Argo Group International (ARGO-PA) 10-Q 6 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Nov. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Trading Symbol	AGII
Entity Registrant Name	Argo Group International Holdings, Ltd.
Entity Central Index Key	1,091,748
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		27,925,756

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	[1]
Assets
Available-for-sale (cost: 2015 - $2,841.7; 2014 - $2,817.2)	$ 2,822.2	$ 2,840.7
Equity securities, at fair value (cost: 2015 - $358.5; 2014 - $307.3)	466	486.3
Other investments (cost: 2015 - $488.1; 2014 - $488.9)	500	495.1
Short-term investments, at fair value (cost: 2015 - $345.0; 2014 - $275.8)	344.8	275.8
Total investments	4,133	4,097.9
Cash	96.2	81
Accrued investment income	21	22.1
Premiums receivable	437.4	353.6
Reinsurance recoverables	1,067.3	997.2
Goodwill	152.2	152.2
Intangible assets, net of accumulated amortization	74.4	78.6
Current income taxes receivable, net	17.1	14.9
Deferred acquisition costs, net	141.4	124.6
Ceded unearned premiums	262.5	207.6
Other assets	225	226.6
Total assets	6,627.5	6,356.3
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses	3,104.1	3,042.4
Unearned premiums	932.7	817.2
Accrued underwriting expenses	131.8	143.1
Ceded reinsurance payable, net	286.4	178.8
Funds held	80.5	55
Senior unsecured fixed rate notes	143.8	143.8
Other indebtedness	57.4	62
Junior subordinated debentures	172.7	172.7
Deferred tax liabilities, net	33.4	53
Other liabilities	43.2	41.6
Total liabilities	$ 4,986	$ 4,709.6
Commitments and contingencies (Note 14)
Shareholders' equity:
Common shares - $1.00 par, 500,000,000 shares authorized; 37,056,534 and 34,318,224 shares issued at September 30, 2015 and December 31, 2014, respectively	$ 37.1	$ 34.3
Additional paid-in capital	961.8	836.3
Treasury shares (9,181,544 and 8,606,489 shares at September 30, 2015 and December 31, 2014, respectively)	(331.1)	(301.4)
Retained earnings	950.2	969.4
Accumulated other comprehensive income, net of taxes	23.5	108.1
Total shareholders' equity	1,641.5	1,646.7
Total liabilities and shareholders' equity	$ 6,627.5	$ 6,356.3
[1]	Derived from audited consolidated financial statements.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	[1]
Statement Of Financial Position [Abstract]
Available-for-sale cost	$ 2,841.7	$ 2,817.2
Equity securities cost	358.5	307.3
Other investments cost	488.1	488.9
Short-term investments, Cost	$ 345	$ 275.8
Common shares, par value	$ 1	$ 1
Common shares, shares authorized	500,000,000	500,000,000
Common shares, shares issued	37,056,534	34,318,224
Treasury shares, shares	9,181,544	8,606,489
[1]	Derived from audited consolidated financial statements.

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Premiums and other revenue:
Earned premiums	$ 346	$ 337.6	$ 1,026.6	$ 999.4
Net investment income	21.3	20.8	63.9	64.7
Fee and other income (expense), net	1	1.6	(0.1)	0.1
Net realized investment and other gains	3.7	12.9	25	42.5
Total revenue	372	372.9	1,115.4	1,106.7
Expenses:
Losses and loss adjustment expenses	200	191.9	574.3	559.5
Underwriting, acquisition and insurance expenses	132.8	133.8	401.9	399.3
Interest expense	4.8	4.9	14.3	15
Foreign currency exchange loss (gain)	(1.8)	(6)	(8.4)	(2.8)
Total expenses	335.8	324.6	982.1	971
Income before income taxes	36.2	48.3	133.3	135.7
Provision for income taxes	0.9	3.6	11.3	12.2
Net income	$ 35.3	$ 44.7	$ 122	$ 123.5
Net income per common share:
Basic	$ 1.27	$ 1.57	$ 4.36	$ 4.28
Diluted	1.24	1.54	4.28	4.21
Dividend declared per common share	$ 0.20	$ 0.16	$ 0.60	$ 0.46
Weighted average common shares:
Basic	27,916,586	28,552,240	27,997,638	28,824,182
Diluted	28,474,504	29,080,608	28,540,094	29,337,175
Net realized investment and other gains before other-than- temporary impairment losses	$ 7.1	$ 13.1	$ 30.3	$ 44.1
Other-than-temporary impairment losses recognized in earnings:
Other-than-temporary impairment losses on fixed maturities	0	0	(0.9)	(1.2)
Other-than-temporary impairment losses on equity securities	(3.4)	(0.2)	(4.4)	(0.4)
Impairment losses recognized in earnings	(3.4)	(0.2)	(5.3)	(1.6)
Net realized investment and other gains	$ 3.7	$ 12.9	$ 25	$ 42.5

Consolidated Statements of Comp

Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 35.3	$ 44.7	$ 122	$ 123.5
Other comprehensive loss:
Foreign currency translation adjustments	(4)	(2.3)	(6.6)	(1.9)
Unrealized (losses) gains on securities:
(Losses) gains arising during the year	(69.7)	(38.8)	(104.3)	16.1
Reclassification adjustment for losses (gains) included in net income	0.1	(5.8)	(6.9)	(22)
Other comprehensive loss before tax	(73.6)	(46.9)	(117.8)	(7.8)
Unrealized (losses) gains on securities:
(Losses) gains arising during the year	(18.3)	(4.9)	(28.6)	10.7
Reclassification adjustment for losses (gains) included in net income	(1.7)	(4.1)	(4.6)	(7.2)
Income tax (benefit) provision related to other comprehensive loss	(20)	(9)	(33.2)	3.5
Other comprehensive (loss) income, net of tax	(53.6)	(37.9)	(84.6)	(11.3)
Comprehensive (loss) income	$ (18.3)	$ 6.8	$ 37.4	$ 112.2

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 122		$ 123.5
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization and depreciation	30.7		27.8
Share-based payments expense	20.8		13.3
Excess tax benefit from share-based payment arrangements	(0.6)		(0.1)
Deferred income tax provision, net	13.8		22.9
Net realized investment and other gains	(25)		(42.5)
Loss on disposals of fixed assets, net	0.2		0
Change in:
Accrued investment income	1.1		3.5
Receivables	(162.2)		214.1
Deferred acquisition costs	(17.6)		(13)
Ceded unearned premiums	(58.5)		(31.2)
Reserves for losses and loss adjustment expenses	75.9		(167.7)
Unearned premiums	123		87.6
Ceded reinsurance payable and funds held	134.3		(159.5)
Income taxes	(2.3)		(35.3)
Accrued underwriting expenses	(19.7)		4.1
Other, net	(0.1)		24.2
Cash provided by operating activities	235.8		71.7
Cash flows from investing activities:
Sales of fixed maturity investments	609.8		884.6
Maturities and mandatory calls of fixed maturity investments	637.4		243.6
Sales of equity securities	61.6		61.8
Sales of other investments	57.4		29.7
Purchases of fixed maturity investments	(1,303.4)		(1,197.3)
Purchases of equity securities	(97.9)		(17.7)
Purchases of other investments	(67.2)		(49.8)
Change in foreign regulatory deposits and voluntary pools	7.5		22.5
Change in short-term investments	(69.9)		(16.5)
Settlements of foreign currency exchange forward contracts	(6.7)		0.6
Purchases of fixed assets	(22)		(26.7)
Other, net	17.4		(21.5)
Cash used by investing activities	(176)		(86.7)
Cash flows from financing activities:
Payment on note payable	0		(0.1)
Redemption of trust preferred securities, net	0		(18)
Activity under stock incentive plans	1.5		3.3
Repurchase of Company's common shares	(29.7)		(40.9)
Excess tax expense from share-based payment arrangements	0.6		0.1
Payment of cash dividends to common shareholders	(17.1)		(13.4)
Cash used by financing activities	(44.7)		(69)
Effect of exchange rate changes on cash	0.1		(0.3)
Change in cash	15.2		(84.3)
Cash, beginning of period	81	[1]	157.4
Cash, end of period	$ 96.2		$ 73.1
[1]	Derived from audited consolidated financial statements.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation	1. Basis of Presentation The accompanying consolidated financial statements of Argo Group International Holdings, Ltd. (“Argo Group,” “we” or the “Company”) and its subsidiaries have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and with the instructions for Form 10-Q and Article 10 of Regulation S-X. The preparation of interim financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. The major estimates reflected in our consolidated financial statements include, but are not limited to, reserves for losses and loss adjustment expenses; reinsurance recoverables, including the reinsurance recoverables allowance for doubtful accounts; estimates of written and earned premiums; reinsurance premium receivable; fair value of investments and assessment of potential impairment; valuation of goodwill and intangibles and our deferred tax asset valuation allowance. Actual results could differ from those estimates. Certain financial information that normally is included in annual financial statements, including certain financial statement footnotes, prepared in accordance with GAAP, is not required for interim reporting purposes and has been condensed or omitted. These statements should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2014, filed with the Securities and Exchange Commission on February 27, 2015. The interim financial information as of, and for the three and nine months ended, September 30, 2015 and 2014 is unaudited. However, in the opinion of management, the interim information includes all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results presented for the interim periods. The operating results for the interim periods are not necessarily indicative of the results to be expected for the full year. All significant intercompany amounts have been eliminated in consolidation. Certain amounts in prior years’ financial statements have been reclassified to conform to the current presentation. 10% Stock Dividend On February 17, 2015, our Board of Directors declared a 10% stock dividend, payable on March 16, 2015, to shareholders of record at the close of business on March 2, 2015. As a result of the stock dividend, 2,554,506 additional shares were issued. Cash was paid in lieu of fractional shares of our common shares. All references to share and per share amounts in this document and related disclosures have been adjusted to reflect the stock dividend for all periods presented.

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	9 Months Ended
	Sep. 30, 2015
Accounting Changes And Error Corrections [Abstract]
Recently Issued Accounting Pronouncements	2 . Recently Issued Accounting Pronouncements In May 2014, the FASB issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers” (Topic 606). The ASU is a comprehensive new revenue recognition model that requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. The ASU provides a five-step analysis of transactions to determine when and how revenue is recognized and requires additional disclosures sufficient to describe the nature, amount, timing and uncertainty of revenue and cash flows for these transactions. This ASU is effective for annual reporting periods beginning after December 15, 2017, with early adoption permitted as early as annual reporting periods beginning after December 15, 2016. We will adopt this ASU on January 1, 2018. Companies may use either a “full retrospective” adoption, meaning the update is applied to all periods presented, or a “modified retrospective” adoption, meaning the update is applied only to the most current period presented in the financial statements. While insurance contracts are excluded from this ASU, fee income related to our brokerage operations and management of the third-party capital for our underwriting Syndicate at Lloyd’s will be subject to this updated guidance. We continue to evaluate what impact this ASU will have on our financial results and disclosures and which adoption method to apply, but no not anticipate such impact being material based on the limited revenue streams subject to the ASU. In February 2015, the FASB issued ASU 2015-02, "Consolidation (Topic 810): Amendments to the Consolidation Analysis." ASU 2015-02 changes the analysis that a reporting entity must perform to determine whether entities should be consolidated if they are deemed variable interest entities. It is effective for annual reporting periods, and interim periods within those years, beginning after December 15, 2015. Early adoption is permitted, including adoption in an interim period. We are currently in the process of evaluating the impact of the adoption of ASU 2015-02 on our consolidated financial statements . In May 2015, the FASB issued ASU 2015-09, “Insurance (Topic 944), Disclosures about Short-Duration Contracts.” ASU 2015-09 requires additional disclosures about short-duration contracts for products in effect for typically a year or less. The disclosures will focus on the liability for unpaid claims and claim adjustment expenses. ASU 2015-09 is effective for annual periods beginning after December 15, 2015 and interim periods within annual periods beginning after December 15, 2016. We are currently in the process of evaluating the impact of the adoption of ASU 2015-09 on our consolidated financial statements.

Investments

Investments	9 Months Ended
	Sep. 30, 2015
Investments Debt And Equity Securities [Abstract]
Investments	3 . Investments Composition of Invested Assets The amortized cost, gross unrealized gains, gross unrealized losses and fair value of investments were as follows: September 30, 2015 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities USD denominated: U.S. Governments $ 167.8 $ 1.4 $ 0.3 $ 168.9 Non-U.S. Governments 87.4 0.4 1.8 86.0 Obligations of states and political subdivisions 473.6 19.4 0.5 492.5 Credit-Financial 491.4 8.2 2.5 497.1 Credit-Industrial 493.0 6.7 6.8 492.9 Credit-Utility 148.8 2.1 7.4 143.5 Structured securities: CMO/MBS-agency (1) 132.8 6.0 0.2 138.6 CMO/MBS-non agency 11.7 0.7 — 12.4 CMBS (2) 165.5 0.9 0.7 165.7 ABS (3) 127.8 0.5 0.3 128.0 CLO (4) 136.0 0.4 0.8 135.6 Foreign denominated: Governments 171.4 1.0 20.1 152.3 Credit 126.0 1.3 18.3 109.0 ABS/CMBS 24.9 0.1 2.9 22.1 CLO 83.6 1.2 7.2 77.6 Total fixed maturities 2,841.7 50.3 69.8 2,822.2 Equity securities 358.5 129.7 22.2 466.0 Other investments 488.1 12.6 0.7 500.0 Short-term investments 345.0 — 0.2 344.8 Total investments $ 4,033.3 $ 192.6 $ 92.9 $ 4,133.0 (1) Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”). (2) Commercial mortgage-backed securities (“CMBS”). (3) Asset-backed securities (“ABS”). (4) December 31, 2014 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities USD denominated: U.S. Governments $ 184.0 $ 1.3 $ 0.3 $ 185.0 Non-U.S. Governments 79.9 0.6 0.6 79.9 Obligations of states and political subdivisions 468.1 22.9 0.3 490.7 Credit-Financial 508.1 12.3 2.3 518.1 Credit-Industrial 493.7 9.4 3.5 499.6 Credit-Utility 142.7 3.2 3.9 142.0 Structured securities: CMO/MBS-agency (1) 168.0 8.0 0.7 175.3 CMO/MBS-non agency 13.2 0.8 — 14.0 CMBS (2) 178.6 1.6 0.2 180.0 ABS (3) 142.7 0.4 0.5 142.6 CLO (4) 78.7 0.2 0.5 78.4 Foreign denominated: Governments 148.4 1.2 9.4 140.2 Credit 136.7 1.8 12.5 126.0 ABS/CMBS 29.5 0.2 2.5 27.2 CLO 44.9 0.7 3.9 41.7 Total fixed maturities 2,817.2 64.6 41.1 2,840.7 Equity securities 307.3 184.1 5.1 486.3 Other investments 488.9 7.5 1.3 495.1 Short-term investments 275.8 — — 275.8 Total investments $ 3,889.2 $ 256.2 $ 47.5 $ 4,097.9 (1) Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”). (2) Commercial mortgage-backed securities (“CMBS”). (3) Asset-backed securities (“ABS”). (4) Included in “Total investments” in our Consolidated Balance Sheets at September 30, 2015 and December 31, 2014 is $78.2 million and $75.2 million, respectively, of assets managed on behalf of the trade capital providers, who are third-party participants that provide underwriting capital to our Syndicate 1200 segment. Contractual Maturity The amortized cost and fair values of fixed maturity investments as of September 30, 2015, by contractual maturity, were as follows: (in millions) Amortized Cost Fair Value Due in one year or less $ 219.8 $ 208.4 Due after one year through five years 1,295.9 1,285.8 Due after five years through ten years 480.4 481.0 Thereafter 163.3 167.0 Structured securities 682.3 680.0 Total $ 2,841.7 $ 2,822.2 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 September 30, 2015 and December 31, 2014 were as follows: September 30, 2015 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 141.3 $ — Private equity 143.7 71.6 Long only funds 195.1 — Other investments 19.9 — Total other invested assets $ 500.0 $ 71.6 December 31, 2014 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 153.2 $ — Private equity 123.6 72.9 Long only funds 200.7 — Other investments 17.6 — Total other invested assets $ 495.1 $ 72.9 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. · Long only funds: These funds include a fund that primarily owns international stocks, a fund that owns high yield fixed income securities and a fund that primarily owns investment-grade corporate and sovereign fixed income securities. · Other investments: Other investments include our participation in pools, foreign exchange currency forward contracts to manage exposure on losses related to global catastrophic events, our Canadian dollar investment portfolio, certain Euro and other non-U.S. dollar denominated investments and to minimize negative impacts to our investment portfolio returns. Unrealized Losses and Other-Than-Temporary Impairments An aging of unrealized losses on our investments in fixed maturities, equity securities, other investments and short-term investments is presented below: September 30, 2015 Less Than One Year One Year or Greater Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Fixed maturities USD denominated: U.S. Governments (2) $ 33.6 $ 0.3 $ 0.4 $ — $ 34.0 $ 0.3 Non-U.S. Governments 32.9 1.5 3.1 0.3 36.0 1.8 Obligations of states and political subdivisions 27.2 0.2 8.5 0.3 35.7 0.5 Credit-Financial 197.9 2.2 19.1 0.3 217.0 2.5 Credit-Industrial 218.4 5.2 30.6 1.6 249.0 6.8 Credit-Utility 75.0 3.9 13.3 3.5 88.3 7.4 Structured securities: CMO/MBS-agency (1) 7.9 — 8.2 0.2 16.1 0.2 CMBS (2) 54.9 0.7 4.5 — 59.4 0.7 ABS (1) 27.5 — 12.1 0.3 39.6 0.3 CLO 95.2 0.7 8.9 0.1 104.1 0.8 Foreign denominated: Governments (2) 136.3 20.1 0.3 — 136.6 20.1 Credit 104.2 18.3 — — 104.2 18.3 ABS/CMBS 21.8 2.9 — — 21.8 2.9 CLO 75.6 7.2 — — 75.6 7.2 Total fixed maturities 1,108.4 63.2 109.0 6.6 1,217.4 69.8 Equity securities 136.0 22.2 — — 136.0 22.2 Other investments (0.4 ) 0.7 — — (0.4 ) 0.7 Short-term investments 20.5 0.2 — — 20.5 0.2 Total $ 1,264.5 $ 86.3 $ 109.0 $ 6.6 $ 1,373.5 $ 92.9 (1) Unrealized losses less than one year are less than $0.1 million. (2) Unrealized losses one year or greater are less than $0.1 million. December 31, 2014 Less Than One Year One Year or Greater Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Fixed maturities USD denominated: U.S. Governments $ 55.0 $ 0.2 $ 15.7 $ 0.1 $ 70.7 $ 0.3 Non-U.S. Governments 36.5 0.4 5.2 0.2 41.7 0.6 Obligations of states and political subdivisions 10.4 0.1 16.6 0.2 27.0 0.3 Credit-Financial 195.7 2.2 11.1 0.1 206.8 2.3 Credit-Industrial 240.8 3.3 12.2 0.2 253.0 3.5 Credit-Utility 63.1 3.8 1.9 0.1 65.0 3.9 Structured securities: CMO/MBS-agency 10.1 0.1 19.2 0.6 29.3 0.7 CMBS 49.3 0.1 6.0 0.1 55.3 0.2 ABS 68.8 0.2 8.1 0.3 76.9 0.5 CLO 60.4 0.5 — — 60.4 0.5 Foreign denominated: Governments 123.7 9.3 11.2 0.1 134.9 9.4 Credit 122.3 12.3 0.9 0.2 123.2 12.5 ABS/CMBS 26.8 2.5 — — 26.8 2.5 CLO 41.7 3.9 — — 41.7 3.9 Total fixed maturities 1,104.6 38.9 108.1 2.2 1,212.7 41.1 Equity securities 53.6 5.1 — — 53.6 5.1 Other investments (0.9 ) 1.3 — — (0.9 ) 1.3 Short-term investments — — — — — — Total $ 1,157.3 $ 45.3 $ 108.1 $ 2.2 $ 1,265.4 $ 47.5 We regularly evaluate our investments for other-than-temporary impairment. For fixed maturity securities, the evaluation for a credit loss is generally based on the present value of expected cash flows of the security as compared to the amortized book value. For structured securities, frequency and severity of loss inputs are used in projecting future cash flows of the securities. Loss frequency is measured as the credit default rate, which includes such factors as loan-to-value ratios and credit scores of borrowers. For equity securities and other investments, the length of time and the amount of decline in fair value are the principal factors in determining other-than-temporary impairment. We also recognize other-than-temporary losses on fixed maturity securities that we intend to sell. We hold a total of 6,805 securities, of which 2,909 were in an unrealized loss position for less than one year and 193 were in an unrealized loss position for a period one year or greater as of September 30, 2015. Unrealized losses greater than twelve months on fixed maturities were the result of a number of factors, including increased credit spreads, foreign currency fluctuations and higher market yields relative to the date the securities were purchased, and for structured securities, by the performance of the underlying collateral, as well. In considering whether an investment is other-than-temporarily impaired or not, we also considered that we do not intend to sell the investments and it is unlikely that we will be required to sell the investments before recovery of their amortized cost bases, which may be maturity. In situations where we did not recognize other-than-temporary losses on investments in our equity portfolio, we have evaluated the near-term prospects of the investment in relation to the severity and duration of the impairment and based on that evaluation, have the ability and intent to hold these investments until a recovery of the cost basis. We do not consider these investments to be other-than-temporarily impaired at September 30, 2015. There was no recognized other-than-temporary loss on our fixed maturities portfolio for the three months ended September 30, 2015 and September 30, 2014. We recognized other-than-temporary losses on our fixed maturities portfolio of $0.9 million and $1.2 million for the nine months ended September 30, 2015 and 2014, respectively. We recognized other-than-temporary losses on our equity portfolio of $3.4 million and $4.4 million for the three and nine months ended September 30, 2015, respectively. We recognized other-than-temporary losses on our equity portfolio of $0.2 million and $0.4 million for the three and nine months ended September 30, 2014, respectively. Realized Gains and Losses The following table presents our gross realized investment and other gains (losses): For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Realized gains Fixed maturities $ 2.9 $ 4.5 $ 10.5 $ 15.2 Equity securities 9.8 0.7 22.6 16.1 Other investments 14.6 13.6 44.9 36.5 Short-term investments — — 1.1 0.1 Other assets — 2.0 — 2.0 Gain on sale of real estate holdings — — 0.4 — Gross realized investment gains 27.3 20.8 79.5 69.9 Realized losses Fixed maturities (4.1 ) (1.1 ) (13.1 ) (8.7 ) Equity securities (2.5 ) (0.1 ) (3.6 ) (0.2 ) Other investments (13.4 ) (6.5 ) (30.9 ) (12.6 ) Short-term investments (0.1 ) — (1.5 ) (0.3 ) Other assets (0.1 ) — (0.1 ) (4.0 ) Other-than-temporary impairment losses on fixed maturities — — (0.9 ) (1.2 ) Other-than-temporary impairment losses on equity securities (3.4 ) (0.2 ) (4.4 ) (0.4 ) Gross realized investment and other losses (23.6 ) (7.9 ) (54.5 ) (27.4 ) Net realized investment and other gains $ 3.7 $ 12.9 $ 25.0 $ 42.5 The cost of securities sold is based on the specific identification method. Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments are summarized as follows: (in millions) Fixed Maturities Equity Maturities Other Investments Short Term Real Estate Holdings and Other Tax Effects Total Three Months Ended September 30, 2015 Realized before impairments $ (1.2 ) $ 7.3 $ 1.2 $ (0.1 ) $ (0.1 ) $ (2.1 ) $ 5.0 Realized - impairments — (3.4 ) — — — 1.2 (2.2 ) Change in unrealized (22.6 ) (46.7 ) — (0.2 ) — 20.1 (49.4 ) Three Months Ended September 30, 2014 Realized before impairments $ 3.4 $ 0.6 $ 7.1 $ — $ 2.0 $ (5.3 ) $ 7.8 Realized - impairments — (0.2 ) — — — 0.4 0.2 Change in unrealized (33.9 ) (10.7 ) — — — 9.0 (35.6 ) Nine Months Ended September 30, 2015 Realized before impairments $ (2.6 ) $ 19.0 $ 14.0 $ (0.4 ) $ 0.3 $ (10.5 ) $ 19.8 Realized - impairments (0.9 ) (4.4 ) — — — 1.8 (3.5 ) Change in unrealized (40.9 ) (71.5 ) 1.5 (0.2 ) — 33.3 (77.8 ) Nine Months Ended September 30, 2014 Realized before impairments $ 6.5 $ 15.9 $ 23.9 $ (0.2 ) $ (2.0 ) $ (13.4 ) $ 30.7 Realized - impairments (1.2 ) (0.4 ) — — — 0.5 (1.1 ) Change in unrealized (12.0 ) 5.0 1.1 — — (3.5 ) (9.4 ) We entered into foreign currency exchange forward contracts to manage currency exposure on losses related to certain global catastrophe events. We did not renew this program in the third quarter of 2015 as the currency exposure has become immaterial. These currency forward contracts were carried at fair value in our Consolidated Balance Sheets in “Other investments” at September 30, 2014. The realized and unrealized gains and losses on these contracts are included in “Net realized investment and other gains” in our Consolidated Statements of Income. The notional amount of these currency forward contracts was $25.6 million at September 30, 2014. The fair value of these currency forward contracts was a loss of $2.0 million at September 30, 2014. For the three and nine months ended September 30, 2015, we recognized $0.0 million and $0.5 million in realized gains and $0.3 million and $2.3 million in realized losses, respectively, from these currency forward contracts. For the three and nine months ended September 30, 2014, we recognized $0.1 million and $3.9 million in realized gains and $2.2 million and $4.1 million in realized losses, respectively, from these currency forward contracts. We enter into foreign currency exchange forward contracts to manage currency exposure on our Canadian dollar (“CAD”) investment portfolio, certain Euro and other non-U.S. dollar denominated investments, and to minimize negative impacts to our investment portfolio returns. The currency forward contracts are carried at fair value in our Consolidated Balance Sheets in “Other investments.” The realized and unrealized gains and losses are included in “Net realized investment and other gains” in our Consolidated Statements of Income. The notional amount of the Canadian dollar forward contracts was CAD 160.7 million (USD $119.9 million) and CAD 132.0 million (USD $118.3 million) as of September 30, 2015 and 2014, respectively. The notional amount of the remaining forward contracts was not material as of September 30, 2015 and 2014. The fair value of the currency forward contracts was a gain of $5.1 million and a loss of $0.4 million as of September 30, 2015 and 2014, respectively. For the three and nine months ended September 30, 2015, we recognized $8.6 million and $26.4 million in realized gains and $3.9 million and $13.4 million in realized losses, respectively, from the currency forward contracts. For both the three and nine months ended September 30, 2014, we recognized $5.7 million and $2.6 million in realized gains and realized losses, respectively. Regulatory Deposits, Pledged Securities and Letters of Credit At September 30, 2015, the amortized cost and fair value of investments on deposit with U.S., Canadian and various other agencies for regulatory purposes were $185.9 million and $192.3 million, respectively. At December 31, 2014, the amortized cost and fair value of investments on deposit with U.S., Canadian and various other agencies for regulatory purposes were $186.6 million and $194.2 million, respectively. At September 30, 2015, investments with an amortized cost of $34.6 million and fair value of $34.8 million were pledged as collateral in support of irrevocable letters of credit (“LOCs”) in the amount of $28.2 million issued under the terms of certain reinsurance agreements in respect of reported loss and loss expense reserves. At December 31, 2014, investments with an amortized cost of $55.0 million and fair value of $55.3 million were pledged as collateral in support of irrevocable LOCs in the amount of $43.6 million issued under the terms of certain reinsurance agreements in respect of reported loss and loss expense reserves. Our Corporate member’s capital supporting our Lloyd’s business was $211.9 million and $217.9 million at September 30, 2015 and December 31, 2014, respectively. Fair Value Measurements Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurement assumes that the transaction to sell the asset or transfer the liability occurs in the principal market for the asset or liability, or in the absence of a principal market, the most advantageous market. Market participants are buyers and sellers in the principal (or most advantageous) market that are independent, knowledgeable, able to transact for the asset or liability and willing to transfer the asset or liability. Valuation techniques consistent with the market approach, income approach and/or cost approach are used to measure fair value. The inputs of these valuation techniques are categorized into three levels. ● ● ● 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 September 30, 2015. 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: ● ● ● 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 are obtained from the National Association of Insurance Commissioners’ Security Valuation Office at the reporting date. — 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. 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. Foreign currency future contracts are valued by our counterparty using market driven foreign currency exchange rates and are considered Level 2 investments. Short-term Investments: Short-term investments are principally reported at fair value using Level 1 inputs, with the exception of short-term corporate 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. Transfers Between Level 1 and Level 2 Securities: There were no transfers between Level 1 and Level 2 securities during the three months ended September 30, 2015. 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) September 30, 2015 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities USD denominated: U.S. Governments $ 168.9 $ 110.4 $ 58.5 $ — Non-U.S. Governments 86.0 — 86.0 — Obligations of states and political subdivisions 492.5 — 492.5 — Credit-Financial 497.1 — 497.1 — Credit-Industrial 492.9 — 492.9 — Credit-Utility 143.5 — 143.5 — Structured securities: CMO/MBS-agency 138.6 — 138.6 — CMO/MBS-non agency 12.4 — 12.4 — CMBS 165.7 — 165.7 — ABS 128.0 — 128.0 — CLO 135.6 — 135.6 — Foreign denominated: Governments 152.3 — 152.3 — Credit 109.0 — 109.0 — ABS/CMBS 22.1 — 22.1 — CLO 77.6 — 77.6 — Total fixed maturities 2,822.2 110.4 2,711.8 — Equity securities 466.0 465.2 — 0.8 Other investments 91.2 — 91.2 — Short-term investments 344.8 323.8 21.0 — $ 3,724.2 $ 899.4 $ 2,824.0 $ 0.8 (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, 2014 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities USD denominated: U.S. Governments $ 185.0 $ 99.2 $ 85.8 $ — Non-U.S. Governments 79.9 — 79.9 — Obligations of states and political subdivisions 490.7 — 490.7 — Credit-Financial 518.1 — 518.1 — Credit-Industrial 499.6 — 499.6 — Credit-Utility 142.0 — 142.0 — Structured securities: CMO/MBS-agency 175.3 — 175.3 — CMO/MBS-non agency 14.0 — 14.0 — CMBS 180.0 — 180.0 — ABS 142.6 — 142.6 — CLO 78.4 — 78.4 — Foreign denominated: Governments 140.2 — 140.2 — Credit 126.0 — 126.0 — ABS/CMBS 27.2 — 27.2 — CLO 41.7 — 41.7 — Total fixed maturities 2,840.7 99.2 2,741.5 — Equity securities 486.3 485.4 — 0.9 Other investments 97.3 — 97.3 — Short-term investments 275.8 273.9 1.9 — $ 3,700.1 $ 858.5 $ 2,840.7 $ 0.9 (a) Quoted prices in active markets for identical assets (b) Significant other observable inputs (c) Significant unobservable inputs The fair value measurements in the tables above do not equal “Total investments” on our Consolidated Balance Sheets as they exclude certain other investments that are accounted for under the equity-method of accounting. A reconciliation of the beginning and ending balances for the investments categorized as Level 3 are as follows: Fair Value Measurements Using Observable Inputs (Level 3) (in millions) Equity Securities Total Beginning balance, January 1, 2015 $ 0.9 $ 0.9 Transfers into Level 3 — — Transfers out of Level 3 — — Total gains or losses (realized/unrealized): Included in net income (loss) — — Included in other comprehensive income (loss) — — Purchases, issuances, sales, and settlements Purchases — — Issuances — — Sales (0.1 ) (0.1 ) Settlements — — Ending balance, September 30, 2015 $ 0.8 $ 0.8 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 September 30, 2015 $ — $ — (in millions) Equity Securities Other Assets Total Beginning balance, January 1, 2014 $ 1.3 $ 2.6 $ 3.9 Transfers into Level 3 — — — Transfers out of Level 3 — — — Total gains or losses (realized/unrealized): Included in net income (loss) — — — Included in other comprehensive income (loss) 0.1 — 0.1 Purchases, issuances, sales, and settlements Purchases — — — Issuances — — — Sales (0.5 ) — (0.5 ) Settlements — (2.6 ) (2.6 ) Ending balance, December 31, 2014 $ 0.9 $ — $ 0.9 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 December 31, 2014 $ — $ — $ — At September 30, 2015 and December 31, 2014, 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.

Reserves for Losses and Loss Ad

Reserves for Losses and Loss Adjustment Expenses	9 Months Ended
	Sep. 30, 2015
Insurance [Abstract]
Reserves for Losses and Loss Adjustment Expenses	4 . Reserves for Losses and Loss Adjustment Expenses The following table provides a reconciliation of reserves for losses and loss adjustment expenses (“LAE”): For the Nine Months Ended September 30, (in millions) 2015 2014 Net reserves beginning of the year $ 2,137.1 $ 2,107.6 Add: Losses and LAE incurred during current calendar year, net of reinsurance: Current accident year 589.6 585.9 Prior accident years (15.3 ) (26.4 ) Losses and LAE incurred during calendar year, net of reinsurance 574.3 559.5 Deduct: Losses and LAE payments made during current calendar year, net of reinsurance: Current accident year 105.2 115.3 Prior accident years 435.5 435.5 Losses and LAE payments made during current calendar year, net of reinsurance: 540.7 550.8 Change in participation interest (1) (1.2 ) 24.7 Foreign exchange adjustments (27.7 ) (4.9 ) Net reserves - end of period 2,141.8 2,136.1 Add: Reinsurance recoverables on unpaid losses and LAE, end of period 962.3 926.5 Gross reserves - end of period $ 3,104.1 $ 3,062.6 (1) Amount represents (decreases) increases in reserves due to change in syndicate 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. Impacting losses and LAE for the nine months ended September 30, 2015 was $15.3 million in favorable prior years’ loss reserve development comprised of the following: $25.1 million of net favorable development in the Excess and Surplus Lines segment primarily the result of favorable development in the general and products liability lines and commercial automobile, partially offset by unfavorable development in property lines; $10.4 million of net unfavorable development in the Commercial Specialty segment, primarily driven by unfavorable development in general liability and workers compensation due to increases in claim severity, partially offset by favorable development in auto liability and short tail lines; $5.8 million of net favorable development in the International Specialty segment primarily driven by favorable development in Argo Insurance Bermuda and Argo Re, partially offset by unfavorable development in the Brazil unit; $2.8 million of net favorable development in the Syndicate 1200 segment primarily driven by favorable development in property, general liability and marine & energy, partially offset by unfavorable development in other liability classes and aerospace; and $8.0 million of unfavorable development in the Run-off Lines segment primarily caused by unfavorable development in workers compensation lines and asbestos and environmental liability, offset in part by favorable development in run-off reinsurance claims. Impacting losses and LAE for the nine months ended September 30, 2014 was $26.4 million in favorable prior years’ loss reserve development comprised of the following: $34.6 million of net favorable development in the Excess and Surplus Lines segment primarily caused by favorable development in the general and products liability lines, partially offset by unfavorable development in commercial automobile and property lines; $5.2 million of net unfavorable development in the Commercial Specialty segment, primarily driven by unfavorable development in general liability lines due to increases in claim severity, as well as unfavorable development in auto liability lines, partially offset by favorable development in workers compensation and short-tail lines; $0.1 million of net favorable development in the International Specialty segment; $15.8 million of net favorable development in the Syndicate 1200 segment primarily driven by favorable development in various property classes, as well as favorable development in professional indemnity and aerospace, partially offset by unfavorable development in general liability; and $18.9 million of unfavorable development in the Run-off Lines segment primarily caused by unfavorable development in workers compensation lines driven by increasing medical costs on older claims, as well as unfavorable development in asbestos liability on assumed 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 assumptions considered reasonable where facts are not known. Due to the significant uncertainties and related management judgments, there can be no assurance that future loss development, favorable or unfavorable, will not occur.

Debt

Debt	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Debt	5 . Debt Revolving Credit Facility On March 7, 2014, each of Argo Group, Argo Group US, Inc., Argo International Holdings Limited and Argo Underwriting Agency Limited (the “Borrowers”) entered into a $175 million credit agreement (“Credit Agreement”) with JPMorgan Chase Bank, N.A., as administrative agent. The Credit Agreement provides for a $175.0 million revolving credit facility with a maturity date of March 7, 2018 unless extended in accordance with the terms of the Credit Agreement. Borrowings under the Credit Agreement may be used for general corporate purposes, including working capital and permitted acquisitions, 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 might be required immediately to repay all amounts outstanding under the Credit Agreement. Lenders holding at least a majority of the loans and commitments under the Credit Agreement may 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 $17.5 million of the revolving credit facility to be used for LOCs, subject to availability. As of September 30, 2015 and December 31, 2014, there were no borrowings outstanding and $0.2 million in LOCs against the Credit Facility. Junior Subordinated Debentures On July 16, 2014, Argo Group US, Inc. purchased the outstanding PXRE Capital Trust V $20,000,000 Junior Subordinated Debt Securities (“Capital Trust V”) at a discount equal to 90.0% of the principal amount plus accrued and unpaid interest through the date of purchase for a total price of $18.2 million, resulting in the recognition of a $2.0 million pre-tax realized gain. The Capital Trust V was redeemed on April 29, 2015.

Disclosures about Fair Value of

Disclosures about Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Disclosures about Fair Value of Financial Instruments	6. 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 approximates fair value. At September 30, 2015 and December 31, 2014, the carrying values of premiums receivable over 90 days were $12.2 million and $12.4 million, respectively. Included in “Reinsurance recoverables” in our Consolidated Balance Sheets at September 30, 2015 and December 31, 2014, are amounts that are due from trade capital providers associated with the operations of Syndicate 1200. Upon settlement, the receivable is offset against the liability also reflected in our accompanying Consolidated Balance Sheets. At September 30, 2015 and December 31, 2014, the payable was in excess of the receivable. Of our reinsurance recoverables on paid losses, excluding amounts attributable to Syndicate 1200’s trade capital providers, at September 30, 2015 and December 31, 2014, the carrying values over 90 days were $9.1 million and $9.9 million, respectively. Our methodology for establishing our allowances for doubtful accounts includes specifically identifying all potential uncollectible balances regardless of aging. At September 30, 2015 and December 31, 2014, the allowance for doubtful accounts for premiums receivable was $3.7 million and $5.2 million, respectively, and the allowance for doubtful accounts for reinsurance recoverables on paid losses was $2.4 million and $1.8 million, respectively. Premiums receivable over 90 days were secured by collateral in the amount of $0.3 million and $0.3 million at September 30, 2015 and December 31, 2014, respectively. Reinsurance recoverables on paid losses over 90 days were secured by collateral in the amount of $0.6 million and $0.4 at September 30, 2015 and December 31, 2014, respectively. Debt . At September 30, 2015 and December 31, 2014, the fair value of our Junior subordinated debentures, Senior unsecured fixed rate notes and Other indebtedness was estimated using appropriate market indices or quoted prices from external sources based on current market conditions. A summary of our financial instruments whose carrying value did not equal fair value is shown below: September 30, 2015 December 31, 2014 (in millions) Carrying Amount Fair Value Carrying Amount Fair Value Junior subordinated debentures $ 172.7 $ 153.0 $ 172.7 $ 155.5 Senior unsecured fixed rate notes 143.8 144.6 143.8 132.3 Other indebtedness: Floating rate loan stock 56.8 50.3 61.3 55.2 Note payable 0.6 0.6 0.7 0.6 $ 373.9 $ 348.5 $ 378.5 $ 343.6

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Shareholders' Equity	7 . Shareholders’ Equity On February 17, 2015, our Board of Directors declared a 10% stock dividend, payable on March 16, 2015, to shareholders of record at the close of business on March 2, 2015. As a result of the stock dividend, 2,554,506 additional shares were issued. Cash was paid in lieu of fractional shares of our common shares. All references to share and per share amounts in this document and related disclosures have been adjusted to reflect the stock dividend for all periods presented. On August 4, 2015, our Board of Directors declared a quarterly cash dividend in the amount of $0.20 on each share of common stock outstanding. On September 15, 2015, we paid $5.6 million to our shareholders of record on September 1, 2015. On August 5, 2014, our Board of Directors declared a quarterly cash dividend in the amount of $0.16 on each share of common stock outstanding, on a post-stock dividend basis. On September 15, 2014, we paid $4.7 million to our shareholders of record on September 1, 2014. On November 5, 2013, our Board of Directors authorized the repurchase of up to $150.0 million of our common shares (“2013 Repurchase Authorization”). The 2013 Repurchase Authorization supersedes all the previous Repurchase Authorizations. As of September 30, 2015, availability under the 2013 Repurchase Authorization for future repurchases of our common shares was $63.1 million. For the three and nine months ended September 30, 2015, we repurchased a total of 85,959 common shares and 575,055, respectively, for $4.8 million and $29.7 million, respectively. A summary of activity from January 1, 2015 through September 30, 2015 follows A summary of common shares repurchased for the nine months ended September 30, 2015 is shown below: Repurchase Type Date Trading Plan Initiated 2015 Purchase Period Number of Shares Repurchased Average Price of Shares Repurchased Total Cost (in millions) Repurchase Authorization Year 10b5-1 Trading Plan 12/15/2014 01/05/2015-02/12/2015 117,482 $ 53.50 $ 6.3 2013 10b5-1 Trading Plan 03/16/2015 03/18/2015-05/06/2015 150,050 $ 49.56 7.4 2013 Open Market N/A 01/01/2015-09/30/2015 307,523 $ 51.83 16.0 2013 Total 575,055 $ 51.58 $ 29.7

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	8 . Accumulated Other Comprehensive Income (Loss) A summary of changes in accumulated other comprehensive income (loss), net of taxes (where applicable) by component for the nine months ended September 30, 2015 and 2014 is presented below: (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance, January 1, 2015 $ (15.6 ) $ 130.7 $ (7.0 ) $ 108.1 Other comprehensive loss before reclassifications (6.6 ) (75.7 ) — (82.3 ) Amounts reclassified from accumulated other comprehensive loss — (2.3 ) — (2.3 ) Net current-period other comprehensive loss (6.6 ) (78.0 ) — (84.6 ) Balance at September 30, 2015 $ (22.2 ) $ 52.7 $ (7.0 ) $ 23.5 (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance, January 1, 2014 $ (11.5 ) $ 163.9 $ (4.6 ) $ 147.8 Other comprehensive income before reclassifications (1.9 ) 5.4 — 3.5 Amounts reclassified from accumulated other comprehensive income — (14.8 ) — (14.8 ) Net current-period other comprehensive income (1.9 ) (9.4 ) — (11.3 ) Balance at September 30, 2014 $ (13.4 ) $ 154.5 $ (4.6 ) $ 136.5 The following tables illustrate the amounts reclassified from accumulated other comprehensive (loss) income shown in the above tables that have been included in our Consolidated Statements of Income: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Unrealized gains and losses on securities: Net realized investment losses $ 0.1 $ (5.8 ) $ (6.9 ) $ (22.0 ) Benefit for income taxes 1.7 4.1 4.6 7.2 Net of taxes $ 1.8 $ (1.7 ) $ (2.3 ) $ (14.8 )

Net Income Per Common Share

Net Income Per Common Share	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Net Income Per Common Share	9. Net Income Per Common Share The following table presents the calculation of net income per common share on a basic and diluted basis (all balances have been adjusted to reflect the 10% stock dividend): For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions, except number of shares and per share amounts) 2015 2014 2015 2014 Net income $ 35.3 $ 44.7 $ 122.0 $ 123.5 Weighted average common shares outstanding - basic 27,916,586 28,552,240 27,997,638 28,824,182 Effect of dilutive securities: Equity compensation awards 557,918 528,368 542,456 512,993 Weighted average common shares outstanding - diluted 28,474,504 29,080,608 28,540,094 29,337,175 Net income per common share: Basic $ 1.27 $ 1.57 $ 4.36 $ 4.28 Diluted $ 1.24 $ 1.54 $ 4.28 $ 4.21 Excluded from the weighted average common shares outstanding calculation at September 30, 2015, and 2014 are 9,181,544 shares and 8,440,355 shares, respectively, which are held as treasury shares. The shares are excluded as of their repurchase date. For the three and nine months ended September 30, 2015, there were no equity compensation awards with an anti-dilutive effect. For the three and nine months ended September 30, 2014, equity compensation awards to purchase 1,879 shares of common stock were excluded from the computation of diluted net income per common share as these instruments were anti-dilutive. These instruments expired or will expire at varying times from 2014 through 2016.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2015
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	10 . Supplemental Cash Flow Information Income taxes paid. We paid income taxes of $ 10.8 million and $23.8 million during the nine months ended September 30, 2015 and 2014, respectively. Income taxes recovered . During the nine months ended September 30, 2015, $11.5 million of income taxes was recovered. No income taxes were recovered during the nine months ended September 30, 2014. Interest paid was as follows: For the Nine Months Ended September 30, (in millions) 2015 2014 Senior unsecured fixed rate notes $ 7.0 $ 7.0 Junior subordinated debentures 5.3 5.8 Other indebtedness 2.0 2.3 Total interest paid $ 14.3 $ 15.1

Share-based Compensation

Share-based Compensation	9 Months Ended
	Sep. 30, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based Compensation	11. Share-based Compensation The fair value method of accounting is used for equity-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. We use the Black-Scholes model to estimate the fair values on the measurement date for share options and share appreciation rights (“SARs”). The Black-Scholes model uses several assumptions to value a share award. The volatility assumption is based on the historical change in our stock price over the previous five years preceding the measurement date. The risk-free rate of return assumption is based on the five-year U.S. Treasury constant maturity rate on the measurement date. The expected award life is based upon the average holding period over the history of the incentive plan. The expected dividend yield is based on our history and expected dividend payouts. The following table summarizes the assumptions we used for the nine months ended September 30, 2015 and 2014: For the Nine Months Ended September 30, 2015 2014 Risk-free rate of return 1.44% 1.77% Expected dividend yields 1.52% 1.49% Expected award life (years) 4.64 4.67 Expected volatility 20.81% 22.84% All outstanding awards were adjusted to reflect the 10% stock dividend, resulting in a 10% increase to the number of awards outstanding and a 9.09% reduction in the exercise price. Argo Group’s Long-Term Incentive Plans In November 2007, our shareholders approved the 2007 Long-Term Incentive Plan (the “2007 Plan”), which provides for an aggregate of 4.5 million shares of our common stock that may be issued to executives, non-employee directors, and other key employees. As of May 2014, 1.46 million shares remained available for grant under the 2007 Plan. In May 2014, our shareholders approved the 2014 Long-Term Incentive Plan (the “2014 Plan”), which provides for an additional 2.8 million shares of our common stock to be available for issuance to executives, non-employee directors and other key employees. The share awards may be in the form of share options, SARs, restricted shares, restricted share awards, restricted share units awards, performance awards, other share-based awards and other cash-based awards. 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. Share options and SARs will count as one share for the purposes of the limits under the incentive plans; restricted shares, restricted share units, performance units, performance shares or other share-based incentive awards which settle in common shares will count as 2.75 shares for purpose of the limits under the 2014 Plan. Share options may be in the form of incentive share options, non-qualified share options and restorative options. Share options are required to have an exercise price that is not less than the market value on the date of grant. We are prohibited from repricing the options. The term of the share options cannot exceed seven years from the grant date. A summary of restricted share activity as of September 30, 2015 and changes during the nine months then ended is as follows: Shares Weighted-Average Grant Date Fair Value Outstanding at January 1, 2015 313,716 $ 31.38 Granted 297,873 $ 39.21 Vested and issued (119,295 ) $ 26.83 Expired or forfeited (8,938 ) $ 41.76 Outstanding at September 30, 2015 483,356 $ 37.14 The restricted shares vest over two to four years. Expense recognized under this plan for the restricted shares was $1.4 million and $4.4 million for the three and nine months ended September 30, 2015, respectively, as compared to $0.8 million and $2.2 million for the three and nine months ended September 30, 2014, respectively. Compensation expense for all share-based compensation awards is included in “Underwriting, acquisition and insurance expense” in the accompanying Consolidated Statements of Income. As of September 30, 2015, there was $13.9 million of total unrecognized compensation cost related to restricted share compensation arrangements granted by Argo Group. A summary of stock-settled SARs activity as of September 30, 2015 and changes during the nine months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2015 1,313,726 $ 28.57 Granted 243,305 $ 39.43 Exercised (165,036 ) $ 24.15 Expired or forfeited (7,231 ) $ 31.68 Outstanding at September 30, 2015 1,384,764 $ 30.14 The stock-settled SARs vest over a one to four year period. Upon exercise of the stock-settled SARs, the employee is entitled to receive shares of our common stock equal to the appreciation of the stock as compared to the exercise price. Expense recognized for the stock-settled SARs was $0.3 million and $1.3 for the three and nine months ended September 30, 2015, respectively, as compared to $0.3 million and $1.6 million for the three and nine months ended September 30, 2014, respectively. As of September 30, 2015, there was $3.3 million of total unrecognized compensation cost related to stock-settled SARs outstanding. A summary of cash-settled SARs activity as of September 30, 2015 and changes during the nine months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2015 2,001,451 $ 32.76 Granted 913,157 $ 47.48 Exercised (366,527 ) $ 29.19 Expired or forfeited (216,354 ) $ 39.40 Outstanding at September 30, 2015 2,331,727 $ 38.46 The cash-settled SARs vest over a one to four year period. Upon exercise of the cash-settled SARs, the employee is entitled to receive cash payment for the appreciation in the value of our common stock over the exercise price. We account for the cash-settled SARs as liability awards, which require the awards to be revalued at each reporting period. Expense recognized for the cash-settled SARs was $2.8 million and $14.1 million for the three and nine months ended September 30, 2015, respectively, as compared to $1.2 million and $9.2 million for the three and nine months ended September 30, 2014, respectively. As of September 30, 2015, there was $13.2 million of total unrecognized compensation cost related to cash-settled SARs outstanding.

Underwriting, Acquisition and I

Underwriting, Acquisition and Insurance Expenses	9 Months Ended
	Sep. 30, 2015
Underwriting Acquisition And Insurance Expenses [Abstract]
Underwriting, Acquisition and Insurance Expenses	12 . Underwriting, Acquisition and Insurance Expenses Underwriting, acquisition and insurance expenses were as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Commissions $ 56.5 $ 59.8 $ 182.4 $ 178.0 General expenses 69.6 69.0 222.2 211.9 Premium taxes, boards and bureaus 7.5 7.2 8.1 19.5 133.6 136.0 412.7 409.4 Net deferral of policy acquisition costs (0.8 ) (2.2 ) (10.8 ) (10.1 ) Total underwriting, acquisition and insurance expenses $ 132.8 $ 133.8 $ 401.9 $ 399.3 Included in general expenses for the three months ended September 30, 2015 and 2014 was $5.5 million and $2.2 million, respectively, and $20.8 million and $13.3 million for the nine months ended September 30, 2015 and 2014, respectively, of expense for our total equity compensation.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	13 . 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 United States or the United Kingdom and, accordingly, do not expect to be subject to direct United States or United Kingdom income taxation. We have subsidiaries based in the United Kingdom that are subject to the tax laws of that country. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Six of the United Kingdom subsidiaries are deemed to be engaged in business in the United States, and therefore, are subject to United States corporate tax in respect of a proportion of their United States underwriting business only. Relief is available against the United Kingdom tax liabilities in respect of overseas taxes paid that arise from the underwriting business. Corporate income tax losses incurred in the United Kingdom can be carried forward, for application against future income, indefinitely. Our United Kingdom subsidiaries file separate United Kingdom income tax returns. We have subsidiaries based in the United States that are subject to United States tax laws. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Our United States subsidiaries file a consolidated United States federal income tax return. We also have operations in Belgium, Switzerland, Brazil, France, Malta, Spain and Ireland, which also are subject to income taxes imposed by the jurisdiction in which they operate. We have operations in the United Arab Emirates, which are not subject to income tax under the laws of that country. Our income tax provision includes the following components: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Current tax provision $ (11.3 ) $ (15.0 ) $ (2.5 ) $ (10.7 ) Deferred tax (benefit) provision related to: Future tax deductions 14.1 19.7 16.7 52.9 Valuation allowance change (1.9 ) (1.1 ) (2.9 ) (30.0 ) Income tax provision $ 0.9 $ 3.6 $ 11.3 $ 12.2 Our expected income tax provision computed on pre-tax income (loss) at the weighted average tax rate has been calculated as the sum of the pre-tax income (loss) in each jurisdiction multiplied by that jurisdiction’s applicable statutory tax rate. For the three and nine months ended September 30, 2015 and 2014, pre-tax income (loss) attributable to our operations and the operations’ effective tax rates were as follows: For the Three Months Ended September 30, (in millions) 2015 2014 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 24.6 0.0 % $ 27.5 0.0 % United States 10.5 19.6 % 13.5 16.2 % United Kingdom 1.9 -58.5 % 9.2 15.4 % Belgium — (1) 31.4 % (0.1 ) -7.9 % Brazil (0.7 ) 0.0 % (1.2 ) 0.0 % United Arab Emirates 0.1 0.0 % — 0.0 % Ireland — (1) 0.0 % — 0.0 % Malta (0.3 ) 0.0 % (0.8 ) 0.0 % Switzerland 0.1 -20.0 % 0.2 4.8 % Pre-tax income $ 36.2 $ 48.3 For the Nine Months Ended September 30, (in millions) 2015 2014 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 68.8 0.0 % 74.3 0.0 % United States 59.1 22.4 % 49.2 20.9 % United Kingdom 9.1 -21.4 % 11.1 17.1 % Belgium (0.1 ) -50.5 % (0.1 ) -32.4 % Brazil (3.7 ) 0.0 % 3.9 0.0 % United Arab Emirates 0.2 0.0 % (0.9 ) 0.0 % Ireland (0.1 ) 0.0 % — 0.0 % Malta — (1) 0.0 % (1.8 ) 0.0 % Switzerland — (1) -21.3 % — (1) 24.2 % Pre-tax income $ 133.3 $ 135.7 (1) Pre-tax income for the respective year was less than $0.1 million. A reconciliation of the difference between the provision for income taxes and the expected tax provision at the weighted average tax rate is as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Income tax provision at expected rate $ 3.7 $ 6.1 $ 21.1 $ 20.6 Tax effect of: Tax-exempt interest (1.2 ) (1.1 ) (3.1 ) (3.4 ) Dividends received deduction (0.6 ) (0.5 ) (1.8 ) (1.7 ) Valuation allowance change (1.9 ) (1.1 ) (2.9 ) (30.0 ) Other permanent adjustments, net 0.1 (0.1 ) 0.3 (1.0 ) Adjustment for prior year tax return (0.6 ) (1.1 ) (0.6 ) (1.1 ) Adjustment for annualized rate 0.8 0.8 0.6 (0.9 ) United States state tax (benefit) expense — — (2.5 ) — Capital loss carryforward from prior merger — — — 29.8 Other foreign adjustments 0.1 — 0.2 — Prior period adjustments to deferred — 0.8 — (0.3 ) Prior year foreign taxes recovered — — (1.2 ) — Foreign exchange adjustments 0.5 (0.2 ) 0.9 (0.1 ) Foreign withholding taxes — — 0.3 0.3 Income tax provision $ 0.9 $ 3.6 $ 11.3 $ 12.2 Income tax (benefit) provision - Foreign $ (1.2 ) $ 1.5 $ (2.0 ) $ 2.0 Income tax provision - United States, Federal 2.1 2.1 16.8 9.8 Income tax (benefit) provision - United States, state — — (3.8 ) 0.1 Foreign withholding tax - United States — — 0.3 0.3 Income tax provision $ 0.9 $ 3.6 $ 11.3 $ 12.2 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. Our net deferred tax assets (liabilities) are supported by taxes paid in previous periods, reversal of taxable temporary differences and recognition of future 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 sufficient taxable income in the future to recover tax benefits that cannot be recovered from taxes paid in the carryback period, which is generally two years for net operating losses and three years for capital losses for our United States operations. At September 30, 2015, we had a total net deferred tax liability of $10.8 million prior to any valuation allowance. Management has concluded that a valuation allowance is required for a portion of the tax effected net operating loss carryforward of $17.1 million generated from a prior merger and for the tax effected net operating loss carryforward of $1.0 million from ARIS. Of the net operating carryforwards from a prior merger, $15.6 million will expire if not used by December 31, 2025 and $1.5 million will expire if not used by December 31, 2027. Of the ARIS loss carryforward, $0.2 million will expire if not used by December 31, 2027, $0.4 million will expire if not used by December 31, 2028 and $0.4 million will expire if not used by December 31, 2029. The valuation allowances have been established as Internal Revenue Code Section 382 limits the application of net operating loss and net capital loss carryforwards following an ownership change. The loss carryforwards available per year are $2.8 million as required by Internal Revenue Code Section 382. Further, due to cumulative losses since inception, management has concluded that a valuation allowance is required for the full amount of the tax effected net operating losses generated by our Brazil and Malta entities. Accordingly, a valuation allowance of $22.6 million is required as of September 30, 2015 of which $15.1 million relates to the prior merger and ARIS loss carryforwards, $5.5 million relates to Brazil operations, and $2.0 million relates to Malta operations. For the nine months ended September 30, 2015, the valuation allowance was reduced by $0.7 million pertaining to the prior merger and ARIS loss carryforwards, decreased by $2.1 million pertaining to our Brazil operations and decreased by $0.1 million pertaining to our Malta operations. We had no material unrecognized tax benefits as of September 30, 2015 and 2014. Our United States subsidiaries are no longer subject to U.S. federal and state income tax examinations by tax authorities for years before 2011. Our United Kingdom subsidiaries are no longer subject to United Kingdom income tax examinations by Her Majesty’s Revenue and Customs for years before 2012.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	14 . Commitments and Contingencies Argo Group’s subsidiaries are parties to legal actions incidental to their business. Based on the opinion of 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 $71.6 million related to our limited partnership investments at September 30, 2015. These commitments will be funded as required by the partnership agreements and range in duration from one to thirteen years.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Segment Information	15 . Segment Information We are primarily engaged in underwriting property and casualty insurance and reinsurance. We have four ongoing reporting segments: Excess and Surplus Lines, Commercial Specialty, International Specialty and Syndicate 1200. 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. 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 investment function and are not under the control of the individual business segments. Identifiable assets by segment are those assets used in the operation of each segment. Revenue and income (loss) before income taxes for each segment were as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Revenue: Earned premiums Excess and Surplus Lines $ 135.7 $ 121.2 $ 389.9 $ 363.9 Commercial Specialty 73.3 72.7 217.6 215.5 International Specialty 37.6 38.0 113.2 112.6 Syndicate 1200 99.1 104.4 305.5 305.9 Run-off Lines 0.3 1.3 0.4 1.5 Total earned premiums 346.0 337.6 1,026.6 999.4 Net investment income Excess and Surplus Lines 8.8 8.9 26.3 27.2 Commercial Specialty 4.6 4.5 13.8 13.8 International Specialty 2.9 2.3 8.8 6.1 Syndicate 1200 2.3 2.1 6.9 7.9 Run-off Lines 2.1 2.4 6.2 7.2 Corporate and Other 0.6 0.6 1.9 2.5 Total net investment income 21.3 20.8 63.9 64.7 Fee and other income (expense), net 1.0 1.6 (0.1 ) 0.1 Net realized investment and other gains 3.7 12.9 25.0 42.5 Total revenue $ 372.0 $ 372.9 $ 1,115.4 $ 1,106.7 For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Income (loss) before income taxes Excess and Surplus Lines $ 26.5 $ 27.6 $ 75.4 $ 75.9 Commercial Specialty 12.4 8.0 20.8 9.2 International Specialty 3.5 4.0 21.4 16.4 Syndicate 1200 6.9 8.8 28.0 34.7 Run-off Lines (7.1 ) (8.3 ) (7.0 ) (17.6 ) Total segment income before taxes 42.2 40.1 138.6 118.6 Corporate and Other (9.7 ) (4.7 ) (30.3 ) (25.4 ) Net realized investment and other gains 3.7 12.9 25.0 42.5 Total income before income taxes $ 36.2 $ 48.3 $ 133.3 $ 135.7 The table below presents earned premiums by geographic location for the three and nine months ended September 30, 2015 and 2014. For this disclosure, we determine geographic location by the country of domicile of our subsidiaries that underwrite the business and not by the location of insureds or reinsureds from whom the business was generated. For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Bermuda $ 26.8 $ 27.0 $ 76.8 $ 75.7 Brazil 10.3 11.0 34.7 35.4 Malta 0.5 0.5 1.4 1.6 United Kingdom 99.1 104.4 305.5 305.9 United States 209.3 194.7 608.2 580.8 Total earned premiums $ 346.0 $ 337.6 $ 1,026.6 $ 999.4 The following table represents identifiable assets: September 30, December 31, (in millions) 2015 2014 Excess and Surplus Lines $ 2,461.4 $ 2,350.7 Commercial Specialty 1,387.9 1,358.5 International Specialty 801.0 776.8 Syndicate 1200 1,353.1 1,258.5 Run-off Lines 557.7 552.8 Corporate and Other 66.4 59.0 Total $ 6,627.5 $ 6,356.3 Included in total assets at September 30, 2015 and December 31, 2014 are $396.3 million and $315.4 million, respectively, in assets associated with trade capital providers.

Information Provided in Connect

Information Provided in Connection with Outstanding Debt of Subsidiaries	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Information Provided in Connection with Outstanding Debt of Subsidiaries	16 . Information Provided in Connection with Outstanding Debt of Subsidiaries The following tables present condensed consolidating financial information at September 30, 2015 and December 31, 2014 and for the three and nine months ended September 30, 2015 and 2014, for Argo Group (the “Parent Guarantor”) and Argo Group US (the “Subsidiary Issuer”). The Subsidiary Issuer is an indirect wholly-owned subsidiary of the Parent Guarantor. Investments in subsidiaries are accounted for by the Parent Guarantor under the equity method for purposes of the supplemental consolidating presentation. Earnings of subsidiaries are reflected in the Parent Guarantor’s investment accounts and earnings. The Parent Guarantor fully and unconditionally guarantees certain of the debt of the Subsidiary Issuer. Condensed consolidating financial information of the Subsidiary Issuer is presented on a consolidated basis and consists principally of the net assets, results of operations and cash flows of operating insurance company subsidiaries. CONDENSED CONSOLIDATING BALANCE SHEET SEPTEMBER 30, 2015 (in millions) Argo Group International Holdings, Ltd (Parent Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Assets Investments $ 6.4 $ 2,830.2 $ 1,296.4 $ — $ 4,133.0 Cash — 84.8 11.4 — 96.2 Accrued investment income — 15.9 5.1 — 21.0 Premiums receivable — 166.7 270.7 — 437.4 Reinsurance recoverables — 1,195.4 (128.1 ) — 1,067.3 Goodwill and other intangible assets, net — 130.0 96.6 — 226.6 Current income taxes receivable, net — 12.3 4.8 — 17.1 Deferred acquisition costs, net — 61.8 79.6 — 141.4 Ceded unearned premiums — 119.8 142.7 — 262.5 Other assets 9.7 155.3 66.4 (6.4 ) 225.0 Due (to) from affiliates (52.5 ) 1.5 (1.5 ) 52.5 — Intercompany note receivable — 41.7 (41.7 ) — — Investments in subsidiaries 1,722.3 — — (1,722.3 ) — Total assets $ 1,685.9 4,815.4 1,802.4 $ (1,676.2 ) $ 6,627.5 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — 2,177.9 926.2 $ — $ 3,104.1 Unearned premiums — 506.9 425.8 — 932.7 Funds held and ceded reinsurance payable, net — 695.5 (328.6 ) — 366.9 Long-term debt 28.3 288.7 56.9 — 373.9 Deferred tax liabilities, net — 24.0 9.4 — 33.4 Accrued underwriting expenses and other liabilities 16.1 98.4 60.5 — 175.0 Total liabilities 44.4 3,791.4 1,150.2 — 4,986.0 Total shareholders' equity 1,641.5 1,024.0 652.2 (1,676.2 ) 1,641.5 Total liabilities and shareholders' equity $ 1,685.9 $ 4,815.4 $ 1,802.4 $ (1,676.2 ) $ 6,627.5 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING BALANCE SHEET DECEMBER 31, 2014 (in millions) Argo Group International Holdings, Ltd (Parent Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Assets Investments $ 0.7 $ 2,841.5 $ 1,255.7 $ — $ 4,097.9 Cash — 49.3 31.7 — 81.0 Accrued investment income — 17.8 4.3 — 22.1 Premiums receivable — 154.6 199.0 — 353.6 Reinsurance recoverables — 1,173.6 (176.4 ) — 997.2 Goodwill and other intangible assets, net — 131.7 99.1 — 230.8 Current income taxes receivable, net — 10.1 4.8 — 14.9 Deferred acquisition costs, net — 58.0 66.6 — 124.6 Ceded unearned premiums — 98.5 109.1 — 207.6 Other assets 9.6 174.1 67.9 (25.0 ) 226.6 Due from (to) affiliates 2.9 (19.8 ) 19.8 (2.9 ) — Intercompany note receivable — 72.0 (72.0 ) — — Investments in subsidiaries 1,698.0 — — (1,698.0 ) — Total assets $ 1,711.2 $ 4,761.4 $ 1,609.6 $ (1,725.9 ) $ 6,356.3 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — $ 2,136.4 $ 906.0 $ — $ 3,042.4 Unearned premiums — 448.9 368.3 — 817.2 Funds held and ceded reinsurance payable, net — 675.1 (441.3 ) — 233.8 Long-term debt 49.0 288.7 61.4 (20.6 ) 378.5 Deferred tax liabilities, net — 41.2 11.8 — 53.0 Accrued underwriting expenses and other liabilities 15.5 104.2 65.0 — 184.7 Total liabilities 64.5 3,694.5 971.2 (20.6 ) 4,709.6 Total shareholders' equity 1,646.7 1,066.9 638.4 (1,705.3 ) 1,646.7 Total liabilities and shareholders' equity $ 1,711.2 $ 4,761.4 $ 1,609.6 $ (1,725.9 ) $ 6,356.3 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2015 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 122.1 $ 223.9 $ — $ 346.0 Net investment income (0.2 ) 14.1 7.6 (0.2 ) 21.3 Fee and other income (expense), net — — 1.0 — 1.0 Net realized investment and other gains — 1.4 2.3 — 3.7 Total revenue (0.2 ) 137.6 234.8 (0.2 ) 372.0 Expenses: Losses and loss adjustment expenses — 75.4 124.6 — 200.0 Underwriting, acquisition and insurance expenses 4.9 48.0 79.9 — 132.8 Interest expense 0.5 3.8 0.7 (0.2 ) 4.8 Foreign currency exchange gain — 0.1 (1.9 ) — (1.8 ) Total expenses 5.4 127.3 203.3 (0.2 ) 335.8 Income before income taxes (5.6 ) 10.3 31.5 — 36.2 Provision for income taxes — 2.1 (1.2 ) — 0.9 Net income before equity in earnings of subsidiaries (5.6 ) 8.2 32.7 — 35.3 Equity in undistributed earnings of subsidiaries 40.9 — — (40.9 ) — Net income $ 35.3 $ 8.2 $ 32.7 $ (40.9 ) $ 35.3 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2014 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 114.2 $ 223.4 $ — $ 337.6 Net investment income (0.1 ) 13.6 7.3 — 20.8 Fee and other income (expense), net — 1.5 0.1 — 1.6 Net realized investment and other gains — 9.2 3.7 — 12.9 Total revenue (0.1 ) 138.5 234.5 — 372.9 Expenses: Losses and loss adjustment expenses — 69.9 122.0 — 191.9 Underwriting, acquisition and insurance expenses 2.3 51.6 79.9 — 133.8 Interest expense 0.7 3.8 0.6 (0.2 ) 4.9 Foreign currency exchange gain — 0.3 (6.3 ) — (6.0 ) Total expenses 3.0 125.6 196.2 (0.2 ) 324.6 Income before income taxes (3.1 ) 12.9 38.3 0.2 48.3 Provision for income taxes — 2.1 1.5 — 3.6 Net income before equity in earnings of subsidiaries (3.1 ) 10.8 36.8 0.2 44.7 Equity in undistributed earnings of subsidiaries 47.9 — — (47.9 ) — Net income $ 44.8 $ 10.8 $ 36.8 $ (47.7 ) $ 44.7 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2015 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 376.0 $ 650.6 $ — $ 1,026.6 Net investment income (0.7 ) 42.6 22.2 (0.2 ) 63.9 Fee and other income (expense), net — (2.4 ) 2.3 — (0.1 ) Net realized investment and other gains 2.0 24.7 0.3 (2.0 ) 25.0 Total revenue 1.3 440.9 675.4 (2.2 ) 1,115.4 Expenses: Losses and loss adjustment expenses — 220.0 354.3 — 574.3 Underwriting, acquisition and insurance expenses 14.4 149.5 238.0 — 401.9 Interest expense 1.2 11.4 1.9 (0.2 ) 14.3 Foreign currency exchange gain — 1.0 (9.4 ) — (8.4 ) Total expenses 15.6 381.9 584.8 (0.2 ) 982.1 Income before income taxes (14.3 ) 59.0 90.6 (2.0 ) 133.3 Provision for income taxes — 13.3 (2.0 ) — 11.3 Net income before equity in earnings of subsidiaries (14.3 ) 45.7 92.6 (2.0 ) 122.0 Equity in undistributed earnings of subsidiaries 136.3 — — (136.3 ) — Net income $ 122.0 $ 45.7 $ 92.6 $ (138.3 ) $ 122.0 ( 1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2014 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 343.7 $ 655.7 $ — $ 999.4 Net investment income (0.3 ) 42.4 22.6 — 64.7 Fee and other (expense) income, net — (1.5 ) 1.6 — 0.1 Net realized investment and other gains — 34.6 7.9 — 42.5 Total revenue (0.3 ) 419.2 687.8 — 1,106.7 Expenses: Losses and loss adjustment expenses — 211.2 348.3 — 559.5 Underwriting, acquisition and insurance expenses 12.5 147.9 238.9 — 399.3 Interest expense 1.8 11.4 2.1 (0.3 ) 15.0 Foreign currency exchange gain — 0.1 (2.9 ) — (2.8 ) Total expenses 14.3 370.6 586.4 (0.3 ) 971.0 Income before income taxes (14.6 ) 48.6 101.4 0.3 135.7 Provision for income taxes — 10.2 2.0 — 12.2 Net income before equity in earnings of subsidiaries (14.6 ) 38.4 99.4 0.3 123.5 Equity in undistributed earnings of subsidiaries 138.1 — — (138.1 ) — Net income $ 123.5 $ 38.4 $ 99.4 $ (137.8 ) $ 123.5 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2015 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Net cash flows from operating activities $ 16.5 $ 130.6 $ 88.7 $ — $ 235.8 Cash flows from investing activities: Proceeds from sales of investments — 524.5 204.3 — 728.8 Maturities and mandatory calls of fixed maturity investments — 509.5 127.9 — 637.4 Purchases of investments — (1,073.2 ) (395.3 ) — (1,468.5 ) Change in short-term investments and foreign regulatory deposits 1.3 (34.5 ) (29.2 ) — (62.4 ) Settlements of foreign currency exchange forward contracts 1.5 — (8.2 ) — (6.7 ) Issuance of intercompany note, net — 15.0 (15.0 ) — — Purchases of fixed assets and other, net (3.8 ) (7.3 ) 6.5 — (4.6 ) Cash used by investing activities (1.0 ) (66.0 ) (109.0 ) — (176.0 ) Cash flows from financing activities: Borrowings under intercompany note, net — — — — — Activity under stock incentive plans 1.6 — (0.1 ) — 1.5 Repurchase of Company's common shares — (29.7 ) — — (29.7 ) Excess tax expense from share-based payment arrangements — 0.6 — — 0.6 Payment of cash dividend to common shareholders (17.1 ) — — — (17.1 ) Cash used by financing activities (15.5 ) (29.1 ) (0.1 ) — (44.7 ) Effect of exchange rate changes on cash — — 0.1 — 0.1 Change in cash — 35.5 (20.3 ) — 15.2 Cash, beginning of the period — 49.3 31.7 — 81.0 Cash, end of period $ — $ 84.8 $ 11.4 $ — $ 96.2 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2014 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Net cash flows (used by) from operating activities $ (16.5 ) $ 11.8 $ 70.0 $ 6.4 $ 71.7 Cash flows from investing activities: Proceeds from sales of investments — 609.2 366.9 — 976.1 Maturities and mandatory calls of fixed maturity investments — 148.0 95.6 — 243.6 Purchases of investments — (773.1 ) (491.7 ) — (1,264.8 ) Change in short-term investments and foreign regulatory deposits 0.1 (12.5 ) 18.4 — 6.0 Settlements of foreign currency exchange forward contracts (0.5 ) — 1.1 — 0.6 Issuance of intercompany note, net — 14.5 (48.5 ) 34.0 — Purchases of fixed assets and other, net (7.0 ) (20.1 ) (14.7 ) (6.4 ) (48.2 ) Cash (used) provided by investing activities (7.4 ) (34.0 ) (72.9 ) 27.6 (86.7 ) Cash flows from financing activities: Borrowings under intercompany note, net 34.0 — — (34.0 ) — Activity under stock incentive plans 3.3 — — — 3.3 Redemption of trust preferred securities, net — — — (18.0 ) (18.0 ) Payment on note payable — (0.1 ) — — (0.1 ) Repurchase of Company's common shares — (41 ) — — (40.9 ) Excess tax expense from share-based payment arrangements — 0.1 — — 0.1 Payment of cash dividend to common shareholders (13.4 ) — — — (13.4 ) Cash provided (used) by financing activities 23.9 (40.9 ) — (52.0 ) (69.0 ) Effect of exchange rate changes on cash — - (0.3 ) — (0.3 ) Change in cash — (63.1 ) (3.2 ) (18.0 ) (84.3 ) Cash, beginning of period — 132.1 25.3 — 157.4 Cash, end of period $ — $ 69.0 $ 22.1 $ (18.0 ) $ 73.1 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation	1. Basis of Presentation The accompanying consolidated financial statements of Argo Group International Holdings, Ltd. (“Argo Group,” “we” or the “Company”) and its subsidiaries have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and with the instructions for Form 10-Q and Article 10 of Regulation S-X. The preparation of interim financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. The major estimates reflected in our consolidated financial statements include, but are not limited to, reserves for losses and loss adjustment expenses; reinsurance recoverables, including the reinsurance recoverables allowance for doubtful accounts; estimates of written and earned premiums; reinsurance premium receivable; fair value of investments and assessment of potential impairment; valuation of goodwill and intangibles and our deferred tax asset valuation allowance. Actual results could differ from those estimates. Certain financial information that normally is included in annual financial statements, including certain financial statement footnotes, prepared in accordance with GAAP, is not required for interim reporting purposes and has been condensed or omitted. These statements should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2014, filed with the Securities and Exchange Commission on February 27, 2015. The interim financial information as of, and for the three and nine months ended, September 30, 2015 and 2014 is unaudited. However, in the opinion of management, the interim information includes all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results presented for the interim periods. The operating results for the interim periods are not necessarily indicative of the results to be expected for the full year. All significant intercompany amounts have been eliminated in consolidation. Certain amounts in prior years’ financial statements have been reclassified to conform to the current presentation.
10% Stock Dividend	10% Stock Dividend On February 17, 2015, our Board of Directors declared a 10% stock dividend, payable on March 16, 2015, to shareholders of record at the close of business on March 2, 2015. As a result of the stock dividend, 2,554,506 additional shares were issued. Cash was paid in lieu of fractional shares of our common shares. All references to share and per share amounts in this document and related disclosures have been adjusted to reflect the stock dividend for all periods presented.

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2015
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 of investments were as follows: September 30, 2015 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities USD denominated: U.S. Governments $ 167.8 $ 1.4 $ 0.3 $ 168.9 Non-U.S. Governments 87.4 0.4 1.8 86.0 Obligations of states and political subdivisions 473.6 19.4 0.5 492.5 Credit-Financial 491.4 8.2 2.5 497.1 Credit-Industrial 493.0 6.7 6.8 492.9 Credit-Utility 148.8 2.1 7.4 143.5 Structured securities: CMO/MBS-agency (1) 132.8 6.0 0.2 138.6 CMO/MBS-non agency 11.7 0.7 — 12.4 CMBS (2) 165.5 0.9 0.7 165.7 ABS (3) 127.8 0.5 0.3 128.0 CLO (4) 136.0 0.4 0.8 135.6 Foreign denominated: Governments 171.4 1.0 20.1 152.3 Credit 126.0 1.3 18.3 109.0 ABS/CMBS 24.9 0.1 2.9 22.1 CLO 83.6 1.2 7.2 77.6 Total fixed maturities 2,841.7 50.3 69.8 2,822.2 Equity securities 358.5 129.7 22.2 466.0 Other investments 488.1 12.6 0.7 500.0 Short-term investments 345.0 — 0.2 344.8 Total investments $ 4,033.3 $ 192.6 $ 92.9 $ 4,133.0 (1) Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”). (2) Commercial mortgage-backed securities (“CMBS”). (3) Asset-backed securities (“ABS”). (4) December 31, 2014 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities USD denominated: U.S. Governments $ 184.0 $ 1.3 $ 0.3 $ 185.0 Non-U.S. Governments 79.9 0.6 0.6 79.9 Obligations of states and political subdivisions 468.1 22.9 0.3 490.7 Credit-Financial 508.1 12.3 2.3 518.1 Credit-Industrial 493.7 9.4 3.5 499.6 Credit-Utility 142.7 3.2 3.9 142.0 Structured securities: CMO/MBS-agency (1) 168.0 8.0 0.7 175.3 CMO/MBS-non agency 13.2 0.8 — 14.0 CMBS (2) 178.6 1.6 0.2 180.0 ABS (3) 142.7 0.4 0.5 142.6 CLO (4) 78.7 0.2 0.5 78.4 Foreign denominated: Governments 148.4 1.2 9.4 140.2 Credit 136.7 1.8 12.5 126.0 ABS/CMBS 29.5 0.2 2.5 27.2 CLO 44.9 0.7 3.9 41.7 Total fixed maturities 2,817.2 64.6 41.1 2,840.7 Equity securities 307.3 184.1 5.1 486.3 Other investments 488.9 7.5 1.3 495.1 Short-term investments 275.8 — — 275.8 Total investments $ 3,889.2 $ 256.2 $ 47.5 $ 4,097.9 (1) Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”). (2) Commercial mortgage-backed securities (“CMBS”). (3) Asset-backed securities (“ABS”). (4)
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 September 30, 2015, by contractual maturity, were as follows: (in millions) Amortized Cost Fair Value Due in one year or less $ 219.8 $ 208.4 Due after one year through five years 1,295.9 1,285.8 Due after five years through ten years 480.4 481.0 Thereafter 163.3 167.0 Structured securities 682.3 680.0 Total $ 2,841.7 $ 2,822.2
Schedule Of Carrying Value 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 September 30, 2015 and December 31, 2014 were as follows: September 30, 2015 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 141.3 $ — Private equity 143.7 71.6 Long only funds 195.1 — Other investments 19.9 — Total other invested assets $ 500.0 $ 71.6 December 31, 2014 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 153.2 $ — Private equity 123.6 72.9 Long only funds 200.7 — Other investments 17.6 — Total other invested assets $ 495.1 $ 72.9
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, equity securities, other investments and short-term investments is presented below: September 30, 2015 Less Than One Year One Year or Greater Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Fixed maturities USD denominated: U.S. Governments (2) $ 33.6 $ 0.3 $ 0.4 $ — $ 34.0 $ 0.3 Non-U.S. Governments 32.9 1.5 3.1 0.3 36.0 1.8 Obligations of states and political subdivisions 27.2 0.2 8.5 0.3 35.7 0.5 Credit-Financial 197.9 2.2 19.1 0.3 217.0 2.5 Credit-Industrial 218.4 5.2 30.6 1.6 249.0 6.8 Credit-Utility 75.0 3.9 13.3 3.5 88.3 7.4 Structured securities: CMO/MBS-agency (1) 7.9 — 8.2 0.2 16.1 0.2 CMBS (2) 54.9 0.7 4.5 — 59.4 0.7 ABS (1) 27.5 — 12.1 0.3 39.6 0.3 CLO 95.2 0.7 8.9 0.1 104.1 0.8 Foreign denominated: Governments (2) 136.3 20.1 0.3 — 136.6 20.1 Credit 104.2 18.3 — — 104.2 18.3 ABS/CMBS 21.8 2.9 — — 21.8 2.9 CLO 75.6 7.2 — — 75.6 7.2 Total fixed maturities 1,108.4 63.2 109.0 6.6 1,217.4 69.8 Equity securities 136.0 22.2 — — 136.0 22.2 Other investments (0.4 ) 0.7 — — (0.4 ) 0.7 Short-term investments 20.5 0.2 — — 20.5 0.2 Total $ 1,264.5 $ 86.3 $ 109.0 $ 6.6 $ 1,373.5 $ 92.9 (1) Unrealized losses less than one year are less than $0.1 million. (2) Unrealized losses one year or greater are less than $0.1 million. December 31, 2014 Less Than One Year One Year or Greater Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Fixed maturities USD denominated: U.S. Governments $ 55.0 $ 0.2 $ 15.7 $ 0.1 $ 70.7 $ 0.3 Non-U.S. Governments 36.5 0.4 5.2 0.2 41.7 0.6 Obligations of states and political subdivisions 10.4 0.1 16.6 0.2 27.0 0.3 Credit-Financial 195.7 2.2 11.1 0.1 206.8 2.3 Credit-Industrial 240.8 3.3 12.2 0.2 253.0 3.5 Credit-Utility 63.1 3.8 1.9 0.1 65.0 3.9 Structured securities: CMO/MBS-agency 10.1 0.1 19.2 0.6 29.3 0.7 CMBS 49.3 0.1 6.0 0.1 55.3 0.2 ABS 68.8 0.2 8.1 0.3 76.9 0.5 CLO 60.4 0.5 — — 60.4 0.5 Foreign denominated: Governments 123.7 9.3 11.2 0.1 134.9 9.4 Credit 122.3 12.3 0.9 0.2 123.2 12.5 ABS/CMBS 26.8 2.5 — — 26.8 2.5 CLO 41.7 3.9 — — 41.7 3.9 Total fixed maturities 1,104.6 38.9 108.1 2.2 1,212.7 41.1 Equity securities 53.6 5.1 — — 53.6 5.1 Other investments (0.9 ) 1.3 — — (0.9 ) 1.3 Short-term investments — — — — — — Total $ 1,157.3 $ 45.3 $ 108.1 $ 2.2 $ 1,265.4 $ 47.5
Schedule of Company's Gross Realized Investment Gains (Losses)	The following table presents our gross realized investment and other gains (losses): For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Realized gains Fixed maturities $ 2.9 $ 4.5 $ 10.5 $ 15.2 Equity securities 9.8 0.7 22.6 16.1 Other investments 14.6 13.6 44.9 36.5 Short-term investments — — 1.1 0.1 Other assets — 2.0 — 2.0 Gain on sale of real estate holdings — — 0.4 — Gross realized investment gains 27.3 20.8 79.5 69.9 Realized losses Fixed maturities (4.1 ) (1.1 ) (13.1 ) (8.7 ) Equity securities (2.5 ) (0.1 ) (3.6 ) (0.2 ) Other investments (13.4 ) (6.5 ) (30.9 ) (12.6 ) Short-term investments (0.1 ) — (1.5 ) (0.3 ) Other assets (0.1 ) — (0.1 ) (4.0 ) Other-than-temporary impairment losses on fixed maturities — — (0.9 ) (1.2 ) Other-than-temporary impairment losses on equity securities (3.4 ) (0.2 ) (4.4 ) (0.4 ) Gross realized investment and other losses (23.6 ) (7.9 ) (54.5 ) (27.4 ) Net realized investment and other gains $ 3.7 $ 12.9 $ 25.0 $ 42.5
Schedule of Realized Gains (Losses) and Changes in Unrealized Appreciation (Depreciation)	Realized gains (losses) and changes in unrealized appreciation (depreciation) related to fixed maturity and equity security investments are summarized as follows: (in millions) Fixed Maturities Equity Maturities Other Investments Short Term Real Estate Holdings and Other Tax Effects Total Three Months Ended September 30, 2015 Realized before impairments $ (1.2 ) $ 7.3 $ 1.2 $ (0.1 ) $ (0.1 ) $ (2.1 ) $ 5.0 Realized - impairments — (3.4 ) — — — 1.2 (2.2 ) Change in unrealized (22.6 ) (46.7 ) — (0.2 ) — 20.1 (49.4 ) Three Months Ended September 30, 2014 Realized before impairments $ 3.4 $ 0.6 $ 7.1 $ — $ 2.0 $ (5.3 ) $ 7.8 Realized - impairments — (0.2 ) — — — 0.4 0.2 Change in unrealized (33.9 ) (10.7 ) — — — 9.0 (35.6 ) Nine Months Ended September 30, 2015 Realized before impairments $ (2.6 ) $ 19.0 $ 14.0 $ (0.4 ) $ 0.3 $ (10.5 ) $ 19.8 Realized - impairments (0.9 ) (4.4 ) — — — 1.8 (3.5 ) Change in unrealized (40.9 ) (71.5 ) 1.5 (0.2 ) — 33.3 (77.8 ) Nine Months Ended September 30, 2014 Realized before impairments $ 6.5 $ 15.9 $ 23.9 $ (0.2 ) $ (2.0 ) $ (13.4 ) $ 30.7 Realized - impairments (1.2 ) (0.4 ) — — — 0.5 (1.1 ) Change in unrealized (12.0 ) 5.0 1.1 — — (3.5 ) (9.4 )
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) September 30, 2015 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities USD denominated: U.S. Governments $ 168.9 $ 110.4 $ 58.5 $ — Non-U.S. Governments 86.0 — 86.0 — Obligations of states and political subdivisions 492.5 — 492.5 — Credit-Financial 497.1 — 497.1 — Credit-Industrial 492.9 — 492.9 — Credit-Utility 143.5 — 143.5 — Structured securities: CMO/MBS-agency 138.6 — 138.6 — CMO/MBS-non agency 12.4 — 12.4 — CMBS 165.7 — 165.7 — ABS 128.0 — 128.0 — CLO 135.6 — 135.6 — Foreign denominated: Governments 152.3 — 152.3 — Credit 109.0 — 109.0 — ABS/CMBS 22.1 — 22.1 — CLO 77.6 — 77.6 — Total fixed maturities 2,822.2 110.4 2,711.8 — Equity securities 466.0 465.2 — 0.8 Other investments 91.2 — 91.2 — Short-term investments 344.8 323.8 21.0 — $ 3,724.2 $ 899.4 $ 2,824.0 $ 0.8 (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, 2014 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities USD denominated: U.S. Governments $ 185.0 $ 99.2 $ 85.8 $ — Non-U.S. Governments 79.9 — 79.9 — Obligations of states and political subdivisions 490.7 — 490.7 — Credit-Financial 518.1 — 518.1 — Credit-Industrial 499.6 — 499.6 — Credit-Utility 142.0 — 142.0 — Structured securities: CMO/MBS-agency 175.3 — 175.3 — CMO/MBS-non agency 14.0 — 14.0 — CMBS 180.0 — 180.0 — ABS 142.6 — 142.6 — CLO 78.4 — 78.4 — Foreign denominated: Governments 140.2 — 140.2 — Credit 126.0 — 126.0 — ABS/CMBS 27.2 — 27.2 — CLO 41.7 — 41.7 — Total fixed maturities 2,840.7 99.2 2,741.5 — Equity securities 486.3 485.4 — 0.9 Other investments 97.3 — 97.3 — Short-term investments 275.8 273.9 1.9 — $ 3,700.1 $ 858.5 $ 2,840.7 $ 0.9 (a) Quoted prices in active markets for identical assets (b) Significant other observable inputs (c) Significant unobservable inputs
Schedule of Reconciliation of Beginning and Ending Balances for Investments Categorized as Level 3	A reconciliation of the beginning and ending balances for the investments categorized as Level 3 are as follows: Fair Value Measurements Using Observable Inputs (Level 3) (in millions) Equity Securities Total Beginning balance, January 1, 2015 $ 0.9 $ 0.9 Transfers into Level 3 — — Transfers out of Level 3 — — Total gains or losses (realized/unrealized): Included in net income (loss) — — Included in other comprehensive income (loss) — — Purchases, issuances, sales, and settlements Purchases — — Issuances — — Sales (0.1 ) (0.1 ) Settlements — — Ending balance, September 30, 2015 $ 0.8 $ 0.8 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 September 30, 2015 $ — $ — (in millions) Equity Securities Other Assets Total Beginning balance, January 1, 2014 $ 1.3 $ 2.6 $ 3.9 Transfers into Level 3 — — — Transfers out of Level 3 — — — Total gains or losses (realized/unrealized): Included in net income (loss) — — — Included in other comprehensive income (loss) 0.1 — 0.1 Purchases, issuances, sales, and settlements Purchases — — — Issuances — — — Sales (0.5 ) — (0.5 ) Settlements — (2.6 ) (2.6 ) Ending balance, December 31, 2014 $ 0.9 $ — $ 0.9 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 December 31, 2014 $ — $ — $ —

Reserves for Losses and Loss 25

Reserves for Losses and Loss Adjustment Expenses (Tables)	9 Months Ended
	Sep. 30, 2015
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 Nine Months Ended September 30, (in millions) 2015 2014 Net reserves beginning of the year $ 2,137.1 $ 2,107.6 Add: Losses and LAE incurred during current calendar year, net of reinsurance: Current accident year 589.6 585.9 Prior accident years (15.3 ) (26.4 ) Losses and LAE incurred during calendar year, net of reinsurance 574.3 559.5 Deduct: Losses and LAE payments made during current calendar year, net of reinsurance: Current accident year 105.2 115.3 Prior accident years 435.5 435.5 Losses and LAE payments made during current calendar year, net of reinsurance: 540.7 550.8 Change in participation interest (1) (1.2 ) 24.7 Foreign exchange adjustments (27.7 ) (4.9 ) Net reserves - end of period 2,141.8 2,136.1 Add: Reinsurance recoverables on unpaid losses and LAE, end of period 962.3 926.5 Gross reserves - end of period $ 3,104.1 $ 3,062.6

Disclosures about Fair Value 26

Disclosures about Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2015
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: September 30, 2015 December 31, 2014 (in millions) Carrying Amount Fair Value Carrying Amount Fair Value Junior subordinated debentures $ 172.7 $ 153.0 $ 172.7 $ 155.5 Senior unsecured fixed rate notes 143.8 144.6 143.8 132.3 Other indebtedness: Floating rate loan stock 56.8 50.3 61.3 55.2 Note payable 0.6 0.6 0.7 0.6 $ 373.9 $ 348.5 $ 378.5 $ 343.6

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Schedule of Repurchase of Shares	A summary of common shares repurchased for the nine months ended September 30, 2015 is shown below: Repurchase Type Date Trading Plan Initiated 2015 Purchase Period Number of Shares Repurchased Average Price of Shares Repurchased Total Cost (in millions) Repurchase Authorization Year 10b5-1 Trading Plan 12/15/2014 01/05/2015-02/12/2015 117,482 $ 53.50 $ 6.3 2013 10b5-1 Trading Plan 03/16/2015 03/18/2015-05/06/2015 150,050 $ 49.56 7.4 2013 Open Market N/A 01/01/2015-09/30/2015 307,523 $ 51.83 16.0 2013 Total 575,055 $ 51.58 $ 29.7

Accumulated Other Comprehensi28

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2015
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 nine months ended September 30, 2015 and 2014 is presented below: (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance, January 1, 2015 $ (15.6 ) $ 130.7 $ (7.0 ) $ 108.1 Other comprehensive loss before reclassifications (6.6 ) (75.7 ) — (82.3 ) Amounts reclassified from accumulated other comprehensive loss — (2.3 ) — (2.3 ) Net current-period other comprehensive loss (6.6 ) (78.0 ) — (84.6 ) Balance at September 30, 2015 $ (22.2 ) $ 52.7 $ (7.0 ) $ 23.5 (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance, January 1, 2014 $ (11.5 ) $ 163.9 $ (4.6 ) $ 147.8 Other comprehensive income before reclassifications (1.9 ) 5.4 — 3.5 Amounts reclassified from accumulated other comprehensive income — (14.8 ) — (14.8 ) Net current-period other comprehensive income (1.9 ) (9.4 ) — (11.3 ) Balance at September 30, 2014 $ (13.4 ) $ 154.5 $ (4.6 ) $ 136.5
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	The following tables illustrate the amounts reclassified from accumulated other comprehensive (loss) income shown in the above tables that have been included in our Consolidated Statements of Income: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Unrealized gains and losses on securities: Net realized investment losses $ 0.1 $ (5.8 ) $ (6.9 ) $ (22.0 ) Benefit for income taxes 1.7 4.1 4.6 7.2 Net of taxes $ 1.8 $ (1.7 ) $ (2.3 ) $ (14.8 )

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Net Income Per Common Share on Basic and Diluted Basis	The following table presents the calculation of net income per common share on a basic and diluted basis (all balances have been adjusted to reflect the 10% stock dividend): For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions, except number of shares and per share amounts) 2015 2014 2015 2014 Net income $ 35.3 $ 44.7 $ 122.0 $ 123.5 Weighted average common shares outstanding - basic 27,916,586 28,552,240 27,997,638 28,824,182 Effect of dilutive securities: Equity compensation awards 557,918 528,368 542,456 512,993 Weighted average common shares outstanding - diluted 28,474,504 29,080,608 28,540,094 29,337,175 Net income per common share: Basic $ 1.27 $ 1.57 $ 4.36 $ 4.28 Diluted $ 1.24 $ 1.54 $ 4.28 $ 4.21

Supplemental Cash Flow Inform30

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2015
Supplemental Cash Flow Elements [Abstract]
Schedule of Interest Paid	Interest paid was as follows: For the Nine Months Ended September 30, (in millions) 2015 2014 Senior unsecured fixed rate notes $ 7.0 $ 7.0 Junior subordinated debentures 5.3 5.8 Other indebtedness 2.0 2.3 Total interest paid $ 14.3 $ 15.1

Share-based Compensation (Table

Share-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Fair Value Assumptions	The following table summarizes the assumptions we used for the nine months ended September 30, 2015 and 2014: For the Nine Months Ended September 30, 2015 2014 Risk-free rate of return 1.44% 1.77% Expected dividend yields 1.52% 1.49% Expected award life (years) 4.64 4.67 Expected volatility 20.81% 22.84%
Summary of Restricted Share Activity	A summary of restricted share activity as of September 30, 2015 and changes during the nine months then ended is as follows: Shares Weighted-Average Grant Date Fair Value Outstanding at January 1, 2015 313,716 $ 31.38 Granted 297,873 $ 39.21 Vested and issued (119,295 ) $ 26.83 Expired or forfeited (8,938 ) $ 41.76 Outstanding at September 30, 2015 483,356 $ 37.14
Summary of Stock-Settled SARs Activity	A summary of stock-settled SARs activity as of September 30, 2015 and changes during the nine months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2015 1,313,726 $ 28.57 Granted 243,305 $ 39.43 Exercised (165,036 ) $ 24.15 Expired or forfeited (7,231 ) $ 31.68 Outstanding at September 30, 2015 1,384,764 $ 30.14
Summary of Cash-Settled SARs Activity	A summary of cash-settled SARs activity as of September 30, 2015 and changes during the nine months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2015 2,001,451 $ 32.76 Granted 913,157 $ 47.48 Exercised (366,527 ) $ 29.19 Expired or forfeited (216,354 ) $ 39.40 Outstanding at September 30, 2015 2,331,727 $ 38.46

Underwriting, Acquisition and32

Underwriting, Acquisition and Insurance Expenses (Tables)	9 Months Ended
	Sep. 30, 2015
Underwriting Acquisition And Insurance Expenses [Abstract]
Underwriting, Acquisition and Insurance Expenses	Underwriting, acquisition and insurance expenses were as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Commissions $ 56.5 $ 59.8 $ 182.4 $ 178.0 General expenses 69.6 69.0 222.2 211.9 Premium taxes, boards and bureaus 7.5 7.2 8.1 19.5 133.6 136.0 412.7 409.4 Net deferral of policy acquisition costs (0.8 ) (2.2 ) (10.8 ) (10.1 ) Total underwriting, acquisition and insurance expenses $ 132.8 $ 133.8 $ 401.9 $ 399.3

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Tax Provision (Benefit)	Our income tax provision includes the following components: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Current tax provision $ (11.3 ) $ (15.0 ) $ (2.5 ) $ (10.7 ) Deferred tax (benefit) provision related to: Future tax deductions 14.1 19.7 16.7 52.9 Valuation allowance change (1.9 ) (1.1 ) (2.9 ) (30.0 ) Income tax provision $ 0.9 $ 3.6 $ 11.3 $ 12.2
Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates	For the three and nine months ended September 30, 2015 and 2014, pre-tax income (loss) attributable to our operations and the operations’ effective tax rates were as follows: For the Three Months Ended September 30, (in millions) 2015 2014 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 24.6 0.0 % $ 27.5 0.0 % United States 10.5 19.6 % 13.5 16.2 % United Kingdom 1.9 -58.5 % 9.2 15.4 % Belgium — (1) 31.4 % (0.1 ) -7.9 % Brazil (0.7 ) 0.0 % (1.2 ) 0.0 % United Arab Emirates 0.1 0.0 % — 0.0 % Ireland — (1) 0.0 % — 0.0 % Malta (0.3 ) 0.0 % (0.8 ) 0.0 % Switzerland 0.1 -20.0 % 0.2 4.8 % Pre-tax income $ 36.2 $ 48.3 For the Nine Months Ended September 30, (in millions) 2015 2014 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 68.8 0.0 % 74.3 0.0 % United States 59.1 22.4 % 49.2 20.9 % United Kingdom 9.1 -21.4 % 11.1 17.1 % Belgium (0.1 ) -50.5 % (0.1 ) -32.4 % Brazil (3.7 ) 0.0 % 3.9 0.0 % United Arab Emirates 0.2 0.0 % (0.9 ) 0.0 % Ireland (0.1 ) 0.0 % — 0.0 % Malta — (1) 0.0 % (1.8 ) 0.0 % Switzerland — (1) -21.3 % — (1) 24.2 % Pre-tax income $ 133.3 $ 135.7 (1) Pre-tax income for the respective year was less than $0.1 million.
Reconciliation of Difference Between Provision for Income Taxes and Expected Tax Provision at Weighted Average Tax Rate	A reconciliation of the difference between the provision for income taxes and the expected tax provision at the weighted average tax rate is as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Income tax provision at expected rate $ 3.7 $ 6.1 $ 21.1 $ 20.6 Tax effect of: Tax-exempt interest (1.2 ) (1.1 ) (3.1 ) (3.4 ) Dividends received deduction (0.6 ) (0.5 ) (1.8 ) (1.7 ) Valuation allowance change (1.9 ) (1.1 ) (2.9 ) (30.0 ) Other permanent adjustments, net 0.1 (0.1 ) 0.3 (1.0 ) Adjustment for prior year tax return (0.6 ) (1.1 ) (0.6 ) (1.1 ) Adjustment for annualized rate 0.8 0.8 0.6 (0.9 ) United States state tax (benefit) expense — — (2.5 ) — Capital loss carryforward from prior merger — — — 29.8 Other foreign adjustments 0.1 — 0.2 — Prior period adjustments to deferred — 0.8 — (0.3 ) Prior year foreign taxes recovered — — (1.2 ) — Foreign exchange adjustments 0.5 (0.2 ) 0.9 (0.1 ) Foreign withholding taxes — — 0.3 0.3 Income tax provision $ 0.9 $ 3.6 $ 11.3 $ 12.2 Income tax (benefit) provision - Foreign $ (1.2 ) $ 1.5 $ (2.0 ) $ 2.0 Income tax provision - United States, Federal 2.1 2.1 16.8 9.8 Income tax (benefit) provision - United States, state — — (3.8 ) 0.1 Foreign withholding tax - United States — — 0.3 0.3 Income tax provision $ 0.9 $ 3.6 $ 11.3 $ 12.2

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Revenue and Income (Loss) Before Income Taxes for Each Segment	Revenue and income (loss) before income taxes for each segment were as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Revenue: Earned premiums Excess and Surplus Lines $ 135.7 $ 121.2 $ 389.9 $ 363.9 Commercial Specialty 73.3 72.7 217.6 215.5 International Specialty 37.6 38.0 113.2 112.6 Syndicate 1200 99.1 104.4 305.5 305.9 Run-off Lines 0.3 1.3 0.4 1.5 Total earned premiums 346.0 337.6 1,026.6 999.4 Net investment income Excess and Surplus Lines 8.8 8.9 26.3 27.2 Commercial Specialty 4.6 4.5 13.8 13.8 International Specialty 2.9 2.3 8.8 6.1 Syndicate 1200 2.3 2.1 6.9 7.9 Run-off Lines 2.1 2.4 6.2 7.2 Corporate and Other 0.6 0.6 1.9 2.5 Total net investment income 21.3 20.8 63.9 64.7 Fee and other income (expense), net 1.0 1.6 (0.1 ) 0.1 Net realized investment and other gains 3.7 12.9 25.0 42.5 Total revenue $ 372.0 $ 372.9 $ 1,115.4 $ 1,106.7 For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Income (loss) before income taxes Excess and Surplus Lines $ 26.5 $ 27.6 $ 75.4 $ 75.9 Commercial Specialty 12.4 8.0 20.8 9.2 International Specialty 3.5 4.0 21.4 16.4 Syndicate 1200 6.9 8.8 28.0 34.7 Run-off Lines (7.1 ) (8.3 ) (7.0 ) (17.6 ) Total segment income before taxes 42.2 40.1 138.6 118.6 Corporate and Other (9.7 ) (4.7 ) (30.3 ) (25.4 ) Net realized investment and other gains 3.7 12.9 25.0 42.5 Total income before income taxes $ 36.2 $ 48.3 $ 133.3 $ 135.7
Schedule of Earned Premiums by Geographic Location	The table below presents earned premiums by geographic location for the three and nine months ended September 30, 2015 and 2014. For this disclosure, we determine geographic location by the country of domicile of our subsidiaries that underwrite the business and not by the location of insureds or reinsureds from whom the business was generated. For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2015 2014 2015 2014 Bermuda $ 26.8 $ 27.0 $ 76.8 $ 75.7 Brazil 10.3 11.0 34.7 35.4 Malta 0.5 0.5 1.4 1.6 United Kingdom 99.1 104.4 305.5 305.9 United States 209.3 194.7 608.2 580.8 Total earned premiums $ 346.0 $ 337.6 $ 1,026.6 $ 999.4
Identifiable Assets	The following table represents identifiable assets: September 30, December 31, (in millions) 2015 2014 Excess and Surplus Lines $ 2,461.4 $ 2,350.7 Commercial Specialty 1,387.9 1,358.5 International Specialty 801.0 776.8 Syndicate 1200 1,353.1 1,258.5 Run-off Lines 557.7 552.8 Corporate and Other 66.4 59.0 Total $ 6,627.5 $ 6,356.3

Information Provided in Conne35

Information Provided in Connection with Outstanding Debt of Subsidiaries (Tables)	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Condensed Consolidating Balance Sheet	CONDENSED CONSOLIDATING BALANCE SHEET SEPTEMBER 30, 2015 (in millions) Argo Group International Holdings, Ltd (Parent Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Assets Investments $ 6.4 $ 2,830.2 $ 1,296.4 $ — $ 4,133.0 Cash — 84.8 11.4 — 96.2 Accrued investment income — 15.9 5.1 — 21.0 Premiums receivable — 166.7 270.7 — 437.4 Reinsurance recoverables — 1,195.4 (128.1 ) — 1,067.3 Goodwill and other intangible assets, net — 130.0 96.6 — 226.6 Current income taxes receivable, net — 12.3 4.8 — 17.1 Deferred acquisition costs, net — 61.8 79.6 — 141.4 Ceded unearned premiums — 119.8 142.7 — 262.5 Other assets 9.7 155.3 66.4 (6.4 ) 225.0 Due (to) from affiliates (52.5 ) 1.5 (1.5 ) 52.5 — Intercompany note receivable — 41.7 (41.7 ) — — Investments in subsidiaries 1,722.3 — — (1,722.3 ) — Total assets $ 1,685.9 4,815.4 1,802.4 $ (1,676.2 ) $ 6,627.5 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — 2,177.9 926.2 $ — $ 3,104.1 Unearned premiums — 506.9 425.8 — 932.7 Funds held and ceded reinsurance payable, net — 695.5 (328.6 ) — 366.9 Long-term debt 28.3 288.7 56.9 — 373.9 Deferred tax liabilities, net — 24.0 9.4 — 33.4 Accrued underwriting expenses and other liabilities 16.1 98.4 60.5 — 175.0 Total liabilities 44.4 3,791.4 1,150.2 — 4,986.0 Total shareholders' equity 1,641.5 1,024.0 652.2 (1,676.2 ) 1,641.5 Total liabilities and shareholders' equity $ 1,685.9 $ 4,815.4 $ 1,802.4 $ (1,676.2 ) $ 6,627.5 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING BALANCE SHEET DECEMBER 31, 2014 (in millions) Argo Group International Holdings, Ltd (Parent Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Assets Investments $ 0.7 $ 2,841.5 $ 1,255.7 $ — $ 4,097.9 Cash — 49.3 31.7 — 81.0 Accrued investment income — 17.8 4.3 — 22.1 Premiums receivable — 154.6 199.0 — 353.6 Reinsurance recoverables — 1,173.6 (176.4 ) — 997.2 Goodwill and other intangible assets, net — 131.7 99.1 — 230.8 Current income taxes receivable, net — 10.1 4.8 — 14.9 Deferred acquisition costs, net — 58.0 66.6 — 124.6 Ceded unearned premiums — 98.5 109.1 — 207.6 Other assets 9.6 174.1 67.9 (25.0 ) 226.6 Due from (to) affiliates 2.9 (19.8 ) 19.8 (2.9 ) — Intercompany note receivable — 72.0 (72.0 ) — — Investments in subsidiaries 1,698.0 — — (1,698.0 ) — Total assets $ 1,711.2 $ 4,761.4 $ 1,609.6 $ (1,725.9 ) $ 6,356.3 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — $ 2,136.4 $ 906.0 $ — $ 3,042.4 Unearned premiums — 448.9 368.3 — 817.2 Funds held and ceded reinsurance payable, net — 675.1 (441.3 ) — 233.8 Long-term debt 49.0 288.7 61.4 (20.6 ) 378.5 Deferred tax liabilities, net — 41.2 11.8 — 53.0 Accrued underwriting expenses and other liabilities 15.5 104.2 65.0 — 184.7 Total liabilities 64.5 3,694.5 971.2 (20.6 ) 4,709.6 Total shareholders' equity 1,646.7 1,066.9 638.4 (1,705.3 ) 1,646.7 Total liabilities and shareholders' equity $ 1,711.2 $ 4,761.4 $ 1,609.6 $ (1,725.9 ) $ 6,356.3 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations.
Condensed Consolidating Statement of Income	CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2015 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 122.1 $ 223.9 $ — $ 346.0 Net investment income (0.2 ) 14.1 7.6 (0.2 ) 21.3 Fee and other income (expense), net — — 1.0 — 1.0 Net realized investment and other gains — 1.4 2.3 — 3.7 Total revenue (0.2 ) 137.6 234.8 (0.2 ) 372.0 Expenses: Losses and loss adjustment expenses — 75.4 124.6 — 200.0 Underwriting, acquisition and insurance expenses 4.9 48.0 79.9 — 132.8 Interest expense 0.5 3.8 0.7 (0.2 ) 4.8 Foreign currency exchange gain — 0.1 (1.9 ) — (1.8 ) Total expenses 5.4 127.3 203.3 (0.2 ) 335.8 Income before income taxes (5.6 ) 10.3 31.5 — 36.2 Provision for income taxes — 2.1 (1.2 ) — 0.9 Net income before equity in earnings of subsidiaries (5.6 ) 8.2 32.7 — 35.3 Equity in undistributed earnings of subsidiaries 40.9 — — (40.9 ) — Net income $ 35.3 $ 8.2 $ 32.7 $ (40.9 ) $ 35.3 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2014 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 114.2 $ 223.4 $ — $ 337.6 Net investment income (0.1 ) 13.6 7.3 — 20.8 Fee and other income (expense), net — 1.5 0.1 — 1.6 Net realized investment and other gains — 9.2 3.7 — 12.9 Total revenue (0.1 ) 138.5 234.5 — 372.9 Expenses: Losses and loss adjustment expenses — 69.9 122.0 — 191.9 Underwriting, acquisition and insurance expenses 2.3 51.6 79.9 — 133.8 Interest expense 0.7 3.8 0.6 (0.2 ) 4.9 Foreign currency exchange gain — 0.3 (6.3 ) — (6.0 ) Total expenses 3.0 125.6 196.2 (0.2 ) 324.6 Income before income taxes (3.1 ) 12.9 38.3 0.2 48.3 Provision for income taxes — 2.1 1.5 — 3.6 Net income before equity in earnings of subsidiaries (3.1 ) 10.8 36.8 0.2 44.7 Equity in undistributed earnings of subsidiaries 47.9 — — (47.9 ) — Net income $ 44.8 $ 10.8 $ 36.8 $ (47.7 ) $ 44.7 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2015 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 376.0 $ 650.6 $ — $ 1,026.6 Net investment income (0.7 ) 42.6 22.2 (0.2 ) 63.9 Fee and other income (expense), net — (2.4 ) 2.3 — (0.1 ) Net realized investment and other gains 2.0 24.7 0.3 (2.0 ) 25.0 Total revenue 1.3 440.9 675.4 (2.2 ) 1,115.4 Expenses: Losses and loss adjustment expenses — 220.0 354.3 — 574.3 Underwriting, acquisition and insurance expenses 14.4 149.5 238.0 — 401.9 Interest expense 1.2 11.4 1.9 (0.2 ) 14.3 Foreign currency exchange gain — 1.0 (9.4 ) — (8.4 ) Total expenses 15.6 381.9 584.8 (0.2 ) 982.1 Income before income taxes (14.3 ) 59.0 90.6 (2.0 ) 133.3 Provision for income taxes — 13.3 (2.0 ) — 11.3 Net income before equity in earnings of subsidiaries (14.3 ) 45.7 92.6 (2.0 ) 122.0 Equity in undistributed earnings of subsidiaries 136.3 — — (136.3 ) — Net income $ 122.0 $ 45.7 $ 92.6 $ (138.3 ) $ 122.0 ( 1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2014 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 343.7 $ 655.7 $ — $ 999.4 Net investment income (0.3 ) 42.4 22.6 — 64.7 Fee and other (expense) income, net — (1.5 ) 1.6 — 0.1 Net realized investment and other gains — 34.6 7.9 — 42.5 Total revenue (0.3 ) 419.2 687.8 — 1,106.7 Expenses: Losses and loss adjustment expenses — 211.2 348.3 — 559.5 Underwriting, acquisition and insurance expenses 12.5 147.9 238.9 — 399.3 Interest expense 1.8 11.4 2.1 (0.3 ) 15.0 Foreign currency exchange gain — 0.1 (2.9 ) — (2.8 ) Total expenses 14.3 370.6 586.4 (0.3 ) 971.0 Income before income taxes (14.6 ) 48.6 101.4 0.3 135.7 Provision for income taxes — 10.2 2.0 — 12.2 Net income before equity in earnings of subsidiaries (14.6 ) 38.4 99.4 0.3 123.5 Equity in undistributed earnings of subsidiaries 138.1 — — (138.1 ) — Net income $ 123.5 $ 38.4 $ 99.4 $ (137.8 ) $ 123.5 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations.
Condensed Consolidating Statement of Cash Flows	CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2015 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Net cash flows from operating activities $ 16.5 $ 130.6 $ 88.7 $ — $ 235.8 Cash flows from investing activities: Proceeds from sales of investments — 524.5 204.3 — 728.8 Maturities and mandatory calls of fixed maturity investments — 509.5 127.9 — 637.4 Purchases of investments — (1,073.2 ) (395.3 ) — (1,468.5 ) Change in short-term investments and foreign regulatory deposits 1.3 (34.5 ) (29.2 ) — (62.4 ) Settlements of foreign currency exchange forward contracts 1.5 — (8.2 ) — (6.7 ) Issuance of intercompany note, net — 15.0 (15.0 ) — — Purchases of fixed assets and other, net (3.8 ) (7.3 ) 6.5 — (4.6 ) Cash used by investing activities (1.0 ) (66.0 ) (109.0 ) — (176.0 ) Cash flows from financing activities: Borrowings under intercompany note, net — — — — — Activity under stock incentive plans 1.6 — (0.1 ) — 1.5 Repurchase of Company's common shares — (29.7 ) — — (29.7 ) Excess tax expense from share-based payment arrangements — 0.6 — — 0.6 Payment of cash dividend to common shareholders (17.1 ) — — — (17.1 ) Cash used by financing activities (15.5 ) (29.1 ) (0.1 ) — (44.7 ) Effect of exchange rate changes on cash — — 0.1 — 0.1 Change in cash — 35.5 (20.3 ) — 15.2 Cash, beginning of the period — 49.3 31.7 — 81.0 Cash, end of period $ — $ 84.8 $ 11.4 $ — $ 96.2 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2014 (in millions) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Net cash flows (used by) from operating activities $ (16.5 ) $ 11.8 $ 70.0 $ 6.4 $ 71.7 Cash flows from investing activities: Proceeds from sales of investments — 609.2 366.9 — 976.1 Maturities and mandatory calls of fixed maturity investments — 148.0 95.6 — 243.6 Purchases of investments — (773.1 ) (491.7 ) — (1,264.8 ) Change in short-term investments and foreign regulatory deposits 0.1 (12.5 ) 18.4 — 6.0 Settlements of foreign currency exchange forward contracts (0.5 ) — 1.1 — 0.6 Issuance of intercompany note, net — 14.5 (48.5 ) 34.0 — Purchases of fixed assets and other, net (7.0 ) (20.1 ) (14.7 ) (6.4 ) (48.2 ) Cash (used) provided by investing activities (7.4 ) (34.0 ) (72.9 ) 27.6 (86.7 ) Cash flows from financing activities: Borrowings under intercompany note, net 34.0 — — (34.0 ) — Activity under stock incentive plans 3.3 — — — 3.3 Redemption of trust preferred securities, net — — — (18.0 ) (18.0 ) Payment on note payable — (0.1 ) — — (0.1 ) Repurchase of Company's common shares — (41 ) — — (40.9 ) Excess tax expense from share-based payment arrangements — 0.1 — — 0.1 Payment of cash dividend to common shareholders (13.4 ) — — — (13.4 ) Cash provided (used) by financing activities 23.9 (40.9 ) — (52.0 ) (69.0 ) Effect of exchange rate changes on cash — - (0.3 ) — (0.3 ) Change in cash — (63.1 ) (3.2 ) (18.0 ) (84.3 ) Cash, beginning of period — 132.1 25.3 — 157.4 Cash, end of period $ — $ 69.0 $ 22.1 $ (18.0 ) $ 73.1 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations.

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Detail) - shares	Sep. 15, 2015	Feb. 17, 2015	Sep. 15, 2014	Sep. 30, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Stock dividend declared		10.00%		10.00%
Additional stock issued as dividend		2,554,506
Dividends declaration date		Feb. 17, 2015
Dividends payable date		Mar. 16, 2015
Dividend payable, date of record	Sep. 1, 2015	Mar. 2, 2015	Sep. 1, 2014

Investments - Schedule of Amort

Investments - Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value of Investments (Detail) - USD ($) $ in Millions		Sep. 30, 2015		Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		$ 4,033.3		$ 3,889.2
Gross Unrealized Gains		192.6		256.2
Gross Unrealized Losses		92.9		47.5
Fair Value		4,133		4,097.9
Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		2,841.7		2,817.2
Gross Unrealized Gains		50.3		64.6
Gross Unrealized Losses		69.8		41.1
Fair Value		2,822.2		2,840.7
Fixed Maturities [Member] | CLO [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	[1]	136		78.7
Gross Unrealized Gains	[1]	0.4		0.2
Gross Unrealized Losses	[1]	0.8		0.5
Fair Value	[1]	135.6		78.4
Fixed Maturities [Member] | U.S. Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		167.8		184
Gross Unrealized Gains		1.4		1.3
Gross Unrealized Losses		0.3	[2]	0.3
Fair Value		168.9		185
Fixed Maturities [Member] | Non-U.S. Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		87.4		79.9
Gross Unrealized Gains		0.4		0.6
Gross Unrealized Losses		1.8		0.6
Fair Value		86		79.9
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		473.6		468.1
Gross Unrealized Gains		19.4		22.9
Gross Unrealized Losses		0.5		0.3
Fair Value		492.5		490.7
Fixed Maturities [Member] | Credit-Financial [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		491.4		508.1
Gross Unrealized Gains		8.2		12.3
Gross Unrealized Losses		2.5		2.3
Fair Value		497.1		518.1
Fixed Maturities [Member] | Credit-Industrial [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		493		493.7
Gross Unrealized Gains		6.7		9.4
Gross Unrealized Losses		6.8		3.5
Fair Value		492.9		499.6
Fixed Maturities [Member] | Credit-Utility [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		148.8		142.7
Gross Unrealized Gains		2.1		3.2
Gross Unrealized Losses		7.4		3.9
Fair Value		143.5		142
Fixed Maturities [Member] | CMO/MBS-Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	[3]	132.8		168
Gross Unrealized Gains	[3]	6		8
Gross Unrealized Losses	[3]	0.2	[4]	0.7
Fair Value	[3]	138.6		175.3
Fixed Maturities [Member] | CMO/MBS-Non Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		11.7		13.2
Gross Unrealized Gains		0.7		0.8
Gross Unrealized Losses		0		0
Fair Value		12.4		14
Fixed Maturities [Member] | CMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	[5]	165.5		178.6
Gross Unrealized Gains	[5]	0.9		1.6
Gross Unrealized Losses	[5]	0.7	[2]	0.2
Fair Value	[5]	165.7		180
Fixed Maturities [Member] | ABS [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	[6]	127.8		142.7
Gross Unrealized Gains	[6]	0.5		0.4
Gross Unrealized Losses	[6]	0.3		0.5
Fair Value	[6]	128		142.6
Fixed Maturities [Member] | Foreign Denominated: Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		171.4		148.4
Gross Unrealized Gains		1		1.2
Gross Unrealized Losses		20.1	[2]	9.4
Fair Value		152.3		140.2
Fixed Maturities [Member] | Foreign Denominated: Credit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		126		136.7
Gross Unrealized Gains		1.3		1.8
Gross Unrealized Losses		18.3		12.5
Fair Value		109		126
Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		24.9		29.5
Gross Unrealized Gains		0.1		0.2
Gross Unrealized Losses		2.9		2.5
Fair Value		22.1		27.2
Fixed Maturities [Member] | Foreign denominated: CLO [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		83.6		44.9
Gross Unrealized Gains		1.2		0.7
Gross Unrealized Losses		7.2		3.9
Fair Value		77.6		41.7
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		358.5		307.3
Gross Unrealized Gains		129.7		184.1
Gross Unrealized Losses		22.2		5.1
Fair Value		466		486.3
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		488.1		488.9
Gross Unrealized Gains		12.6		7.5
Gross Unrealized Losses		0.7		1.3
Fair Value		500		495.1
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		345		275.8
Gross Unrealized Gains		0		0
Gross Unrealized Losses		0.2	[4]	0
Fair Value		$ 344.8		$ 275.8
[1]	Collateralized loan obligations (“CLO”).
[2]	Unrealized losses one year or greater are less than $0.1 million.
[3]	Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”).
[4]	Unrealized losses less than one year are less than $0.1 million.
[5]	Commercial mortgage-backed securities (“CMBS”).
[6]	Asset-backed securities (“ABS”).

Investments - Additional Inform

Investments - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2015USD ($)Security	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)Security	Sep. 30, 2014USD ($)	Sep. 30, 2015CADSecurity	Dec. 31, 2014USD ($)	Sep. 30, 2014CAD
Schedule Of Investments [Line Items]
Fair value of investments, assets managed on behalf of the trade capital providers	$ 78,200,000		$ 78,200,000			$ 75,200,000
Number of securities in an unrealized loss position, total | Security	6,805		6,805		6,805
Number of securities in an unrealized loss position for less than one year | Security	2,909		2,909		2,909
Number of securities in an unrealized loss position for a period of one year or greater | Security	193		193		193
Fair value of the currency forward contracts		$ 2,000,000		$ 2,000,000
Realized gains from currency forward contracts	$ 0	100,000	$ 500,000	3,900,000
Realized losses from currency forward contracts	300,000	2,200,000	2,300,000	4,100,000
Amortized Cost	4,033,300,000		4,033,300,000			3,889,200,000
Fair Value	4,133,000,000		4,133,000,000			4,097,900,000
Reported loss expense reserve	28,200,000		28,200,000			43,600,000
Securities pledged to Lloyd's	211,900,000		211,900,000			217,900,000
Transfers between Level 1 and Level 2 securities	0		0
Transfers between Level 2 and Level 1 securities	0		0
Securities Pledged as Collateral [Member]
Schedule Of Investments [Line Items]
Pledged assets separately reported, securities pledged under letters of credit facilities, at amortized cost	34,600,000		34,600,000			55,000,000
Pledged assets separately reported, securities pledged under letters of credit facilities, at fair value	34,800,000		34,800,000			55,300,000
Currency Forward Contracts [Member]
Schedule Of Investments [Line Items]
Notional amount of the currency forward contracts		25,600,000		25,600,000
Currency Forward Contracts [Member] | C A D
Schedule Of Investments [Line Items]
Notional amount of the currency forward contracts	119,900,000	118,300,000	119,900,000	118,300,000	CAD 160,700,000		CAD 132,000,000
Realized gains from currency forward contracts	8,600,000	5,700,000	26,400,000	5,700,000
Realized losses from currency forward contracts	3,900,000	2,600,000	13,400,000	2,600,000
Gain (loss) from fair value of the currency forward contracts			5,100,000	(400,000)
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Other-than-temporary losses	0	0	900,000	1,200,000
Amortized Cost	2,841,700,000		2,841,700,000			2,817,200,000
Fair Value	2,822,200,000		2,822,200,000			2,840,700,000
Equity Securities [Member]
Schedule Of Investments [Line Items]
Other-than-temporary losses	3,400,000	$ 200,000	4,400,000	$ 400,000
Amortized Cost	358,500,000		358,500,000			307,300,000
Fair Value	466,000,000		466,000,000			486,300,000
Deposit with Various U.S. Canadian Insurance and Other Agencies [Member] | United States [Member]
Schedule Of Investments [Line Items]
Amortized Cost	185,900,000		185,900,000
Fair Value	$ 192,300,000		$ 192,300,000
Deposit with Various U.S. Insurance and Other Agencies [Member] | United States [Member]
Schedule Of Investments [Line Items]
Amortized Cost						186,600,000
Fair Value						$ 194,200,000

Investments - Schedule of Amo39

Investments - Schedule of Amortized Cost and Fair Values of Fixed Maturity Investments, by Contractual Maturity (Detail) $ in Millions	Sep. 30, 2015USD ($)
Investments Debt And Equity Securities [Abstract]
Amortized Cost, Due in one year or less	$ 219.8
Amortized Cost, Due after one year through five years	1,295.9
Amortized Cost, Due after five years through ten years	480.4
Amortized Cost, Thereafter	163.3
Amortized Cost, Structured securities	682.3
Amortized Cost, Total	2,841.7
Fair Value, Due in one year or less	208.4
Fair Value, Due after one year through five years	1,285.8
Fair Value, Due after five years through ten years	481
Fair Value, Thereafter	167
Fair Value, Structured securities	680
Fair Value, Total	$ 2,822.2

Investments - Schedule of Carry

Investments - Schedule of Carrying Value and Unfunded Investment Commitments of Other Invested Assets Portfolio (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Investments [Line Items]
Carrying Value	$ 4,133	$ 4,097.9	[1]
Hedge funds [Member]
Schedule Of Investments [Line Items]
Carrying Value	141.3	153.2
Unfunded Commitments	0	0
Private equity [Member]
Schedule Of Investments [Line Items]
Carrying Value	143.7	123.6
Unfunded Commitments	71.6	72.9
Long only funds [Member]
Schedule Of Investments [Line Items]
Carrying Value	195.1	200.7
Unfunded Commitments	0	0
Other Investments [Member]
Schedule Of Investments [Line Items]
Carrying Value	19.9	17.6
Unfunded Commitments	0	0
Other invested assets [Member]
Schedule Of Investments [Line Items]
Carrying Value	500	495.1
Unfunded Commitments	$ 71.6	$ 72.9
[1]	Derived from audited consolidated financial statements.

Investments - Schedule of Aging

Investments - Schedule of Aging of Unrealized Losses on Company's Investments in Fixed Maturities, Equity Securities and Other Investments (Detail) - USD ($) $ in Millions		Sep. 30, 2015		Dec. 31, 2014
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		$ 1,264.5		$ 1,157.3
Unrealized Losses, Less Than One Year		86.3		45.3
Fair Value, One Year or Greater		109		108.1
Unrealized Losses, One Year or Greater		6.6		2.2
Fair Value, Total		1,373.5		1,265.4
Unrealized Losses, Total		92.9		47.5
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		1,108.4		1,104.6
Unrealized Losses, Less Than One Year		63.2		38.9
Fair Value, One Year or Greater		109		108.1
Unrealized Losses, One Year or Greater		6.6		2.2
Fair Value, Total		1,217.4		1,212.7
Unrealized Losses, Total		69.8		41.1
Fixed Maturities [Member] | CLO [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		95.2		60.4
Unrealized Losses, Less Than One Year		0.7		0.5
Fair Value, One Year or Greater		8.9		0
Unrealized Losses, One Year or Greater		0.1		0
Fair Value, Total		104.1		60.4
Unrealized Losses, Total	[1]	0.8		0.5
Fixed Maturities [Member] | U.S. Governments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		33.6	[2]	55
Unrealized Losses, Less Than One Year		0.3	[2]	0.2
Fair Value, One Year or Greater		0.4	[2]	15.7
Unrealized Losses, One Year or Greater		0	[2]	0.1
Fair Value, Total		34	[2]	70.7
Unrealized Losses, Total		0.3	[2]	0.3
Fixed Maturities [Member] | Non-U.S. Governments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		32.9		36.5
Unrealized Losses, Less Than One Year		1.5		0.4
Fair Value, One Year or Greater		3.1		5.2
Unrealized Losses, One Year or Greater		0.3		0.2
Fair Value, Total		36		41.7
Unrealized Losses, Total		1.8		0.6
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		27.2		10.4
Unrealized Losses, Less Than One Year		0.2		0.1
Fair Value, One Year or Greater		8.5		16.6
Unrealized Losses, One Year or Greater		0.3		0.2
Fair Value, Total		35.7		27
Unrealized Losses, Total		0.5		0.3
Fixed Maturities [Member] | Credit-Financial [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		197.9		195.7
Unrealized Losses, Less Than One Year		2.2		2.2
Fair Value, One Year or Greater		19.1		11.1
Unrealized Losses, One Year or Greater		0.3		0.1
Fair Value, Total		217		206.8
Unrealized Losses, Total		2.5		2.3
Fixed Maturities [Member] | Credit-Industrial [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		218.4		240.8
Unrealized Losses, Less Than One Year		5.2		3.3
Fair Value, One Year or Greater		30.6		12.2
Unrealized Losses, One Year or Greater		1.6		0.2
Fair Value, Total		249		253
Unrealized Losses, Total		6.8		3.5
Fixed Maturities [Member] | Credit-Utility [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		75		63.1
Unrealized Losses, Less Than One Year		3.9		3.8
Fair Value, One Year or Greater		13.3		1.9
Unrealized Losses, One Year or Greater		3.5		0.1
Fair Value, Total		88.3		65
Unrealized Losses, Total		7.4		3.9
Fixed Maturities [Member] | CMO/MBS-Agency [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		7.9	[3]	10.1
Unrealized Losses, Less Than One Year		0	[3]	0.1
Fair Value, One Year or Greater		8.2	[3]	19.2
Unrealized Losses, One Year or Greater		0.2	[3]	0.6
Fair Value, Total		16.1	[3]	29.3
Unrealized Losses, Total	[4]	0.2	[3]	0.7
Fixed Maturities [Member] | CMBS [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		54.9	[2]	49.3
Unrealized Losses, Less Than One Year		0.7	[2]	0.1
Fair Value, One Year or Greater		4.5	[2]	6
Unrealized Losses, One Year or Greater		0	[2]	0.1
Fair Value, Total		59.4	[2]	55.3
Unrealized Losses, Total	[5]	0.7	[2]	0.2
Fixed Maturities [Member] | ABS [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		27.5		68.8
Unrealized Losses, Less Than One Year		0		0.2
Fair Value, One Year or Greater		12.1		8.1
Unrealized Losses, One Year or Greater		0.3		0.3
Fair Value, Total		39.6		76.9
Unrealized Losses, Total	[6]	0.3		0.5
Fixed Maturities [Member] | Foreign Denominated: Governments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		136.3	[2]	123.7
Unrealized Losses, Less Than One Year		20.1	[2]	9.3
Fair Value, One Year or Greater		0.3	[2]	11.2
Unrealized Losses, One Year or Greater		0	[2]	0.1
Fair Value, Total		136.6	[2]	134.9
Unrealized Losses, Total		20.1	[2]	9.4
Fixed Maturities [Member] | Foreign Denominated: Credit [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		104.2		122.3
Unrealized Losses, Less Than One Year		18.3		12.3
Fair Value, One Year or Greater		0		0.9
Unrealized Losses, One Year or Greater		0		0.2
Fair Value, Total		104.2		123.2
Unrealized Losses, Total		18.3		12.5
Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		21.8		26.8
Unrealized Losses, Less Than One Year		2.9		2.5
Fair Value, One Year or Greater		0		0
Unrealized Losses, One Year or Greater		0		0
Fair Value, Total		21.8		26.8
Unrealized Losses, Total		2.9		2.5
Fixed Maturities [Member] | Foreign denominated: CLO [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		75.6		41.7
Unrealized Losses, Less Than One Year		7.2		3.9
Fair Value, One Year or Greater		0		0
Unrealized Losses, One Year or Greater		0		0
Fair Value, Total		75.6		41.7
Unrealized Losses, Total		7.2		3.9
Equity Securities [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		136		53.6
Unrealized Losses, Less Than One Year		22.2		5.1
Fair Value, One Year or Greater		0		0
Unrealized Losses, One Year or Greater		0		0
Fair Value, Total		136		53.6
Unrealized Losses, Total		22.2		5.1
Other Investments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		(0.4)		(0.9)
Unrealized Losses, Less Than One Year		0.7		1.3
Fair Value, One Year or Greater		0		0
Unrealized Losses, One Year or Greater		0		0
Fair Value, Total		(0.4)		(0.9)
Unrealized Losses, Total		0.7		1.3
Short-Term Investments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		20.5	[3]	0
Unrealized Losses, Less Than One Year		0.2	[3]	0
Fair Value, One Year or Greater		0	[3]	0
Unrealized Losses, One Year or Greater		0	[3]	0
Fair Value, Total		20.5	[3]	0
Unrealized Losses, Total		$ 0.2	[3]	$ 0
[1]	Collateralized loan obligations (“CLO”).
[2]	Unrealized losses one year or greater are less than $0.1 million.
[3]	Unrealized losses less than one year are less than $0.1 million.
[4]	Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”).
[5]	Commercial mortgage-backed securities (“CMBS”).
[6]	Asset-backed securities (“ABS”).

Investments - Schedule of Agi42

Investments - Schedule of Aging of Unrealized Losses on Company's Investments in Fixed Maturities, Equity Securities and Other Investments (Parenthetical) (Detail) $ in Millions	Sep. 30, 2015USD ($)
Investments Debt And Equity Securities [Abstract]
Unrealized losses less than one year	$ 0.1
Unrealized losses one year or greater	$ 0.1

Investments - Schedule of Compa

Investments - Schedule of Company's Gross Realized Investment Gains (Losses) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule Of Investments [Line Items]
Gross realized investment gains and other	$ 27.3	$ 20.8	$ 79.5	$ 69.9
Gross realized investment and other losses	(23.6)	(7.9)	(54.5)	(27.4)
Net realized investment and other gains	3.7	12.9	25	42.5
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	2.9	4.5	10.5	15.2
Gross realized investment and other losses	(4.1)	(1.1)	(13.1)	(8.7)
Equity Securities [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	9.8	0.7	22.6	16.1
Gross realized investment and other losses	(2.5)	(0.1)	(3.6)	(0.2)
Other Investments [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	14.6	13.6	44.9	36.5
Gross realized investment and other losses	(13.4)	(6.5)	(30.9)	(12.6)
Short-Term Investments [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	0	0	1.1	0.1
Gross realized investment and other losses	(0.1)	0	(1.5)	(0.3)
Other Assets [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	0	2	0	2
Gross realized investment and other losses	(0.1)	0	(0.1)	(4)
Real Estate Holdings [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	0	0	0.4	0
Other-Than-Temporary Impairment Losses on Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other losses	0	0	(0.9)	(1.2)
Other-Than-Temporary Impairment Losses on Equity Securities [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other losses	$ (3.4)	$ (0.2)	$ (4.4)	$ (0.4)

Investments - Schedule of Reali

Investments - Schedule of Realized Gains (Losses) and Changes in Unrealized of Appreciation(Depreciation) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule Of Investments [Line Items]
Realized before impairments	$ 5	$ 7.8	$ 19.8	$ 30.7
Realized - impairments	(2.2)	0.2	(3.5)	(1.1)
Change in unrealized	(49.4)	(35.6)	(77.8)	(9.4)
Realized before impairments, Tax Effects	(2.1)	(5.3)	(10.5)	(13.4)
Realized - impairments, Tax Effects	1.2	0.4	1.8	0.5
Change in unrealized, Tax Effects	20.1	9	33.3	(3.5)
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Realized before impairments	(1.2)	3.4	(2.6)	6.5
Realized - impairments	0	0	(0.9)	(1.2)
Change in unrealized	(22.6)	(33.9)	(40.9)	(12)
Equity Securities [Member]
Schedule Of Investments [Line Items]
Realized before impairments	7.3	0.6	19	15.9
Realized - impairments	(3.4)	(0.2)	(4.4)	(0.4)
Change in unrealized	(46.7)	(10.7)	(71.5)	5
Other Investments [Member]
Schedule Of Investments [Line Items]
Realized before impairments	1.2	7.1	14	23.9
Realized - impairments	0	0	0	0
Change in unrealized	0	0	1.5	1.1
Short-Term Investments [Member]
Schedule Of Investments [Line Items]
Realized before impairments	(0.1)	0	(0.4)	(0.2)
Realized - impairments	0	0	0	0
Change in unrealized	(0.2)	0	(0.2)	0
Real Estate Holdings and Other [Member]
Schedule Of Investments [Line Items]
Realized before impairments	(0.1)	2	0.3	(2)
Realized - impairments	0	0	0	0
Change in unrealized	$ 0	$ 0	$ 0	$ 0

Investments - Financial Assets

Investments - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		$ 4,133	$ 4,097.9
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		3,724.2	3,700.1
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	899.4	858.5
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	2,824	2,840.7
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0.8	0.9
Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		2,822.2	2,840.7
Fixed Maturities [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[4]	135.6	78.4
Fixed Maturities [Member] | U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		168.9	185
Fixed Maturities [Member] | Non-U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		86	79.9
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		492.5	490.7
Fixed Maturities [Member] | Credit-Financial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		497.1	518.1
Fixed Maturities [Member] | Credit-Industrial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		492.9	499.6
Fixed Maturities [Member] | Credit-Utility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		143.5	142
Fixed Maturities [Member] | CMO/MBS-Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[5]	138.6	175.3
Fixed Maturities [Member] | CMO/MBS-Non Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		12.4	14
Fixed Maturities [Member] | CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[6]	165.7	180
Fixed Maturities [Member] | ABS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[7]	128	142.6
Fixed Maturities [Member] | Foreign Denominated: Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		152.3	140.2
Fixed Maturities [Member] | Foreign Denominated: Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		109	126
Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		22.1	27.2
Fixed Maturities [Member] | Foreign denominated: CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		77.6	41.7
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		2,822.2	2,840.7
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		135.6	78.4
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		168.9	185
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Non-U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		86	79.9
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		492.5	490.7
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Credit-Financial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		497.1	518.1
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Credit-Industrial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		492.9	499.6
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Credit-Utility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		143.5	142
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | CMO/MBS-Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		138.6	175.3
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | CMO/MBS-Non Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		12.4	14
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		165.7	180
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | ABS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		128	142.6
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Denominated: Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		152.3	140.2
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Denominated: Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		109	126
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Foreign denominated: ABS/CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		22.1	27.2
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Foreign denominated: CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		77.6	41.7
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	110.4	99.2
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	110.4	99.2
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Non-U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Credit-Financial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Credit-Industrial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Credit-Utility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | CMO/MBS-Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | CMO/MBS-Non Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | ABS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign Denominated: Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign Denominated: Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign denominated: ABS/CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign denominated: CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	2,711.8	2,741.5
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	135.6	78.4
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	58.5	85.8
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Non-U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	86	79.9
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	492.5	490.7
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Credit-Financial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	497.1	518.1
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Credit-Industrial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	492.9	499.6
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Credit-Utility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	143.5	142
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | CMO/MBS-Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	138.6	175.3
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | CMO/MBS-Non Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	12.4	14
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	165.7	180
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | ABS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	128	142.6
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign Denominated: Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	152.3	140.2
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign Denominated: Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	109	126
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign denominated: ABS/CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	22.1	27.2
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign denominated: CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	77.6	41.7
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Non-U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Credit-Financial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Credit-Industrial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Credit-Utility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | CMO/MBS-Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | CMO/MBS-Non Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | ABS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Foreign Denominated: Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Foreign Denominated: Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Foreign denominated: ABS/CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Fixed Maturities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Foreign denominated: CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		466	486.3
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		466	486.3
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	465.2	485.4
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	0	0
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0.8	0.9
Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		500	495.1
Other Investments [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		91.2	97.3
Other Investments [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	0	0
Other Investments [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	91.2	97.3
Other Investments [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	0	0
Short-Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		344.8	275.8
Short-Term Investments [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value		344.8	275.8
Short-Term Investments [Member] | Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[1]	323.8	273.9
Short-Term Investments [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[2]	21	1.9
Short-Term Investments [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	[3]	$ 0	$ 0
[1]	Quoted prices in active markets for identical assets
[2]	Significant other observable inputs
[3]	Significant unobservable inputs
[4]	Collateralized loan obligations (“CLO”).
[5]	Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”).
[6]	Commercial mortgage-backed securities (“CMBS”).
[7]	Asset-backed securities (“ABS”).

Investments - Schedule of Recon

Investments - Schedule of Reconciliation of Beginning and Ending Balances for Investments Categorized as Level 3 (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 0.9	$ 3.9
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income (loss)	0	0
Included in other comprehensive income (loss)	0	0.1
Purchases	0	0
Issuances	0	0
Sales	(0.1)	(0.5)
Settlements	0	(2.6)
Ending balance	0.8	0.9
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 [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	0.9	1.3
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income (loss)	0	0
Included in other comprehensive income (loss)	0	0.1
Purchases	0	0
Issuances	0	0
Sales	(0.1)	(0.5)
Settlements	0	0
Ending balance	0.8	0.9
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
Other Assets [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 0	2.6
Transfers into Level 3		0
Transfers out of Level 3		0
Included in net income (loss)		0
Included in other comprehensive income (loss)		0
Purchases		0
Issuances		0
Sales		0
Settlements		(2.6)
Ending balance		0
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

Reserves for Losses and Loss 47

Reserves for Losses and Loss Adjustment Expenses - Reinsurance Recoverables (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014		Sep. 30, 2014
Liability for Claims and Claims Adjustment Expense [Abstract]
Net reserves beginning of the year		$ 2,137.1	$ 2,107.6
Losses and LAE incurred during current calendar year, net of reinsurance:
Current accident year		589.6	585.9
Prior accident years		(15.3)	(26.4)
Losses and LAE incurred during calendar year, net of reinsurance		574.3	559.5
Current accident year		105.2	115.3
Prior accident years		435.5	435.5
Losses and LAE payments made during current calendar year, net of reinsurance:		540.7	550.8
Change in participation interest	[1]	(1.2)	24.7
Foreign exchange adjustments		(27.7)	(4.9)
Net reserves - end of period		2,141.8	2,136.1
Reinsurance recoverables on unpaid losses and LAE, end of period				$ (962.3)			$ (926.5)
Reserves for losses and loss adjustment expenses				3,104.1	$ 3,042.4	[2]	3,062.6
Net reserves - end of period		$ 2,137.1	$ 2,107.6	$ 2,141.8	$ 2,137.1		$ 2,136.1
[1]	Amount represents (decreases) increases in reserves due to change in syndicate participation
[2]	Derived from audited consolidated financial statements.

Reserves for Losses and Loss 48

Reserves for Losses and Loss Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	$ 15.3	$ 26.4
Excess and Surplus Lines [Member]
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	25.1	34.6
Commercial Specialty [Member]
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	10.4	5.2
International Specialty [Member]
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	5.8
International Specialty [Member] | Brazil [Member]
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years		0.1
Syndicate 1200 Segment [Member]
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	2.8	15.8
Run Off Lines [Member]
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	$ 8	$ 18.9

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	Jul. 16, 2014	Sep. 30, 2015	Dec. 31, 2014		Mar. 07, 2014
Debt Instrument [Line Items]
Junior subordinated debentures		$ 172,700,000	$ 172,700,000	[1]
Junior subordinated debentures, Redemption Date	Apr. 29, 2015
Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Junior subordinated debentures	$ 20,000,000
Percentage of debt securities redeemed as compare to principal amount	90.00%
Redemption received on debt securities	$ 18,200,000
Recognition of pre-tax gain	$ 2,000,000
Credit Agreement [Member] | Revolving Credit Facility | J P Morgan Chase Bank
Debt Instrument [Line Items]
Letter of credit facility amount					$ 175,000,000
Revolving credit facility maturity date		Mar. 7, 2018
Credit Agreement [Member] | Letter Of Credit | J P Morgan Chase Bank
Debt Instrument [Line Items]
Letter of credit facility amount		$ 17,500,000
Letter of credit facility amount		$ 0	$ 200,000
[1]	Derived from audited consolidated financial statements.

Disclosures about Fair Value 50

Disclosures about Fair Value of Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Financial Instruments Owned and Pledged as Collateral [Line Items]
Premiums receivable	$ 437.4	$ 353.6	[1]
Reinsurance recoverables	1,067.3	997.2	[1]
Premiums receivable, allowance for doubtful accounts	3.7	5.2
Over 90 Days [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Premiums receivable	12.2	12.4
Reinsurance recoverables	9.1	9.9
Reinsurance recoverables, allowance for doubtful accounts	2.4	1.8
Premiums receivables, secured by collateral	0.3	0.3
Reinsurance recoverables, secured by collateral	$ 0.6	$ 0.4
[1]	Derived from audited consolidated financial statements.

Disclosures about Fair Value 51

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	Sep. 30, 2015	Dec. 31, 2014
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	$ 373.9	$ 378.5
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	348.5	343.6
Junior Subordinated Debentures [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	172.7	172.7
Junior Subordinated Debentures [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	153	155.5
Senior Unsecured Fixed Rate Notes [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	143.8	143.8
Senior Unsecured Fixed Rate Notes [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	144.6	132.3
Other Indebtedness [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	56.8	61.3
Other Indebtedness [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	50.3	55.2
Other Indebtedness [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	0.6	0.7
Other Indebtedness [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	$ 0.6	$ 0.6

Shareholders Equity - Additiona

Shareholders Equity - Additional Information (Detail) - USD ($)	Sep. 15, 2015	Aug. 04, 2015	Feb. 17, 2015	Sep. 15, 2014	Aug. 05, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Nov. 05, 2013
Class Of Stock [Line Items]
Stock dividend declared			10.00%			10.00%		10.00%
Dividends declaration date			Feb. 17, 2015
Additional stock issued as dividend			2,554,506
Dividends payable date			Mar. 16, 2015
Dividend payable, date of record	Sep. 1, 2015		Mar. 2, 2015	Sep. 1, 2014
Dividend declared per common share		$ 0.20			$ 0.16	$ 0.20	$ 0.16	$ 0.60	$ 0.46
Cash dividends paid - common shares, total	$ 5,600,000			$ 4,700,000
Common shares repurchased on open market								575,055
2013 Repurchase Authorization [Member]
Class Of Stock [Line Items]
Total number of shares authorized for purchase, Value						$ 63,100,000		$ 63,100,000		$ 150,000,000
Common shares repurchased on open market						85,959		575,055
Common shares repurchased on open market, total cost						$ 4,800,000		$ 29,700,000

Shareholders Equity - Schedule

Shareholders Equity - Schedule of Repurchase of Shares (Detail) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)$ / sharesshares
Equity Class Of Treasury Stock [Line Items]
Common shares repurchased on open market | shares	575,055
Average Price of Shares Repurchased	$ 51.58
Total Cost (in millions) | $	$ 29.7
10b5-1 Trading Plan Initiated In 2014 [Member]
Equity Class Of Treasury Stock [Line Items]
Date Trading Plan Initiated	Dec. 15, 2014
Trading Plan Purchase Period Start Date	01/05/2015
Common shares repurchased on open market | shares	117,482
Average Price of Shares Repurchased	$ 53.50
Total Cost (in millions) | $	$ 6.3
Repurchase Authorization Year	2,013
Trading Plan Purchase Period End Date	02/12/2015
10b5-1 Trading Plan Initiated In 2015 [Member]
Equity Class Of Treasury Stock [Line Items]
Date Trading Plan Initiated	Mar. 16, 2015
Trading Plan Purchase Period Start Date	03/18/2015
Common shares repurchased on open market | shares	150,050
Average Price of Shares Repurchased	$ 49.56
Total Cost (in millions) | $	$ 7.4
Repurchase Authorization Year	2,013
Trading Plan Purchase Period End Date	05/06/2015
Open Market [Member]
Equity Class Of Treasury Stock [Line Items]
Trading Plan Purchase Period Start Date	01/01/2015
Common shares repurchased on open market | shares	307,523
Average Price of Shares Repurchased	$ 51.83
Total Cost (in millions) | $	$ 16
Repurchase Authorization Year	2,013
Trading Plan Purchase Period End Date	09/30/2015

Accumulated Other Comprehensi54

Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			$ 108.1	[1]	$ 147.8
Other comprehensive (loss) income before reclassifications			(82.3)		3.5
Amounts reclassified from accumulated other comprehensive loss			(2.3)		(14.8)
Other comprehensive (loss) income, net of tax	$ (53.6)	$ (37.9)	(84.6)		(11.3)
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	23.5	136.5	23.5		136.5
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			(15.6)		(11.5)
Other comprehensive (loss) income before reclassifications			(6.6)		(1.9)
Amounts reclassified from accumulated other comprehensive loss			0		0
Other comprehensive (loss) income, net of tax			(6.6)		(1.9)
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	(22.2)	(13.4)	(22.2)		(13.4)
Unrealized Holding Gains on Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			130.7		163.9
Other comprehensive (loss) income before reclassifications			(75.7)		5.4
Amounts reclassified from accumulated other comprehensive loss			(2.3)		(14.8)
Other comprehensive (loss) income, net of tax			(78)		(9.4)
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	52.7	154.5	52.7		154.5
Defined Benefit Pension Plans
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			(7)		(4.6)
Other comprehensive (loss) income before reclassifications			0		0
Amounts reclassified from accumulated other comprehensive loss			0		0
Other comprehensive (loss) income, net of tax			0		0
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	$ (7)	$ (4.6)	$ (7)		$ (4.6)
[1]	Derived from audited consolidated financial statements.

Accumulated Other Comprehensi55

Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Unrealized gains and losses on securities:
Net realized investment losses	$ 0.1	$ (5.8)	$ (6.9)	$ (22)
Benefit for income taxes	1.7	4.1	4.6	7.2
Net of taxes			(2.3)	(14.8)
Unrealized Holding Gains on Securities
Unrealized gains and losses on securities:
Net of taxes			(2.3)	(14.8)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Holding Gains on Securities
Unrealized gains and losses on securities:
Net realized investment losses	0.1	(5.8)	(6.9)	(22)
Benefit for income taxes	1.7	4.1	4.6	7.2
Net of taxes	$ 1.8	$ (1.7)	$ (2.3)	$ (14.8)

Net Income Per Common Share - A

Net Income Per Common Share - Additional Information (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Feb. 17, 2015	Dec. 31, 2014	[1]
Earnings Per Share [Abstract]
Stock dividend declared	10.00%		10.00%		10.00%
Treasury shares, shares	9,181,544	8,440,355	9,181,544	8,440,355		8,606,489
Antidilutive securities excluded from computation of diluted net income per share, shares	0	1,879	0	1,879
[1]	Derived from audited consolidated financial statements.

Net Income Per Common Share - N

Net Income Per Common Share - Net Income Per Common Share on Basic and Diluted Basis (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 35.3	$ 44.7	$ 122	$ 123.5
Weighted average common shares outstanding - basic	27,916,586	28,552,240	27,997,638	28,824,182
Effect of dilutive securities:
Equity compensation awards	557,918	528,368	542,456	512,993
Weighted average common shares outstanding - diluted	28,474,504	29,080,608	28,540,094	29,337,175
Net income per common share - basic	$ 1.27	$ 1.57	$ 4.36	$ 4.28
Net income per common share - diluted	$ 1.24	$ 1.54	$ 4.28	$ 4.21

Supplemental Cash Flow Inform58

Supplemental Cash Flow Information - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Income Taxes Paid Net [Abstract]
Income taxes paid	$ 10,800,000	$ 23,800,000
Income taxes recovered	$ 11,500,000	$ 0

Supplemental Cash Flow Inform59

Supplemental Cash Flow Information - Schedule of Interest Paid (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Supplemental Cash Flow [Line Items]
Total interest paid	$ 14.3	$ 15.1
Senior Unsecured Fixed Rate Notes [Member]
Supplemental Cash Flow [Line Items]
Total interest paid	7	7
Junior Subordinated Debentures [Member]
Supplemental Cash Flow [Line Items]
Total interest paid	5.3	5.8
Other Indebtedness [Member]
Supplemental Cash Flow [Line Items]
Total interest paid	$ 2	$ 2.3

Share-based Compensation - Addi

Share-based Compensation - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Feb. 17, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based compensation arrangement by share-based payment award, award vesting period, years	5 years	5 years
Stock dividend declared	10.00%		10.00%
Percentage increase in number of awards outstanding due to stock dividend	10.00%
Reduction in exercise price of awards outstanding due to stock dividend	9.09%

Share-based Compensation - Fair

Share-based Compensation - Fair Value Assumptions (Detail)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free rate of return	1.44%	1.77%
Expected dividend yields	1.52%	1.49%
Expected award life (years)	4 years 7 months 21 days	4 years 8 months 1 day
Expected volatility	20.81%	22.84%

Share-Based Compensation - 2014

Share-Based Compensation - 2014 Long-Term Incentive Plan - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	May. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Nov. 30, 2007
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	5 years
Restricted Share [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, compensation expense		$ 1.4	$ 0.8	$ 4.4	$ 2.2
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		13.9		$ 13.9
Restricted Share [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period, years				2 years
Restricted Share [Member] | Maximum [Member]
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
Stock-Settled SARs Activity [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, compensation expense		0.3	0.3	$ 1.3	1.6
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		3.3		$ 3.3
Stock-Settled SARs Activity [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period, years				1 year
Stock-Settled SARs Activity [Member] | Maximum [Member]
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
Cash-Settled SARs Activity [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, compensation expense		2.8	$ 1.2	$ 14.1	$ 9.2
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		$ 13.2		$ 13.2
Cash-Settled SARs Activity [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period, years				1 year
Cash-Settled SARs Activity [Member] | Maximum [Member]
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
2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized						4,500,000
Share-based compensation arrangement by share-based payment award, number of shares available for grant	1,460,000
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, additional number of shares authorized	2,800,000
Count of restricted shares, settle in common shares				2.75

Share-based Compensation - Summ

Share-based Compensation - Summary of Restricted Share Activity (Detail) - Restricted Stock Units (RSUs) [Member]	9 Months Ended
	Sep. 30, 2015$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2015 | shares	313,716
Granted, Shares | shares	297,873
Vested and issued, Shares | shares	(119,295)
Expired or forfeited, Shares | shares	(8,938)
Shares, Outstanding at September 30, 2015 | shares	483,356
Weighted-Average Grant Date Fair Value, Outstanding at January 1, 2015	$ 31.38
Granted, Weighted-Average Grant Date Fair Value	39.21
Vested and issued, Weighted-Average Grant Date Fair Value	26.83
Expired or forfeited, Weighted-Average Grant Date Fair Value	41.76
Weighted-Average Grant Date Fair Value, Outstanding at September 30, 2015	$ 37.14

Share-based Compensation - Su64

Share-based Compensation - Summary of Stock-Settled SARs Activity (Detail) - Stock-Settled SARs Activity [Member]	9 Months Ended
	Sep. 30, 2015$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2015 | shares	1,313,726
Granted, Shares | shares	243,305
Exercised, Shares | shares	(165,036)
Expired or forfeited, Shares | shares	(7,231)
Shares, Outstanding at September 30, 2015 | shares	1,384,764
Weighted-Average Exercise Price, Outstanding at January 1, 2015	$ 28.57
Granted, Weighted-Average Exercise Price	39.43
Exercised, Weighted-Average Exercise Price	24.15
Expired or forfeited, Weighted-Average Exercise Price	31.68
Weighted-Average Exercise Price, Outstanding at September 30, 2015	$ 30.14

Share-based Compensation - Su65

Share-based Compensation - Summary of Cash-Settled SARs Activity (Detail) - Cash-Settled SARs Activity [Member]	9 Months Ended
	Sep. 30, 2015$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2015 | shares	2,001,451
Granted, Shares | shares	913,157
Exercised, Shares | shares	(366,527)
Expired or forfeited, Shares | shares	(216,354)
Shares, Outstanding at September 30, 2015 | shares	2,331,727
Weighted-Average Exercise Price, Outstanding at January 1, 2015	$ 32.76
Granted, Weighted-Average Exercise Price	47.48
Exercised, Weighted-Average Exercise Price	29.19
Expired or forfeited, Weighted-Average Exercise Price	39.40
Weighted-Average Exercise Price, Outstanding at September 30, 2015	$ 38.46

Underwriting, Acquisition and66

Underwriting, Acquisition and Insurance Expenses - Underwriting, Acquisition and Insurance Expenses (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Underwriting Acquisition And Insurance Expenses [Abstract]
Commissions	$ 56.5	$ 59.8	$ 182.4	$ 178
General expenses	69.6	69	222.2	211.9
Premium taxes, boards and bureaus	7.5	7.2	8.1	19.5
Underwriting, acquisition and insurance expenses, total	133.6	136	412.7	409.4
Net deferral of policy acquisition costs	(0.8)	(2.2)	(10.8)	(10.1)
Total underwriting, acquisition and insurance expenses	$ 132.8	$ 133.8	$ 401.9	$ 399.3

Underwriting, Acquisition and67

Underwriting, Acquisition and Insurance Expenses - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Underwriting Acquisition And Insurance Expenses [Abstract]
Share-based payments expense	$ 5.5	$ 2.2	$ 20.8	$ 13.3

Income Taxes - Income Tax Provi

Income Taxes - Income Tax Provision (Benefit) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Current tax provision	$ (11.3)	$ (15)	$ (2.5)	$ (10.7)
Future tax deductions	14.1	19.7	16.7	52.9
Valuation allowance change	(1.9)	(1.1)	(2.9)	(30)
Income tax provision	$ 0.9	$ 3.6	$ 11.3	$ 12.2

Income Taxes - Schedule of Pre-

Income Taxes - Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 36.2		$ 48.3	$ 133.3		$ 135.7
Bermuda [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 24.6		$ 27.5	$ 68.8		$ 74.3
Effective Tax Rate	0.00%		0.00%	0.00%		0.00%
United States [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 10.5		$ 13.5	$ 59.1		$ 49.2
Effective Tax Rate	19.60%		16.20%	22.40%		20.90%
United Kingdom [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 1.9		$ 9.2	$ 9.1		$ 11.1
Effective Tax Rate	(58.50%)		15.40%	(21.40%)		17.10%
Belgium [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0	[1]	$ (0.1)	$ (0.1)		$ (0.1)
Effective Tax Rate	31.40%		(7.90%)	(50.50%)		(32.40%)
Brazil [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ (0.7)		$ (1.2)	$ (3.7)		$ 3.9
Effective Tax Rate	0.00%		0.00%	0.00%		0.00%
United Arab Emirates [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.1		$ 0	$ 0.2		$ (0.9)
Effective Tax Rate	0.00%		0.00%	0.00%		0.00%
Ireland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0	[1]	$ 0	$ (0.1)		$ 0
Effective Tax Rate	0.00%		0.00%	0.00%		0.00%
Malta [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ (0.3)		$ (0.8)	$ 0	[1]	$ (1.8)
Effective Tax Rate	0.00%		0.00%	0.00%		0.00%
Switzerland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.1		$ 0.2	$ 0	[1]	$ 0	[1]
Effective Tax Rate	(20.00%)		4.80%	(21.30%)		24.20%
[1]	Pre-tax income for the respective year was less than $0.1 million.

Income Taxes - Schedule of Pr70

Income Taxes - Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 36.2	$ 48.3	$ 133.3		$ 135.7
Switzerland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	0.1	0.2	0	[1]	0	[1]
Maximum [Member] | Switzerland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.1	$ 0.1	$ 0.1		$ 0.1
[1]	Pre-tax income for the respective year was less than $0.1 million.

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	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Income tax provision at expected rate	$ 3.7	$ 6.1	$ 21.1	$ 20.6
Tax-exempt interest	(1.2)	(1.1)	(3.1)	(3.4)
Dividends received deduction	(0.6)	(0.5)	(1.8)	(1.7)
Valuation allowance change	(1.9)	(1.1)	(2.9)	(30)
Other permanent adjustments, net	0.1	(0.1)	0.3	(1)
Adjustment for prior year tax return	(0.6)	(1.1)	(0.6)	(1.1)
Adjustment for annualized rate	0.8	0.8	0.6	(0.9)
United States state tax (benefit) expense	0	0	(2.5)	0
Capital loss carryforward from prior merger	0	0	0	29.8
Other foreign adjustments	0.1	0	0.2	0
Prior period adjustments to deferred	0	0.8	0	(0.3)
Prior year foreign taxes recovered	0	0	(1.2)	0
Foreign exchange adjustments	0.5	(0.2)	0.9	(0.1)
Foreign withholding taxes	0	0	0.3	0.3
Income tax provision	0.9	3.6	11.3	12.2
Income tax (benefit) provision - Foreign	(1.2)	1.5	(2)	2
Income tax provision - United States, Federal	2.1	2.1	16.8	9.8
Income tax (benefit) provision - United States, state	0	0	(3.8)	0.1
Foreign withholding tax - United States	$ 0	$ 0	$ 0.3	$ 0.3

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Income Taxes Disclosure [Line Items]
Net operating losses carryback period	2 years
Capital losses carryback period	3 years
Total net deferred tax liabilities	$ 10,800,000
Net operating loss carryforward	17,100,000
Valuation allowance	22,600,000
Loss carryforwards per year	2,800,000
Unrecognized tax benefits	0	$ 0
ARIS [Member]
Income Taxes Disclosure [Line Items]
Net operating loss carryforward	1,000,000
Malta [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	2,000,000
Decreased valuation allowance	100,000
Brazil [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	5,500,000
Increased valuation allowance	2,100,000
PXRE Reinsurance Company [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	15,100,000
Reduced valuation allowance	700,000
December 31, 2025 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized	15,600,000
December 31, 2027 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized	1,500,000
December 31, 2027 [Member] | ARIS [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized	200,000
December 31, 2028 [Member] | ARIS [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized	400,000
December 31, 2029 [Member] | ARIS [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized	$ 400,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)
Disclosure - Commitments and Contingencies - Additional Information (Detail) [Line Items]
Contractual commitments related to its limited partnership investments	$ 71.6
Minimum [Member]
Disclosure - Commitments and Contingencies - Additional Information (Detail) [Line Items]
Contractual commitments period	1 year
Maximum [Member]
Disclosure - Commitments and Contingencies - Additional Information (Detail) [Line Items]
Contractual commitments period	13 years

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)Segment	Dec. 31, 2014USD ($)
Segment Reporting [Abstract]
Number of reportable segments	4
Assets associated with trade capital providers | $	$ 396.3	$ 315.4

Segment Information - Revenue a

Segment Information - Revenue and Income (Loss) Before Income Taxes for Each Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Earned premiums	$ 346	$ 337.6	$ 1,026.6	$ 999.4
Net investment income	21.3	20.8	63.9	64.7
Fee and other income (expense), net	1	1.6	(0.1)	0.1
Net realized investment and other gains	3.7	12.9	25	42.5
Total revenue	372	372.9	1,115.4	1,106.7
Income before income taxes	36.2	48.3	133.3	135.7
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net investment income	0.6	0.6	1.9	2.5
Income before income taxes	(9.7)	(4.7)	(30.3)	(25.4)
Operating Segments [Members]
Segment Reporting Information [Line Items]
Income before income taxes	42.2	40.1	138.6	118.6
Excess and Surplus Lines [Member]
Segment Reporting Information [Line Items]
Earned premiums	135.7	121.2	389.9	363.9
Net investment income	8.8	8.9	26.3	27.2
Excess and Surplus Lines [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income before income taxes	26.5	27.6	75.4	75.9
Commercial Specialty [Member]
Segment Reporting Information [Line Items]
Earned premiums	73.3	72.7	217.6	215.5
Net investment income	4.6	4.5	13.8	13.8
Commercial Specialty [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income before income taxes	12.4	8	20.8	9.2
International Specialty [Member]
Segment Reporting Information [Line Items]
Earned premiums	37.6	38	113.2	112.6
Net investment income	2.9	2.3	8.8	6.1
International Specialty [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income before income taxes	3.5	4	21.4	16.4
Syndicate 1200 [Member]
Segment Reporting Information [Line Items]
Earned premiums	99.1	104.4	305.5	305.9
Net investment income	2.3	2.1	6.9	7.9
Syndicate 1200 [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income before income taxes	6.9	8.8	28	34.7
Run Off Lines [Member]
Segment Reporting Information [Line Items]
Earned premiums	0.3	1.3	0.4	1.5
Net investment income	2.1	2.4	6.2	7.2
Run Off Lines [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income before income taxes	$ (7.1)	$ (8.3)	$ (7)	$ (17.6)

Segment Information - Schedule

Segment Information - Schedule of Earned Premiums by Geographic Location (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	$ 346	$ 337.6	$ 1,026.6	$ 999.4
Bermuda [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	26.8	27	76.8	75.7
Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	10.3	11	34.7	35.4
Malta [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	0.5	0.5	1.4	1.6
United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	99.1	104.4	305.5	305.9
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	$ 209.3	$ 194.7	$ 608.2	$ 580.8

Segment Information - Identifia

Segment Information - Identifiable Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 6,627.5	$ 6,356.3	[1]
Excess and Surplus Lines [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	2,461.4	2,350.7
Commercial Specialty [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	1,387.9	1,358.5
International Specialty [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	801	776.8
Syndicate 1200 [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	1,353.1	1,258.5
Run Off Lines [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	557.7	552.8
Corporate and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 66.4	$ 59
[1]	Derived from audited consolidated financial statements.

Information Provided in Conne78

Information Provided in Connection with Outstanding Debt of Subsidiaries - Condensed Consolidating Balance Sheet (Detail) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014		Sep. 30, 2014	Dec. 31, 2013
Assets
Investments		$ 4,133	$ 4,097.9	[1]
Cash		96.2	81	[1]	$ 73.1	$ 157.4
Accrued investment income		21	22.1	[1]
Premiums receivable		437.4	353.6	[1]
Reinsurance recoverables		1,067.3	997.2	[1]
Goodwill and other intangible assets, net		226.6	230.8
Current income taxes receivable, net		17.1	14.9	[1]
Deferred acquisition costs, net		141.4	124.6	[1]
Ceded unearned premiums		262.5	207.6	[1]
Other assets		225	226.6	[1]
Due from (to) affiliates		0	0
Intercompany note receivable		0	0
Investments in subsidiaries		0	0
Total assets		6,627.5	6,356.3	[1]
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses		3,104.1	3,042.4	[1]	3,062.6
Unearned premiums		932.7	817.2	[1]
Funds held and ceded reinsurance payable, net		366.9	233.8
Long-term debt		373.9	378.5
Deferred tax liabilities, net		33.4	53	[1]
Accrued underwriting expenses and other liabilities		175	184.7
Total liabilities		4,986	4,709.6	[1]
Total shareholders' equity		1,641.5	1,646.7	[1]
Total liabilities and shareholders' equity		6,627.5	6,356.3	[1]
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]
Assets
Investments		6.4	0.7
Cash		0	0		0	0
Accrued investment income		0	0
Premiums receivable		0	0
Reinsurance recoverables		0	0
Goodwill and other intangible assets, net		0	0
Current income taxes receivable, net		0	0
Deferred acquisition costs, net		0	0
Ceded unearned premiums		0	0
Other assets		9.7	9.6
Due from (to) affiliates		(52.5)	2.9
Intercompany note receivable		0	0
Investments in subsidiaries		1,722.3	1,698
Total assets		1,685.9	1,711.2
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses		0	0
Unearned premiums		0	0
Funds held and ceded reinsurance payable, net		0	0
Long-term debt		28.3	49
Deferred tax liabilities, net		0	0
Accrued underwriting expenses and other liabilities		16.1	15.5
Total liabilities		44.4	64.5
Total shareholders' equity		1,641.5	1,646.7
Total liabilities and shareholders' equity		1,685.9	1,711.2
Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) [Member]
Assets
Investments		2,830.2	2,841.5
Cash		84.8	49.3		69	132.1
Accrued investment income		15.9	17.8
Premiums receivable		166.7	154.6
Reinsurance recoverables		1,195.4	1,173.6
Goodwill and other intangible assets, net		130	131.7
Current income taxes receivable, net		12.3	10.1
Deferred acquisition costs, net		61.8	58
Ceded unearned premiums		119.8	98.5
Other assets		155.3	174.1
Due from (to) affiliates		1.5	(19.8)
Intercompany note receivable		41.7	72
Investments in subsidiaries		0	0
Total assets		4,815.4	4,761.4
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses		2,177.9	2,136.4
Unearned premiums		506.9	448.9
Funds held and ceded reinsurance payable, net		695.5	675.1
Long-term debt		288.7	288.7
Deferred tax liabilities, net		24	41.2
Accrued underwriting expenses and other liabilities		98.4	104.2
Total liabilities		3,791.4	3,694.5
Total shareholders' equity		1,024	1,066.9
Total liabilities and shareholders' equity		4,815.4	4,761.4
Other Subsidiaries and Eliminations [Member]
Assets
Investments	[2]	1,296.4	1,255.7
Cash	[2]	11.4	31.7		22.1	25.3
Accrued investment income	[2]	5.1	4.3
Premiums receivable	[2]	270.7	199
Reinsurance recoverables	[2]	(128.1)	(176.4)
Goodwill and other intangible assets, net	[2]	96.6	99.1
Current income taxes receivable, net	[2]	4.8	4.8
Deferred acquisition costs, net	[2]	79.6	66.6
Ceded unearned premiums	[2]	142.7	109.1
Other assets	[2]	66.4	67.9
Due from (to) affiliates	[2]	(1.5)	19.8
Intercompany note receivable	[2]	(41.7)	(72)
Investments in subsidiaries	[2]	0	0
Total assets	[2]	1,802.4	1,609.6
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses	[2]	926.2	906
Unearned premiums	[2]	425.8	368.3
Funds held and ceded reinsurance payable, net	[2]	(328.6)	(441.3)
Long-term debt	[2]	56.9	61.4
Deferred tax liabilities, net	[2]	9.4	11.8
Accrued underwriting expenses and other liabilities	[2]	60.5	65
Total liabilities	[2]	1,150.2	971.2
Total shareholders' equity	[2]	652.2	638.4
Total liabilities and shareholders' equity	[2]	1,802.4	1,609.6
Consolidating Adjustments [Member]
Assets
Investments	[3]	0	0
Cash	[3]	0	0		$ (18)	$ 0
Accrued investment income	[3]	0	0
Premiums receivable	[3]	0	0
Reinsurance recoverables	[3]	0	0
Goodwill and other intangible assets, net	[3]	0	0
Current income taxes receivable, net	[3]	0	0
Deferred acquisition costs, net	[3]	0	0
Ceded unearned premiums	[3]	0	0
Other assets	[3]	(6.4)	(25)
Due from (to) affiliates	[3]	52.5	(2.9)
Intercompany note receivable	[3]	0	0
Investments in subsidiaries	[3]	(1,722.3)	(1,698)
Total assets	[3]	(1,676.2)	(1,725.9)
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses	[3]	0	0
Unearned premiums	[3]	0	0
Funds held and ceded reinsurance payable, net	[3]	0	0
Long-term debt	[3]	0	(20.6)
Deferred tax liabilities, net	[3]	0	0
Accrued underwriting expenses and other liabilities	[3]	0	0
Total liabilities	[3]	0	(20.6)
Total shareholders' equity	[3]	(1,676.2)	(1,705.3)
Total liabilities and shareholders' equity	[3]	$ (1,676.2)	$ (1,725.9)
[1]	Derived from audited consolidated financial statements.
[2]	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations.
[3]	Includes all Argo Group parent company eliminations.

Information Provided in Conne79

Information Provided in Connection with Outstanding Debt of Subsidiaries - Condensed Consolidating Statement of Income (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Premiums and other revenue:
Earned premiums		$ 346	$ 337.6	$ 1,026.6	$ 999.4
Net investment income		21.3	20.8	63.9	64.7
Fee and other income (expense), net		1	1.6	(0.1)	0.1
Net realized investment and other gains (loss)		3.7	12.9	25	42.5
Total revenue		372	372.9	1,115.4	1,106.7
Expenses:
Losses and loss adjustment expenses		200	191.9	574.3	559.5
Underwriting, acquisition and insurance expenses		132.8	133.8	401.9	399.3
Interest expense		4.8	4.9	14.3	15
Foreign currency exchange loss (gain)		(1.8)	(6)	(8.4)	(2.8)
Total expenses		335.8	324.6	982.1	971
Income before income taxes		36.2	48.3	133.3	135.7
Provision for income taxes		0.9	3.6	11.3	12.2
Net income (loss) before equity in earnings of subsidiaries		35.3	44.7	122	123.5
Equity in undistributed earnings of subsidiaries		0	0	0	0
Net income		35.3	44.7	122	123.5
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]
Premiums and other revenue:
Earned premiums		0	0	0	0
Net investment income		(0.2)	(0.1)	(0.7)	(0.3)
Fee and other income (expense), net		0	0	0	0
Net realized investment and other gains (loss)		0	0	2	0
Total revenue		(0.2)	(0.1)	1.3	(0.3)
Expenses:
Losses and loss adjustment expenses		0	0	0	0
Underwriting, acquisition and insurance expenses		4.9	2.3	14.4	12.5
Interest expense		0.5	0.7	1.2	1.8
Foreign currency exchange loss (gain)		0	0	0	0
Total expenses		5.4	3	15.6	14.3
Income before income taxes		(5.6)	(3.1)	(14.3)	(14.6)
Provision for income taxes		0	0	0	0
Net income (loss) before equity in earnings of subsidiaries		(5.6)	(3.1)	(14.3)	(14.6)
Equity in undistributed earnings of subsidiaries		40.9	47.9	136.3	138.1
Net income		35.3	44.8	122	123.5
Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) [Member]
Premiums and other revenue:
Earned premiums		122.1	114.2	376	343.7
Net investment income		14.1	13.6	42.6	42.4
Fee and other income (expense), net		0	1.5	(2.4)	(1.5)
Net realized investment and other gains (loss)		1.4	9.2	24.7	34.6
Total revenue		137.6	138.5	440.9	419.2
Expenses:
Losses and loss adjustment expenses		75.4	69.9	220	211.2
Underwriting, acquisition and insurance expenses		48	51.6	149.5	147.9
Interest expense		3.8	3.8	11.4	11.4
Foreign currency exchange loss (gain)		0.1	0.3	1	0.1
Total expenses		127.3	125.6	381.9	370.6
Income before income taxes		10.3	12.9	59	48.6
Provision for income taxes		2.1	2.1	13.3	10.2
Net income (loss) before equity in earnings of subsidiaries		8.2	10.8	45.7	38.4
Equity in undistributed earnings of subsidiaries		0	0	0	0
Net income		8.2	10.8	45.7	38.4
Other Subsidiaries and Eliminations [Member]
Premiums and other revenue:
Earned premiums	[1]	223.9	223.4	650.6	655.7
Net investment income	[1]	7.6	7.3	22.2	22.6
Fee and other income (expense), net	[1]	1	0.1	2.3	1.6
Net realized investment and other gains (loss)	[1]	2.3	3.7	0.3	7.9
Total revenue	[1]	234.8	234.5	675.4	687.8
Expenses:
Losses and loss adjustment expenses	[1]	124.6	122	354.3	348.3
Underwriting, acquisition and insurance expenses	[1]	79.9	79.9	238	238.9
Interest expense	[1]	0.7	0.6	1.9	2.1
Foreign currency exchange loss (gain)	[1]	(1.9)	(6.3)	(9.4)	(2.9)
Total expenses	[1]	203.3	196.2	584.8	586.4
Income before income taxes	[1]	31.5	38.3	90.6	101.4
Provision for income taxes	[1]	(1.2)	1.5	(2)	2
Net income (loss) before equity in earnings of subsidiaries	[1]	32.7	36.8	92.6	99.4
Equity in undistributed earnings of subsidiaries	[1]	0	0	0	0
Net income	[1]	32.7	36.8	92.6	99.4
Consolidating Adjustments [Member]
Premiums and other revenue:
Earned premiums	[2]	0	0	0	0
Net investment income	[2]	(0.2)	0	(0.2)	0
Fee and other income (expense), net	[2]	0	0	0	0
Net realized investment and other gains (loss)	[2]	0	0	(2)	0
Total revenue	[2]	(0.2)	0	(2.2)	0
Expenses:
Losses and loss adjustment expenses	[2]	0	0	0	0
Underwriting, acquisition and insurance expenses	[2]	0	0	0	0
Interest expense	[2]	(0.2)	(0.2)	(0.2)	(0.3)
Foreign currency exchange loss (gain)	[2]	0	0	0	0
Total expenses	[2]	(0.2)	(0.2)	(0.2)	(0.3)
Income before income taxes	[2]	0	0.2	(2)	0.3
Provision for income taxes	[2]	0	0	0	0
Net income (loss) before equity in earnings of subsidiaries	[2]	0	0.2	(2)	0.3
Equity in undistributed earnings of subsidiaries	[2]	(40.9)	(47.9)	(136.3)	(138.1)
Net income	[2]	$ (40.9)	$ (47.7)	$ (138.3)	$ (137.8)
[1]	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations.
[2]	Includes all Argo Group parent company eliminations.

Information Provided in Conne80

Information Provided in Connection with Outstanding Debt of Subsidiaries - Condensed Consolidating Statement of Cash Flows (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014
Condensed Financial Statements Captions [Line Items]
Net cash flows from operating activities		$ 235.8		$ 71.7
Cash flows from investing activities:
Proceeds from sales of investments		728.8		976.1
Maturities and mandatory calls of fixed maturity investments		637.4		243.6
Purchases of investments		(1,468.5)		(1,264.8)
Change in short-term investments and foreign regulatory deposits		(62.4)		6
Settlements of foreign currency exchange forward contracts		(6.7)		0.6
Issuance of intercompany note, net		0		0
Purchases of fixed assets		(22)		(26.7)
Purchases of fixed assets and other, net		(4.6)		(48.2)
Cash used by investing activities		(176)		(86.7)
Cash flows from financing activities:
Borrowings under intercompany note, net		0		0
Activity under stock incentive plans		1.5		3.3
Redemption of trust preferred securities, net		0		(18)
Payment on note payable		0		(0.1)
Repurchase of Company's common shares		(29.7)		(40.9)
Excess tax expense from share-based payment arrangements		0.6		0.1
Payment of cash dividends to common shareholders		(17.1)		(13.4)
Cash used by financing activities		(44.7)		(69)
Effect of exchange rate changes on cash		0.1		(0.3)
Change in cash		15.2		(84.3)
Cash, beginning of period		81	[1]	157.4
Cash, end of period		96.2		73.1
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]
Condensed Financial Statements Captions [Line Items]
Net cash flows from operating activities		16.5		(16.5)
Cash flows from investing activities:
Proceeds from sales of investments		0		0
Maturities and mandatory calls of fixed maturity investments		0		0
Purchases of investments		0		0
Change in short-term investments and foreign regulatory deposits		1.3		0.1
Settlements of foreign currency exchange forward contracts		1.5		(0.5)
Issuance of intercompany note, net		0		0
Purchases of fixed assets and other, net		(3.8)		(7)
Cash used by investing activities		(1)		(7.4)
Cash flows from financing activities:
Borrowings under intercompany note, net		0		34
Activity under stock incentive plans		1.6		3.3
Redemption of trust preferred securities, net				0
Payment on note payable				0
Repurchase of Company's common shares		0		0
Excess tax expense from share-based payment arrangements		0		0
Payment of cash dividends to common shareholders		(17.1)		(13.4)
Cash used by financing activities		(15.5)		23.9
Effect of exchange rate changes on cash		0		0
Change in cash		0		0
Cash, beginning of period		0		0
Cash, end of period		0		0
Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) [Member]
Condensed Financial Statements Captions [Line Items]
Net cash flows from operating activities		130.6		11.8
Cash flows from investing activities:
Proceeds from sales of investments		524.5		609.2
Maturities and mandatory calls of fixed maturity investments		509.5		148
Purchases of investments		(1,073.2)		(773.1)
Change in short-term investments and foreign regulatory deposits		(34.5)		(12.5)
Settlements of foreign currency exchange forward contracts		0		0
Issuance of intercompany note, net		15		14.5
Purchases of fixed assets and other, net		(7.3)		(20.1)
Cash used by investing activities		(66)		(34)
Cash flows from financing activities:
Borrowings under intercompany note, net		0		0
Activity under stock incentive plans		0		0
Redemption of trust preferred securities, net				0
Payment on note payable				(0.1)
Repurchase of Company's common shares		(29.7)		(41)
Excess tax expense from share-based payment arrangements		0.6		0.1
Payment of cash dividends to common shareholders		0		0
Cash used by financing activities		(29.1)		(40.9)
Effect of exchange rate changes on cash		0		0
Change in cash		35.5		(63.1)
Cash, beginning of period		49.3		132.1
Cash, end of period		84.8		69
Other Subsidiaries and Eliminations [Member]
Condensed Financial Statements Captions [Line Items]
Net cash flows from operating activities	[2]	88.7		70
Cash flows from investing activities:
Proceeds from sales of investments	[2]	204.3		366.9
Maturities and mandatory calls of fixed maturity investments	[2]	127.9		95.6
Purchases of investments	[2]	(395.3)		(491.7)
Change in short-term investments and foreign regulatory deposits	[2]	(29.2)		18.4
Settlements of foreign currency exchange forward contracts	[2]	(8.2)		1.1
Issuance of intercompany note, net	[2]	(15)		(48.5)
Purchases of fixed assets and other, net	[2]	6.5		(14.7)
Cash used by investing activities	[2]	(109)		(72.9)
Cash flows from financing activities:
Borrowings under intercompany note, net	[2]	0		0
Activity under stock incentive plans	[2]	(0.1)		0
Redemption of trust preferred securities, net	[2]			0
Payment on note payable	[2]			0
Repurchase of Company's common shares	[2]	0		0
Excess tax expense from share-based payment arrangements	[2]	0		0
Payment of cash dividends to common shareholders	[2]	0		0
Cash used by financing activities	[2]	(0.1)		0
Effect of exchange rate changes on cash	[2]	0.1		(0.3)
Change in cash	[2]	(20.3)		(3.2)
Cash, beginning of period	[2]	31.7		25.3
Cash, end of period	[2]	11.4		22.1
Consolidating Adjustments [Member]
Condensed Financial Statements Captions [Line Items]
Net cash flows from operating activities	[3]	0		6.4
Cash flows from investing activities:
Proceeds from sales of investments	[3]	0		0
Maturities and mandatory calls of fixed maturity investments	[3]	0		0
Purchases of investments	[3]	0		0
Change in short-term investments and foreign regulatory deposits	[3]	0		0
Settlements of foreign currency exchange forward contracts	[3]	0		0
Issuance of intercompany note, net	[3]	0		34
Purchases of fixed assets and other, net	[3]	0		(6.4)
Cash used by investing activities	[3]	0		27.6
Cash flows from financing activities:
Borrowings under intercompany note, net	[3]	0		(34)
Activity under stock incentive plans	[3]	0		0
Redemption of trust preferred securities, net	[3]			(18)
Payment on note payable	[3]			0
Repurchase of Company's common shares	[3]	0		0
Excess tax expense from share-based payment arrangements	[3]	0		0
Payment of cash dividends to common shareholders	[3]	0		0
Cash used by financing activities	[3]	0		(52)
Effect of exchange rate changes on cash	[3]	0		0
Change in cash	[3]	0		(18)
Cash, beginning of period	[3]	0		0
Cash, end of period	[3]	$ 0		$ (18)
[1]	Derived from audited consolidated financial statements.
[2]	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations.
[3]	Includes all Argo Group parent company eliminations.