Argo Group International (ARGO-PA) 10-Q 4 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Oct. 31, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2,016
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		29,966,008

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015	[1]
Assets
Fixed maturities available-for-sale, at fair value (cost: 2016 - $3,008.8; 2015 - $2,971.0)	$ 3,044.6	$ 2,927.3
Equity securities available-for-sale, at fair value (cost: 2016 - $345.6; 2015 - $349.7)	453.7	463.9
Other investments (cost: 2016 - $518.7; 2015 - $506.9)	526.1	513.7
Short-term investments, at fair value (cost: 2016 - $289.2; 2015 - $211.2)	289.2	210.8
Total investments	4,313.6	4,115.7
Cash	123.6	121.7
Accrued investment income	21.9	21.6
Premiums receivable	503.4	404.5
Reinsurance recoverables	1,283.1	1,121.1
Goodwill	152.2	152.2
Intangible assets, net of accumulated amortization	68.9	73.3
Current income taxes receivable, net	0	11.6
Deferred acquisition costs, net	147.7	132.4
Ceded unearned premiums	311.6	250.8
Other assets	255.1	220.7
Total assets	7,181.1	6,625.6
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses	3,284.8	3,123.6
Unearned premiums	1,010.2	886.7
Accrued underwriting expenses	103	133.9
Ceded reinsurance payable, net	452.8	312.4
Funds held	65.7	77.6
Senior unsecured fixed rate notes	139.4	139.3
Other indebtedness	57.3	55.2
Junior subordinated debentures	172.7	172.7
Current income taxes payable, net	7.7	0
Deferred tax liabilities, net	40.7	23.6
Other liabilities	58.4	32.5
Total liabilities	5,392.7	4,957.5
Commitments and contingencies (Note 13)	0	0
Shareholders' equity:
Common shares - $1.00 par, 500,000,000 shares authorized; 39,980,160 and 37,104,294 shares issued at September 30, 2016 and December 31, 2015, respectively	40	37.1
Additional paid-in capital	1,119.8	964.9
Treasury shares (9,996,840 and 9,181,644 shares at September 30, 2016 and December 31, 2015, respectively)	(376.4)	(331.1)
Retained earnings	933.8	985.7
Accumulated other comprehensive income, net of taxes	71.2	11.5
Total shareholders' equity	1,788.4	1,668.1
Total liabilities and shareholders' equity	$ 7,181.1	$ 6,625.6
[1]	Derived from audited consolidated financial statements.

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015	[1]
Statement Of Financial Position [Abstract]
Available-for-sale cost	$ 3,008.8	$ 2,971
Equity securities cost	345.6	349.7
Other investments cost	518.7	506.9
Short-term investments, Cost	$ 289.2	$ 211.2
Common shares, par value	$ 1	$ 1
Common shares, shares authorized	500,000,000	500,000,000
Common shares, shares issued	39,980,160	37,104,294
Treasury shares, shares	9,996,840	9,181,644
[1]	Derived from audited consolidated financial statements.

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Premiums and other revenue:
Earned premiums	$ 358.7	$ 346	$ 1,048.5	$ 1,026.6
Net investment income	32.7	18.4	89.6	68.5
Fee and other income	7.6	9.2	20.2	17.9
Net realized investment and other gains	17.7	6.6	12.8	20.4
Total revenue	416.7	380.2	1,171.1	1,133.4
Expenses:
Losses and loss adjustment expenses	207.8	200	596	574.3
Underwriting, acquisition and insurance expenses	137.4	132.8	403	401.9
Interest expense	4.9	4.8	14.6	14.3
Fee and other expense	5.9	8.2	18.1	18
Foreign currency exchange (gain) loss	(1.5)	(1.8)	4.5	(8.4)
Total expenses	354.5	344	1,036.2	1,000.1
Income before income taxes	62.2	36.2	134.9	133.3
Provision for income taxes	7	0.9	21.1	11.3
Net income before equity in earnings of subsidiaries	55.2	35.3	113.8	122
Equity in undistributed earnings of subsidiaries	0	0	0	0
Net income	$ 55.2	$ 35.3	$ 113.8	$ 122
Net income per common share:
Basic	$ 1.84	$ 1.15	$ 3.76	$ 3.96
Diluted	1.80	1.13	3.68	3.89
Dividend declared per common share	$ 0.22	$ 0.18	$ 0.64	$ 0.55
Weighted average common shares:
Basic	30,018,637	30,707,233	30,227,725	30,796,390
Diluted	30,728,383	31,320,943	30,889,487	31,393,092
Net realized investment and other (losses) gains before other- than-temporary impairment losses	$ 20.1	$ 10	$ 21.8	$ 25.7
Other-than-temporary impairment losses recognized in earnings:
Other-than-temporary impairment losses on fixed maturities	(0.6)	0	(1.7)	(0.9)
Other-than-temporary impairment losses on equity securities	(1.8)	(3.4)	(7.3)	(4.4)
Impairment losses recognized in earnings	(2.4)	(3.4)	(9)	(5.3)
Net realized investment and other gains	$ 17.7	$ 6.6	$ 12.8	$ 20.4

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 55.2	$ 35.3	$ 113.8	$ 122
Other comprehensive income (loss):
Foreign currency translation adjustments	(1)	(4)	2.8	(6.6)
Unrealized gains (losses) on securities:
Gains (losses) arising during the year	19.8	(69.7)	97.7	(104.3)
Reclassification adjustment for gains included in net income	(17)	0.1	(25.1)	(6.9)
Other comprehensive income (loss) before tax	1.8	(73.6)	75.4	(117.8)
Unrealized gains (loss) on securities:
Gains (losses) arising during the year	7.6	(18.3)	27.5	(28.6)
Reclassification adjustment for gains included in net income	(7.9)	(1.7)	(11.8)	(4.6)
Income tax provision (benefit) related to other comprehensive income (loss)	(0.3)	(20)	15.7	(33.2)
Other comprehensive income (loss), net of tax	2.1	(53.6)	59.7	(84.6)
Comprehensive income (loss)	$ 57.3	$ (18.3)	$ 173.5	$ 37.4

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016		Sep. 30, 2015
Cash flows from operating activities:
Net income	$ 113.8		$ 122
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization and depreciation	27.4		30.7
Share-based payments expense	11.1		20.8
Excess tax benefit from share-based payment arrangements	(0.1)		(0.6)
Deferred income tax provision, net	2.3		13.8
Net realized investment and other gains	(12.8)		(20.4)
Undistributed earnings from alternative investment portfolio	(20.8)		(4.6)
Amortization of debt issuance costs	0.1		0.1
Loss on disposals of fixed assets, net	0.2		0.2
Change in:
Accrued investment income	(0.3)		1.1
Receivables	(255.5)		(162.2)
Deferred acquisition costs	(14.9)		(17.6)
Ceded unearned premiums	(59.8)		(58.5)
Reserves for losses and loss adjustment expenses	154.2		75.9
Unearned premiums	120.3		123
Ceded reinsurance payable and funds held	128.3		134.3
Income taxes	19.7		(2.3)
Accrued underwriting expenses	(27.4)		(19.7)
Other, net	(35.1)		(0.2)
Cash provided by operating activities	150.7		235.8
Cash flows from investing activities:
Sales of fixed maturity investments	761.8		609.8
Maturities and mandatory calls of fixed maturity investments	839		637.4
Sales of equity securities	155.3		61.6
Sales of other investments	92.1		57.4
Purchases of fixed maturity investments	(1,650.7)		(1,303.4)
Purchases of equity securities	(114.7)		(97.9)
Purchases of other investments	(90.3)		(67.2)
Change in foreign regulatory deposits and voluntary pools	4.8		7.5
Change in short-term investments	(78.7)		(69.9)
Settlements of foreign currency exchange forward contracts	(7.2)		(6.7)
Purchases of fixed assets	(26.7)		(22)
Other, net	31.9		17.4
Cash used in investing activities	(83.4)		(176)
Cash flows from financing activities:
Activity under stock incentive plans	0.6		1.5
Repurchase of Company's common shares	(45.3)		(29.7)
Excess tax expense from share-based payment arrangements	0.1		0.6
Payment of cash dividends to common shareholders	(19.8)		(17.1)
Cash used in financing activities	(64.4)		(44.7)
Effect of exchange rate changes on cash	(1)		0.1
Change in cash	1.9		15.2
Cash, beginning of period	121.7	[1]	81
Cash, end of period	$ 123.6		$ 96.2
[1]	Derived from audited consolidated financial statements.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2016
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, 2015, filed with the Securities and Exchange Commission on February 26, 2016. The interim financial information as of, and for the three and nine months ended, September 30, 2016 and 2015 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. During the first quarter of 2016, we evaluated our accounting for income from our alternative investment portfolio and determined that as we manage these investments to appreciate in value on a quarter to quarter basis, it is more appropriate to classify the change in value as net investment income as opposed to realized investment gains (losses). As a result, net investment income for the three and nine months ended September 30, 2016 includes $9.9 million and $20.8 million, respectively, related to the appreciation of our alternative investment portfolio. Net investment income and net realized and other gains for the three and nine months ended September 30, 2015 have been reclassified to reflect the current presentation. Specifically, net investment income for the three and nine months ended September 30, 2015 includes a decrease of $2.9 million and an increase of $4.6 million, respectively, related to the alternative investment portfolio, and net realized investment and other gains were increased for the three months ended September 30, 2015 and decreased for the nine months ended September 30, 2015 by these same amounts. 10% Stock Dividend On May 3, 2016, our Board of Directors declared a 10% stock dividend, payable on June 15, 2016, to shareholders of record at the close of business on June 1, 2016. As a result of the stock dividend, 2,735,542 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, 2016
Accounting Changes And Error Corrections [Abstract]
Recently Issued Accounting Pronouncements	2. Recently Issued Accounting Pronouncements In August 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-15, “Classification of Certain Cash Receipts and Cash Payments (Topic 230). ASU 2016-15 will reduce diversity in practice on how eight specific cash receipts and payments are classified on the statement of cash flows. The ASU will be effective for fiscal years beginning after December 15, 2017, including interim periods within those years. We are currently evaluating the impact that the adoption of ASU 2016-15 will have on our financial results and disclosures. In June 2016, the FASB issued ASU 2016-13, “Measurement of Credit Losses on Financial Instruments” (Topic 326). ASU 2016-13 requires organizations to estimate credit losses on certain types of financial instruments, including receivables and available-for-sale debt securities, by introducing an approach based on expected losses. The expected loss approach will require entities to incorporate considerations of historical information, current information and reasonable and supportable forecasts. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The guidance requires a modified retrospective transition method and early adoption is permitted. We are currently evaluating the impact that the adoption of ASU 2016-13 will have on our financial results and disclosures. In March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting” (Topic 718). ASU 2016-09 simplifies the accounting for share-based payment award transactions including income tax consequences, classification of awards as either equity or liabilities, classification on the statement of cash flows, and accounting for forfeitures. The guidance is effective for annual periods beginning after December 15, 2017, and interim periods within annual periods beginning December 15, 2018. In February 2016, the FASB issued ASU 2016-02, “Leases” (Topic 842). ASU 2016-02 requires organizations that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. Additionally, ASU 2016-02 modifies current guidance for lessors' accounting. ASU 2016-02 is effective for interim and annual reporting periods beginning on or after January 1, 2019, with early adoption permitted. We are currently evaluating the impact that the adoption of ASU 2016-02 will have on our financial results and disclosures. In January 2016, the FASB issued ASU 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities” (Subtopic 825-10). ASU 2016-01 will require equity investments that are not consolidated or accounted for under the equity method of accounting to be measured at fair value with changes in fair value recognized in net income. This ASU will also require us to assess the ability to realize our deferred tax assets (“DTAs”) related to an available-for-sale debt security in combination with our other DTAs. The ASU will be effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. We are currently evaluating the impact that the adoption of ASU 2016-01 will have on our financial results and disclosures. In May 2015, the FASB issued ASU 2015-09, “Disclosures about Short-Duration Contracts” (Topic 944). ASU 2015-09 requires additional disclosures for unpaid claim liabilities and claim adjustment expenses for short-duration insurance contracts (i.e., coverage provided for a fixed period of short duration, typically a year or less). The standard will require tables showing incurred and paid claims development information by accident year for the number of years claims typically remain outstanding, but not more than 10 years, including a reconciliation of this information to the statement of financial position. This ASU is effective for annual periods beginning after December 15, 2015 and interim periods within annual periods after December 15, 2016. This ASU will increase the volume and level of detail in our financial disclosures around reserves for losses and loss adjustment expenses in our Forms 10-K. In August 2014, the FASB issued ASU 2014-15, “Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern” (Subtopic 205-40). ASU 2014-15 requires entities to disclose whether there are conditions and events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the financial statements are issued. Management is also required to evaluate and disclose whether it plans to alleviate the doubt. The ASU will apply to both annual and interim reporting periods. The standard is effective for annual periods ending after December 15, 2016 and interim periods within annual periods beginning after December 15, 2016. We do not anticipate that the adoption of ASU 2014-15 will have a material impact on our financial disclosures. In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers” (Topic 606), which replaces most existing GAAP revenue recognition guidance and permits the use of either the retrospective or cumulative effect transition method. In August 2015, “Deferral of the Effective Date” (Topic 606), deferred the effective date of this guidance to interim and annual reporting periods beginning after December 15, 2017. Early adoption is permitted for fiscal years, and interim reporting periods within those years, beginning after December 15, 2016. Subsequently, in 2016, the FASB issued implementation guidance related to ASU 2014-09, including: • ASU 2016-08, “Principal versus Agent Considerations (Reporting Revenue Gross versus Net)” (Topic 606), which is intended to provide further clarification on the application of the principal versus agent implementation; • ASU 2016-10, “Identifying Performance Obligations and Licensing” (Topic 606), which is intended to clarify the guidance for identifying promised goods or services in a contract with a customer; • ASU 2016-11, “Rescission of SEC Guidance Because of Accounting Standards Updates 2014-09 and 2014-16 Pursuant to Staff Announcements at the March 3, 2016 EITF Meeting” (Topic 605 & 815); and • ASU 2016-12, “Narrow-Scope Improvements and Practical Expedients” (Topic 606), which amends certain aspects of ASU 2014-09 to address certain implementation issues. 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 do not anticipate such impact being material based on the limited revenue streams subject to the ASU. Accounting Standards Retrospectively Adopted in 2016 In April 2015, the FASB issued ASU 2015-03, “Simplifying the Presentation of Debt Issuance Costs,” which amends the guidance in Accounting Standards Codification Topic 835-30 “Interest – Imputation of Interest.” ASU 2015-03 requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. For public business entities, the guidance was effective for annual and interim periods beginning after December 15, 2015. We adopted this guidance effective January 1, 2016 and adjusted our prior period balances to reflect the adoption of this guidance. As of December 31, 2015, we reported $4.5 million of unamortized debt issuance costs related to our senior unsecured fixed rate notes. The effects of the retrospective application of this guidance on individual financial statement line items in our Consolidated Balance Sheets were as follows: December 31, 2015 (in millions) As Previously Reported As Adjusted Effect of Change Other assets $ 225.2 $ 220.7 $ (4.5 ) Senior unsecured fixed rate notes 143.8 139.3 (4.5 ) The effects of the retrospective application of this guidance on individual financial statement line items in our Consolidated Statements of Cash Flows were as follows: For the Nine Months Ended September 30, 2015 (in millions) As Previously Reported As Adjusted Effect of Change Cash flows from operating activities: Amortization of debt issuance costs $ — $ 0.1 $ 0.1 Other, net $ (0.1 ) $ (0.2 ) $ (0.1 ) There were no changes to the Consolidated Statements of Income for the periods presented as a result of adoption of the authoritative guidance.

Investments

Investments	9 Months Ended
	Sep. 30, 2016
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, 2016 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities USD denominated: U.S. Governments $ 216.4 $ 1.8 $ 0.2 $ 218.0 Non-U.S. Governments 92.7 0.8 — 93.5 Obligations of states and political subdivisions 387.0 20.8 0.1 407.7 Credit-Financial 494.3 11.4 0.5 505.2 Credit-Industrial 627.5 16.1 2.5 641.1 Credit-Utility 150.0 6.2 1.8 154.4 Structured securities: CMO/MBS-agency (1) 162.9 5.3 0.1 168.1 CMO/MBS-non agency 5.6 0.5 — 6.1 CMBS (2) 203.6 2.0 0.2 205.4 ABS (3) 122.5 0.5 0.2 122.8 CLO (4) 150.6 1.0 0.4 151.2 Foreign denominated: Governments 165.7 1.8 9.8 157.7 Credit 123.1 1.5 13.3 111.3 ABS/CMBS 18.1 — 2.8 15.3 CLO 88.8 2.8 4.8 86.8 Total fixed maturities 3,008.8 72.5 36.7 3,044.6 Equity securities 345.6 115.4 7.3 453.7 Other investments 518.7 7.5 0.1 526.1 Short-term investments 289.2 — — 289.2 Total investments $ 4,162.3 $ 195.4 $ 44.1 $ 4,313.6 (1) Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”). (2) Commercial mortgage-backed securities (“CMBS”). (3) Asset-backed securities (“ABS”). (4) December 31, 2015 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities USD denominated: U.S. Governments $ 207.9 $ 0.7 $ 0.7 $ 207.9 Non-U.S. Governments 93.0 0.1 1.3 91.8 Obligations of states and political subdivisions 467.6 20.7 0.3 488.0 Credit-Financial 502.3 6.2 2.6 505.9 Credit-Industrial 555.8 5.3 12.4 548.7 Credit-Utility 168.1 1.0 13.6 155.5 Structured securities: CMO/MBS-agency (1) 126.5 5.0 0.5 131.0 CMO/MBS-non agency 6.7 0.6 — 7.3 CMBS (2) 186.5 0.5 1.6 185.4 ABS (3) 111.0 0.2 0.7 110.5 CLO (4) 137.5 0.1 1.7 135.9 Foreign denominated: Governments 168.8 0.8 19.3 150.3 Credit 130.2 1.1 20.4 110.9 ABS/CMBS 19.7 0.1 2.2 17.6 CLO 89.4 0.7 9.5 80.6 Total fixed maturities 2,971.0 43.1 86.8 2,927.3 Equity securities 349.7 131.5 17.3 463.9 Other investments 506.9 6.9 0.1 513.7 Short-term investments 211.2 — 0.4 210.8 Total investments $ 4,038.8 $ 181.5 $ 104.6 $ 4,115.7 (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, 2016 and December 31, 2015 is $127.5 million and $95.3 million, respectively, of assets managed on behalf of the trade capital providers, who are third-party participants that provide underwriting capital to the operations of our Syndicate 1200 segment. Contractual Maturity The amortized cost and fair values of fixed maturity investments as of September 30, 2016, by contractual maturity, were as follows: (in millions) Amortized Cost Fair Value Due in one year or less $ 270.6 $ 264.4 Due after one year through five years 1,317.4 1,329.7 Due after five years through ten years 503.7 520.4 Thereafter 165.0 174.4 Structured securities 752.1 755.7 Total $ 3,008.8 $ 3,044.6 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, 2016 and December 31, 2015 were as follows: September 30, 2016 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 179.5 $ — Private equity 175.7 99.1 Long only funds 164.5 — Other investments 6.4 — Total other invested assets $ 526.1 $ 99.1 December 31, 2015 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 146.9 $ — Private equity 144.1 90.2 Long only funds 211.0 — Other investments 11.7 — Total other invested assets $ 513.7 $ 90.2 The following describes each investment type: • Hedge funds: Hedge funds include funds that primarily buy and sell stocks, including the short sales of stocks, 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 domestic and international stocks, a fund that owns high yield fixed income securities, our participation in pools, and a fund that primarily owns investment-grade corporate and sovereign fixed income securities. • Other investments: Other investments include foreign exchange currency forward contracts to manage exposure on losses related to global catastrophic events as well as certain 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, 2016 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) $ 57.2 $ 0.2 $ — $ — $ 57.2 $ 0.2 Non-U.S. Governments (1) (2) 19.7 — 0.3 — 20.0 — Obligations of states and political subdivisions 18.4 0.1 1.9 — 20.3 0.1 Credit-Financial 64.9 0.3 12.5 0.2 77.4 0.5 Credit-Industrial 54.2 1.3 34.3 1.2 88.5 2.5 Credit-Utility 7.2 0.1 12.6 1.7 19.8 1.8 Structured securities: CMO/MBS-agency (2) 38.8 0.1 4.5 — 43.3 0.1 CMO/MBS-non agency — — — — — — CMBS (2) 45.4 0.2 10.8 — 56.2 0.2 ABS (1) 15.2 — 5.0 0.2 20.2 0.2 CLO 15.1 0.1 44.5 0.3 59.6 0.4 Foreign denominated: Governments 107.9 9.8 — — 107.9 9.8 Credit 90.1 13.2 0.5 0.1 90.6 13.3 ABS/CMBS 13.1 2.3 1.9 0.5 15.0 2.8 CLO 51.9 4.2 6.9 0.6 58.8 4.8 Total fixed maturities 599.1 31.9 135.7 4.8 734.8 36.7 Equity securities 85.5 7.3 — — 85.5 7.3 Other investments 0.3 0.1 — — 0.3 0.1 Short-term investments (1) 3.0 — — — 3.0 — Total $ 687.9 $ 39.3 $ 135.7 $ 4.8 $ 823.6 $ 44.1 (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, 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) $ 138.3 $ 0.7 $ 0.4 $ — $ 138.7 $ 0.7 Non-U.S. Governments 80.2 1.2 2.2 0.1 82.4 1.3 Obligations of states and political subdivisions (1) 9.4 — 8.8 0.3 18.2 0.3 Credit-Financial 283.9 2.2 28.7 0.4 312.6 2.6 Credit-Industrial 343.9 10.3 31.0 2.1 374.9 12.4 Credit-Utility 112.8 8.6 17.6 5.0 130.4 13.6 Structured securities: CMO/MBS-agency 26.9 0.2 8.4 0.3 35.3 0.5 CMO/MBS-non agency (1) 3.8 — — — 3.8 — CMBS (2) 129.5 1.6 3.0 — 132.5 1.6 ABS 91.5 0.4 6.8 0.3 98.3 0.7 CLO 103.8 1.4 12.5 0.3 116.3 1.7 Foreign denominated: Governments 136.4 19.2 0.3 0.1 136.7 19.3 Credit 105.1 20.3 0.5 0.1 105.6 20.4 ABS/CMBS (2) 16.7 2.2 0.1 — 16.8 2.2 CLO 79.5 9.3 0.5 0.2 80.0 9.5 Total fixed maturities 1,661.7 77.6 120.8 9.2 1,782.5 86.8 Equity securities 112.4 17.3 — — 112.4 17.3 Other investments 0.3 0.1 — — 0.3 0.1 Short-term investments 5.8 0.4 — — 5.8 0.4 Total $ 1,780.2 $ 95.4 $ 120.8 $ 9.2 $ 1,901.0 $ 104.6 (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. 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 7,203 securities, of which 1,331 were in an unrealized loss position for less than one year and 264 were in an unrealized loss position for a period one year or greater as of September 30, 2016. 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, 2016. We recognized other-than-temporary losses on our fixed maturities portfolio of $0.6 million and $1.7 million for the three and nine months ended September 30, 2016, respectively. We recognized other-than-temporary losses on our fixed maturities portfolio of $0.0 million and $0.9 million for the three and nine months ended September 30, 2015, respectively. We recognized other-than-temporary losses on our equity portfolio of $1.8 million and $7.3 million for the three and nine months ended September 30, 2016, 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. 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) 2016 2015 2016 2015 Realized gains Fixed maturities $ 5.4 $ 2.9 $ 16.4 $ 10.5 Equity securities 20.8 9.8 45.4 22.6 Other investments 4.2 8.7 31.2 27.6 Short-term investments — — 0.4 1.1 Other assets 1.2 — 1.2 — Gain on sale of real estate holdings — — — 0.4 Gross realized investment gains 31.6 21.4 94.6 62.2 Realized losses Fixed maturities (6.1 ) (4.1 ) (21.0 ) (13.1 ) Equity securities (1.9 ) (2.5 ) (9.0 ) (3.6 ) Other investments (3.5 ) (4.6 ) (42.7 ) (18.2 ) Short-term investments — (0.1 ) (0.1 ) (1.5 ) Other assets — (0.1 ) — (0.1 ) Other-than-temporary impairment losses on fixed maturities (0.6 ) — (1.7 ) (0.9 ) Other-than-temporary impairment losses on equity securities (1.8 ) (3.4 ) (7.3 ) (4.4 ) Gross realized investment and other losses (13.9 ) (14.8 ) (81.8 ) (41.8 ) Net realized investment and other (losses) gains $ 17.7 $ 6.6 $ 12.8 $ 20.4 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 Investments Real Estate Holdings and Other Assets Tax Effects Total Three Months Ended September 30, 2016 Realized before impairments $ (0.7 ) $ 18.9 $ 0.7 $ — $ 1.2 $ (7.1 ) $ 13.0 Realized - impairments (0.6 ) (1.8 ) — — — 0.6 (1.8 ) Change in unrealized 13.7 (10.8 ) — (0.1 ) — 0.3 3.1 Three Months Ended September 30, 2015 Realized before impairments $ (1.2 ) $ 7.3 $ 4.1 $ (0.1 ) $ (0.1 ) $ (3.2 ) $ 6.8 Realized - impairments — (3.4 ) — — — 1.2 (2.2 ) Change in unrealized (22.6 ) (46.7 ) — (0.2 ) — 20.1 (49.4 ) Nine Months Ended September 30, 2016 Realized before impairments $ (4.6 ) $ 36.4 $ (11.5 ) $ 0.3 $ 1.2 $ (10.6 ) $ 11.2 Realized - impairments (1.7 ) (7.3 ) — — — 2.9 (6.1 ) Change in unrealized 78.5 (6.8 ) 0.6 0.3 — (15.7 ) 56.9 Nine Months Ended September 30, 2015 Realized before impairments $ (2.6 ) $ 19.0 $ 9.4 $ (0.4 ) $ 0.3 $ (9.6 ) $ 16.1 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 ) Foreign Currency Exchange Forward Contracts We entered into foreign currency exchange forward contracts to manage currency exposure on losses related to certain global catastrophe events, manage currency exposure on our Canadian dollar (“CAD”) investment portfolio, minimize negative impacts to our investment portfolio returns, manage currency exposure on certain Euro (“EUR”) denominated investments and gain exposure to a total return strategy which invests in multiple currencies. The fair value of our foreign currency exchange forward contracts as of September 30, 2016 and December 31, 2015 was as follows: September 30, December 31, (in millions) 2016 2015 Canadian dollar (CAD) currency exposure $ 1.3 $ 5.2 Euro (EUR) investment exposure (0.4 ) 2.9 Total return strategy 0.6 (0.8 ) $ 1.5 $ 7.3 The following table represents our gross investment realized gains and losses on our foreign currency exchange forward contracts: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2016 2015 2016 2015 Realized gains Global catastrophe (1) $ — $ — $ — $ 0.5 Canadian dollar (CAD) currency exposure 1.3 5.3 8.7 16.5 Euro (EUR) investment exposure — — 2.2 6.3 Investment portfolio return strategy — 3.3 0.3 3.7 Total return strategy 2.2 — 18.2 — Gross realized investment gains 3.5 8.6 29.4 27.0 Realized losses Global catastrophe (1) — (0.2 ) — (2.3 ) Canadian dollar (CAD) currency exposure (0.8 ) (0.4 ) (16.3 ) (5.2 ) Euro (EUR) investment exposure (0.8 ) — (4.5 ) (2.3 ) Investment portfolio return strategy — (3.3 ) (0.2 ) (4.2 ) Total return strategy (1.6 ) — (19.9 ) — Gross realized investment losses (3.2 ) (3.9 ) (40.9 ) (14.0 ) Net realized investment gains (losses) on foreign currency exchange forward contracts $ 0.3 $ 4.7 $ (11.5 ) $ 13.0 (1) Regulatory Deposits, Pledged Securities and Letters of Credit At September 30, 2016, the amortized cost and fair value of investments on deposit with U.S., Canadian and various other agencies for regulatory and other purposes were $164.4 million and $172.7 million, respectively. At December 31, 2015, the amortized cost and fair value of investments on deposit with U.S., Canadian and various other agencies for regulatory and other purposes were $187.1 million and $192.8 million, respectively. At September 30, 2016, investments with an amortized cost of $39.5 million and fair value of $39.3 million were pledged as collateral in support of irrevocable letters of credit (“LOCs”) in the amount of $28.1 million issued under the terms of certain reinsurance agreements in respect of reported loss and loss expense reserves. At December 31, 2015, investments with an amortized cost of $34.9 million and fair value of $35.0 million were pledged as collateral in support of irrevocable LOCs in the amount of $29.3 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 $195.1 million and $202.5 million at September 30, 2016 and December 31, 2015, 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. • Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that can be accessed at the reporting date. We define actively traded as a security that has traded in the past seven days. We receive one quote per instrument for Level 1 inputs. • Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. We receive one quote per instrument for Level 2 inputs. • Level 3 inputs are unobservable inputs. Unobservable inputs reflect our own judgments about the assumptions market participants would use in pricing the asset or liability based on the best information available in the circumstances. We receive fair value prices from third-party pricing services and our outside investment managers. These prices are determined using observable market information such as dealer quotes, market spreads, cash flows, yield curves, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things. We have reviewed the processes used by the third-party providers for pricing the securities, and have determined that these processes result in fair values consistent with GAAP requirements. In addition, we review these prices for reasonableness, and have not adjusted any prices received from the third-party providers as of September 30, 2016. A description of the valuation techniques we use to measure assets at fair value is as follows: Fixed Maturities (Available-for-Sale) Levels 1 and 2: • United States Treasury securities are typically valued using Level 1 inputs. For these securities, we obtain fair value measurements from third-party pricing services using quoted prices (unadjusted) in active markets at the reporting date. • United States Government agencies, non-U.S. Government securities, obligations of states and political subdivisions, credit securities and foreign denominated securities are reported at fair value using Level 2 inputs. For these securities, we obtain fair value measurements from third-party pricing services. Observable data may include dealer quotes, market spreads, yield curves, live trading levels, trade execution data, credit information and the security’s terms and conditions, among other things. • CMO/MBS agency, CMO/MBS non-agency, CMBS, ABS and CLO securities are reported at fair value using Level 2 inputs. For these securities, we obtain fair value measurements from third-party pricing services. Observable data may include dealer quotes, market spreads, 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. 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 2: We own interest in a mutual fund that is reported at fair value using Level 2 inputs. The valuation is based on the fund’s net asset value per share, at the end of each month. The underlying assets in the fund are valued primarily on the basis of closing market quotations or official closing prices on each valuation day. 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, 2016. Based on an analysis of the inputs, our financial assets measured at fair value on a recurring basis have been categorized as follows: Fair (in millions) September 30, 2016 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities USD denominated: U.S. Governments $ 218.0 $ 174.3 $ 43.7 $ — Non-U.S. Governments 93.5 — 93.5 — Obligations of states and political subdivisions 407.7 — 407.7 — Credit-Financial 505.2 — 503.2 2.0 Credit-Industrial 641.1 — 641.1 — Credit-Utility 154.4 — 154.4 — Structured securities: CMO/MBS-agency 168.1 — 168.1 — CMO/MBS-non agency 6.1 — 6.1 — CMBS 205.4 — 205.4 — ABS 122.8 — 122.8 — CLO 151.2 — 151.2 — Foreign denominated: — — — Governments 157.7 — 157.7 — Credit 111.3 — 111.3 — ABS/CMBS 15.3 — 15.3 — CLO 86.8 — 86.8 — Total fixed maturities 3,044.6 174.3 2,868.3 2.0 Equity securities 453.7 451.2 2.1 0.4 Other fair value investments 86.8 — 86.8 — Short-term investments 289.2 275.0 14.2 — $ 3,874.3 $ 900.5 $ 2,971.4 $ 2.4 (a) Quoted prices in active markets for identical assets (b) Significant other observable inputs (c) Significant unobservable inputs Fair Value Measurements at Reporting Date Using (in millions) December 31, 2015 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities USD denominated: U.S. Governments $ 207.9 $ 150.4 $ 57.5 $ — Non-U.S. Governments 91.8 — 91.8 — Obligations of states and political subdivisions 488.0 — 488.0 — Credit-Financial 505.9 — 505.9 — Credit-Industrial 548.7 — 548.7 — Credit-Utility 155.5 — 155.5 — Structured securities: CMO/MBS-agency 131.0 — 131.0 — CMO/MBS-non agency 7.3 — 7.3 — CMBS 185.4 — 185.4 — ABS 110.5 — 110.5 — CLO 135.9 — 135.9 — Foreign denominated: Governments 150.3 — 150.3 — Credit 110.9 — 110.9 — ABS/CMBS 17.6 — 17.6 — CLO 80.6 — 80.6 — Total fixed maturities 2,927.3 150.4 2,776.9 — Equity securities 463.9 457.6 5.6 0.7 Other fair value investments 97.2 — 97.2 — Short-term investments 210.8 203.6 7.2 — $ 3,699.2 $ 811.6 $ 2,886.9 $ 0.7 (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) Credit Financial Equity Securities Total Beginning balance, January 1, 2016 $ — $ 0.7 $ 0.7 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 2.0 — 2.0 Issuances — — — Sales — (0.3 ) (0.3 ) Settlements — — — Ending balance, September 30, 2016 $ 2.0 $ 0.4 $ 2.4 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, 2016 $ — $ — $ — (in millions) Credit Financial 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 — (0.2 ) (0.2 ) Settlements — — — Ending balance, December 31, 2015 $ — $ 0.7 $ 0.7 Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2015 $ — $ — $ — At September 30, 2016 and December 31, 2015, 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, 2016
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) 2016 2015 Net reserves beginning of the year $ 2,133.3 $ 2,137.1 Add: Losses and LAE incurred during current calendar year, net of reinsurance: Current accident year 614.8 589.6 Prior accident years (18.8 ) (15.3 ) Losses and LAE incurred during calendar year, net of reinsurance 596.0 574.3 Deduct: Losses and LAE payments made during current calendar year, net of reinsurance: Current accident year 115.3 105.2 Prior accident years 403.9 435.5 Losses and LAE payments made during current calendar year, net of reinsurance: 519.2 540.7 Change in participation interest (1) (36.3 ) (1.2 ) Foreign exchange adjustments 1.0 (27.7 ) Net reserves - end of period 2,174.8 2,141.8 Add: Reinsurance recoverables on unpaid losses and LAE, end of period 1,110.0 962.3 Gross reserves - end of period $ 3,284.8 $ 3,104.1 (1) Amount represents decreases 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. The impact from the (favorable) unfavorable development of prior accident years’ loss and LAE reserves on each reporting segment is presented below: For the Nine Months Ended September 30, (in millions) 2016 2015 Excess and Surplus Lines $ (12.0 ) $ (18.4 ) Commercial Specialty (13.6 ) 3.7 International Specialty (8.3 ) (5.8 ) Syndicate 1200 (2.5 ) (2.8 ) Run-off Lines 17.6 8.0 Total favorable prior-year development $ (18.8 ) $ (15.3 ) The following describes the primary factors behind each segment’s prior accident year reserve development for the nine months ended September 30, 2016 and 2015: Nine months ended September 30, 2016: • Excess and Surplus Lines: Favorable development in the property lines, general and products liability lines, and commercial automobile • Commercial Specialty: Favorable development primarily in auto liability, surety, workers compensation, and property lines, partially offset by unfavorable development in other liability lines • International Specialty: Favorable development in the property reinsurance line, professional liability, and in the Brazil unit, partially offset by unfavorable development in the casualty unit • Syndicate 1200: Favorable development in property lines and marine and energy, partially offset by unfavorable development in specialty lines and professional indemnity • Run-off Lines: Unfavorable development primarily in asbestos and risk management liability Nine months ended September 30, 2015: • Excess and Surplus Lines: Favorable development in the general and products liability lines and commercial automobile, partially offset by unfavorable development in the property lines • Commercial Specialty: Unfavorable development in general liability and workers compensation due to increases in claim severity, partially offset by favorable development in auto liability, short-tail lines, and errors and omissions • International Specialty: Favorable development in the property reinsurance line, professional liability, casualty unit, partially offset by unfavorable development in the Brazil unit • Syndicate 1200: Favorable development in property, general liability and marine and energy, partially offset by unfavorable development in other liability classes and aerospace • Run-off Lines: Unfavorable development in workers compensation lines and asbestos and environmental liability, offset in part by favorable development in run-off reinsurance claims 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 favorable or unfavorable loss development, which may be material, will not occur.

Disclosures about Fair Value of

Disclosures about Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Disclosures about Fair Value of Financial Instruments	5. 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, 2016 and December 31, 2015, the carrying values of premiums receivable over 90 days were $13.3 million and $10.0 million, respectively. Included in “Reinsurance recoverables” in our Consolidated Balance Sheets at September 30, 2016 and December 31, 2015, 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 which is included in “Ceded reinsurance payable, net” in our accompanying Consolidated Balance Sheets. At September 30, 2016 and December 31, 2015, 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, 2016 and December 31, 2015, the carrying values over 90 days were $10.2 million and $7.1 million, respectively. Our methodology for establishing our allowances for doubtful accounts includes specifically identifying all potential uncollectible balances regardless of aging. At September 30, 2016 and December 31, 2015, the allowance for doubtful accounts for premiums receivable was $2.6 million and $3.5 million, respectively, and the allowance for doubtful accounts for reinsurance recoverables on paid losses was $1.8 million and $2.2 million, respectively. Premiums receivable over 90 days were secured by collateral in the amount of $0.5 million and $0.2 million at September 30, 2016 and December 31, 2015, respectively. Reinsurance recoverables on paid losses over 90 days were secured by collateral in the amount of $0.6 million and $0.7 at September 30, 2016 and December 31, 2015, respectively. Debt . At September 30, 2016 and December 31, 2015, 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, 2016 December 31, 2015 (in millions) Carrying Amount Fair Value Carrying Amount Fair Value Junior subordinated debentures $ 172.7 $ 172.7 $ 172.7 $ 166.5 Senior unsecured fixed rate notes 139.4 144.4 139.3 141.8 Other indebtedness: Floating rate loan stock 56.7 56.7 54.6 52.7 Note payable 0.6 0.6 0.6 0.6 $ 369.4 $ 374.4 $ 367.2 $ 361.6

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Shareholders' Equity	6. Shareholders’ Equity On May 3, 2016, our Board of Directors declared a 10% stock dividend, payable on June 15, 2016, to shareholders of record at the close of business on June 1, 2016. As a result of the stock dividend, 2,735,542 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 2, 2016, our Board of Directors declared a quarterly cash dividend in the amount of $0.22 on each share of common stock outstanding. On August 29, 2016, we paid $6.7 million to our shareholders of record on August 15, 2016. On August 4, 2015, our Board of directors declared a quarterly cash dividend in the amount of $0.18 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 May 3, 2016, our Board of Directors authorized the repurchase of up to $150.0 million of our common shares (“2016 Repurchase Authorization”). The 2016 Repurchase Authorization supersedes all the previous Repurchase Authorizations. As of September 30, 2016, availability under the 2016 Repurchase Authorization for future repurchases of our common shares was $132.0 million. For the nine months ended September 30, 2016, we repurchased a total of 815,196 common shares for $45.3 million. A summary of activity from January 1, 2016 through September 30, 2016 follows. A summary of common shares repurchased for the nine months ended September 30, 2016 is shown below: Repurchase Type Date Trading Plan Initiated 2016 Purchase Period Number of Shares Repurchased Average Price of Shares Repurchased Total Cost (in millions) Repurchase Authorization Year 10b5-1 Trading Plan 12/16/2015 01/04/2016-02/11/2016 266,538 $ 55.59 $ 14.8 2013 10b5-1 Trading Plan 03/16/2016 03/16/2016-05/02/2016 162,893 $ 55.62 9.1 2013 10b5-1 Trading Plan 06/16/2016 06/24/2016-06/28/2016 14,774 $ 49.78 0.7 2016 10b5-1 Trading Plan 09/15/2016 09/19/2016-09/28/2016 11,147 $ 55.38 0.6 2016 Open Market N/A 01/01/2016-05/02/2016 64,464 $ 54.14 3.5 2013 Open Market N/A 05/03/2016-09/30/2016 295,380 $ 56.38 16.6 2016 Total 815,196 $ 55.66 $ 45.3

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	7. 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, 2016 and 2015 is presented below: (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance, January 1, 2016 $ (21.6 ) $ 40.0 $ (6.9 ) $ 11.5 Other comprehensive (loss) income before reclassifications 2.8 70.2 — 73.0 Amounts reclassified from accumulated other comprehensive (loss) income — (13.3 ) — (13.3 ) Net current-period other comprehensive (loss) income 2.8 56.9 — 59.7 Balance at September 30, 2016 $ (18.8 ) $ 96.9 $ (6.9 ) $ 71.2 (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) income before reclassifications (6.6 ) (75.7 ) — (82.3 ) Amounts reclassified from accumulated other comprehensive (loss) income — (2.3 ) — (2.3 ) Net current-period other comprehensive (loss) income (6.6 ) (78.0 ) — (84.6 ) Balance at September 30, 2015 $ (22.2 ) $ 52.7 $ (7.0 ) $ 23.5 The following table illustrates the amounts reclassified from accumulated other comprehensive income (loss) 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) 2016 2015 2016 2015 Unrealized gains and losses on securities: Net realized investment (gains) losses $ (17.0 ) $ 0.1 $ (25.1 ) $ (6.9 ) Provision for income tax 7.9 1.7 11.8 4.6 Net of taxes $ (9.1 ) $ 1.8 $ (13.3 ) $ (2.3 )

Net Income Per Common Share

Net Income Per Common Share	9 Months Ended
	Sep. 30, 2016
Earnings Per Share [Abstract]
Net Income Per Common Share	8. Net Income Per Common Share The following table presents the calculation of net income per common share on a basic and diluted basis: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions, except number of shares and per share amounts) 2016 2015 2016 2015 Net income $ 55.2 $ 35.3 $ 113.8 $ 122.0 Weighted average common shares outstanding - basic 30,018,637 30,707,233 30,227,725 30,796,390 Effect of dilutive securities: Equity compensation awards 709,746 613,710 661,762 596,702 Weighted average common shares outstanding - diluted 30,728,383 31,320,943 30,889,487 31,393,092 Net income per common share: Basic $ 1.84 $ 1.15 $ 3.76 $ 3.96 Diluted $ 1.80 $ 1.13 $ 3.68 $ 3.89 Excluded from the weighted average common shares outstanding calculation at September 30, 2016, and 2015 are 9,996,840 shares and 9,181,544 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, 2016 and 2015, there were no equity compensation awards with an anti-dilutive effect.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2016
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	9. Supplemental Cash Flow Information Income taxes paid. We paid income taxes of $1.5 million and $10.8 million during the nine months ended September 30, 2016 and 2015, respectively. Income taxes recovered . We recovered income taxes of $0.5 million and $11.5 million during the nine months ended September 30, 2016 and 2015, respectively. Interest paid was as follows: For the Nine Months Ended September 30, (in millions) 2016 2015 Senior unsecured fixed rate notes $ 7.0 $ 7.0 Junior subordinated debentures 5.7 5.3 Other indebtedness 2.0 2.0 Total interest paid $ 14.7 $ 14.3

Share-based Compensation

Share-based Compensation	9 Months Ended
	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based Compensation	10. Share-based Compensation The fair value method of accounting is used for share-based compensation plans. Under the fair value method, compensation cost is measured based on the fair value of the award at the measurement date and recognized over the requisite service period. 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 risk-free rate of return assumption is based on the five-year U.S. Treasury constant maturity rate on the measurement date. The expected dividend yield is based on our history and expected dividend payouts. The expected award life is based upon the average holding period over the history of the incentive plan. The expected volatility assumption is based on the historical change in our stock price over the previous five years preceding the measurement date. The following table summarizes the assumptions we used for the nine months ended September 30, 2016 and 2015: For the Nine Months Ended September 30, 2016 2015 Risk-free rate of return 1.12% 1.44% Expected dividend yields 1.65% 1.52% Expected award life (years) 4.50 4.64 Expected volatility 18.73% 20.81% All outstanding awards were adjusted to reflect the 10% stock dividend declared on May 3, 2016, 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 unit 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. Restricted Shares A summary of restricted share activity as of September 30, 2016 and changes during the nine months then ended is as follows: Shares Weighted-Average Grant Date Fair Value Outstanding at January 1, 2016 514,742 $ 36.87 Granted 263,491 $ 50.41 Vested and issued (70,987 ) $ 32.70 Expired or forfeited (13,990 ) $ 44.13 Outstanding at September 30, 2016 693,256 $ 42.29 The restricted shares vest over two to four years. Expense recognized under this plan for the restricted shares was $1.7 million and $5.2 million for the three and nine months ended September 30, 2016, respectively, as compared to $1.4 million and $4.4 million for the three and nine months ended September 30, 2015, respectively. Compensation expense for all share-based compensation awards is included in “Underwriting, acquisition and insurance expenses” in the accompanying Consolidated Statements of Income. As of September 30, 2016, there was $19.9 million of total unrecognized compensation cost related to restricted share compensation arrangements granted by Argo Group. Stock-Settled SARs In January 2016, we modified certain unvested cash-settled SARs, converting the awards into stock-settled SARs. We evaluated this modification under the terms of ASU 718 “Share Based Payments,” and determined that no additional expense resulted from the conversion. The expense for the stock-settled SARs will be amortized over the remaining vesting period. A summary of stock-settled SARs activity as of September 30, 2016 and changes during the nine months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2016 1,438,146 $ 29.52 Granted 542 $ 36.71 Converted from cash-settled SARs 944,046 $ 41.21 Exercised (173,538 ) $ 25.42 Expired or forfeited (128,701 ) $ 42.03 Outstanding at September 30, 2016 2,080,495 $ 34.39 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 $1.0 million and $3.6 for the three and nine months ended September 30, 2016, respectively, as compared to $0.3 million and $1.3 million for the three and nine months ended September 30, 2015, respectively. As of September 30, 2016, there was $9.4 million of total unrecognized compensation cost related to stock-settled SARs outstanding. Cash-Settled SARs A summary of cash-settled SARs activity as of September 30, 2016 and changes during the nine months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2016 2,220,560 $ 35.53 Granted 540 $ 36.71 Converted to stock-settled SARs (1) (864,036 ) $ 41.21 Exercised (565,096 ) $ 31.37 Expired or forfeited (111,709 ) $ 39.23 Outstanding at September 30, 2016 680,259 $ 31.16 (1) The converted shares were not adjusted for the 10% stock dividend because the conversion occurred prior to the stock dividend record date. 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 $2.6 million and $2.1

Underwriting, Acquisition and I

Underwriting, Acquisition and Insurance Expenses	9 Months Ended
	Sep. 30, 2016
Underwriting Acquisition And Insurance Expenses [Abstract]
Underwriting, Acquisition and Insurance Expenses	11. 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) 2016 2015 2016 2015 Commissions $ 59.3 $ 56.5 $ 178.5 $ 182.4 General expenses 75.6 69.6 217.3 222.2 Premium taxes, boards and bureaus 6.1 7.5 19.0 8.1 141.0 133.6 414.8 412.7 Net deferral of policy acquisition costs (3.6 ) (0.8 ) (11.8 ) (10.8 ) Total underwriting, acquisition and insurance expenses $ 137.4 $ 132.8 $ 403.0 $ 401.9 Included in general expenses for the three months ended September 30, 2016 and 2015 was $5.5 million and $7.9 million, respectively, and $11.1 million and $20.8 million for the nine months ended September 30, 2016, and 2015, respectively, of expense for our total equity-related compensation. The increase in premium taxes, boards and bureaus for the nine months ended September 30, 2016 as compared to the nine months ended September 30, 2015 was primarily due to a decline in the accrual for premium taxes and other assessments due to a change in accounting estimate in the first quarter of 2015.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	12. 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. Eight of the United Kingdom subsidiaries are deemed to be engaged in business in the United States, and therefore, are subject to United States corporate tax in respect of a proportion of their United States underwriting business only. Relief is available against the United Kingdom tax liabilities in respect of overseas taxes paid that arise from the underwriting business. Our United Kingdom subsidiaries file separate United Kingdom income tax returns. We have subsidiaries based in the United States that are subject to United States tax laws. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Our United States subsidiaries 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) 2016 2015 2016 2015 Current tax provision $ 10.8 $ (11.3 ) $ 18.8 $ (2.5 ) Deferred tax provision (benefit) related to: Future tax deductions (3.0 ) 14.1 1.9 16.7 Valuation allowance change (0.8 ) (1.9 ) 0.4 (2.9 ) Income tax provision $ 7.0 $ 0.9 $ 21.1 $ 11.3 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 Months Ended September 30, (in millions) 2016 2015 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 35.6 0.0 % $ 24.6 0.0 % United States 28.2 24.2 % 10.5 19.6 % United Kingdom (2.8 ) -3.0 % 1.9 -58.5 % Belgium — (1) -160.0 % — (1) 31.4 % Brazil 0.4 0.0 % (0.7 ) 0.0 % United Arab Emirates — (1) 0.0 % 0.1 0.0 % Ireland (0.1 ) 0.0 % — (1) 0.0 % Malta 0.9 0.0 % (0.3 ) 0.0 % Switzerland — (1) 21.2 % 0.1 -20.0 % Pre-tax income $ 62.2 $ 36.2 For the Nine Months Ended September 30, (in millions) 2016 2015 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 79.7 0.0 % $ 68.8 0.0 % United States 78.0 26.3 % 59.1 22.4 % United Kingdom (24.9 ) -1.9 % 9.1 -21.4 % Belgium — (1) 0.0 % (0.1 ) -50.5 % Brazil 1.1 0.0 % (3.7 ) 0.0 % United Arab Emirates — (1) 0.0 % 0.2 0.0 % Ireland (0.2 ) 0.0 % (0.1 ) 0.0 % Malta 1.2 0.0 % — (1) 0.0 % Switzerland — (1) 21.1 % — (1) -21.3 % Pre-tax income $ 134.9 $ 133.3 (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) 2016 2015 2016 2015 Income tax provision at expected rate $ 9.8 $ 3.7 $ 23.2 $ 21.1 Tax effect of: Tax-exempt interest (0.7 ) (1.2 ) (2.5 ) (3.1 ) Dividends received deduction (0.4 ) (0.6 ) (1.7 ) (1.8 ) Valuation allowance change (0.8 ) (1.9 ) 0.4 (2.9 ) Other permanent adjustments, net 0.1 0.1 0.3 0.3 Adjustment for prior year tax return (0.8 ) (0.6 ) (0.8 ) (0.6 ) Adjustment for annualized rate (0.9 ) 0.8 (1.5 ) 0.6 United States state tax (benefit) expense — — — (2.5 ) Other foreign adjustments (0.1 ) 0.1 (0.7 ) 0.2 Prior year foreign taxes recovered — — — (1.2 ) Deferred tax rate reduction — — (0.3 ) — Foreign exchange adjustments 0.8 0.5 4.4 0.9 Foreign withholding taxes — — 0.3 0.3 Income tax provision $ 7.0 $ 0.9 $ 21.1 $ 11.3 Income tax provision (benefit) - Foreign $ 0.2 $ (1.2 ) $ 0.6 $ (2.0 ) Income tax provision - United States, Federal 6.8 2.1 20.2 16.8 Income tax benefit - United States, State — — — (3.8 ) Foreign withholding tax - United States — — 0.3 0.3 Income tax provision $ 7.0 $ 0.9 $ 21.1 $ 11.3 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, generally two years for net operating losses and three years for capital losses for our United States operations. At September 30, 2016, we had a total net deferred tax liability of $17.5 million prior to any valuation allowance. Management has determined that a valuation allowance is required for a portion of the tax-effected net operating loss carryforward included as part of the United States consolidated group of $16.1 million generated from PXRE Corporation and for the tax-effected net operating loss carryforward of $1.0 million from ARIS. 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. Furthermore, 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 $23.2 million is required as of September 30, 2016 of which $14.2 million relates to the PXRE Corporation and ARIS loss carryforwards, $7.5 million relates to Brazil operations, and $1.5 million relates to Malta operations. For the nine months ended September 30, 2016, the valuation allowance was reduced by $0.7 million pertaining to PXRE Corporation and ARIS loss carryforwards, and increased by $1.4 million pertaining to our Brazil operations, and decreased by $0.3 million pertaining to our Malta operations. Of the PXRE Corporation net operating loss carryforwards, $14.6 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. For any uncertain tax positions not meeting the “more-likely-than-not” recognition threshold, accounting standards require recognition, measurement and disclosure in a company’s financial statements. We had no material unrecognized tax benefits as of September 30, 2016 and 2015. Our United States subsidiaries are no longer subject to U.S. federal and state income tax examinations by tax authorities for years before 2012. 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, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. 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 $99.1 million related to our limited partnership investments at September 30, 2016. These commitments will be funded as required by the partnership agreements which can be called to be fulfilled at any time, not to exceed thirteen years.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2016
Segment Reporting [Abstract]
Segment Information	14. 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. Based on management’s evaluation of the Argo Pro platform’s shift in primary distribution channels and mix of admitted versus non-admitted business, we have reclassified Argo Pro’s results of operations and identifiable assets from the Excess and Surplus Lines segment to the Commercial Specialty segment effective January 1, 2016, as the current makeup of the platform more closely aligns with our Commercial Specialty segment. The results of operations and identifiable assets for prior periods have been reclassified to conform to the current presentation. 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) 2016 2015 2016 2015 Revenue: Earned premiums Excess and Surplus Lines $ 122.3 $ 121.5 $ 363.4 $ 351.8 Commercial Specialty 94.0 87.5 266.3 255.7 International Specialty 39.9 36.4 117.4 109.8 Syndicate 1200 102.4 100.3 301.1 308.9 Run-off Lines 0.1 0.3 0.3 0.4 Total earned premiums 358.7 346.0 1,048.5 1,026.6 Net investment income Excess and Surplus Lines 12.7 7.2 35.1 24.6 Commercial Specialty 7.6 4.4 20.7 15.1 International Specialty 4.7 2.5 13.0 8.7 Syndicate 1200 2.8 1.9 9.7 6.7 Run-off Lines 3.2 1.7 8.8 6.1 Corporate and Other 1.7 0.7 2.3 7.3 Total net investment income 32.7 18.4 89.6 68.5 Fee and other income 7.6 9.2 20.2 17.9 Net realized investment and other gains 17.7 6.6 12.8 20.4 Total revenue $ 416.7 $ 380.2 $ 1,171.1 $ 1,133.4 For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2016 2015 2016 2015 Income (loss) before income taxes Excess and Surplus Lines $ 22.8 $ 22.0 $ 69.0 $ 64.1 Commercial Specialty 23.1 15.1 57.2 31.7 International Specialty 15.2 3.1 32.4 21.1 Syndicate 1200 4.9 6.5 20.7 28.0 Run-off Lines (10.0 ) (6.9 ) (14.6 ) (6.6 ) Total segment income before taxes 56.0 39.8 164.7 138.3 Corporate and Other (11.5 ) (10.2 ) (42.6 ) (25.4 ) Net realized investment and other gains 17.7 6.6 12.8 20.4 Total income before income taxes $ 62.2 $ 36.2 $ 134.9 $ 133.3 The table below presents earned premiums by geographic location for the three and nine months ended September 30, 2016 and 2015. 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) 2016 2015 2016 2015 Bermuda $ 29.0 $ 26.8 $ 86.1 $ 76.8 Brazil 10.4 10.3 29.6 34.7 Malta 0.6 0.5 1.6 1.4 United Kingdom 102.4 99.1 301.1 305.5 United States 216.3 209.3 630.1 608.2 Total earned premiums $ 358.7 $ 346.0 $ 1,048.5 $ 1,026.6 The following table represents identifiable assets: September 30, December 31, (in millions) 2016 2015 Excess and Surplus Lines $ 2,266.6 $ 2,174.8 Commercial Specialty 1,652.6 1,511.7 International Specialty 981.6 877.2 Syndicate 1200 1,364.2 1,216.5 Run-off Lines 556.6 558.4 Corporate and Other 359.5 287.0 Total $ 7,181.1 $ 6,625.6 Included in total assets at September 30, 2016 and December 31, 2015 are $576.8 million and $377.1 million, respectively, in assets associated with trade capital providers.

Senior Unsecured Fixed Rate Not

Senior Unsecured Fixed Rate Notes	9 Months Ended
	Sep. 30, 2016
Debt Disclosure [Abstract]
Senior Unsecured Fixed Rate Notes	15. Senior Unsecured Fixed Rate Notes In September 2012, Argo Group (the “Parent Guarantor”), through its subsidiary Argo Group US (the “Subsidiary Issuer”), issued $143,750,000 aggregate principal amount of the Subsidiary Issuer’s 6.5% Senior Notes due September 15, 2042 (the “Notes”). The Notes are unsecured and unsubordinated obligations of the Subsidiary Issuer and rank equally in right of payment with all of the Subsidiary Issuer’s other unsecured and unsubordinated debt. The Notes are guaranteed on a full and unconditional senior unsecured basis by the Parent Guarantor. The Notes may be redeemed, for cash, in whole or in part, on or after September 15, 2017, at the Subsidiary Issuer’s option, at any time and from time to time, prior to maturity at a redemption price equal to 100% of the principal amount of the Notes to be redeemed, plus accrued but unpaid interest on the principal amount being redeemed to, but not including, the redemption date. In accordance with ASU 2015-03, “Simplifying the Presentation of Debt Issuance Costs” (Topic 835), we present the unamortized debt issuance costs in the balance sheet as a direct deduction from the carrying value of the debt liability. At September 30, 2016 and December 31, 2015, the Notes consisted of the following: (in millions) September 30, 2016 December 31, 2015 Senior unsecured fixed rate notes Principal $ 143.8 $ 143.8 Less: unamortized debt issuance costs (4.4 ) (4.5 ) Senior unsecured fixed rate notes, less unamortized debt issuance costs $ 139.4 $ 139.3 In accordance with Article 10 of SEC Regulation S-X, we have elected to present condensed consolidating financial information in lieu of separate financial statements for the Subsidiary Issuer. The following tables present condensed consolidating financial information at September 30, 2016 and December 31, 2015 and for the three and nine months ended September 30, 2016 and 2015, of the Parent Guarantor and 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, 2016 (in millions) (Unaudited) 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 $ 2.6 $ 2,871.2 $ 1,439.8 $ — $ 4,313.6 Cash — 89.3 34.3 — 123.6 Accrued investment income — 16.3 5.6 — 21.9 Premiums receivable — 213.2 290.2 — 503.4 Reinsurance recoverables — 1,300.9 (17.8 ) — 1,283.1 Goodwill and other intangible assets, net — 127.6 93.5 — 221.1 Deferred acquisition costs, net — 64.7 83.0 — 147.7 Ceded unearned premiums — 162.2 149.4 — 311.6 Other assets 9.4 160.0 85.7 — 255.1 Intercompany note receivable — 50.2 (50.2 ) — — Investments in subsidiaries 1,862.1 — — (1,862.1 ) — Total assets $ 1,874.1 $ 5,055.6 $ 2,113.5 $ (1,862.1 ) $ 7,181.1 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — 2,292.7 992.1 $ — $ 3,284.8 Unearned premiums — 582.7 427.5 — 1,010.2 Funds held and ceded reinsurance payable, net — 733.7 (215.2 ) — 518.5 Long-term debt 28.4 284.3 56.7 — 369.4 Current income taxes payable, net — 8.8 (1.1 ) — 7.7 Deferred tax liabilities, net — 25.0 15.7 — 40.7 Accrued underwriting expenses and other liabilities 13.2 109.9 38.3 — 161.4 Due to (from) affiliates 44.1 0.2 (0.2 ) (44.1 ) — Total liabilities 85.7 4,037.3 1,313.8 (44.1 ) 5,392.7 Total shareholders' equity 1,788.4 1,018.3 799.7 (1,818.0 ) 1,788.4 Total liabilities and shareholders' equity $ 1,874.1 $ 5,055.6 $ 2,113.5 $ (1,862.1 ) $ 7,181.1 (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, 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 $ 6.2 $ 2,761.0 $ 1,348.5 $ — $ 4,115.7 Cash — 88.8 32.9 — 121.7 Accrued investment income — 16.4 5.2 — 21.6 Premiums receivable — 166.4 238.1 — 404.5 Reinsurance recoverables — 1,212.2 (91.1 ) — 1,121.1 Goodwill and other intangible assets, net — 129.8 95.7 — 225.5 Current income taxes receivable, net — 4.7 6.9 — 11.6 Deferred acquisition costs, net — 58.2 74.2 — 132.4 Ceded unearned premiums — 125.8 125.0 — 250.8 Other assets 8.2 151.7 60.8 — 220.7 Intercompany note receivable — 49.8 (49.8 ) — — Investments in subsidiaries 1,715.9 — — (1,715.9 ) — Total assets $ 1,730.3 $ 4,764.8 $ 1,846.4 $ (1,715.9 ) $ 6,625.6 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — $ 2,194.1 $ 929.5 $ — $ 3,123.6 Unearned premiums — 501.5 385.2 — 886.7 Funds held and ceded reinsurance payable, net — 702.6 (312.6 ) — 390.0 Long-term debt 28.4 284.2 54.6 — 367.2 Deferred tax liabilities, net — 11.9 11.7 — 23.6 Accrued underwriting expenses and other liabilities 16.3 95.4 54.7 — 166.4 Due to (from) affiliates 17.5 2.3 (2.3 ) (17.5 ) — Total liabilities 62.2 3,792.0 1,120.8 (17.5 ) 4,957.5 Total shareholders' equity 1,668.1 972.8 725.6 (1,698.4 ) 1,668.1 Total liabilities and shareholders' equity $ 1,730.3 $ 4,764.8 $ 1,846.4 $ (1,715.9 ) $ 6,625.6 (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, 2016 (in millions) (Unaudited) 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 $ — $ 128.0 $ 230.7 $ — $ 358.7 Net investment income (expense) (0.9 ) 22.5 11.1 — 32.7 Fee and other income — 5.5 2.1 — 7.6 Net realized investment and other (losses) gains — 19.4 (1.7 ) — 17.7 Total revenue (0.9 ) 175.4 242.2 — 416.7 Expenses: Losses and loss adjustment expenses — 83.5 124.3 — 207.8 Underwriting, acquisition and insurance expenses 3.7 54.0 79.7 — 137.4 Interest expense 0.3 4.0 0.6 — 4.9 Fee and other expense — 5.5 0.4 — 5.9 Foreign currency exchange loss (gain) — 0.2 (1.7 ) — (1.5 ) Total expenses 4.0 147.2 203.3 — 354.5 Income (loss) before income taxes (4.9 ) 28.2 38.9 — 62.2 Provision for income taxes — 6.8 0.2 — 7.0 Net income (loss) before equity in earnings of subsidiaries (4.9 ) 21.4 38.7 — 55.2 Equity in undistributed earnings of subsidiaries 60.1 — — (60.1 ) — Net income $ 55.2 $ 21.4 $ 38.7 $ (60.1 ) $ 55.2 (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 INCOME FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2015 (in millions) (Unaudited) 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 (expense) (0.2 ) 11.2 7.6 (0.2 ) 18.4 Fee and other income — 7.6 1.6 — 9.2 Net realized investment and other gains — 4.3 2.3 — 6.6 Total revenue (0.2 ) 145.2 235.4 (0.2 ) 380.2 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 Fee and other expense — 7.6 0.6 — 8.2 Foreign currency exchange loss (gain) — 0.1 (1.9 ) — (1.8 ) Total expenses 5.4 134.9 203.9 (0.2 ) 344.0 Income (loss) before income taxes (5.6 ) 10.3 31.5 — 36.2 Provision for income taxes — 2.1 (1.2 ) — 0.9 Net income (loss) 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 NINE MONTHS ENDED SEPTEMBER 30, 2016 (in millions) (Unaudited) 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 $ — $ 368.1 $ 680.4 $ — $ 1,048.5 Net investment income (expense) (2.0 ) 62.6 29.0 — 89.6 Fee and other income — 14.9 5.3 — 20.2 Net realized investment and other gains (losses) gains 0.2 32.5 (19.9 ) — 12.8 Total revenue (1.8 ) 478.1 694.8 — 1,171.1 Expenses: Losses and loss adjustment expenses — 220.9 375.1 — 596.0 Underwriting, acquisition and insurance expenses 10.0 150.6 242.4 — 403.0 Interest expense 1.0 11.8 1.8 — 14.6 Fee and other expense — 16.7 1.4 — 18.1 Foreign currency exchange loss — 0.1 4.4 — 4.5 Total expenses 11.0 400.1 625.1 — 1,036.2 Income (loss) before income taxes (12.8 ) 78.0 69.7 — 134.9 Provision for income taxes — 20.5 0.6 — 21.1 Net income (loss) before equity in earnings of subsidiaries (12.8 ) 57.5 69.1 — 113.8 Equity in undistributed earnings of subsidiaries 126.6 — — (126.6 ) — Net income $ 113.8 $ 57.5 $ 69.1 $ (126.6 ) $ 113.8 (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 (expense) (0.7 ) 47.2 22.2 (0.2 ) 68.5 Fee and other income — 14.0 3.9 — 17.9 Net realized investment and other gains gains 2.0 20.1 0.3 (2.0 ) 20.4 Total revenue 1.3 457.3 677.0 (2.2 ) 1,133.4 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 Fee and other expense — 16.4 1.6 — 18.0 Foreign currency exchange loss (gain) — 1.0 (9.4 ) — (8.4 ) Total expenses 15.6 398.3 586.4 (0.2 ) 1,000.1 Income (loss) 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 (loss) 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 CASH FLOWS FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2016 (in millions) (Unaudited) 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 $ 19.6 $ 60.6 $ 70.5 $ — $ 150.7 Cash flows from investing activities: Proceeds from sales of investments — 762.4 246.8 — 1,009.2 Maturities and mandatory calls of fixed maturity investments — 419.7 419.3 — 839.0 Purchases of investments — (1,134.6 ) (721.1 ) — (1,855.7 ) Change in short-term investments and foreign regulatory deposits (0.4 ) (70.5 ) (3.0 ) — (73.9 ) Settlements of foreign currency exchange forward contracts — — (7.2 ) — (7.2 ) Purchases of fixed assets and other, net — 8.1 (2.9 ) — 5.2 Cash used in investing activities (0.4 ) (14.9 ) (68.1 ) — (83.4 ) Cash flows from financing activities: Activity under stock incentive plans 0.6 — — — 0.6 Repurchase of Company's common shares — (45.3 ) — — (45.3 ) Excess tax expense from share-based payment arrangements — 0.1 — — 0.1 Payment of cash dividend to common shareholders (19.8 ) — — — (19.8 ) Cash used in financing activities (19.2 ) (45.2 ) — — (64.4 ) Effect of exchange rate changes on cash — — (1.0 ) — (1.0 ) Change in cash — 0.5 1.4 — 1.9 Cash, beginning of the period — 88.8 32.9 — 121.7 Cash, end of period $ — $ 89.3 $ 34.3 $ — $ 123.6 (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) (Unaudited) 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 $ 12.6 $ 130.6 $ 92.6 $ — $ 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 0.2 (7.3 ) 2.5 — (4.6 ) Cash provided by (used in) investing activities 3.0 (66.0 ) (113.0 ) — (176.0 ) Cash flows from financing activities: Activity under stock incentive plans 1.5 — — — 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 in financing activities (15.6 ) (29.1 ) — — (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 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.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Basis of Presentation	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, 2015, filed with the Securities and Exchange Commission on February 26, 2016. The interim financial information as of, and for the three and nine months ended, September 30, 2016 and 2015 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. During the first quarter of 2016, we evaluated our accounting for income from our alternative investment portfolio and determined that as we manage these investments to appreciate in value on a quarter to quarter basis, it is more appropriate to classify the change in value as net investment income as opposed to realized investment gains (losses). As a result, net investment income for the three and nine months ended September 30, 2016 includes $9.9 million and $20.8 million, respectively, related to the appreciation of our alternative investment portfolio. Net investment income and net realized and other gains for the three and nine months ended September 30, 2015 have been reclassified to reflect the current presentation. Specifically, net investment income for the three and nine months ended September 30, 2015 includes a decrease of $2.9 million and an increase of $4.6 million, respectively, related to the alternative investment portfolio, and net realized investment and other gains were increased for the three months ended September 30, 2015 and decreased for the nine months ended September 30, 2015 by these same amounts. 10% Stock Dividend On May 3, 2016, our Board of Directors declared a 10% stock dividend, payable on June 15, 2016, to shareholders of record at the close of business on June 1, 2016. As a result of the stock dividend, 2,735,542 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 Pr23

Recently Issued Accounting Pronouncements (Tables)	9 Months Ended
	Sep. 30, 2016
Accounting Changes And Error Corrections [Abstract]
Effects of Retrospective Application of Guidance on Individual Financial Statement Line Items	The effects of the retrospective application of this guidance on individual financial statement line items in our Consolidated Balance Sheets were as follows: December 31, 2015 (in millions) As Previously Reported As Adjusted Effect of Change Other assets $ 225.2 $ 220.7 $ (4.5 ) Senior unsecured fixed rate notes 143.8 139.3 (4.5 ) The effects of the retrospective application of this guidance on individual financial statement line items in our Consolidated Statements of Cash Flows were as follows: For the Nine Months Ended September 30, 2015 (in millions) As Previously Reported As Adjusted Effect of Change Cash flows from operating activities: Amortization of debt issuance costs $ — $ 0.1 $ 0.1 Other, net $ (0.1 ) $ (0.2 ) $ (0.1 )

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2016
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, 2016 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities USD denominated: U.S. Governments $ 216.4 $ 1.8 $ 0.2 $ 218.0 Non-U.S. Governments 92.7 0.8 — 93.5 Obligations of states and political subdivisions 387.0 20.8 0.1 407.7 Credit-Financial 494.3 11.4 0.5 505.2 Credit-Industrial 627.5 16.1 2.5 641.1 Credit-Utility 150.0 6.2 1.8 154.4 Structured securities: CMO/MBS-agency (1) 162.9 5.3 0.1 168.1 CMO/MBS-non agency 5.6 0.5 — 6.1 CMBS (2) 203.6 2.0 0.2 205.4 ABS (3) 122.5 0.5 0.2 122.8 CLO (4) 150.6 1.0 0.4 151.2 Foreign denominated: Governments 165.7 1.8 9.8 157.7 Credit 123.1 1.5 13.3 111.3 ABS/CMBS 18.1 — 2.8 15.3 CLO 88.8 2.8 4.8 86.8 Total fixed maturities 3,008.8 72.5 36.7 3,044.6 Equity securities 345.6 115.4 7.3 453.7 Other investments 518.7 7.5 0.1 526.1 Short-term investments 289.2 — — 289.2 Total investments $ 4,162.3 $ 195.4 $ 44.1 $ 4,313.6 (1) Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”). (2) Commercial mortgage-backed securities (“CMBS”). (3) Asset-backed securities (“ABS”). (4) December 31, 2015 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities USD denominated: U.S. Governments $ 207.9 $ 0.7 $ 0.7 $ 207.9 Non-U.S. Governments 93.0 0.1 1.3 91.8 Obligations of states and political subdivisions 467.6 20.7 0.3 488.0 Credit-Financial 502.3 6.2 2.6 505.9 Credit-Industrial 555.8 5.3 12.4 548.7 Credit-Utility 168.1 1.0 13.6 155.5 Structured securities: CMO/MBS-agency (1) 126.5 5.0 0.5 131.0 CMO/MBS-non agency 6.7 0.6 — 7.3 CMBS (2) 186.5 0.5 1.6 185.4 ABS (3) 111.0 0.2 0.7 110.5 CLO (4) 137.5 0.1 1.7 135.9 Foreign denominated: Governments 168.8 0.8 19.3 150.3 Credit 130.2 1.1 20.4 110.9 ABS/CMBS 19.7 0.1 2.2 17.6 CLO 89.4 0.7 9.5 80.6 Total fixed maturities 2,971.0 43.1 86.8 2,927.3 Equity securities 349.7 131.5 17.3 463.9 Other investments 506.9 6.9 0.1 513.7 Short-term investments 211.2 — 0.4 210.8 Total investments $ 4,038.8 $ 181.5 $ 104.6 $ 4,115.7 (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, 2016, by contractual maturity, were as follows: (in millions) Amortized Cost Fair Value Due in one year or less $ 270.6 $ 264.4 Due after one year through five years 1,317.4 1,329.7 Due after five years through ten years 503.7 520.4 Thereafter 165.0 174.4 Structured securities 752.1 755.7 Total $ 3,008.8 $ 3,044.6
Schedule Of Carrying Value Redemption Characteristics And Unfunded Investment Commitments Of Other Invested Assets Portfolio	Details regarding the carrying value and unfunded investment commitments of the other invested assets portfolio as of September 30, 2016 and December 31, 2015 were as follows: September 30, 2016 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 179.5 $ — Private equity 175.7 99.1 Long only funds 164.5 — Other investments 6.4 — Total other invested assets $ 526.1 $ 99.1 December 31, 2015 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 146.9 $ — Private equity 144.1 90.2 Long only funds 211.0 — Other investments 11.7 — Total other invested assets $ 513.7 $ 90.2
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, 2016 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) $ 57.2 $ 0.2 $ — $ — $ 57.2 $ 0.2 Non-U.S. Governments (1) (2) 19.7 — 0.3 — 20.0 — Obligations of states and political subdivisions 18.4 0.1 1.9 — 20.3 0.1 Credit-Financial 64.9 0.3 12.5 0.2 77.4 0.5 Credit-Industrial 54.2 1.3 34.3 1.2 88.5 2.5 Credit-Utility 7.2 0.1 12.6 1.7 19.8 1.8 Structured securities: CMO/MBS-agency (2) 38.8 0.1 4.5 — 43.3 0.1 CMO/MBS-non agency — — — — — — CMBS (2) 45.4 0.2 10.8 — 56.2 0.2 ABS (1) 15.2 — 5.0 0.2 20.2 0.2 CLO 15.1 0.1 44.5 0.3 59.6 0.4 Foreign denominated: Governments 107.9 9.8 — — 107.9 9.8 Credit 90.1 13.2 0.5 0.1 90.6 13.3 ABS/CMBS 13.1 2.3 1.9 0.5 15.0 2.8 CLO 51.9 4.2 6.9 0.6 58.8 4.8 Total fixed maturities 599.1 31.9 135.7 4.8 734.8 36.7 Equity securities 85.5 7.3 — — 85.5 7.3 Other investments 0.3 0.1 — — 0.3 0.1 Short-term investments (1) 3.0 — — — 3.0 — Total $ 687.9 $ 39.3 $ 135.7 $ 4.8 $ 823.6 $ 44.1 (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, 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) $ 138.3 $ 0.7 $ 0.4 $ — $ 138.7 $ 0.7 Non-U.S. Governments 80.2 1.2 2.2 0.1 82.4 1.3 Obligations of states and political subdivisions (1) 9.4 — 8.8 0.3 18.2 0.3 Credit-Financial 283.9 2.2 28.7 0.4 312.6 2.6 Credit-Industrial 343.9 10.3 31.0 2.1 374.9 12.4 Credit-Utility 112.8 8.6 17.6 5.0 130.4 13.6 Structured securities: CMO/MBS-agency 26.9 0.2 8.4 0.3 35.3 0.5 CMO/MBS-non agency (1) 3.8 — — — 3.8 — CMBS (2) 129.5 1.6 3.0 — 132.5 1.6 ABS 91.5 0.4 6.8 0.3 98.3 0.7 CLO 103.8 1.4 12.5 0.3 116.3 1.7 Foreign denominated: Governments 136.4 19.2 0.3 0.1 136.7 19.3 Credit 105.1 20.3 0.5 0.1 105.6 20.4 ABS/CMBS (2) 16.7 2.2 0.1 — 16.8 2.2 CLO 79.5 9.3 0.5 0.2 80.0 9.5 Total fixed maturities 1,661.7 77.6 120.8 9.2 1,782.5 86.8 Equity securities 112.4 17.3 — — 112.4 17.3 Other investments 0.3 0.1 — — 0.3 0.1 Short-term investments 5.8 0.4 — — 5.8 0.4 Total $ 1,780.2 $ 95.4 $ 120.8 $ 9.2 $ 1,901.0 $ 104.6 (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.
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) 2016 2015 2016 2015 Realized gains Fixed maturities $ 5.4 $ 2.9 $ 16.4 $ 10.5 Equity securities 20.8 9.8 45.4 22.6 Other investments 4.2 8.7 31.2 27.6 Short-term investments — — 0.4 1.1 Other assets 1.2 — 1.2 — Gain on sale of real estate holdings — — — 0.4 Gross realized investment gains 31.6 21.4 94.6 62.2 Realized losses Fixed maturities (6.1 ) (4.1 ) (21.0 ) (13.1 ) Equity securities (1.9 ) (2.5 ) (9.0 ) (3.6 ) Other investments (3.5 ) (4.6 ) (42.7 ) (18.2 ) Short-term investments — (0.1 ) (0.1 ) (1.5 ) Other assets — (0.1 ) — (0.1 ) Other-than-temporary impairment losses on fixed maturities (0.6 ) — (1.7 ) (0.9 ) Other-than-temporary impairment losses on equity securities (1.8 ) (3.4 ) (7.3 ) (4.4 ) Gross realized investment and other losses (13.9 ) (14.8 ) (81.8 ) (41.8 ) Net realized investment and other (losses) gains $ 17.7 $ 6.6 $ 12.8 $ 20.4
Schedule of Realized Gains (Losses) and Changes in Unrealized Appreciation (Depreciation)	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 Investments Real Estate Holdings and Other Assets Tax Effects Total Three Months Ended September 30, 2016 Realized before impairments $ (0.7 ) $ 18.9 $ 0.7 $ — $ 1.2 $ (7.1 ) $ 13.0 Realized - impairments (0.6 ) (1.8 ) — — — 0.6 (1.8 ) Change in unrealized 13.7 (10.8 ) — (0.1 ) — 0.3 3.1 Three Months Ended September 30, 2015 Realized before impairments $ (1.2 ) $ 7.3 $ 4.1 $ (0.1 ) $ (0.1 ) $ (3.2 ) $ 6.8 Realized - impairments — (3.4 ) — — — 1.2 (2.2 ) Change in unrealized (22.6 ) (46.7 ) — (0.2 ) — 20.1 (49.4 ) Nine Months Ended September 30, 2016 Realized before impairments $ (4.6 ) $ 36.4 $ (11.5 ) $ 0.3 $ 1.2 $ (10.6 ) $ 11.2 Realized - impairments (1.7 ) (7.3 ) — — — 2.9 (6.1 ) Change in unrealized 78.5 (6.8 ) 0.6 0.3 — (15.7 ) 56.9 Nine Months Ended September 30, 2015 Realized before impairments $ (2.6 ) $ 19.0 $ 9.4 $ (0.4 ) $ 0.3 $ (9.6 ) $ 16.1 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 )
Schedule of Fair Value of Foreign Currency Exchange Forward Contracts	The fair value of our foreign currency exchange forward contracts as of September 30, 2016 and December 31, 2015 was as follows: September 30, December 31, (in millions) 2016 2015 Canadian dollar (CAD) currency exposure $ 1.3 $ 5.2 Euro (EUR) investment exposure (0.4 ) 2.9 Total return strategy 0.6 (0.8 ) $ 1.5 $ 7.3
Schedule of Realized Gains and Losses of Investment on Foreign Currency Exchange Forward Contracts	The following table represents our gross investment realized gains and losses on our foreign currency exchange forward contracts: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2016 2015 2016 2015 Realized gains Global catastrophe (1) $ — $ — $ — $ 0.5 Canadian dollar (CAD) currency exposure 1.3 5.3 8.7 16.5 Euro (EUR) investment exposure — — 2.2 6.3 Investment portfolio return strategy — 3.3 0.3 3.7 Total return strategy 2.2 — 18.2 — Gross realized investment gains 3.5 8.6 29.4 27.0 Realized losses Global catastrophe (1) — (0.2 ) — (2.3 ) Canadian dollar (CAD) currency exposure (0.8 ) (0.4 ) (16.3 ) (5.2 ) Euro (EUR) investment exposure (0.8 ) — (4.5 ) (2.3 ) Investment portfolio return strategy — (3.3 ) (0.2 ) (4.2 ) Total return strategy (1.6 ) — (19.9 ) — Gross realized investment losses (3.2 ) (3.9 ) (40.9 ) (14.0 ) Net realized investment gains (losses) on foreign currency exchange forward contracts $ 0.3 $ 4.7 $ (11.5 ) $ 13.0 (1)
Financial Assets Measured at Fair Value on Recurring Basis	Based on an analysis of the inputs, our financial assets measured at fair value on a recurring basis have been categorized as follows: Fair (in millions) September 30, 2016 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities USD denominated: U.S. Governments $ 218.0 $ 174.3 $ 43.7 $ — Non-U.S. Governments 93.5 — 93.5 — Obligations of states and political subdivisions 407.7 — 407.7 — Credit-Financial 505.2 — 503.2 2.0 Credit-Industrial 641.1 — 641.1 — Credit-Utility 154.4 — 154.4 — Structured securities: CMO/MBS-agency 168.1 — 168.1 — CMO/MBS-non agency 6.1 — 6.1 — CMBS 205.4 — 205.4 — ABS 122.8 — 122.8 — CLO 151.2 — 151.2 — Foreign denominated: — — — Governments 157.7 — 157.7 — Credit 111.3 — 111.3 — ABS/CMBS 15.3 — 15.3 — CLO 86.8 — 86.8 — Total fixed maturities 3,044.6 174.3 2,868.3 2.0 Equity securities 453.7 451.2 2.1 0.4 Other fair value investments 86.8 — 86.8 — Short-term investments 289.2 275.0 14.2 — $ 3,874.3 $ 900.5 $ 2,971.4 $ 2.4 (a) Quoted prices in active markets for identical assets (b) Significant other observable inputs (c) Significant unobservable inputs Fair Value Measurements at Reporting Date Using (in millions) December 31, 2015 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities USD denominated: U.S. Governments $ 207.9 $ 150.4 $ 57.5 $ — Non-U.S. Governments 91.8 — 91.8 — Obligations of states and political subdivisions 488.0 — 488.0 — Credit-Financial 505.9 — 505.9 — Credit-Industrial 548.7 — 548.7 — Credit-Utility 155.5 — 155.5 — Structured securities: CMO/MBS-agency 131.0 — 131.0 — CMO/MBS-non agency 7.3 — 7.3 — CMBS 185.4 — 185.4 — ABS 110.5 — 110.5 — CLO 135.9 — 135.9 — Foreign denominated: Governments 150.3 — 150.3 — Credit 110.9 — 110.9 — ABS/CMBS 17.6 — 17.6 — CLO 80.6 — 80.6 — Total fixed maturities 2,927.3 150.4 2,776.9 — Equity securities 463.9 457.6 5.6 0.7 Other fair value investments 97.2 — 97.2 — Short-term investments 210.8 203.6 7.2 — $ 3,699.2 $ 811.6 $ 2,886.9 $ 0.7 (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) Credit Financial Equity Securities Total Beginning balance, January 1, 2016 $ — $ 0.7 $ 0.7 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 2.0 — 2.0 Issuances — — — Sales — (0.3 ) (0.3 ) Settlements — — — Ending balance, September 30, 2016 $ 2.0 $ 0.4 $ 2.4 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, 2016 $ — $ — $ — (in millions) Credit Financial 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 — (0.2 ) (0.2 ) Settlements — — — Ending balance, December 31, 2015 $ — $ 0.7 $ 0.7 Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2015 $ — $ — $ —

Reserves for Losses and Loss 25

Reserves for Losses and Loss Adjustment Expenses (Tables)	9 Months Ended
	Sep. 30, 2016
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) 2016 2015 Net reserves beginning of the year $ 2,133.3 $ 2,137.1 Add: Losses and LAE incurred during current calendar year, net of reinsurance: Current accident year 614.8 589.6 Prior accident years (18.8 ) (15.3 ) Losses and LAE incurred during calendar year, net of reinsurance 596.0 574.3 Deduct: Losses and LAE payments made during current calendar year, net of reinsurance: Current accident year 115.3 105.2 Prior accident years 403.9 435.5 Losses and LAE payments made during current calendar year, net of reinsurance: 519.2 540.7 Change in participation interest (1) (36.3 ) (1.2 ) Foreign exchange adjustments 1.0 (27.7 ) Net reserves - end of period 2,174.8 2,141.8 Add: Reinsurance recoverables on unpaid losses and LAE, end of period 1,110.0 962.3 Gross reserves - end of period $ 3,284.8 $ 3,104.1 (1) Amount represents decreases in reserves due to change in syndicate participation
Impact from (Favorable) Unfavorable Development of Prior Accident Years’ Loss and LAE Reserves on Each Reporting Segment	The impact from the (favorable) unfavorable development of prior accident years’ loss and LAE reserves on each reporting segment is presented below: For the Nine Months Ended September 30, (in millions) 2016 2015 Excess and Surplus Lines $ (12.0 ) $ (18.4 ) Commercial Specialty (13.6 ) 3.7 International Specialty (8.3 ) (5.8 ) Syndicate 1200 (2.5 ) (2.8 ) Run-off Lines 17.6 8.0 Total favorable prior-year development $ (18.8 ) $ (15.3 )

Disclosures about Fair Value 26

Disclosures about Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2016
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, 2016 December 31, 2015 (in millions) Carrying Amount Fair Value Carrying Amount Fair Value Junior subordinated debentures $ 172.7 $ 172.7 $ 172.7 $ 166.5 Senior unsecured fixed rate notes 139.4 144.4 139.3 141.8 Other indebtedness: Floating rate loan stock 56.7 56.7 54.6 52.7 Note payable 0.6 0.6 0.6 0.6 $ 369.4 $ 374.4 $ 367.2 $ 361.6

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Schedule of Repurchase of Shares	A summary of common shares repurchased for the nine months ended September 30, 2016 is shown below: Repurchase Type Date Trading Plan Initiated 2016 Purchase Period Number of Shares Repurchased Average Price of Shares Repurchased Total Cost (in millions) Repurchase Authorization Year 10b5-1 Trading Plan 12/16/2015 01/04/2016-02/11/2016 266,538 $ 55.59 $ 14.8 2013 10b5-1 Trading Plan 03/16/2016 03/16/2016-05/02/2016 162,893 $ 55.62 9.1 2013 10b5-1 Trading Plan 06/16/2016 06/24/2016-06/28/2016 14,774 $ 49.78 0.7 2016 10b5-1 Trading Plan 09/15/2016 09/19/2016-09/28/2016 11,147 $ 55.38 0.6 2016 Open Market N/A 01/01/2016-05/02/2016 64,464 $ 54.14 3.5 2013 Open Market N/A 05/03/2016-09/30/2016 295,380 $ 56.38 16.6 2016 Total 815,196 $ 55.66 $ 45.3

Accumulated Other Comprehensi28

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2016
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, 2016 and 2015 is presented below: (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance, January 1, 2016 $ (21.6 ) $ 40.0 $ (6.9 ) $ 11.5 Other comprehensive (loss) income before reclassifications 2.8 70.2 — 73.0 Amounts reclassified from accumulated other comprehensive (loss) income — (13.3 ) — (13.3 ) Net current-period other comprehensive (loss) income 2.8 56.9 — 59.7 Balance at September 30, 2016 $ (18.8 ) $ 96.9 $ (6.9 ) $ 71.2 (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) income before reclassifications (6.6 ) (75.7 ) — (82.3 ) Amounts reclassified from accumulated other comprehensive (loss) income — (2.3 ) — (2.3 ) Net current-period other comprehensive (loss) income (6.6 ) (78.0 ) — (84.6 ) Balance at September 30, 2015 $ (22.2 ) $ 52.7 $ (7.0 ) $ 23.5
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	The following table illustrates the amounts reclassified from accumulated other comprehensive income (loss) 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) 2016 2015 2016 2015 Unrealized gains and losses on securities: Net realized investment (gains) losses $ (17.0 ) $ 0.1 $ (25.1 ) $ (6.9 ) Provision for income tax 7.9 1.7 11.8 4.6 Net of taxes $ (9.1 ) $ 1.8 $ (13.3 ) $ (2.3 )

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2016
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: For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions, except number of shares and per share amounts) 2016 2015 2016 2015 Net income $ 55.2 $ 35.3 $ 113.8 $ 122.0 Weighted average common shares outstanding - basic 30,018,637 30,707,233 30,227,725 30,796,390 Effect of dilutive securities: Equity compensation awards 709,746 613,710 661,762 596,702 Weighted average common shares outstanding - diluted 30,728,383 31,320,943 30,889,487 31,393,092 Net income per common share: Basic $ 1.84 $ 1.15 $ 3.76 $ 3.96 Diluted $ 1.80 $ 1.13 $ 3.68 $ 3.89

Supplemental Cash Flow Inform30

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2016
Supplemental Cash Flow Elements [Abstract]
Schedule of Interest Paid	Interest paid was as follows: For the Nine Months Ended September 30, (in millions) 2016 2015 Senior unsecured fixed rate notes $ 7.0 $ 7.0 Junior subordinated debentures 5.7 5.3 Other indebtedness 2.0 2.0 Total interest paid $ 14.7 $ 14.3

Share-based Compensation (Table

Share-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2016
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, 2016 and 2015: For the Nine Months Ended September 30, 2016 2015 Risk-free rate of return 1.12% 1.44% Expected dividend yields 1.65% 1.52% Expected award life (years) 4.50 4.64 Expected volatility 18.73% 20.81%
Summary of Restricted Share Activity	A summary of restricted share activity as of September 30, 2016 and changes during the nine months then ended is as follows: Shares Weighted-Average Grant Date Fair Value Outstanding at January 1, 2016 514,742 $ 36.87 Granted 263,491 $ 50.41 Vested and issued (70,987 ) $ 32.70 Expired or forfeited (13,990 ) $ 44.13 Outstanding at September 30, 2016 693,256 $ 42.29
Summary of Stock-Settled SARs Activity	A summary of stock-settled SARs activity as of September 30, 2016 and changes during the nine months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2016 1,438,146 $ 29.52 Granted 542 $ 36.71 Converted from cash-settled SARs 944,046 $ 41.21 Exercised (173,538 ) $ 25.42 Expired or forfeited (128,701 ) $ 42.03 Outstanding at September 30, 2016 2,080,495 $ 34.39
Summary of Cash-Settled SARs Activity	Cash-Settled SARs A summary of cash-settled SARs activity as of September 30, 2016 and changes during the nine months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2016 2,220,560 $ 35.53 Granted 540 $ 36.71 Converted to stock-settled SARs (1) (864,036 ) $ 41.21 Exercised (565,096 ) $ 31.37 Expired or forfeited (111,709 ) $ 39.23 Outstanding at September 30, 2016 680,259 $ 31.16 (1) The converted shares were not adjusted for the 10% stock dividend because the conversion occurred prior to the stock dividend record date.

Underwriting, Acquisition and32

Underwriting, Acquisition and Insurance Expenses (Tables)	9 Months Ended
	Sep. 30, 2016
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) 2016 2015 2016 2015 Commissions $ 59.3 $ 56.5 $ 178.5 $ 182.4 General expenses 75.6 69.6 217.3 222.2 Premium taxes, boards and bureaus 6.1 7.5 19.0 8.1 141.0 133.6 414.8 412.7 Net deferral of policy acquisition costs (3.6 ) (0.8 ) (11.8 ) (10.8 ) Total underwriting, acquisition and insurance expenses $ 137.4 $ 132.8 $ 403.0 $ 401.9

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2016
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) 2016 2015 2016 2015 Current tax provision $ 10.8 $ (11.3 ) $ 18.8 $ (2.5 ) Deferred tax provision (benefit) related to: Future tax deductions (3.0 ) 14.1 1.9 16.7 Valuation allowance change (0.8 ) (1.9 ) 0.4 (2.9 ) Income tax provision $ 7.0 $ 0.9 $ 21.1 $ 11.3
Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates	For the three and nine months ended September 30, 2016 and 2015, 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) 2016 2015 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 35.6 0.0 % $ 24.6 0.0 % United States 28.2 24.2 % 10.5 19.6 % United Kingdom (2.8 ) -3.0 % 1.9 -58.5 % Belgium — (1) -160.0 % — (1) 31.4 % Brazil 0.4 0.0 % (0.7 ) 0.0 % United Arab Emirates — (1) 0.0 % 0.1 0.0 % Ireland (0.1 ) 0.0 % — (1) 0.0 % Malta 0.9 0.0 % (0.3 ) 0.0 % Switzerland — (1) 21.2 % 0.1 -20.0 % Pre-tax income $ 62.2 $ 36.2 For the Nine Months Ended September 30, (in millions) 2016 2015 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 79.7 0.0 % $ 68.8 0.0 % United States 78.0 26.3 % 59.1 22.4 % United Kingdom (24.9 ) -1.9 % 9.1 -21.4 % Belgium — (1) 0.0 % (0.1 ) -50.5 % Brazil 1.1 0.0 % (3.7 ) 0.0 % United Arab Emirates — (1) 0.0 % 0.2 0.0 % Ireland (0.2 ) 0.0 % (0.1 ) 0.0 % Malta 1.2 0.0 % — (1) 0.0 % Switzerland — (1) 21.1 % — (1) -21.3 % Pre-tax income $ 134.9 $ 133.3 (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) 2016 2015 2016 2015 Income tax provision at expected rate $ 9.8 $ 3.7 $ 23.2 $ 21.1 Tax effect of: Tax-exempt interest (0.7 ) (1.2 ) (2.5 ) (3.1 ) Dividends received deduction (0.4 ) (0.6 ) (1.7 ) (1.8 ) Valuation allowance change (0.8 ) (1.9 ) 0.4 (2.9 ) Other permanent adjustments, net 0.1 0.1 0.3 0.3 Adjustment for prior year tax return (0.8 ) (0.6 ) (0.8 ) (0.6 ) Adjustment for annualized rate (0.9 ) 0.8 (1.5 ) 0.6 United States state tax (benefit) expense — — — (2.5 ) Other foreign adjustments (0.1 ) 0.1 (0.7 ) 0.2 Prior year foreign taxes recovered — — — (1.2 ) Deferred tax rate reduction — — (0.3 ) — Foreign exchange adjustments 0.8 0.5 4.4 0.9 Foreign withholding taxes — — 0.3 0.3 Income tax provision $ 7.0 $ 0.9 $ 21.1 $ 11.3 Income tax provision (benefit) - Foreign $ 0.2 $ (1.2 ) $ 0.6 $ (2.0 ) Income tax provision - United States, Federal 6.8 2.1 20.2 16.8 Income tax benefit - United States, State — — — (3.8 ) Foreign withholding tax - United States — — 0.3 0.3 Income tax provision $ 7.0 $ 0.9 $ 21.1 $ 11.3

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2016
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) 2016 2015 2016 2015 Revenue: Earned premiums Excess and Surplus Lines $ 122.3 $ 121.5 $ 363.4 $ 351.8 Commercial Specialty 94.0 87.5 266.3 255.7 International Specialty 39.9 36.4 117.4 109.8 Syndicate 1200 102.4 100.3 301.1 308.9 Run-off Lines 0.1 0.3 0.3 0.4 Total earned premiums 358.7 346.0 1,048.5 1,026.6 Net investment income Excess and Surplus Lines 12.7 7.2 35.1 24.6 Commercial Specialty 7.6 4.4 20.7 15.1 International Specialty 4.7 2.5 13.0 8.7 Syndicate 1200 2.8 1.9 9.7 6.7 Run-off Lines 3.2 1.7 8.8 6.1 Corporate and Other 1.7 0.7 2.3 7.3 Total net investment income 32.7 18.4 89.6 68.5 Fee and other income 7.6 9.2 20.2 17.9 Net realized investment and other gains 17.7 6.6 12.8 20.4 Total revenue $ 416.7 $ 380.2 $ 1,171.1 $ 1,133.4 For the Three Months Ended September 30, For the Nine Months Ended September 30, (in millions) 2016 2015 2016 2015 Income (loss) before income taxes Excess and Surplus Lines $ 22.8 $ 22.0 $ 69.0 $ 64.1 Commercial Specialty 23.1 15.1 57.2 31.7 International Specialty 15.2 3.1 32.4 21.1 Syndicate 1200 4.9 6.5 20.7 28.0 Run-off Lines (10.0 ) (6.9 ) (14.6 ) (6.6 ) Total segment income before taxes 56.0 39.8 164.7 138.3 Corporate and Other (11.5 ) (10.2 ) (42.6 ) (25.4 ) Net realized investment and other gains 17.7 6.6 12.8 20.4 Total income before income taxes $ 62.2 $ 36.2 $ 134.9 $ 133.3
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, 2016 and 2015. 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) 2016 2015 2016 2015 Bermuda $ 29.0 $ 26.8 $ 86.1 $ 76.8 Brazil 10.4 10.3 29.6 34.7 Malta 0.6 0.5 1.6 1.4 United Kingdom 102.4 99.1 301.1 305.5 United States 216.3 209.3 630.1 608.2 Total earned premiums $ 358.7 $ 346.0 $ 1,048.5 $ 1,026.6
Identifiable Assets	The following table represents identifiable assets: September 30, December 31, (in millions) 2016 2015 Excess and Surplus Lines $ 2,266.6 $ 2,174.8 Commercial Specialty 1,652.6 1,511.7 International Specialty 981.6 877.2 Syndicate 1200 1,364.2 1,216.5 Run-off Lines 556.6 558.4 Corporate and Other 359.5 287.0 Total $ 7,181.1 $ 6,625.6

Senior Unsecured Fixed Rate N35

Senior Unsecured Fixed Rate Notes (Tables)	9 Months Ended
	Sep. 30, 2016
Debt Disclosure [Abstract]
Schedule Of Unamortized Debt Issuance Costs Deducted From Carrying Value Of Debt Liability	At September 30, 2016 and December 31, 2015, the Notes consisted of the following: (in millions) September 30, 2016 December 31, 2015 Senior unsecured fixed rate notes Principal $ 143.8 $ 143.8 Less: unamortized debt issuance costs (4.4 ) (4.5 ) Senior unsecured fixed rate notes, less unamortized debt issuance costs $ 139.4 $ 139.3
Condensed Consolidating Balance Sheet	CONDENSED CONSOLIDATING BALANCE SHEET September 30, 2016 (in millions) (Unaudited) 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 $ 2.6 $ 2,871.2 $ 1,439.8 $ — $ 4,313.6 Cash — 89.3 34.3 — 123.6 Accrued investment income — 16.3 5.6 — 21.9 Premiums receivable — 213.2 290.2 — 503.4 Reinsurance recoverables — 1,300.9 (17.8 ) — 1,283.1 Goodwill and other intangible assets, net — 127.6 93.5 — 221.1 Deferred acquisition costs, net — 64.7 83.0 — 147.7 Ceded unearned premiums — 162.2 149.4 — 311.6 Other assets 9.4 160.0 85.7 — 255.1 Intercompany note receivable — 50.2 (50.2 ) — — Investments in subsidiaries 1,862.1 — — (1,862.1 ) — Total assets $ 1,874.1 $ 5,055.6 $ 2,113.5 $ (1,862.1 ) $ 7,181.1 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — 2,292.7 992.1 $ — $ 3,284.8 Unearned premiums — 582.7 427.5 — 1,010.2 Funds held and ceded reinsurance payable, net — 733.7 (215.2 ) — 518.5 Long-term debt 28.4 284.3 56.7 — 369.4 Current income taxes payable, net — 8.8 (1.1 ) — 7.7 Deferred tax liabilities, net — 25.0 15.7 — 40.7 Accrued underwriting expenses and other liabilities 13.2 109.9 38.3 — 161.4 Due to (from) affiliates 44.1 0.2 (0.2 ) (44.1 ) — Total liabilities 85.7 4,037.3 1,313.8 (44.1 ) 5,392.7 Total shareholders' equity 1,788.4 1,018.3 799.7 (1,818.0 ) 1,788.4 Total liabilities and shareholders' equity $ 1,874.1 $ 5,055.6 $ 2,113.5 $ (1,862.1 ) $ 7,181.1 (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, 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 $ 6.2 $ 2,761.0 $ 1,348.5 $ — $ 4,115.7 Cash — 88.8 32.9 — 121.7 Accrued investment income — 16.4 5.2 — 21.6 Premiums receivable — 166.4 238.1 — 404.5 Reinsurance recoverables — 1,212.2 (91.1 ) — 1,121.1 Goodwill and other intangible assets, net — 129.8 95.7 — 225.5 Current income taxes receivable, net — 4.7 6.9 — 11.6 Deferred acquisition costs, net — 58.2 74.2 — 132.4 Ceded unearned premiums — 125.8 125.0 — 250.8 Other assets 8.2 151.7 60.8 — 220.7 Intercompany note receivable — 49.8 (49.8 ) — — Investments in subsidiaries 1,715.9 — — (1,715.9 ) — Total assets $ 1,730.3 $ 4,764.8 $ 1,846.4 $ (1,715.9 ) $ 6,625.6 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — $ 2,194.1 $ 929.5 $ — $ 3,123.6 Unearned premiums — 501.5 385.2 — 886.7 Funds held and ceded reinsurance payable, net — 702.6 (312.6 ) — 390.0 Long-term debt 28.4 284.2 54.6 — 367.2 Deferred tax liabilities, net — 11.9 11.7 — 23.6 Accrued underwriting expenses and other liabilities 16.3 95.4 54.7 — 166.4 Due to (from) affiliates 17.5 2.3 (2.3 ) (17.5 ) — Total liabilities 62.2 3,792.0 1,120.8 (17.5 ) 4,957.5 Total shareholders' equity 1,668.1 972.8 725.6 (1,698.4 ) 1,668.1 Total liabilities and shareholders' equity $ 1,730.3 $ 4,764.8 $ 1,846.4 $ (1,715.9 ) $ 6,625.6 (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, 2016 (in millions) (Unaudited) 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 $ — $ 128.0 $ 230.7 $ — $ 358.7 Net investment income (expense) (0.9 ) 22.5 11.1 — 32.7 Fee and other income — 5.5 2.1 — 7.6 Net realized investment and other (losses) gains — 19.4 (1.7 ) — 17.7 Total revenue (0.9 ) 175.4 242.2 — 416.7 Expenses: Losses and loss adjustment expenses — 83.5 124.3 — 207.8 Underwriting, acquisition and insurance expenses 3.7 54.0 79.7 — 137.4 Interest expense 0.3 4.0 0.6 — 4.9 Fee and other expense — 5.5 0.4 — 5.9 Foreign currency exchange loss (gain) — 0.2 (1.7 ) — (1.5 ) Total expenses 4.0 147.2 203.3 — 354.5 Income (loss) before income taxes (4.9 ) 28.2 38.9 — 62.2 Provision for income taxes — 6.8 0.2 — 7.0 Net income (loss) before equity in earnings of subsidiaries (4.9 ) 21.4 38.7 — 55.2 Equity in undistributed earnings of subsidiaries 60.1 — — (60.1 ) — Net income $ 55.2 $ 21.4 $ 38.7 $ (60.1 ) $ 55.2 (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 INCOME FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2015 (in millions) (Unaudited) 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 (expense) (0.2 ) 11.2 7.6 (0.2 ) 18.4 Fee and other income — 7.6 1.6 — 9.2 Net realized investment and other gains — 4.3 2.3 — 6.6 Total revenue (0.2 ) 145.2 235.4 (0.2 ) 380.2 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 Fee and other expense — 7.6 0.6 — 8.2 Foreign currency exchange loss (gain) — 0.1 (1.9 ) — (1.8 ) Total expenses 5.4 134.9 203.9 (0.2 ) 344.0 Income (loss) before income taxes (5.6 ) 10.3 31.5 — 36.2 Provision for income taxes — 2.1 (1.2 ) — 0.9 Net income (loss) 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 NINE MONTHS ENDED SEPTEMBER 30, 2016 (in millions) (Unaudited) 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 $ — $ 368.1 $ 680.4 $ — $ 1,048.5 Net investment income (expense) (2.0 ) 62.6 29.0 — 89.6 Fee and other income — 14.9 5.3 — 20.2 Net realized investment and other gains (losses) gains 0.2 32.5 (19.9 ) — 12.8 Total revenue (1.8 ) 478.1 694.8 — 1,171.1 Expenses: Losses and loss adjustment expenses — 220.9 375.1 — 596.0 Underwriting, acquisition and insurance expenses 10.0 150.6 242.4 — 403.0 Interest expense 1.0 11.8 1.8 — 14.6 Fee and other expense — 16.7 1.4 — 18.1 Foreign currency exchange loss — 0.1 4.4 — 4.5 Total expenses 11.0 400.1 625.1 — 1,036.2 Income (loss) before income taxes (12.8 ) 78.0 69.7 — 134.9 Provision for income taxes — 20.5 0.6 — 21.1 Net income (loss) before equity in earnings of subsidiaries (12.8 ) 57.5 69.1 — 113.8 Equity in undistributed earnings of subsidiaries 126.6 — — (126.6 ) — Net income $ 113.8 $ 57.5 $ 69.1 $ (126.6 ) $ 113.8 (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 (expense) (0.7 ) 47.2 22.2 (0.2 ) 68.5 Fee and other income — 14.0 3.9 — 17.9 Net realized investment and other gains gains 2.0 20.1 0.3 (2.0 ) 20.4 Total revenue 1.3 457.3 677.0 (2.2 ) 1,133.4 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 Fee and other expense — 16.4 1.6 — 18.0 Foreign currency exchange loss (gain) — 1.0 (9.4 ) — (8.4 ) Total expenses 15.6 398.3 586.4 (0.2 ) 1,000.1 Income (loss) 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 (loss) 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
Condensed Consolidating Statement of Cash Flows	CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2016 (in millions) (Unaudited) 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 $ 19.6 $ 60.6 $ 70.5 $ — $ 150.7 Cash flows from investing activities: Proceeds from sales of investments — 762.4 246.8 — 1,009.2 Maturities and mandatory calls of fixed maturity investments — 419.7 419.3 — 839.0 Purchases of investments — (1,134.6 ) (721.1 ) — (1,855.7 ) Change in short-term investments and foreign regulatory deposits (0.4 ) (70.5 ) (3.0 ) — (73.9 ) Settlements of foreign currency exchange forward contracts — — (7.2 ) — (7.2 ) Purchases of fixed assets and other, net — 8.1 (2.9 ) — 5.2 Cash used in investing activities (0.4 ) (14.9 ) (68.1 ) — (83.4 ) Cash flows from financing activities: Activity under stock incentive plans 0.6 — — — 0.6 Repurchase of Company's common shares — (45.3 ) — — (45.3 ) Excess tax expense from share-based payment arrangements — 0.1 — — 0.1 Payment of cash dividend to common shareholders (19.8 ) — — — (19.8 ) Cash used in financing activities (19.2 ) (45.2 ) — — (64.4 ) Effect of exchange rate changes on cash — — (1.0 ) — (1.0 ) Change in cash — 0.5 1.4 — 1.9 Cash, beginning of the period — 88.8 32.9 — 121.7 Cash, end of period $ — $ 89.3 $ 34.3 $ — $ 123.6 (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) (Unaudited) 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 $ 12.6 $ 130.6 $ 92.6 $ — $ 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 0.2 (7.3 ) 2.5 — (4.6 ) Cash provided by (used in) investing activities 3.0 (66.0 ) (113.0 ) — (176.0 ) Cash flows from financing activities: Activity under stock incentive plans 1.5 — — — 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 in financing activities (15.6 ) (29.1 ) — — (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 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.

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Detail) - USD ($) $ in Millions	Aug. 02, 2016	May 03, 2016	Aug. 04, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Basis Of Presentation [Line Items]
Stock dividend declared		10.00%
Additional stock issued as dividend		2,735,542
Dividends declaration date	Aug. 2, 2016	May 3, 2016	Aug. 4, 2015
Dividends payable date		Jun. 15, 2016
Dividend payable, date of record	Aug. 15, 2016	Jun. 1, 2016	Sep. 1, 2015
Restatement Of Revenue [Member]
Basis Of Presentation [Line Items]
Increase (decrease) in net investment income				$ 9.9	$ (2.9)	$ 20.8	$ 4.6
Increase (decrease) in net realized investment income and other gains				$ 9.9	$ 2.9	$ 20.8	$ (4.6)

Recently Issued Accounting Pr37

Recently Issued Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Unamortized debt issuance costs related to senior unsecured fixed rate notes	$ 4.4	$ 4.5
Accounting Standards Update 2015-03 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Unamortized debt issuance costs related to senior unsecured fixed rate notes		$ 4.5

Recently Issued Accounting Pr38

Recently Issued Accounting Pronouncements - Effects of Retrospective Application of Guidance on Individual Financial Statement Line Items in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Debt Issuance Cost [Abstract]
Other assets	$ 255.1	$ 220.7	[1]
Senior unsecured fixed rate notes	$ 139.4	139.3	[1]
Other Assets [Member] | Accounting Standards Update 2015-03 [Member] | As Previously Reported [Member]
Debt Issuance Cost [Abstract]
Other assets		225.2
Other Assets [Member] | Accounting Standards Update 2015-03 [Member] | Scenario Adjustment [Member]
Debt Issuance Cost [Abstract]
Other assets		220.7
Other Assets [Member] | Accounting Standards Update 2015-03 [Member] | Restatement Adjustment [Member]
Debt Issuance Cost [Abstract]
Other assets		(4.5)
Senior Notes [Member] | Accounting Standards Update 2015-03 [Member] | As Previously Reported [Member]
Debt Issuance Cost [Abstract]
Senior unsecured fixed rate notes		143.8
Senior Notes [Member] | Accounting Standards Update 2015-03 [Member] | Scenario Adjustment [Member]
Debt Issuance Cost [Abstract]
Senior unsecured fixed rate notes		139.3
Senior Notes [Member] | Accounting Standards Update 2015-03 [Member] | Restatement Adjustment [Member]
Debt Issuance Cost [Abstract]
Senior unsecured fixed rate notes		$ (4.5)
[1]	Derived from audited consolidated financial statements.

Recently Issued Accounting Pr39

Recently Issued Accounting Pronouncements - Effects of Retrospective Application of Guidance on Individual Financial Statement Line Items in Consolidated Statement of Cash Flows (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Amortization of debt issuance costs	$ (0.1)	$ (0.1)
Other, net	$ (35.1)	(0.2)
Accounting Standards Update 2015-03 [Member] | As Previously Reported [Member]
Cash flows from operating activities:
Amortization of debt issuance costs		0
Other, net		(0.1)
Accounting Standards Update 2015-03 [Member] | Scenario Adjustment [Member]
Cash flows from operating activities:
Amortization of debt issuance costs		0.1
Other, net		(0.2)
Accounting Standards Update 2015-03 [Member] | Restatement Adjustment [Member]
Cash flows from operating activities:
Amortization of debt issuance costs		0.1
Other, net		$ (0.1)

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, 2016	Dec. 31, 2015
Schedule of Invested Assets [Line Items]
Total investments		$ 4,313.6	$ 4,115.7	[1]
Fixed Maturities [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		3,008.8	2,971
Investments Gross Unrealized Gains		72.5	43.1
Investments Gross Unrealized losses		36.7	86.8
Total investments		3,044.6	2,927.3
Fixed Maturities [Member] | CLO [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost	[2]	150.6	137.5
Investments Gross Unrealized Gains	[2]	1	0.1
Investments Gross Unrealized losses	[2]	0.4	1.7
Total investments	[2]	151.2	135.9
Fixed Maturities [Member] | U.S. Governments [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		216.4	207.9
Investments Gross Unrealized Gains		1.8	0.7
Investments Gross Unrealized losses		0.2	0.7
Total investments		218	207.9
Fixed Maturities [Member] | Non-U.S. Governments [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		92.7	93
Investments Gross Unrealized Gains		0.8	0.1
Investments Gross Unrealized losses		0	1.3
Total investments		93.5	91.8
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		387	467.6
Investments Gross Unrealized Gains		20.8	20.7
Investments Gross Unrealized losses		0.1	0.3
Total investments		407.7	488
Fixed Maturities [Member] | Credit-Financial [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		494.3	502.3
Investments Gross Unrealized Gains		11.4	6.2
Investments Gross Unrealized losses		0.5	2.6
Total investments		505.2	505.9
Fixed Maturities [Member] | Credit-Industrial [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		627.5	555.8
Investments Gross Unrealized Gains		16.1	5.3
Investments Gross Unrealized losses		2.5	12.4
Total investments		641.1	548.7
Fixed Maturities [Member] | Credit-Utility [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		150	168.1
Investments Gross Unrealized Gains		6.2	1
Investments Gross Unrealized losses		1.8	13.6
Total investments		154.4	155.5
Fixed Maturities [Member] | CMO/MBS-Agency [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost	[3]	162.9	126.5
Investments Gross Unrealized Gains	[3]	5.3	5
Investments Gross Unrealized losses	[3]	0.1	0.5
Total investments	[3]	168.1	131
Fixed Maturities [Member] | CMO/MBS-Non Agency [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		5.6	6.7
Investments Gross Unrealized Gains		0.5	0.6
Investments Gross Unrealized losses		0	0
Total investments		6.1	7.3
Fixed Maturities [Member] | CMBS [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost	[4]	203.6	186.5
Investments Gross Unrealized Gains	[4]	2	0.5
Investments Gross Unrealized losses	[4]	0.2	1.6
Total investments	[4]	205.4	185.4
Fixed Maturities [Member] | ABS [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost	[5]	122.5	111
Investments Gross Unrealized Gains	[5]	0.5	0.2
Investments Gross Unrealized losses	[5]	0.2	0.7
Total investments	[5]	122.8	110.5
Fixed Maturities [Member] | Foreign Denominated: Governments [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		165.7	168.8
Investments Gross Unrealized Gains		1.8	0.8
Investments Gross Unrealized losses		9.8	19.3
Total investments		157.7	150.3
Fixed Maturities [Member] | Foreign Denominated: Credit [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		123.1	130.2
Investments Gross Unrealized Gains		1.5	1.1
Investments Gross Unrealized losses		13.3	20.4
Total investments		111.3	110.9
Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		18.1	19.7
Investments Gross Unrealized Gains		0	0.1
Investments Gross Unrealized losses		2.8	2.2
Total investments		15.3	17.6
Fixed Maturities [Member] | Foreign denominated: CLO [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		88.8	89.4
Investments Gross Unrealized Gains		2.8	0.7
Investments Gross Unrealized losses		4.8	9.5
Total investments		86.8	80.6
Equity Securities [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		345.6	349.7
Investments Gross Unrealized Gains		115.4	131.5
Investments Gross Unrealized losses		7.3	17.3
Total investments		453.7	463.9
Other Investments [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		518.7	506.9
Investments Gross Unrealized Gains		7.5	6.9
Investments Gross Unrealized losses		0.1	0.1
Total investments		526.1	513.7
Short-Term Investments [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		289.2	211.2
Investments Gross Unrealized Gains		0	0
Investments Gross Unrealized losses		0	0.4
Total investments		289.2	210.8
Securities and Non Securities Investment [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost		4,162.3	4,038.8
Investments Gross Unrealized Gains		195.4	181.5
Investments Gross Unrealized losses		44.1	104.6
Total investments		$ 4,313.6	$ 4,115.7
[1]	Derived from audited consolidated financial statements.
[2]	Collateralized loan obligations (“CLO”).
[3]	Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”).
[4]	Commercial mortgage-backed securities (“CMBS”).
[5]	Asset-backed securities (“ABS”).

Investments - Additional Inform

Investments - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2016USD ($)Security	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)Security	Sep. 30, 2015USD ($)	Dec. 31, 2015USD ($)
Schedule Of Investments [Line Items]
Fair value of investments, assets managed on behalf of the trade capital providers	$ 127,500,000		$ 127,500,000		$ 95,300,000
Number of securities in an unrealized loss position, total | Security	7,203		7,203
Number of securities in an unrealized loss position for less than one year | Security	1,331		1,331
Number of securities in an unrealized loss position for a period of one year or greater | Security	264		264
Other-than-temporary losses	$ 1,800,000	$ 3,400,000	$ 7,300,000	$ 4,400,000
Total investments	4,313,600,000		4,313,600,000		4,115,700,000	[1]
Reported loss expense reserve	28,100,000		28,100,000		29,300,000
Securities pledged to Lloyd's	195,100,000		195,100,000		202,500,000
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	39,500,000		39,500,000		34,900,000
Pledged assets separately reported, securities pledged under letters of credit facilities, at fair value	39,300,000		39,300,000		35,000,000
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Other-than-temporary losses	600,000	0	1,700,000	900,000
Total investments	3,044,600,000		3,044,600,000		2,927,300,000
Equity Securities [Member]
Schedule Of Investments [Line Items]
Other-than-temporary losses	1,800,000	$ 3,400,000	7,300,000	$ 4,400,000
Total investments	453,700,000		453,700,000		463,900,000
Deposit with Various U.S. Canadian Insurance and Other Agencies [Member] | United States [Member]
Schedule Of Investments [Line Items]
Amortized Cost	164,400,000		164,400,000		187,100,000
Total investments	$ 172,700,000		$ 172,700,000		$ 192,800,000
[1]	Derived from audited consolidated financial statements.

Investments - Schedule of Amo42

Investments - Schedule of Amortized Cost and Fair Values of Fixed Maturity Investments, by Contractual Maturity (Detail) $ in Millions	Sep. 30, 2016USD ($)
Investments Debt And Equity Securities [Abstract]
Amortized Cost, Due in one year or less	$ 270.6
Amortized Cost, Due after one year through five years	1,317.4
Amortized Cost, Due after five years through ten years	503.7
Amortized Cost, Thereafter	165
Amortized Cost, Structured securities	752.1
Amortized Cost, Total	3,008.8
Fair Value, Due in one year or less	264.4
Fair Value, Due after one year through five years	1,329.7
Fair Value, Due after five years through ten years	520.4
Fair Value, Thereafter	174.4
Fair Value, Structured securities	755.7
Fair Value, Total	$ 3,044.6

Investments - Schedule of Carry

Investments - Schedule of Carrying Value and Unfunded Investment Commitments of Other Invested Assets Portfolio (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Schedule Of Investments [Line Items]
Carrying Value	$ 4,313.6	$ 4,115.7	[1]
Hedge funds [Member]
Schedule Of Investments [Line Items]
Carrying Value	179.5	146.9
Unfunded Commitments	0	0
Private equity [Member]
Schedule Of Investments [Line Items]
Carrying Value	175.7	144.1
Unfunded Commitments	99.1	90.2
Long only funds [Member]
Schedule Of Investments [Line Items]
Carrying Value	164.5	211
Unfunded Commitments	0	0
Other Investments [Member]
Schedule Of Investments [Line Items]
Carrying Value	6.4	11.7
Unfunded Commitments	0	0
Other Investments [Member]
Schedule Of Investments [Line Items]
Carrying Value	526.1	513.7
Unfunded Commitments	$ 99.1	$ 90.2
[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, 2016		Dec. 31, 2015
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		$ 687.9		$ 1,780.2
Unrealized Losses, Less Than One Year		39.3		95.4
Fair Value, One Year or Greater		135.7		120.8
Unrealized Losses, One Year or Greater		4.8		9.2
Fair Value, Total		823.6		1,901
Unrealized Losses, Total		44.1		104.6
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		599.1		1,661.7
Unrealized Losses, Less Than One Year		31.9		77.6
Fair Value, One Year or Greater		135.7		120.8
Unrealized Losses, One Year or Greater		4.8		9.2
Fair Value, Total		734.8		1,782.5
Unrealized Losses, Total		36.7		86.8
Fixed Maturities [Member] | CLO [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		15.1		103.8
Unrealized Losses, Less Than One Year		0.1		1.4
Fair Value, One Year or Greater		44.5		12.5
Unrealized Losses, One Year or Greater		0.3		0.3
Fair Value, Total		59.6		116.3
Unrealized Losses, Total		0.4		1.7
Fixed Maturities [Member] | U.S. Governments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year	[1]	57.2		138.3
Unrealized Losses, Less Than One Year	[1]	0.2		0.7
Fair Value, One Year or Greater	[1]	0		0.4
Unrealized Losses, One Year or Greater	[1]	0		0
Fair Value, Total	[1]	57.2		138.7
Unrealized Losses, Total	[1]	0.2		0.7
Fixed Maturities [Member] | Non-U.S. Governments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		19.7	[1],[2]	80.2
Unrealized Losses, Less Than One Year		0	[1],[2]	1.2
Fair Value, One Year or Greater		0.3	[1],[2]	2.2
Unrealized Losses, One Year or Greater		0	[1],[2]	0.1
Fair Value, Total		20	[1],[2]	82.4
Unrealized Losses, Total		0	[1],[2]	1.3
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		18.4		9.4	[2]
Unrealized Losses, Less Than One Year		0.1		0	[2]
Fair Value, One Year or Greater		1.9		8.8	[2]
Unrealized Losses, One Year or Greater		0		0.3	[2]
Fair Value, Total		20.3		18.2	[2]
Unrealized Losses, Total		0.1		0.3	[2]
Fixed Maturities [Member] | Credit-Financial [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		64.9		283.9
Unrealized Losses, Less Than One Year		0.3		2.2
Fair Value, One Year or Greater		12.5		28.7
Unrealized Losses, One Year or Greater		0.2		0.4
Fair Value, Total		77.4		312.6
Unrealized Losses, Total		0.5		2.6
Fixed Maturities [Member] | Credit-Industrial [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		54.2		343.9
Unrealized Losses, Less Than One Year		1.3		10.3
Fair Value, One Year or Greater		34.3		31
Unrealized Losses, One Year or Greater		1.2		2.1
Fair Value, Total		88.5		374.9
Unrealized Losses, Total		2.5		12.4
Fixed Maturities [Member] | Credit-Utility [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		7.2		112.8
Unrealized Losses, Less Than One Year		0.1		8.6
Fair Value, One Year or Greater		12.6		17.6
Unrealized Losses, One Year or Greater		1.7		5
Fair Value, Total		19.8		130.4
Unrealized Losses, Total		1.8		13.6
Fixed Maturities [Member] | CMO/MBS-Agency [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		38.8	[1]	26.9
Unrealized Losses, Less Than One Year		0.1	[1]	0.2
Fair Value, One Year or Greater		4.5	[1]	8.4
Unrealized Losses, One Year or Greater		0	[1]	0.3
Fair Value, Total		43.3	[1]	35.3
Unrealized Losses, Total		0.1	[1]	0.5
Fixed Maturities [Member] | CMO/MBS-Non Agency [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		0		3.8	[2]
Unrealized Losses, Less Than One Year		0		0	[2]
Fair Value, One Year or Greater		0		0	[2]
Unrealized Losses, One Year or Greater		0		0	[2]
Fair Value, Total		0		3.8	[2]
Unrealized Losses, Total		0		0	[2]
Fixed Maturities [Member] | CMBS [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year	[1]	45.4		129.5
Unrealized Losses, Less Than One Year	[1]	0.2		1.6
Fair Value, One Year or Greater	[1]	10.8		3
Unrealized Losses, One Year or Greater	[1]	0		0
Fair Value, Total	[1]	56.2		132.5
Unrealized Losses, Total	[1]	0.2		1.6
Fixed Maturities [Member] | ABS [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		15.2	[2]	91.5
Unrealized Losses, Less Than One Year		0	[2]	0.4
Fair Value, One Year or Greater		5	[2]	6.8
Unrealized Losses, One Year or Greater		0.2	[2]	0.3
Fair Value, Total		20.2	[2]	98.3
Unrealized Losses, Total		0.2	[2]	0.7
Fixed Maturities [Member] | Foreign Denominated: Governments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		107.9		136.4
Unrealized Losses, Less Than One Year		9.8		19.2
Fair Value, One Year or Greater		0		0.3
Unrealized Losses, One Year or Greater		0		0.1
Fair Value, Total		107.9		136.7
Unrealized Losses, Total		9.8		19.3
Fixed Maturities [Member] | Foreign Denominated: Credit [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		90.1		105.1
Unrealized Losses, Less Than One Year		13.2		20.3
Fair Value, One Year or Greater		0.5		0.5
Unrealized Losses, One Year or Greater		0.1		0.1
Fair Value, Total		90.6		105.6
Unrealized Losses, Total		13.3		20.4
Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		13.1		16.7	[1]
Unrealized Losses, Less Than One Year		2.3		2.2	[1]
Fair Value, One Year or Greater		1.9		0.1	[1]
Unrealized Losses, One Year or Greater		0.5		0	[1]
Fair Value, Total		15		16.8	[1]
Unrealized Losses, Total		2.8		2.2	[1]
Fixed Maturities [Member] | Foreign denominated: CLO [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		51.9		79.5
Unrealized Losses, Less Than One Year		4.2		9.3
Fair Value, One Year or Greater		6.9		0.5
Unrealized Losses, One Year or Greater		0.6		0.2
Fair Value, Total		58.8		80
Unrealized Losses, Total		4.8		9.5
Equity Securities [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		85.5		112.4
Unrealized Losses, Less Than One Year		7.3		17.3
Fair Value, One Year or Greater		0		0
Unrealized Losses, One Year or Greater		0		0
Fair Value, Total		85.5		112.4
Unrealized Losses, Total		7.3		17.3
Other Investments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		0.3		0.3
Unrealized Losses, Less Than One Year		0.1		0.1
Fair Value, One Year or Greater		0		0
Unrealized Losses, One Year or Greater		0		0
Fair Value, Total		0.3		0.3
Unrealized Losses, Total		0.1		0.1
Short-Term Investments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		3	[2]	5.8
Unrealized Losses, Less Than One Year		0	[2]	0.4
Fair Value, One Year or Greater		0	[2]	0
Unrealized Losses, One Year or Greater		0	[2]	0
Fair Value, Total		3	[2]	5.8
Unrealized Losses, Total		$ 0	[2]	$ 0.4
[1]	Unrealized losses one year or greater are less than $0.1 million.
[2]	Unrealized losses less than one year are less than $0.1 million.

Investments - Schedule of Agi45

Investments - Schedule of Aging of Unrealized Losses on Company's Investments in Fixed Maturities, Equity Securities and Other Investments (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Unrealized losses less than one year	$ 0.1	$ 0.1
Unrealized losses one year or greater	$ 0.1	$ 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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Investments [Line Items]
Gross realized investment gains and other	$ 31.6	$ 21.4	$ 94.6	$ 62.2
Gross realized investment and other losses	(13.9)	(14.8)	(81.8)	(41.8)
Net realized investment and other (losses) gains	17.7	6.6	12.8	20.4
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	5.4	2.9	16.4	10.5
Gross realized investment and other losses	(6.1)	(4.1)	(21)	(13.1)
Equity Securities [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	20.8	9.8	45.4	22.6
Gross realized investment and other losses	(1.9)	(2.5)	(9)	(3.6)
Other Investments [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	4.2	8.7	31.2	27.6
Gross realized investment and other losses	(3.5)	(4.6)	(42.7)	(18.2)
Short-Term Investments [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	0	0	0.4	1.1
Gross realized investment and other losses	0	(0.1)	(0.1)	(1.5)
Other Assets [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	1.2	0	1.2	0
Gross realized investment and other losses	0	(0.1)	0	(0.1)
Real Estate Holdings [Member]
Schedule Of Investments [Line Items]
Gross realized investment gains and other	0	0	0	0.4
Other-Than-Temporary Impairment Losses on Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other losses	(0.6)	0	(1.7)	(0.9)
Other-Than-Temporary Impairment Losses on Equity Securities [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other losses	$ (1.8)	$ (3.4)	$ (7.3)	$ (4.4)

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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Investments [Line Items]
Realized before impairments	$ 13	$ 6.8	$ 11.2	$ 16.1
Realized - impairments	(1.8)	(2.2)	(6.1)	(3.5)
Change in unrealized	3.1	(49.4)	56.9	(77.8)
Realized before impairments, Tax Effects	(7.1)	(3.2)	(10.6)	(9.6)
Realized - impairments, Tax Effects	0.6	1.2	2.9	1.8
Change in unrealized, Tax Effects	0.3	20.1	(15.7)	33.3
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Realized before impairments	(0.7)	(1.2)	(4.6)	(2.6)
Realized - impairments	(0.6)	0	(1.7)	(0.9)
Change in unrealized	13.7	(22.6)	78.5	(40.9)
Equity Securities [Member]
Schedule Of Investments [Line Items]
Realized before impairments	18.9	7.3	36.4	19
Realized - impairments	(1.8)	(3.4)	(7.3)	(4.4)
Change in unrealized	(10.8)	(46.7)	(6.8)	(71.5)
Other Investments [Member]
Schedule Of Investments [Line Items]
Realized before impairments	0.7	4.1	(11.5)	9.4
Realized - impairments	0	0	0	0
Change in unrealized	0	0	0.6	1.5
Short-Term Investments [Member]
Schedule Of Investments [Line Items]
Realized before impairments	0	(0.1)	0.3	(0.4)
Realized - impairments	0	0	0	0
Change in unrealized	(0.1)	(0.2)	0.3	(0.2)
Real Estate Holdings and Other Assets [Member]
Schedule Of Investments [Line Items]
Realized before impairments	1.2	(0.1)	1.2	0.3
Realized - impairments	0	0	0	0
Change in unrealized	$ 0	$ 0	$ 0	$ 0

Investments - Schedule of Fair

Investments - Schedule of Fair Value of Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts [Member] - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Schedule Of Investments [Line Items]
Fair value of foreign currency exchange forward contracts	$ 1.5	$ 7.3
Currency Exposure [Member] | Canadian Dollar (CAD) [Member]
Schedule Of Investments [Line Items]
Fair value of foreign currency exchange forward contracts	1.3	5.2
Investment Exposure [Member] | Euro (EUR) [Member]
Schedule Of Investments [Line Items]
Fair value of foreign currency exchange forward contracts	(0.4)	2.9
Total return strategy [Member]
Schedule Of Investments [Line Items]
Fair value of foreign currency exchange forward contracts	$ 0.6	$ (0.8)

Investments - Schedule of Rea49

Investments - Schedule of Realized Gains and Losses of Investment on Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts [Member] - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts		$ 3.5	$ 8.6	$ 29.4	$ 27
Realized losses from foreign currency exchange forward contracts		(3.2)	(3.9)	(40.9)	(14)
Net realized investment gains (losses) on foreign currency exchange forward contracts		0.3	4.7	(11.5)	13
Global Catastrophe [Member]
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts	[1]	0	0	0	0.5
Realized losses from foreign currency exchange forward contracts	[1]	0	(0.2)	0	(2.3)
Currency Exposure [Member] | Canadian Dollar (CAD) [Member]
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts		1.3	5.3	8.7	16.5
Realized losses from foreign currency exchange forward contracts		(0.8)	(0.4)	(16.3)	(5.2)
Investment Exposure [Member] | Euro (EUR) [Member]
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts		0	0	2.2	6.3
Realized losses from foreign currency exchange forward contracts		(0.8)	0	(4.5)	(2.3)
Investment Portfolio Return Strategy [Member]
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts		0	3.3	0.3	3.7
Realized losses from foreign currency exchange forward contracts		0	(3.3)	(0.2)	(4.2)
Total return strategy [Member]
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts		2.2	0	18.2	0
Realized losses from foreign currency exchange forward contracts		$ (1.6)	$ 0	$ (19.9)	$ 0
[1]	Global Catastrophe program ended 2015

Investments - Financial Assets

Investments - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		$ 4,313.6	$ 4,115.7	[1]
Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		3,044.6	2,927.3
Fixed Maturities [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	151.2	135.9
Fixed Maturities [Member] | U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		218	207.9
Fixed Maturities [Member] | Non-U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		93.5	91.8
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		407.7	488
Fixed Maturities [Member] | Credit-Financial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		505.2	505.9
Fixed Maturities [Member] | Credit-Industrial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		641.1	548.7
Fixed Maturities [Member] | Credit-Utility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		154.4	155.5
Fixed Maturities [Member] | CMO/MBS-Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	168.1	131
Fixed Maturities [Member] | CMO/MBS-Non Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		6.1	7.3
Fixed Maturities [Member] | CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	205.4	185.4
Fixed Maturities [Member] | ABS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[5]	122.8	110.5
Fixed Maturities [Member] | Foreign Denominated: Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		157.7	150.3
Fixed Maturities [Member] | Foreign Denominated: Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		111.3	110.9
Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		15.3	17.6
Fixed Maturities [Member] | Foreign denominated: CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		86.8	80.6
Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		453.7	463.9
Other fair value investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		526.1	513.7
Short-Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		289.2	210.8
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		3,874.3	3,699.2
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]
Total investments	[6]	900.5	811.6
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	2,971.4	2,886.9
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	2.4	0.7
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		3,044.6	2,927.3
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		151.2	135.9
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	174.3	150.4
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	2,868.3	2,776.9
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Other Observable Inputs (Level 2) [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	151.2	135.9
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	2	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Unobservable Inputs (Level 3) [Member] | CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		218	207.9
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | U.S. Governments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	174.3	150.4
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | U.S. Governments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	43.7	57.5
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | U.S. Governments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Non-U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		93.5	91.8
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Non-U.S. Governments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Non-U.S. Governments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	93.5	91.8
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Non-U.S. Governments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		407.7	488
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	407.7	488
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Financial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		505.2	505.9
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Financial [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Financial [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	503.2	505.9
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Financial [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	2	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Industrial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		641.1	548.7
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Industrial [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Industrial [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	641.1	548.7
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Industrial [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Utility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		154.4	155.5
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Utility [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Utility [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	154.4	155.5
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Credit-Utility [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMO/MBS-Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		168.1	131
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMO/MBS-Agency [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMO/MBS-Agency [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	168.1	131
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMO/MBS-Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMO/MBS-Non Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		6.1	7.3
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMO/MBS-Non Agency [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMO/MBS-Non Agency [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	6.1	7.3
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMO/MBS-Non Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		205.4	185.4
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMBS [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMBS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	205.4	185.4
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | CMBS [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | ABS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		122.8	110.5
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | ABS [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | ABS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	122.8	110.5
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | ABS [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Denominated: Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		157.7	150.3
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Denominated: Governments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Denominated: Governments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	157.7	150.3
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Denominated: Governments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Denominated: Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		111.3	110.9
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Denominated: Credit [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Denominated: Credit [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	111.3	110.9
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Denominated: Credit [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		15.3	17.6
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	15.3	17.6
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign denominated: ABS/CMBS [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign denominated: CLO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		86.8	80.6
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign denominated: CLO [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign denominated: CLO [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	86.8	80.6
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign denominated: CLO [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		453.7	463.9
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	451.2	457.6
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	2.1	5.6
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0.4	0.7
Fair Value, Measurements, Recurring [Member] | Other fair value investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		86.8	97.2
Fair Value, Measurements, Recurring [Member] | Other fair value investments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	0	0
Fair Value, Measurements, Recurring [Member] | Other fair value investments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	86.8	97.2
Fair Value, Measurements, Recurring [Member] | Other fair value investments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	0	0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		289.2	210.8
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[6]	275	203.6
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[7]	14.2	7.2
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[8]	$ 0	$ 0
[1]	Derived from audited consolidated financial statements.
[2]	Collateralized loan obligations (“CLO”).
[3]	Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”).
[4]	Commercial mortgage-backed securities (“CMBS”).
[5]	Asset-backed securities (“ABS”).
[6]	Quoted prices in active markets for identical assets
[7]	Significant other observable inputs
[8]	Significant unobservable inputs

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, 2016	Dec. 31, 2015
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 0.7	$ 0.9
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
Purchases	2	0
Issuances	0	0
Sales	(0.3)	(0.2)
Settlements	0	0
Ending balance	2.4	0.7
Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at end of period	0	0
Credit-Financial [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	0	0
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
Purchases	2	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Ending balance	2	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	0
Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	0.7	0.9
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
Purchases	0	0
Issuances	0	0
Sales	(0.3)	(0.2)
Settlements	0	0
Ending balance	0.4	0.7
Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at end of period	$ 0	$ 0

Reserves for Losses and Loss 52

Reserves for Losses and Loss Adjustment Expenses - Reinsurance Recoverables (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	[2]
Liability for Claims and Claims Adjustment Expense [Abstract]
Net reserves beginning of the year				$ 2,133.3	$ 2,137.1
Losses and LAE incurred during current calendar year, net of reinsurance:
Current accident year				614.8	589.6
Prior accident years				(18.8)	(15.3)
Losses and LAE incurred during calendar year, net of reinsurance		$ 207.8	$ 200	596	574.3
Current accident year				115.3	105.2
Prior accident years				403.9	435.5
Losses and LAE payments made during current calendar year, net of reinsurance:				519.2	540.7
Change in participation interest	[1]			(36.3)	(1.2)
Foreign exchange adjustments				1	(27.7)
Net reserves - end of period		2,174.8	2,141.8	2,174.8	2,141.8
Reinsurance recoverables on unpaid losses and LAE, end of period		(1,110)	(962.3)	(1,110)	(962.3)
Reserves for losses and loss adjustment expenses		$ 3,284.8	$ 3,104.1	$ 3,284.8	$ 3,104.1	$ 3,123.6
[1]	Amount represents decreases in reserves due to change in syndicate participation
[2]	Derived from audited consolidated financial statements.

Reserves for Losses and Loss 53

Reserves for Losses and Loss Adjustment Expenses - Impact from (Favorable) Unfavorable Development of Prior Accident Years' Loss and LAE Reserves on Each Reporting Segment (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total favorable prior-year development	$ (18.8)	$ (15.3)
Excess and Surplus Lines [Member]
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total favorable prior-year development	(12)	(18.4)
Commercial Specialty [Member]
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total favorable prior-year development	(13.6)	3.7
International Specialty [Member]
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total favorable prior-year development	(8.3)	(5.8)
Syndicate 1200 [Member]
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total favorable prior-year development	(2.5)	(2.8)
Run Off Lines [Member]
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total favorable prior-year development	$ 17.6	$ 8

Disclosures about Fair Value 54

Disclosures about Fair Value of Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Financial Instruments Owned and Pledged as Collateral [Line Items]
Premiums receivable	$ 503.4	$ 404.5	[1]
Reinsurance recoverables	1,283.1	1,121.1	[1]
Premiums receivable, allowance for doubtful accounts	2.6	3.5
Over 90 Days [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Premiums receivable	13.3	10
Reinsurance recoverables	10.2	7.1
Reinsurance recoverables, allowance for doubtful accounts	1.8	2.2
Premiums receivables, secured by collateral	0.5	0.2
Reinsurance recoverables, secured by collateral	$ 0.6	$ 0.7
[1]	Derived from audited consolidated financial statements.

Disclosures about Fair Value 55

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, 2016	Dec. 31, 2015
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	$ 369.4	$ 367.2
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	374.4	361.6
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	172.7	166.5
Senior Unsecured Fixed Rate Notes [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	139.4	139.3
Senior Unsecured Fixed Rate Notes [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	144.4	141.8
Other Indebtedness [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	56.7	54.6
Other Indebtedness [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	56.7	52.7
Other Indebtedness [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	0.6	0.6
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 ($)	Aug. 29, 2016	Aug. 02, 2016	May 03, 2016	Sep. 15, 2015	Aug. 04, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Class Of Stock [Line Items]
Stock dividend declared			10.00%
Dividends declaration date		Aug. 2, 2016	May 3, 2016		Aug. 4, 2015
Additional stock issued as dividend			2,735,542
Dividends payable date			Jun. 15, 2016
Dividend payable, date of record		Aug. 15, 2016	Jun. 1, 2016		Sep. 1, 2015
Dividend declared per common share		$ 0.22			$ 0.18	$ 0.22	$ 0.18	$ 0.64	$ 0.55
Cash dividends paid - common shares, total	$ 6,700,000			$ 5,600,000
Common shares repurchased on open market								815,196
2016 Repurchase Authorization [Member]
Class Of Stock [Line Items]
Total number of shares authorized for purchase, Value			$ 150,000,000			$ 132,000,000		$ 132,000,000
Common shares repurchased on open market								815,196
Common shares repurchased on open market, total cost								$ 45,300,000

Shareholders Equity - Schedule

Shareholders Equity - Schedule of Repurchase of Shares (Detail) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2016USD ($)$ / sharesshares
Equity Class Of Treasury Stock [Line Items]
Common shares repurchased on open market | shares	815,196
Average Price of Shares Repurchased | $ / shares	$ 55.66
Total Cost (in millions) | $	$ 45.3
10b5-1 Trading Plan Initiated In 12/16/2015 [Member]
Equity Class Of Treasury Stock [Line Items]
Date Trading Plan Initiated	Dec. 16, 2015
Trading Plan Purchase Period Start Date	Jan. 4, 2016
Common shares repurchased on open market | shares	266,538
Average Price of Shares Repurchased | $ / shares	$ 55.59
Total Cost (in millions) | $	$ 14.8
Repurchase Authorization Year	2,013
Trading Plan Purchase Period End Date	Feb. 11, 2016
10b5-1 Trading Plan Initiated In 03/16/2016 [Member]
Equity Class Of Treasury Stock [Line Items]
Date Trading Plan Initiated	Mar. 16, 2016
Trading Plan Purchase Period Start Date	Mar. 16, 2016
Common shares repurchased on open market | shares	162,893
Average Price of Shares Repurchased | $ / shares	$ 55.62
Total Cost (in millions) | $	$ 9.1
Repurchase Authorization Year	2,013
Trading Plan Purchase Period End Date	May 2, 2016
10b5-1 Trading Plan Initiated In 06/14/2016 [Member]
Equity Class Of Treasury Stock [Line Items]
Date Trading Plan Initiated	Jun. 16, 2016
Trading Plan Purchase Period Start Date	Jun. 24, 2016
Common shares repurchased on open market | shares	14,774
Average Price of Shares Repurchased | $ / shares	$ 49.78
Total Cost (in millions) | $	$ 0.7
Repurchase Authorization Year	2,016
Trading Plan Purchase Period End Date	Jun. 28, 2016
Open Market Repurchase Authorization Two Thousand And Sixteen [Member]
Equity Class Of Treasury Stock [Line Items]
Trading Plan Purchase Period Start Date	May 3, 2016
Common shares repurchased on open market | shares	295,380
Average Price of Shares Repurchased | $ / shares	$ 56.38
Total Cost (in millions) | $	$ 16.6
Repurchase Authorization Year	2,016
Trading Plan Purchase Period End Date	Sep. 30, 2016
10b5-1 Trading Plan Initiated In 09/15/2016 [Member]
Equity Class Of Treasury Stock [Line Items]
Date Trading Plan Initiated	Sep. 15, 2016
Trading Plan Purchase Period Start Date	Sep. 19, 2016
Common shares repurchased on open market | shares	11,147
Average Price of Shares Repurchased | $ / shares	$ 55.38
Total Cost (in millions) | $	$ 0.6
Repurchase Authorization Year	2,016
Trading Plan Purchase Period End Date	Sep. 28, 2016
Open Market Repurchase Authorization Two Thousand And Thirteen [Member]
Equity Class Of Treasury Stock [Line Items]
Trading Plan Purchase Period Start Date	Jan. 1, 2016
Common shares repurchased on open market | shares	64,464
Average Price of Shares Repurchased | $ / shares	$ 54.14
Total Cost (in millions) | $	$ 3.5
Repurchase Authorization Year	2,013
Trading Plan Purchase Period End Date	May 2, 2016

Accumulated Other Comprehensi58

Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016		Sep. 30, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			$ 11.5	[1]	$ 108.1
Other comprehensive (loss) income before reclassifications			73		(82.3)
Amounts reclassified from accumulated other comprehensive (loss) income			(13.3)		(2.3)
Other comprehensive income (loss), net of tax	$ 2.1	$ (53.6)	59.7		(84.6)
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	71.2	23.5	71.2		23.5
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			(21.6)		(15.6)
Other comprehensive (loss) income before reclassifications			2.8		(6.6)
Amounts reclassified from accumulated other comprehensive (loss) income			0		0
Other comprehensive income (loss), net of tax			2.8		(6.6)
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	(18.8)	(22.2)	(18.8)		(22.2)
Unrealized Holding Gains on Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			40		130.7
Other comprehensive (loss) income before reclassifications			70.2		(75.7)
Amounts reclassified from accumulated other comprehensive (loss) income			(13.3)		(2.3)
Other comprehensive income (loss), net of tax			56.9		(78)
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	96.9	52.7	96.9		52.7
Defined Benefit Pension Plans
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			(6.9)		(7)
Other comprehensive (loss) income before reclassifications			0		0
Amounts reclassified from accumulated other comprehensive (loss) income			0		0
Other comprehensive income (loss), net of tax			0		0
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	$ (6.9)	$ (7)	$ (6.9)		$ (7)
[1]	Derived from audited consolidated financial statements.

Accumulated Other Comprehensi59

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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Unrealized gains and losses on securities:
Net realized investment (gains) losses	$ (17)	$ 0.1	$ (25.1)	$ (6.9)
Provision for income tax	7.9	1.7	11.8	4.6
Net of taxes			(13.3)	(2.3)
Unrealized Holding Gains on Securities
Unrealized gains and losses on securities:
Net of taxes			(13.3)	(2.3)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Holding Gains on Securities
Unrealized gains and losses on securities:
Net realized investment (gains) losses	(17)	0.1	(25.1)	(6.9)
Provision for income tax	7.9	1.7	11.8	4.6
Net of taxes	$ (9.1)	$ 1.8	$ (13.3)	$ (2.3)

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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 55.2	$ 35.3	$ 113.8	$ 122
Weighted average common shares outstanding - basic	30,018,637	30,707,233	30,227,725	30,796,390
Effect of dilutive securities:
Equity compensation awards	709,746	613,710	661,762	596,702
Weighted average common shares outstanding - diluted	30,728,383	31,320,943	30,889,487	31,393,092
Net income per common share - basic	$ 1.84	$ 1.15	$ 3.76	$ 3.96
Net income per common share - diluted	$ 1.80	$ 1.13	$ 3.68	$ 3.89

Net Income Per Common Share - A

Net Income Per Common Share - Additional Information (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	[1]
Earnings Per Share [Abstract]
Treasury shares, shares	9,996,840	9,181,544	9,996,840	9,181,544	9,181,644
Antidilutive securities excluded from computation of diluted net income per share, shares	0	0	0	0
[1]	Derived from audited consolidated financial statements.

Supplemental Cash Flow Inform62

Supplemental Cash Flow Information - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Income Taxes Paid Net [Abstract]
Income taxes paid	$ 1.5	$ 10.8
Income taxes recovered	$ 0.5	$ 11.5

Supplemental Cash Flow Inform63

Supplemental Cash Flow Information - Schedule of Interest Paid (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Supplemental Cash Flow [Line Items]
Total interest paid	$ 14.7	$ 14.3
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	5.7	5.3
Other Indebtedness [Member]
Supplemental Cash Flow [Line Items]
Total interest paid	$ 2	$ 2

Share-based Compensation - Addi

Share-based Compensation - Additional Information (Detail)	Aug. 02, 2016	May 03, 2016	Aug. 04, 2015	Sep. 30, 2016	Sep. 30, 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%
Dividends declaration date	Aug. 2, 2016	May 3, 2016	Aug. 4, 2015
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, 2016	Sep. 30, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free rate of return	1.12%	1.44%
Expected dividend yields	1.65%	1.52%
Expected award life (years)	4 years 6 months	4 years 7 months 21 days
Expected volatility	18.73%	20.81%

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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	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		$ 1.7	$ 1.4	$ 5.2	$ 4.4
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		19.9		$ 19.9
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		1	0.3	$ 3.6	1.3
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		9.4		$ 9.4
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		2.6	$ 2.8	$ 2.1	$ 14.1
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		$ 0.5		$ 0.5
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, 2016$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2016 | shares	514,742
Granted, Shares | shares	263,491
Vested and issued, Shares | shares	(70,987)
Expired or forfeited, Shares | shares	(13,990)
Shares, Outstanding at September 30, 2016 | shares	693,256
Weighted-Average Grant Date Fair Value, Outstanding at January 1, 2016 | $ / shares	$ 36.87
Granted, Weighted-Average Grant Date Fair Value | $ / shares	50.41
Vested and issued, Weighted-Average Grant Date Fair Value | $ / shares	32.70
Expired or forfeited, Weighted-Average Grant Date Fair Value | $ / shares	44.13
Weighted-Average Grant Date Fair Value, Outstanding at September 30, 2016 | $ / shares	$ 42.29

Share-based Compensation - Su68

Share-based Compensation - Summary of Stock-Settled SARs Activity (Detail) - Stock-Settled SARs Activity [Member]	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2016 | shares	1,438,146
Granted, Shares | shares	542
Converted from cash-settled SARs | shares	944,046
Exercised, Shares | shares	(173,538)
Expired or forfeited, Shares | shares	(128,701)
Shares, Outstanding at September 30, 2016 | shares	2,080,495
Weighted-Average Exercise Price, Outstanding at January 1, 2016 | $ / shares	$ 29.52
Granted, Weighted-Average Exercise Price | $ / shares	36.71
Converted from cash-settled SARs | $ / shares	41.21
Exercised, Weighted-Average Exercise Price | $ / shares	25.42
Expired or forfeited, Weighted-Average Exercise Price | $ / shares	42.03
Weighted-Average Exercise Price, Outstanding at September 30, 2016 | $ / shares	$ 34.39

Share-based Compensation - Su69

Share-based Compensation - Summary of Cash-Settled SARs Activity (Detail) - Cash-Settled SARs Activity [Member]	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2016 | shares	2,220,560
Granted, Shares | shares	540
Converted to stock-settled SARs | shares	(864,036)	[1]
Exercised, Shares | shares	(565,096)
Expired or forfeited, Shares | shares	(111,709)
Shares, Outstanding at September 30, 2016 | shares	680,259
Weighted-Average Exercise Price, Outstanding at January 1, 2016 | $ / shares	$ 35.53
Granted, Weighted-Average Exercise Price | $ / shares	36.71
Converted to stock-settled SARs | $ / shares	41.21	[1]
Exercised, Weighted-Average Exercise Price | $ / shares	31.37
Expired or forfeited, Weighted-Average Exercise Price | $ / shares	39.23
Weighted-Average Exercise Price, Outstanding at September 30, 2016 | $ / shares	$ 31.16
[1]	The converted shares were not adjusted for the 10% stock dividend because the conversion occurred prior to the stock dividend record date.

Underwriting, Acquisition and70

Underwriting, Acquisition and Insurance Expenses - Underwriting, Acquisition and Insurance Expenses (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Underwriting Acquisition And Insurance Expenses [Abstract]
Commissions	$ 59.3	$ 56.5	$ 178.5	$ 182.4
General expenses	75.6	69.6	217.3	222.2
Premium taxes, boards and bureaus	6.1	7.5	19	8.1
Underwriting, acquisition and insurance expenses, total	141	133.6	414.8	412.7
Net deferral of policy acquisition costs	(3.6)	(0.8)	(11.8)	(10.8)
Total underwriting, acquisition and insurance expenses	$ 137.4	$ 132.8	$ 403	$ 401.9

Underwriting, Acquisition and71

Underwriting, Acquisition and Insurance Expenses - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Underwriting Acquisition And Insurance Expenses [Abstract]
Share-based payments expense	$ 5.5	$ 7.9	$ 11.1	$ 20.8

Income Taxes - Income Tax Provi

Income Taxes - Income Tax Provision (Benefit) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Current tax provision	$ 10.8	$ (11.3)	$ 18.8	$ (2.5)
Future tax deductions	(3)	14.1	1.9	16.7
Valuation allowance change	(0.8)	(1.9)	0.4	(2.9)
Income tax provision	$ 7	$ 0.9	$ 21.1	$ 11.3

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, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 62.2		$ 36.2		$ 134.9		$ 133.3
Effective Tax Rate					0.00%		0.00%
Bermuda [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 35.6		$ 24.6		$ 79.7		$ 68.8
Effective Tax Rate	0.00%		0.00%		0.00%		0.00%
United States [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 28.2		$ 10.5		$ 78		$ 59.1
Effective Tax Rate	24.20%		19.60%		26.30%		22.40%
United Kingdom [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ (2.8)		$ 1.9		$ (24.9)		$ 9.1
Effective Tax Rate	(3.00%)		(58.50%)		(1.90%)		(21.40%)
Belgium [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ (0.1)
Effective Tax Rate	(160.00%)		31.40%		0.00%		(50.50%)
Brazil [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.4		$ (0.7)		$ 1.1		$ (3.7)
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]	$ 0.1		$ 0	[1]	$ 0.2
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	[1]	$ (0.2)		$ (0.1)
Effective Tax Rate	0.00%		0.00%		0.00%		0.00%
Malta [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.9		$ (0.3)		$ 1.2		$ 0	[1]
Effective Tax Rate	0.00%		0.00%		0.00%		0.00%
Switzerland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0	[1]	$ 0.1		$ 0	[1]	$ 0	[1]
Effective Tax Rate	21.20%		(20.00%)		21.10%		(21.30%)
[1]	Pre-tax income for the respective year was less than $0.1 million.

Income Taxes - Schedule of Pr74

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, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 62.2		$ 36.2		$ 134.9		$ 133.3
Belgium [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	0	[1]	0	[1]	0	[1]	(0.1)
Ireland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	(0.1)		0	[1]	(0.2)		(0.1)
Malta [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	0.9		(0.3)		1.2		0	[1]
Switzerland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0	[1]	0.1		$ 0	[1]	0	[1]
Maximum [Member] | Belgium [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)			0.1
Maximum [Member] | Ireland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)			$ 0.1
Maximum [Member] | Malta [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)							0.1
Maximum [Member] | Switzerland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)							$ 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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income tax provision at expected rate	$ 9.8	$ 3.7	$ 23.2	$ 21.1
Tax-exempt interest	(0.7)	(1.2)	(2.5)	(3.1)
Dividends received deduction	(0.4)	(0.6)	(1.7)	(1.8)
Valuation allowance change	(0.8)	(1.9)	0.4	(2.9)
Other permanent adjustments, net	0.1	0.1	0.3	0.3
Adjustment for prior year tax return	(0.8)	(0.6)	(0.8)	(0.6)
Adjustment for annualized rate	(0.9)	0.8	(1.5)	0.6
United States state tax (benefit) expense	0	0	0	(2.5)
Other foreign adjustments	(0.1)	0.1	(0.7)	0.2
Prior year foreign taxes recovered	0	0	0	(1.2)
Deferred tax rate reduction	0	0	(0.3)	0
Foreign exchange adjustments	0.8	0.5	4.4	0.9
Foreign withholding taxes	0	0	0.3	0.3
Income tax provision	7	0.9	21.1	11.3
Income tax provision (benefit) - Foreign	0.2	(1.2)	0.6	(2)
Income tax provision - United States, Federal	6.8	2.1	20.2	16.8
Income tax benefit - United States, State	0	0	0	(3.8)
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, 2016	Sep. 30, 2015
Income Taxes Disclosure [Line Items]
Net operating losses carryback period	2 years
Capital losses carryback period	3 years
Total net deferred tax liabilities	$ 17,500,000
Net operating loss carryforward	16,100,000
Loss carryforwards per year	2,800,000
Valuation allowance	23,200,000
Unrecognized tax benefits	0	$ 0
December 31, 2025 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized	14,600,000
December 31, 2027 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized	1,500,000
Brazil [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	7,500,000
Valuation Allowance Increased	1,400,000
Malta [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	1,500,000
Valuation Allowance Reduced	300,000
PXRE Reinsurance Company [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	14,200,000
Valuation Allowance Reduced	700,000
ARIS [Member]
Income Taxes Disclosure [Line Items]
Net operating loss carryforward	1,000,000
ARIS [Member] | December 31, 2027 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized	200,000
ARIS [Member] | December 31, 2028 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized	400,000
ARIS [Member] | December 31, 2029 [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, 2016USD ($)
Commitments And Contingencies [Line Items]
Contractual commitments related to its limited partnership investments	$ 99.1
Maximum [Member]
Commitments And Contingencies [Line Items]
Contractual commitments period	13 years

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2016USD ($)Segment	Dec. 31, 2015USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment	4
Assets associated with trade capital providers | $	$ 576.8	$ 377.1

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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Earned premiums	$ 358.7	$ 346	$ 1,048.5	$ 1,026.6
Net investment income	32.7	18.4	89.6	68.5
Fee and other income	7.6	9.2	20.2	17.9
Net realized investment and other gains	17.7	6.6	12.8	20.4
Total revenue	416.7	380.2	1,171.1	1,133.4
Income (loss) before income taxes	62.2	36.2	134.9	133.3
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net investment income	1.7	0.7	2.3	7.3
Income (loss) before income taxes	(11.5)	(10.2)	(42.6)	(25.4)
Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	56	39.8	164.7	138.3
Excess and Surplus Lines [Member]
Segment Reporting Information [Line Items]
Earned premiums	122.3	121.5	363.4	351.8
Net investment income	12.7	7.2	35.1	24.6
Excess and Surplus Lines [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	22.8	22	69	64.1
Commercial Specialty [Member]
Segment Reporting Information [Line Items]
Earned premiums	94	87.5	266.3	255.7
Net investment income	7.6	4.4	20.7	15.1
Commercial Specialty [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	23.1	15.1	57.2	31.7
International Specialty [Member]
Segment Reporting Information [Line Items]
Earned premiums	39.9	36.4	117.4	109.8
Net investment income	4.7	2.5	13	8.7
International Specialty [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	15.2	3.1	32.4	21.1
Syndicate 1200 [Member]
Segment Reporting Information [Line Items]
Earned premiums	102.4	100.3	301.1	308.9
Net investment income	2.8	1.9	9.7	6.7
Syndicate 1200 [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	4.9	6.5	20.7	28
Run Off Lines [Member]
Segment Reporting Information [Line Items]
Earned premiums	0.1	0.3	0.3	0.4
Net investment income	3.2	1.7	8.8	6.1
Run Off Lines [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	$ (10)	$ (6.9)	$ (14.6)	$ (6.6)

Segment Information - Schedule

Segment Information - Schedule of Earned Premiums by Geographic Location (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	$ 358.7	$ 346	$ 1,048.5	$ 1,026.6
Bermuda [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	29	26.8	86.1	76.8
Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	10.4	10.3	29.6	34.7
Malta [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	0.6	0.5	1.6	1.4
United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	102.4	99.1	301.1	305.5
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	$ 216.3	$ 209.3	$ 630.1	$ 608.2

Segment Information - Identifia

Segment Information - Identifiable Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 7,181.1	$ 6,625.6	[1]
Excess and Surplus Lines [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	2,266.6	2,174.8
Commercial Specialty [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	1,652.6	1,511.7
International Specialty [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	981.6	877.2
Syndicate 1200 [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	1,364.2	1,216.5
Run Off Lines [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	556.6	558.4
Corporate and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 359.5	$ 287
[1]	Derived from audited consolidated financial statements.

Senior Unsecured Fixed Rate N82

Senior Unsecured Fixed Rate Notes - Additional Information (Detail) - USD ($)	1 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2016	Dec. 31, 2015
Schedule Of Equity Method Investments [Line Items]
Principal amount of senior note		$ 143,800,000	$ 143,800,000
Senior Unsecured Fixed Rate Notes [Member]
Schedule Of Equity Method Investments [Line Items]
Principal amount of senior note	$ 143,750,000
Debt instrument interest rate stated percentage	6.50%
Debt instrument maturity date		Sep. 15, 2042
Initial maturity date		Sep. 15, 2017
Debt Instrument, Redemption Price, Percentage	100.00%

Senior Unsecured Fixed Rate N83

Senior Unsecured Fixed Rate Notes - Schedule Of Unamortized Debt Issuance Costs Deducted From Carrying Value Of Debt Liability (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Principal	$ 143.8	$ 143.8
Less: unamortized debt issuance costs	(4.4)	(4.5)
Senior unsecured fixed rate notes, less unamortized debt issuance costs	$ 139.4	$ 139.3	[1]
[1]	Derived from audited consolidated financial statements.

Senior Unsecured Fixed Rate N84

Senior Unsecured Fixed Rate Notes - Condensed Consolidating Balance Sheet (Detail) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015		Sep. 30, 2015	Dec. 31, 2014
Assets
Investments		$ 4,313.6	$ 4,115.7	[1]
Cash		123.6	121.7	[1]	$ 96.2	$ 81
Accrued investment income		21.9	21.6	[1]
Premiums receivable		503.4	404.5	[1]
Reinsurance recoverables		1,283.1	1,121.1	[1]
Goodwill and other intangible assets, net		221.1	225.5
Current income taxes receivable, net		0	11.6	[1]
Deferred acquisition costs, net		147.7	132.4	[1]
Ceded unearned premiums		311.6	250.8	[1]
Other assets		255.1	220.7	[1]
Intercompany note receivable		0	0
Investments in subsidiaries		0	0
Total assets		7,181.1	6,625.6	[1]
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses		3,284.8	3,123.6	[1]	3,104.1
Unearned premiums		1,010.2	886.7	[1]
Funds held and ceded reinsurance payable, net		518.5	390
Long-term debt		369.4	367.2
Current income taxes payable, net		7.7	0	[1]
Deferred tax liabilities, net		40.7	23.6	[1]
Accrued underwriting expenses and other liabilities		161.4	166.4
Due to (from) affiliates		0	0
Total liabilities		5,392.7	4,957.5	[1]
Total shareholders' equity		1,788.4	1,668.1	[1]
Total liabilities and shareholders' equity		7,181.1	6,625.6	[1]
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]
Assets
Investments		2.6	6.2
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
Deferred acquisition costs, net		0	0
Ceded unearned premiums		0	0
Other assets		9.4	8.2
Intercompany note receivable		0	0
Investments in subsidiaries		1,862.1	1,715.9
Total assets		1,874.1	1,730.3
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		28.4	28.4
Current income taxes payable, net		0
Deferred tax liabilities, net		0	0
Accrued underwriting expenses and other liabilities		13.2	16.3
Due to (from) affiliates		44.1	17.5
Total liabilities		85.7	62.2
Total shareholders' equity		1,788.4	1,668.1
Total liabilities and shareholders' equity		1,874.1	1,730.3
Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) [Member]
Assets
Investments		2,871.2	2,761
Cash		89.3	88.8		84.8	49.3
Accrued investment income		16.3	16.4
Premiums receivable		213.2	166.4
Reinsurance recoverables		1,300.9	1,212.2
Goodwill and other intangible assets, net		127.6	129.8
Current income taxes receivable, net			4.7
Deferred acquisition costs, net		64.7	58.2
Ceded unearned premiums		162.2	125.8
Other assets		160	151.7
Intercompany note receivable		50.2	49.8
Investments in subsidiaries		0	0
Total assets		5,055.6	4,764.8
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses		2,292.7	2,194.1
Unearned premiums		582.7	501.5
Funds held and ceded reinsurance payable, net		733.7	702.6
Long-term debt		284.3	284.2
Current income taxes payable, net		8.8
Deferred tax liabilities, net		25	11.9
Accrued underwriting expenses and other liabilities		109.9	95.4
Due to (from) affiliates		0.2	2.3
Total liabilities		4,037.3	3,792
Total shareholders' equity		1,018.3	972.8
Total liabilities and shareholders' equity		5,055.6	4,764.8
Other Subsidiaries and Eliminations [Member]
Assets
Investments	[2]	1,439.8	1,348.5
Cash	[2]	34.3	32.9		11.4	31.7
Accrued investment income	[2]	5.6	5.2
Premiums receivable	[2]	290.2	238.1
Reinsurance recoverables	[2]	(17.8)	(91.1)
Goodwill and other intangible assets, net	[2]	93.5	95.7
Current income taxes receivable, net	[2]		6.9
Deferred acquisition costs, net	[2]	83	74.2
Ceded unearned premiums	[2]	149.4	125
Other assets	[2]	85.7	60.8
Intercompany note receivable	[2]	(50.2)	(49.8)
Investments in subsidiaries	[2]	0	0
Total assets	[2]	2,113.5	1,846.4
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses	[2]	992.1	929.5
Unearned premiums	[2]	427.5	385.2
Funds held and ceded reinsurance payable, net	[2]	(215.2)	(312.6)
Long-term debt	[2]	56.7	54.6
Current income taxes payable, net	[2]	(1.1)
Deferred tax liabilities, net	[2]	15.7	11.7
Accrued underwriting expenses and other liabilities	[2]	38.3	54.7
Due to (from) affiliates	[2]	(0.2)	(2.3)
Total liabilities	[2]	1,313.8	1,120.8
Total shareholders' equity	[2]	799.7	725.6
Total liabilities and shareholders' equity	[2]	2,113.5	1,846.4
Consolidating Adjustments [Member]
Assets
Investments	[3]	0	0
Cash	[3]	0	0		$ 0	$ 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
Deferred acquisition costs, net	[3]	0	0
Ceded unearned premiums	[3]	0	0
Other assets	[3]	0	0
Intercompany note receivable	[3]	0	0
Investments in subsidiaries	[3]	(1,862.1)	(1,715.9)
Total assets	[3]	(1,862.1)	(1,715.9)
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	0
Current income taxes payable, net	[3]	0
Deferred tax liabilities, net	[3]	0	0
Accrued underwriting expenses and other liabilities	[3]	0	0
Due to (from) affiliates	[3]	(44.1)	(17.5)
Total liabilities	[3]	(44.1)	(17.5)
Total shareholders' equity	[3]	(1,818)	(1,698.4)
Total liabilities and shareholders' equity	[3]	$ (1,862.1)	$ (1,715.9)
[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.

Senior Unsecured Fixed Rate N85

Senior Unsecured Fixed Rate Notes - Condensed Consolidating Statement of Income (Detail) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015
Premiums and other revenue:
Earned premiums	$ 358.7		$ 346		$ 1,048.5		$ 1,026.6
Net investment income (expense)	32.7		18.4		89.6		68.5
Fee and other income	7.6		9.2		20.2		17.9
Net realized investment and other (losses) gains	17.7		6.6		12.8		20.4
Total revenue	416.7		380.2		1,171.1		1,133.4
Expenses:
Losses and loss adjustment expenses	207.8		200		596		574.3
Underwriting, acquisition and insurance expenses	137.4		132.8		403		401.9
Interest expense	4.9		4.8		14.6		14.3
Fee and other expense	5.9		8.2		18.1		18
Foreign currency exchange (gain) loss	(1.5)		(1.8)		4.5		(8.4)
Total expenses	354.5		344		1,036.2		1,000.1
Income before income taxes	62.2		36.2		134.9		133.3
Provision for income taxes	7		0.9		21.1		11.3
Net income before equity in earnings of subsidiaries	55.2		35.3		113.8		122
Equity in undistributed earnings of subsidiaries	0		0		0		0
Net income	55.2		35.3		113.8		122
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]
Premiums and other revenue:
Earned premiums	0		0		0		0
Net investment income (expense)	(0.9)		(0.2)		(2)		(0.7)
Fee and other income	0		0		0		0
Net realized investment and other (losses) gains	0		0		0.2		2
Total revenue	(0.9)		(0.2)		(1.8)		1.3
Expenses:
Losses and loss adjustment expenses	0		0		0		0
Underwriting, acquisition and insurance expenses	3.7		4.9		10		14.4
Interest expense	0.3		0.5		1		1.2
Fee and other expense	0		0		0		0
Foreign currency exchange (gain) loss	0		0		0		0
Total expenses	4		5.4		11		15.6
Income before income taxes	(4.9)		(5.6)		(12.8)		(14.3)
Provision for income taxes	0		0		0		0
Net income before equity in earnings of subsidiaries	(4.9)		(5.6)		(12.8)		(14.3)
Equity in undistributed earnings of subsidiaries	60.1		40.9		126.6		136.3
Net income	55.2		35.3		113.8		122
Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) [Member]
Premiums and other revenue:
Earned premiums	128		122.1		368.1		376
Net investment income (expense)	22.5		11.2		62.6		47.2
Fee and other income	5.5		7.6		14.9		14
Net realized investment and other (losses) gains	19.4		4.3		32.5		20.1
Total revenue	175.4		145.2		478.1		457.3
Expenses:
Losses and loss adjustment expenses	83.5		75.4		220.9		220
Underwriting, acquisition and insurance expenses	54		48		150.6		149.5
Interest expense	4		3.8		11.8		11.4
Fee and other expense	5.5		7.6		16.7		16.4
Foreign currency exchange (gain) loss	0.2		0.1		0.1		1
Total expenses	147.2		134.9		400.1		398.3
Income before income taxes	28.2		10.3		78		59
Provision for income taxes	6.8		2.1		20.5		13.3
Net income before equity in earnings of subsidiaries	21.4		8.2		57.5		45.7
Equity in undistributed earnings of subsidiaries	0		0		0		0
Net income	21.4		8.2		57.5		45.7
Other Subsidiaries and Eliminations [Member]
Premiums and other revenue:
Earned premiums	230.7	[1]	223.9	[1]	680.4	[2]	650.6	[2]
Net investment income (expense)	11.1	[1]	7.6	[1]	29	[2]	22.2	[2]
Fee and other income	2.1	[1]	1.6	[1]	5.3	[2]	3.9	[2]
Net realized investment and other (losses) gains	(1.7)	[1]	2.3	[1]	(19.9)	[2]	0.3	[2]
Total revenue	242.2	[1]	235.4	[1]	694.8	[2]	677	[2]
Expenses:
Losses and loss adjustment expenses	124.3	[1]	124.6	[1]	375.1	[2]	354.3	[2]
Underwriting, acquisition and insurance expenses	79.7	[1]	79.9	[1]	242.4	[2]	238	[2]
Interest expense	0.6	[1]	0.7	[1]	1.8	[2]	1.9	[2]
Fee and other expense	0.4	[1]	0.6	[1]	1.4	[2]	1.6	[2]
Foreign currency exchange (gain) loss	(1.7)	[1]	(1.9)	[1]	4.4	[2]	(9.4)	[2]
Total expenses	203.3	[1]	203.9	[1]	625.1	[2]	586.4	[2]
Income before income taxes	38.9	[1]	31.5	[1]	69.7	[2]	90.6	[2]
Provision for income taxes	0.2	[1]	(1.2)	[1]	0.6	[2]	(2)	[2]
Net income before equity in earnings of subsidiaries	38.7	[1]	32.7	[1]	69.1	[2]	92.6	[2]
Equity in undistributed earnings of subsidiaries	0	[1]	0	[1]	0	[2]	0	[2]
Net income	38.7	[1]	32.7	[1]	69.1	[2]	92.6	[2]
Consolidating Adjustments [Member]
Premiums and other revenue:
Earned premiums	0	[3]	0	[3]	0	[4]	0	[4]
Net investment income (expense)	0	[3]	(0.2)	[3]	0	[4]	(0.2)	[4]
Fee and other income	0	[3]	0	[3]	0	[4]	0	[4]
Net realized investment and other (losses) gains	0	[3]	0	[3]	0	[4]	(2)	[4]
Total revenue	0	[3]	(0.2)	[3]	0	[4]	(2.2)	[4]
Expenses:
Losses and loss adjustment expenses	0	[3]	0	[3]	0	[4]	0	[4]
Underwriting, acquisition and insurance expenses	0	[3]	0	[3]	0	[4]	0	[4]
Interest expense	0	[3]	(0.2)	[3]	0	[4]	(0.2)	[4]
Fee and other expense	0	[3]	0	[3]	0	[4]	0	[4]
Foreign currency exchange (gain) loss	0	[3]	0	[3]	0	[4]	0	[4]
Total expenses	0	[3]	(0.2)	[3]	0	[4]	(0.2)	[4]
Income before income taxes	0	[3]	0	[3]	0	[4]	(2)	[4]
Provision for income taxes	0	[3]	0	[3]	0	[4]	0	[4]
Net income before equity in earnings of subsidiaries	0	[3]	0	[3]	0	[4]	(2)	[4]
Equity in undistributed earnings of subsidiaries	(60.1)	[3]	(40.9)	[3]	(126.6)	[4]	(136.3)	[4]
Net income	$ (60.1)	[3]	$ (40.9)	[3]	$ (126.6)	[4]	$ (138.3)	[4]
[1]	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations.
[2]	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations
[3]	Includes all Argo Group parent company eliminations.
[4]	Includes all Argo Group parent company eliminations

Senior Unsecured Fixed Rate N86

Senior Unsecured Fixed Rate Notes - Condensed Consolidating Statement of Cash Flows (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities		$ 150.7		$ 235.8
Cash flows from investing activities:
Proceeds from sales of investments		1,009.2		728.8
Maturities and mandatory calls of fixed maturity investments		839		637.4
Purchases of investments		(1,855.7)		(1,468.5)
Change in short-term investments and foreign regulatory deposits		(73.9)		(62.4)
Settlements of foreign currency exchange forward contracts		(7.2)		(6.7)
Purchases of fixed assets		(26.7)		(22)
Issuance of intercompany note, net				0
Purchases of fixed assets and other, net		5.2		(4.6)
Cash used in investing activities		(83.4)		(176)
Cash flows from financing activities:
Activity under stock incentive plans		0.6		1.5
Repurchase of Company's common shares		(45.3)		(29.7)
Excess tax expense from share-based payment arrangements		0.1		0.6
Payment of cash dividends to common shareholders		(19.8)		(17.1)
Cash used in financing activities		(64.4)		(44.7)
Effect of exchange rate changes on cash		(1)		0.1
Change in cash		1.9		15.2
Cash, beginning of period		121.7	[1]	81
Cash, end of period		123.6		96.2
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities		19.6		12.6
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		(0.4)		1.3
Settlements of foreign currency exchange forward contracts		0		1.5
Issuance of intercompany note, net				0
Purchases of fixed assets and other, net		0		0.2
Cash used in investing activities		(0.4)		3
Cash flows from financing activities:
Activity under stock incentive plans		0.6		1.5
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		(19.8)		(17.1)
Cash used in financing activities		(19.2)		(15.6)
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		60.6		130.6
Cash flows from investing activities:
Proceeds from sales of investments		762.4		524.5
Maturities and mandatory calls of fixed maturity investments		419.7		509.5
Purchases of investments		(1,134.6)		(1,073.2)
Change in short-term investments and foreign regulatory deposits		(70.5)		(34.5)
Settlements of foreign currency exchange forward contracts		0		0
Issuance of intercompany note, net				15
Purchases of fixed assets and other, net		8.1		(7.3)
Cash used in investing activities		(14.9)		(66)
Cash flows from financing activities:
Activity under stock incentive plans		0		0
Repurchase of Company's common shares		(45.3)		(29.7)
Excess tax expense from share-based payment arrangements		0.1		0.6
Payment of cash dividends to common shareholders		0		0
Cash used in financing activities		(45.2)		(29.1)
Effect of exchange rate changes on cash		0		0
Change in cash		0.5		35.5
Cash, beginning of period		88.8		49.3
Cash, end of period		89.3		84.8
Other Subsidiaries and Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities	[2]	70.5		92.6
Cash flows from investing activities:
Proceeds from sales of investments	[2]	246.8		204.3
Maturities and mandatory calls of fixed maturity investments	[2]	419.3		127.9
Purchases of investments	[2]	(721.1)		(395.3)
Change in short-term investments and foreign regulatory deposits	[2]	(3)		(29.2)
Settlements of foreign currency exchange forward contracts	[2]	(7.2)		(8.2)
Issuance of intercompany note, net	[2]			(15)
Purchases of fixed assets and other, net	[2]	(2.9)		2.5
Cash used in investing activities	[2]	(68.1)		(113)
Cash flows from financing activities:
Activity under stock incentive plans	[2]	0		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 in financing activities	[2]	0		0
Effect of exchange rate changes on cash	[2]	(1)		0.1
Change in cash	[2]	1.4		(20.3)
Cash, beginning of period	[2]	32.9		31.7
Cash, end of period	[2]	34.3		11.4
Consolidating Adjustments [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities	[3]	0		0
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
Purchases of fixed assets and other, net	[3]	0		0
Cash used in investing activities	[3]	0		0
Cash flows from financing activities:
Activity under stock incentive plans	[3]	0		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 in financing activities	[3]	0		0
Effect of exchange rate changes on cash	[3]	0		0
Change in cash	[3]	0		0
Cash, beginning of period	[3]	0		0
Cash, end of period	[3]	$ 0		$ 0
[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.