number of reported claims is measured by individual claimant at a coverage level. Reported occurrences that do not result in a liability are included as reported claims. During 2021, we implemented additional processes to consolidate multiple data sources for U.S. Operations reserving. As part of that process, the level of detail used to determine the number of reported claims for some of the business units in US Operations changed. As a result, the cumulative number of reported claims for each accident year presented above as of December 31, 2021 is not comparable to the cumulative number of reported claims disclosed in previously issued financial statements. Reporting Segment: U.S. Operations Line of Business: Professional (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 27.8 $ 28.3 $ 28.6 $ 25.8 $ 24.0 $ 24.5 $ 24.9 $ 24.7 $ 24.4 $ 24.3 2013 20.9 21.5 21.1 19.0 19.8 19.5 18.3 18.1 18.0 2014 22.4 22.4 26.0 33.7 36.2 35.4 35.1 34.4 2015 29.9 29.5 33.2 34.0 37.1 37.9 38.3 2016 44.2 44.8 45.1 42.9 35.5 43.0 2017 60.1 61.8 78.3 87.9 99.5 2018 70.8 73.2 79.2 94.8 2019 94.4 96.8 105.0 2020 152.6 142.6 2021 177.9 Total 777.8 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 2.3 $ 8.6 $ 16.9 $ 19.9 $ 21.4 $ 22.6 $ 23.5 $ 24.2 $ 24.0 $ 24.3 2013 1.9 6.3 10.9 14.2 17.6 17.5 17.9 17.9 17.9 2014 2.3 5.4 15.1 24.1 25.5 32.3 33.3 33.6 2015 1.8 8.3 15.6 20.8 26.2 31.3 31.7 2016 2.4 11.9 24.6 28.9 30.8 34.4 2017 3.5 24.9 38.0 59.7 77.9 2018 4.5 16.7 43.8 62.6 2019 4.9 32.9 50.0 2020 13.3 36.4 2021 12.1 Total $ 380.9 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance 14.4 Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 411.3 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 24.3 $ 0.1 642 2013 18.0 0.1 625 2014 34.4 0.1 1,044 2015 38.3 2.2 1,831 2016 43.0 (0.1) 3,256 2017 99.5 4.2 3,759 2018 94.8 (0.5) 4,303 2019 105.0 22.5 5,091 2020 142.6 78.7 5,389 2021 177.9 149.2 5,208 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. (2) During 2021, the Company revised the manner in which it measures reported claims. The cumulative number of reported claims is measured by individual claimant at a coverage level. Reported occurrences that do not result in a liability are included as reported claims. During 2021, we implemented additional processes to consolidate multiple data sources for U.S. Operations reserving. As part of that process, the level of detail used to determine the number of reported claims for some of the business units in US Operations changed. As a result, the cumulative number of reported claims for each accident year presented above as of December 31, 2021 is not comparable to the cumulative number of reported claims disclosed in previously issued financial statements. Reporting Segment: U.S. Operations Line of Business: Property (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 103.8 $ 101.8 $ 98.7 $ 98.8 $ 98.5 $ 98.7 $ 98.7 $ 98.6 $ 98.6 $ 97.4 2013 74.5 79.9 78.7 78.2 77.8 78.2 78.4 78.2 77.2 2014 80.4 82.2 77.0 77.1 76.9 76.9 76.1 76.0 2015 74.0 73.4 69.9 68.9 69.1 69.2 69.2 2016 59.4 57.6 57.1 56.6 56.6 56.5 2017 75.2 79.6 86.9 94.9 94.5 2018 89.2 93.1 95.1 96.9 2019 91.4 88.8 98.4 2020 129.5 133.2 2021 111.7 Total $ 911.0 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 70.1 $ 97.2 $ 98.0 $ 98.2 $ 98.4 $ 98.4 $ 98.7 $ 98.6 $ 98.6 $ 97.4 2013 52.5 73.2 75.5 77.4 77.1 75.9 78.1 78.2 77.2 2014 51.6 73.1 75.7 76.4 76.3 76.4 76.1 76.0 2015 44.6 67.6 68.6 67.9 68.3 68.5 69.0 2016 39.4 55.2 55.8 56.1 56.4 56.3 2017 54.4 95.3 113.9 100.8 88.4 2018 61.3 126.7 107.0 98.8 2019 55.8 82.4 90.9 2020 75.9 116.6 2021 71.3 Total 841.9 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance (0.3) Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 68.8 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 97.4 $ 6.3 15,005 2013 77.2 0.9 10,717 2014 76.0 0.5 8,559 2015 69.2 0.8 7,746 2016 56.5 2.0 7,999 2017 94.5 — 10,388 2018 96.9 (12.9) 11,145 2019 98.4 2.1 11,724 2020 133.2 (9.3) 11,504 2021 111.7 (0.6) 9,265 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. (2) During 2021, the Company revised the manner in which it measures reported claims. The cumulative number of reported claims is measured by individual claimant at a coverage level. Reported occurrences that do not result in a liability are included as reported claims. During 2021, we implemented additional processes to consolidate multiple data sources for U.S. Operations reserving. As part of that process, the level of detail used to determine the number of reported claims for some of the business units in US Operations changed. As a result, the cumulative number of reported claims for each accident year presented above as of December 31, 2021 is not comparable to the cumulative number of reported claims disclosed in previously issued financial statements. Reporting Segment: U.S. Operations Line of Business: Specialty (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 7.5 $ 6.7 $ 4.9 $ 4.3 $ 4.0 $ 3.9 $ 3.5 $ 3.6 $ 3.3 $ 3.3 2013 10.0 8.6 4.6 2.5 1.7 0.9 0.9 0.9 0.9 2014 13.1 13.1 8.9 6.0 4.8 4.6 4.6 4.1 2015 14.8 14.3 9.5 5.5 1.2 0.5 0.3 2016 15.0 15.0 11.2 6.2 4.7 3.3 2017 16.2 16.2 7.6 0.9 0.7 2018 20.9 17.4 3.3 3.5 2019 22.7 8.5 5.6 2020 25.4 10.3 2021 27.9 Total $ 59.9 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 3.6 $ 3.3 $ 3.3 $ 3.3 $ 3.3 $ 3.4 $ 3.3 $ 3.4 $ 3.4 $ 3.4 2013 0.4 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 2014 1.1 3.3 4.0 4.0 4.1 4.1 4.0 4.1 2015 0.2 0.1 0.2 0.3 0.3 0.3 0.3 2016 1.3 1.6 2.2 2.2 2.2 2.8 2017 0.3 0.1 — 0.1 0.2 2018 — 0.7 1.7 1.2 2019 0.7 0.7 3.2 2020 0.3 7.6 2021 0.3 Total 24.0 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance 0.6 Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 36.5 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 3.3 $ — 121 2013 0.9 0.1 47 2014 4.1 — 45 2015 0.3 — 24 2016 3.3 0.9 56 2017 0.7 1.0 106 2018 3.5 2.6 142 2019 5.6 0.6 233 2020 10.3 2.3 409 2021 27.9 26.5 427 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. (2) During 2021, the Company revised the manner in which it measures reported claims. The cumulative number of reported claims is measured by individual claimant at a coverage level. Reported occurrences that do not result in a liability are included as reported claims. During 2021, we implemented additional processes to consolidate multiple data sources for U.S. Operations reserving. As part of that process, the level of detail used to determine the number of reported claims for some of the business units in US Operations changed. As a result, the cumulative number of reported claims for each accident year presented above as of December 31, 2021 is not comparable to the cumulative number of reported claims disclosed in previously issued financial statements. Reporting Segment: International Operations Operating Division: Argo Insurance Bermuda Line of Business: Liability (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ 7.4 $ 7.4 $ 7.4 $ 5.6 $ 4.4 $ 1.7 $ — $ 0.6 $ 0.6 $ 0.6 2013 8.5 8.5 8.5 8.5 4.9 2.2 5.3 5.3 6.0 2014 9.8 9.8 9.8 6.2 1.5 2.3 2.3 1.6 2015 11.3 14.3 24.8 35.4 45.4 45.1 51.3 2016 13.9 14.0 14.0 6.6 6.1 0.8 2017 17.1 17.3 26.9 30.3 37.3 2018 8.9 32.1 26.6 24.2 2019 13.3 13.6 13.8 2020 23.3 24.9 2021 12.3 Total $ 172.8 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — 2.3 2.3 2.3 2.4 2.4 2014 — — 0.1 0.1 1.2 1.2 1.4 1.4 2015 — — 16.1 20.3 26.6 34.8 38.9 2016 — — — 0.1 0.1 0.2 2017 — 3.3 3.4 18.0 19.7 2018 — 13.8 18.3 18.5 2019 — 0.1 0.7 2020 0.8 7.0 2021 — Total $ 88.8 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance — Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 84.0 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims Cumulative Number of Reported Claims (2) 2012 $ 0.6 $ 0.5 1,392 2013 6.0 0.7 1,200 2014 1.6 (0.4) 1,350 2015 51.3 — 1,613 2016 0.8 0.5 1,943 2017 37.3 10.4 2,129 2018 24.2 5.2 1,110 2019 13.8 12.7 1,168 2020 24.9 16.6 1,267 2021 12.3 12.3 1,053 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. (2) The cumulative number of reported claims is measured by individual claimant at a coverage level. Reported occurrences that do not result in a liability are included as reported claims. Reporting Segment: International Operations Operating Division: Syndicate 1200 Line of Business: Liability (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — — — — — — 2014 — — — — — — — — 2015 — — — — — — — 2016 — — — — — — 2017 — — — — — 2018 17.8 19.6 19.5 19.9 2019 14.6 15.7 15.2 2020 15.2 14.6 2021 15.8 Total $ 65.5 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — — — — — — 2014 — — — — — — — — 2015 — — — — — — — 2016 — — — — — — 2017 — — — — — 2018 0.6 2.5 5.9 6.1 2019 1.4 4.6 5.2 2020 1.1 1.5 2021 0.2 Total $ 13.0 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance 3.7 Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 56.2 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims 2012 $ — $ — 2013 — — 2014 — — 2015 — — 2016 — — 2017 — — 2018 19.9 5.0 2019 15.2 5.3 2020 14.6 8.0 2021 15.8 12.7 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. Reporting Segment: International Operations Operating Division: Syndicate 1200 Line of Business: Professional (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — — — — — — 2014 — — — — — — — — 2015 — — — — — — — 2016 — — — — — — 2017 — — — — — 2018 13.7 14.4 15.3 15.5 2019 19.5 20.9 20.2 2020 25.0 25.0 2021 24.9 Total $ 85.6 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — — — — — — 2014 — — — — — — — — 2015 — — — — — — — 2016 — — — — — — 2017 — — — — — 2018 0.1 1.8 4.5 4.6 2019 2.7 8.7 9.1 2020 2.2 3.1 2021 0.7 Total $ 17.5 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance 10.5 Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 78.6 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims 2012 $ — $ — 2013 — — 2014 — — 2015 — — 2016 — — 2017 — — 2018 15.5 4.6 2019 20.2 7.1 2020 25.0 12.0 2021 24.9 20.0 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. Reporting Segment: International Operations Operating Division: Syndicate 1200 Line of Business: Property (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — — — — — — 2014 — — — — — — — — 2015 — — — — — — — 2016 — — — — — — 2017 — — — — — 2018 19.7 21.8 21.7 22.1 2019 37.2 40.1 38.7 2020 62.8 60.3 2021 113.5 Total $ 234.6 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — — — — — — 2014 — — — — — — — — 2015 — — — — — — — 2016 — — — — — — 2017 — — — — — 2018 1.5 6.1 14.4 14.8 2019 9.5 31.9 36.0 2020 20.0 29.1 2021 15.6 Total $ 95.5 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance — Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 139.1 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims 2012 $ — $ — 2013 — — 2014 — — 2015 — — 2016 — — 2017 — — 2018 22.1 0.2 2019 38.7 1.2 2020 60.3 6.0 2021 113.5 68.1 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited. Reporting Segment: International Operations Operating Division: Syndicate 1200 Line of Business: Specialty (in millions, except number of claims reported) Incurred Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — — — — — — 2014 — — — — — — — — 2015 — — — — — — — 2016 — — — — — — 2017 — — — — — 2018 43.8 53.8 55.0 53.0 2019 66.5 84.0 80.5 2020 109.8 108.2 2021 72.6 Total $ 314.3 Cumulative Paid Losses & ALAE, Net of Reinsurance Accident For the Years Ended December 31, 2012 (1) 2013 (1) 2014 (1) 2015 (1) 2016 (1) 2017 (1) 2018 (1) 2019 (1) 2020 (1) 2021 (1) 2012 $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — 2013 — — — — — — — — — 2014 — — — — — — — — 2015 — — — — — — — 2016 — — — — — — 2017 — — — — — 2018 3.0 23.8 32.7 25.5 2019 31.3 65.8 65.8 2020 27.7 42.9 2021 9.7 Total $ 143.9 Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance — Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance $ 170.4 As of December 31, 2021 Accident Year Incurred Losses & ALAE, Net of Reinsurance IBNR & Expected Development on Reported Claims 2012 $ — $ — 2013 — — 2014 — — 2015 — — 2016 — — 2017 — — 2018 53.0 2.2 2019 80.5 5.1 2020 108.2 19.8 2021 72.6 37.8 (1) Information presented for calendar years prior to 2021 is required supplementary information and is unaudited.
Summary of Reconciliation of Net Incurred and Paid Development to Liability for Unpaid Losses and LAE in Consolidated Balance Sheets	The reconciliation of the net incurred and paid development tables to the liability for unpaid losses and LAE in our consolidated balance sheets is as follows: (in millions) As of December 31, 2021 Liabilities for unpaid losses and ALAE: US Operations: Liability $ 1,540.7 Professional 411.3 Property 68.8 Specialty 36.5 International Operations: Argo Insurance Bermuda- Liability 84.0 Syndicate 1200 - Liability 56.2 Syndicate 1200 - Professional 78.6 Syndicate 1200 - Property 139.1 Syndicate 1200 - Specialty 170.4 Run-off Lines 183.4 Other lines 302.6 Total liabilities for unpaid losses and ALAE, net of reinsurance 3,071.6 Reinsurance recoverables on unpaid losses and LAE: US Operations: Liability 825.4 Professional 251.3 Property 206.9 Specialty 11.4 International Operations: Argo Insurance Bermuda- Liability 207.6 Syndicate 1200 - Liability 30.8 Syndicate 1200 - Professional 74.6 Syndicate 1200 - Property 102.6 Syndicate 1200 - Specialty 103.3 Run-off Lines 82.5 Other lines 575.4 Total reinsurance recoverables on unpaid losses and LAE 2,471.8 Unallocated loss adjustment expenses 70.4 Unamortized reserve discount (18.8) Gross liability for unpaid losses and LAE $ 5,595.0
Schedule of Supplementary Unaudited Information About Annual Percentage Payout of Incurred Losses and ALAE, Net of Reinsurance	The following table provides supplementary unaudited information about the annual percentage payout of incurred losses and ALAE, net of reinsurance, as of December 31, 2021: Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance (1) Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Remainder U.S. Operations: US Liability 8.9% 17.6% 18.2% 18.3% 11.5% 8.3% 5.2% 3.6% 2.4% 1.7% 4.3% US Professional 6.1% 19.1% 22.0% 18.6% 12.5% 8.9% 5.5% 3.2% 1.8% 1.0% 1.2% US Property 58.4% 32.5% 5.7% 2.3% 0.7% 0.2% 0.1% —% —% —% —% US Specialty 52.7% 22.8% 19.2% 3.4% 1.2% 0.4% 0.1% 0.1% —% —% —% International Operations: Bermuda Insurance Liability 0.6% 14.2% 12.7% 13.2% 12.2% 10.5% 8.6% 6.8% 5.3% 4.0% 11.9% S1200 Liability 6.3% 11.5% 13.4% 15.0% 16.0% 11.7% 6.9% 5.2% 3.7% 2.7% 7.6% S1200 Professional 7.3% 12.5% 18.5% 17.6% 12.4% 8.7% 5.9% 4.5% 3.2% 2.3% 7.1% S1200 Property 33.8% 39.2% 14.3% 8.4% 2.7% 0.8% 0.4% 0.2% 0.1% —% 0.1% S1200 Specialty 32.0% 36.4% 16.7% 9.2% 3.0% 1.5% 0.6% 0.3% 0.1% —% —% (1) The average annual percentage payout is calculated from a paid losses and ALAE development pattern based on an actuarial analysis of the paid losses and ALAE movements by accident year for each disaggregation category. The paid losses and ALAE development pattern provides the expected percentage of ultimate losses and ALAE to be paid in each year. The pattern considers all accident years included in the claims development tables .
Schedule of Information About Discounted Liabilities for Unpaid Losses and LAE	The following tables provide information about these discounted liabilities for unpaid losses and LAE: Carrying Amount of Reserves for Losses & LAE Aggregate Amount of Discount As of December 31, As of December 31, (in millions, except discount percentages) 2021 2020 2019 2021 2020 2019 US Operations: Commercial Specialty - Liability $ 163.1 $ 150.4 $ 153.1 $ 14.1 $ 12.9 $ 13.0 Run-off Lines 114.3 128.4 148.9 4.7 4.9 4.9 Total $ 277.4 $ 278.8 $ 302.0 $ 18.8 $ 17.8 $ 17.9 Interest Accretion (1) Discount Rate For the Years Ended December 31, As of December 31, 2021 2020 2019 2021 2020 2019 US Operations: Commercial Specialty - Liability $ 0.9 $ 1.9 $ 1.3 2.25% 2.25% 2.25% Run-off Lines 0.2 — 0.2 3.50% 3.50% 3.50% Total $ 1.1 $ 1.9 $ 1.5 (1) Interest accretion is recorded in the line item “Losses and loss adjustment expenses” in our Consolidated Statements of Income (Loss).

Run-off Lines (Tables)

Run-off Lines (Tables)	12 Months Ended
	Dec. 31, 2021
Discontinued Operations and Disposal Groups [Abstract]
Gross Reserves for Run-Off Lines	The following table presents our gross reserves for Run-off Lines as of December 31: December 31, (in millions) 2021 2020 Asbestos and Environmental: Reinsurance assumed $ 29.6 $ 29.4 Other 34.2 29.9 Total Asbestos and Environmental 63.8 59.3 Risk-management 162.6 162.4 Run-off reinsurance lines 0.5 0.5 Other run-off lines 34.3 14.3 Gross reserves - Run-off Lines $ 261.2 $ 236.5
Total Gross Reserves for Asbestos Exposure	The following table represents the total gross reserves for our asbestos exposure: December 31, (in millions) 2021 2020 2019 Direct written Case reserves $ 3.0 $ 3.1 $ 2.7 Unallocated loss adjustment expense ("ULAE") 0.5 0.5 0.5 Incurred but not reported ("IBNR") 19.9 20.2 16.1 Total direct written reserves 23.4 23.8 19.3 Assumed domestic Case reserves 7.4 8.4 9.1 ULAE 0.8 0.8 0.8 IBNR 11.9 12.8 11.2 Total assumed domestic reserves 20.1 22.0 21.1 Assumed London Case reserves 2.1 1.4 1.3 IBNR 2.3 1.6 1.1 Total assumed London reserves 4.4 3.0 2.4 Total asbestos reserves $ 47.9 $ 48.8 $ 42.8
Underwriting Losses for Run-Off Lines	The following table presents our underwriting losses for Run-off Lines: For the Years Ended December 31, (in millions) 2021 2020 2019 Asbestos and Environmental: Reinsurance assumed $ (4.7) $ (5.7) $ (4.4) Other (10.0) (11.7) (3.9) Total Asbestos and Environmental (14.7) (17.4) (8.3) Risk-management (9.9) 7.6 (4.9) Run-off reinsurance lines — 0.4 0.7 Other run-off lines (20.1) (3.4) (1.7) Total underwriting loss - Run-off Lines $ (44.7) $ (12.8) $ (14.2)

Long-term Debt (Tables)

Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Schedule Of Unamortized Debt Issuance Costs Deducted From Carrying Value Of Debt Liability	At December 31, 2021 and 2020, the Notes consisted of the following: (in millions) December 31, 2021 December 31, 2020 Senior unsecured fixed rate notes Principal $ 143.8 $ 143.8 Less: unamortized debt issuance costs (3.5) (3.6) Senior unsecured fixed rate notes, less unamortized debt issuance costs $ 140.3 $ 140.2
Schedule of Long-term Debt	A summary of our outstanding junior subordinated debentures is presented below: December 31, 2021 (in millions) Issue Date Trust Preferred Pools Maturity Rate Structure Interest Rate at December 31, 2021 Amount Argo Group 5/15/2003 PXRE Capital Statutory Trust II 5/15/2033 3M LIBOR + 4.10% 4.26% $ 18.0 11/6/2003 PXRE Capital Trust VI 9/30/2033 3M LIBOR + 3.90% 4.12% 10.3 Argo Group US 5/15/2003 Argonaut Group Statutory Trust I 5/15/2033 3M LIBOR + 4.10% 4.26% 15.5 12/16/2003 Argonaut Group Statutory Trust III 1/8/2034 3M LIBOR + 4.10% 4.22% 12.3 4/29/2004 Argonaut Group Statutory Trust IV 4/29/2034 3M LIBOR + 3.85% 4.00% 13.4 5/26/2004 Argonaut Group Statutory Trust V 5/24/2034 3M LIBOR + 3.85% 4.02% 12.4 5/12/2004 Argonaut Group Statutory Trust VI 6/17/2034 3M LIBOR + 3.80% 4.02% 13.4 9/17/2004 Argonaut Group Statutory Trust VII 12/15/2034 3M LIBOR + 3.60% 3.80% 15.5 9/22/2004 Argonaut Group Statutory Trust VIII 9/22/2034 3M LIBOR + 3.55% 3.76% 15.5 10/22/2004 Argonaut Group Statutory Trust IX 12/15/2034 3M LIBOR + 3.60% 3.80% 15.5 9/14/2005 Argonaut Group Statutory Trust X 9/15/2035 3M LIBOR + 3.40% 3.60% 30.9 Total Outstanding $ 172.7 December 31, 2020 (in millions) Issue Date Trust Preferred Pools Maturity Rate Structure Interest Rate at December 31, 2020 Amount Argo Group 5/15/2003 PXRE Capital Statutory Trust II 5/15/2033 3M LIBOR + 4.10% 4.32% $ 18.0 11/6/2003 PXRE Capital Trust VI 9/30/2033 3M LIBOR + 3.90% 4.15% 10.3 Argo Group US 5/15/2003 Argonaut Group Statutory Trust I 5/15/2033 3M LIBOR + 4.10% 4.32% 15.5 12/16/2003 Argonaut Group Statutory Trust III 1/8/2034 3M LIBOR + 4.10% 4.34% 12.3 4/29/2004 Argonaut Group Statutory Trust IV 4/29/2034 3M LIBOR + 3.85% 4.07% 13.4 5/26/2004 Argonaut Group Statutory Trust V 5/24/2034 3M LIBOR + 3.85% 4.05% 12.4 5/12/2004 Argonaut Group Statutory Trust VI 6/17/2034 3M LIBOR + 3.80% 4.03% 13.4 9/17/2004 Argonaut Group Statutory Trust VII 12/15/2034 3M LIBOR + 3.60% 3.82% 15.5 9/22/2004 Argonaut Group Statutory Trust VIII 9/22/2034 3M LIBOR + 3.55% 3.79% 15.5 10/22/2004 Argonaut Group Statutory Trust IX 12/15/2034 3M LIBOR + 3.60% 3.82% 15.5 9/14/2005 Argonaut Group Statutory Trust X 9/15/2035 3M LIBOR + 3.40% 3.62% 30.9 Total Outstanding $ 172.7 A summary of the terms of the acquired debt outstanding is presented below: (in millions) Issue Date Maturity Rate Structure Interest Rate at December 31, 2021 Principal at December 31, 2021 Carrying Value at December 31, 2021 9/13/2007 9/15/2037 3 month LIBOR + 3.15% 3.35 % $ 91.8 $ 85.5 (in millions) Issue Date Maturity Rate Structure Interest Rate at December 31, 2020 Principal at December 31, 2020 Carrying Value at December 31, 2020 9/13/2007 9/15/2037 3 month LIBOR + 3.15% 3.37 % $ 91.8 $ 85.1 (in millions) December 31, Debt Type 2021 2020 Floating rate loan stock $ 57.0 $ 60.7 Total other indebtedness $ 57.0 $ 60.7 (in millions) Currency Issue Date Maturity Rate Structure Interest Rate at December 31, 2021 Amount U.S. Dollar 12/8/2004 11/15/2034 6 month LIBOR + 4.2% 4.35% $ 6.5 U.S. Dollar 10/31/2006 1/15/2036 6 month LIBOR + 4.0% 4.15% 10.0 Total U.S. Dollar notes 16.5 Euro 9/6/2005 8/22/2035 3 month Euribor + 4.0% 3.44% 13.5 Euro 10/31/2006 11/22/2036 3 month Euribor + 4.0% 3.44% 11.8 Euro 6/8/2007 9/15/2037 3 month Euribor + 3.9% 3.30% 15.2 Total Euro notes 40.5 Total notes outstanding $ 57.0 (in millions) Currency Issue Date Maturity Rate Structure Interest Rate at December 31, 2020 Amount U.S. Dollar 12/8/2004 11/15/2034 6 month LIBOR + 4.2% 4.54% $ 6.5 U.S. Dollar 10/31/2006 1/15/2036 6 month LIBOR + 4.0% 4.34% 10.0 Total U.S. Dollar notes 16.5 Euro 9/6/2005 8/22/2035 3 month Euribor + 4.0% 3.47% 14.7 Euro 10/31/2006 11/22/2036 3 month Euribor + 4.0% 3.47% 12.9 Euro 6/8/2007 9/15/2037 3 month Euribor + 3.9% 3.36% 16.6 Total Euro notes 44.2 Total notes outstanding $ 60.7
Schedule of Outstanding Balance	The following table presents interest and maturities of long-term debt as of December 31, 2021: For the Years Ended (in millions) Total 2022 2023 2024 2025 2026 Thereafter Long-term debt: Junior subordinated debentures (1) 421.4 10.4 11.3 11.8 11.8 11.8 364.3 Senior unsecured fixed rate notes (2) 335.4 9.3 9.4 9.3 9.4 9.3 288.7 Floating rate loan stock (3) 88.6 2.1 2.2 2.2 2.2 2.2 77.7 (1) Interest only on Junior Subordinated Debentures through 2037. Interest calculated based on interest rate forecast. Principal due beginning May 2033. (2) Interest only on Senior Unsecured Fixed Rate Notes through 2042. Interest calculated based on the fixed rate of the notes. Principal due September 2042. (3) Interest only on Floating Rate Loan Stock through 2034. Interest calculated based on interest rate forecast. Principal due beginning November 2034.

Disclosures about Fair Value _2

Disclosures about Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 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: December 31, 2021 2020 (in millions) Carrying Fair Carrying Fair Junior subordinated debentures: Trust preferred debentures $ 172.7 $ 172.9 $ 172.7 $ 173.6 Subordinated debentures 85.5 91.9 85.1 92.3 Total junior subordinated debentures 258.2 264.8 257.8 265.9 Senior unsecured fixed rate notes 140.3 148.4 140.2 146.7 Floating rate loan stock 57.0 57.1 60.7 61.0 Based on an analysis of the inputs, our financial instruments measured at fair value on a recurring basis have been categorized as follows: Fair Value Measurements at Reporting Date Using (in millions) December 31, 2021 Level 1 (a) Level 2 (b) Level 3 (c) Junior subordinated debentures: Trust preferred debentures $ 172.9 $ — $ 172.9 $ — Subordinated debentures 91.9 — 91.9 — Total junior subordinated debentures 264.8 — 264.8 — Senior unsecured fixed rate notes 148.4 148.4 — — Floating rate loan stock 57.1 — 57.1 — 470.3 148.4 321.9 — (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) Junior subordinated debentures: Trust preferred debentures $ 173.6 $ — $ 173.6 $ — Subordinated debentures 92.3 — 92.3 — Total junior subordinated debentures 265.9 — 265.9 — Senior unsecured fixed rate notes 146.7 146.7 — — Floating rate loan stock 61.0 — 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

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Changes in Accumulated Other Comprehensive Income (Loss)	A summary of changes in accumulated other comprehensive income (loss), net of taxes (where applicable) by component for the year ended December 31, 2021 and 2020 is presented below: (in millions) Foreign Currency Translation Adjustments Unrealized Defined Benefit Pension Plans Total Balance, January 1, 2020 $ (22.6) $ 33.5 $ (8.1) $ 2.8 Other comprehensive income (loss) before reclassifications (15.3) 78.7 (0.5) 62.9 Amounts reclassified from accumulated other comprehensive loss — (12.8) — (12.8) Net current-period other comprehensive income (loss) (15.3) 65.9 (0.5) 50.1 Cumulative effect of adoption of ASU 2016-13 — 5.7 — 5.7 Balance, December 31, 2020 (37.9) 105.1 (8.6) 58.6 Other comprehensive (loss) income before reclassifications 2.6 (77.4) 1.5 (73.3) Amounts reclassified from accumulated other comprehensive income — (8.0) — (8.0) Net current-period other comprehensive (loss) income 2.6 (85.4) 1.5 (81.3) Balance, December 31, 2021 $ (35.3) $ 19.7 $ (7.1) $ (22.7)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	The amounts reclassified from accumulated other comprehensive (loss) income shown in the above table have been included in the following captions in our Consolidated Statements of Income (Loss): For the Years Ended December 31, (in millions) 2021 2020 2019 Unrealized gains and losses on securities: Net realized investment losses (gains) $ (12.2) $ (12.8) $ 9.9 (Benefit) provision for income taxes 4.2 — (1.2) Net of taxes $ (8.0) $ (12.8) $ 8.7

Net (Loss) Income Per Common _2

Net (Loss) Income Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Income Per Common Share on Basic and Diluted Basis	The following table presents the calculation of net (loss) income per common share on a basic and diluted basis: For the Years Ended December 31, (in millions, except number of shares and per share amounts) 2021 2020 2019 Net income (loss) $ 6.7 $ (54.1) $ (14.1) Less: Preferred share dividends 10.5 4.6 — Net loss attributable to common shareholders (3.8) (58.7) (14.1) Weighted average common shares outstanding - basic 34,816,160 34,614,813 34,205,954 Effect of dilutive securities: Equity compensation awards — — — Weighted average common shares outstanding - diluted 34,816,160 34,614,813 34,205,954 Net income (loss) per common share: Basic $ (0.11) $ (1.70) $ (0.41) Diluted $ (0.11) $ (1.70) $ (0.41)

Share-based Compensation (Table

Share-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Summary of Performance Share Activity	A summary of non-vested performance share activity as of December 31, 2021 and changes during the year then ended is as follows: Shares Weighted-Average Outstanding at January 1, 2021 157,847 $ 43.10 Granted 100,291 $ 54.79 Vested and issued (8,987) $ 44.49 Expired or forfeited (48,587) $ 48.74 Outstanding at December 31, 2021 200,564 $ 47.52
Summary of Restricted Share Activity	A summary of restricted share activity as of December 31, 2021 and changes during the year then ended is as follows: Shares Weighted-Average Outstanding at January 1, 2021 370,027 $ 44.22 Granted 168,011 $ 55.12 Vested and issued (143,744) $ 46.08 Expired or forfeited (115,864) $ 44.88 Outstanding at December 31, 2021 278,430 $ 49.57

Underwriting, Acquisition and_2

Underwriting, Acquisition and Insurance Expenses (Tables)	12 Months Ended
	Dec. 31, 2021
Underwriting Acquisition And Insurance Expenses [Abstract]
Underwriting, Acquisition and Insurance Expenses	Underwriting, acquisition and insurance expenses were as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Commissions $ 289.5 $ 268.0 $ 241.3 Other underwriting and insurance expenses 428.6 409.0 412.3 Total 718.1 677.0 653.6 Net deferral of policy acquisition costs (15.8) (9.3) 12.4 Total underwriting, acquisition and insurance expenses $ 702.3 $ 667.7 $ 666.0

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Tax Provision (Benefit) Expense	The following table presents the components of income tax provision (benefit) included in the amounts reported in our consolidated financial statements: For the Years Ended December 31, (in millions) 2021 2020 2019 Current income tax provision (benefit) related to: United States (Federal) $ 35.4 $ 28.0 $ 37.3 United States (State) $ 2.4 $ 1.4 $ 1.7 United Kingdom (2.2) (0.1) (1.5) Other jurisdictions 1.6 — (1) 0.1 Total current income tax provision 37.2 29.3 37.6 Deferred income tax provision (benefit) related to: United States (26.3) (5.1) (17.7) United Kingdom (12.3) (16.6) (5.8) Other jurisdictions — 0.1 — Total deferred income tax (benefit) (38.6) (21.6) (23.5) Income tax provision (benefit) $ (1.4) $ 7.7 $ 14.1 (1) Tax expense for the respective year was less than $0.1 million.
Schedule of Earned Premiums by Geographic Location	For the years ended December 31, 2021, 2020 and 2019, pre-tax income (loss) attributable to our operations and the operations’ effective tax rates were as follows: (in millions) 2021 2020 2019 Pre-Tax Effective Pre-Tax Effective Pre-Tax Effective Bermuda $ (18.0) — % $ (56.2) — % $ (34.7) — % United States 65.6 18.1 % 103.3 22.7 % 84.7 24.6 % United Kingdom (61.1) 24.4 % (100.6) 15.7 % (45.9) 14.9 % Barbados — (1) — % — (1) — % — (1) — % Belgium — — % 0.2 30.7 % — (1) 15.8 % Brazil 15.3 10.4 % 3.9 — % 5.2 — % United Arab Emirates 1.4 — % 2.1 — % 0.4 — % Ireland (0.2) — % 1.8 — % (0.1) — % Italy 1.4 — % 0.6 — % (7.4) — % Malta 0.9 — % (1.4) — % (2.0) — % Switzerland — (1) — % (0.1) — % (0.2) (0.2) % Pre-tax income (loss) $ 5.3 (26.4) % $ (46.4) (16.6) % $ — — % (2) (1) Pre-tax income for the respective year was less than $0.1 million. (2) Not meaningful.
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 (benefit) at the weighted average tax rate is as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Income tax provision (benefit) at expected rate $ 9.8 $ 4.0 $ 8.9 Tax effect of: Nontaxable investment income (0.5) (0.7) (1.2) Foreign exchange adjustments (0.7) 1.6 (0.1) Impairment of goodwill 8.2 1.0 2.9 Withholding taxes 0.1 0.1 0.2 Change in uncertain tax position liability (4.5) 0.7 1.4 Change in valuation allowance (0.7) 0.5 (1.8) Impact of change in tax rate related to Finance Act 2021 (8.3) — — Brazil Premiums and Underwriting (5.3) — — Other 0.5 0.5 3.8 Income tax provision (benefit) $ (1.4) $ 7.7 $ 14.1
Schedule of Net Deferred Tax Liability Comprises Tax Effect Related to Assets and Liabilities	The net deferred tax asset (liability) comprises the tax effects of temporary differences related to the following assets and liabilities: December 31, (in millions) 2021 2020 Deferred tax assets: Losses and loss adjustment expense reserve discounting $ 35.4 $ 29.2 Unearned premiums 27.0 25.9 Net operating loss carryforwards 31.6 27.9 Investment in limited partnership interests 21.1 7.8 Unrealized losses on equity securities 8.6 — Investments — 2.0 Right of use assets 13.5 12.7 Accrued bonus 5.8 6.3 Stock option expense 1.1 0.7 United Kingdom underwriting results 28.1 21.9 Other 10.6 9.6 Deferred tax assets, gross 182.8 144.0 Deferred tax liabilities: Unrealized gains on equity securities — (5.7) Unrealized gains on fixed maturities and other investment securities (4.8) (22.3) Unrealized gains on limited partnership interests (26.3) (14.7) Investments (5.1) — Depreciable fixed assets (7.9) (20.5) Deferred acquisition costs (21.3) (20.4) Lease liability (12.2) (11.7) TCJA reserve transitional liability (2.1) (2.7) Other (1.6) (0.7) Deferred tax liabilities, gross (81.3) (98.7) Deferred tax assets, net before valuation allowance $ 101.5 $ 45.3 Valuation allowance (27.9) (28.6) Deferred tax asset (liabilities), net $ 73.6 $ 16.7 Net deferred tax assets (liabilities) - Other jurisdictions $ 35.0 $ 21.4 Net deferred tax assets (liabilities) - United States 38.6 (4.7) Deferred tax asset (liabilities), net $ 73.6 $ 16.7
Schedule of Net Operating Loss Carryforwards Amounts by Jurisdiction and Year of Expiration	The NOL amounts by jurisdiction and year of expiration are as follows: (in millions) December 31, 2021 Expiration Net operating loss carryforwards by jurisdiction: Brazil 6.6 Indefinite Italy 48.4 Indefinite Malta 13.7 Indefinite United Kingdom 17.2 Indefinite United States 40.6 2025 - 2037
Schedule of Unrecognized Tax Benefits	The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits for the years ended December 31, 2021 and 2020: (in millions) 2021 2020 Balance at January 1 $ 8.2 $ 7.5 Additions for tax positions of prior years $ — — Reductions for tax positions of prior years (0.3) — Additions based on tax positions related to current year $ — 0.7 Reductions based on tax positions related to current year — — Reductions based on settlements with taxing authorities (2.8) — Expiration of statute of limitations (1.5) — Balance at December 31 $ 3.6 $ 8.2

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
Revenue and Income (Loss) Before Income Taxes for Each Segment	Revenue and income before income taxes for each segment were as follows: For the Years Ended December 31, (in millions) 2021 2020 2019 Revenue: Earned premiums U.S. Operations $ 1,283.7 $ 1,207.6 $ 1,119.9 International Operations 625.8 572.5 609.6 Run-off Lines 0.6 0.4 0.2 Total earned premiums 1,910.1 1,780.5 1,729.7 Net investment income U.S. Operations 119.4 80.3 100.0 International Operations 50.6 26.7 44.2 Run-off Lines 3.6 4.0 5.7 Corporate and Other 14.0 1.7 1.2 Total net investment income 187.6 112.7 151.1 Net realized investment gains (losses) 32.6 (3.6) 80.1 Total revenue $ 2,130.3 $ 1,889.6 $ 1,960.9 For the Years Ended December 31, (in millions) 2021 2020 2019 Income (loss) before income taxes U.S. Operations $ 61.1 $ 113.1 $ 139.3 International Operations 64.1 (75.3) (121.4) Run-off Lines (41.5) (9.6) (9.8) Total segment income before taxes 83.7 28.2 8.1 Corporate and Other (22.5) (34.5) (44.8) Net realized investment and other gains (losses) 32.6 (3.6) 80.1 Foreign currency exchange losses (1.6) (15.4) 9.8 Impairment of intangibles (43.2) — (15.6) Non-operating expense (43.7) (21.1) (37.6) Total income (loss) before income taxes $ 5.3 $ (46.4) $ —
Schedule of Earned Premiums by Geographic Location	The table below presents earned premiums by geographic location for the years ended December 31, 2021, 2020 and 2019. 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 Years Ended December 31, (in millions) 2021 2020 2019 United States $ 1,277.0 $ 1,205.0 $ 1,115.8 United Kingdom 475.3 361.1 391.5 Bermuda 54.8 96.5 80.7 Malta 35.4 59.5 85.0 All other jurisdictions 67.6 58.4 56.7 Total earned premiums $ 1,910.1 $ 1,780.5 $ 1,729.7
Identifiable Assets	The following table represents identifiable assets: December 31, (in millions) 2021 2020 U.S. Operations $ 5,800.1 $ 5,915.5 International Operations 3,932.3 3,911.9 Run-off Lines 314.7 337.3 Corporate and Other 270.7 301.1 Total $ 10,317.8 $ 10,465.8
Schedule of Goodwill and Intangible Assets Net of Accumulated Amortization	The following table represents goodwill and intangible assets, net of accumulated amortization, as of December 31, 2021 and 2020: Goodwill Intangible Assets, Net of (in millions) 2021 2020 2021 2020 U.S. Operations $ 118.6 $ 118.6 $ — $ — International Operations 28.7 28.7 17.3 60.5 Total $ 147.3 $ 147.3 $ 17.3 $ 60.5

Statutory Accounting Principl_2

Statutory Accounting Principles (Tables)	12 Months Ended
	Dec. 31, 2021
Statutory Accounting Principles [Abstract]
Statutory Capital and Surplus for Principal Operating Subsidiaries	The statutory capital and surplus for our principal operating subsidiaries was as follows: Statutory capital and surplus (1) December 31, (in millions) 2021 2020 Bermuda $ 1,425.8 $ 1,483.4 United Kingdom (2) 414.8 534.7 United States 1,177.2 1,072.1 (1) Such amounts include ownership interests in affiliate insurance and reinsurance subsidiaries. (2) Capital on deposit with Lloyd’s in U.S. dollars
Statutory Net Income (Loss) for Principal Operating Subsidiaries	The statutory net income (loss) for our principal operating subsidiaries was as follows: Statutory net income (loss) (1) For the Years Ended December 31, (in millions) 2021 2020 2019 Bermuda $ 14.2 $ (18.0) $ 7.1 United Kingdom (2) 8.6 (53.0) (15.1) United States 103.5 76.4 196.1 (1) Such amounts include ownership interests in affiliate insurance and reinsurance subsidiaries. (2) In U.S. dollars

Business and Significant Acco_4

Business and Significant Accounting Policies - Additional Information (Detail) $ in Millions	Nov. 25, 2020USD ($)	Apr. 30, 2020USD ($)	Nov. 30, 2021property	Dec. 31, 2021USD ($)segmentfoundationtrust	Dec. 31, 2020USD ($)property	Dec. 31, 2019USD ($)property	Oct. 01, 2021USD ($)	Dec. 31, 2018USD ($)
Business And Significant Accounting Policies [Line Items]
Number of reportable segments | segment				2
Percentage of contractual participation				100.00%
Number of statutory trusts | trust				11
Number of charitable foundations | foundation				1
Estimated liability for return of premiums				$ 4.7	$ 1.5
Estimated amount of premiums receivables due				0.1	0.1
Impairment of goodwill and intangibles					0	$ 15.6
Intangible assets derecognized				43.2	0	15.6
Amortization expense				0	1.1	1.7
Accumulated depreciation for property and equipment				158.8	163.3
Net book value of property and equipment				67.5	130.4
Depreciation expense				23.9	$ 24.1	$ 24.4
Number of properties held for sale | property						4
Number of properties sold | property			2		2
Assets held for sale				0	$ 7.7
Foreign currency translation adjustment gain (loss)				(35.3)	(37.9)
Shareholders' equity				(1,735.2)	(1,857.8)	$ (1,763.7)		$ (1,735)
ArgoGlobal Syndicate 1200
Business And Significant Accounting Policies [Line Items]
Carrying amount in excess of fair value				43.2
Impairment of goodwill and intangibles				28.7
Indefinite-lived intangible asset carrying value				17.3			$ 60.5
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Trident
Business And Significant Accounting Policies [Line Items]
Goodwill derecognized		$ 4.9
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Ariel Re
Business And Significant Accounting Policies [Line Items]
Goodwill derecognized	$ 9.2
Intangible assets derecognized	$ 30.2
Disposal Group, Held-for-sale, Not Discontinued Operations
Business And Significant Accounting Policies [Line Items]
Assets held for sale					7.7
Disposal Group, Held-for-sale, Not Discontinued Operations | Other Corporate Expense
Business And Significant Accounting Policies [Line Items]
Reclassification to "Assets held for sale" pretax gain (loss)				0.3	(0.8)	(3.7)
Retained Earnings
Business And Significant Accounting Policies [Line Items]
Shareholders' equity				(636.4)	(684.1)	(793.7)		(850.9)
AOCI Attributable to Parent
Business And Significant Accounting Policies [Line Items]
Shareholders' equity				$ 22.7	$ (58.6)	(2.8)		$ 78.1
Cumulative Effect, Period of Adoption, Adjustment
Business And Significant Accounting Policies [Line Items]
Shareholders' equity						2.2
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
Business And Significant Accounting Policies [Line Items]
Shareholders' equity						7.9
Cumulative Effect, Period of Adoption, Adjustment | AOCI Attributable to Parent
Business And Significant Accounting Policies [Line Items]
Shareholders' equity						$ (5.7)
Minimum
Business And Significant Accounting Policies [Line Items]
Useful life				3 years
Maximum
Business And Significant Accounting Policies [Line Items]
Useful life				39 years

Business and Significant Acco_5

Business and Significant Accounting Policies - Intangible Assets and Accumulated Amortization (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 69	$ 112.2
Accumulated Amortization	51.7	51.7
Lloyd's capacity
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	17.3	60.5
Distribution network
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	45.5	45.5
Accumulated Amortization	45.5	45.5
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6.2	6.2
Accumulated Amortization	$ 6.2	$ 6.2

Business and Significant Acco_6

Business and Significant Accounting Policies - Schedule of Interest Paid (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disclosure - Business and Significant Accounting Policies - Supplemental Cash Flow Information - Schedule of Interest Paid (Detail) [Line Items]
Total interest paid	$ 21.8	$ 26.4	$ 33.1
Income taxes paid	43	47.7	24
Income taxes recovered	(2.6)	(1.8)	(0.1)
Income taxes paid, net	40.4	45.9	23.9
Senior unsecured fixed rate notes
Disclosure - Business and Significant Accounting Policies - Supplemental Cash Flow Information - Schedule of Interest Paid (Detail) [Line Items]
Total interest paid	9.3	9.3	9.3
Junior subordinated debentures
Disclosure - Business and Significant Accounting Policies - Supplemental Cash Flow Information - Schedule of Interest Paid (Detail) [Line Items]
Total interest paid	10	11.9	16.2
Other indebtedness
Disclosure - Business and Significant Accounting Policies - Supplemental Cash Flow Information - Schedule of Interest Paid (Detail) [Line Items]
Total interest paid	$ 2.5	$ 5.2	$ 7.6

Recent Acquisitions, Disposal_2

Recent Acquisitions, Disposals & Other Transactions - Sale of Business Unit (Details) R$ in Millions, $ in Millions	Feb. 15, 2022USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Feb. 15, 2022BRL (R$)	Nov. 25, 2020USD ($)	Apr. 30, 2020USD ($)
Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, adjustment to carrying value of acquisition cost	$ 5.6
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Trident
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration received from sale						$ 38
Gain (loss) on disposal, pre-tax		$ 10.5	$ (31.8)
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Ariel Re
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration received from sale					$ 30
Gain (loss) on disposal, pre-tax			$ 9.4
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Argo Seguros Brasil S.A. | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration received from sale	30.5			R$ 160
Gain (loss) on disposal, pre-tax	6.3
Gain (loss) on disposal, other costs	$ 0.7

Recent Acquisitions, Disposal_3

Recent Acquisitions, Disposals & Other Transactions - Acquisitions (Details) - USD ($) $ in Millions	Jun. 12, 2020	Oct. 12, 2020
ArgoGlobal | RiverStone | ArgoGlobal Syndicate 1200
Business Acquisition [Line Items]
Reinsurance-to-close transaction, net technical provision		$ 219.7
Ariel Indemnity Limited
Business Acquisition [Line Items]
Percentage of capital stock acquired	100.00%
Consideration transferred	$ 55.6

Investments - Additional Inform

Investments - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)security	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Fair value of investments, assets managed on behalf of the trade capital providers | $	$ 89.6	$ 140.3
Number of securities in an unrealized loss position, total | security	5,207
Number of securities in an unrealized loss position for less than one year | security	697
Number of securities in an unrealized loss position for a period of one year or greater | security	82
Credit impairment losses | $	$ (0.6)	39.9	$ 0
Gain (Loss) on Investments
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Credit impairment losses | $	$ 0.6	$ (39.9)

Investments - Schedule of Amort

Investments - Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value of Investments (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Invested Assets [Line Items]
Amortized Cost	$ 4,203.2	$ 3,981.1
Allowance for Credit Losses	2.5	6.6	$ 0
Fair Value	4,223.3	4,107.1
Fixed maturities
Schedule of Invested Assets [Line Items]
Amortized Cost	4,203.2	3,981.1
Gross Unrealized Gains	63.4	149.7
Gross Unrealized Losses	40.8	17.1
Allowance for Credit Losses	2.5	6.6
Fair Value	4,223.3	4,107.1
Fixed maturities | U.S. Governments
Schedule of Invested Assets [Line Items]
Amortized Cost	422.7	385.4
Gross Unrealized Gains	5.5	14.7
Gross Unrealized Losses	3.2	0.3
Allowance for Credit Losses	0	0
Fair Value	425	399.8
Fixed maturities | Foreign Governments
Schedule of Invested Assets [Line Items]
Amortized Cost	234.7	284.1
Gross Unrealized Gains	2.2	11.6
Gross Unrealized Losses	3.9	0.7
Allowance for Credit Losses	0.2	0.2
Fair Value	232.8	294.8
Fixed maturities | Obligations of states and political subdivisions
Schedule of Invested Assets [Line Items]
Amortized Cost	166.7	163.1
Gross Unrealized Gains	5.8	7.7
Gross Unrealized Losses	1.2	0.3
Allowance for Credit Losses	0	0.1
Fair Value	171.3	170.4
Fixed maturities | Corporate bonds
Schedule of Invested Assets [Line Items]
Amortized Cost	1,972.3	1,925.9
Gross Unrealized Gains	33.5	75.3
Gross Unrealized Losses	20.3	13.3
Allowance for Credit Losses	2.2	6.1
Fair Value	1,983.3	1,981.8
Fixed maturities | Commercial mortgage-backed securities
Schedule of Invested Assets [Line Items]
Amortized Cost	416.7	324.8
Gross Unrealized Gains	6.3	15.2
Gross Unrealized Losses	4.3	0.3
Allowance for Credit Losses	0	0
Fair Value	418.7	339.7
Fixed maturities | Residential mortgage-backed securities
Schedule of Invested Assets [Line Items]
Amortized Cost	480.7	491.4
Gross Unrealized Gains	7.5	17.4
Gross Unrealized Losses	5.7	0.6
Allowance for Credit Losses	0	0
Fair Value	482.5	508.2
Fixed maturities | Asset backed securities
Schedule of Invested Assets [Line Items]
Amortized Cost	173	120.5
Gross Unrealized Gains	1.3	2.9
Gross Unrealized Losses	0.6	0.4
Allowance for Credit Losses	0.1	0.2
Fair Value	173.6	122.8
Fixed maturities | Collateralized loan obligations
Schedule of Invested Assets [Line Items]
Amortized Cost	336.4	285.9
Gross Unrealized Gains	1.3	4.9
Gross Unrealized Losses	1.6	1.2
Allowance for Credit Losses	0	0
Fair Value	$ 336.1	$ 289.6

Investments - Schedule of Amo_2

Investments - Schedule of Amortized Cost and Fair Values of Fixed Maturity Investments, by Contractual Maturity (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 281.7
Due after one year through five years	1,692
Due after five years through ten years	710
Thereafter	112.6
Structured securities	4,203.2
Amortized Cost	4,203.2	$ 3,981.1
Fair Value
Due in one year or less	284.6
Due after one year through five years	1,704.8
Due after five years through ten years	711.3
Thereafter	111.6
Structured securities		4,223.3
Fair Value	4,223.3	$ 4,107.1
Structured Securities
Amortized Cost
Structured securities	1,406.9
Fair Value
Structured securities	$ 1,411

Investments - Schedule of Carry

Investments - Schedule of Carrying Value and Unfunded Investment Commitments of Other Invested Assets Portfolio (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Carrying Value	$ 5,322.6	$ 5,255.8
Hedge funds
Schedule of Investments [Line Items]
Carrying Value	58.6	111.2
Unfunded Commitments	0	0
Private equity
Schedule of Investments [Line Items]
Carrying Value	248.9	211.4
Unfunded Commitments	64.2	80
Overseas deposits
Schedule of Investments [Line Items]
Carrying Value	74.9	102.1
Unfunded Commitments	0	0
Other
Schedule of Investments [Line Items]
Carrying Value	4.8	4.7
Unfunded Commitments	0	0
Total other investments
Schedule of Investments [Line Items]
Carrying Value	387.2	429.4
Unfunded Commitments	$ 64.2	$ 80

Investments - Schedule of Aging

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	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Fair value, less than one year	$ 1,967.8	$ 488.2
Unrealized losses, less than one year	36.9	9.8
Fair value, one year or greater	70	69.7
Unrealized losses, one year or greater	3.9	7.3
Fair Value	2,037.8	557.9
Unrealized Losses	40.8	17.1
U.S. Governments
Schedule of Investments [Line Items]
Fair value, less than one year	193.4	40.6
Unrealized losses, less than one year	2.6	0.3
Fair value, one year or greater	14.6	0
Unrealized losses, one year or greater	0.6	0
Fair Value	208	40.6
Unrealized Losses	3.2	0.3
Foreign Governments
Schedule of Investments [Line Items]
Fair value, less than one year	152.4	18
Unrealized losses, less than one year	3.3	0.5
Fair value, one year or greater	2.6	0.1
Unrealized losses, one year or greater	0.6	0.2
Fair Value	155	18.1
Unrealized Losses	3.9	0.7
Obligations of states and political subdivisions
Schedule of Investments [Line Items]
Fair value, less than one year	46	5.2
Unrealized losses, less than one year	0.8	0.3
Fair value, one year or greater	0.1	0
Unrealized losses, one year or greater	0.4	0
Fair Value	46.1	5.2
Unrealized Losses	1.2	0.3
Corporate bonds
Schedule of Investments [Line Items]
Fair value, less than one year	854.3	202.5
Unrealized losses, less than one year	18.3	6.7
Fair value, one year or greater	41.7	17.5
Unrealized losses, one year or greater	2	6.6
Fair Value	896	220
Unrealized Losses	20.3	13.3
Commercial mortgage-backed securities
Schedule of Investments [Line Items]
Fair value, less than one year	198.8	21.8
Unrealized losses, less than one year	4.1	0.3
Fair value, one year or greater	6.5	0
Unrealized losses, one year or greater	0.2	0
Fair Value	205.3	21.8
Unrealized Losses	4.3	0.3
Residential mortgage-backed securities
Schedule of Investments [Line Items]
Fair value, less than one year	284.2	74.4
Unrealized losses, less than one year	5.6	0.4
Fair value, one year or greater	4	3
Unrealized losses, one year or greater	0.1	0.2
Fair Value	288.2	77.4
Unrealized Losses	5.7	0.6
Asset backed securities
Schedule of Investments [Line Items]
Fair value, less than one year	62.6	4.6
Unrealized losses, less than one year	0.6	0.4
Fair value, one year or greater	0	0
Unrealized losses, one year or greater		0
Fair Value	62.6	4.6
Unrealized Losses	0.6	0.4
Collateralized loan obligations
Schedule of Investments [Line Items]
Fair value, less than one year	176.1	121.1
Unrealized losses, less than one year	1.6	0.9
Fair value, one year or greater	0.5	49.1
Unrealized losses, one year or greater		0.3
Fair Value	176.6	170.2
Unrealized Losses	$ 1.6	$ 1.2

Investments - Allowance for Cre

Investments - Allowance for Credit Losses (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 6.6	$ 0
Securities for which allowance was not previously recorded	2.9	15.9
Securities sold during the period	(3.5)	(39.3)
Additional net increases (decreases) in existing allowance	(3.5)	23.1
Ending balance	2.5	6.6
Cumulative Effect, Period of Adoption, Adjustment
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance		6.9
Foreign Governments
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance	0.2	0
Securities for which allowance was not previously recorded	0	0.3
Securities sold during the period	0	(0.2)
Additional net increases (decreases) in existing allowance	0	0.1
Ending balance	0.2	0.2
Foreign Governments | Cumulative Effect, Period of Adoption, Adjustment
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance		0
Obligations of states and political subdivisions
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance	0.1	0
Securities for which allowance was not previously recorded	0	0.3
Securities sold during the period	0	0
Additional net increases (decreases) in existing allowance	(0.1)	(0.2)
Ending balance	0	0.1
Obligations of states and political subdivisions | Cumulative Effect, Period of Adoption, Adjustment
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance		0
Corporate bonds
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance	6.1	0
Securities for which allowance was not previously recorded	2.7	15.3
Securities sold during the period	(3.5)	(39)
Additional net increases (decreases) in existing allowance	(3.1)	23
Ending balance	2.2	6.1
Corporate bonds | Cumulative Effect, Period of Adoption, Adjustment
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance		6.8
Asset backed securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance	0.2	0
Securities for which allowance was not previously recorded	0.2	0
Securities sold during the period	0	(0.1)
Additional net increases (decreases) in existing allowance	(0.3)	0.2
Ending balance	$ 0.1	0.2
Asset backed securities | Cumulative Effect, Period of Adoption, Adjustment
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning balance		$ 0.1

Investments - Schedule of Inves

Investments - Schedule of Investment Income and Expenses (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investment income:
Interest on fixed maturities	$ 98.9	$ 108.6	$ 129.5
Dividends on equity securities	3.1	2.8	11.1
Income on alternative investments	95.5	10.4	22.4
Income on short-term and other investments	3.3	3.9	8.9
Investment income	200.8	125.7	171.9
Investment expenses	(13.2)	(13)	(20.8)
Net investment income	$ 187.6	$ 112.7	$ 151.1

Investments - Schedule of Compa

Investments - Schedule of Company's Gross Realized Investment Gains (Losses) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Realized gains on fixed maturities and other	$ 43.7	$ 164.1	$ 55.3
Realized losses on fixed maturities and other	(42.8)	(121)	(43)
Credit losses on fixed maturities	0.6	(39.9)	0
Other	(6.3)	0	0
Net (losses) recognized on fixed maturities and other	(5.7)	(39.9)	(20.3)
Net realized gains (losses) on equity securities	71.5	(17.1)	128.9
Change in fair value recognized	(34.1)	10.3	(40.8)
Net realized gains (losses) on equity securities	37.4	(6.8)	88.1
Net realized investment (gains) losses	32.6	(3.6)	80.1
Income tax (benefit) provision	6.2	1.3	16.2
Net realized investment gains (losses), net of income taxes	26.4	(4.9)	63.9
Fixed maturities
Schedule of Investments [Line Items]
Realized gains on fixed maturities and other	30.6	37.1	22.2
Realized losses on fixed maturities and other	(11.8)	(35.2)	(11.7)
Other investments, including short-terms
Schedule of Investments [Line Items]
Realized gains on fixed maturities and other	9.8	93.8	0.1
Realized losses on fixed maturities and other	(18.5)	(78.6)	(31.3)
Other assets
Schedule of Investments [Line Items]
Realized gains on fixed maturities and other	3.3	33.2	33
Realized losses on fixed maturities and other	(12.5)	(7.2)	0
Other-than-temporary impairment losses
Schedule of Investments [Line Items]
Credit losses on fixed maturities	(0.6)	39.9	0
Other-than-temporary impairment losses	$ 0	$ 0	$ (20.3)

Investments - Schedule of Chang

Investments - Schedule of Changes in Unrealized Appreciation (Depreciation) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Net unrealized investment gains (losses) before income taxes	$ (106.9)	$ 82.4	$ 97.9
Income tax provision (benefit)	(21.5)	16.5	15.4
Net unrealized investment gains (losses), net of income taxes	(85.4)	65.9	82.5
Fixed maturities
Schedule of Investments [Line Items]
Net unrealized investment gains (losses) before income taxes	(105.9)	96	93.3
Other assets
Schedule of Investments [Line Items]
Net unrealized investment gains (losses) before income taxes	0	(14.3)	4.4
Other and short-term investments
Schedule of Investments [Line Items]
Net unrealized investment gains (losses) before income taxes	$ (1)	$ 0.7	$ 0.2

Investments - Schedule of Fair

Investments - Schedule of Fair Value of Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	$ (0.6)	$ 0.9
Operational currency exposure
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	(0.3)	0.4
Asset manager investment exposure
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	(0.3)	(0.2)
Total return strategy
Schedule of Investments [Line Items]
Derivative assets (liabilities), at fair value, net	$ 0	$ 0.7

Investments - Schedule of Reali

Investments - Schedule of Realized Gains and Losses of Investment on Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Gross realized investment gains	$ 33.2	$ 77	$ 30.9
Gross realized investment losses	(41.9)	(74.9)	(29)
Net realized investment gains (losses) on foreign    currency exchange forward contracts	(8.7)	2.1	1.9
Operational currency exposure
Schedule of Investments [Line Items]
Gross realized investment gains	16.5	13.2	5.7
Gross realized investment losses	(28.9)	(8.6)	(10.6)
Asset manager investment exposure
Schedule of Investments [Line Items]
Gross realized investment gains	3.7	2.2	2.7
Gross realized investment losses	(1)	(4)	(0.8)
Total return strategy
Schedule of Investments [Line Items]
Gross realized investment gains	13	61.6	22.5
Gross realized investment losses	$ (12)	$ (62.3)	$ (17.6)

Investments - Components of Res

Investments - Components of Restricted Assets (Detail) - USD ($) $ in Millions	Dec. 31, 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	$ 193.9	$ 189.4
Securities and cash on deposit supporting Lloyd’s business (1)	296.8	409.2
Total restricted investments	686.3	826.1
Securities And Letters Of Credit Pledged As Part Of Syndicate, Minimum Amount	296.8
Argo Re
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Securities and cash on deposit supporting Lloyd’s business (1)	140.3
Securities on deposit for regulatory and other purposes
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Securities on deposit for regulatory and other purposes	$ 195.6	$ 227.5

Investments - Financial Assets

Investments - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 5,322.6	$ 5,255.8
Other assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	387.2	429.4
Recurring fair value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	5,010.8	4,928.9
Recurring fair value | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,112.9	1,069.6
Recurring fair value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3,880.4	3,834.8
Recurring fair value | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	17.5	24.5
Recurring fair value | Fixed maturities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	4,223.3	4,107.1
Recurring fair value | Fixed maturities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	417.4	383.5
Recurring fair value | Fixed maturities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	3,803.1	3,716.6
Recurring fair value | Fixed maturities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2.8	7
Recurring fair value | Fixed maturities | Collateralized loan obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	336.1	289.6
Recurring fair value | Fixed maturities | Collateralized loan obligations | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Collateralized loan obligations | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	336.1	289.6
Recurring fair value | Fixed maturities | Collateralized loan obligations | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | U.S. Governments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	425	399.8
Recurring fair value | Fixed maturities | U.S. Governments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	417.4	383.5
Recurring fair value | Fixed maturities | U.S. Governments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	7.6	16.3
Recurring fair value | Fixed maturities | U.S. Governments | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Foreign Governments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	232.8	294.8
Recurring fair value | Fixed maturities | Foreign Governments | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Foreign Governments | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	232.8	294.8
Recurring fair value | Fixed maturities | Foreign Governments | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Obligations of states and political subdivisions
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	171.3	170.4
Recurring fair value | Fixed maturities | Obligations of states and political subdivisions | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Obligations of states and political subdivisions | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	171.3	170.4
Recurring fair value | Fixed maturities | Obligations of states and political subdivisions | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,983.3	1,981.8
Recurring fair value | Fixed maturities | Corporate bonds | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Corporate bonds | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1,980.5	1,974.8
Recurring fair value | Fixed maturities | Corporate bonds | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	2.8	7
Recurring fair value | Fixed maturities | Commercial mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	418.7	339.7
Recurring fair value | Fixed maturities | Commercial mortgage-backed securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Commercial mortgage-backed securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	418.7	339.7
Recurring fair value | Fixed maturities | Commercial mortgage-backed securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Residential mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	482.5	508.2
Recurring fair value | Fixed maturities | Residential mortgage-backed securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Residential mortgage-backed securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	482.5	508.2
Recurring fair value | Fixed maturities | Residential mortgage-backed securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Asset backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	173.6	122.8
Recurring fair value | Fixed maturities | Asset backed securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Fixed maturities | Asset backed securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	173.6	122.8
Recurring fair value | Fixed maturities | Asset backed securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	56.3	176.7
Recurring fair value | Equity securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	41.6	159.2
Recurring fair value | Equity securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Equity securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	14.7	17.5
Recurring fair value | Other assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	75.4	102.5
Recurring fair value | Other assets | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0.4
Recurring fair value | Other assets | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	75.4	102.1
Recurring fair value | Other assets | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Recurring fair value | Other investments, including short-terms
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	655.8	542.6
Recurring fair value | Other investments, including short-terms | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	653.9	526.5
Recurring fair value | Other investments, including short-terms | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	1.9	16.1
Recurring fair value | Other investments, including short-terms | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 0	$ 0

Investments - Schedule of Recon

Investments - Schedule of Reconciliation of Beginning and Ending Balances for Investments Categorized as Level 3 (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 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	1	0
Transfers out of Level 3	0	0
Total gains or losses (realized/unrealized):
Included in net income	4.2	(5.9)
Included in other comprehensive income	(0.8)	(0.5)
Purchases, issuances, sales, and settlements:
Purchases	1.3	5.3
Issuances	0	0
Sales	(14.1)	0
Settlements	0	0
Ending balance	16.1	24.5
Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at end of period	0	0
Credit Financial
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	7	7.4
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Total gains or losses (realized/unrealized):
Included in net income	0	0
Included in other comprehensive income	(0.8)	(0.5)
Purchases, issuances, sales, and settlements:
Purchases	0.1	0.1
Issuances	0	0
Sales	(3.5)	0
Settlements	0	0
Ending balance	2.8	7
Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at end of period	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	1	0
Transfers out of Level 3	0	0
Total gains or losses (realized/unrealized):
Included in net income	4.2	(5.9)
Included in other comprehensive income	0	0
Purchases, issuances, sales, and settlements:
Purchases	1.2	5.2
Issuances	0	0
Sales	(10.6)	0
Settlements	0	0
Ending balance	13.3	17.5
Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at end of period	$ 0	$ 0

Allowance for Credit Losses - P

Allowance for Credit Losses - Premium Receivables (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Premium Receivable, Allowance for Credit Loss [Roll Forward]
Premiums receivable	$ 648.6	$ 679.8
Balance, January 1, 2021	9.4
Current period change for estimated uncollectible premiums	(3.1)
Write-offs of uncollectible premiums receivable	(0.6)
Foreign exchange adjustments	0
Balance, December 31, 2021	$ 5.7

Allowance for Credit Losses - R

Allowance for Credit Losses - Reinsurance Recoverables (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Reinsurance recoverables, net	$ 2,966.4	$ 3,009
Balance, January 1, 2021	4.1
Current period change for estimated uncollectible reinsurance	(0.3)
Write-offs of uncollectible reinsurance recoverables	0
Balance, December 31, 2021	$ 3.8

Leases - Additional Information

Leases - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)property	Dec. 31, 2020USD ($)
Lessee, Lease, Description [Line Items]
Lease cost	$ 18.3	$ 20.3
Number of leased properties | property	1
Lease income	$ 1.4	$ 2.6
Minimum
Lessee, Lease, Description [Line Items]
Lease term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease term	13 years

Leases - Components of Leases (

Leases - Components of Leases (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating leases right-of-use assets	$ 81.4	$ 82
Operating lease liabilities	$ 97.7	$ 95.8
Operating lease weighted-average remaining lease term	9 years 6 months 3 days	10 years 6 months
Operating lease weighted-average discount rate	3.53%	3.77%

Leases - Lease Cost (Details)

Leases - Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease costs	$ 14.2	$ 15.3
Variable lease costs	6.2	5.4
Sublease income	(2.1)	(0.4)
Total lease costs	18.3	20.3
Operating cash flows from operating leases (fixed payments)	14.9	15.7
Operating cash flows from operating leases (liability reduction)	$ 12.8	$ 12.8

Leases - Lease Maturity (Detail

Leases - Lease Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2022	$ 13.8
2023	13.4
2024	11.8
2024	11.6
2026	11.2
Thereafter	54.4
Total future minimum lease payments	116.2
Future lease obligations
Less imputed interest	(18.5)
Total operating lease liability	$ 97.7	$ 95.8

Reinsurance - Additional Inform

Reinsurance - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Insurance [Abstract]
Reinsurance recoverables, allowance for doubtful accounts	$ 3.8	$ 4.1
Amount of collateral under reinsurance agreement	1,085.5	1,131.4
Paid loss recoverables in insurance recoverables	494.6	509.1
Losses and loss adjustment expenses	1,314.6	1,208.8	$ 1,220.7
Net of amounts ceded to reinsurers	$ 829.6	$ 941.3	$ 1,031.1

Reinsurance - Schedule of Reins

Reinsurance - Schedule of Reinsurance Premium (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Insurance [Abstract]
Direct written premiums	$ 2,990.6	$ 2,676.1	$ 2,510.4
Reinsurance ceded to other companies	(1,203.9)	(1,423.2)	(1,375.6)
Reinsurance assumed from other companies	190.6	557.2	619.8
Net written premiums	1,977.3	1,810.1	1,754.6
Direct earned premiums	2,917.7	2,660.6	2,412.4
Reinsurance ceded to other companies	(1,272.7)	(1,388.6)	(1,286.7)
Reinsurance assumed from other companies	265.1	508.5	604
Net earned premiums	$ 1,910.1	$ 1,780.5	$ 1,729.7
Percentage of reinsurance assumed to net earned premiums	13.90%	28.60%	34.90%

Reserves for Losses and Loss _3

Reserves for Losses and Loss Adjustment Expenses - Reserves for Losses and Loss Adjustment Expenses (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Net reserves beginning of the year	$ 2,906.1	$ 2,722.7	$ 2,562.9
Net AIL reserves acquired	0	27.9	0
Losses and LAE incurred during current calendar year, net of reinsurance:
Current accident year	1,176.3	1,201.1	1,082.6
Prior accident years	138.3	7.7	138.1
Losses and LAE incurred during calendar year, net of reinsurance	1,314.6	1,208.8	1,220.7
Losses and LAE payments made during current calendar year, net of reinsurance:
Current accident year	180.8	253.4	224.3
Prior accident years	688.4	866.4	806
Losses and LAE payments made during current calendar year, net of reinsurance:	869.2	1,119.8	1,030.3
Net reserve ceded - reinsurance to close transaction for years of account 2017 and prior	219.7	0	0
Change in participation interest	8.4	32.8	(14.4)
Foreign exchange adjustments	(17)	33.7	(16.2)
Net reserves - end of period	3,123.2	2,906.1	2,722.7
Reinsurance recoverables on unpaid losses and LAE, end of period	2,471.8	2,499.9	2,434.9
Reserves for losses and loss adjustment expenses	$ 5,595	$ 5,406	$ 5,157.6

Reserves for Losses and Loss _4

Reserves for Losses and Loss Adjustment Expenses - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)segment	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Loss adjustment expenses related to pandemic	$ 12.4
Number of reportable segments | segment	2
Claims remain outstanding period	10 years
Number of reporting segments | segment	2
Prior years	$ 138.3	$ 7.7	$ 138.1
U.S. Operations
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Prior years	120.9	2.4	15.7
U.S. Operations | Liability
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Prior years	112.1
U.S. Operations | Professional
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Prior years	33
International Operations
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Prior years	$ (26.9)	(6.2)	110.4
Run-off Lines
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Percentage of gross reserves for losses	5.00%
Prior years	$ 44.3	$ 11.5	$ 12

Reserves for Losses and Loss _5

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	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total (favorable) unfavorable prior-year development	$ 138.3	$ 7.7	$ 138.1
U.S. Operations
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total (favorable) unfavorable prior-year development	120.9	2.4	15.7
International Operations
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total (favorable) unfavorable prior-year development	(26.9)	(6.2)	110.4
Run-off Lines
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total (favorable) unfavorable prior-year development	$ 44.3	$ 11.5	$ 12

Reserves for Losses and Loss _6

Reserves for Losses and Loss Adjustment Expenses - Summary of Information about Incurred and Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance (Detail) $ in Millions	Dec. 31, 2021USD ($)claim	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)
Claims Development [Line Items]
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	$ 3,071.6
U.S. Operations | Liability
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	3,837.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	2,355.9
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	59.4
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	1,540.7
U.S. Operations | Liability | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	329.3	$ 328.2	$ 327.2	$ 328.9	$ 329.7	$ 335.9	$ 336.9	$ 339.3	$ 342.3	$ 329.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	315.7	313.2	305.3	295.4	285.3	263.2	226.6	169.8	103.8	37.3
IBNR & Expected Development on Reported Claims	$ 35.6
Cumulative number of reported claims | claim	27,587
U.S. Operations | Liability | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 357.3	344.8	343.1	346.6	351.5	360.4	361	355.8	344.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	325.4	318.2	306.9	289.3	266.5	228.8	174.3	109.7	36.5
IBNR & Expected Development on Reported Claims	$ 48.4
Cumulative number of reported claims | claim	27,258
U.S. Operations | Liability | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 341.3	327.4	321.9	323.9	326.3	330	337.1	328.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	291.4	283.2	266.3	240.6	206.9	154.6	91	32.4
IBNR & Expected Development on Reported Claims	$ 56.3
Cumulative number of reported claims | claim	23,473
U.S. Operations | Liability | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 347.9	335.4	328	328.7	330.3	343.8	339.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	289.3	263.9	236.4	195.6	140.2	86.9	33.7
IBNR & Expected Development on Reported Claims	$ 54.2
Cumulative number of reported claims | claim	21,729
U.S. Operations | Liability | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 379	355.3	353	342.4	350.5	342.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	293.8	255.6	217.1	144.1	84.5	28.5
IBNR & Expected Development on Reported Claims	$ 60.7
Cumulative number of reported claims | claim	18,693
U.S. Operations | Liability | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 431.7	397.7	384.3	373.7	374.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	295.2	238.5	158.8	83	27.8
IBNR & Expected Development on Reported Claims	$ 102.3
Cumulative number of reported claims | claim	20,868
U.S. Operations | Liability | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 420.4	414.5	430.4	426.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	245.5	175.8	98.9	34.3
IBNR & Expected Development on Reported Claims	$ 117
Cumulative number of reported claims | claim	23,150
U.S. Operations | Liability | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 427.1	423.7	421.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	186.1	113.6	32.4
IBNR & Expected Development on Reported Claims	$ 181.8
Cumulative number of reported claims | claim	22,270
U.S. Operations | Liability | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 386.7	404.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	85.9	25.6
IBNR & Expected Development on Reported Claims	$ 261.2
Cumulative number of reported claims | claim	17,001
U.S. Operations | Liability | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 416.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	27.6
IBNR & Expected Development on Reported Claims	$ 366.6
Cumulative number of reported claims | claim	11,344
U.S. Operations | Professional
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 777.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	380.9
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	14.4
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	411.3
U.S. Operations | Professional | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	24.3	24.4	24.7	24.9	24.5	24	25.8	28.6	28.3	27.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	24.3	24	24.2	23.5	22.6	21.4	19.9	16.9	8.6	2.3
IBNR & Expected Development on Reported Claims	$ 0.1
Cumulative number of reported claims | claim	642
U.S. Operations | Professional | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 18	18.1	18.3	19.5	19.8	19	21.1	21.5	20.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	17.9	17.9	17.9	17.5	17.6	14.2	10.9	6.3	1.9
IBNR & Expected Development on Reported Claims	$ 0.1
Cumulative number of reported claims | claim	625
U.S. Operations | Professional | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 34.4	35.1	35.4	36.2	33.7	26	22.4	22.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	33.6	33.3	32.3	25.5	24.1	15.1	5.4	2.3
IBNR & Expected Development on Reported Claims	$ 0.1
Cumulative number of reported claims | claim	1,044
U.S. Operations | Professional | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 38.3	37.9	37.1	34	33.2	29.5	29.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	31.7	31.3	26.2	20.8	15.6	8.3	1.8
IBNR & Expected Development on Reported Claims	$ 2.2
Cumulative number of reported claims | claim	1,831
U.S. Operations | Professional | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 43	35.5	42.9	45.1	44.8	44.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	34.4	30.8	28.9	24.6	11.9	2.4
IBNR & Expected Development on Reported Claims	$ (0.1)
Cumulative number of reported claims | claim	3,256
U.S. Operations | Professional | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 99.5	87.9	78.3	61.8	60.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	77.9	59.7	38	24.9	3.5
IBNR & Expected Development on Reported Claims	$ 4.2
Cumulative number of reported claims | claim	3,759
U.S. Operations | Professional | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 94.8	79.2	73.2	70.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	62.6	43.8	16.7	4.5
IBNR & Expected Development on Reported Claims	$ (0.5)
Cumulative number of reported claims | claim	4,303
U.S. Operations | Professional | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 105	96.8	94.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	50	32.9	4.9
IBNR & Expected Development on Reported Claims	$ 22.5
Cumulative number of reported claims | claim	5,091
U.S. Operations | Professional | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 142.6	152.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	36.4	13.3
IBNR & Expected Development on Reported Claims	$ 78.7
Cumulative number of reported claims | claim	5,389
U.S. Operations | Professional | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 177.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	12.1
IBNR & Expected Development on Reported Claims	$ 149.2
Cumulative number of reported claims | claim	5,208
U.S. Operations | Specialty
Claims Development [Line Items]
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	$ 36.5
U.S. Operations | Property
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	911
Cumulative Paid Losses & ALAE, Net of Reinsurance	841.9
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	(0.3)
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	68.8
U.S. Operations | Property | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	97.4	98.6	98.6	98.7	98.7	98.5	98.8	98.7	101.8	103.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	97.4	98.6	98.6	98.7	98.4	98.4	98.2	98	97.2	70.1
IBNR & Expected Development on Reported Claims	$ 6.3
Cumulative number of reported claims | claim	15,005
U.S. Operations | Property | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 77.2	78.2	78.4	78.2	77.8	78.2	78.7	79.9	74.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	77.2	78.2	78.1	75.9	77.1	77.4	75.5	73.2	52.5
IBNR & Expected Development on Reported Claims	$ 0.9
Cumulative number of reported claims | claim	10,717
U.S. Operations | Property | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 76	76.1	76.9	76.9	77.1	77	82.2	80.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	76	76.1	76.4	76.3	76.4	75.7	73.1	51.6
IBNR & Expected Development on Reported Claims	$ 0.5
Cumulative number of reported claims | claim	8,559
U.S. Operations | Property | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 69.2	69.2	69.1	68.9	69.9	73.4	74
Cumulative Paid Losses & ALAE, Net of Reinsurance	69	68.5	68.3	67.9	68.6	67.6	44.6
IBNR & Expected Development on Reported Claims	$ 0.8
Cumulative number of reported claims | claim	7,746
U.S. Operations | Property | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 56.5	56.6	56.6	57.1	57.6	59.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	56.3	56.4	56.1	55.8	55.2	39.4
IBNR & Expected Development on Reported Claims	$ 2
Cumulative number of reported claims | claim	7,999
U.S. Operations | Property | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 94.5	94.9	86.9	79.6	75.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	88.4	100.8	113.9	95.3	54.4
IBNR & Expected Development on Reported Claims	$ 0
Cumulative number of reported claims | claim	10,388
U.S. Operations | Property | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 96.9	95.1	93.1	89.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	98.8	107	126.7	61.3
IBNR & Expected Development on Reported Claims	$ (12.9)
Cumulative number of reported claims | claim	11,145
U.S. Operations | Property | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 98.4	88.8	91.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	90.9	82.4	55.8
IBNR & Expected Development on Reported Claims	$ 2.1
Cumulative number of reported claims | claim	11,724
U.S. Operations | Property | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 133.2	129.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	116.6	75.9
IBNR & Expected Development on Reported Claims	$ (9.3)
Cumulative number of reported claims | claim	11,504
U.S. Operations | Property | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 111.7
Cumulative Paid Losses & ALAE, Net of Reinsurance	71.3
IBNR & Expected Development on Reported Claims	$ (0.6)
Cumulative number of reported claims | claim	9,265
U.S. Operations | Specialty Admitted | Specialty
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 59.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	24
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	0.6
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	36.5
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	3.3	3.3	3.6	3.5	3.9	4	4.3	4.9	6.7	7.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	3.4	3.4	3.4	3.3	3.4	3.3	3.3	3.3	3.3	3.6
IBNR & Expected Development on Reported Claims	$ 0
Cumulative number of reported claims | claim	121
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 0.9	0.9	0.9	0.9	1.7	2.5	4.6	8.6	10
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.4
IBNR & Expected Development on Reported Claims	$ 0.1
Cumulative number of reported claims | claim	47
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 4.1	4.6	4.6	4.8	6	8.9	13.1	13.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	4.1	4	4.1	4.1	4	4	3.3	1.1
IBNR & Expected Development on Reported Claims	$ 0
Cumulative number of reported claims | claim	45
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 0.3	0.5	1.2	5.5	9.5	14.3	14.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.3	0.3	0.3	0.3	0.2	0.1	0.2
IBNR & Expected Development on Reported Claims	$ 0
Cumulative number of reported claims | claim	24
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 3.3	4.7	6.2	11.2	15	15
Cumulative Paid Losses & ALAE, Net of Reinsurance	2.8	2.2	2.2	2.2	1.6	1.3
IBNR & Expected Development on Reported Claims	$ 0.9
Cumulative number of reported claims | claim	56
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 0.7	0.9	7.6	16.2	16.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.2	0.1	0	0.1	0.3
IBNR & Expected Development on Reported Claims	$ 1
Cumulative number of reported claims | claim	106
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 3.5	3.3	17.4	20.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	1.2	1.7	0.7	0
IBNR & Expected Development on Reported Claims	$ 2.6
Cumulative number of reported claims | claim	142
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 5.6	8.5	22.7
Cumulative Paid Losses & ALAE, Net of Reinsurance	3.2	0.7	0.7
IBNR & Expected Development on Reported Claims	$ 0.6
Cumulative number of reported claims | claim	233
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 10.3	25.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	7.6	0.3
IBNR & Expected Development on Reported Claims	$ 2.3
Cumulative number of reported claims | claim	409
U.S. Operations | Specialty Admitted | Specialty | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 27.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.3
IBNR & Expected Development on Reported Claims	$ 26.5
Cumulative number of reported claims | claim	427
International Operations | Argo Insurance Bermuda- Liability | Liability
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 172.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	88.8
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	0
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	84
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0.6	0.6	0.6	0	1.7	4.4	5.6	7.4	7.4	7.4
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	$ 0.5
Cumulative number of reported claims | claim	1,392
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 6	5.3	5.3	2.2	4.9	8.5	8.5	8.5	8.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	2.4	2.4	2.3	2.3	2.3	0	0	0	0
IBNR & Expected Development on Reported Claims	$ 0.7
Cumulative number of reported claims | claim	1,200
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 1.6	2.3	2.3	1.5	6.2	9.8	9.8	9.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	1.4	1.4	1.2	1.2	0.1	0.1	0	0
IBNR & Expected Development on Reported Claims	$ (0.4)
Cumulative number of reported claims | claim	1,350
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 51.3	45.1	45.4	35.4	24.8	14.3	11.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	38.9	34.8	26.6	20.3	16.1	0	0
IBNR & Expected Development on Reported Claims	$ 0
Cumulative number of reported claims | claim	1,613
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 0.8	6.1	6.6	14	14	13.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.2	0.1	0.1	0	0	0
IBNR & Expected Development on Reported Claims	$ 0.5
Cumulative number of reported claims | claim	1,943
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 37.3	30.3	26.9	17.3	17.1
Cumulative Paid Losses & ALAE, Net of Reinsurance	19.7	18	3.4	3.3	0
IBNR & Expected Development on Reported Claims	$ 10.4
Cumulative number of reported claims | claim	2,129
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 24.2	26.6	32.1	8.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	18.5	18.3	13.8	0
IBNR & Expected Development on Reported Claims	$ 5.2
Cumulative number of reported claims | claim	1,110
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 13.8	13.6	13.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.7	0.1	0
IBNR & Expected Development on Reported Claims	$ 12.7
Cumulative number of reported claims | claim	1,168
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 24.9	23.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	7	0.8
IBNR & Expected Development on Reported Claims	$ 16.6
Cumulative number of reported claims | claim	1,267
International Operations | Argo Insurance Bermuda- Liability | Liability | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 12.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	0
IBNR & Expected Development on Reported Claims	$ 12.3
Cumulative number of reported claims | claim	1,053
International Operations | Syndicate 1200 | Liability
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	$ 65.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	13
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	3.7
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	56.2
International Operations | Syndicate 1200 | Liability | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Liability | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Liability | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Liability | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Liability | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Liability | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Liability | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	19.9	19.5	19.6	17.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	6.1	5.9	2.5	0.6
IBNR & Expected Development on Reported Claims	5
International Operations | Syndicate 1200 | Liability | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	15.2	15.7	14.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	5.2	4.6	1.4
IBNR & Expected Development on Reported Claims	5.3
International Operations | Syndicate 1200 | Liability | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	14.6	15.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	1.5	1.1
IBNR & Expected Development on Reported Claims	8
International Operations | Syndicate 1200 | Liability | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	15.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.2
IBNR & Expected Development on Reported Claims	12.7
International Operations | Syndicate 1200 | Professional
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	85.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	17.5
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	10.5
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	78.6
International Operations | Syndicate 1200 | Professional | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Professional | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Professional | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Professional | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Professional | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Professional | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Professional | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	15.5	15.3	14.4	13.7
Cumulative Paid Losses & ALAE, Net of Reinsurance	4.6	4.5	1.8	0.1
IBNR & Expected Development on Reported Claims	4.6
International Operations | Syndicate 1200 | Professional | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	20.2	20.9	19.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	9.1	8.7	2.7
IBNR & Expected Development on Reported Claims	7.1
International Operations | Syndicate 1200 | Professional | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	25	25
Cumulative Paid Losses & ALAE, Net of Reinsurance	3.1	2.2
IBNR & Expected Development on Reported Claims	12
International Operations | Syndicate 1200 | Professional | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	24.9
Cumulative Paid Losses & ALAE, Net of Reinsurance	0.7
IBNR & Expected Development on Reported Claims	20
International Operations | Syndicate 1200 | Specialty
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	314.3
Cumulative Paid Losses & ALAE, Net of Reinsurance	143.9
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	0
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	170.4
International Operations | Syndicate 1200 | Specialty | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Specialty | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Specialty | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Specialty | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Specialty | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Specialty | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Specialty | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	53	55	53.8	43.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	25.5	32.7	23.8	3
IBNR & Expected Development on Reported Claims	2.2
International Operations | Syndicate 1200 | Specialty | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	80.5	84	66.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	65.8	65.8	31.3
IBNR & Expected Development on Reported Claims	5.1
International Operations | Syndicate 1200 | Specialty | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	108.2	109.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	42.9	27.7
IBNR & Expected Development on Reported Claims	19.8
International Operations | Syndicate 1200 | Specialty | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	72.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	9.7
IBNR & Expected Development on Reported Claims	37.8
International Operations | Syndicate 1200 | Property
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	234.6
Cumulative Paid Losses & ALAE, Net of Reinsurance	95.5
Outstanding liabilities for unpaid losses and ALAE prior to 2012, net of reinsurance	0
Total outstanding liabilities for unpaid losses and ALAE, net of reinsurance	139.1
International Operations | Syndicate 1200 | Property | Accident Year 2012
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0	$ 0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Property | Accident Year 2013
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0	$ 0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Property | Accident Year 2014
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0	$ 0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Property | Accident Year 2015
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0	$ 0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Property | Accident Year 2016
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	0	$ 0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Property | Accident Year 2017
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	0	0	0	0	0
Cumulative Paid Losses & ALAE, Net of Reinsurance	0	0	0	0	$ 0
IBNR & Expected Development on Reported Claims	0
International Operations | Syndicate 1200 | Property | Accident Year 2018
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	22.1	21.7	21.8	19.7
Cumulative Paid Losses & ALAE, Net of Reinsurance	14.8	14.4	6.1	$ 1.5
IBNR & Expected Development on Reported Claims	0.2
International Operations | Syndicate 1200 | Property | Accident Year 2019
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	38.7	40.1	37.2
Cumulative Paid Losses & ALAE, Net of Reinsurance	36	31.9	$ 9.5
IBNR & Expected Development on Reported Claims	1.2
International Operations | Syndicate 1200 | Property | Accident Year 2020
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	60.3	62.8
Cumulative Paid Losses & ALAE, Net of Reinsurance	29.1	$ 20
IBNR & Expected Development on Reported Claims	6
International Operations | Syndicate 1200 | Property | Accident Year 2021
Claims Development [Line Items]
Incurred Losses & ALAE, Net of Reinsurance	113.5
Cumulative Paid Losses & ALAE, Net of Reinsurance	15.6
IBNR & Expected Development on Reported Claims	$ 68.1

Reserves for Losses and Loss _7

Reserves for Losses and Loss Adjustment Expenses - Summary of Reconciliation of Net Incurred and Paid Development to Liability for Unpaid Losses and LAE in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	$ 3,071.6
Total reinsurance recoverables on unpaid losses and LAE	2,471.8
Unallocated loss adjustment expenses	70.4
Unamortized reserve discount	(18.8)	$ (17.8)	$ (17.9)
Reserves for losses and loss adjustment expenses	5,595	5,406	5,157.6
U.S. Operations | Liability
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	1,540.7
Total reinsurance recoverables on unpaid losses and LAE	825.4
U.S. Operations | Professional
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	411.3
Total reinsurance recoverables on unpaid losses and LAE	251.3
U.S. Operations | Property
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	68.8
Total reinsurance recoverables on unpaid losses and LAE	206.9
U.S. Operations | Specialty
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	36.5
Total reinsurance recoverables on unpaid losses and LAE	11.4
International Operations | Argo Insurance Bermuda- Liability | Liability
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	84
Total reinsurance recoverables on unpaid losses and LAE	207.6
International Operations | Syndicate 1200 | Liability
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	56.2
Total reinsurance recoverables on unpaid losses and LAE	30.8
International Operations | Syndicate 1200 | Professional
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	78.6
Total reinsurance recoverables on unpaid losses and LAE	74.6
International Operations | Syndicate 1200 | Property
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	139.1
Total reinsurance recoverables on unpaid losses and LAE	102.6
International Operations | Syndicate 1200 | Specialty
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	170.4
Total reinsurance recoverables on unpaid losses and LAE	103.3
Run-off Lines
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	183.4
Total reinsurance recoverables on unpaid losses and LAE	82.5
Unamortized reserve discount	(4.7)	$ (4.9)	$ (4.9)
Other Lines
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Total liabilities for unpaid losses and ALAE, net of reinsurance	302.6
Total reinsurance recoverables on unpaid losses and LAE	$ 575.4

Reserves for Losses and Loss _8

Reserves for Losses and Loss Adjustment Expenses - Schedule of Supplementary Unaudited Information About Annual Percentage Payout of Incurred Losses and ALAE, Net of Reinsurance (Detail)	Dec. 31, 2021
U.S. Operations | Liability
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	8.90%
Year 2	17.60%
Year 3	18.20%
Year 4	18.30%
Year 5	11.50%
Year 6	8.30%
Year 7	5.20%
Year 8	3.60%
Year 9	2.40%
Year 10	1.70%
Remainder	4.30%
U.S. Operations | Professional
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	6.10%
Year 2	19.10%
Year 3	22.00%
Year 4	18.60%
Year 5	12.50%
Year 6	8.90%
Year 7	5.50%
Year 8	3.20%
Year 9	1.80%
Year 10	1.00%
Remainder	1.20%
U.S. Operations | Property
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	58.40%
Year 2	32.50%
Year 3	5.70%
Year 4	2.30%
Year 5	0.70%
Year 6	0.20%
Year 7	0.10%
Year 8	0.00%
Year 9	0.00%
Year 10	0.00%
Remainder	0.00%
U.S. Operations | Specialty
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	52.70%
Year 2	22.80%
Year 3	19.20%
Year 4	3.40%
Year 5	1.20%
Year 6	0.40%
Year 7	0.10%
Year 8	0.10%
Year 9	0.00%
Year 10	0.00%
Remainder	0.00%
International Operations | Argo Insurance Bermuda- Liability | Liability
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	0.60%
Year 2	14.20%
Year 3	12.70%
Year 4	13.20%
Year 5	12.20%
Year 6	10.50%
Year 7	8.60%
Year 8	6.80%
Year 9	5.30%
Year 10	4.00%
Remainder	11.90%
International Operations | Syndicate 1200 | Liability
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	6.30%
Year 2	11.50%
Year 3	13.40%
Year 4	15.00%
Year 5	16.00%
Year 6	11.70%
Year 7	6.90%
Year 8	5.20%
Year 9	3.70%
Year 10	2.70%
Remainder	7.60%
International Operations | Syndicate 1200 | Professional
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	7.30%
Year 2	12.50%
Year 3	18.50%
Year 4	17.60%
Year 5	12.40%
Year 6	8.70%
Year 7	5.90%
Year 8	4.50%
Year 9	3.20%
Year 10	2.30%
Remainder	7.10%
International Operations | Syndicate 1200 | Property
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	33.80%
Year 2	39.20%
Year 3	14.30%
Year 4	8.40%
Year 5	2.70%
Year 6	0.80%
Year 7	0.40%
Year 8	0.20%
Year 9	0.10%
Year 10	0.00%
Remainder	0.10%
International Operations | Syndicate 1200 | Specialty
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	32.00%
Year 2	36.40%
Year 3	16.70%
Year 4	9.20%
Year 5	3.00%
Year 6	1.50%
Year 7	0.60%
Year 8	0.30%
Year 9	0.10%
Year 10	0.00%
Remainder	0.00%

Reserves for Losses and Loss _9

Reserves for Losses and Loss Adjustment Expenses - Schedule of Information About Discounted Liabilities For Unpaid Losses and LAE (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Carrying Amount of Reserves for Losses & LAE	$ 277.4	$ 278.8	$ 302
Aggregate Amount of Discount	18.8	17.8	17.9
Interest Accretion	1.1	1.9	1.5
U.S. Operations | Specialty Admitted | Liability
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Carrying Amount of Reserves for Losses & LAE	163.1	150.4	153.1
Aggregate Amount of Discount	14.1	12.9	13
Interest Accretion	$ 0.9	$ 1.9	$ 1.3
Discount Rate	2.25%	2.25%	2.25%
Run-off Lines
Short-duration Insurance Contracts, Discounted Liabilities [Line Items]
Carrying Amount of Reserves for Losses & LAE	$ 114.3	$ 128.4	$ 148.9
Aggregate Amount of Discount	4.7	4.9	4.9
Interest Accretion	$ 0.2	$ 0	$ 0.2
Discount Rate	3.50%	3.50%	3.50%

Run-off Lines - Gross Reserves

Run-off Lines - Gross Reserves for Run-Off Lines (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Asbestos and Environmental	$ 63.8	$ 59.3
Gross reserves - Run-off Lines	261.2	236.5
Reinsurance assumed
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Asbestos and Environmental	29.6	29.4
Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Asbestos and Environmental	34.2	29.9
Risk-management
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gross reserves - Run-off Lines	162.6	162.4
Run-off reinsurance lines
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gross reserves - Run-off Lines	0.5	0.5
Other run-off lines
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gross reserves - Run-off Lines	$ 34.3	$ 14.3

Run-off Lines - Total Gross Res

Run-off Lines - Total Gross Reserves for Asbestos Exposure (Detail) - Asbestos and Environmental Claims - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total direct written reserves	$ 23.4	$ 23.8	$ 19.3
Total asbestos reserves	47.9	48.8	42.8
Case reserves
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total direct written reserves	3	3.1	2.7
Unallocated loss adjustment expense ("ULAE")
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total direct written reserves	0.5	0.5	0.5
Incurred but not reported ("IBNR")
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total direct written reserves	19.9	20.2	16.1
Assumed domestic
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total assumed reserves	20.1	22	21.1
Assumed domestic | Case reserves
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total assumed reserves	7.4	8.4	9.1
Assumed domestic | Unallocated loss adjustment expense ("ULAE")
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total assumed reserves	0.8	0.8	0.8
Assumed domestic | Incurred but not reported ("IBNR")
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total assumed reserves	11.9	12.8	11.2
Assumed London
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total assumed reserves	4.4	3	2.4
Assumed London | Case reserves
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total assumed reserves	2.1	1.4	1.3
Assumed London | Incurred but not reported ("IBNR")
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total assumed reserves	$ 2.3	$ 1.6	$ 1.1

Run-off Lines - Underwriting Lo

Run-off Lines - Underwriting Losses for Run-Off Lines (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Asbestos and Environmental	$ (14.7)	$ (17.4)	$ (8.3)
Total underwriting loss - Run-off Lines	(44.7)	(12.8)	(14.2)
Reinsurance assumed
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Asbestos and Environmental	(4.7)	(5.7)	(4.4)
Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Asbestos and Environmental	(10)	(11.7)	(3.9)
Risk-management
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total underwriting loss - Run-off Lines	(9.9)	7.6	(4.9)
Run-off reinsurance lines
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total underwriting loss - Run-off Lines	0	0.4	0.7
Other run-off lines
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total underwriting loss - Run-off Lines	$ (20.1)	$ (3.4)	$ (1.7)

Long-term Debt - Additional Inf

Long-term Debt - Additional Information (Detail) £ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2012USD ($)	Dec. 31, 2021USD ($)debtInstrument	Dec. 31, 2020USD ($)	Dec. 31, 2021GBP (£)debtInstrument	Nov. 02, 2018USD ($)
Debt Instrument [Line Items]
Principal		$ 143,800,000	$ 143,800,000
Redemption price, percentage		100.00%
Junior subordinated debentures		$ 258,200,000	257,800,000
Floating rate loan stock denominated in Euros		40,500,000	44,200,000
Amount of collateral under reinsurance agreement		1,085,500,000	1,131,400,000
Letter of Credit
Debt Instrument [Line Items]
Letter of credit facility amount outstanding		167,400,000
Amount of collateral under reinsurance agreement		193,900,000
New Credit Agreement
Debt Instrument [Line Items]
Line of credit, maximum borrowing amount					$ 325,000,000
New Credit Agreement | Term Loan
Debt Instrument [Line Items]
Principal					125,000,000
New Credit Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Principal					200,000,000
Line of credit, maximum borrowing amount					$ 200,000,000
Letter of credit facility amount outstanding		40,300,000
New Credit Agreement | Letter of Credit
Debt Instrument [Line Items]
Letter of credit facility amount outstanding			70,500,000
Reinsurance Credit Facilities, Secured Bilateral Line of Credit Facilities | Letter of Credit
Debt Instrument [Line Items]
Letter of credit facility amount outstanding		205,000,000
Committed Secured Bilateral Facility | Letter of Credit
Debt Instrument [Line Items]
Letter of credit facility amount outstanding		$ 59,200,000
Number of letters of credit | debtInstrument		1		1
Debt instrument, term		1 year
Uncommitted Secured Bilateral Facility | Letter of Credit
Debt Instrument [Line Items]
Letter of credit facility amount outstanding		$ 108,200,000
Number of letters of credit | debtInstrument		2		2
Uncommitted Secured Bilateral LOC facility | Letter of Credit
Debt Instrument [Line Items]
Letter of credit facility amount outstanding		$ 260,000
Funds at Lloyd's Instrument | Letter of Credit
Debt Instrument [Line Items]
Letter of credit facility amount outstanding		$ 35,100,000		£ 26
Debt instrument, term		1 year
Unsecured Line of Credit Facility | Letter of Credit
Debt Instrument [Line Items]
Amount of collateral under reinsurance agreement		$ 5,000,000	$ 3,900,000
Junior subordinated debentures
Debt Instrument [Line Items]
Redemption price, percentage		100.00%	100.00%
Subordinated debentures
Debt Instrument [Line Items]
Principal		$ 91,800,000	$ 91,800,000
Debt instrument interest rate stated percentage		3.35%	3.37%	3.35%
Junior subordinated debentures		$ 91,800,000
Unsecured debentures		$ 85,500,000	$ 85,100,000
Subordinated debentures | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate basis spread		3.15%	3.15%
Unsecured debt
Debt Instrument [Line Items]
Redemption price, percentage			100.00%
Senior unsecured fixed rate notes
Debt Instrument [Line Items]
Principal	$ 143,750,000
Debt instrument interest rate stated percentage	6.50%
Redemption price, percentage	100.00%

Long-term Debt - Schedule of Un

Long-term Debt - Schedule of Unamortized Debt Issuance Costs Deducted from Carrying Value of Debt Liability (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Senior unsecured fixed rate notes	$ 143.8	$ 143.8
Less: unamortized debt issuance costs	(3.5)	(3.6)
Senior unsecured fixed rate notes, less unamortized debt issuance costs	$ 140.3	$ 140.2

Long-term Debt - Schedule of Ju

Long-term Debt - Schedule of Junior Subordinated Debentures (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Junior subordinated debentures, Amount	$ 258.2	$ 257.8
Argo Group
Debt Instrument [Line Items]
Junior subordinated debentures, Amount	$ 28.4	$ 28.4
Trust preferred debentures | Argo Group | PXRE Capital Statutory Trust II
Debt Instrument [Line Items]
Interest rate	4.26%	4.32%
Junior subordinated debentures, Amount	$ 18	$ 18
Trust preferred debentures | Argo Group | PXRE Capital Trust VI
Debt Instrument [Line Items]
Interest rate	4.12%	4.15%
Junior subordinated debentures, Amount	$ 10.3	$ 10.3
Trust preferred debentures | Argo Group US
Debt Instrument [Line Items]
Junior subordinated debentures, Amount	$ 172.7	$ 172.7
Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust I
Debt Instrument [Line Items]
Interest rate	4.26%	4.32%
Junior subordinated debentures, Amount	$ 15.5	$ 15.5
Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust III
Debt Instrument [Line Items]
Interest rate	4.22%	4.34%
Junior subordinated debentures, Amount	$ 12.3	$ 12.3
Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust IV
Debt Instrument [Line Items]
Interest rate	4.00%	4.07%
Junior subordinated debentures, Amount	$ 13.4	$ 13.4
Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust V
Debt Instrument [Line Items]
Interest rate	4.02%	4.05%
Junior subordinated debentures, Amount	$ 12.4	$ 12.4
Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust VI
Debt Instrument [Line Items]
Interest rate	4.02%	4.03%
Junior subordinated debentures, Amount	$ 13.4	$ 13.4
Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust VII
Debt Instrument [Line Items]
Interest rate	3.80%	3.82%
Junior subordinated debentures, Amount	$ 15.5	$ 15.5
Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust VIII
Debt Instrument [Line Items]
Interest rate	3.76%	3.79%
Junior subordinated debentures, Amount	$ 15.5	$ 15.5
Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust IX
Debt Instrument [Line Items]
Interest rate	3.80%	3.82%
Junior subordinated debentures, Amount	$ 15.5	$ 15.5
Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust X
Debt Instrument [Line Items]
Interest rate	3.60%	3.62%
Junior subordinated debentures, Amount	$ 30.9	$ 30.9
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group | PXRE Capital Statutory Trust II
Debt Instrument [Line Items]
Interest rate basis spread	4.10%	4.10%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group | PXRE Capital Trust VI
Debt Instrument [Line Items]
Interest rate basis spread	3.90%	3.90%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust I
Debt Instrument [Line Items]
Interest rate basis spread	4.10%	4.10%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust III
Debt Instrument [Line Items]
Interest rate basis spread	4.10%	4.10%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust IV
Debt Instrument [Line Items]
Interest rate basis spread	3.85%	3.85%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust V
Debt Instrument [Line Items]
Interest rate basis spread	3.85%	3.85%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust VI
Debt Instrument [Line Items]
Interest rate basis spread	3.80%	3.80%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust VII
Debt Instrument [Line Items]
Interest rate basis spread	3.60%	3.60%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust VIII
Debt Instrument [Line Items]
Interest rate basis spread	3.55%	3.55%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust IX
Debt Instrument [Line Items]
Interest rate basis spread	3.60%	3.60%
London Interbank Offered Rate (LIBOR) | Trust preferred debentures | Argo Group US | Argonaut Group Statutory Trust X
Debt Instrument [Line Items]
Interest rate basis spread	3.40%	3.40%

Long-term Debt - Schedule of Ma

Long-term Debt - Schedule of Maybrooke Junior Subordinated Debentures (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Principal	$ 143.8	$ 143.8
Subordinated debentures
Debt Instrument [Line Items]
Interest rate	3.35%	3.37%
Principal	$ 91.8	$ 91.8
Carrying Value	$ 85.5	$ 85.1
London Interbank Offered Rate (LIBOR) | Subordinated debentures
Debt Instrument [Line Items]
Interest rate basis spread	3.15%	3.15%

Long-term Debt- Schedule of Ter

Long-term Debt- Schedule of Terms and Principal Amounts of Other Indebtedness (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Other indebtedness	$ 57	$ 60.7
Floating rate loan stock
Debt Instrument [Line Items]
Other indebtedness	$ 57	$ 60.7

Long-term Debt - Schedule of Fl

Long-term Debt - Schedule of Floating Rate Loan Stock, Notes Outstanding (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Amount	$ 57	$ 60.7
Floating Rate Loan Stock, U.S. Dollar, Start Year 2004
Debt Instrument [Line Items]
Interest rate	4.35%	4.54%
Amount	$ 6.5	$ 6.5
Floating Rate Loan Stock, U.S. Dollar, Start Year 2006
Debt Instrument [Line Items]
Interest rate	4.15%	4.34%
Amount	$ 10	$ 10
Floating Rate Loan Stock, U.S. Dollar
Debt Instrument [Line Items]
Amount	$ 16.5	$ 16.5
Floating Rate Loan Stock, Euro, Start Year 2005
Debt Instrument [Line Items]
Interest rate	3.44%	3.47%
Amount	$ 13.5	$ 14.7
Floating Rate Loan Stock, Euro, Start Year 2006
Debt Instrument [Line Items]
Interest rate	3.44%	3.47%
Amount	$ 11.8	$ 12.9
Floating Rate Loan Stock, Euro, Start Year 2007
Debt Instrument [Line Items]
Interest rate	3.30%	3.36%
Amount	$ 15.2	$ 16.6
Floating Rate Loan Stock, Euro
Debt Instrument [Line Items]
Amount	$ 40.5	$ 44.2
London Interbank Offered Rate (LIBOR) | Floating Rate Loan Stock, U.S. Dollar, Start Year 2004
Debt Instrument [Line Items]
Interest rate basis spread	4.20%	4.20%
London Interbank Offered Rate (LIBOR) | Floating Rate Loan Stock, U.S. Dollar, Start Year 2006
Debt Instrument [Line Items]
Interest rate basis spread	4.00%	4.00%
Euribor | Floating Rate Loan Stock, Euro, Start Year 2005
Debt Instrument [Line Items]
Interest rate basis spread	4.00%	4.00%
Euribor | Floating Rate Loan Stock, Euro, Start Year 2006
Debt Instrument [Line Items]
Interest rate basis spread	4.00%	4.00%
Euribor | Floating Rate Loan Stock, Euro, Start Year 2007
Debt Instrument [Line Items]
Interest rate basis spread	3.90%	3.90%

Long-term Debt - Schedule of Lo

Long-term Debt - Schedule of Long-term Debt Maturity (Details) $ in Millions	Dec. 31, 2021USD ($)
Junior subordinated debentures
Debt Instrument [Line Items]
Total	$ 421.4
2022	10.4
2023	11.3
2024	11.8
2025	11.8
2026	11.8
Thereafter	364.3
Senior unsecured fixed rate notes
Debt Instrument [Line Items]
Total	335.4
2022	9.3
2023	9.4
2024	9.3
2025	9.4
2026	9.3
Thereafter	288.7
Floating rate loan stock
Debt Instrument [Line Items]
Total	88.6
2022	2.1
2023	2.2
2024	2.2
2025	2.2
2026	2.2
Thereafter	$ 77.7

Disclosures about Fair Value _3

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	Dec. 31, 2021	Dec. 31, 2020
Junior subordinated debentures | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial instruments	$ 258.2	$ 257.8
Junior subordinated debentures | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial instruments	264.8	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	172.9	173.6
Junior subordinated debentures | Subordinated debentures | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial instruments	85.5	85.1
Junior subordinated debentures | Subordinated debentures | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial instruments	91.9	92.3
Senior unsecured fixed rate notes | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial instruments	140.3	140.2
Senior unsecured fixed rate notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial instruments	148.4	146.7
Floating rate loan stock | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial instruments	57	60.7
Floating rate loan stock | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial instruments	$ 57.1	$ 61

Disclosures about Fair Value _4

Disclosures about Fair Value of Financial Instruments - Schedule of Financial Instruments Measured at Fair Value (Details) - Recurring fair value - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	$ 470.3	$ 473.6
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	148.4	146.7
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	321.9	326.9
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	0	0
Junior subordinated debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	264.8	265.9
Junior subordinated debentures | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	0	0
Junior subordinated debentures | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	264.8	265.9
Junior subordinated debentures | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	0	0
Senior unsecured fixed rate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	148.4	146.7
Senior unsecured fixed rate notes | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	148.4	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
Senior unsecured fixed rate notes | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	0	0
Floating rate loan stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	57.1	61
Floating rate loan stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	0	0
Floating rate loan stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	57.1	61
Floating rate loan stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	0	0
Trust preferred debentures | Junior subordinated debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	172.9	173.6
Trust preferred debentures | Junior subordinated debentures | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	0	0
Trust preferred debentures | Junior subordinated debentures | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	172.9	173.6
Trust preferred debentures | Junior subordinated debentures | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	0	0
Subordinated debentures | Junior subordinated debentures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	91.9	92.3
Subordinated debentures | Junior subordinated debentures | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	0	0
Subordinated debentures | Junior subordinated debentures | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	91.9	92.3
Subordinated debentures | Junior subordinated debentures | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments	$ 0	$ 0

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / shares	Jul. 09, 2020$ / shares	May 03, 2016USD ($)
Class of Stock [Line Items]
Preferred shares, issued (in shares) | shares	6,000	6,000
Depositary shares issued (in shares) | shares	6,000,000
Preferred stock, liquidation preference (in dollars per share)	$ 25,000	$ 25,000
Depositary share, liquidation preference (in dollars per share)	25			$ 25
Preferred stock, per depositary share amounts of preferred dividends (in dollars per share)	$ 1.75
Preferred shares, authorized (in shares) | shares	30,000,000	30,000,000
Preferred shares, par value (in dollars per share)	$ 1	$ 1
Preferred shares, outstanding (in shares) | shares	6,000	6,000
Dividend declared per common share (in dollars per share)	$ 1.24	$ 1.24	$ 1.24
Cash dividends paid to common stockholders | $	$ 43.9	$ 43	$ 43.1
Common shares repurchased on open market (in shares) | shares	0	0
Fractional interest per preference share	0.001
Series A Preferred Stock
Class of Stock [Line Items]
Preferred shares, issued (in shares) | shares	6,000
Preferred stock, liquidation preference (in dollars per share)	$ 25,000			$ 25,000
Dividends declared per preferred share (in dollars per share)	0.0700
Preferred stock dividends (in dollars per share)	$ 1,750
Payments of dividends | $	$ 10.5
Preferred shares, outstanding (in shares) | shares	6,000
Series A Preferred Stock | US Treasury (UST) Interest Rate
Class of Stock [Line Items]
Preferred stock, dividend payment rate, Basis spread on variable rate (in percentage)	0.06712
2016 Repurchase Authorization
Class of Stock [Line Items]
Remaining number of shares available under repurchase authorization, value | $	$ 53.3
Maximum | 2016 Repurchase Authorization
Class of Stock [Line Items]
Total number of shares authorized for purchase, value | $					$ 150

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 1,857.8	$ 1,763.7
Other comprehensive (loss) income before reclassifications	(73.3)	62.9
Amounts reclassified from accumulated other comprehensive income	(8)	(12.8)
Net current-period other comprehensive income (loss)	(81.3)	50.1
Ending Balance	1,735.2	1,857.8
Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		(2.2)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(37.9)	(22.6)
Other comprehensive (loss) income before reclassifications	2.6	(15.3)
Amounts reclassified from accumulated other comprehensive income	0	0
Net current-period other comprehensive income (loss)	2.6	(15.3)
Ending Balance	(35.3)	(37.9)
Foreign Currency Translation Adjustments | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		0
Unrealized Holding Gains on Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	105.1	33.5
Other comprehensive (loss) income before reclassifications	(77.4)	78.7
Amounts reclassified from accumulated other comprehensive income	(8)	(12.8)
Net current-period other comprehensive income (loss)	(85.4)	65.9
Ending Balance	19.7	105.1
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) income before reclassifications	1.5	(0.5)
Amounts reclassified from accumulated other comprehensive income	0	0
Net current-period other comprehensive income (loss)	1.5	(0.5)
Ending Balance	(7.1)	(8.6)
Defined Benefit Pension Plans | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		0
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	58.6	2.8
Ending Balance	$ (22.7)	58.6
AOCI Attributable to Parent | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		$ 5.7

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Unrealized gains and losses on securities:
Net realized investment (gains) losses	$ (72.4)	$ (26)	$ (120.9)
Income tax provision (benefit)	(1.4)	7.7	14.1
Net of taxes	(6.7)	54.1	14.1
Unrealized Holding Gains on Securities | Reclassification out of accumulated other comprehensive income
Unrealized gains and losses on securities:
Net realized investment (gains) losses	(12.2)	(12.8)	9.9
Income tax provision (benefit)	4.2	0	(1.2)
Net of taxes	$ (8)	$ (12.8)	$ 8.7

Net (Loss) Income Per Common _3

Net (Loss) Income Per Common Share - Net (Loss) Income Per Common Share on Basic and Diluted Basis (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net income (loss)	$ 6.7	$ (54.1)	$ (14.1)
Dividends on preferred shares	10.5	4.6	0
Net income (loss) attributable to common shareholders, diluted	(3.8)	(58.7)	(14.1)
Net income (loss) attributable to common shareholders, basic	$ (3.8)	$ (58.7)	$ (14.1)
Weighted average common shares outstanding - basic (in shares)	34,816,160	34,614,813	34,205,954
Effect of dilutive securities:
Equity compensation awards (in shares)	0	0	0
Weighted average common shares outstanding - diluted (in shares)	34,816,160	34,614,813	34,205,954
Net income (loss) per common share:
Basic (in dollars per share)	$ (0.11)	$ (1.70)	$ (0.41)
Diluted (in dollars per share)	$ (0.11)	$ (1.70)	$ (0.41)

Net (Loss) Income Per Common _4

Net (Loss) Income Per Common Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Treasury shares (in shares)	11,315,889	11,315,889	11,315,889
Anti-dilutive securities excluded from computation of diluted net income per common share (in shares)	208,524	197,035	587,462

Share-based Compensation - Addi

Share-based Compensation - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment expense		$ 8	$ 8.7	$ 16.9
Share-based payments expense, net of tax		6.9	$ 7.8	15.5
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		$ 9.6
Employee service share-based compensation, unrecognized compensation costs recognition period		2 years 4 months 24 days
Share-based compensation, restricted shares , vested in period, fair value		$ 6.6
Options outstanding (in shares)		278,430	370,027
Stock-Settled SARs Activity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercised (in shares)		129,977
Share based compensation arrangement by share based payment award options exercises, intrinsic value		$ 2.2
Share based compensation arrangement by share based payment award, shares issued (in shares)		10,178
Share based compensation arrangement by share based payment award, shares outstanding (in shares)		10,178
Share-based Payment Arrangement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment expense		$ 0.5	$ 0.7	$ 0.5
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		$ 4.4
Employee service share-based compensation, unrecognized compensation costs recognition period		1 year 8 months 12 days
Share-based compensation, restricted shares , vested in period, fair value		$ 0.4
Options outstanding (in shares)		200,564	157,847
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]
Number of additional shares authorized (in shares)	1,885,000
Expiration period	10 years
2007 Employee Share Purchase Plan
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 months
Discount from market price		85.00%
Earn Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount from market price		85.00%
Earn Plan | 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
Earn Plan | 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		5 years

Share-based Compensation - Summ

Share-based Compensation - Summary of Performance Share Activity (Details) - Performance Shares - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Shares
Options outstanding (in shares)	200,564	157,847
Granted (in shares)	100,291
Vested and issued (in shares)	(8,987)
Expired or forfeited (in shares)	(48,587)
Outstanding, ending balance (in shares)	200,564
Weighted-Average Grant Date Fair Value
Outstanding, weighted-average grant date fair value, beginning balance (in dollars per share)	$ 43.10
Granted (in dollars per share)	54.79
Vested and issued (in dollars per share)	44.49
Expired or forfeited (in dollars per share)	48.74
Outstanding, weighted-average grant date fair value, ending balance (in dollars per share)	$ 47.52

Share-based Compensation - Su_2

Share-based Compensation - Summary of Restricted Share Activity (Detail) - Restricted Stock Units (RSUs)	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Shares
Outstanding, beginning balance (in shares) | shares	370,027
Granted (in shares) | shares	168,011
Vested and issued (in shares) | shares	(143,744)
Expired or forfeited (in shares) | shares	(115,864)
Outstanding, ending balance (in shares) | shares	278,430
Weighted-Average Grant Date Fair Value
Outstanding, weighted-average grant date fair value, beginning balance (in dollars per share) | $ / shares	$ 44.22
Granted (in dollars per share) | $ / shares	55.12
Vested and issued (in dollars per share) | $ / shares	46.08
Expired or forfeited (in dollars per share) | $ / shares	44.88
Outstanding, weighted-average grant date fair value, ending balance (in dollars per share) | $ / shares	$ 49.57

Underwriting, Acquisition and_3

Underwriting, Acquisition and Insurance Expenses (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Underwriting Acquisition And Insurance Expenses [Abstract]
Commissions	$ 289.5	$ 268	$ 241.3
Other underwriting and insurance expenses	428.6	409	412.3
Underwriting, acquisition and insurance expenses, total	718.1	677	653.6
Net deferral of policy acquisition costs	(15.8)	(9.3)	12.4
Total underwriting, acquisition and insurance expenses	$ 702.3	$ 667.7	$ 666

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Increase in deferred tax assets	$ 0.9	$ 7.4
Impact of change in tax rate related to Finance Act 2021			$ (8.3)	$ 0	$ 0
Net operating losses carryback period			2 years
Capital losses carryback period			3 years
Net change in valuation allowance, for deferred tax asset			$ (0.7)
Unrecognized tax benefits	3.6		3.6	8.2	7.5
Decrease in unrecognized tax benefits is reasonably possible	$ 0.6		0.6
Unrecognized tax benefits, interest expense on income taxes			(1)	0.5	0.5
Tax penalty expense			$ (0.8)	$ 0.1	$ 0.2

Income Taxes - Income Tax (Bene

Income Taxes - Income Tax (Benefit) Provision Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current income tax provision (benefit) related to:
United States (Federal)	$ 35.4	$ 28	$ 37.3
United States (State)	2.4	1.4	1.7
United Kingdom	(2.2)	(0.1)	(1.5)
Other jurisdictions	1.6	0	0.1
Total current income tax provision	37.2	29.3	37.6
Deferred income tax provision (benefit) related to:
United States	(26.3)	(5.1)	(17.7)
United Kingdom	(12.3)	(16.6)	(5.8)
Other jurisdictions	0	0.1	0
Total deferred income tax (benefit)	(38.6)	(21.6)	(23.5)
Income tax provision (benefit)	$ (1.4)	$ 7.7	$ 14.1

Income Taxes - Schedule of Pre-

Income Taxes - Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 5.3	$ (46.4)	$ 0
Effective Tax Rate	(26.40%)	(16.60%)	0.00%
Bermuda
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ (18)	$ (56.2)	$ (34.7)
Effective Tax Rate	0.00%	0.00%	0.00%
United States (Federal)
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 65.6	$ 103.3	$ 84.7
Effective Tax Rate	18.10%	22.70%	24.60%
United Kingdom
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ (61.1)	$ (100.6)	$ (45.9)
Effective Tax Rate	24.40%	15.70%	14.90%
Barbados
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0	$ 0	$ 0
Effective Tax Rate	0.00%	0.00%	0.00%
Belgium
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0	$ 0.2	$ 0
Effective Tax Rate	0.00%	30.70%	15.80%
Brazil
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 15.3	$ 3.9	$ 5.2
Effective Tax Rate	10.40%	0.00%	0.00%
United Arab Emirates
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 1.4	$ 2.1	$ 0.4
Effective Tax Rate	0.00%	0.00%	0.00%
Ireland
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ (0.2)	$ 1.8	$ (0.1)
Effective Tax Rate	0.00%	0.00%	0.00%
Italy
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 1.4	$ 0.6	$ (7.4)
Effective Tax Rate	0.00%	0.00%	0.00%
Malta
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.9	$ (1.4)	$ (2)
Effective Tax Rate	0.00%	0.00%	0.00%
Switzerland
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0	$ (0.1)	$ (0.2)
Effective Tax Rate	0.00%	0.00%	(0.20%)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Difference Between Provision for Income Taxes and Expected Tax Provision at Weighted Average Tax Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income tax provision (benefit) at expected rate	$ 9.8	$ 4	$ 8.9
Tax effect of:
Nontaxable investment income	(0.5)	(0.7)	(1.2)
Foreign exchange adjustments	(0.7)	1.6	(0.1)
Impairment of goodwill	8.2	1	2.9
Withholding taxes	0.1	0.1	0.2
Change in uncertain tax position liability	(4.5)	0.7	1.4
Change in valuation allowance	(0.7)	0.5	(1.8)
Impact of change in tax rate related to Finance Act 2021	(8.3)	0	0
Brazil Premiums and Underwriting	(5.3)	0	0
Other	0.5	0.5	3.8
Income tax provision (benefit)	$ (1.4)	$ 7.7	$ 14.1

Income Taxes - Schedule of Net

Income Taxes - Schedule of Net Deferred Tax Liability Comprises Tax Effect Related to Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Losses and loss adjustment expense reserve discounting	$ 35.4	$ 29.2
Unearned premiums	27	25.9
Net operating loss carryforwards	31.6	27.9
Investment in limited partnership interests	21.1	7.8
Unrealized losses on equity securities	8.6	0
Investments	0	2
Right of use assets	13.5	12.7
Accrued bonus	5.8	6.3
Stock option expense	1.1	0.7
United Kingdom underwriting results	28.1	21.9
Other	10.6	9.6
Deferred tax assets, gross	182.8	144
Deferred tax liabilities:
Unrealized gains on equity securities	0	(5.7)
Unrealized gains on fixed maturities and other investment securities	(4.8)	(22.3)
Unrealized gains on limited partnership interests	(26.3)	(14.7)
Investments	(5.1)	0
Depreciable fixed assets	(7.9)	(20.5)
Deferred acquisition costs	(21.3)	(20.4)
Lease liability	(12.2)	(11.7)
TCJA reserve transitional liability	(2.1)	(2.7)
Other	(1.6)	(0.7)
Deferred tax liabilities, gross	(81.3)	(98.7)
Deferred tax assets, net before valuation allowance	101.5	45.3
Valuation allowance	(27.9)	(28.6)
Net deferred assets	73.6	16.7
Foreign Tax Authority
Deferred tax liabilities:
Net deferred assets	35	21.4
Domestic Tax Authority
Deferred tax liabilities:
Net deferred assets	$ 38.6
Net deferred liabilities		$ (4.7)

Income Taxes - Schedule of Ne_2

Income Taxes - Schedule of Net Operating Loss Carryforwards Amounts by Jurisdiction and Year of Expiration (Detail) $ in Millions	Dec. 31, 2021USD ($)
Brazil | Indefinite Expiration
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards by jurisdiction:	$ 6.6
Italy | Indefinite Expiration
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards by jurisdiction:	48.4
Malta | Indefinite Expiration
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards by jurisdiction:	13.7
United Kingdom | Indefinite Expiration
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards by jurisdiction:	17.2
United States (Federal) | Expiration Year From 2025 - 2037
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards by jurisdiction:	$ 40.6

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance at January 1	$ 8.2	$ 7.5
Additions for tax positions of prior years	0	0
Reductions for tax positions of prior years	(0.3)	0
Additions based on tax positions related to current year	0	0.7
Reductions based on tax positions related to current year	0	0
Reductions based on settlements with taxing authorities	(2.8)	0
Expiration of statute of limitations	(1.5)	0
Balance at December 31	$ 3.6	$ 8.2

Pension Benefits and Savings _2

Pension Benefits and Savings Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 0.1	$ 0.1	$ 0.3
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer towards savings plan	9.3	9.2	$ 8.9
Qualified Plan | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Underfunded amount	2.6	4.2
Nonqualified Plan | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Underfunded amount	$ 1.8	$ 2

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - Maximum $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)
Commitments And Contingencies [Line Items]
Contractual commitments related to its limited partnership investments, up to	$ 64.2
Contractual commitments period	12 years

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	Nov. 25, 2020USD ($)	Apr. 30, 2020USD ($)	Dec. 31, 2021USD ($)segment	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of reportable segments | segment			2
Assets associated with trade capital providers			$ 554.2	$ 825.9
Intangible assets derecognized			43.2	0	$ 15.6
Impairment of goodwill and intangibles				0	15.6
Impairment of goodwill and intangibles			43.2	$ 0	$ 15.6
ArgoGlobal Syndicate 1200
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of goodwill and intangibles			28.7
Impairment of goodwill and intangibles			$ 43.2
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Trident
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill derecognized		$ 4.9
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Ariel Re
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill derecognized	$ 9.2
Intangible assets derecognized	$ 30.2

Segment Information - Revenue a

Segment Information - Revenue and Income (Loss) Before Income Taxes for Each Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Earned premiums	$ 1,910.1	$ 1,780.5	$ 1,729.7
Net investment income	187.6	112.7	151.1
Net realized investment and other gains (losses)	32.6	(3.6)	80.1
Total revenue	2,130.3	1,889.6	1,960.9
Foreign currency exchange losses	(1.6)	(15.4)	9.8
Impairment of intangibles	(43.2)	0	(15.6)
Non-operating expenses	(43.7)	(21.1)	(37.6)
Pre-Tax Income (Loss)	5.3	(46.4)	0
U.S. Operations
Segment Reporting Information [Line Items]
Earned premiums	1,283.7	1,207.6	1,119.9
Net investment income	119.4	80.3	100
International Operations
Segment Reporting Information [Line Items]
Earned premiums	625.8	572.5	609.6
Net investment income	50.6	26.7	44.2
Run-off Lines
Segment Reporting Information [Line Items]
Earned premiums	0.6	0.4	0.2
Net investment income	3.6	4	5.7
Operating Segments
Segment Reporting Information [Line Items]
Pre-Tax Income (Loss)	83.7	28.2	8.1
Operating Segments | U.S. Operations
Segment Reporting Information [Line Items]
Earned premiums	1,283.7	1,207.6	1,119.9
Net investment income	119.4	80.3	100
Pre-Tax Income (Loss)	61.1	113.1	139.3
Operating Segments | International Operations
Segment Reporting Information [Line Items]
Earned premiums	625.8	572.5	609.6
Net investment income	50.6	26.7	44.2
Pre-Tax Income (Loss)	64.1	(75.3)	(121.4)
Operating Segments | Run-off Lines
Segment Reporting Information [Line Items]
Earned premiums	0.6	0.4	0.2
Net investment income	3.6	4	5.7
Pre-Tax Income (Loss)	(41.5)	(9.6)	(9.8)
Corporate and Other
Segment Reporting Information [Line Items]
Net investment income	14	1.7	1.2
Pre-Tax Income (Loss)	$ (22.5)	$ (34.5)	$ (44.8)

Segment Information - Schedule

Segment Information - Schedule of Earned Premiums by Geographic Location (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	$ 1,910.1	$ 1,780.5	$ 1,729.7
United States (Federal)
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	1,277	1,205	1,115.8
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	475.3	361.1	391.5
Bermuda
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	54.8	96.5	80.7
Malta
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	35.4	59.5	85
All other jurisdictions
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	$ 67.6	$ 58.4	$ 56.7

Segment Information - Identifia

Segment Information - Identifiable Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 10,317.8	$ 10,465.8
Operating Segments | U.S. Operations
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	5,800.1	5,915.5
Operating Segments | International Operations
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	3,932.3	3,911.9
Operating Segments | Run-off Lines
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	314.7	337.3
Corporate and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 270.7	$ 301.1

Segment Information - Schedul_2

Segment Information - Schedule of Goodwill and Intangible Assets Net of Accumulated Amortization (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Goodwill	$ 147.3	$ 147.3
Intangible Assets, Net of Accumulated Amortization	17.3	60.5
U.S. Operations
Segment Reporting Information [Line Items]
Goodwill	118.6	118.6
Intangible Assets, Net of Accumulated Amortization	0	0
International Operations
Segment Reporting Information [Line Items]
Goodwill	28.7	28.7
Intangible Assets, Net of Accumulated Amortization	$ 17.3	$ 60.5

Statutory Accounting Principl_3

Statutory Accounting Principles - Statutory Capital and Surplus for Principal Operating Subsidiaries (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Bermuda
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 1,425.8	$ 1,483.4
United Kingdom
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	414.8	534.7
United States (Federal)
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 1,177.2	$ 1,072.1

Statutory Accounting Principl_4

Statutory Accounting Principles - Statutory Net Income (Loss) for Principal Operating Subsidiaries (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Bermuda
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	$ 14.2	$ (18)	$ 7.1
United Kingdom
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	8.6	(53)	(15.1)
United States (Federal)
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	$ 103.5	$ 76.4	$ 196.1

Statutory Accounting Principl_5

Statutory Accounting Principles - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Argo Re
Statutory Accounting Practices [Line Items]
Maximum permissible limit for dividend	25.00%
Reduction in total statutory capital	15.00%
Maximum permitted amount of dividends	$ 356.4
Cash dividends	85	$ 58.8	$ 52.1
Argonaut Insurance Company
Statutory Accounting Practices [Line Items]
Maximum permitted amount of dividends	107.1
Rockwood Casualty Insurance Company
Statutory Accounting Practices [Line Items]
Maximum permitted amount of dividends	10.6
Minimum
Statutory Accounting Practices [Line Items]
Minimum statutory capital and surplus balance	$ 126.8	$ 201.3

Insurance Assessments (Detail)

Insurance Assessments (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Insurance [Abstract]
Insurance assessments on current insolvencies	$ 5.8	$ 6.7

Schedule II Condensed Financi_2

Schedule II Condensed Financial Information of Registrant - Schedule of Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash	$ 146.1	$ 148.8
Operating leases right-of-use assets	81.4	82
Other assets	211.6	294.7
Total assets	10,317.8	10,465.8
Liabilities and Shareholders' Equity
Junior subordinated debentures	258.2	257.8
Accrued underwriting expenses and other liabilities	166.6	167.6
Operating lease liabilities	97.7	95.8
Total liabilities	8,582.6	8,608
Shareholders' equity	1,735.2	1,857.8	$ 1,763.7	$ 1,735
Total liabilities and shareholders' equity	10,317.8	10,465.8
Argo Group International Holdings, Ltd (Parent  Guarantor)
Assets
Short-term investments	14.5	0.6
Investment in subsidiaries	1,740.8	1,881.9
Cash	2	3	$ 1.9	$ 1.7
Operating leases right-of-use assets	5.3	6.2
Other assets	5.2	14.5
Total assets	1,767.8	1,906.2
Liabilities and Shareholders' Equity
Junior subordinated debentures	28.4	28.4
Accrued underwriting expenses and other liabilities	3.6	6.3
Operating lease liabilities	5.3	6.2
Due to subsidiaries	(4.7)	7.5
Total liabilities	32.6	48.4
Shareholders' equity	1,735.2	1,857.8
Total liabilities and shareholders' equity	$ 1,767.8	$ 1,906.2

Schedule II Condensed Financi_3

Schedule II Condensed Financial Information of Registrant - Schedule of Statements of Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue:
Net investment expense	$ 187.6	$ 112.7	$ 151.1
Net realized investment (gains) losses	32.6	(3.6)	80.1
Total revenue	2,130.3	1,889.6	1,960.9
Expenses:
Interest expense	21.6	26.9	34.1
Non-operating expenses	43.7	21.1	37.6
Total expenses	2,125	1,936	1,960.9
Net income (loss)	6.7	(54.1)	(14.1)
Dividends on preferred shares	10.5	4.6	0
Net income (loss) attributable to common shareholders, basic	(3.8)	(58.7)	(14.1)
Argo Group International Holdings, Ltd (Parent  Guarantor)
Revenue:
Net investment expense	0	0	(2.9)
Net realized investment (gains) losses	0	(8.3)	(0.1)
Total revenue	0	(8.3)	(3)
Expenses:
Interest expense	1.2	3.6	6.6
Operating expenses	6.2	20.4	1.3
Non-operating expenses	0.2	4.4	26.8
Total expenses	7.6	28.4	34.7
Net income before equity in earnings of subsidiaries	(7.6)	(36.7)	(37.7)
Equity in undistributed earnings of subsidiaries	14.3	(17.4)	23.6
Net income (loss)	6.7	(54.1)	(14.1)
Dividends on preferred shares	10.5	4.6	0
Net income (loss) attributable to common shareholders, basic	$ (3.8)	$ (58.7)	$ (14.1)

Schedule II Condensed Financi_4

Schedule II Condensed Financial Information of Registrant - Schedule of Statements of Cash Flows (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows provided by operating activities:
Net income (loss)	$ 6.7	$ (54.1)	$ (14.1)
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Amortization and depreciation	43.4	33.2	27.3
Share-based payments expense	8	8.7	16.9
Loss on disposals of long-lived assets, net	23.3	5.5	7.2
Change in:
Accrued underwriting expenses and other liabilities	3	(43.7)	(10.6)
Other, net	17.9	9.8	(77)
Net cash flows from operating activities	99.7	71.9	182.8
Cash flows used in investing activities:
Change in short-term investments	(116.4)	285.4	(490.4)
Settlements of foreign currency exchange forward contracts	(1.2)	9.4	0.3
Proceeds from sale of Ariel Re, net of cash transferred	0	28.3	0
Cash used in investing activities	(55.9)	(24.3)	(142.8)
Cash flows from financing activities:
Issuance of preferred shares, net of issuance costs	0	144	0
Activity under stock incentive plans	1.3	1.8	1.9
Payment of cash dividends to preferred shareholders	(10.5)	(4.6)	0
Payment of cash dividends to common shareholders	(43.7)	(43)	(43.1)
Cash used in financing activities	(52.9)	(26.8)	(41.8)
Cash, beginning of year	148.8
Cash, end of period	146.1	148.8
Argo Group International Holdings, Ltd (Parent  Guarantor)
Cash flows provided by operating activities:
Net income (loss)	6.7	(54.1)	(14.1)
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Amortization and depreciation	1.5	1.1	1.3
Share-based payments expense	2.3	3.6	8.1
Net realized investment and other losses (gains)	0	8.3	0.1
Loss on disposals of long-lived assets, net	(3)	0.1	0
Undistributed (losses) earnings of subsidiaries	(14.3)	17.4	(23.6)
Change in:
Prepaid assets	7.2	(2.2)	2.5
Accrued underwriting expenses and other liabilities	(4.1)	(9.1)	7.3
Due (to) from subsidiaries	(12.1)	(11.1)	16.8
Other, net	(3.9)	(7.8)	(12.1)
Net cash flows from operating activities	(19.7)	(53.8)	(13.7)
Cash flows used in investing activities:
Change in short-term investments	(13.9)	0	3.2
Settlements of foreign currency exchange forward contracts	0.5	0.1	(0.2)
Capital contribution to subsidiaries	0	(145.3)	0
Proceeds from sale of Ariel Re, net of cash transferred	0	30	0
Dividend received from subsidiaries	85	71.9	52.1
Cash used in investing activities	71.6	(43.3)	55.1
Cash flows from financing activities:
Issuance of preferred shares, net of issuance costs	0	144	0
Activity under stock incentive plans	1.3	1.8	1.9
Payment of cash dividends to preferred shareholders	(10.5)	(4.6)	0
Payment of cash dividends to common shareholders	(43.7)	(43)	(43.1)
Cash used in financing activities	(52.9)	98.2	(41.2)
Change in cash	(1)	1.1	0.2
Cash, beginning of year	3	1.9	1.7
Cash, end of period	$ 2	$ 3	$ 1.9

Schedule III Supplemental Ins_2

Schedule III Supplemental Insurance Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
DAC	$ 168	$ 163.6	$ 160.2
Reserves for Losses and Loss Adjustment Expenses	5,595	5,406	5,157.6
UPR	1,466.8	1,464.8	1,410.9
Premium Revenue	1,910.1	1,780.5	1,729.7
Net investment income	187.6	112.7	151.1
Loss & LAE	1,314.6	1,208.8	1,220.7
Amortization (Deferral) DAC	(15.8)	(9.3)	12.4
Other Operating Expenses	718.1	677	653.6
Net Premiums Written	1,977.3	1,810.1	1,754.6
U.S. Operations
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
DAC	103.7	98.2	89.7
Reserves for Losses and Loss Adjustment Expenses	3,422.4	3,091.9	2,775.1
UPR	973.7	939.2	896.1
Premium Revenue	1,283.7	1,207.6	1,119.9
Net investment income	119.4	80.3	100
Loss & LAE	908.2	768.7	690.4
Amortization (Deferral) DAC	(5.8)	(8.6)	(2.5)
Other Operating Expenses	425.1	398.3	371.2
Net Premiums Written	1,304.8	1,223	1,166.3
International Operations
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
DAC	64.3	65.4	70.5
Reserves for Losses and Loss Adjustment Expenses	1,911.4	2,077.6	2,129
UPR	493.1	525.4	514.7
Premium Revenue	625.8	572.5	609.6
Net investment income	50.6	26.7	44.2
Loss & LAE	362.1	428.6	518.3
Amortization (Deferral) DAC	(10)	(0.7)	14.9
Other Operating Expenses	256.3	242.3	235.3
Net Premiums Written	671.7	586.6	588.1
Run-off Lines
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
DAC	0	0	0
Reserves for Losses and Loss Adjustment Expenses	261.2	236.5	253.5
UPR	0	0.2	0.1
Premium Revenue	0.6	0.4	0.2
Net investment income	3.6	4	5.7
Loss & LAE	44.3	11.5	12
Amortization (Deferral) DAC	0	0	0
Other Operating Expenses	1	1.7	2.4
Net Premiums Written	0.8	0.5	0.2
Corporate and Other
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
DAC	0	0	0
Reserves for Losses and Loss Adjustment Expenses	0	0	0
UPR	0	0	0
Premium Revenue	0	0	0
Net investment income	14	1.7	1.2
Loss & LAE	0	0	0
Amortization (Deferral) DAC	0	0	0
Other Operating Expenses	35.7	34.7	44.7
Net Premiums Written	$ 0	$ 0	$ 0

Schedule V Valuation and Qual_2

Schedule V Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 28.6	$ 28.1	$ 29.9
Charged to Cost and Expense	(0.7)	0.5	(1.8)
Capital Loss Carryforward	0	0	0
Net Operating Loss Carryforward	0	0	0
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Balance at End of Year	$ 27.9	$ 28.6	$ 28.1

Schedule VI Supplemental Info_2

Schedule VI Supplemental Information for Property-Casualty Insurance Companies (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract]
Deferred acquisition costs	$ 168	$ 163.6	$ 160.2
Reserves for losses and loss adjustment expenses	5,595	5,406	5,157.6
Unamortized discount in reserves for losses	18.8	17.8	17.9
Unearned premiums	1,466.8	1,464.8	1,410.9
Premiums earned	1,910.1	1,780.5	1,729.5
Net investment income	187.6	112.7	151.1
Current year	1,176.3	1,201.1	1,082.6
Prior years	138.3	7.7	138.1
Losses and loss adjustment expenses incurred	1,314.6	1,208.8	1,220.7
Amortization (Deferral) DAC	(15.8)	(9.3)	12.4
Paid losses and loss adjustment expenses, net of reinsurance	869.2	1,119.8	1,030.3
Gross premiums written	$ 3,181.2	$ 3,233.3	$ 3,130.2