Argo Group International (ARGO-PA) 10-Q10 Nov 142014 Q3 Quarterly reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
Document and Entity Information	Sep. 30, 2014	Oct. 31, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'AGII	'
Entity Registrant Name	'Argo Group International Holdings, Ltd.	'
Entity Central Index Key	'0001091748	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	25,685,241

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Assets	'	'
Available-for-sale (cost: 2014 - $2,798.6; 2013 - $2,760.1)	$2,840.90	$2,814.40	[1]
Equity securities, at fair value (cost: 2014 - $318.7; 2013 - $346.9)	511.3	534.3	[1]
Other investments (cost: 2014 - $398.0; 2013 - $377.4)	403.3	378.9	[1]
Short-term investments, at fair value (cost: 2014 - $356.2; 2013 - $351.6)	356.2	351.6	[1]
Total investments	4,111.70	4,079.20	[1]
Cash	73.1	157.4	[1]
Accrued investment income	22.2	25.7	[1]
Premiums receivable	396.7	348.4	[1]
Reinsurance recoverables	1,002.30	1,263.50	[1]
Goodwill	153.8	153.8	[1]
Intangible assets, net of accumulated amortization	81.7	86	[1]
Current income taxes receivable, net	30	0	[1]
Deferred acquisition costs, net	130	113.9	[1]
Ceded unearned premiums	227	196.3	[1]
Other assets	160.1	166.8	[1]
Total assets	6,388.60	6,591	[1]
Liabilities and Shareholders' Equity	'	'
Reserves for losses and loss adjustment expenses	3,062.60	3,230.30	[1]
Unearned premiums	865.4	779.1	[1]
Accrued underwriting expenses	130.6	122.3	[1]
Ceded reinsurance payable, net	200.9	354.7	[1]
Funds held	37.9	43.7	[1]
Senior unsecured fixed rate notes	143.8	143.8	[1]
Other indebtedness	64.4	66.3	[1]
Junior subordinated debentures	172.7	193.3	[1]
Current income taxes payable, net	0	5.2	[1]
Deferred tax liabilities, net	55.7	28.7	[1]
Other liabilities	27.7	60.6	[1]
Total liabilities	4,761.70	5,028	[1]
Commitments and contingencies (Note 15)	'	'	[1]
Shareholders' equity:	'	'
Common shares - $1.00 par, 500,000,000 shares authorized; 34,268,995 and 34,066,889 shares issued and outstanding at September 30, 2014 and December 31, 2013, respectively	34.3	34.1	[1]
Additional paid-in capital	834.4	827.3	[1]
Treasury shares (8,440,355 and 7,558,345 shares at September 30, 2014 and December 31, 2013, respectively)	-292.7	-250.6	[1]
Retained earnings	914.4	804.4	[1]
Accumulated other comprehensive income, net of taxes	136.5	147.8	[1]
Total shareholders' equity	1,626.90	1,563	[1]
Total liabilities and shareholders' equity	$6,388.60	$6,591	[1]

[1]	Derived from audited consolidated financial statements.

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]	'	'
Available-for-sale cost	$2,798.60	$2,760.10	[1]
Equity securities cost	318.7	346.9	[1]
Other investments cost	398	377.4	[1]
Short-term investments, Cost	$356.20	$351.60	[1]
Common shares, par value	$1	$1	[1]
Common shares, shares authorized	500,000,000	500,000,000	[1]
Common shares, shares issued	34,268,995	34,066,889	[1]
Common shares, shares outstanding	34,268,995	34,066,889	[1]
Treasury shares, shares	8,440,355	7,558,345	[1]

[1]	Derived from audited consolidated financial statements.

Consolidated_Statements_of_Inc

Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Premiums and other revenue:	'	'	'	'
Earned premiums	$337.60	$330.50	$999.40	$962.20
Net investment income	20.8	24.1	64.7	77.3
Fee income, net	1.6	0.3	0.1	0.5
Net realized investment gains and other	12.9	9.1	42.5	29.6
Total revenue	372.9	364	1,106.70	1,069.60
Expenses:	'	'	'	'
Losses and loss adjustment expenses	191.9	190.9	559.5	554.1
Other reinsurance-related expenses	0	4.6	0	14.4
Underwriting, acquisition and insurance expenses	133.8	126.7	399.3	378
Interest expense	4.9	5.1	15	15.1
Foreign currency exchange (gain) loss	-6	3.8	-2.8	-5.2
Total expenses	324.6	331.1	971	956.4
Income before income taxes	48.3	32.9	135.7	113.2
Provision for income taxes	3.6	1.9	12.2	17.8
Net income	44.7	31	123.5	95.4
Net income per common share:	'	'	'	'
Basic	$1.72	$1.16	$4.71	$3.54
Diluted	$1.69	$1.12	$4.63	$3.41
Dividend declared per common share:	$0.18	$0.15	$0.51	$0.44
Weighted average common shares:	'	'	'	'
Basic	25,956,599	26,682,176	26,203,819	26,961,792
Diluted	26,436,933	27,819,550	26,670,176	27,993,335
Net realized investment gains and other before other-than-temporary impairment losses	13.1	9.2	44.1	31.5
Other-than-temporary impairment losses recognized in earnings	'	'	'	'
Other-than-temporary impairment losses on fixed maturities	0	0	-1.2	-0.3
Other-than-temporary impairment losses on equity securities	-0.2	-0.1	-0.4	-1.6
Other-than-temporary impairment losses on Funds at Lloyd's foreign currency exchange	0	0	0	0
Other-than-temporary impairment losses on other investments	0	0	0	0
Impairment losses recognized in earnings	-0.2	-0.1	-1.6	-1.9
Net realized investment gains and other	$12.90	$9.10	$42.50	$29.60

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Loss) (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Net income	$44.70	$31	$123.50	$95.40
Other comprehensive income:	'	'	'	'
Foreign currency translation adjustments	-2.3	-0.3	-1.9	-2.2
Unrealized gains (losses) on securities:	'	'	'	'
(Losses) gains arising during the period	-38.8	23.2	16.1	-34.8
Reclassification adjustment for gains included in net income	-5.8	-3.3	-22	-18.3
Other comprehensive (loss) income before tax	-46.9	19.6	-7.8	-55.3
Unrealized gains (losses) on securities:	'	'	'	'
(Losses) gains arising during the period	-4.9	5.4	10.7	-10.9
Reclassification adjustment for gains included in net income	-4.1	-2	-7.2	-6.7
Income tax provision related to other comprehensive (loss) income	-9	3.4	3.5	-17.6
Other comprehensive (loss) income, net of tax	-37.9	16.2	-11.3	-37.7
Comprehensive income	$6.80	$47.20	$112.20	$57.70

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
Cash flows from operating activities:	'		'
Net income	$123.50		$95.40
Adjustments to reconcile net income to net cash (used) provided by operating activities:	'		'
Amortization and depreciation	27.8		28.8
Share-based payments expense	13.3		17.8
Excess tax benefit from share-based payment arrangements	-0.1		-0.2
Deferred income tax provision, net	22.9		4.4
Net realized investment and other gains	-42.5		-29.6
Loss on disposals of fixed assets, net	0		0.2
Change in:	'		'
Accrued investment income	3.5		5
Receivables	214.1		-3.5
Deferred acquisition costs	-13		-15.5
Ceded unearned premiums	-31.2		-38.5
Reserves for losses and loss adjustment expenses	-167.7		1.4
Unearned premiums	87.6		118.8
Ceded reinsurance payable and funds held	-159.5		-188.3
Income taxes	-35.3		-2.3
Accrued underwriting expenses	4.1		27.6
Other, net	24.2		-24.5
Cash provided (used) by operating activities	71.7		-3
Cash flows from investing activities:	'		'
Sales of fixed maturity investments	884.6		1,308
Maturities and mandatory calls of fixed maturity investments	243.6		224.2
Sales of equity securities	61.8		65
Sales of other investments	29.7		5.8
Purchases of fixed maturity investments	-1,197.30		-1,264.70
Purchases of equity securities	-17.7		-71.4
Purchases of other investments	-49.8		-71.2
Change in foreign regulatory deposits and voluntary pools	22.5		0.6
Change in short-term investments	-16.5		-76.1
Settlements of foreign currency exchange forward contracts	0.6		-6.4
Purchases of fixed assets	-26.7		-19.1
Other, net	-21.5		4.5
Cash (used) provided by investing activities	-86.7		99.2
Cash flows from financing activities:	'		'
Redemption of trust preferred securities, net	-18		0
Payment on note payable	-0.1		0
Activity under stock incentive plans	3.3		1.4
Repurchase of Company's common shares	-40.9		-40.1
Excess tax expense from share-based payment arrangements	0.1		0.2
Payment of cash dividends to common shareholders	-13.4		-11.8
Cash used by financing activities	-69		-50.3
Effect of exchange rate changes on cash	-0.3		-0.1
Change in cash	-84.3		45.8
Cash, beginning of period	157.4	[1]	95.8
Cash, end of period	$73.10		$141.60

[1]	Derived from audited consolidated financial statements.

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2014
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, 2013, filed with the Securities and Exchange Commission on February 28, 2014.
	The interim financial information as of, and for the three and nine months ended, September 30, 2014 and 2013 is unaudited. However, in the opinion of management, the interim information includes all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results presented for the interim periods. The operating results for the interim periods are not necessarily indicative of the results to be expected for the full year. All significant intercompany amounts have been eliminated in consolidation. Certain amounts in prior years’ financial statements have been reclassified to conform to the current presentation.
	10% Stock Dividend
	On May 7, 2013, our Board of Directors declared a 10% stock dividend, payable on June 17, 2013, to shareholders of record at the close of business on June 3, 2013. As a result of the stock dividend, 2,447,839 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_Sta

Recently Issued Accounting Standards	9 Months Ended
	Sep. 30, 2014
Accounting Changes and Error Corrections [Abstract]	'
Recently Issued Accounting Standards	'
	2	Recently Issued Accounting Standards
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued amendments to “Liabilities” (Topic 405) in order to resolve diversity in practice related to accounting for the recognition, measurement and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. The amendments require an entity to measure the liability as the sum of (a) the amount the reporting entity agreed to pay on the basis of its arrangement among its co-obligors and (b) any additional amount the reporting entity expects to pay on behalf of its co-obligors. The amendments in this update are effective for fiscal years, and interim periods within those years, beginning after December 15, 2013, but early adoption is permitted. The amendments should be applied retrospectively to all prior periods presented for those obligations resulting from joint and several liability arrangements within the update’s scope that exist at the beginning of an entity’s fiscal year of adoption. The adoption of this amendment did not have a material impact on our financial results or disclosures.
	In March 2013, the FASB issued an amendment to “Consolidation” (Topic 810) to resolve the diversity in practice related to the release of the cumulative translation adjustment into net income when a parent sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets that is a nonprofit activity or a business within a foreign entity. The amendments in the update are effective prospectively for fiscal years, and interim reporting periods within those years, beginning after December 15, 2013, but early adoption is permitted. The amendments should be applied prospectively to derecognition events occurring after the effective date with no adjustment to prior periods. The adoption of this amendment did not have an impact on our financial results or disclosures.

	In July 2013, the FASB issued amendments to “Income Taxes” (Topic 740) that require the presentation of certain unrecognized tax benefits as reductions to deferred tax assets rather than liabilities in our Consolidated Balance Sheets when a net operating loss carryforward, similar tax loss or tax credit carryforward exists. The new standard requires adoption on a prospective basis. The adoption of this amendment did not have an impact on our financial results or disclosures.
	In April 2014, the FASB issued amendments to “Presentation of Financial Statements (Topic 205) and Property, Plant and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity.” The amendments require that a disposal representing a strategic shift that has, or will have, a major effect on an entity’s financial results or a business activity classified as held for sale should be reported as discontinued operations. The amendments also expand the disclosure requirements for discontinued operations and add new disclosures for individually significant dispositions that do not qualify as discontinued operations. The amendments are effective prospectively for fiscal years, and interim reporting periods within those years, beginning after December 15, 2014. Early adoption is permitted only for disposals not previously reported. We do not anticipate this update will have an impact on our financial results and disclosures.
	In May 2014, the FASB issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers” (Topic 606). The ASU is a comprehensive new revenue recognition model that requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. The ASU provides a five-step analysis of transactions to determine when and how revenue is recognized and requires additional disclosures sufficient to describe the nature, amount, timing and uncertainty of revenue and cash flows for these transactions. This ASU is effective for annual reporting periods beginning after December 15, 2016 and early adoption is not permitted. Accordingly, we will adopt this ASU on January 1, 2017. Companies may use either a “full retrospective” adoption, meaning the update is applied to all periods presented, or a “modified retrospective” adoption, meaning the update is applied only to the most current period presented in the financial statements. While insurance contracts are excluded from this ASU, our 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 are currently evaluating what impact this ASU will have on our financial results and disclosures and which adoption method to apply.

Investments

Investments	9 Months Ended
Investments	Sep. 30, 2014
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, 2014		Amortized			Gross			Gross			Fair
	(in millions)		Cost			Unrealized			Unrealized			Value
						Gains			Losses
	Fixed maturities
	USD denominated:
	U.S. Governments		$	209.8		$	1.5		$	0.5		$	210.8
	Non-U.S. Governments			76.9			0.6			0.5			77
	Obligations of states and political subdivisions			485.6			24.2			0.6			509.2
	Credit-Financial			489.1			12.8			1.3			500.6
	Credit-Industrial			461			10.3			2.8			468.5
	Credit-Utility			146.8			4.3			0.7			150.4
	Structured securities:
	CMO/MBS-agency (1)			179.4			8.2			0.9			186.7
	CMO/MBS-non agency			13.7			0.9			0			14.6
	CMBS (2)			163.8			2.1			0.2			165.7
	ABS-residential (3)			5.2			0			0.3			4.9
	ABS-non residential			209.2			0.8			0.3			209.7
	Foreign denominated:
	Governments			140.4			1.8			7.4			134.8
	Credit			217.7			3			12.7			208

	Total fixed maturities			2,798.60			70.5			28.2			2,840.90
	Equity securities			318.7			195.2			2.6			511.3
	Other investments			398			7.3			2			403.3
	Short-term investments			356.2			0			0			356.2

	Total investments		$	3,871.50		$	273		$	32.8		$	4,111.70



	December 31, 2013		Amortized			Gross			Gross			Fair
	(in millions)		Cost			Unrealized			Unrealized			Value
						Gains			Losses
	Fixed maturities
	USD denominated:
	U.S. Governments		$	273.4		$	2.4		$	0.5		$	275.3
	Non-U.S. Governments			60.9			0.3			1			60.2
	Obligations of states and political subdivisions			563.7			22.9			8.8			577.8
	Credit-Financial			426.3			15.4			1.8			439.9
	Credit-Industrial			385.5			13.8			2.2			397.1
	Credit-Utility			162			5.4			0.8			166.6
	Structured securities:
	CMO/MBS-agency (1)			219.4			9.2			1.7			226.9
	CMO/MBS-non agency			19.4			0.8			0			20.2
	CMBS (2)			162.7			3.1			1			164.8
	ABS-residential (3)			6.8			0.3			0.5			6.6
	ABS-non residential			116.8			0.5			0.1			117.2
	Foreign denominated:
	Governments			207.7			4.9			5.9			206.7
	Credit			155.5			4.4			4.8			155.1

	Total fixed maturities			2,760.10			83.4			29.1			2,814.40
	Equity securities			346.9			188.6			1.2			534.3
	Other investments			377.4			2.8			1.3			378.9
	Short-term investments			351.6			0			0			351.6

	Total investments		$	3,836.00		$	274.8		$	31.6		$	4,079.20


(1)	Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”).
(2)	Commercial mortgage-backed securities (“CMBS”).
(3)	Asset-backed securities (“ABS”).
Included in “Total investments” in our Consolidated Balance Sheets at September 30, 2014 and December 31, 2013 is $70.1 million and $87.3 million, respectively, of assets managed on behalf of the trade capital providers, who are third-party capital participants that provide underwriting capital to our Syndicate 1200 segment.
Contractual Maturity
The amortized cost and fair values of fixed maturity investments as of September 30, 2014, by contractual maturity, were as follows:


(in millions)		Amortized			Fair
(in millions)		Cost			Value
Due in one year or less		$	255.7		$	254.2
Due after one year through five years			1,329.30			1,343.20
Due after five years through ten years			472.9			488.2
Thereafter			169.4			173.7
Structured securities			571.3			581.6

Total		$	2,798.60		$	2,840.90

The expected maturities may differ from the contractual maturities because debtors may have the right to call or prepay obligations.

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, 2014		Less Than One Year						One Year or Greater						Total
(in millions)		Fair			Unrealized			Fair			Unrealized			Fair			Unrealized
		Value			Losses			Value			Losses			Value			Losses
Fixed maturities
USD denominated:
U.S. Governments		$	59.5		$	0.3		$	16.3		$	0.2		$	75.8		$	0.5
Non-U.S. Governments			28.3			0.1			7.5			0.4			35.8			0.5
Obligations of states and political subdivisions			16.4			0.1			27.9			0.5			44.3			0.6
Credit-Financial			149.1			1.1			14.3			0.2			163.4			1.3
Credit-Industrial			222.5			2.5			13.5			0.3			236			2.8
Credit-Utility (2)			42.5			0.7			1.9			0			44.4			0.7
Structured securities:
CMO/MBS-agency			23.8			0.1			17.1			0.8			40.9			0.9
CMBS			29.8			0.1			6.6			0.1			36.4			0.2
ABS-residential			0			0			3.4			0.3			3.4			0.3
ABS-non residential (2)			106.9			0.3			3.6			0			110.5			0.3
Foreign denominated:
Governments			111.5			6.9			17			0.5			128.5			7.4
Credit			179.8			12.6			0.7			0.1			180.5			12.7

Total fixed maturities			970.1			24.8			129.8			3.4			1,099.90			28.2
Equity securities			32.1			2.6			0			0			32.1			2.6
Other investments			(2.0	)		2			0			0			(2.0	)		2

Total		$	1,000.20		$	29.4		$	129.8		$	3.4		$	1,130.00		$	32.8



December 31, 2013		Less Than One Year						One Year or Greater						Total
(in millions)		Fair			Unrealized			Fair			Unrealized			Fair			Unrealized
		Value			Losses			Value			Losses			Value			Losses
Fixed maturities
USD denominated:
U.S. Governments		$	55.3		$	0.5		$	0		$	0		$	55.3		$	0.5
Non-U.S. Governments			36.3			1			0			0			36.3			1
Obligations of states and political subdivisions (2)			154.6			8.8			3.1			0			157.7			8.8
Credit-Financial			88.7			1.7			2.4			0.1			91.1			1.8
Credit-Industrial			85.7			2			2.9			0.2			88.6			2.2
Credit-Utility			21.2			0.7			1.9			0.1			23.1			0.8
Structured securities:
CMO/MBS-agency			58.4			1.2			5.6			0.5			64			1.7
CMBS (2)			24.2			1			1.1			0			25.3			1
ABS-residential			0			0			3.6			0.5			3.6			0.5
ABS-non residential (2)			59.1			0.1			2			0			61.1			0.1
Foreign denominated:
Governments			170.5			5.9			0			0			170.5			5.9
Credit			125.3			4.8			0			0			125.3			4.8

Total fixed maturities			879.3			27.7			22.6			1.4			901.9			29.1
Equity securities			25.5			1.2			0			0			25.5			1.2
Other investments			(1.4	)		1.3			0			0			(1.4	)		1.3
Short-term investments (1)			4.5			0			0			0			4.5			0

Total		$	907.9		$	30.2		$	22.6		$	1.4		$	930.5		$	31.6


(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. Loss severity includes such factors as trends in real estate values and proceeds at foreclosure. 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 our fixed maturity securities that we intend to sell.
We hold a total of 5,853 securities, of which 1,668 were in an unrealized loss position for less than one year and 167 were in an unrealized loss position for a period one year or greater as of September 30, 2014. 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-temporily 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 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, 2014.
There were no recognized other-than-temporary losses on our fixed maturities portfolio for the three months ended September 30, 2014 and 2013, respectively. We recognized other-than-temporary losses on our fixed maturities portfolio of $1.2 million and $0.3 million for the nine months ended September 30, 2014 and 2013, respectively. We recognized other-than-temporary losses on our equity portfolio of $0.2 million and $0.4 million for the three and nine months ended September 30, 2014, respectively. We recognized other-than-temporary losses on our equity portfolio of $0.1 million and $1.6 million for the three and nine months ended September 30, 2013, respectively.
Realized Gains and Losses
The following table presents our gross realized investment gains (losses):


		For the Three Months						For the Nine Months
		Ended September 30,						Ended September 30,
(in millions)		2014			2013			2014			2013
Realized gains
Fixed maturities		$	4.5		$	5.8		$	15.2		$	27.5
Equity securities			0.7			7.2			16.1			15
Other investments			13.6			11.2			36.5			28.9
Short-term investments			0			0.1			0.1			0.1
Other assets			2			0			2			0

Gross realized investment gains			20.8			24.3			69.9			71.5
Realized losses
Fixed maturities			(1.1	)		(6.1	)		(8.7	)		(14.5	)
Equity securities			(0.1	)		(0.1	)		(0.2	)		(0.8	)
Other investments			(6.5	)		(8.6	)		(12.6	)		(24.1	)
Short-term investments			0			(0.3	)		(0.3	)		(0.6	)
Other assets			0			0			(4.0	)		0
Other-than-temporary impairment losses on fixed maturities			0			0			(1.2	)		(0.3	)
Other-than-temporary impairment losses on equity securities			(0.2	)		(0.1	)		(0.4	)		(1.6	)

Gross realized investment and other losses			(7.9	)		(15.2	)		(27.4	)		(41.9	)

Net realized investment gains and other		$	12.9		$	9.1		$	42.5		$	29.6

As of September 30, 2013, we hedged $2.0 million of certain holdings in non-U.S. Dollar denominated fixed maturity investments with $1.8 million of foreign exchange contracts. The net realized effect on income was not significant for the three and nine months ended September 30, 2013. This program was discontinued in 2014 and the net realized effect on income was not significant.

We also enter into foreign currency exchange forward contracts to manage currency exposure on losses related to global catastrophe events. These currency forward contracts are carried at fair value in our Consolidated Balance Sheets in “Other investments.” The realized and unrealized gains and losses are included in “Net realized investment gains and other” in our Consolidated Statements of Income. The notional amount of the currency forward contracts was $25.6 million and $53.2 million as of September 30, 2014 and 2013, respectively. The fair value of the currency forward contracts was a loss of $2.0 million and a gain $1.6 million as of September 30, 2014 and 2013, respectively. For the three and nine months ended September 30, 2014, we recognized $2.1 million and $0.2 million in net realized losses, respectively, from the catastrophe event currency forward contracts. For the three and nine months ended September 30, 2013, we recognized $2.4 million in net realized gains and $2.2 million in net realized losses, respectively, from the catastrophe event currency forward contracts.
In 2014, we entered into foreign currency exchange forward contracts to manage currency exposure on our Canadian dollar (“CAD”) investment portfolio. The currency forward contracts are carried at fair value in our Consolidated Balance Sheets in “Other investments.” The realized and unrealized gains and losses are included in “Net realized investment gains and other” in our Consolidated Statements of Income. The notional amount of the currency forward contracts was $118.3 million as of September 30, 2014. The fair value of the currency forward contracts was $1.5 million as of September 30, 2014. For the three and nine months ended September 30, 2014, we recognized $1.1 million in net realized gains from the Canadian dollar currency forward contracts.
Also in 2014, we entered into foreign currency exchange forward contracts to manage currency exposure on certain Euro denominated investments. The currency forward contracts are carried at fair value in our Consolidated Balance Sheets in “Other investments”. The realized and unrealized gains and losses are included in “Net realized investment gains and other” in our Consolidated Statements of Income. The fair value of the currency forward contracts was $1.9 million as of September 30, 2014. For the three and nine months ended September 30, 2014, we recognized $2.0 million in net realized gains from these currency forward contracts.
Regulatory Deposits, Pledged Securities and Letters of Credit
At September 30, 2014, the amortized cost and fair value of investments on deposit with U.S. and various regulatory agencies for regulatory purposes were $196.0 million and $204.4 million, respectively. At December 31, 2013, the amortized cost and fair value of investments on deposit with U.S. and various regulatory agencies for regulatory purposes were $196.7 million and $203.4 million, respectively.
At September 30, 2014, investments with an amortized cost of $55.4 million and fair value of $55.8 million were pledged as collateral in support of irrevocable letters of credit (“LOC’s”) in the amount of $45.0 million issued under the terms of certain reinsurance agreements in respect of reported loss and loss expense reserves. At December 31, 2013, investments with an amortized cost of $96.6 million and fair value of $97.5 million were pledged as collateral in support of irrevocable LOC’s in the amount of $60.2 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 $243.2 million and $250.8 million at September 30, 2014 and December 31, 2013, 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 assumptions about the assumptions market participants would use in pricing the asset or liability based on the best information available in the circumstances.
We receive fair value prices from third-party pricing services and our outside investment managers. These prices are determined using observable market information such as dealer quotes, market spreads, cash flows, yield curves, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things. We have reviewed the processes used by the third-party providers for pricing the securities, and have determined that these processes result in fair values consistent with GAAP requirements. In addition, we review these prices for reasonableness, and have not adjusted any prices received from the third-party providers as of September 30, 2014. 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 residential and ABS non-residential 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 interests in equity funds that are reported at fair value using Level 2 inputs. The valuations are based on the funds’ net asset value per share, determined weekly or at the end of each month. The underlying assets in the funds 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.

Other Assets Level 3: We had one reinsurance contract deemed a derivative in 2013. The fair values were estimated by management taking into account changes in the market for catastrophic bond reinsurance contracts with similar economic characteristics and potential recoveries from events preceding the valuation date. See Note 4, “Derivative Instruments” for related disclosures.
Transfers Between Level 1 and Level 2 Securities: There were no transfers between Level 1 and Level 2 securities during the three and nine months ended September 30, 2014 or 2013.
Based on an analysis of the inputs, our financial assets measured at fair value on a recurring basis have been categorized as follows:


					Fair Value Measurements at Reporting Date Using
(in millions)		September 30, 2014			Level 1 (a)			Level 2 (b)			Level 3 (c)
Fixed maturities
USD denominated:
U.S. Governments		$	210.8		$	120.8		$	90		$	0
Non-U.S. Governments			77			0			77			0
Obligations of states and political subdivisions			509.2			0			509.2			0
Credit-Financial			500.6			0			500.6			0
Credit-Industrial			468.5			0			468.5			0
Credit-Utility			150.4			0			150.4			0
Structured securities:
CMO/MBS-agency			186.7			0			186.7			0
CMO/MBS-non agency			14.6			0			14.6			0
CMBS			165.7			0			165.7			0
ABS-residential			4.9			0			4.9			0
ABS-non residential			209.7			0			209.7			0
Foreign denominated:
Governments			134.8			0			134.8			0
Credit			208			0			208			0

Total fixed maturities			2,840.90			120.8			2,720.10			0
Equity securities			511.3			471			39.3			1
Other investments			98.1			0			98.1			0
Short-term investments			356.2			354.1			2.1			0

		$	3,806.50		$	945.9		$	2,859.60		$	1


(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, 2013			Level 1 (a)			Level 2 (b)			Level 3 (c)
Fixed maturities
USD denominated:
U.S. Governments		$	275.3		$	143.8		$	131.5		$	0
Non-U.S. Governments			60.2			0			60.2			0
Obligations of states and political subdivisions			577.8			0			577.8			0
Credit-Financial			439.9			0			439.9			0
Credit-Industrial			397.1			0			397.1			0
Credit-Utility			166.6			0			166.6			0
Structured securities:
CMO/MBS-agency			226.9			0			226.9			0
CMO/MBS-non agency			20.2			0			20.2			0
CMBS			164.8			0			164.8			0
ABS-residential			6.6			0			6.6			0
ABS-non residential			117.2			0			117.2			0
Foreign denominated:
Governments			206.7			0			206.7			0
Credit			155.1			0			155.1			0

Total fixed maturities			2,814.40			143.8			2,670.60			0
Equity securities			534.3			476.7			56.3			1.3
Other investments			117.8			0			117.8			0
Short-term investments			351.6			347			4.6			0
Other assets			2.6			0			0			2.6

		$	3,820.70		$	967.5		$	2,849.30		$	3.9


(a)	Quoted prices in active markets for identical assets
(b)	Significant other observable inputs
(c)	Significant unobservable inputs
The fair value measurements in the tables above do not equal “Total investments” on our Consolidated Balance Sheets as they exclude certain other investments that are accounted for under the equity-method of accounting and include reinsurance contracts that are classified as “Other assets”.
A reconciliation of the beginning and ending balances for the investments categorized as Level 3 are as follows:
Fair Value Measurements Using Observable Inputs (Level 3)


(in millions)		Equity			Other Assets			Total
(in millions)		Securities			Other Assets			Total
Beginning balance, January 1, 2014		$	1.3		$	2.6		$	3.9
Transfers into Level 3			0			0			0
Transfers out of Level 3			0			0			0
Total gains or losses (realized/unrealized):
Included in net income (loss)			0			0			0
Included in other comprehensive income (loss)			0			0			0
Purchases, issuances, sales, and settlements
Purchases			0			0			0
Issuances			0			0			0
Sales			(0.3	)		0			(0.3	)
Settlements			0			(2.6	)		(2.6	)

Ending balance, September 30, 2014		$	1		$	0		$	1

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, 2014		$	0		$	0		$	0



(in millions)		Equity			Other Assets			Total
(in millions)		Securities			Other Assets			Total
Beginning balance, January 1, 2013		$	1.8		$	6.9		$	8.7
Transfers into Level 3			0			0			0
Transfers out of Level 3			0			0			0
Total gains or losses (realized/unrealized):
Included in net income (loss)			0.1			0			0.1
Included in other comprehensive income (loss)			0			0			0
Purchases, issuances, sales, and settlements
Purchases			0			0			0
Issuances			0			0			0
Sales			(0.6	)		0			(0.6	)
Settlements			0			(4.3	)		(4.3	)

Ending balance, December 31, 2013		$	1.3		$	2.6		$	3.9

Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2013		$	0		$	0		$	0

At September 30, 2014 and December 31, 2013, 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.

Derivative_Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Instruments	'
	4	Derivative Instruments
	Through our subsidiary Argo Re, Ltd. (“Argo Re”), we entered into a reinsurance contract with a special purpose reinsurance company that provided us with protection against certain severe catastrophe events and the occurrence of multiple significant catastrophe events during the same year. The contract entered into on December 28, 2011 and effective January 1, 2012, provided coverage of $100 million for hurricanes and earthquakes (including fire) in the U.S. and covered losses for the first and subsequent events on a per-occurrence basis over a 24-month coverage period. This contract expired in December 2013. Each event had an activation level, which, if attained, put the notes on risk for a subsequent event. Once the coverage had been activated, a second loss during the coverage period in excess of the loss trigger level resulted in a loss to the note holders. This transaction ignored the effects of inuring reinsurance, creating the remote possibility of a double recovery on covered events, and was therefore deemed to be a derivative.
	We recorded the contract at fair value, and such fair value is included in “Other assets” in our Consolidated Balance Sheets with any changes in the value reflected in “Other reinsurance-related expenses” in our Consolidated Statements of Income. As there is no quoted fair value available for this derivative, the fair value was estimated by management taking into account changes in the market for catastrophe bond reinsurance contracts with similar economic characteristics and potential recoveries from events preceding the valuation date. Included in “Other reinsurance-related expenses” for the three and nine months ended September 30, 2013 was $4.6 million and $14.4 million, respectively, which was incurred due to the change in the fair value of the derivative, principally due to the passage of the transaction’s risk coverage term. Included in “Other assets” in our Consolidated Balance Sheets at December 31, 2013 was $2.6 million, which represented the fair value of the contract at that date. As the contract expired in December 2013, no such expense was incurred during 2014, nor was it reflected on our Consolidated Balance Sheets at September 30, 2014.
	The special purpose reinsurance company that was the counterparty to this transaction was a variable interest entity under the provisions of Accounting Standards Codification (“ASC”) Topic 810-10, “Consolidation.” Argo Group was not the primary beneficiary of this entity and was therefore not required to consolidate it in our consolidated financial statements.

Reserves_for_Losses_and_Loss_A

Reserves for Losses and Loss Adjustment Expenses	9 Months Ended
Reserves for Losses and Loss Adjustment Expenses	Sep. 30, 2014
Insurance [Abstract]	'
Reserves for Losses and Loss Adjustment Expenses	'
	5	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)		2014			2013
	Net reserves beginning of the year		$	2,107.60		$	2,110.90
	Add:
	Losses and LAE incurred during current calendar year, net of reinsurance:
	Current accident year			585.9			575.6
	Prior accident years			(26.4	)		(21.5	)

	Losses and LAE incurred during calendar year, net of reinsurance			559.5			554.1

	Deduct:
	Losses and LAE payments made during current calendar year, net of reinsurance:
	Current accident year			115.3			131.7
	Prior accident years			435.5			429

	Losses and LAE payments made during current calendar year, net of reinsurance			550.8			560.7

	Add:
	Change in participation interest (1)			24.7			10.4
	Foreign exchange adjustments			(4.9	)		(6.3	)

	Net reserves - end of period			2,136.10			2,108.40
	Add:
	Reinsurance recoverables on unpaid losses and LAE, end of period			926.5			1,114.50

	Gross reserves - end of period		$	3,062.60		$	3,222.90


	(1)	Amount represents increase in reserves due to change in syndicate participation.
	On December 31, 2012, Syndicate 1200 entered into a retroactive whole account quota share contract covering the 2009 and prior years of account. The counterparty was another syndicate within the Lloyd’s market. As a result of this transaction, reserves for losses and LAE at December 31, 2012 were net of $192.2 million ceded under this quota share agreement. Subject to a Split Reinsurance to Close arrangement previously approved by the Prudential Regulatory Authority, the liabilities assumed by the whole account quota share provider were legally transferred to that quota share provider on January 18, 2014, with an inception date of January 1, 2014.
	Reserves for losses and loss adjustment expenses represent the estimated indemnity cost and related adjustment expenses necessary to investigate and settle claims. Such estimates are based upon individual case estimates for reported claims, estimates from ceding companies for reinsurance assumed and actuarial estimates for losses that have been incurred but not yet reported to the insurer. Any change in probable ultimate liabilities is reflected in current operating results.
	Impacting losses and LAE for the nine months ended September 30, 2014 was $26.4 million in favorable prior years’ loss reserve development comprised of the following: $34.6 million of net favorable development in the Excess and Surplus Lines segment primarily caused by favorable development in the general and products liability lines, partially offset by unfavorable development in commercial automobile and property lines; $5.2 million of net unfavorable development in the Commercial Specialty segment, primarily driven by unfavorable development in general liability lines due to increases in claim severity, as well as unfavorable development in auto liability lines, partially offset by favorable development in short-tail and workers compensation lines; $0.1 million of net favorable development in the International Specialty segment; $15.8 million of net favorable development in the Syndicate 1200 segment primarily driven by favorable development in various property classes, as well as favorable development in professional indemnity and aerospace, partially offset by unfavorable development in general liability; $18.9 million of unfavorable development in the Run-off Lines segment primarily caused by $9.9 million of unfavorable development in workers compensation lines driven by increasing medical costs on older claims, as well as $9.0 million in asbestos liability driven by increasing defense costs on primary business and activity on assumed business including the impact of arbitrations and commutations.

	Impacting losses and LAE for the nine months ended September 30, 2013 was $21.5 million in favorable prior years’ loss reserve development comprised of the following: $26.8 million net favorable development in the Excess and Surplus Lines segment primarily caused by favorable development in the general and products liability lines, partially offset by unfavorable development in commercial automobile; $0.4 million of net unfavorable development in the Commercial Specialty segment, primarily driven by unfavorable development in general liability lines due to increases in claim severity and unfavorable development in automobile liability lines, partially offset by favorable development in short-tail and workers compensation lines; $0.6 million net favorable development in the International Specialty segment; $4.1 million net favorable development in the Syndicate 1200 segment driven by favorable development in various property classes, partially offset by unfavorable development in the onshore energy and general liability classes of business; $9.6 million unfavorable development in the Run-off Lines segment primarily caused by $6.4 million of unfavorable development in asbestos driven by an increase in defense costs for claims from general liability policies written on a direct basis and commutation and settlement activity and $2.0 million of unfavorable development in the medical malpractice liability line due to the loss of the New York Liquidation Bureau funding for structured settlement annuity payments.
	In the opinion of management, our reserves represent the best estimate of our ultimate liabilities, based on currently known facts, current law, current technology and assumptions considered reasonable where facts are not known. Due to the significant uncertainties and related management judgments, there can be no assurance that future loss development, favorable or unfavorable, will not occur.

Debt

Debt	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Debt	'
	6	Debt
	Borrowing Under Revolving Credit Facility
	On March 7, 2014, each of Argo Group, Argo Group US, Inc., Argo International Holdings Limited and Argo Underwriting Agency Limited (the “Borrowers”) entered into a $175.0 million Credit Agreement (“New Credit Agreement”) with JPMorgan Chase Bank, N.A., as administrative agent. The New Credit Agreement replaced and terminated the original $150.0 million Credit Agreement. The New Credit Agreement provides for a $175.0 million revolving credit facility with a maturity date of March 7, 2018 unless extended in accordance with the terms of the New Credit Agreement. Borrowings under the New Credit Agreement may be used for general corporate purposes, including working capital and permitted acquisitions, and each of the Borrowers has agreed to be jointly and severally liable for the obligations of the other Borrowers under the New Credit Agreement.
	The New Credit Agreement contains customary events of default. If an event of default occurs and is continuing, the Borrowers might be required immediately to repay all amounts outstanding under the New Credit Agreement. Lenders holding at least a majority of the loans and commitments under the New Credit Agreement may elect to accelerate the maturity of the loans and/or terminate the commitments under the New Credit Agreement upon the occurrence and during the continuation of an event of default.
	Included in the New Credit Agreement is a provision that allows up to $17.5 million of the revolving credit facility to be used for LOC’s, subject to availability. On March 7, 2014, the $0.2 million LOC outstanding under the original $150.0 million Credit Agreement was transferred to the New Credit Agreement. As of September 30, 2014 and December 31, 2013, there were no borrowings outstanding and $0.2 million in LOC’s against the Credit Facility.
	Junior Subordinated Debentures
	On July 16, 2014, Argo Group US, Inc. purchased the outstanding PXRE Capital Trust V $20,000,000 Junior Subordinated Debt Securities (“Capital Trust V”) at a discount equal to 90.0% of the principal amount plus accrued and unpaid interest through the date of purchase for a total price of $18.2 million. As of September 30, 2014, the Capital Trust V has not yet been redeemed and interest will continue to accrue and be paid until the redemption date. In accordance with ASC Topic 405, “Liabilities,” we have eliminated the outstanding debt, associated interest and intercompany balances related to the purchase of the Capital Trust V since the purchase by Argo Group Us, Inc. In essence, this reduces our outstanding debt related to the Junior Subordinated Debentures.

Disclosures_about_Fair_Value_o

Disclosures about Fair Value of Financial Instruments	9 Months Ended
Disclosures about Fair Value of Financial Instruments	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Disclosures about Fair Value of Financial Instruments	'
	7	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, 2014 and December 31, 2013, the carrying values of premiums receivable over 90 days were $17.9 million and $9.8 million, respectively. Included in “Reinsurance recoverables” in our Consolidated Balance Sheets at September 30, 2014 and December 31, 2013, are amounts that are due from third-party trade capital providers associated with the operations of Argo International. Upon settlement, the receivable is offset against the liability also reflected in our accompanying Consolidated Balance Sheets. At September 30, 2014 and December 31, 2013, the payable was in excess of the receivable. Of our reinsurance recoverable on paid losses, excluding amounts attributable to Argo International’s third-party trade capital providers, at September 30, 2014 and December 31, 2013, the carrying values over 90 days were $13.2 million and $22.2 million, respectively. Our methodology for establishing our allowances for doubtful accounts includes specifically identifying all potential uncollectible balances regardless of aging. At September 30, 2014 and December 31, 2013, the allowance for doubtful accounts for premiums receivable was $4.9 million and $4.5 million, and the allowance for doubtful accounts for reinsurance recoverables on paid losses was $2.0 million and $1.6 million, respectively. Premiums receivable over 90 days were secured by collateral in the amount of $0.3 million and $0.4 million at September 30, 2014 and December 31, 2013, respectively.
	At September 30, 2014 and December 31, 2013, 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, 2014				December 31, 2013
	(in millions)		Carrying		Fair Value		Carrying		Fair Value
	(in millions)		Amount		Fair Value		Amount		Fair Value
	Junior subordinated debentures		$	172.7	$	155.5	$	193.3	$	155.5
	Senior unsecured fixed rate notes			143.8		132.3		143.8		116.2
	Other indebtedness:
	Floating rate loan stock			63.8		57.4		65.5		52.7
	Note payable			0.6		0.6		0.8		0.6

			$	380.9	$	345.8	$	403.4	$	325

Shareholders_Equity

Shareholders' Equity	9 Months Ended
Shareholders' Equity	Sep. 30, 2014
Equity [Abstract]	'
Shareholders' Equity	'
	8	Shareholders’ Equity
	On August 5, 2014, 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, 2014, we paid $4.7 million to our shareholders of record on September 1, 2014.
	On August 6, 2013, our Board of Directors declared a quarterly cash dividend in the amount of $0.15 on each share of common stock outstanding. On September 20, 2013, we paid $4.0 million to our shareholders of record on September 2, 2013.
	On November 13, 2007, our Board of Directors authorized the repurchase of up to $150.0 million of Argo Group’s common shares. On February 18, 2011, our Board of Directors authorized the repurchase of up to $150.0 million of our common shares (“2011 Repurchase Authorization”). The 2011 Repurchase Authorization superseded the November 13, 2007 repurchase program such that no further amounts could be repurchased under the repurchase program approved in 2007. On November 5, 2013, our Board of Directors authorized the repurchase of up to $150.0 million of our common shares (“2013 Repurchase Authorization”). The 2013 Repurchase Authorization superseded the 2011 Repurchase Authorization such that no further amounts could be repurchased under the 2011 Repurchase Authorization. As of September 30, 2014, availability under the 2013 Repurchase Authorization for future repurchases of our common shares was $101.5 million.
	For the three and nine months ended September 30, 2014, we repurchased a total of 206,710 common shares and 882,010 common shares, respectively, for $10.8 million and $42.2 million, respectively. A summary of activity from January 1, 2014 through September 30, 2014 follows.
	For the three and nine months ended September 30, 2014, we repurchased 98,108 common shares and 301,758 common shares, respectively, on the open market for $5.2 million and $14.9 million, respectively. In 2014, we repurchased shares under Securities Exchange Act of 1934 Rule 10b5-1 trading plans as follows:


	Date Trading		2014		Number of		Average Price of		Total Cost		Repurchase
	Plan Initiated		Purchase Period		Shares Repurchased		Shares Repurchased		(in millions)		Authorization Year
	12/17/13			02/04/14-02/12/14		15,789	$	43.28	$	0.7		2013
	3/18/14			03/18/14-04/28/14		436,867	$	45.81	$	20		2013
	6/13/14			06/17/14-08/04/14		41,362	$	49.94	$	2.1		2013
	9/12/14			09/16/14-09/30/14		86,234	$	52.17	$	4.5		2013

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
Accumulated Other Comprehensive Income (Loss)	Sep. 30, 2014
Equity [Abstract]	'
Accumulated Other Comprehensive Income (Loss)	'
	9	Accumulated Other Comprehensive Income (Loss)
	In February 2013, the FASB issued ASU 2013-02 that amends ASC 220, “Comprehensive Income.” An entity is required to report the effect of significant reclassifications, by component, out of accumulated other comprehensive income (loss) on the respective line items in net income if the item is required under GAAP to be reclassified in its entirety in the same reporting period. Effective January 1, 2013, we adopted the update prospectively.

	A summary of changes in accumulated other comprehensive income (loss), net of taxes (where applicable) by component for the nine months ended September 30, 2014 and 2013 is presented in the following tables:


	(in millions)		Foreign Currency			Unrealized			Defined Benefit			Total
			Translation			Holding Gains			Pension Plans
			Adjustments			on Securities
	Beginning balance, January 1, 2014		$	(11.5	)	$	163.9		$	(4.6	)	$	147.8
	Other comprehensive income before reclassifications			(1.9	)		5.4			0			3.5
	Amounts reclassified from accumulated other comprehensive income			0			(14.8	)		0			(14.8	)

	Net current-period other comprehensive income			(1.9	)		(9.4	)		0			(11.3	)

	Ending balance, September 30, 2014		$	(13.4	)	$	154.5		$	(4.6	)	$	136.5



	(in millions)		Foreign Currency			Unrealized			Defined Benefit			Total
			Translation			Holding Gains			Pension Plans
			Adjustments			on Securities
	Beginning balance, January 1, 2013		$	(8.7	)	$	204.1		$	(5.9	)	$	189.5
	Other comprehensive loss before reclassifications			(2.2	)		(23.9	)		0			(26.1	)
	Amounts reclassified from accumulated other comprehensive loss			0			(11.6	)		0			(11.6	)

	Net current-period other comprehensive loss			(2.2	)		(35.5	)		0			(37.7	)

	Ending balance, September 30, 2013		$	(10.9	)	$	168.6		$	(5.9	)	$	151.8

	The amounts reclassified from accumulated other comprehensive income (loss) shown in the above table have been included in the following captions in our Consolidated Statements of Income:


			For the Three Months						For the Nine Months
			Ended September 30,						Ended September 30,
	(in millions)		2014			2013			2014			2013
	Unrealized gains and losses on securities
	Net realized investment gains		$	(5.8	)	$	(3.3	)	$	(22.0	)	$	(18.3	)
	Provision for income taxes			4.1			2			7.2			6.7

	Net of taxes		$	(1.7	)	$	(1.3	)	$	(14.8	)	$	(11.6	)

Net_Income_Per_Common_Share

Net Income Per Common Share	9 Months Ended
Net Income Per Common Share	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Net Income Per Common Share	'
	10	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				For the Nine Months
			Ended September 30,				Ended September 30,
	(in millions, except number of shares and per share amounts)		2014		2013		2014		2013
	Net income		$	44.7	$	31	$	123.5	$	95.4
	Weighted average common shares outstanding - basic			25,956,599		26,682,176		26,203,819		26,961,792
	Effect of dilutive securities:
	Equity compensation awards			480,334		1,137,374		466,357		1,031,543

	Weighted average common shares outstanding - diluted			26,436,933		27,819,550		26,670,176		27,993,335

	Net income per common share - basic		$	1.72	$	1.16	$	4.71	$	3.54

	Net income per common share - diluted		$	1.69	$	1.12	$	4.63	$	3.41

	Excluded from the weighted average common shares outstanding calculation at September 30, 2014 and 2013 are 8,440,355 shares and 7,408,601 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, 2014, equity compensation awards to purchase 1,879 shares of common stock were excluded from the computation of diluted net income per common share as these instruments were anti-dilutive. These instruments expire at varying times from 2014 through 2016. For the three and nine months ended September 30, 2013, equity compensation awards to purchase 58,784 shares of common stock were excluded from the computation of diluted net income per common share as these instruments were anti-dilutive. These instruments expire at varying times from 2013 through 2020.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	9 Months Ended
Supplemental Cash Flow Information	Sep. 30, 2014
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Information	'
	11	Supplemental Cash Flow Information
	Income taxes paid. We paid income taxes of $23.8 million and $14.1 million during the nine months ended September 30, 2014 and 2013, respectively.
	Interest paid. Interest paid was as follows:


			For the Nine Months
			Ended September 30,
	(in millions)		2014		2013
	Senior unsecured fixed rate notes		$	7	$	7
	Junior subordinated debentures			5.8		6
	Other indebtedness			2.3		2.1

	Total interest paid		$	15.1	$	15.1

Sharebased_Compensation

Share-based Compensation	9 Months Ended
Share-based Compensation	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Share-based Compensation	'
	12	Share-based Compensation
	The fair value method of accounting is used for equity-based compensation plans. Under the fair value method, compensation cost is measured based on the fair value of the award at the measurement date and recognized over the requisite service period. We use the Black-Scholes model to estimate the fair values on the measurement date for share options and share appreciation rights (“SARs”). The Black-Scholes model uses several assumptions to value a share award. The volatility assumption is based on the historical change in Argo Group’s stock price over the previous five years preceding the measurement date. The risk-free rate of return assumption is based on the five-year U.S. Treasury constant maturity rate on the measurement date. The expected award life is based upon the average holding period over the history of the incentive plan. The expected dividend yield is based on our history and expected dividend payouts.
	The following table summarizes the assumptions we used for the nine months ended September 30, 2014 and 2013:


			2014			2013
	Risk-free rate of return			1.77	%		1.44	%
	Expected dividend yields			1.49	%		1.55	%
	Expected award life (years)			4.67			4.92
	Expected volatility			22.84	%		31.12	%
	Argo Group’s 2014 Long-Term Incentive Plan
	In November 2007, the shareholders of Argo Group approved the 2007 Long-Term Incentive 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, 1,789,004 shares remained available for grant under the 2007 Long-Term Incentive Plan. In May 2014, the shareholders of Argo Group approved the 2014 Long-Term Incentive Plan (the “2014 Plan”), which provides for an additional 2.8 million shares of our common stock to be available for issuance to executives, non-employee directors and other key employees. The share awards may be in the form of share options, SARs, restricted shares, restricted share awards, restricted share units (“RSU”) 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 2014 Plan; 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 and non-qualified share options. Share options are required to have an exercise price that is not less than the market value on the date of grant. We are prohibited from repricing the options. The term of the share options cannot exceed seven years from the grant date.
	A summary of restricted share activity as of September 30, 2014 and changes during the nine months then ended is as follows:


			Shares			Weighted-Average
						Grant Date
						Fair Value
	Outstanding at January 1, 2014			257,975		$	32.97
	Granted			107,696		$	44.93
	Vested and issued			(58,680	)	$	31.62
	Expired or forfeited			(35,511	)	$	33.08

	Outstanding at September 30, 2014			271,480		$	37.99

	The restricted shares vest over two to four years. Expense recognized under this plan for the restricted shares was $0.8 million and $2.2 million for the three and nine months ended September 30, 2014, respectively, as compared to $0.6 million and $2.2 million for the three and nine months ended September 30, 2013, 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, 2014, there was $7.3 million of total unrecognized compensation cost related to restricted share compensation arrangements granted by Argo Group.
	A summary of stock-settled SARs activity as of September 30, 2014 and changes during the nine months then ended is as follows:


			Shares			Weighted-Average
			Shares			Exercise Price
	Outstanding at January 1, 2014			1,288,698		$	29.47
	Granted			188,273		$	43.23
	Exercised			(107,979	)	$	29.4
	Expired or forfeited			(68,523	)	$	32.95

	Outstanding at September 30, 2014			1,300,469		$	31.28

	The stock-settled SARs vest over a one to four year period. Upon exercise of the stock-settled SARs, the employee is entitled to receive shares of our common stock equal to the appreciation of the stock as compared to the exercise price. Expense recognized for the stock-settled SARs was $0.3 million and $1.6 million for the three and nine months ended September 30, 2014, respectively, and $0.8 million and $2.1 million for the three and nine months ended September 30, 2013, respectively. As of September 30, 2014, there was $3.6 million of total unrecognized compensation cost related to stock-settled SARs outstanding.
	A summary of cash-settled SARs activity as of September 30, 2014 and changes during the nine months then ended is as follows:


			Shares			Weighted-Average
			Shares			Exercise Price
	Outstanding at January 1, 2014			1,743,758		$	33
	Granted			756,853		$	44.28
	Exercised			(386,615	)	$	30.94
	Expired or forfeited			(170,195	)	$	35.49

	Outstanding at September 30, 2014			1,943,801		$	37.58

	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 $1.2 million and $9.2 million for the three and nine months ended September 30, 2014, respectively, and $1.7 million and $12.7 million for the three and nine months ended September 30, 2013, respectively. As of September 30, 2014, there was $10.2 million of total unrecognized compensation cost related to cash-settled SARs outstanding.

Underwriting_Acquisition_and_I

Underwriting, Acquisition and Insurance Expenses	9 Months Ended
Underwriting, Acquisition and Insurance Expenses	Sep. 30, 2014
Text Block [Abstract]	'
Underwriting, Acquisition and Insurance Expenses	'
	13	Underwriting, Acquisition and Insurance Expenses
	Underwriting, acquisition and insurance expenses were as follows:


			For the Three Months						For the Nine Months
			Ended September 30,						Ended September 30,
	(in millions)		2014			2013			2014			2013
	Commissions		$	59.8		$	57.2		$	178		$	174.7
	General expenses			69			65.4			211.9			200.8
	Premium taxes, boards and bureaus			7.2			6.8			19.5			19.7

				136			129.4			409.4			395.2
	Net deferral amortization of policy acquisition costs			(2.2	)		(2.7	)		(10.1	)		(17.2	)

	Total underwriting, acquisition and insurance expenses		$	133.8		$	126.7		$	399.3		$	378

	Included in general expenses for the three months ended September 30, 2014 and 2013 was $2.2 million and $3.2 million, respectively, and $13.3 million and $17.6 million for the nine months ended September 30, 2014 and 2013, respectively, of total equity compensation expense.

Income_Taxes

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	14	Income Taxes
	We are incorporated under the laws of Bermuda and, under current Bermuda law, are not obligated to pay any taxes in Bermuda based upon income or capital gains. We have received an undertaking from the Supervisor of Insurance in Bermuda pursuant to the provisions of the Exempted Undertakings Tax Protection Act, 2011, which exempts us from any Bermuda taxes computed on profits, income or any capital asset, gain or appreciation or any tax in the nature of estate duty or inheritance tax, at least until the year 2035.
	We do not consider ourselves to be engaged in a trade or business in the United States or the United Kingdom and, accordingly, do not expect to be subject to direct United States or United Kingdom income taxation.
	We have subsidiaries based in the United Kingdom that are subject to the tax laws of that country. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Six of the United Kingdom subsidiaries are deemed to be engaged in business in the United States, and therefore, are subject to United States corporate tax in respect of a proportion of their United States underwriting business only. Relief is available against the United Kingdom tax liabilities in respect of overseas taxes paid that arise from the underwriting business. Corporate income tax losses incurred in the United Kingdom can be carried forward, for application against future income, indefinitely. Our United Kingdom subsidiaries file separate United Kingdom income tax returns.
	We have subsidiaries based in the United States that are subject to United States tax laws. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Our United States subsidiaries file a consolidated United States federal income tax return.
	We also have operations in Belgium, Switzerland, Brazil, France, Malta, Spain, Singapore 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								For the Nine Months
			Ended September 30,								Ended September 30,
	(in millions)		2014				2013				2014				2013
	Current tax provision		$	(15.0	)		$	3.5			$	(10.7	)		$	13.4
	Deferred tax provision related to:
	Future tax deductions			19.7				(2.4	)			52.9				2
	Valuation allowance change			(1.1	)			0.8				(30.0	)			2.4

	Income tax provision		$	3.6			$	1.9			$	12.2			$	17.8

	Our expected income tax provision computed on pre-tax income (loss) at the weighted average tax rate has been calculated as the sum of the pre-tax income (loss) in each jurisdiction multiplied by that jurisdiction’s applicable statutory tax rate. For the three and nine months ended September 30, 2014 and 2013, pre-tax income (loss) attributable to our operations and the operations’ effective tax rates were as follows:


			For the Three Months Ended September 30,
			2014								2013
	(in millions)		Pre-tax				Effective Tax				Pre-tax				Effective Tax
	(in millions)		Income (Loss)				Rate				Income (Loss)				Rate
	Bermuda		$	27.5				0	%		$	14.2				0	%
	United States			13.5				16.2	%			19.6				22.9	%
	United Kingdom			9.2				15.4	%			1.6				-164.7	%
	Belgium			(0.1	)			-7.9	%			0.1				91.6	%
	Brazil			(1.2	)			0	%			(1.5	)			0	%
	United Arab Emirates			0				0	%			(0.4	)			0	%
	Ireland			0				0	%			(0.1	)			0	%
	Malta			(0.8	)			0	%			(0.6	)			0	%
	Switzerland			0.2				4.8	%			0	(1)			19.7	%

	Pre-tax income		$	48.3							$	32.9


	(1)	Pre-tax income for the respective period was less than $0.1 million.


			For the Nine Months Ended September 30,
			2014								2013
	(in millions)		Pre-tax				Effective Tax				Pre-tax				Effective Tax
	(in millions)		Income (Loss)				Rate				Income (Loss)				Rate
	Bermuda		$	74.3				0	%		$	34.2				0	%
	United States			49.2				20.9	%			68.6				23.5	%
	United Kingdom			11.1				17.1	%			18.3				9.2	%
	Belgium			(0.1	)			-32.4	%			0.1				26.9	%
	Brazil			3.9				0	%			(6.2	)			0	%
	United Arab Emirates			(0.9	)			0	%			(0.4	)			0	%
	Ireland			0				0	%			(0.1	)			0	%
	Malta			(1.8	)			0	%			(1.3	)			0	%
	Switzerland			0	(2)			24.2	%			0	(2)			21	%

	Pre-tax income		$	135.7							$	113.2


	(2)	Pre-tax income for the respective period 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								For the Nine Months
		Ended September 30,								Ended September 30,
(in millions)		2014				2013				2014				2013
Income tax provision at expected rate		$	6.1			$	6.2			$	20.6			$	25.2
Tax effect of:
Tax-exempt interest			(1.1	)			(1.3	)			(3.4	)			(4.1	)
Dividends received deduction			(0.5	)			(0.7	)			(1.7	)			(1.8	)
Valuation allowance change			(1.1	)			0.8				(30.0	)			2.4
Other permanent adjustments, net			(0.1	)			(0.5	)			(1.0	)			(1.4	)
Adjustment for prior year tax return			(1.1	)			0				(1.1	)			0
Adjustment for annualized rate - United States			0.3				0.3				0.5				(0.1	)
Adjustment for annualized rate - Foreign			0.5				0				(1.4	)			0
Prior period adjustment to deferred			0.9				0				(0.2	)			0
United States state tax benefit			0				(0.1	)			0				(0.4	)
PXRE Reinsurance capital loss carryforward			0				0				29.8				0
Deferred tax rate reduction			(0.1	)			(1.3	)			(0.1	)			(1.3	)
Foreign exchange adjustments			(0.2	)			(1.7	)			(0.1	)			(1.3	)
Foreign withholding taxes			0				0.2				0.3				0.6

Income tax provision		$	3.6			$	1.9			$	12.2			$	17.8

Income tax provision (benefit) - Foreign		$	1.5			$	(2.6	)		$	2			$	1.7
Income tax provision - United States Federal			2.1				4.4				9.8				16.1
Income tax (benefit) provision - United States State			0				(0.1	)			0.1				(0.6	)
Foreign withholding tax - United States			0				0.2				0.3				0.6

Income tax provision		$	3.6			$	1.9			$	12.2			$	17.8

We recognize accrued interest and penalties, if any, within our global operations in “Interest expense” and “Underwriting, acquisition and insurance expenses,” respectively, in our Consolidated Statements of Income.
Our net deferred tax assets (liabilities) are supported by taxes paid in previous periods, reversal of the taxable temporary differences and recognition of future income. Management regularly evaluates the recoverability of the deferred tax assets and makes any necessary adjustments to them based upon any changes in management’s expectations of future taxable income. Realization of deferred tax assets is dependent upon our generation of sufficient taxable income in the future to recover tax benefits that cannot be recovered from taxes paid in the carryback period, which is generally two years for net operating losses and three years for capital losses for our United States operations. At September 30, 2014, we had a total net deferred tax liability of $29.4 million prior to any valuation allowance. Management has concluded that a valuation allowance is required for a portion of the tax effected net operating loss carryforward of $18.0 million from PXRE Corporation and for the tax effected net operating loss carryforward of $1.0 million from ARIS. The capital loss carryforward generated from the sale of PXRE Reinsurance Company expired on December 31, 2013. Of the PXRE Corporation loss carryforwards, $16.5 million will expire if not used by December 31, 2025 and $1.5 million will expire if not used by December 31, 2027. Of the ARIS loss carryforward, $0.2 million will expire if not used by December 31, 2027, $0.4 million will expire if not used by December 31, 2028 and $0.4 million will expire if not used by December 31, 2029. The valuation allowances have been established as Internal Revenue Code Section 382 limits the application of net operating loss and net capital loss carryforwards following an ownership change. The loss carryforwards available per year are $2.8 million as required by Internal Revenue Code Section 382. Further, due to cumulative losses since inception, management has concluded that a valuation allowance is required for the full amount of the tax effected net operating losses generated by our Brazil and Malta entities. Accordingly, a valuation allowance of $26.3 million is required as of September 30, 2014 of which $16.1 million relates to the PXRE Corporation and ARIS loss carryforwards, $8.1 million relates to Brazil operations and $2.1 million relates to Malta operations. For the nine months ended September 30, 2014, the valuation allowance was reduced by $29.8 million pertaining to the expiration of the PXRE Reinsurance Company capital loss carryforward, reduced by $0.7 million pertaining to the PXRE Corporation and ARIS loss carryforwards, increased by $0.2 million pertaining to our Brazil operations and increased by $0.3 million pertaining to our Malta operations.

We had no material unrecognized tax benefits as of September 30, 2014 and 2013. Our United States subsidiaries are no longer subject to U.S. federal and state income tax examinations by tax authorities for years before 2011. Our United Kingdom subsidiaries are no longer subject to United Kingdom income tax examinations by Her Majesty’s Revenue and Customs for years before 2011.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	15. 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 $42.4 million related to our limited partnership investments at September 30, 2014. These commitments will be funded as required by the partnership agreements.

Segment_Information

Segment Information	9 Months Ended
Segment Information	Sep. 30, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	16. Segment Information
	We are primarily engaged in underwriting property and casualty insurance and reinsurance. We have four ongoing reporting segments: Excess and Surplus Lines, Commercial Specialty, International Specialty and Syndicate 1200. Additionally, we have a Run-off Lines segment for certain products that we no longer underwrite.
	We consider many factors, including the nature of each segment’s insurance and reinsurance products, production sources, distribution strategies and the regulatory environment, in determining how to aggregate reporting segments.
	In evaluating the operating performance of our segments, we focus on core underwriting and investing results before the consideration of realized gains or losses from the sales of investments. Realized investment gains are reported as a component of the Corporate and Other segment, as decisions regarding the acquisition and disposal of securities reside with the investment function and are not under the control of the individual business segments. Identifiable assets by segment are those assets used in the operation of each segment.
	Revenue and income (loss) before income taxes for each segment were as follows:


			For the Three Months								For the Nine Months
			Ended September 30,								Ended September 30,
	(in millions)		2014				2013				2014				2013
	Revenue:
	Earned premiums
	Excess and Surplus Lines		$	121.2			$	120.6			$	363.9			$	334.4
	Commercial Specialty			72.7				74.6				215.5				225.1
	International Specialty			38				37.5				112.6				106.6
	Syndicate 1200			104.4				97.3				305.9				295.6
	Run-off Lines			1.3				0.5				1.5				0.5

	Total earned premiums			337.6				330.5				999.4				962.2
	Net investment income
	Excess and Surplus Lines			8.9				10.2				27.2				32.3
	Commercial Specialty			4.5				5.6				13.8				17.6
	International Specialty			2.3				2.4				6.1				6.4
	Syndicate 1200			2.1				2.5				7.9				8.1
	Run-off Lines			2.4				2.6				7.2				8.2
	Corporate and Other			0.6				0.8				2.5				4.7

	Total net investment income			20.8				24.1				64.7				77.3
	Fee income, net			1.6				0.3				0.1				0.5
	Net realized investment gains and other			12.9				9.1				42.5				29.6

	Total revenue		$	372.9			$	364			$	1,106.70			$	1,069.60



			For the Three Months								For the Nine Months
			Ended September 30,								Ended September 30,
	(in millions)		2014				2013				2014				2013
	Income (loss) before income taxes
	Excess and Surplus Lines		$	27.6			$	29.6			$	75.9			$	60.2
	Commercial Specialty			8				10.1				9.2				17.3
	International Specialty			4				0.5				16.4				8.1
	Syndicate 1200			8.8				8.5				34.7				26.7
	Run-off Lines			(8.3	)			(9.1	)			(17.6	)			(5.8	)

	Total segment income before taxes			40.1				39.6				118.6				106.5
	Corporate and Other			(4.7	)			(15.8	)			(25.4	)			(22.9	)
	Net realized investment gains and other			12.9				9.1				42.5				29.6

	Total income before income taxes		$	48.3			$	32.9			$	135.7			$	113.2

	The table below presents earned premiums by geographic location for the three and nine months ended September 30, 2014 and 2013. 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								For the Nine Months
			Ended September 30,								Ended September 30,
	(in millions)		2014				2013				2014				2013
	Bermuda		$	27			$	27.4			$	75.7			$	75.3
	Brazil			11				9.9				35.4				29.9
	Malta			0.5				0.5				1.6				1.3
	United Kingdom			104.4				97.7				305.9				296
	United States			194.7				195				580.8				559.7

Total earned premiums		$	337.6			$	330.5			$	999.4			$	962.2

The following table presents our identifiable assets.


(in millions)		September 30,				December 31,
(in millions)		2014				2013
Excess and Surplus Lines		$	2,383.80			$	2,252.20
Commercial Specialty			1,287.00				1,333.40
International Specialty			771.5				743.6
Syndicate 1200			1,287.20				1,638.80
Run-off Lines			586.2				555.9
Corporate and Other			72.9				67.1

Total		$	6,388.60			$	6,591.00

Included in total assets at September 30, 2014 and December 31, 2013 are $287.6 million and $386.8 million, respectively, in assets associated with trade capital providers.

Information_Provided_in_Connec

Information Provided in Connection with Outstanding Debt of Subsidiaries	9 Months Ended
	Sep. 30, 2014
Text Block [Abstract]	'
Information Provided in Connection with Outstanding Debt of Subsidiaries	'
	17. Information Provided in Connection with Outstanding Debt of Subsidiaries
	The following tables present condensed consolidating financial information at September 30, 2014 and December 31, 2013 and for the three and nine months ended September 30, 2014 and 2013, for Argo Group (the “Parent Guarantor”) and Argo Group US (the “Subsidiary Issuer”). The Subsidiary Issuer is an indirect 100 percent-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, 2014
	(in millions)


			Argo Group			Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
			International Holdings,			and Subsidiaries				and Eliminations (1)				Adjustments (2)
			Ltd (Parent Guarantor)			(Subsidiary Issuer)
	Assets
	Investments		$	1.9		$	2,847.80			$	1,262.00			$	0			$	4,111.70
	Cash			0			69				22.1				(18.0	)			73.1
	Accrued investment income			0			17.2				5				0				22.2
	Premiums receivable			0			161				235.7				0				396.7
	Reinsurance recoverables			0			1,188.70				(186.4	)			0				1,002.30
	Goodwill and other intangible assets, net			0			135.6				99.9				0				235.5
	Current income taxes receivable, net			0			25.3				4.7				0				30
	Deferred acquisition costs, net			0			58.4				71.6				0				130
	Ceded unearned premiums			0			100.9				126.1				0				227
	Other assets			10.4			104.1				52.6				(7.0	)			160.1
	Due from affiliates			7			(18.8	)			18.8				(7.0	)			0
	Intercompany note receivable			0			71.4				(71.4	)			0				0
	Investments in subsidiaries			1,710.80			0				0				(1,710.8	)			0

	Total assets		$	1,730.10		$	4,760.60			$	1,640.70			$	(1,742.8	)		$	6,388.60

	Liabilities and Shareholders’ Equity
	Reserves for losses and loss adjustment expenses		$	0		$	2,160.50			$	902.1			$	0			$	3,062.60
	Unearned premiums			0			453.1				412.3				0				865.4
	Funds held and ceded reinsurance payable, net			0			658.5				(419.7	)			0				238.8
	Long-term debt			49			288.7				63.8				(20.6	)			380.9
	Deferred tax liabilities, net			0			47.1				8.6				0				55.7
	Accrued underwriting expenses and other liabilities			13.3			93.5				51.5				0				158.3
	Intercompany note payable			40.9			0				0				(40.9	)			0

	Total liabilities			103.2			3,701.40				1,018.60				(61.5	)			4,761.70

	Total shareholders’ equity			1,626.90			1,059.20				622.1				(1,681.3	)			1,626.90

	Total liabilities and shareholders’ equity		$	1,730.10		$	4,760.60			$	1,640.70			$	(1,742.8	)		$	6,388.60


	(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, 2013
	(in millions)


			Argo Group			Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
			International Holdings,			and Subsidiaries				and Eliminations (1)				Adjustments (2)
			Ltd (Parent Guarantor)			(Subsidiary Issuer)
	Assets
	Investments		$	1.1		$	2,785.10			$	1,293.00			$	0			$	4,079.20
	Cash			0			132.1				25.3				0				157.4
	Accrued investment income			0			19.7				6				0				25.7
	Premiums receivable			0			150.8				197.6				0				348.4
	Reinsurance recoverables			0			1,145.90				117.6				0				1,263.50
	Goodwill and other intangible assets, net			0			137.4				102.4				0				239.8
	Current income taxes receivable, net			0			0.5				(0.5	)			0				0
	Deferred acquisition costs, net			0			55.6				58.3				0				113.9
Ceded unearned premiums			0			88.2				108.1				0				196.3
Other assets			4.6			97.8				64.4				0				166.8
Due from affiliates			3.1			1.5				(1.5	)			(3.1	)			0
Intercompany note receivable			0			87.4				(87.4	)			0				0
Investments in subsidiaries			1,625.20			0				0				(1,625.2	)			0

Total assets		$	1,634.00		$	4,702.00			$	1,883.30			$	(1,628.3	)		$	6,591.00

Liabilities and Shareholders’ Equity
Reserves for losses and loss adjustment expenses		$	0		$	2,157.00			$	1,073.30			$	0			$	3,230.30
Unearned premiums			0			425.5				353.6				0				779.1
Funds held and ceded reinsurance payable, net			0			642.4				(244.0	)			0				398.4
Long-term debt			49			288.9				65.5				0				403.4
Current income taxes payable, net			0			8.9				(3.7	)			0				5.2
Deferred tax liabilities, net			0			22.8				5.9				0				28.7
Accrued underwriting expenses and other liabilities			15.4			98.2				69.3				0				182.9
Intercompany note payable			6.6			0				0				(6.6	)			0

Total liabilities			71			3,643.70				1,319.90				(6.6	)			5,028.00

Total shareholders’ equity			1,563.00			1,058.30				563.4				(1,621.7	)			1,563.00

Total liabilities and shareholders’ equity		$	1,634.00		$	4,702.00			$	1,883.30			$	(1,628.3	)		$	6,591.00


(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd and all intercompany eliminations
(2)	Includes all Argo Group parent company eliminations
CONDENSED CONSOLIDATING STATEMENT OF INCOME
FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2014
(in millions)


		Argo Group			Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
		International Holdings,			and Subsidiaries				and Eliminations (1)				Adjustments (2)
		Ltd (Parent Guarantor)			(Subsidiary Issuer)
Premiums and other revenue:
Earned premiums		$	0		$	114.2			$	223.4			$	0			$	337.6
Net investment (loss) income			(0.1	)		13.6				7.3				0				20.8
Fee income, net			0			1.5				0.1				0				1.6
Net realized investment gains and other			0			9.2				3.7				0				12.9

Total revenue			(0.1	)		138.5				234.5				0				372.9

Expenses:
Losses and loss adjustment expenses			0			69.9				122				0				191.9
Underwriting, acquisition and insurance expenses			2.3			51.6				79.9				0				133.8
Interest expense			0.7			3.8				0.6				(0.2	)			4.9
Foreign currency exchange loss (gain)			0			0.3				(6.3	)			0				(6.0	)

Total expenses			3			125.6				196.2				(0.2	)			324.6

(Loss) income before income taxes			(3.1	)		12.9				38.3				0.2				48.3
Provision for income taxes			0			2.1				1.5				0				3.6

Net (loss) income before equity in earnings of subsidiaries			(3.1	)		10.8				36.8				0.2				44.7
Equity in undistributed earnings of subsidiaries			47.9			0				0				(47.9	)			0

Net income		$	44.8		$	10.8			$	36.8			$	(47.7	)		$	44.7


(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations
(2)	Includes all Argo Group parent company eliminations


CONDENSED CONSOLIDATING STATEMENT OF INCOME
FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2013
(in millions)


		Argo Group			Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
		International Holdings,			and Subsidiaries				and Eliminations (1)				Adjustments (2)
		Ltd (Parent Guarantor)			(Subsidiary Issuer)
Premiums and other revenue:
Earned premiums		$	0		$	105.2			$	225.3			$	0			$	330.5
Net investment income			0			16.7				7.7				(0.3	)			24.1
Fee income, net			0			(0.6	)			0.9				0				0.3
Net realized investment gains and other			0			7.2				1.9				0				9.1

Total revenue			0			128.5				235.8				(0.3	)			364

Expenses:
Losses and loss adjustment expenses			0			65.9				125				0				190.9
Other reinsurance-related expenses			0			(2.9	)			7.5				0				4.6
Underwriting, acquisition and insurance expenses			5.8			42.1				78.8				0				126.7
Interest expense			0.7			3.8				0.9				(0.3	)			5.1
Foreign currency exchange loss (gain)			0			(0.1	)			3.9				0				3.8

Total expenses			6.5			108.8				216.1				(0.3	)			331.1

(Loss) income before income taxes			(6.5	)		19.7				19.7				0				32.9
Provision for income taxes			0			4.4				(2.5	)			0				1.9

Net (loss) income before equity in earnings of subsidiaries			(6.5	)		15.3				22.2				0				31
Equity in undistributed earnings of subsidiaries			37.5			0				0				(37.5	)			0

Net income		$	31		$	15.3			$	22.2			$	(37.5	)		$	31


(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations
(2)	Includes all Argo Group parent company eliminations
CONDENSED CONSOLIDATING STATEMENT OF INCOME
FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2014
(in millions)


		Argo Group			Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
		International Holdings,			and Subsidiaries				and Eliminations (1)				Adjustments (2)
		Ltd (Parent Guarantor)			(Subsidiary Issuer)
Premiums and other revenue:
Earned premiums		$	0		$	343.7			$	655.7			$	0			$	999.4
Net investment (loss) income			(0.3	)		42.4				22.6				0				64.7
Fee (expense) income, net			0			(1.5	)			1.6				0				0.1
Net realized investment gains and other			0			34.6				7.9				0				42.5

Total revenue			(0.3	)		419.2				687.8				0				1,106.70

Expenses:
Losses and loss adjustment expenses			0			211.2				348.3				0				559.5
Underwriting, acquisition and insurance expenses			12.5			147.9				238.9				0				399.3
Interest expense			1.8			11.4				2.1				(0.3	)			15
Foreign currency exchange loss (gain)			0			0.1				(2.9	)			0				(2.8	)

Total expenses			14.3			370.6				586.4				(0.3	)			971

(Loss) income before income taxes			(14.6	)		48.6				101.4				0.3				135.7
Provision for income taxes			0			10.2				2				0				12.2

Net (loss) income before equity in earnings of subsidiaries			(14.6	)		38.4				99.4				0.3				123.5
Equity in undistributed earnings of subsidiaries			138.1			0				0				(138.1	)			0

Net income		$	123.5		$	38.4			$	99.4			$	(137.8	)		$	123.5


(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations
(2)	Includes all Argo Group parent company eliminations

CONDENSED CONSOLIDATING STATEMENT OF INCOME
FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2013
(in millions)


		Argo Group			Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
		International Holdings,			and Subsidiaries				and Eliminations (1)				Adjustments (2)
		Ltd (Parent Guarantor)			(Subsidiary Issuer)
Premiums and other revenue:
Earned premiums		$	0		$	321.2			$	641			$	0			$	962.2
Net investment income			0			57.2				21				(0.9	)			77.3
Fee income, net			0			(1.9	)			2.4				0				0.5
Net realized investment gains (losses) and other			0			32.8				(3.2	)			0				29.6

Total revenue			0			409.3				661.2				(0.9	)			1,069.60

Expenses:
Losses and loss adjustment expenses			0			194.9				359.2				0				554.1
Other reinsurance-related expenses			0			0				14.4				0				14.4
Underwriting, acquisition and insurance expenses			18.3			134.3				225.4				0				378
Interest expense			2.3			11.4				2.3				(0.9	)			15.1
Foreign currency exchange loss (gain)			0			0.1				(5.3	)			0				(5.2	)

Total expenses			20.6			340.7				596				(0.9	)			956.4

(Loss) income before income taxes			(20.6	)		68.6				65.2				0				113.2
Provision for income taxes			0			16				1.8				0				17.8

Net (loss) income before equity in earnings of subsidiaries			(20.6	)		52.6				63.4				0				95.4
Equity in undistributed earnings of subsidiaries			116			0				0				(116.0	)			0

Net income		$	95.4		$	52.6			$	63.4			$	(116.0	)		$	95.4


(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations
(2)	Includes all Argo Group parent company eliminations
CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2014
(in millions)


		Argo Group			Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
		International Holdings,			and Subsidiaries				and Eliminations (1)				Adjustments (2)
		Ltd (Parent Guarantor)			(Subsidiary Issuer)
Net cash flows from operating activities		$	(16.5	)	$	11.8			$	70			$	6.4			$	71.7

Cash flows from investing activities:
Proceeds from sales of investments			0			609.2				366.9				0				976.1
Proceeds from maturities and mandatory calls of investments			0			148				95.6				0				243.6
Purchases of investments			0			(773.1	)			(491.7	)			0				(1,264.8	)
Change in short-term investments and foreign regulatory deposits			0.1			(12.5	)			18.4				0				6
Settlements of foreign currency exchange forward contracts			(0.5	)		0				1.1				0				0.6
Issuance of intercompany note, net			0			14.5				(48.5	)			34				0
Purchase of fixed assets			(7.0	)		(17.7	)			4.4				(6.4	)			(26.7	)
Other, net			0			(2.4	)			(19.1	)			0				(21.5	)

Cash (used) provided by investing activities			(7.4	)		(34.0	)			(72.9	)			27.6				(86.7	)

Cash flows from financing activities:
Borrowings under intercompany note, net			34			0				0				(34.0	)			0
Redemption of trust preferred securities, net			0			0				0				(18.0	)			(18.0	)
Payment on note payable			0			(0.1	)			0				0				(0.1	)
Activity under stock incentive plans			3.3			0				0				0				3.3
Repurchase of Company’s common shares			0			(40.9	)			0				0				(40.9	)
Excess tax expense from share-based payment arrangements			0			0.1				0				0				0.1
Payment of cash dividends to common shareholders			(13.4	)		0				0				0				(13.4	)

Cash provided (used) by financing activities			23.9			(40.9	)			0				(52.0	)			(69.0	)

Effect of exchange rate changes on cash			0			0				(0.3	)			0				(0.3	)

Change in cash			0			(63.1	)			(3.2	)			(18.0	)			(84.3	)
Cash, beginning of period			0			132.1				25.3				0				157.4

Cash, end of period		$	0		$	69			$	22.1			$	(18.0	)		$	73.1


(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd and all intercompany eliminations
(2)	Includes all Argo Group parent company eliminations

CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2013
(in millions)


		Argo Group			Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
		International Holdings,			and Subsidiaries				and Eliminations (1)				Adjustments (2)
		Ltd (Parent Guarantor)			(Subsidiary Issuer)
Net cash flows from operating activities		$	(15.5	)	$	75.9			$	(63.4	)		$	0			$	(3.0	)

Cash flows from investing activities:
Proceeds from sales of investments			0			863.2				515.6				0				1,378.80
Proceeds from maturities and mandatory calls of investments			0			139				85.2				0				224.2
Purchases of investments			0			(942.4	)			(464.9	)			0				(1,407.3	)
Change in short-term investments and foreign regulatory deposits			(0.8	)		(38.5	)			(36.2	)			0				(75.5	)
Settlements of foreign currency exchange forward contracts			1.9			0				(8.3	)			0				(6.4	)
Issuance of intercompany note, net			0			0				(24.9	)			24.9				0
Purchase of fixed assets			0			(17.7	)			(1.4	)			0				(19.1	)
Other, net			(0.1	)		4.4				0.2				0				4.5

Cash provided by investing activities			1			8				65.3				24.9				99.2

Cash flows from financing activities:
Borrowings under intercompany note, net			24.9			0				0				(24.9	)			0
Activity under stock incentive plans			1.4			0				0				0				1.4
Repurchase of Company’s common shares			0			(40.1	)			0				0				(40.1	)
Excess tax expense from share-based payment arrangements			0			(0.2	)			0.4				0				0.2
Payment of cash dividends to common shareholders			(11.8	)		0				0				0				(11.8	)

Cash provided (used) by financing activities			14.5			(40.3	)			0.4				(24.9	)			(50.3	)

Effect of exchange rate changes on cash			0			0				(0.1	)			0				(0.1	)

Change in cash			(0.0	)		43.6				2.2				0				45.8
Cash, beginning of period			0			73.9				21.9				0				95.8

Cash, end of period		$	(0.0	)	$	117.5			$	24.1			$	0			$	141.6


(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, 2014
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, 2013, filed with the Securities and Exchange Commission on February 28, 2014.
	The interim financial information as of, and for the three and nine months ended, September 30, 2014 and 2013 is unaudited. However, in the opinion of management, the interim information includes all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results presented for the interim periods. The operating results for the interim periods are not necessarily indicative of the results to be expected for the full year. All significant intercompany amounts have been eliminated in consolidation. Certain amounts in prior years’ financial statements have been reclassified to conform to the current presentation.
10% Stock Dividend	'
	10% Stock Dividend
	On May 7, 2013, our Board of Directors declared a 10% stock dividend, payable on June 17, 2013, to shareholders of record at the close of business on June 3, 2013. As a result of the stock dividend, 2,447,839 additional shares were issued. Cash was paid in lieu of fractional shares of our common shares. All references to share and per share amounts in this document and related disclosures have been adjusted to reflect the stock dividend for all periods presented.

Investments_Tables

Investments (Tables)	9 Months Ended
Investments (Tables)	Sep. 30, 2014
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, 2014		Amortized			Gross			Gross			Fair
	(in millions)		Cost			Unrealized			Unrealized			Value
						Gains			Losses
	Fixed maturities
	USD denominated:
	U.S. Governments		$	209.8		$	1.5		$	0.5		$	210.8
	Non-U.S. Governments			76.9			0.6			0.5			77
	Obligations of states and political subdivisions			485.6			24.2			0.6			509.2
	Credit-Financial			489.1			12.8			1.3			500.6
	Credit-Industrial			461			10.3			2.8			468.5
	Credit-Utility			146.8			4.3			0.7			150.4
	Structured securities:
	CMO/MBS-agency (1)			179.4			8.2			0.9			186.7
	CMO/MBS-non agency			13.7			0.9			0			14.6
	CMBS (2)			163.8			2.1			0.2			165.7
	ABS-residential (3)			5.2			0			0.3			4.9
	ABS-non residential			209.2			0.8			0.3			209.7
	Foreign denominated:
	Governments			140.4			1.8			7.4			134.8
	Credit			217.7			3			12.7			208

	Total fixed maturities			2,798.60			70.5			28.2			2,840.90
	Equity securities			318.7			195.2			2.6			511.3
	Other investments			398			7.3			2			403.3
	Short-term investments			356.2			0			0			356.2

	Total investments		$	3,871.50		$	273		$	32.8		$	4,111.70



	December 31, 2013		Amortized			Gross			Gross			Fair
	(in millions)		Cost			Unrealized			Unrealized			Value
						Gains			Losses
	Fixed maturities
	USD denominated:
	U.S. Governments		$	273.4		$	2.4		$	0.5		$	275.3
	Non-U.S. Governments			60.9			0.3			1			60.2
	Obligations of states and political subdivisions			563.7			22.9			8.8			577.8
	Credit-Financial			426.3			15.4			1.8			439.9
	Credit-Industrial			385.5			13.8			2.2			397.1
	Credit-Utility			162			5.4			0.8			166.6
	Structured securities:
	CMO/MBS-agency (1)			219.4			9.2			1.7			226.9
	CMO/MBS-non agency			19.4			0.8			0			20.2
	CMBS (2)			162.7			3.1			1			164.8
	ABS-residential (3)			6.8			0.3			0.5			6.6
	ABS-non residential			116.8			0.5			0.1			117.2
	Foreign denominated:
	Governments			207.7			4.9			5.9			206.7
	Credit			155.5			4.4			4.8			155.1

	Total fixed maturities			2,760.10			83.4			29.1			2,814.40
	Equity securities			346.9			188.6			1.2			534.3
	Other investments			377.4			2.8			1.3			378.9
	Short-term investments			351.6			0			0			351.6

	Total investments		$	3,836.00		$	274.8		$	31.6		$	4,079.20


	(1)	Collateralized mortgage obligations/mortgage-backed securities (“CMO/MBS”).
(2)	Commercial mortgage-backed securities (“CMBS”).
(3)	Asset-backed securities (“ABS”).
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, 2014, by contractual maturity, were as follows:


	(in millions)		Amortized			Fair
	(in millions)		Cost			Value
	Due in one year or less		$	255.7		$	254.2
	Due after one year through five years			1,329.30			1,343.20
	Due after five years through ten years			472.9			488.2
	Thereafter			169.4			173.7
	Structured securities			571.3			581.6

	Total		$	2,798.60		$	2,840.90

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, 2014		Less Than One Year						One Year or Greater						Total
	(in millions)		Fair			Unrealized			Fair			Unrealized			Fair			Unrealized
			Value			Losses			Value			Losses			Value			Losses
	Fixed maturities
	USD denominated:
	U.S. Governments		$	59.5		$	0.3		$	16.3		$	0.2		$	75.8		$	0.5
	Non-U.S. Governments			28.3			0.1			7.5			0.4			35.8			0.5
	Obligations of states and political subdivisions			16.4			0.1			27.9			0.5			44.3			0.6
	Credit-Financial			149.1			1.1			14.3			0.2			163.4			1.3
	Credit-Industrial			222.5			2.5			13.5			0.3			236			2.8
	Credit-Utility (2)			42.5			0.7			1.9			0			44.4			0.7
	Structured securities:
	CMO/MBS-agency			23.8			0.1			17.1			0.8			40.9			0.9
	CMBS			29.8			0.1			6.6			0.1			36.4			0.2
	ABS-residential			0			0			3.4			0.3			3.4			0.3
	ABS-non residential (2)			106.9			0.3			3.6			0			110.5			0.3
	Foreign denominated:
	Governments			111.5			6.9			17			0.5			128.5			7.4
	Credit			179.8			12.6			0.7			0.1			180.5			12.7

	Total fixed maturities			970.1			24.8			129.8			3.4			1,099.90			28.2
	Equity securities			32.1			2.6			0			0			32.1			2.6
	Other investments			(2.0	)		2			0			0			(2.0	)		2

	Total		$	1,000.20		$	29.4		$	129.8		$	3.4		$	1,130.00		$	32.8



	December 31, 2013		Less Than One Year						One Year or Greater						Total
	(in millions)		Fair			Unrealized			Fair			Unrealized			Fair			Unrealized
			Value			Losses			Value			Losses			Value			Losses
	Fixed maturities
	USD denominated:
	U.S. Governments		$	55.3		$	0.5		$	0		$	0		$	55.3		$	0.5
	Non-U.S. Governments			36.3			1			0			0			36.3			1
	Obligations of states and political subdivisions (2)			154.6			8.8			3.1			0			157.7			8.8
	Credit-Financial			88.7			1.7			2.4			0.1			91.1			1.8
	Credit-Industrial			85.7			2			2.9			0.2			88.6			2.2
	Credit-Utility			21.2			0.7			1.9			0.1			23.1			0.8
	Structured securities:
	CMO/MBS-agency			58.4			1.2			5.6			0.5			64			1.7
	CMBS (2)			24.2			1			1.1			0			25.3			1
	ABS-residential			0			0			3.6			0.5			3.6			0.5
	ABS-non residential (2)			59.1			0.1			2			0			61.1			0.1
	Foreign denominated:
	Governments			170.5			5.9			0			0			170.5			5.9
	Credit			125.3			4.8			0			0			125.3			4.8

	Total fixed maturities			879.3			27.7			22.6			1.4			901.9			29.1
	Equity securities			25.5			1.2			0			0			25.5			1.2
	Other investments			(1.4	)		1.3			0			0			(1.4	)		1.3
	Short-term investments (1)			4.5			0			0			0			4.5			0

	Total		$	907.9		$	30.2		$	22.6		$	1.4		$	930.5		$	31.6


	(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 gains (losses):


			For the Three Months						For the Nine Months
			Ended September 30,						Ended September 30,
	(in millions)		2014			2013			2014			2013
	Realized gains
	Fixed maturities		$	4.5		$	5.8		$	15.2		$	27.5
	Equity securities			0.7			7.2			16.1			15
	Other investments			13.6			11.2			36.5			28.9
	Short-term investments			0			0.1			0.1			0.1
	Other assets			2			0			2			0

	Gross realized investment gains			20.8			24.3			69.9			71.5
	Realized losses
	Fixed maturities			(1.1	)		(6.1	)		(8.7	)		(14.5	)
	Equity securities			(0.1	)		(0.1	)		(0.2	)		(0.8	)
	Other investments			(6.5	)		(8.6	)		(12.6	)		(24.1	)
	Short-term investments			0			(0.3	)		(0.3	)		(0.6	)
	Other assets			0			0			(4.0	)		0
	Other-than-temporary impairment losses on fixed maturities			0			0			(1.2	)		(0.3	)
	Other-than-temporary impairment losses on equity securities			(0.2	)		(0.1	)		(0.4	)		(1.6	)

	Gross realized investment and other losses			(7.9	)		(15.2	)		(27.4	)		(41.9	)

	Net realized investment gains and other		$	12.9		$	9.1		$	42.5		$	29.6

Financial Assets Measured at Fair Value on Recurring Basis	'
	Based on an analysis of the inputs, our financial assets measured at fair value on a recurring basis have been categorized as follows:


						Fair Value Measurements at Reporting Date Using
	(in millions)		September 30, 2014			Level 1 (a)			Level 2 (b)			Level 3 (c)
	Fixed maturities
	USD denominated:
	U.S. Governments		$	210.8		$	120.8		$	90		$	0
	Non-U.S. Governments			77			0			77			0
	Obligations of states and political subdivisions			509.2			0			509.2			0
	Credit-Financial			500.6			0			500.6			0
	Credit-Industrial			468.5			0			468.5			0
	Credit-Utility			150.4			0			150.4			0
	Structured securities:
	CMO/MBS-agency			186.7			0			186.7			0
	CMO/MBS-non agency			14.6			0			14.6			0
	CMBS			165.7			0			165.7			0
	ABS-residential			4.9			0			4.9			0
	ABS-non residential			209.7			0			209.7			0
	Foreign denominated:
	Governments			134.8			0			134.8			0
	Credit			208			0			208			0

	Total fixed maturities			2,840.90			120.8			2,720.10			0
	Equity securities			511.3			471			39.3			1
	Other investments			98.1			0			98.1			0
	Short-term investments			356.2			354.1			2.1			0

			$	3,806.50		$	945.9		$	2,859.60		$	1


	(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, 2013			Level 1 (a)			Level 2 (b)			Level 3 (c)
	Fixed maturities
	USD denominated:
	U.S. Governments		$	275.3		$	143.8		$	131.5		$	0
	Non-U.S. Governments			60.2			0			60.2			0
	Obligations of states and political subdivisions			577.8			0			577.8			0
	Credit-Financial			439.9			0			439.9			0
	Credit-Industrial			397.1			0			397.1			0
	Credit-Utility			166.6			0			166.6			0
	Structured securities:
	CMO/MBS-agency			226.9			0			226.9			0
	CMO/MBS-non agency			20.2			0			20.2			0
	CMBS			164.8			0			164.8			0
	ABS-residential			6.6			0			6.6			0
	ABS-non residential			117.2			0			117.2			0
	Foreign denominated:
	Governments			206.7			0			206.7			0
	Credit			155.1			0			155.1			0

	Total fixed maturities			2,814.40			143.8			2,670.60			0
	Equity securities			534.3			476.7			56.3			1.3
	Other investments			117.8			0			117.8			0
	Short-term investments			351.6			347			4.6			0
	Other assets			2.6			0			0			2.6

			$	3,820.70		$	967.5		$	2,849.30		$	3.9


(a)	Quoted prices in active markets for identical assets
(b)	Significant other observable inputs
(c)	Significant unobservable inputs
Schedule of Reconciliation of Beginning and Ending Balances for Investments Categorized as Level 3	'
	A reconciliation of the beginning and ending balances for the investments categorized as Level 3 are as follows:
	Fair Value Measurements Using Observable Inputs (Level 3)


	(in millions)		Equity			Other Assets			Total
	(in millions)		Securities			Other Assets			Total
	Beginning balance, January 1, 2014		$	1.3		$	2.6		$	3.9
	Transfers into Level 3			0			0			0
	Transfers out of Level 3			0			0			0
	Total gains or losses (realized/unrealized):
	Included in net income (loss)			0			0			0
	Included in other comprehensive income (loss)			0			0			0
	Purchases, issuances, sales, and settlements
	Purchases			0			0			0
	Issuances			0			0			0
	Sales			(0.3	)		0			(0.3	)
	Settlements			0			(2.6	)		(2.6	)

	Ending balance, September 30, 2014		$	1		$	0		$	1

	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, 2014		$	0		$	0		$	0



	(in millions)		Equity			Other Assets			Total
	(in millions)		Securities			Other Assets			Total
	Beginning balance, January 1, 2013		$	1.8		$	6.9		$	8.7
	Transfers into Level 3			0			0			0
	Transfers out of Level 3			0			0			0
	Total gains or losses (realized/unrealized):
	Included in net income (loss)			0.1			0			0.1
	Included in other comprehensive income (loss)			0			0			0
	Purchases, issuances, sales, and settlements
	Purchases			0			0			0
	Issuances			0			0			0
	Sales			(0.6	)		0			(0.6	)
	Settlements			0			(4.3	)		(4.3	)

	Ending balance, December 31, 2013		$	1.3		$	2.6		$	3.9

	Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2013		$	0		$	0		$	0

Reserves_for_Losses_and_Loss_A1

Reserves for Losses and Loss Adjustment Expenses (Tables)	9 Months Ended
Reserves for Losses and Loss Adjustment Expenses (Tables)	Sep. 30, 2014
Insurance [Abstract]	'
Reinsurance Recoverables	'
	The following table provides a reconciliation of reserves for losses and loss adjustment expenses (“LAE”):


			For the Nine Months
			Ended September 30,
	(in millions)		2014			2013
	Net reserves beginning of the year		$	2,107.60		$	2,110.90
	Add:
	Losses and LAE incurred during current calendar year, net of reinsurance:
	Current accident year			585.9			575.6
	Prior accident years			(26.4	)		(21.5	)

	Losses and LAE incurred during calendar year, net of reinsurance			559.5			554.1

	Deduct:
	Losses and LAE payments made during current calendar year, net of reinsurance:
	Current accident year			115.3			131.7
	Prior accident years			435.5			429

	Losses and LAE payments made during current calendar year, net of reinsurance			550.8			560.7

	Add:
	Change in participation interest (1)			24.7			10.4
	Foreign exchange adjustments			(4.9	)		(6.3	)

	Net reserves - end of period			2,136.10			2,108.40
	Add:
	Reinsurance recoverables on unpaid losses and LAE, end of period			926.5			1,114.50

	Gross reserves - end of period		$	3,062.60		$	3,222.90


	(1)	Amount represents increase in reserves due to change in syndicate participation.

Disclosures_about_Fair_Value_o1

Disclosures about Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2014
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, 2014				December 31, 2013
	(in millions)	Carrying		Fair Value		Carrying		Fair Value
	(in millions)	Amount		Fair Value		Amount		Fair Value
	Junior subordinated debentures	$	172.7	$	155.5	$	193.3	$	155.5
	Senior unsecured fixed rate notes		143.8		132.3		143.8		116.2
	Other indebtedness:
	Floating rate loan stock		63.8		57.4		65.5		52.7
	Note payable		0.6		0.6		0.8		0.6

		$	380.9	$	345.8	$	403.4	$	325

Shareholders_Equity_Tables

Shareholders' Equity (Tables)	9 Months Ended
Shareholders' Equity (Tables)	Sep. 30, 2014
Equity [Abstract]	'
Schedule of Repurchase of Shares	'
	In 2014, we repurchased shares under Securities Exchange Act of 1934 Rule 10b5-1 trading plans as follows:


	Date Trading	2014		Number of		Average Price of		Total Cost		Repurchase
	Plan Initiated	Purchase Period		Shares Repurchased		Shares Repurchased		(in millions)		Authorization Year
	12/17/13		02/04/14-02/12/14		15,789	$	43.28	$	0.7		2013
	3/18/14		03/18/14-04/28/14		436,867	$	45.81	$	20		2013
	6/13/14		06/17/14-08/04/14		41,362	$	49.94	$	2.1		2013
	9/12/14		09/16/14-09/30/14		86,234	$	52.17	$	4.5		2013

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
Accumulated Other Comprehensive Income (Loss) (Tables)	Sep. 30, 2014
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, 2014 and 2013 is presented in the following tables:


	(in millions)	Foreign Currency			Unrealized			Defined Benefit			Total
		Translation			Holding Gains			Pension Plans
		Adjustments			on Securities
	Beginning balance, January 1, 2014	$	(11.5	)	$	163.9		$	(4.6	)	$	147.8
	Other comprehensive income before reclassifications		(1.9	)		5.4			0			3.5
	Amounts reclassified from accumulated other comprehensive income		0			(14.8	)		0			(14.8	)

	Net current-period other comprehensive income		(1.9	)		(9.4	)		0			(11.3	)

	Ending balance, September 30, 2014	$	(13.4	)	$	154.5		$	(4.6	)	$	136.5



	(in millions)	Foreign Currency			Unrealized			Defined Benefit			Total
		Translation			Holding Gains			Pension Plans
		Adjustments			on Securities
	Beginning balance, January 1, 2013	$	(8.7	)	$	204.1		$	(5.9	)	$	189.5
	Other comprehensive loss before reclassifications		(2.2	)		(23.9	)		0			(26.1	)
	Amounts reclassified from accumulated other comprehensive loss		0			(11.6	)		0			(11.6	)

	Net current-period other comprehensive loss		(2.2	)		(35.5	)		0			(37.7	)

	Ending balance, September 30, 2013	$	(10.9	)	$	168.6		$	(5.9	)	$	151.8




Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	'
	The amounts reclassified from accumulated other comprehensive income (loss) shown in the above table have been included in the following captions in our Consolidated Statements of Income:


		For the Three Months						For the Nine Months
		Ended September 30,						Ended September 30,
	(in millions)	2014			2013			2014			2013
	Unrealized gains and losses on securities
	Net realized investment gains	$	(5.8	)	$	(3.3	)	$	(22.0	)	$	(18.3	)
	Provision for income taxes		4.1			2			7.2			6.7

	Net of taxes	$	(1.7	)	$	(1.3	)	$	(14.8	)	$	(11.6	)

Net_Income_Per_Common_Share_Ta

Net Income Per Common Share (Tables)	9 Months Ended
Net Income Per Common Share (Tables)	Sep. 30, 2014
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				For the Nine Months
		Ended September 30,				Ended September 30,
	(in millions, except number of shares and per share amounts)	2014		2013		2014		2013
	Net income	$	44.7	$	31	$	123.5	$	95.4
	Weighted average common shares outstanding - basic		25,956,599		26,682,176		26,203,819		26,961,792
	Effect of dilutive securities:
	Equity compensation awards		480,334		1,137,374		466,357		1,031,543

	Weighted average common shares outstanding - diluted		26,436,933		27,819,550		26,670,176		27,993,335

	Net income per common share - basic	$	1.72	$	1.16	$	4.71	$	3.54

	Net income per common share - diluted	$	1.69	$	1.12	$	4.63	$	3.41

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	9 Months Ended
Supplemental Cash Flow Information (Tables)	Sep. 30, 2014
Supplemental Cash Flow Elements [Abstract]	'
Schedule of Interest Paid	'
	Interest paid. Interest paid was as follows:


		For the Nine Months
		Ended September 30,
	(in millions)	2014		2013
	Senior unsecured fixed rate notes	$	7	$	7
	Junior subordinated debentures		5.8		6
	Other indebtedness		2.3		2.1

	Total interest paid	$	15.1	$	15.1

Sharebased_Compensation_Tables

Share-based Compensation (Tables)	9 Months Ended
Share-based Compensation (Tables)	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Fair Value Assumptions	'
	The following table summarizes the assumptions we used for the nine months ended September 30, 2014 and 2013:


		2014			2013
	Risk-free rate of return		1.77	%		1.44	%
	Expected dividend yields		1.49	%		1.55	%
	Expected award life (years)		4.67			4.92
	Expected volatility		22.84	%		31.12	%
Summary of Restricted Share Activity	'
	A summary of restricted share activity as of September 30, 2014 and changes during the nine months then ended is as follows:


		Shares			Weighted-Average
					Grant Date
					Fair Value
	Outstanding at January 1, 2014		257,975		$	32.97
	Granted		107,696		$	44.93
	Vested and issued		(58,680	)	$	31.62
	Expired or forfeited		(35,511	)	$	33.08

	Outstanding at September 30, 2014		271,480		$	37.99

Summary of Stock-Settled SARs Activity	'
	A summary of stock-settled SARs activity as of September 30, 2014 and changes during the nine months then ended is as follows:


		Shares			Weighted-Average
		Shares			Exercise Price
	Outstanding at January 1, 2014		1,288,698		$	29.47
	Granted		188,273		$	43.23
	Exercised		(107,979	)	$	29.4
	Expired or forfeited		(68,523	)	$	32.95

	Outstanding at September 30, 2014		1,300,469		$	31.28

Summary of Cash-Settled SARs Activity	'
	A summary of cash-settled SARs activity as of September 30, 2014 and changes during the nine months then ended is as follows:


		Shares			Weighted-Average
		Shares			Exercise Price
	Outstanding at January 1, 2014		1,743,758		$	33
	Granted		756,853		$	44.28
	Exercised		(386,615	)	$	30.94
	Expired or forfeited		(170,195	)	$	35.49

	Outstanding at September 30, 2014		1,943,801		$	37.58

Underwriting_Acquisition_and_I1

Underwriting, Acquisition and Insurance Expenses (Tables)	9 Months Ended
Underwriting, Acquisition and Insurance Expenses (Tables)	Sep. 30, 2014
Text Block [Abstract]	'
Underwriting, Acquisition and Insurance Expenses	'
	Underwriting, acquisition and insurance expenses were as follows:


		For the Three Months						For the Nine Months
		Ended September 30,						Ended September 30,
	(in millions)	2014			2013			2014			2013
	Commissions	$	59.8		$	57.2		$	178		$	174.7
	General expenses		69			65.4			211.9			200.8
	Premium taxes, boards and bureaus		7.2			6.8			19.5			19.7

			136			129.4			409.4			395.2
	Net deferral amortization of policy acquisition costs		(2.2	)		(2.7	)		(10.1	)		(17.2	)

	Total underwriting, acquisition and insurance expenses	$	133.8		$	126.7		$	399.3		$	378

Income_Taxes_Tables

Income Taxes (Tables)	9 Months Ended
Income Taxes (Tables)	Sep. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Tax Provision (Benefit)	'
	Our income tax provision includes the following components:


			For the Three Months						For the Nine Months
			Ended September 30,						Ended September 30,
	(in millions)		2014			2013			2014			2013
	Current tax provision		$	(15.0	)	$	3.5		$	(10.7	)	$	13.4
	Deferred tax provision related to:
	Future tax deductions			19.7			(2.4	)		52.9			2
	Valuation allowance change			(1.1	)		0.8			(30.0	)		2.4

	Income tax provision		$	3.6		$	1.9		$	12.2		$	17.8

Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates	'
	For the three and nine months ended September 30, 2014 and 2013, pre-tax income (loss) attributable to our operations and the operations’ effective tax rates were as follows:


			For the Three Months Ended September 30,
			2014						2013
	(in millions)		Pre-tax			Effective Tax			Pre-tax			Effective Tax
	(in millions)		Income (Loss)			Rate			Income (Loss)			Rate
	Bermuda		$	27.5			0	%	$	14.2			0	%
	United States			13.5			16.2	%		19.6			22.9	%
	United Kingdom			9.2			15.4	%		1.6			-164.7	%
	Belgium			(0.1	)		-7.9	%		0.1			91.6	%
	Brazil			(1.2	)		0	%		(1.5	)		0	%
	United Arab Emirates			0			0	%		(0.4	)		0	%
	Ireland			0			0	%		(0.1	)		0	%
	Malta			(0.8	)		0	%		(0.6	)		0	%
	Switzerland			0.2			4.8	%		0	(1)		19.7	%

	Pre-tax income		$	48.3					$	32.9


	(1)	Pre-tax income for the respective period was less than $0.1 million.


			For the Nine Months Ended September 30,
			2014						2013
	(in millions)		Pre-tax			Effective Tax			Pre-tax			Effective Tax
	(in millions)		Income (Loss)			Rate			Income (Loss)			Rate
	Bermuda		$	74.3			0	%	$	34.2			0	%
	United States			49.2			20.9	%		68.6			23.5	%
	United Kingdom			11.1			17.1	%		18.3			9.2	%
	Belgium			(0.1	)		-32.4	%		0.1			26.9	%
	Brazil			3.9			0	%		(6.2	)		0	%
	United Arab Emirates			(0.9	)		0	%		(0.4	)		0	%
	Ireland			0			0	%		(0.1	)		0	%
	Malta			(1.8	)		0	%		(1.3	)		0	%
	Switzerland			0	(2)		24.2	%		0	(2)		21	%

	Pre-tax income		$	135.7					$	113.2


	(2)	Pre-tax income for the respective period 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						For the Nine Months
			Ended September 30,						Ended September 30,
	(in millions)		2014			2013			2014			2013
	Income tax provision at expected rate		$	6.1		$	6.2		$	20.6		$	25.2
	Tax effect of:
	Tax-exempt interest			(1.1	)		(1.3	)		(3.4	)		(4.1	)
	Dividends received deduction			(0.5	)		(0.7	)		(1.7	)		(1.8	)
	Valuation allowance change			(1.1	)		0.8			(30.0	)		2.4
	Other permanent adjustments, net			(0.1	)		(0.5	)		(1.0	)		(1.4	)
	Adjustment for prior year tax return			(1.1	)		0			(1.1	)		0
	Adjustment for annualized rate - United States			0.3			0.3			0.5			(0.1	)
	Adjustment for annualized rate - Foreign			0.5			0			(1.4	)		0
	Prior period adjustment to deferred			0.9			0			(0.2	)		0
	United States state tax benefit			0			(0.1	)		0			(0.4	)
	PXRE Reinsurance capital loss carryforward			0			0			29.8			0
	Deferred tax rate reduction			(0.1	)		(1.3	)		(0.1	)		(1.3	)
	Foreign exchange adjustments			(0.2	)		(1.7	)		(0.1	)		(1.3	)
	Foreign withholding taxes			0			0.2			0.3			0.6

	Income tax provision		$	3.6		$	1.9		$	12.2		$	17.8

	Income tax provision (benefit) - Foreign		$	1.5		$	(2.6	)	$	2		$	1.7
	Income tax provision - United States Federal			2.1			4.4			9.8			16.1
	Income tax (benefit) provision - United States State			0			(0.1	)		0.1			(0.6	)
	Foreign withholding tax - United States			0			0.2			0.3			0.6

	Income tax provision		$	3.6		$	1.9		$	12.2		$	17.8

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
Segment Information (Tables)	Sep. 30, 2014
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						For the Nine Months
		Ended September 30,						Ended September 30,
	(in millions)	2014			2013			2014			2013
	Revenue:
	Earned premiums
	Excess and Surplus Lines	$	121.2		$	120.6		$	363.9		$	334.4
	Commercial Specialty		72.7			74.6			215.5			225.1
	International Specialty		38			37.5			112.6			106.6
	Syndicate 1200		104.4			97.3			305.9			295.6
	Run-off Lines		1.3			0.5			1.5			0.5

	Total earned premiums		337.6			330.5			999.4			962.2
	Net investment income
	Excess and Surplus Lines		8.9			10.2			27.2			32.3
	Commercial Specialty		4.5			5.6			13.8			17.6
	International Specialty		2.3			2.4			6.1			6.4
	Syndicate 1200		2.1			2.5			7.9			8.1
	Run-off Lines		2.4			2.6			7.2			8.2
	Corporate and Other		0.6			0.8			2.5			4.7

	Total net investment income		20.8			24.1			64.7			77.3
	Fee income, net		1.6			0.3			0.1			0.5
	Net realized investment gains and other		12.9			9.1			42.5			29.6

	Total revenue	$	372.9		$	364		$	1,106.70		$	1,069.60



		For the Three Months						For the Nine Months
		Ended September 30,						Ended September 30,
	(in millions)	2014			2013			2014			2013
	Income (loss) before income taxes
	Excess and Surplus Lines	$	27.6		$	29.6		$	75.9		$	60.2
	Commercial Specialty		8			10.1			9.2			17.3
	International Specialty		4			0.5			16.4			8.1
	Syndicate 1200		8.8			8.5			34.7			26.7
	Run-off Lines		(8.3	)		(9.1	)		(17.6	)		(5.8	)

	Total segment income before taxes		40.1			39.6			118.6			106.5
	Corporate and Other		(4.7	)		(15.8	)		(25.4	)		(22.9	)
	Net realized investment gains and other		12.9			9.1			42.5			29.6

	Total income before income taxes	$	48.3		$	32.9		$	135.7		$	113.2

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, 2014 and 2013. 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						For the Nine Months
		Ended September 30,						Ended September 30,
	(in millions)	2014			2013			2014			2013
	Bermuda	$	27		$	27.4		$	75.7		$	75.3
	Brazil		11			9.9			35.4			29.9
	Malta		0.5			0.5			1.6			1.3
	United Kingdom		104.4			97.7			305.9			296
	United States		194.7			195			580.8			559.7

	Total earned premiums	$	337.6		$	330.5		$	999.4		$	962.2

Identifiable Assets	'
	The following table presents our identifiable assets.


	(in millions)	September 30,			December 31,
	(in millions)	2014			2013
	Excess and Surplus Lines	$	2,383.80		$	2,252.20
	Commercial Specialty		1,287.00			1,333.40
	International Specialty		771.5			743.6
	Syndicate 1200		1,287.20			1,638.80
	Run-off Lines		586.2			555.9
	Corporate and Other		72.9			67.1

	Total	$	6,388.60		$	6,591.00

Information_Provided_in_Connec1

Information Provided in Connection with Outstanding Debt of Subsidiaries (Tables)	9 Months Ended
	Sep. 30, 2014
Text Block [Abstract]	'
Condensed Consolidating Balance Sheet	'
	CONDENSED CONSOLIDATING BALANCE SHEET
	September 30, 2014
	(in millions)


			Argo Group				Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
			International Holdings,				and Subsidiaries				and Eliminations (1)				Adjustments (2)
			Ltd (Parent Guarantor)				(Subsidiary Issuer)
	Assets
	Investments		$	1.9			$	2,847.80			$	1,262.00			$	0			$	4,111.70
	Cash			0				69				22.1				(18.0	)			73.1
	Accrued investment income			0				17.2				5				0				22.2
	Premiums receivable			0				161				235.7				0				396.7
	Reinsurance recoverables			0				1,188.70				(186.4	)			0				1,002.30
	Goodwill and other intangible assets, net			0				135.6				99.9				0				235.5
	Current income taxes receivable, net			0				25.3				4.7				0				30
	Deferred acquisition costs, net			0				58.4				71.6				0				130
	Ceded unearned premiums			0				100.9				126.1				0				227
	Other assets			10.4				104.1				52.6				(7.0	)			160.1
	Due from affiliates			7				(18.8	)			18.8				(7.0	)			0
	Intercompany note receivable			0				71.4				(71.4	)			0				0
	Investments in subsidiaries			1,710.80				0				0				(1,710.8	)			0

	Total assets		$	1,730.10			$	4,760.60			$	1,640.70			$	(1,742.8	)		$	6,388.60

	Liabilities and Shareholders’ Equity
	Reserves for losses and loss adjustment expenses		$	0			$	2,160.50			$	902.1			$	0			$	3,062.60
	Unearned premiums			0				453.1				412.3				0				865.4
	Funds held and ceded reinsurance payable, net			0				658.5				(419.7	)			0				238.8
	Long-term debt			49				288.7				63.8				(20.6	)			380.9
	Deferred tax liabilities, net			0				47.1				8.6				0				55.7
	Accrued underwriting expenses and other liabilities			13.3				93.5				51.5				0				158.3
	Intercompany note payable			40.9				0				0				(40.9	)			0

	Total liabilities			103.2				3,701.40				1,018.60				(61.5	)			4,761.70

	Total shareholders’ equity			1,626.90				1,059.20				622.1				(1,681.3	)			1,626.90

	Total liabilities and shareholders’ equity		$	1,730.10			$	4,760.60			$	1,640.70			$	(1,742.8	)		$	6,388.60


	(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, 2013
	(in millions)


			Argo Group				Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
			International Holdings,				and Subsidiaries				and Eliminations (1)				Adjustments (2)
			Ltd (Parent Guarantor)				(Subsidiary Issuer)
	Assets
	Investments		$	1.1			$	2,785.10			$	1,293.00			$	0			$	4,079.20
	Cash			0				132.1				25.3				0				157.4
	Accrued investment income			0				19.7				6				0				25.7
	Premiums receivable			0				150.8				197.6				0				348.4
	Reinsurance recoverables			0				1,145.90				117.6				0				1,263.50
	Goodwill and other intangible assets, net			0				137.4				102.4				0				239.8
	Current income taxes receivable, net			0				0.5				(0.5	)			0				0
	Deferred acquisition costs, net			0				55.6				58.3				0				113.9
	Ceded unearned premiums			0				88.2				108.1				0				196.3
	Other assets			4.6				97.8				64.4				0				166.8
Due from affiliates			3.1				1.5				(1.5	)			(3.1	)			0
Intercompany note receivable			0				87.4				(87.4	)			0				0
Investments in subsidiaries			1,625.20				0				0				(1,625.2	)			0

Total assets		$	1,634.00			$	4,702.00			$	1,883.30			$	(1,628.3	)		$	6,591.00

Liabilities and Shareholders’ Equity
Reserves for losses and loss adjustment expenses		$	0			$	2,157.00			$	1,073.30			$	0			$	3,230.30
Unearned premiums			0				425.5				353.6				0				779.1
Funds held and ceded reinsurance payable, net			0				642.4				(244.0	)			0				398.4
Long-term debt			49				288.9				65.5				0				403.4
Current income taxes payable, net			0				8.9				(3.7	)			0				5.2
Deferred tax liabilities, net			0				22.8				5.9				0				28.7
Accrued underwriting expenses and other liabilities			15.4				98.2				69.3				0				182.9
Intercompany note payable			6.6				0				0				(6.6	)			0

Total liabilities			71				3,643.70				1,319.90				(6.6	)			5,028.00

Total shareholders’ equity			1,563.00				1,058.30				563.4				(1,621.7	)			1,563.00

Total liabilities and shareholders’ equity		$	1,634.00			$	4,702.00			$	1,883.30			$	(1,628.3	)		$	6,591.00


(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, 2014
	(in millions)


			Argo Group				Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
			International Holdings,				and Subsidiaries				and Eliminations (1)				Adjustments (2)
			Ltd (Parent Guarantor)				(Subsidiary Issuer)
	Premiums and other revenue:
	Earned premiums		$	0			$	114.2			$	223.4			$	0			$	337.6
	Net investment (loss) income			(0.1	)			13.6				7.3				0				20.8
	Fee income, net			0				1.5				0.1				0				1.6
	Net realized investment gains and other			0				9.2				3.7				0				12.9

	Total revenue			(0.1	)			138.5				234.5				0				372.9

	Expenses:
	Losses and loss adjustment expenses			0				69.9				122				0				191.9
	Underwriting, acquisition and insurance expenses			2.3				51.6				79.9				0				133.8
	Interest expense			0.7				3.8				0.6				(0.2	)			4.9
	Foreign currency exchange loss (gain)			0				0.3				(6.3	)			0				(6.0	)

	Total expenses			3				125.6				196.2				(0.2	)			324.6

	(Loss) income before income taxes			(3.1	)			12.9				38.3				0.2				48.3
	Provision for income taxes			0				2.1				1.5				0				3.6

	Net (loss) income before equity in earnings of subsidiaries			(3.1	)			10.8				36.8				0.2				44.7
	Equity in undistributed earnings of subsidiaries			47.9				0				0				(47.9	)			0

	Net income		$	44.8			$	10.8			$	36.8			$	(47.7	)		$	44.7


	(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations
	(2)	Includes all Argo Group parent company eliminations


	CONDENSED CONSOLIDATING STATEMENT OF INCOME
	FOR THE THREE MONTHS ENDED SEPTEMBER 30, 2013
	(in millions)


			Argo Group				Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
			International Holdings,				and Subsidiaries				and Eliminations (1)				Adjustments (2)
			Ltd (Parent Guarantor)				(Subsidiary Issuer)
	Premiums and other revenue:
	Earned premiums		$	0			$	105.2			$	225.3			$	0			$	330.5
	Net investment income			0				16.7				7.7				(0.3	)			24.1
	Fee income, net			0				(0.6	)			0.9				0				0.3
	Net realized investment gains and other			0				7.2				1.9				0				9.1

	Total revenue			0				128.5				235.8				(0.3	)			364

	Expenses:
	Losses and loss adjustment expenses			0				65.9				125				0				190.9
	Other reinsurance-related expenses			0				(2.9	)			7.5				0				4.6
	Underwriting, acquisition and insurance expenses			5.8				42.1				78.8				0				126.7
	Interest expense			0.7				3.8				0.9				(0.3	)			5.1
	Foreign currency exchange loss (gain)			0				(0.1	)			3.9				0				3.8

	Total expenses			6.5				108.8				216.1				(0.3	)			331.1

	(Loss) income before income taxes			(6.5	)			19.7				19.7				0				32.9
Provision for income taxes			0				4.4				(2.5	)			0				1.9

Net (loss) income before equity in earnings of subsidiaries			(6.5	)			15.3				22.2				0				31
Equity in undistributed earnings of subsidiaries			37.5				0				0				(37.5	)			0

Net income		$	31			$	15.3			$	22.2			$	(37.5	)		$	31


(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations
(2)	Includes all Argo Group parent company eliminations
CONDENSED CONSOLIDATING STATEMENT OF INCOME
FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2014
(in millions)


		Argo Group				Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
		International Holdings,				and Subsidiaries				and Eliminations (1)				Adjustments (2)
		Ltd (Parent Guarantor)				(Subsidiary Issuer)
Premiums and other revenue:
Earned premiums		$	0			$	343.7			$	655.7			$	0			$	999.4
Net investment (loss) income			(0.3	)			42.4				22.6				0				64.7
Fee (expense) income, net			0				(1.5	)			1.6				0				0.1
Net realized investment gains and other			0				34.6				7.9				0				42.5

Total revenue			(0.3	)			419.2				687.8				0				1,106.70

Expenses:
Losses and loss adjustment expenses			0				211.2				348.3				0				559.5
Underwriting, acquisition and insurance expenses			12.5				147.9				238.9				0				399.3
Interest expense			1.8				11.4				2.1				(0.3	)			15
Foreign currency exchange loss (gain)			0				0.1				(2.9	)			0				(2.8	)

Total expenses			14.3				370.6				586.4				(0.3	)			971

(Loss) income before income taxes			(14.6	)			48.6				101.4				0.3				135.7
Provision for income taxes			0				10.2				2				0				12.2

Net (loss) income before equity in earnings of subsidiaries			(14.6	)			38.4				99.4				0.3				123.5
Equity in undistributed earnings of subsidiaries			138.1				0				0				(138.1	)			0

Net income		$	123.5			$	38.4			$	99.4			$	(137.8	)		$	123.5


(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations
(2)	Includes all Argo Group parent company eliminations

CONDENSED CONSOLIDATING STATEMENT OF INCOME
FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2013
(in millions)


		Argo Group				Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
		International Holdings,				and Subsidiaries				and Eliminations (1)				Adjustments (2)
		Ltd (Parent Guarantor)				(Subsidiary Issuer)
Premiums and other revenue:
Earned premiums		$	0			$	321.2			$	641			$	0			$	962.2
Net investment income			0				57.2				21				(0.9	)			77.3
Fee income, net			0				(1.9	)			2.4				0				0.5
Net realized investment gains (losses) and other			0				32.8				(3.2	)			0				29.6

Total revenue			0				409.3				661.2				(0.9	)			1,069.60

Expenses:
Losses and loss adjustment expenses			0				194.9				359.2				0				554.1
Other reinsurance-related expenses			0				0				14.4				0				14.4
Underwriting, acquisition and insurance expenses			18.3				134.3				225.4				0				378
Interest expense			2.3				11.4				2.3				(0.9	)			15.1
Foreign currency exchange loss (gain)			0				0.1				(5.3	)			0				(5.2	)

Total expenses			20.6				340.7				596				(0.9	)			956.4

(Loss) income before income taxes			(20.6	)			68.6				65.2				0				113.2
Provision for income taxes			0				16				1.8				0				17.8

Net (loss) income before equity in earnings of subsidiaries			(20.6	)			52.6				63.4				0				95.4
Equity in undistributed earnings of subsidiaries			116				0				0				(116.0	)			0

Net income		$	95.4			$	52.6			$	63.4			$	(116.0	)		$	95.4


(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations
(2)	Includes all Argo Group parent company eliminations
Condensed Consolidating Statement of Cash Flows	'
	CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
	FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2014
	(in millions)


			Argo Group				Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
			International Holdings,				and Subsidiaries				and Eliminations (1)				Adjustments (2)
			Ltd (Parent Guarantor)				(Subsidiary Issuer)
	Net cash flows from operating activities		$	(16.5	)		$	11.8			$	70			$	6.4			$	71.7

	Cash flows from investing activities:
	Proceeds from sales of investments			0				609.2				366.9				0				976.1
	Proceeds from maturities and mandatory calls of investments			0				148				95.6				0				243.6
	Purchases of investments			0				(773.1	)			(491.7	)			0				(1,264.8	)
	Change in short-term investments and foreign regulatory deposits			0.1				(12.5	)			18.4				0				6
	Settlements of foreign currency exchange forward contracts			(0.5	)			0				1.1				0				0.6
	Issuance of intercompany note, net			0				14.5				(48.5	)			34				0
	Purchase of fixed assets			(7.0	)			(17.7	)			4.4				(6.4	)			(26.7	)
	Other, net			0				(2.4	)			(19.1	)			0				(21.5	)

	Cash (used) provided by investing activities			(7.4	)			(34.0	)			(72.9	)			27.6				(86.7	)

	Cash flows from financing activities:
	Borrowings under intercompany note, net			34				0				0				(34.0	)			0
	Redemption of trust preferred securities, net			0				0				0				(18.0	)			(18.0	)
	Payment on note payable			0				(0.1	)			0				0				(0.1	)
	Activity under stock incentive plans			3.3				0				0				0				3.3
	Repurchase of Company’s common shares			0				(40.9	)			0				0				(40.9	)
	Excess tax expense from share-based payment arrangements			0				0.1				0				0				0.1
	Payment of cash dividends to common shareholders			(13.4	)			0				0				0				(13.4	)

	Cash provided (used) by financing activities			23.9				(40.9	)			0				(52.0	)			(69.0	)

	Effect of exchange rate changes on cash			0				0				(0.3	)			0				(0.3	)

	Change in cash			0				(63.1	)			(3.2	)			(18.0	)			(84.3	)
	Cash, beginning of period			0				132.1				25.3				0				157.4

	Cash, end of period		$	0			$	69			$	22.1			$	(18.0	)		$	73.1


	(1)	Includes all other subsidiaries of Argo Group International Holdings, Ltd and all intercompany eliminations
	(2)	Includes all Argo Group parent company eliminations

	CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
	FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2013
	(in millions)


			Argo Group				Argo Group US, Inc.				Other Subsidiaries				Consolidating				Total
			International Holdings,				and Subsidiaries				and Eliminations (1)				Adjustments (2)
			Ltd (Parent Guarantor)				(Subsidiary Issuer)
	Net cash flows from operating activities		$	(15.5	)		$	75.9			$	(63.4	)		$	0			$	(3.0	)

	Cash flows from investing activities:
	Proceeds from sales of investments			0				863.2				515.6				0				1,378.80
	Proceeds from maturities and mandatory calls of investments			0				139				85.2				0				224.2
	Purchases of investments			0				(942.4	)			(464.9	)			0				(1,407.3	)
	Change in short-term investments and foreign regulatory deposits			(0.8	)			(38.5	)			(36.2	)			0				(75.5	)
	Settlements of foreign currency exchange forward contracts			1.9				0				(8.3	)			0				(6.4	)
	Issuance of intercompany note, net			0				0				(24.9	)			24.9				0
	Purchase of fixed assets			0				(17.7	)			(1.4	)			0				(19.1	)
	Other, net			(0.1	)			4.4				0.2				0				4.5

Cash provided by investing activities			1				8				65.3				24.9				99.2

Cash flows from financing activities:
Borrowings under intercompany note, net			24.9				0				0				(24.9	)			0
Activity under stock incentive plans			1.4				0				0				0				1.4
Repurchase of Company’s common shares			0				(40.1	)			0				0				(40.1	)
Excess tax expense from share-based payment arrangements			0				(0.2	)			0.4				0				0.2
Payment of cash dividends to common shareholders			(11.8	)			0				0				0				(11.8	)

Cash provided (used) by financing activities			14.5				(40.3	)			0.4				(24.9	)			(50.3	)

Effect of exchange rate changes on cash			0				0				(0.1	)			0				(0.1	)

Change in cash			(0.0	)			43.6				2.2				0				45.8
Cash, beginning of period			0				73.9				21.9				0				95.8

Cash, end of period		$	(0.0	)		$	117.5			$	24.1			$	0			$	141.6


(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_Addition

Basis of Presentation - Additional Information (Detail)	9 Months Ended
Basis of Presentation - Additional Information (Detail)	Sep. 30, 2014	Sep. 30, 2013	7-May-13
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'	'	'
Stock dividend declared	'	'	10.00%
Additional stock issued as dividend	'	2,447,839	'
Dividends declaration date	'	7-May-13	'
Dividends payable date	'	17-Jun-13	'
Dividend payable, date of record	1-Sep-14	3-Jun-13	'

Investments_Schedule_of_Amorti

Investments - Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value of Investments (Detail) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	$3,871.50	$3,836
Gross Unrealized Gains	273	274.8
Gross Unrealized Losses	32.8	31.6
Fair Value	4,111.70	4,079.20
Other Investments [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	398	377.4
Gross Unrealized Gains	7.3	2.8
Gross Unrealized Losses	2	1.3
Fair Value	403.3	378.9
Fixed Maturities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	2,798.60	2,760.10
Gross Unrealized Gains	70.5	83.4
Gross Unrealized Losses	28.2	29.1
Fair Value	2,840.90	2,814.40
Fixed Maturities [Member] \| U.S. Governments [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	209.8	273.4
Gross Unrealized Gains	1.5	2.4
Gross Unrealized Losses	0.5	0.5
Fair Value	210.8	275.3
Fixed Maturities [Member] \| Non-U.S. Governments [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	76.9	60.9
Gross Unrealized Gains	0.6	0.3
Gross Unrealized Losses	0.5	1
Fair Value	77	60.2
Fixed Maturities [Member] \| Obligations of States and Political Subdivisions [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	485.6	563.7
Gross Unrealized Gains	24.2	22.9
Gross Unrealized Losses	0.6	8.8
Fair Value	509.2	577.8
Fixed Maturities [Member] \| Credit-Financial [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	489.1	426.3
Gross Unrealized Gains	12.8	15.4
Gross Unrealized Losses	1.3	1.8
Fair Value	500.6	439.9
Fixed Maturities [Member] \| Credit-Industrial [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	461	385.5
Gross Unrealized Gains	10.3	13.8
Gross Unrealized Losses	2.8	2.2
Fair Value	468.5	397.1
Fixed Maturities [Member] \| Credit-Utility [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	146.8	162
Gross Unrealized Gains	4.3	5.4
Gross Unrealized Losses	0.7	0.8
Fair Value	150.4	166.6
Fixed Maturities [Member] \| CMO/MBS-Agency [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	179.4	219.4
Gross Unrealized Gains	8.2	9.2
Gross Unrealized Losses	0.9	1.7
Fair Value	186.7	226.9
Fixed Maturities [Member] \| CMO/MBS-Non Agency [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	13.7	19.4
Gross Unrealized Gains	0.9	0.8
Gross Unrealized Losses	0	0
Fair Value	14.6	20.2
Fixed Maturities [Member] \| CMBS [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	163.8	162.7
Gross Unrealized Gains	2.1	3.1
Gross Unrealized Losses	0.2	1
Fair Value	165.7	164.8
Fixed Maturities [Member] \| ABS-Residential [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	5.2	6.8
Gross Unrealized Gains	0	0.3
Gross Unrealized Losses	0.3	0.5
Fair Value	4.9	6.6
Fixed Maturities [Member] \| ABS-Non Residential [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	209.2	116.8
Gross Unrealized Gains	0.8	0.5
Gross Unrealized Losses	0.3	0.1
Fair Value	209.7	117.2
Fixed Maturities [Member] \| Foreign Denominated: Governments [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	140.4	207.7
Gross Unrealized Gains	1.8	4.9
Gross Unrealized Losses	7.4	5.9
Fair Value	134.8	206.7
Fixed Maturities [Member] \| Foreign Denominated: Credit [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	217.7	155.5
Gross Unrealized Gains	3	4.4
Gross Unrealized Losses	12.7	4.8
Fair Value	208	155.1
Equity Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	318.7	346.9
Gross Unrealized Gains	195.2	188.6
Gross Unrealized Losses	2.6	1.2
Fair Value	511.3	534.3
Short-Term Investments [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	356.2	351.6
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$356.20	$351.60

Investments_Additional_Informa

Investments - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 28, 2011
	Security	Sep. 30, 2013	Security	Sep. 30, 2013	Dec. 31, 2013	Dec. 28, 2011
Schedule of Investments [Line Items]	'	'	'	'	'	'
Fair value of investments, assets managed on behalf of the trade capital providers	$70.10	'	$70.10	'	$87.30	'
Number of securities in an unrealized loss position, total	5,853	'	5,853	'	'	'
Number of securities in an unrealized loss position for less than one year	'	'	1,668	'	'	'
Number of securities in an unrealized loss position for a period of one year or greater	'	'	167	'	'	'
Other-than-temporary losses on fixed maturities portfolio	0	0	1.2	0.3	'	'
Other-than-temporary losses equity portfolio	0.2	0.1	0.4	1.6	'	'
Total notional amount of the Company's holdings in non-U.S. Dollar denominated higher yielding fixed maturity investments	2	'	2	'	'	'
Notional amount of the currency forward contracts	'	'	'	'	'	100
Fair value of the currency forward contracts	2	1.6	2	1.6	'	'
Realized gains from currency forward contracts	'	2.4	'	2.4	'	'
Realized losses from currency forward contracts	2.1	2.2	0.2	2.2	'	'
Amortized Cost	3,871.50	'	3,871.50	'	3,836	'
Fair Value	4,111.70	'	4,111.70	'	4,079.20	'
Reported loss incurred	45	'	45	'	60.2	'
Reported loss expense reserve	45	'	45	'	60.2	'
Securities pledged to Lloyd's	243.2	'	243.2	'	250.8	'
Canadian Dollar [Member]	'	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'	'
Fair value of the currency forward contracts	1.5	'	1.5	'	'	'
Realized gains from currency forward contracts	1.1	'	1.1	'	'	'
Euro [Member]	'	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'	'
Fair value of the currency forward contracts	1.9	'	1.9	'	'	'
Realized gains from currency forward contracts	2	'	2	'	'	'
Securities Pledged as Collateral [Member]	'	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'	'
Pledged assets separately reported, securities pledged under letters of credit facilities, at amortized cost	55.4	'	55.4	'	96.6	'
Pledged assets separately reported, securities pledged under letters of credit facilities, at fair value	55.8	'	55.8	'	97.5	'
Currency Forward Contracts [Member]	'	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'	'
Notional amount of the currency forward contracts	25.6	53.2	25.6	53.2	'	'
Currency Forward Contracts [Member] \| Canadian Dollar [Member]	'	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'	'
Notional amount of the currency forward contracts	118.3	'	118.3	'	'	'
Deposit with Various U.S. Insurance and Other Regulatory Agencies [Member]	'	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'	'
Amortized Cost	196	'	196	'	196.7	'
Fair Value	204.4	'	204.4	'	203.4	'
Non-U.S. Denominated Fixed Maturity Investments [Member]	'	'	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'	'	'
Total notional amount of the Company's holdings in non-U.S. Dollar denominated higher yielding fixed maturity investments	$1.80	'	$1.80	'	'	'

Investments_Schedule_of_Amorti1

Investments - Schedule of Amortized Cost and Fair Values of Fixed Maturity Investments, by Contractual Maturity (Detail) (USD $)	Sep. 30, 2014
In Millions, unless otherwise specified	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Amortized Cost, Due in one year or less	$255.70
Amortized Cost, Due after one year through five years	1,329.30
Amortized Cost, Due after five years through ten years	472.9
Amortized Cost, Thereafter	169.4
Amortized Cost, Structured securities	571.3
Amortized Cost, Total	2,798.60
Fair Value, Due in one year or less	254.2
Fair Value, Due after one year through five years	1,343.20
Fair Value, Due after five years through ten years	488.2
Fair Value, Thereafter	173.7
Fair Value, Structured securities	581.6
Fair Value, Total	$2,840.90

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 $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	$1,000.20	$907.90
Unrealized Losses, Less Than One Year	29.4	30.2
Fair Value, One Year or Greater	129.8	22.6
Unrealized Losses, One Year or Greater	3.4	1.4
Fair Value, Total	1,130	930.5
Unrealized Losses, Total	32.8	31.6
Other Investments [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	-2	-1.4
Unrealized Losses, Less Than One Year	2	1.3
Fair Value, One Year or Greater	0	0
Unrealized Losses, One Year or Greater	0	0
Fair Value, Total	-2	-1.4
Unrealized Losses, Total	2	1.3
Fixed Maturities [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	970.1	879.3
Unrealized Losses, Less Than One Year	24.8	27.7
Fair Value, One Year or Greater	129.8	22.6
Unrealized Losses, One Year or Greater	3.4	1.4
Fair Value, Total	1,099.90	901.9
Unrealized Losses, Total	28.2	29.1
Fixed Maturities [Member] \| U.S. Governments [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	59.5	55.3
Unrealized Losses, Less Than One Year	0.3	0.5
Fair Value, One Year or Greater	16.3	0
Unrealized Losses, One Year or Greater	0.2	0
Fair Value, Total	75.8	55.3
Unrealized Losses, Total	0.5	0.5
Fixed Maturities [Member] \| Non-U.S. Governments [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	28.3	36.3
Unrealized Losses, Less Than One Year	0.1	1
Fair Value, One Year or Greater	7.5	0
Unrealized Losses, One Year or Greater	0.4	0
Fair Value, Total	35.8	36.3
Unrealized Losses, Total	0.5	1
Fixed Maturities [Member] \| Obligations of States and Political Subdivisions [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	16.4	154.6
Unrealized Losses, Less Than One Year	0.1	8.8
Fair Value, One Year or Greater	27.9	3.1
Unrealized Losses, One Year or Greater	0.5	0
Fair Value, Total	44.3	157.7
Unrealized Losses, Total	0.6	8.8
Fixed Maturities [Member] \| Credit-Financial [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	149.1	88.7
Unrealized Losses, Less Than One Year	1.1	1.7
Fair Value, One Year or Greater	14.3	2.4
Unrealized Losses, One Year or Greater	0.2	0.1
Fair Value, Total	163.4	91.1
Unrealized Losses, Total	1.3	1.8
Fixed Maturities [Member] \| Credit-Industrial [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	222.5	85.7
Unrealized Losses, Less Than One Year	2.5	2
Fair Value, One Year or Greater	13.5	2.9
Unrealized Losses, One Year or Greater	0.3	0.2
Fair Value, Total	236	88.6
Unrealized Losses, Total	2.8	2.2
Fixed Maturities [Member] \| Credit-Utility [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	42.5	21.2
Unrealized Losses, Less Than One Year	0.7	0.7
Fair Value, One Year or Greater	1.9	1.9
Unrealized Losses, One Year or Greater	0	0.1
Fair Value, Total	44.4	23.1
Unrealized Losses, Total	0.7	0.8
Fixed Maturities [Member] \| CMO/MBS-Agency [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	23.8	58.4
Unrealized Losses, Less Than One Year	0.1	1.2
Fair Value, One Year or Greater	17.1	5.6
Unrealized Losses, One Year or Greater	0.8	0.5
Fair Value, Total	40.9	64
Unrealized Losses, Total	0.9	1.7
Fixed Maturities [Member] \| CMBS [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	29.8	24.2
Unrealized Losses, Less Than One Year	0.1	1
Fair Value, One Year or Greater	6.6	1.1
Unrealized Losses, One Year or Greater	0.1	0
Fair Value, Total	36.4	25.3
Unrealized Losses, Total	0.2	1
Fixed Maturities [Member] \| ABS-Residential [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	0	0
Unrealized Losses, Less Than One Year	0	0
Fair Value, One Year or Greater	3.4	3.6
Unrealized Losses, One Year or Greater	0.3	0.5
Fair Value, Total	3.4	3.6
Unrealized Losses, Total	0.3	0.5
Fixed Maturities [Member] \| ABS-Non Residential [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	106.9	59.1
Unrealized Losses, Less Than One Year	0.3	0.1
Fair Value, One Year or Greater	3.6	2
Unrealized Losses, One Year or Greater	0	0
Fair Value, Total	110.5	61.1
Unrealized Losses, Total	0.3	0.1
Fixed Maturities [Member] \| Foreign Denominated: Governments [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	111.5	170.5
Unrealized Losses, Less Than One Year	6.9	5.9
Fair Value, One Year or Greater	17	0
Unrealized Losses, One Year or Greater	0.5	0
Fair Value, Total	128.5	170.5
Unrealized Losses, Total	7.4	5.9
Fixed Maturities [Member] \| Foreign Denominated: Credit [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	179.8	125.3
Unrealized Losses, Less Than One Year	12.6	4.8
Fair Value, One Year or Greater	0.7	0
Unrealized Losses, One Year or Greater	0.1	0
Fair Value, Total	180.5	125.3
Unrealized Losses, Total	12.7	4.8
Equity Securities [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	32.1	25.5
Unrealized Losses, Less Than One Year	2.6	1.2
Fair Value, One Year or Greater	0	0
Unrealized Losses, One Year or Greater	0	0
Fair Value, Total	32.1	25.5
Unrealized Losses, Total	2.6	1.2
Short-Term Investments [Member]	'	'
Schedule of Investments [Line Items]	'	'
Fair Value, Less Than One Year	'	4.5
Unrealized Losses, Less Than One Year	'	0
Fair Value, One Year or Greater	'	0
Unrealized Losses, One Year or Greater	'	0
Fair Value, Total	'	4.5
Unrealized Losses, Total	$0	$0

Investments_Schedule_of_Aging_1

Investments - Schedule of Aging of Unrealized Losses on Company's Investments in Fixed Maturities, Equity Securities and Other Investments (Parenthetical) (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]	'	'
Unrealized losses less than one year	$0.10	$0.10
Unrealized losses one year or greater	$0.10	$0.10

Investments_Schedule_of_Compan

Investments - Schedule of Company's Gross Realized Investment Gains (Losses) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule of Investments [Line Items]	'	'	'	'
Gross realized investment gains	$20.80	$24.30	$69.90	$71.50
Gross realized investment and other losses	-7.9	-15.2	-27.4	-41.9
Net realized investment gains and other	12.9	9.1	42.5	29.6
Other Investments [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Gross realized investment gains	13.6	11.2	36.5	28.9
Gross realized investment and other losses	-6.5	-8.6	-12.6	-24.1
Other Assets [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Gross realized investment gains	2	0	2	0
Gross realized investment and other losses	0	0	-4	0
Fixed Maturities [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Gross realized investment gains	4.5	5.8	15.2	27.5
Gross realized investment and other losses	-1.1	-6.1	-8.7	-14.5
Equity Securities [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Gross realized investment gains	0.7	7.2	16.1	15
Gross realized investment and other losses	-0.1	-0.1	-0.2	-0.8
Short-Term Investments [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Gross realized investment gains	0	0.1	0.1	0.1
Gross realized investment and other losses	0	-0.3	-0.3	-0.6
Other-Than-Temporary Impairment Losses on Fixed Maturities [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Gross realized investment and other losses	0	0	-1.2	-0.3
Other-Than-Temporary Impairment Losses on Equity Securities [Member]	'	'	'	'
Schedule of Investments [Line Items]	'	'	'	'
Gross realized investment and other losses	($0.20)	($0.10)	($0.40)	($1.60)

Investments_Financial_Assets_M

Investments - Financial Assets Measured at Fair Value on Recurring Basis (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	$4,111.70	$4,079.20
Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	3,806.50	3,820.70
Other Investments [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	403.3	378.9
Other Investments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	98.1	117.8
Other Assets [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	'	2.6
Fixed Maturities [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	2,840.90	2,814.40
Fixed Maturities [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	2,840.90	2,814.40
Fixed Maturities [Member] \| U.S. Governments [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	210.8	275.3
Fixed Maturities [Member] \| U.S. Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	210.8	275.3
Fixed Maturities [Member] \| Non-U.S. Governments [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	77	60.2
Fixed Maturities [Member] \| Non-U.S. Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	77	60.2
Fixed Maturities [Member] \| Obligations of States and Political Subdivisions [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	509.2	577.8
Fixed Maturities [Member] \| Obligations of States and Political Subdivisions [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	509.2	577.8
Fixed Maturities [Member] \| Credit-Financial [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	500.6	439.9
Fixed Maturities [Member] \| Credit-Financial [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	500.6	439.9
Fixed Maturities [Member] \| Credit-Industrial [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	468.5	397.1
Fixed Maturities [Member] \| Credit-Industrial [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	468.5	397.1
Fixed Maturities [Member] \| Credit-Utility [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	150.4	166.6
Fixed Maturities [Member] \| Credit-Utility [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	150.4	166.6
Fixed Maturities [Member] \| CMO/MBS-Agency [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	186.7	226.9
Fixed Maturities [Member] \| CMO/MBS-Agency [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	186.7	226.9
Fixed Maturities [Member] \| CMO/MBS-Non Agency [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	14.6	20.2
Fixed Maturities [Member] \| CMO/MBS-Non Agency [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	14.6	20.2
Fixed Maturities [Member] \| CMBS [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	165.7	164.8
Fixed Maturities [Member] \| CMBS [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	165.7	164.8
Fixed Maturities [Member] \| ABS-Residential [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	4.9	6.6
Fixed Maturities [Member] \| ABS-Residential [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	4.9	6.6
Fixed Maturities [Member] \| ABS-Non Residential [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	209.7	117.2
Fixed Maturities [Member] \| ABS-Non Residential [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	209.7	117.2
Fixed Maturities [Member] \| Foreign Denominated: Governments [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	134.8	206.7
Fixed Maturities [Member] \| Foreign Denominated: Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	134.8	206.7
Fixed Maturities [Member] \| Foreign Denominated: Credit [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	208	155.1
Fixed Maturities [Member] \| Foreign Denominated: Credit [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	208	155.1
Equity Securities [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	511.3	534.3
Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	511.3	534.3
Short-Term Investments [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	356.2	351.6
Short-Term Investments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	356.2	351.6
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	945.9	967.5
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Other Investments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Other Assets [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	'	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	120.8	143.8
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| U.S. Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	120.8	143.8
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| Non-U.S. Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| Obligations of States and Political Subdivisions [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| Credit-Financial [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| Credit-Industrial [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| Credit-Utility [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| CMO/MBS-Agency [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| CMO/MBS-Non Agency [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| CMBS [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| ABS-Residential [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| ABS-Non Residential [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| Foreign Denominated: Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fixed Maturities [Member] \| Foreign Denominated: Credit [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	471	476.7
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Short-Term Investments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	354.1	347
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	2,859.60	2,849.30
Significant Other Observable Inputs (Level 2) [Member] \| Other Investments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	98.1	117.8
Significant Other Observable Inputs (Level 2) [Member] \| Other Assets [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	'	0
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	2,720.10	2,670.60
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| U.S. Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	90	131.5
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| Non-U.S. Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	77	60.2
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| Obligations of States and Political Subdivisions [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	509.2	577.8
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| Credit-Financial [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	500.6	439.9
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| Credit-Industrial [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	468.5	397.1
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| Credit-Utility [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	150.4	166.6
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| CMO/MBS-Agency [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	186.7	226.9
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| CMO/MBS-Non Agency [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	14.6	20.2
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| CMBS [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	165.7	164.8
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| ABS-Residential [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	4.9	6.6
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| ABS-Non Residential [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	209.7	117.2
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| Foreign Denominated: Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	134.8	206.7
Significant Other Observable Inputs (Level 2) [Member] \| Fixed Maturities [Member] \| Foreign Denominated: Credit [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	208	155.1
Significant Other Observable Inputs (Level 2) [Member] \| Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	39.3	56.3
Significant Other Observable Inputs (Level 2) [Member] \| Short-Term Investments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	2.1	4.6
Significant Unobservable Inputs (Level 3) [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	1	3.9
Significant Unobservable Inputs (Level 3) [Member] \| Other Investments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Other Assets [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	'	2.6
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| U.S. Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| Non-U.S. Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| Obligations of States and Political Subdivisions [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| Credit-Financial [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| Credit-Industrial [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| Credit-Utility [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| CMO/MBS-Agency [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| CMO/MBS-Non Agency [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| CMBS [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| ABS-Residential [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| ABS-Non Residential [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| Foreign Denominated: Governments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Fixed Maturities [Member] \| Foreign Denominated: Credit [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	1	1.3
Significant Unobservable Inputs (Level 3) [Member] \| Short-Term Investments [Member] \| Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Fair Value	$0	$0

Investments_Schedule_of_Reconc

Investments - Schedule of Reconciliation of Beginning and Ending Balances for Investments Categorized as Level 3 (Detail) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Beginning balance	$3.90	$8.70
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income (loss)	0	0.1
Included in other comprehensive income (loss)	0	0
Purchases	0	0
Issuances	0	0
Sales	-0.3	-0.6
Settlements	-2.6	-4.3
Ending balance	1	3.9
Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at end of period	0	0
Other Assets [Member]	'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'
Beginning balance	2.6	6.9
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	0
Settlements	-2.6	-4.3
Ending balance	0	2.6
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	1.3	1.8
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income (loss)	0	0.1
Included in other comprehensive income (loss)	0	0
Purchases	0	0
Issuances	0	0
Sales	-0.3	-0.6
Settlements	0	0
Ending balance	1	1.3
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

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Dec. 28, 2011	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2011	Dec. 31, 2013
	Dec. 28, 2011	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Contract	Dec. 31, 2013
Offsetting [Abstract]	'	'	'	'	'	'	'
Number of reinsurance contracts	'	'	'	'	'	1	'
Coverage amount	$100	'	'	'	'	'	'
Coverage period, months	'24 months	'	'	'	'	'	'
Other reinsurance-related expenses	'	0	4.6	0	14.4	'	'
Other assets	'	$0	'	$0	'	'	$2.60

Reserves_for_Losses_and_Loss_A2

Reserves for Losses and Loss Adjustment Expenses - Reinsurance Recoverables (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Liability for Claims and Claims Adjustment Expense [Abstract]	'	'	'
Net reserves beginning of the year	$2,107.60	$2,110.90	'
Losses and LAE incurred during current calendar year, net of reinsurance:	'	'	'
Current accident year	585.9	575.6	'
Prior accident years	-26.4	-21.5	'
Losses and LAE incurred during calendar year, net of reinsurance	559.5	554.1	'
Losses and LAE payments made during current calendar year, net of reinsurance:	'	'	'
Current accident year	115.3	131.7	'
Prior accident years	435.5	429	'
Losses and LAE payments made during current calendar year, net of reinsurance	550.8	560.7	'
Change in participation interest	24.7	10.4	'
Foreign exchange adjustments	-4.9	-6.3	'
Net reserves-end of period	2,136.10	2,108.40	'
Reinsurance recoverables on unpaid losses and LAE, end of period	926.5	1,114.50	'
Gross reserves-end of period	$3,062.60	$3,222.90	$3,230.30	[1]

[1]	Derived from audited consolidated financial statements.

Reserves_for_Losses_and_Loss_A3

Reserves for Losses and Loss Adjustment Expenses - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2012
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]	'	'	'
Net reserves ceded - whole account quota share reinsurance transaction	'	'	$192.20
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	26.4	21.5	'
Commercial Specialty [Member]	'	'	'
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]	'	'	'
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	5.2	0.4	'
Excess and Surplus Lines [Member]	'	'	'
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]	'	'	'
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	34.6	26.8	'
International Specialty [Member]	'	'	'
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]	'	'	'
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	0.1	0.6	'
Syndicate 1200 Segment [Member]	'	'	'
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]	'	'	'
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	15.8	4.1	'
Run-Off Lines [Member]	'	'	'
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]	'	'	'
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	18.9	9.6	'
Medical Malpractice Liability [Member]	'	'	'
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]	'	'	'
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	9	2	'
Unfavorable Development [Member]	'	'	'
Schedule Of Reserves For Losses And Loss Adjustment Expenses [Line Items]	'	'	'
Liability for unpaid claims and claims adjustment expense, incurred claims, prior years	$9.90	$6.40	'

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)	Mar. 07, 2014	Mar. 07, 2014	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Jul. 16, 2014
		New Credit Agreement [Member]	New Credit Agreement [Member]	New Credit Agreement [Member]	New Credit Agreement [Member]	Junior Subordinated Debentures [Member]
					Revolving Credit Facility [Member]
Debt Instrument [Line Items]	'	'	'	'	'	'
Credit agreement with major money center banks, amount	$150,000,000	$175,000,000	'	'	'	'
Revolving credit facility maturity date	'	'	7-Mar-18	'	'	'
Amount drawn under revolving letter of credit	'	200,000	'	'	'	'
Letter of credit facility amount	'	'	0	0	17,500,000	'
Maximum borrowing capacity under revolving credit facility before amendment	150,000,000	'	'	'	'	'
Purchase of outstanding PXRE Capital Trust of junior subordinate notes	'	'	'	'	'	20,000,000
Percentage of discount on principal amount	'	'	'	'	'	90.00%
Purchase price of junior subordinated debt securities	'	'	'	'	'	$18,200,000

Disclosures_about_Fair_Value_o2

Disclosures about Fair Value of Financial Instruments - Additional Information (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financial Instruments Owned and Pledged as Collateral [Line Items]	'	'
Premiums receivable	$396.70	$348.40	[1]
Reinsurance recoverable	1,002.30	1,263.50	[1]
Over 90 Days [Member]	'	'
Financial Instruments Owned and Pledged as Collateral [Line Items]	'	'
Premiums receivable	17.9	9.8
Reinsurance recoverable	13.2	22.2
Premiums receivable, allowance for doubtful accounts	4.9	4.5
Reinsurance recoverables, allowance for doubtful accounts	2	1.6
Premiums receivables, secured by collateral	$0.30	$0.40

[1]	Derived from audited consolidated financial statements.

Disclosures_about_Fair_Value_o3

Disclosures about Fair Value of Financial Instruments - Summary of Company's Financial Instruments Whose Carrying Amount Did Not Equal Fair Value (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Carrying Amount	$380.90	$403.40
Fair Value	345.8	325
Junior Subordinated Debentures [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Carrying Amount	172.7	193.3
Fair Value	155.5	155.5
Senior Unsecured Fixed Rate Notes [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Carrying Amount	143.8	143.8
Fair Value	132.3	116.2
Other Indebtedness [Member] \| Floating Rate Loan Stock [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Carrying Amount	63.8	65.5
Fair Value	57.4	52.7
Other Indebtedness [Member] \| Note Payable [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Carrying Amount	0.6	0.8
Fair Value	$0.60	$0.60

Shareholders_Equity_Additional

Shareholders Equity - Additional Information (Detail) (USD $)

0 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

In Millions, except Share data, unless otherwise specified

Sep. 15, 2014

Aug. 05, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Nov. 13, 2007

Feb. 18, 2011

Nov. 05, 2013

Sep. 30, 2014

Sep. 20, 2013

Aug. 06, 2013

Sep. 30, 2014

2011 Repurchase Authorization [Member]

2013 Repurchase Authorization [Member]

Open Market [Member]

10% Stock Dividend [Member]

Class of Stock [Line Items]

Dividend declared per common share

$0.18

$0.15

$0.51

$0.44

$0.15

Dividend payable, date of record

1-Sep-14

3-Jun-13

2-Sep-13

Cash dividends paid - common shares, total

$4.70

Common stock repurchase authorization, maximum

150

Shares purchased during period, Value

150

101.5

Stock repurchase program, number of shares authorized to be repurchased

Common shares repurchased

206,710

882,010

98,108

301,758

Common shares repurchased, total cost

$10.80

$42.20

$5.20

$14.90

Shareholders_Equity_Schedule_o

Shareholders Equity - Schedule of Repurchase of Shares (Detail) (USD $)	3 Months Ended	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014
Equity, Class of Treasury Stock [Line Items]	'	'
Number of Shares Repurchased	206,710	882,010
Total Cost	$10.80	$42.20
12/17/2013 [Member]	'	'
Equity, Class of Treasury Stock [Line Items]	'	'
Date Trading Plan Initiated	'	17-Dec-13
2014 Purchase Period	'	'02/04/14-02/12/14
Trading Plans Purchase Period Date Range Start	'	'02/04/14
Trading Plans Purchase Period Date Range End	'	'02/12/14
Number of Shares Repurchased	'	15,789
Average Price of Shares Repurchased	'	$43.28
Total Cost	'	0.7
Repurchase Authorization Year	'	'2013
03/18/2014 [Member]	'	'
Equity, Class of Treasury Stock [Line Items]	'	'
Date Trading Plan Initiated	'	18-Mar-14
2014 Purchase Period	'	'03/18/14-04/28/14
Trading Plans Purchase Period Date Range Start	'	'03/18/14
Trading Plans Purchase Period Date Range End	'	'04/28/14
Number of Shares Repurchased	'	436,867
Average Price of Shares Repurchased	'	$45.81
Total Cost	'	20
Repurchase Authorization Year	'	'2013
06/13/2014 [Member]	'	'
Equity, Class of Treasury Stock [Line Items]	'	'
Date Trading Plan Initiated	'	13-Jun-14
2014 Purchase Period	'	'06/17/14-08/04/14
Trading Plans Purchase Period Date Range Start	'	'06/17/14
Trading Plans Purchase Period Date Range End	'	'08/04/14
Number of Shares Repurchased	'	41,362
Average Price of Shares Repurchased	'	$49.94
Total Cost	'	2.1
Repurchase Authorization Year	'	'2013
09/12/2014 [Member]	'	'
Equity, Class of Treasury Stock [Line Items]	'	'
Date Trading Plan Initiated	'	12-Sep-14
2014 Purchase Period	'	'09/16/14-09/30/14
Trading Plans Purchase Period Date Range Start	'	'09/16/14
Trading Plans Purchase Period Date Range End	'	'09/30/14
Number of Shares Repurchased	'	86,234
Average Price of Shares Repurchased	'	$52.17
Total Cost	'	$4.50
Repurchase Authorization Year	'	'2013

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]	'	'	'		'
Beginning balance, Foreign currency translation adjustments	'	'	($11.50)		($8.70)
Other comprehensive income (loss) before reclassifications, Foreign currency translation adjustments	'	'	-1.9		-2.2
Amounts reclassified from accumulated other comprehensive income (loss), Foreign currency translation adjustments	'	'	0		0
Net current-period other comprehensive income (loss), Foreign currency translation adjustments	'	'	-1.9		-2.2
Ending balance, Foreign currency translation adjustments	-13.4	-10.9	-13.4		-10.9
Beginning balance, Unrealized holding gains on securities	'	'	163.9		204.1
Other comprehensive income (loss) before reclassifications, Unrealized holding gains on securities	'	'	5.4		-23.9
Amounts reclassified from accumulated other comprehensive income (loss), Unrealized holding gains on securities	-1.7	-1.3	-14.8		-11.6
Net current-period other comprehensive income (loss), Unrealized holding gains on securities	'	'	-9.4		-35.5
Ending balance, Unrealized holding gains on securities	154.5	168.6	154.5		168.6
Beginning balance, Defined benefit pension plans	'	'	-4.6		-5.9
Other comprehensive income (loss) before reclassifications, Defined benefit pension plans	'	'	0		0
Amounts reclassified from accumulated other comprehensive income (loss), Defined benefit pension plans	'	'	0		0
Net current-period other comprehensive income (loss), Defined benefit pension plans	'	'	0		0
Ending balance, Defined benefit pension plans	-4.6	-5.9	-4.6		-5.9
Beginning balance	'	'	147.8	[1]	189.5
Other comprehensive income (loss) before reclassifications	'	'	3.5		-26.1
Amounts reclassified from accumulated other comprehensive income (loss)	'	'	-14.8		-11.6
Other comprehensive (loss) income, net of tax	-37.9	16.2	-11.3		-37.7
Ending balance	$136.50	$151.80	$136.50		$151.80

[1]	Derived from audited consolidated financial statements.

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Unrealized gains and losses on securities	'	'	'	'
Net realized investment gains	($5.80)	($3.30)	($22)	($18.30)
Provision for income taxes	4.1	2	7.2	6.7
Net of taxes	($1.70)	($1.30)	($14.80)	($11.60)

Net_Income_Per_Common_Share_Ne

Net Income Per Common Share - Net Income Per Common Share on Basic and Diluted Basis (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Net income	$44.70	$31	$123.50	$95.40
Weighted average common shares outstanding - basic	25,956,599	26,682,176	26,203,819	26,961,792
Effect of dilutive securities:	'	'	'	'
Equity compensation awards	480,334	1,137,374	466,357	1,031,543
Weighted average common shares outstanding - diluted	26,436,933	27,819,550	26,670,176	27,993,335
Net income per common share - basic	$1.72	$1.16	$4.71	$3.54
Net income per common share - diluted	$1.69	$1.12	$4.63	$3.41

Net_Income_Per_Common_Share_Ad

Net Income Per Common Share - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Earnings Per Share [Abstract]	'	'	'	'	'
Treasury shares	8,440,355	7,408,601	8,440,355	7,408,601	7,558,345	[1]
Antidilutive securities excluded from computation of diluted net income per share, shares	1,879	58,784	1,879	58,784	'

[1]	Derived from audited consolidated financial statements.

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information - Additional Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Income Taxes Paid, Net [Abstract]	'	'
Income taxes paid	$23.80	$14.10

Supplemental_Cash_Flow_Informa3

Supplemental Cash Flow Information - Schedule of Interest Paid (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Interest Paid [Abstract]	'	'
Senior unsecured fixed rate notes	$7	$7
Junior subordinated debentures	5.8	6
Other indebtedness	2.3	2.1
Total interest paid	$15.10	$15.10

Sharebased_Compensation_Additi

Share-based Compensation - Additional Information (Detail)	9 Months Ended
Share-based Compensation - Additional Information (Detail)	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'
Share-based compensation arrangement by share-based payment award, award vesting period, years	'5 years	'5 years

Sharebased_Compensation_Fair_V

Share-based Compensation - Fair Value Assumptions (Detail)	9 Months Ended
Share-based Compensation - Fair Value Assumptions (Detail)	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'
Risk-free rate of return	1.77%	1.44%
Expected dividend yields	1.49%	1.55%
Expected award life (years)	'4 years 8 months 1 day	'4 years 11 months 1 day
Expected volatility	22.84%	31.12%

Sharebased_Compensation_2014_L

Share-based Compensation - 2014 Long-Term Incentive Plan - Additional Information (Detail) (USD $)

9 Months Ended

1 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

In Millions, except Share data, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

31-May-14

Nov. 30, 2007

31-May-14

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

2007 Plan [Member]

Two Thousand Fourteen Plan [Member]

Restricted Share Units [Member]

Stock-Settled SARs Activity [Member]

Cash-Settled SARs Activity [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [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, additional number of shares authorized

2,800,000

Share-based compensation arrangement by share-based payment award, terms of award

'Share options and SARs will count as one share for the purposes of the limits under the 2014 Plan; 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.

Count of restricted shares, settle in common shares

2.75

Shares available for grant

1,789,004

Term of shares options, (in years)

'Seven years

Share-based compensation arrangement by share-based payment award, award vesting period, years

'5 years

'4 years

'2 years

'4 years

'1 year

'4 years

'1 year

Share-based compensation arrangement by share-based payment award, compensation expense

$0.80

$0.60

$2.20

$0.30

$0.80

$1.60

$2.10

Employee service share-based compensation, unrecognized compensation costs on nonvested awards

7.3

3.6

10.2

Deferred compensation arrangement with individual, compensation expense

$1.20

$1.70

$9.20

$12.70

Sharebased_Compensation_Summar

Share-based Compensation - Summary of Restricted Share Activity (Detail) (Restricted Stock Units (RSUs) [Member], USD $)	9 Months Ended
	Sep. 30, 2014
Restricted Stock Units (RSUs) [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares, Outstanding at January 1, 2014	257,975
Granted, Shares	107,696
Vested and issued, Shares	-58,680
Expired or forfeited, Shares	-35,511
Shares, Outstanding at September 30, 2014	271,480
Weighted-Average Grant Date Fair Value, Outstanding at January 1, 2014	$32.97
Granted, Weighted-Average Grant Date Fair Value	$44.93
Vested and issued, Weighted-Average Grant Date Fair Value	$31.62
Expired or forfeited, Weighted-Average Grant Date Fair Value	$33.08
Weighted-Average Grant Date Fair Value, Outstanding at September 30, 2014	$37.99

Sharebased_Compensation_Summar1

Share-based Compensation - Summary of Stock-Settled SARs Activity (Detail) (Stock-Settled SARs Activity [Member], USD $)	9 Months Ended
	Sep. 30, 2014
Stock-Settled SARs Activity [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares, Outstanding at January 1, 2014	1,288,698
Granted, Shares	188,273
Exercised, Shares	-107,979
Expired or forfeited, Shares	-68,523
Shares, Outstanding at September 30, 2014	1,300,469
Weighted-Average Exercise Price, Outstanding at January 1, 2014	$29.47
Granted, Weighted-Average Exercise Price	$43.23
Exercised, Weighted-Average Exercise Price	$29.40
Expired or forfeited, Weighted-Average Exercise Price	$32.95
Weighted-Average Exercise Price, Outstanding at September 30, 2014	$31.28

Sharebased_Compensation_Summar2

Share-based Compensation - Summary of Cash-Settled SARs Activity (Detail) (Cash-Settled SARs Activity [Member], USD $)	9 Months Ended
	Sep. 30, 2014
Cash-Settled SARs Activity [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares, Outstanding at January 1, 2014	1,743,758
Granted, Shares	756,853
Exercised, Shares	-386,615
Expired or forfeited, Shares	-170,195
Shares, Outstanding at September 30, 2014	1,943,801
Weighted-Average Exercise Price, Outstanding at January 1, 2014	$33
Granted, Weighted-Average Exercise Price	$44.28
Exercised, Weighted-Average Exercise Price	$30.94
Expired or forfeited, Weighted-Average Exercise Price	$35.49
Weighted-Average Exercise Price, Outstanding at September 30, 2014	$37.58

Underwriting_Acquisition_and_I2

Underwriting, Acquisition and Insurance Expenses - Underwriting, Acquisition and Insurance Expenses (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Other Income and Expenses [Abstract]	'	'	'	'
Commissions	$59.80	$57.20	$178	$174.70
General expenses	69	65.4	211.9	200.8
Premium taxes, boards and bureaus	7.2	6.8	19.5	19.7
Underwriting Acquisition and Insurance Expenses, Total	136	129.4	409.4	395.2
Net deferral amortization of policy acquisition costs	-2.2	-2.7	-10.1	-17.2
Total underwriting, acquisition and insurance expenses	$133.80	$126.70	$399.30	$378

Underwriting_Acquisition_and_I3

Underwriting, Acquisition and Insurance Expenses - Additional Information (Detail) (Stock Compensation Plan [Member], USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Stock Compensation Plan [Member]	'	'	'	'
Underwriting Acquisition and Insurance Expense [Line Items]	'	'	'	'
Expense associated with cash settled stock appreciation rights	$2.20	$3.20	$13.30	$17.60

Income_Taxes_Income_Tax_Provis

Income Taxes - Income Tax Provision (Benefit) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Disclosure [Abstract]	'	'	'	'
Current tax provision	($15)	$3.50	($10.70)	$13.40
Future tax deductions	19.7	-2.4	52.9	2
Valuation allowance change	-1.1	0.8	-30	2.4
Income tax provision	$3.60	$1.90	$12.20	$17.80

Income_Taxes_Schedule_of_PreTa

Income Taxes - Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	$48.30	$32.90	$135.70	$113.20
Bermuda [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	27.5	14.2	74.3	34.2
Effective Tax Rate	0.00%	0.00%	0.00%	0.00%
United States [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	13.5	19.6	49.2	68.6
Effective Tax Rate	16.20%	22.90%	20.90%	23.50%
United Kingdom [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	9.2	1.6	11.1	18.3
Effective Tax Rate	15.40%	-164.70%	17.10%	9.20%
Belgium [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	-0.1	0.1	-0.1	0.1
Effective Tax Rate	-7.90%	91.60%	-32.40%	26.90%
Brazil [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	-1.2	-1.5	3.9	-6.2
Effective Tax Rate	0.00%	0.00%	0.00%	0.00%
United Arab Emirates [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	0	-0.4	-0.9	-0.4
Effective Tax Rate	0.00%	0.00%	0.00%	0.00%
Ireland [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	0	-0.1	0	-0.1
Effective Tax Rate	0.00%	0.00%	0.00%	0.00%
Malta [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	-0.8	-0.6	-1.8	-1.3
Effective Tax Rate	0.00%	0.00%	0.00%	0.00%
Switzerland [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax Income	$0.20	$0	$0	$0
Effective Tax Rate	4.80%	19.70%	24.20%	21.00%

Income_Taxes_Schedule_of_PreTa1

Income Taxes - Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates (Parenthetical) (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax income (loss)	$48.30	$32.90	$135.70	$113.20
Switzerland [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax income (loss)	0.2	0	0	0
Maximum [Member] \| Switzerland [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Pre-tax income (loss)	'	$0.10	$0.10	$0.10

Income_Taxes_Reconciliation_of

Income Taxes - Reconciliation of Difference Between Provision for Income Taxes and Expected Tax Provision at Weighted Average Tax Rate (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Examination [Line Items]	'	'	'	'
Income tax provision at expected rate	$6.10	$6.20	$20.60	$25.20
Tax-exempt interest	-1.1	-1.3	-3.4	-4.1
Dividends received deduction	-0.5	-0.7	-1.7	-1.8
Valuation allowance change	-1.1	0.8	-30	2.4
Other permanent adjustments, net	-0.1	-0.5	-1	-1.4
Adjustment for prior year tax return	-1.1	0	-1.1	0
Prior period adjustment to deferred	0.9	0	-0.2	0
United States state tax benefit	0	-0.1	0	-0.4
PXRE Reinsurance capital loss carryforward	0	0	29.8	0
Deferred tax rate reduction	-0.1	-1.3	-0.1	-1.3
Foreign exchange adjustments	-0.2	-1.7	-0.1	-1.3
Foreign withholding taxes	0	0.2	0.3	0.6
Income tax provision	3.6	1.9	12.2	17.8
Income tax provision (benefit) - Foreign	1.5	-2.6	2	1.7
Income tax provision-United States Federal	2.1	4.4	9.8	16.1
Income tax (benefit) provision - United States State	0	-0.1	0.1	-0.6
Foreign withholding tax - United States	0	0.2	0.3	0.6
Income tax provision	3.6	1.9	12.2	17.8
United States [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Adjustment for annualized rate	0.3	0.3	0.5	-0.1
Foreign Country [Member]	'	'	'	'
Income Tax Examination [Line Items]	'	'	'	'
Adjustment for annualized rate	$0.50	$0	($1.40)	$0

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
Income Taxes - Additional Information (Detail) (USD $)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Contingency [Line Items]	'	'	'	'
Total net deferred tax liabilities	$29,400,000	'	$29,400,000	'
Net operating loss carryforward	18,000,000	'	18,000,000	'
Valuation allowance	26,300,000	'	26,300,000	'
Loss carryforwards per year	'	'	2,800,000	'
Increase decrease in valuation allowance	1,100,000	-800,000	30,000,000	-2,400,000
Unrecognized tax benefits	0	0	0	0
Malta [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Valuation allowance	2,100,000	'	2,100,000	'
Increase decrease in valuation allowance	'	'	700,000	'
Brazil [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Valuation allowance	700,000	'	700,000	'
Increase decrease in valuation allowance	'	'	200,000	'
December 31, 2025 [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Loss carryforwards, amounts expiring if not utilized	'	'	16,500,000	'
December 31, 2027 [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Loss carryforwards, amounts expiring if not utilized	'	'	1,500,000	'
PXRE Corporation [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Valuation allowance	16,100,000	'	16,100,000	'
Capital loss carryforward	300,000	'	300,000	'
PXRE Reinsurance Company [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Increase decrease in valuation allowance	'	'	29,800,000	'
ARIS [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Net operating loss carryforward	1,000,000	'	1,000,000	'
ARIS [Member] \| December 31, 2027 [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Loss carryforwards, amounts expiring if not utilized	'	'	200,000	'
ARIS [Member] \| December 31, 2028 [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Loss carryforwards, amounts expiring if not utilized	'	'	400,000	'
ARIS [Member] \| December 31, 2029 [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Loss carryforwards, amounts expiring if not utilized	'	'	$400,000	'

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)	Sep. 30, 2014
In Millions, unless otherwise specified	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Contractual commitments related to its limited partnership investments	$42.40

Segment_Information_Additional

Segment Information - Additional Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
	Segment	Dec. 31, 2013
Segment Reporting [Abstract]	'	'
Number of reportable segments	4	'
Assets associated with trade capital providers	$287.60	$386.80

Segment_Information_Revenue_an

Segment Information - Revenue and Income (Loss) Before Income Taxes for Each Segment (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]	'	'	'	'
Earned premiums	$337.60	$330.50	$999.40	$962.20
Net investment income	20.8	24.1	64.7	77.3
Fee income, net	1.6	0.3	0.1	0.5
Net realized investment and other gains	12.9	9.1	42.5	29.6
Total revenue	372.9	364	1,106.70	1,069.60
Income before income taxes	48.3	32.9	135.7	113.2
Excess and Surplus Lines [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Earned premiums	121.2	120.6	363.9	334.4
Net investment income	8.9	10.2	27.2	32.3
Commercial Specialty [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Earned premiums	72.7	74.6	215.5	225.1
Net investment income	4.5	5.6	13.8	17.6
International Specialty [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Earned premiums	38	37.5	112.6	106.6
Net investment income	2.3	2.4	6.1	6.4
Syndicate 1200 [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Earned premiums	104.4	97.3	305.9	295.6
Net investment income	2.1	2.5	7.9	8.1
Run-Off Lines [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Earned premiums	1.3	0.5	1.5	0.5
Net investment income	2.4	2.6	7.2	8.2
Corporate and Other [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net investment income	0.6	0.8	2.5	4.7
Operating Segments [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Income before income taxes	40.1	39.6	118.6	106.5
Operating Segments [Member] \| Excess and Surplus Lines [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Income before income taxes	27.6	29.6	75.9	60.2
Operating Segments [Member] \| Commercial Specialty [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Income before income taxes	8	10.1	9.2	17.3
Operating Segments [Member] \| International Specialty [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Income before income taxes	4	0.5	16.4	8.1
Operating Segments [Member] \| Syndicate 1200 [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Income before income taxes	8.8	8.5	34.7	26.7
Operating Segments [Member] \| Run-Off Lines [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Income before income taxes	-8.3	-9.1	-17.6	-5.8
Segment Reconciling Items [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net realized investment and other gains	12.9	9.1	42.5	29.6
Segment Reconciling Items [Member] \| Corporate and Other [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Net realized investment and other gains	($4.70)	($15.80)	($25.40)	($22.90)

Segment_Information_Schedule_o

Segment Information - Schedule of Earned Premiums by Geographic Location (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total earned premiums	$337.60	$330.50	$999.40	$962.20
Bermuda [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total earned premiums	27	27.4	75.7	75.3
Brazil [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total earned premiums	11	9.9	35.4	29.9
Malta [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total earned premiums	0.5	0.5	1.6	1.3
United Kingdom [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total earned premiums	104.4	97.7	305.9	296
United States [Member]	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Total earned premiums	$194.70	$195	$580.80	$559.70

Segment_Information_Identifiab

Segment Information - Identifiable Assets (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Identifiable assets	$6,388.60	$6,591	[1]
Excess and Surplus Lines [Member]	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Identifiable assets	2,383.80	2,252.20
Commercial Specialty [Member]	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Identifiable assets	1,287	1,333.40
International Specialty [Member]	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Identifiable assets	771.5	743.6
Syndicate 1200 [Member]	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Identifiable assets	1,287.20	1,638.80
Run-Off Lines [Member]	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Identifiable assets	586.2	555.9
Corporate and Other [Member]	'	'
Segment Reporting, Asset Reconciling Item [Line Items]	'	'
Identifiable assets	$72.90	$67.10

[1]	Derived from audited consolidated financial statements.

Information_Provided_in_Connec2

Information Provided in Connection With Outstanding Debt of Subsidiaries - Additional Information (Detail)	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Ownership Percentage	100.00%

Information_Provided_in_Connec3

Information Provided in Connection with Outstanding Debt of Subsidiaries - Condensed Consolidating Balance Sheet (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013		Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013		Sep. 30, 2013	Dec. 31, 2012
Assets	'	'		'	'
Investments	$4,111.70	$4,079.20	[1]	'	'
Cash	73.1	157.4	[1]	141.6	95.8
Accrued investment income	22.2	25.7	[1]	'	'
Premiums receivable	396.7	348.4	[1]	'	'
Reinsurance recoverables	1,002.30	1,263.50	[1]	'	'
Goodwill and other intangible assets, net	235.5	239.8		'	'
Current income taxes receivable, net	30	0	[1]	'	'
Deferred acquisition costs, net	130	113.9	[1]	'	'
Ceded unearned premiums	227	196.3	[1]	'	'
Other assets	160.1	166.8	[1]	'	'
Due from affiliates	0	0		'	'
Intercompany note receivable	0	0		'	'
Investments in subsidiaries	0	0		'	'
Total assets	6,388.60	6,591	[1]	'	'
Liabilities and Shareholders' Equity	'	'		'	'
Reserves for losses and loss adjustment expenses	3,062.60	3,230.30	[1]	3,222.90	'
Unearned premiums	865.4	779.1	[1]	'	'
Funds held and ceded reinsurance payable, net	238.8	398.4		'	'
Long-term debt	380.9	403.4		'	'
Current income taxes payable, net	0	5.2	[1]	'	'
Deferred tax liabilities, net	55.7	28.7	[1]	'	'
Accrued underwriting expenses and other liabilities	158.3	182.9		'	'
Intercompany note payable	0	0		'	'
Total liabilities	4,761.70	5,028	[1]	'	'
Total shareholders' equity	1,626.90	1,563	[1]	'	'
Total liabilities and shareholders' equity	6,388.60	6,591	[1]	'	'
Consolidating Adjustments [Member]	'	'		'	'
Assets	'	'		'	'
Investments	0	0		'	'
Cash	-18	0		0	0
Accrued investment income	0	0		'	'
Premiums receivable	0	0		'	'
Reinsurance recoverables	0	0		'	'
Goodwill and other intangible assets, net	0	0		'	'
Current income taxes receivable, net	0	0		'	'
Deferred acquisition costs, net	0	0		'	'
Ceded unearned premiums	0	0		'	'
Other assets	-7	0		'	'
Due from affiliates	-7	-3.1		'	'
Intercompany note receivable	0	0		'	'
Investments in subsidiaries	-1,710.80	-1,625.20		'	'
Total assets	-1,742.80	-1,628.30		'	'
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	-20.6	0		'	'
Current income taxes payable, net	'	0		'	'
Deferred tax liabilities, net	0	0		'	'
Accrued underwriting expenses and other liabilities	0	0		'	'
Intercompany note payable	-40.9	-6.6		'	'
Total liabilities	-61.5	-6.6		'	'
Total shareholders' equity	-1,681.30	-1,621.70		'	'
Total liabilities and shareholders' equity	-1,742.80	-1,628.30		'	'
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]	'	'		'	'
Assets	'	'		'	'
Investments	1.9	1.1		'	'
Cash	0	0		0	0
Accrued investment income	0	0		'	'
Premiums receivable	0	0		'	'
Reinsurance recoverables	0	0		'	'
Goodwill and other intangible assets, net	0	0		'	'
Current income taxes receivable, net	0	0		'	'
Deferred acquisition costs, net	0	0		'	'
Ceded unearned premiums	0	0		'	'
Other assets	10.4	4.6		'	'
Due from affiliates	7	3.1		'	'
Intercompany note receivable	0	0		'	'
Investments in subsidiaries	1,710.80	1,625.20		'	'
Total assets	1,730.10	1,634		'	'
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	49	49		'	'
Current income taxes payable, net	'	0		'	'
Deferred tax liabilities, net	0	0		'	'
Accrued underwriting expenses and other liabilities	13.3	15.4		'	'
Intercompany note payable	40.9	6.6		'	'
Total liabilities	103.2	71		'	'
Total shareholders' equity	1,626.90	1,563		'	'
Total liabilities and shareholders' equity	1,730.10	1,634		'	'
Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) [Member]	'	'		'	'
Assets	'	'		'	'
Investments	2,847.80	2,785.10		'	'
Cash	69	132.1		117.5	73.9
Accrued investment income	17.2	19.7		'	'
Premiums receivable	161	150.8		'	'
Reinsurance recoverables	1,188.70	1,145.90		'	'
Goodwill and other intangible assets, net	135.6	137.4		'	'
Current income taxes receivable, net	25.3	0.5		'	'
Deferred acquisition costs, net	58.4	55.6		'	'
Ceded unearned premiums	100.9	88.2		'	'
Other assets	104.1	97.8		'	'
Due from affiliates	-18.8	1.5		'	'
Intercompany note receivable	71.4	87.4		'	'
Investments in subsidiaries	0	0		'	'
Total assets	4,760.60	4,702		'	'
Liabilities and Shareholders' Equity	'	'		'	'
Reserves for losses and loss adjustment expenses	2,160.50	2,157		'	'
Unearned premiums	453.1	425.5		'	'
Funds held and ceded reinsurance payable, net	658.5	642.4		'	'
Long-term debt	288.7	288.9		'	'
Current income taxes payable, net	'	8.9		'	'
Deferred tax liabilities, net	47.1	22.8		'	'
Accrued underwriting expenses and other liabilities	93.5	98.2		'	'
Intercompany note payable	0	0		'	'
Total liabilities	3,701.40	3,643.70		'	'
Total shareholders' equity	1,059.20	1,058.30		'	'
Total liabilities and shareholders' equity	4,760.60	4,702		'	'
Other Subsidiaries and Eliminations [Member]	'	'		'	'
Assets	'	'		'	'
Investments	1,262	1,293		'	'
Cash	22.1	25.3		24.1	21.9
Accrued investment income	5	6		'	'
Premiums receivable	235.7	197.6		'	'
Reinsurance recoverables	-186.4	117.6		'	'
Goodwill and other intangible assets, net	99.9	102.4		'	'
Current income taxes receivable, net	4.7	-0.5		'	'
Deferred acquisition costs, net	71.6	58.3		'	'
Ceded unearned premiums	126.1	108.1		'	'
Other assets	52.6	64.4		'	'
Due from affiliates	18.8	-1.5		'	'
Intercompany note receivable	-71.4	-87.4		'	'
Investments in subsidiaries	0	0		'	'
Total assets	1,640.70	1,883.30		'	'
Liabilities and Shareholders' Equity	'	'		'	'
Reserves for losses and loss adjustment expenses	902.1	1,073.30		'	'
Unearned premiums	412.3	353.6		'	'
Funds held and ceded reinsurance payable, net	-419.7	-244		'	'
Long-term debt	63.8	65.5		'	'
Current income taxes payable, net	'	-3.7		'	'
Deferred tax liabilities, net	8.6	5.9		'	'
Accrued underwriting expenses and other liabilities	51.5	69.3		'	'
Intercompany note payable	0	0		'	'
Total liabilities	1,018.60	1,319.90		'	'
Total shareholders' equity	622.1	563.4		'	'
Total liabilities and shareholders' equity	$1,640.70	$1,883.30		'	'

[1]	Derived from audited consolidated financial statements.

Information_Provided_in_Connec4

Information Provided in Connection with Outstanding Debt of Subsidiaries - Condensed Consolidating Statement of Income (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Premiums and other revenue:	'	'	'	'
Earned premiums	$337.60	$330.50	$999.40	$962.20
Net investment (loss) income	20.8	24.1	64.7	77.3
Fee income, net	1.6	0.3	0.1	0.5
Net realized investment gains (losses) and other	12.9	9.1	42.5	29.6
Total revenue	372.9	364	1,106.70	1,069.60
Expenses:	'	'	'	'
Losses and loss adjustment expenses	191.9	190.9	559.5	554.1
Other reinsurance-related expenses	0	4.6	0	14.4
Underwriting, acquisition and insurance expenses	133.8	126.7	399.3	378
Interest expense	4.9	5.1	15	15.1
Foreign currency exchange loss (gain)	-6	3.8	-2.8	-5.2
Total expenses	324.6	331.1	971	956.4
(Loss) income before income taxes	48.3	32.9	135.7	113.2
Provision for income taxes	3.6	1.9	12.2	17.8
Net (loss) income before equity in earnings of subsidiaries	44.7	31	123.5	95.4
Equity in undistributed earnings of subsidiaries	0	0	0	0
Net income	44.7	31	123.5	95.4
Consolidating Adjustments [Member]	'	'	'	'
Premiums and other revenue:	'	'	'	'
Earned premiums	0	0	0	0
Net investment (loss) income	0	-0.3	0	-0.9
Fee income, net	0	0	0	0
Net realized investment gains (losses) and other	0	0	0	0
Total revenue	0	-0.3	0	-0.9
Expenses:	'	'	'	'
Losses and loss adjustment expenses	0	0	0	0
Other reinsurance-related expenses	'	0	'	0
Underwriting, acquisition and insurance expenses	0	0	0	0
Interest expense	-0.2	-0.3	-0.3	-0.9
Foreign currency exchange loss (gain)	0	0	0	0
Total expenses	-0.2	-0.3	-0.3	-0.9
(Loss) income before income taxes	0.2	0	0.3	0
Provision for income taxes	0	0	0	0
Net (loss) income before equity in earnings of subsidiaries	0.2	0	0.3	0
Equity in undistributed earnings of subsidiaries	-47.9	-37.5	-138.1	-116
Net income	-47.7	-37.5	-137.8	-116
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]	'	'	'	'
Premiums and other revenue:	'	'	'	'
Earned premiums	0	0	0	0
Net investment (loss) income	-0.1	0	-0.3	0
Fee income, net	0	0	0	0
Net realized investment gains (losses) and other	0	0	0	0
Total revenue	-0.1	0	-0.3	0
Expenses:	'	'	'	'
Losses and loss adjustment expenses	0	0	0	0
Other reinsurance-related expenses	'	0	'	0
Underwriting, acquisition and insurance expenses	2.3	5.8	12.5	18.3
Interest expense	0.7	0.7	1.8	2.3
Foreign currency exchange loss (gain)	0	0	0	0
Total expenses	3	6.5	14.3	20.6
(Loss) income before income taxes	-3.1	-6.5	-14.6	-20.6
Provision for income taxes	0	0	0	0
Net (loss) income before equity in earnings of subsidiaries	-3.1	-6.5	-14.6	-20.6
Equity in undistributed earnings of subsidiaries	47.9	37.5	138.1	116
Net income	44.8	31	123.5	95.4
Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) [Member]	'	'	'	'
Premiums and other revenue:	'	'	'	'
Earned premiums	114.2	105.2	343.7	321.2
Net investment (loss) income	13.6	16.7	42.4	57.2
Fee income, net	1.5	-0.6	-1.5	-1.9
Net realized investment gains (losses) and other	9.2	7.2	34.6	32.8
Total revenue	138.5	128.5	419.2	409.3
Expenses:	'	'	'	'
Losses and loss adjustment expenses	69.9	65.9	211.2	194.9
Other reinsurance-related expenses	'	-2.9	'	0
Underwriting, acquisition and insurance expenses	51.6	42.1	147.9	134.3
Interest expense	3.8	3.8	11.4	11.4
Foreign currency exchange loss (gain)	0.3	-0.1	0.1	0.1
Total expenses	125.6	108.8	370.6	340.7
(Loss) income before income taxes	12.9	19.7	48.6	68.6
Provision for income taxes	2.1	4.4	10.2	16
Net (loss) income before equity in earnings of subsidiaries	10.8	15.3	38.4	52.6
Equity in undistributed earnings of subsidiaries	0	0	0	0
Net income	10.8	15.3	38.4	52.6
Other Subsidiaries and Eliminations [Member]	'	'	'	'
Premiums and other revenue:	'	'	'	'
Earned premiums	223.4	225.3	655.7	641
Net investment (loss) income	7.3	7.7	22.6	21
Fee income, net	0.1	0.9	1.6	2.4
Net realized investment gains (losses) and other	3.7	1.9	7.9	-3.2
Total revenue	234.5	235.8	687.8	661.2
Expenses:	'	'	'	'
Losses and loss adjustment expenses	122	125	348.3	359.2
Other reinsurance-related expenses	'	7.5	'	14.4
Underwriting, acquisition and insurance expenses	79.9	78.8	238.9	225.4
Interest expense	0.6	0.9	2.1	2.3
Foreign currency exchange loss (gain)	-6.3	3.9	-2.9	-5.3
Total expenses	196.2	216.1	586.4	596
(Loss) income before income taxes	38.3	19.7	101.4	65.2
Provision for income taxes	1.5	-2.5	2	1.8
Net (loss) income before equity in earnings of subsidiaries	36.8	22.2	99.4	63.4
Equity in undistributed earnings of subsidiaries	0	0	0	0
Net income	$36.80	$22.20	$99.40	$63.40

Information_Provided_in_Connec5

Information Provided in Connection with Outstanding Debt of Subsidiaries - Condensed Consolidating Statement of Cash Flows (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
Condensed Financial Statements, Captions [Line Items]	'		'
Net cash flows from operating activities	$71.70		($3)
Cash flows from investing activities:	'		'
Proceeds from sales of investments	976.1		1,378.80
Proceeds from maturities and mandatory calls of investments	243.6		224.2
Purchases of investments	-1,264.80		-1,407.30
Change in short-term investments and foreign regulatory deposits	6		-75.5
Settlements of foreign currency exchange forward contracts	0.6		-6.4
Issuance of intercompany note, net	0		0
Purchase of fixed assets	-26.7		-19.1
Other, net	-21.5		4.5
Cash (used) provided by investing activities	-86.7		99.2
Cash flows from financing activities:	'		'
Borrowings under intercompany note, net	0		0
Redemption of trust preferred securities, net	-18		0
Payment on note payable	-0.1		0
Activity under stock incentive plans	3.3		1.4
Repurchase of Company's common shares	-40.9		-40.1
Excess tax expense from share-based payment arrangements	0.1		0.2
Payment of cash dividends to common shareholders	-13.4		-11.8
Cash used by financing activities	-69		-50.3
Effect of exchange rate changes on cash	-0.3		-0.1
Change in cash	-84.3		45.8
Cash, beginning of period	157.4	[1]	95.8
Cash, end of period	73.1		141.6
Consolidating Adjustments [Member]	'		'
Condensed Financial Statements, Captions [Line Items]	'		'
Net cash flows from operating activities	6.4		0
Cash flows from investing activities:	'		'
Proceeds from sales of investments	0		0
Proceeds from maturities and mandatory calls of investments	0		0
Purchases of investments	0		0
Change in short-term investments and foreign regulatory deposits	0		0
Settlements of foreign currency exchange forward contracts	0		0
Issuance of intercompany note, net	34		24.9
Purchase of fixed assets	-6.4		0
Other, net	0		0
Cash (used) provided by investing activities	27.6		24.9
Cash flows from financing activities:	'		'
Borrowings under intercompany note, net	-34		-24.9
Redemption of trust preferred securities, net	-18		'
Payment on note payable	0		'
Activity under stock incentive plans	0		0
Repurchase of Company's common shares	0		0
Excess tax expense from share-based payment arrangements	0		0
Payment of cash dividends to common shareholders	0		0
Cash used by financing activities	-52		-24.9
Effect of exchange rate changes on cash	0		0
Change in cash	-18		0
Cash, beginning of period	0		0
Cash, end of period	-18		0
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]	'		'
Condensed Financial Statements, Captions [Line Items]	'		'
Net cash flows from operating activities	-16.5		-15.5
Cash flows from investing activities:	'		'
Proceeds from sales of investments	0		0
Proceeds from maturities and mandatory calls of investments	0		0
Purchases of investments	0		0
Change in short-term investments and foreign regulatory deposits	0.1		-0.8
Settlements of foreign currency exchange forward contracts	-0.5		1.9
Issuance of intercompany note, net	0		0
Purchase of fixed assets	-7		0
Other, net	0		-0.1
Cash (used) provided by investing activities	-7.4		1
Cash flows from financing activities:	'		'
Borrowings under intercompany note, net	34		24.9
Redemption of trust preferred securities, net	0		'
Payment on note payable	0		'
Activity under stock incentive plans	3.3		1.4
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	-13.4		-11.8
Cash used by financing activities	23.9		14.5
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	11.8		75.9
Cash flows from investing activities:	'		'
Proceeds from sales of investments	609.2		863.2
Proceeds from maturities and mandatory calls of investments	148		139
Purchases of investments	-773.1		-942.4
Change in short-term investments and foreign regulatory deposits	-12.5		-38.5
Settlements of foreign currency exchange forward contracts	0		0
Issuance of intercompany note, net	14.5		0
Purchase of fixed assets	-17.7		-17.7
Other, net	-2.4		4.4
Cash (used) provided by investing activities	-34		8
Cash flows from financing activities:	'		'
Borrowings under intercompany note, net	0		0
Redemption of trust preferred securities, net	0		'
Payment on note payable	-0.1		'
Activity under stock incentive plans	0		0
Repurchase of Company's common shares	-40.9		-40.1
Excess tax expense from share-based payment arrangements	0.1		-0.2
Payment of cash dividends to common shareholders	0		0
Cash used by financing activities	-40.9		-40.3
Effect of exchange rate changes on cash	0		0
Change in cash	-63.1		43.6
Cash, beginning of period	132.1		73.9
Cash, end of period	69		117.5
Other Subsidiaries and Eliminations [Member]	'		'
Condensed Financial Statements, Captions [Line Items]	'		'
Net cash flows from operating activities	70		-63.4
Cash flows from investing activities:	'		'
Proceeds from sales of investments	366.9		515.6
Proceeds from maturities and mandatory calls of investments	95.6		85.2
Purchases of investments	-491.7		-464.9
Change in short-term investments and foreign regulatory deposits	18.4		-36.2
Settlements of foreign currency exchange forward contracts	1.1		-8.3
Issuance of intercompany note, net	-48.5		-24.9
Purchase of fixed assets	4.4		-1.4
Other, net	-19.1		0.2
Cash (used) provided by investing activities	-72.9		65.3
Cash flows from financing activities:	'		'
Borrowings under intercompany note, net	0		0
Redemption of trust preferred securities, net	0		'
Payment on note payable	0		'
Activity under stock incentive plans	0		0
Repurchase of Company's common shares	0		0
Excess tax expense from share-based payment arrangements	0		0.4
Payment of cash dividends to common shareholders	0		0
Cash used by financing activities	0		0.4
Effect of exchange rate changes on cash	-0.3		-0.1
Change in cash	-3.2		2.2
Cash, beginning of period	25.3		21.9
Cash, end of period	$22.10		$24.10

[1]	Derived from audited consolidated financial statements.