Argo Group International (ARGO-PA) 10-Q 8 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Aug. 04, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Trading Symbol	AGII
Entity Registrant Name	Argo Group International Holdings, Ltd.
Entity Central Index Key	1,091,748
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		30,139,988

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	[1]
Assets
Fixed maturities available-for-sale, at fair value (cost: 2017 - $3,248.6; 2016 - $2,938.8)	$ 3,276.2	$ 2,932.4
Equity securities available-for-sale, at fair value (cost: 2017 - $321.5; 2016 - $335.2)	442.6	447.4
Other investments (cost: 2017 - $530.0; 2016 - $531.6)	539.4	539
Short-term investments, at fair value (cost: 2017 - $365.9; 2016 - $405.5)	365.9	405.5
Total investments	4,624.1	4,324.3
Cash	214.5	86
Accrued investment income	23	20.7
Premiums receivable	672.6	463.8
Reinsurance recoverables	1,519.6	1,385.6
Goodwill	152.2	152.2
Intangible assets, net of accumulated amortization	108.9	67.7
Deferred acquisition costs, net	162.8	139.1
Ceded unearned premiums	436.6	302.8
Other assets	326.4	262.8
Total assets	8,240.7	7,205
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses	3,632.8	3,350.8
Unearned premiums	1,176.2	970
Accrued underwriting expenses	116	115
Ceded reinsurance payable, net	704.7	466.6
Funds held	40.2	77.1
Senior unsecured fixed rate notes	139.5	139.5
Other indebtedness	182.5	55.4
Junior subordinated debentures	256.4	172.7
Current income taxes payable, net	13.4	8.1
Deferred tax liabilities, net	38.2	24.1
Other liabilities	49.5	33
Total liabilities	6,349.4	5,412.3
Commitments and contingencies (Note 16)	0	0
Shareholders' equity:
Common shares - $1.00 par, 500,000,000 shares authorized; 40,262,441 and 40,042,330 shares issued at June 30, 2017 and December 31, 2016, respectively	40.3	40
Additional paid-in capital	1,125.9	1,123.3
Treasury shares (10,075,255 and 10,028,755 shares at June 30, 2017 and December 31, 2016, respectively)	(381)	(378.2)
Retained earnings	1,026	959.9
Accumulated other comprehensive income, net of taxes	80.1	47.7
Total shareholders' equity	1,891.3	1,792.7
Total liabilities and shareholders' equity	$ 8,240.7	$ 7,205
[1]	Derived from audited consolidated financial statements.

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	[1]
Statement Of Financial Position [Abstract]
Available-for-sale cost	$ 3,248.6	$ 2,938.8
Equity securities cost	321.5	335.2
Other investments cost	530	531.6
Short-term investments, Cost	$ 365.9	$ 405.5
Common shares, par value	$ 1	$ 1
Common shares, shares authorized	500,000,000	500,000,000
Common shares, shares issued	40,262,441	40,042,330
Treasury shares, shares	10,075,255	10,028,755
[1]	Derived from audited consolidated financial statements.

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Premiums and other revenue:
Earned premiums	$ 399.1	$ 344.9	$ 778.5	$ 689.8
Net investment income	43.6	35.7	74.1	56.9
Fee and other income	3.8	5.8	7.4	12.6
Net realized investment and other gains (losses)	4.5	(2.1)	19.1	(4.9)
Total revenue	451	384.3	879.1	754.4
Expenses:
Losses and loss adjustment expenses	230.6	196.6	453.1	388.2
Underwriting, acquisition and insurance expenses	154.7	133	308.3	265.6
Interest expense	7	4.9	12.9	9.7
Fee and other expense	3.3	5.7	7.4	12.2
Foreign currency exchange losses	4.6	4.5	3.9	6
Total expenses	400.2	344.7	785.6	681.7
Income before income taxes	50.8	39.6	93.5	72.7
Provision for income taxes	4.8	8.7	10.8	14.1
Net income	$ 46	$ 30.9	$ 82.7	$ 58.6
Net income per common share:
Basic	$ 1.52	$ 1.03	$ 2.75	$ 1.93
Diluted	1.48	1	2.67	1.89
Dividend declared per common share	$ 0.27	$ 0.22	$ 0.54	$ 0.42
Weighted average common shares:
Basic	30,201,457	30,187,592	30,124,696	30,333,417
Diluted	31,048,081	30,810,156	30,995,172	30,971,189
Net realized investment and other gains before other-than-temporary impairment losses	$ 5.6	$ 2.8	$ 20.6	$ 1.7
Other-than-temporary impairment losses recognized in earnings:
Other-than-temporary impairment losses on fixed maturities	0	(0.5)	0	(1.1)
Other-than-temporary impairment losses on equity securities	(1.1)	(4.4)	(1.5)	(5.5)
Impairment losses recognized in earnings	(1.1)	(4.9)	(1.5)	(6.6)
Net realized investment and other gains (losses)	$ 4.5	$ (2.1)	$ 19.1	$ (4.9)

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 46	$ 30.9	$ 82.7	$ 58.6
Other comprehensive income:
Foreign currency translation adjustments	(1.2)	2.3	(0.6)	3.8
Unrealized gains on securities:
Gains arising during the year	27.5	39.1	61.6	77.9
Reclassification adjustment for gains included in net income	(2.7)	(0.3)	(18.9)	(8.1)
Other comprehensive income before tax	23.6	41.1	42.1	73.6
Unrealized gains on securities:
Gains arising during the year	6.1	12.1	15.9	19.9
Reclassification adjustment for gains included in net income	(1)	0.2	(6.2)	(3.9)
Income tax provision related to other comprehensive income	5.1	12.3	9.7	16
Other comprehensive income, net of tax	18.5	28.8	32.4	57.6
Comprehensive income	$ 64.5	$ 59.7	$ 115.1	$ 116.2

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 82.7		$ 58.6
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Amortization and depreciation	15.9		17.8
Share-based payments expense	7.6		5.6
Deferred income tax (benefit) provision, net	(4.7)		6.1
Net realized investment and other (gains) losses	(19.1)		4.9
Undistributed earnings from alternative investment portfolio	(32.9)		(10.9)
Loss on disposals of fixed assets, net	1.7		0.1
Change in:
Accrued investment income	(2.1)		0.9
Receivables	(103.9)		(185.3)
Deferred acquisition costs	(13.8)		(11.8)
Ceded unearned premiums	(41)		(60.3)
Reserves for losses and loss adjustment expenses	85.4		51
Unearned premiums	53.3		66.5
Ceded reinsurance payable and funds held	57		138.5
Income taxes	5.9		9.1
Accrued underwriting expenses	(21.7)		(23.6)
Other, net	(33)		(35.6)
Cash provided by operating activities	37.3		31.6
Cash flows from investing activities:
Sales of fixed maturity investments	785.8		532
Maturities and mandatory calls of fixed maturity investments	335.1		673.3
Sales of equity securities	107.5		93
Sales of other investments	65.1		5.5
Purchases of fixed maturity investments	(1,381.7)		(1,119)
Purchases of equity securities	(67.5)		(59.6)
Purchases of other investments	(16.8)		(77.1)
Change in foreign regulatory deposits and voluntary pools	(9.5)		2.7
Change in short-term investments	309.9		(13.7)
Settlements of foreign currency exchange forward contracts	0.5		6.8
Acquisition of subsidiaries, net of cash acquired	(105.2)		0
Purchases of fixed assets	(10)		(22.7)
Other, net	(27.7)		(0.9)
Cash (used in) provided by investing activities	(14.5)		20.3
Cash flows from financing activities:
Additional long-term borrowings	125		0
Activity under stock incentive plans	0.5		0.2
Repurchase of Company's common shares	(2.8)		(40)
Payment of cash dividends to common shareholders	(16.6)		(13.1)
Cash provided by (used in) financing activities	106.1		(52.9)
Effect of exchange rate changes on cash	(0.4)		(0.1)
Change in cash	128.5		(1.1)
Cash, beginning of year	86	[1]	121.7
Cash, end of period	$ 214.5		$ 120.6
[1]	Derived from audited consolidated financial statements.

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2017
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 U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions for Form 10-Q and Article 10 of Regulation S-X. 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, 2016, filed with the Securities and Exchange Commission on February 24, 2017. Effective February 6, 2017, we completed the acquisition of Maybrooke Holdings, S.A. (“Maybrooke”) and its direct subsidiaries, including Ariel Re. We have accounted for the acquisition in accordance with Accounting Standards Codification (“ASC”) 805, “Business Combinations,” and the purchase price has been preliminarily allocated to the assets acquired and liabilities assumed based on their estimated fair values at the acquisition date. See Note 3, “Acquisition of Maybrooke,” for additional discussion regarding the acquisition and the related financial disclosures. The Consolidated Financial Statements as of and for the three and six months ended June 30, 2017 and the Notes to the Consolidated Financial Statements reflect the consolidated results of Argo Group and Maybrooke commencing on the date of acquisition. The interim financial information as of, and for the three and six months ended June 30, 2017 and 2016 is unaudited. However, in the opinion of management, the interim information includes all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results presented for the interim periods. The operating results for the interim periods are not necessarily indicative of the results to be expected for the full year. All significant intercompany amounts have been eliminated in consolidation. During the first quarter of 2017, we evaluated and modified the presentation of our reportable segments to better reflect our new operating framework and management structure. Under this model, Argo Group’s chief operating decision maker – Mark E. Watson III, President and Chief Executive Officer – evaluates performance and allocates resources based on the review of the U.S. Operations and the International Operations. The U.S. Operations includes the former Excess & Surplus and Commercial Specialty reportable segments. The International Operations includes the former Syndicate 1200, International Specialty reportable segments, and the recently acquired Ariel Re business. (See Note 3, “Acquisition of Maybrooke” for details regarding Ariel Re.) The business unit that produces the risk and not the location of the underlying exposure is the primary characteristic in distinguishing operating and reportable segments. For example, a U.S. property exposure underwritten through our Syndicate platform would be included in International Operations. Consistent with prior periods, the Run-off Lines and Corporate segments include all other activity of Argo Group and are included in our consolidated financial results. Segment results for the three and six months ended June 30, 2016 have been reclassified to conform to the current presentation.

Recently Issued Accounting Pron

Recently Issued Accounting Pronouncements	6 Months Ended
	Jun. 30, 2017
Accounting Changes And Error Corrections [Abstract]
Recently Issued Accounting Pronouncements	2. Recently Issued Accounting Pronouncements In May 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (ASU) 2017-09, “Compensation – Stock Compensation” (Topic 718): Scope of Modification Accounting. ASU 2017-09 clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. The guidance requires entities to apply the modification accounting guidance if the value, vesting conditions or classification of the award changes. In addition to all the disclosures about modifications that are required today, the entities are required to affirmatively disclose when compensation expense has not changed. The ASU will be applied prospectively and is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted, including in any interim period for which financial statements have not been issued or made available for issuance. We are currently evaluating the impact that the adopting of the ASU will have on our financial results and disclosures. In January 2017, the FASB issued ASU 2017-01, “Business Combination” (Topic 805). ASU 2017-01 clarifies the definition of a business to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The guidance specifies the minimum inputs and processes required to meet the definition of a business. The guidance is effective for annual periods beginning after December 15, 2017, and interim periods within those periods, with early adoption permitted. We do not anticipate that this ASU will have a material impact on our financial results or disclosures. In January 2017, the FASB issued ASU 2017-04, “Intangibles – Goodwill and Other” (Topic 350). ASU 2017-04 eliminates the requirement to calculate the implied fair value of goodwill that is done in Step 2 of the current goodwill impairment test to measure a goodwill impairment loss. Instead, entities will record an impairment loss based on the excess of a reporting unit’s carrying amount over its fair value. The guidance will be applied prospectively and is effective for annual and interim impairment tests performed in periods beginning after December 15, 2019. We do not anticipate that this ASU will have a material impact on our financial results or disclosures. In August 2016, the FASB issued ASU 2016-15, “Classification of Certain Cash Receipts and Cash Payments (Topic 230). ASU 2016-15 will reduce diversity in practice on how eight specific cash receipts and payments are classified on the statement of cash flows. The ASU will be effective for fiscal years beginning after December 15, 2017, including interim periods within those years. This ASU will have an impact on how we present the distributions received from equity method investees in our statement of cash flows. We have elected to adopt the cumulative earnings approach to classify distributions received from equity method investees, which we will adopt retrospectively. We anticipate that this ASU will have no net effect on our consolidated statements of cash flows, but will likely have an immaterial impact on the reclassification of specific cash receipts and payments within the statement. In June 2016, the FASB issued ASU 2016-13, “Measurement of Credit Losses on Financial Instruments” (Topic 326). ASU 2016-13 requires organizations to estimate credit losses on certain types of financial instruments, including receivables and available-for-sale debt securities, by introducing an approach based on expected losses. The expected loss approach will require entities to incorporate considerations of historical information, current information and reasonable and supportable forecasts. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The guidance requires a modified retrospective transition method and early adoption is permitted. We are currently evaluating the impact that the adoption of the ASU will have on our financial results and disclosures, but do not anticipate that any such potential impact would be material. In March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting” (Topic 718). ASU 2016-09 simplifies the accounting for share-based payment award transactions including income tax consequences, classification of awards as either equity or liabilities, classification on the statement of cash flows, and accounting for forfeitures. The ASU is effective for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. We have adopted this ASU as of January 1, 2017, and for presentation purposes, the incremental tax windfall or shortfall associated with these events will be classified as a cash inflow from operating activity as compared with a financing activity, as previously required. The impact to our financial statements was not material. Additionally, we have selected to continue estimating forfeitures based on historical patterns and will true-up the expenses upon vesting. In February 2016, the FASB issued ASU 2016-02, “Leases” (Topic 842). ASU 2016-02 requires organizations that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. Additionally, the ASU modifies current guidance for lessors' accounting. The ASU is effective for interim and annual reporting periods beginning on or after January 1, 2019, with early adoption permitted. We do not anticipate that this ASU will have a material impact on our results of operations, but we anticipate an increase to the value of our assets and liabilities related to leases, with no material impact to equity. In January 2016, the FASB issued ASU 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities” (Subtopic 825-10). ASU 2016-01 will require equity investments that are not consolidated or accounted for under the equity method of accounting to be measured at fair value with changes in fair value recognized in net income. This ASU will also require us to assess the ability to realize our deferred tax assets (“DTAs”) related to an available-for-sale debt security in combination with our other DTAs. The ASU will be effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. While we continue to evaluate the impact of this ASU, we anticipate the standard will increase the volatility of our consolidated statements of income, resulting from the remeasurement of our equity investments. In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers” (Topic 606), which replaces most existing U.S. GAAP revenue recognition guidance and permits the use of either the retrospective or cumulative effect transition method. In August 2015, “Deferral of the Effective Date” (Topic 606), deferred the effective date of this guidance to interim and annual reporting periods beginning after December 15, 2017. Subsequently, in 2016, the FASB issued implementation guidance related to ASU 2014-09, including: • ASU 2016-08, “Principal versus Agent considerations (Reporting Revenue Gross versus Net)” (Topic 606), which is intended to provide further clarification on the application of the principal versus agent implementations; • ASU 2016-10, “Identifying Performance Obligations and Licensing” (Topic 606), which is intended to clarify the guidance for identifying promised goods or service in a contract with a customer; • ASU 2016-11, “Rescission of SEC Guidance Because of Accounting Standards Updates 2014-09 and 2014-16 Pursuant to Staff Announcements at the March 3, 2016 EITF Meeting” (Topic 605) & 815); • ASU 2016-12, “Narrow-Scope Improvements and Practical Expedients” (Topic 606), provides additional guidance for quantitative and qualitative disclosures in certain cases, and make 12 additional technical corrections and improvements to the new revenue standard. While insurance contracts are excluded from this ASU, fee income related to our brokerage operations and management of the third-party capital for our underwriting Syndicate at Lloyd’s will be subject to this updated guidance. We continue to evaluate what impact this ASU will have on our financial results and disclosures and which adoption method to apply, but do not anticipate such impact being material based on the limited revenue streams subject to the ASU.

Acquisition of Maybrooke

Acquisition of Maybrooke	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
Acquisition of Maybrooke	3. Acquisition of Maybrooke Effective February 6, 2017, we completed the acquisition of Maybrooke whereby we acquired all of the issued and outstanding capital stock of Maybrooke. The initial purchase price of $235.3 million was paid in cash from funds on hand and available under our credit facility (see Note 7, “Other Indebtedness”). The initial purchase price was subject to post-closing adjustments based on a final calculation of the purchase price, which we delivered to the seller, as required, within 90 days of closing. As of the date of this filing, we are in discussions with the seller to finalize and agree upon certain changes included in the final purchase price calculation. We anticipate resolving this matter by the end of 2017 and do not expect any material adjustments to the purchase price disclosed below. Through the acquisition of Maybrooke, we acquired Ariel Re, a global underwriter of specialty insurance and reinsurance business written primarily through its Lloyd’s Syndicate 1910. Ariel Re provides Argo Group with a number of strategic advantages, including enhanced scale in its London- and Bermuda-based platforms. The acquisition is being accounting for in accordance with ASC 805, “Business Combinations.” Purchase accounting, as defined by ASC 805, requires that the assets acquired and liabilities assumed be recognized at their fair values as of the acquisition date. We are in the process of finalizing our determination of fair values, including an independent appraisal of certain assets and liabilities, including intangible assets. Therefore, a preliminary allocation of the purchase price to the acquired assets, liabilities, and intangible assets is presented in the table below: (in millions) Assets: Investments $ 340.7 Cash 130.1 Accrued investment income 0.2 Premiums receivable 157.6 Reinsurance recoverables 80.2 Current income taxes receivable 0.6 Deferred acquisition costs, net 9.8 Ceded unearned premiums 92.6 Other assets 24.0 Total assets 835.8 Liabilities: Reserves for losses and loss adjustment expenses 197.0 Unearned premiums 152.5 Accrued underwriting expenses 24.9 Ceded reinsurance payable, net 144.2 Junior subordinated debentures 83.6 Deferred tax liabilities 8.1 Other liabilities 33.7 Total liabilities 644.0 Net assets acquired 191.8 Initial purchase price 235.3 Intangible assets $ 43.5 During the second quarter of 2017, we engaged an independent valuation firm and anticipate completing our valuation analysis and closing the fair value measurement period by the end of 2017. The excess of the purchase price over the fair value of the net assets acquired has been preliminarily allocated to intangible assets, which will be specifically identified and quantified by the end of 2017. We did not record amortization expense related to the $43.5 million intangible assets during the six months ended June 30, 2017, as the valuation analysis has not yet been completed. We anticipate recording both amortizable and non-amortizable identifiable intangible assets and goodwill upon the completion of the valuation analyses, including intangible assets relating to the Lloyd’s Syndicate 1910 stamp capacity (non-amortizable), distribution networks (amortizable), and the Ariel Re tradename (amortizable). Goodwill is calculated as the excess of the purchase price over the fair value of the net assets recognized, including identifiable intangible assets. We recognized approximately $2.5 million of acquisition-related transaction costs in our Consolidated Statements of Income, all of which were recorded during the first quarter of 2017. Of these amounts, $2.2 million were reported in “Underwriting, acquisition and insurance expenses” and $0.3 million in “Interest expense” related to the borrowings under our credit facility to help fund the acquisition. No additional transaction costs were incurred during the three months ended June 30, 2017. Maybrooke’s Contribution to Argo Group’s Revenue and Income The following selected financial information summarizes the results of Maybrooke from the date of acquisition that have been included in our Consolidated Statement of Income: (in millions) For the Three Months Ended June 30, 2017 For the Six Months Ended June 30, 2017 Revenues $ 42.9 $ 66.2 Net income $ 6.4 $ 13.0 Unaudited Pro forma Results of Operations The following unaudited pro forma financial information has been provided to present a summary of the combined results of Argo Group’s operations with Maybrooke’s as if the acquisition had occurred on January 1, 2016. The unaudited pro forma financial information is for informational purposes only and is not necessarily indicative of what the results would have been had the acquisition been completed at the date indicated above, as it may not include all necessary adjustments. Future changes to Maybrooke’s business, such as, but not limited to, the impact from underwriting decisions, changes in risk selection, or retention rates, could result in a material favorable or unfavorable impact on Argo Group’s future results of operations and financial position. The unaudited pro forma results for six months ended June 30, 2017 include favorable development from prior accident years of $6.5 million, including $6.2 million relating to one specific claim in January 2017. In addition, the $2.5 million of nonrecurring transaction costs directly attributable to the acquisition for six months ended June 30, 2017, as disclosed above, have also been removed from the unaudited pro forma results in the table below. The unaudited pro forma results for the three and six months ended June 30, 2016 include the benefits of higher net retention resulting in increased earned premiums and profitability for prior Lloyd’s years of account, partially offset by unfavorable development on claims from prior accident years. For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions, except per share data) 2017 2016 2017 2016 Pro forma revenues $ 449.5 $ 435.3 $ 893.2 $ 874.5 Pro forma net income 46.2 33.3 93.2 76.7 Pro forma net income per share - basic 1.53 1.10 3.09 2.53 Pro forma net income per share - diluted 1.49 1.08 3.01 2.48

Investments

Investments	6 Months Ended
	Jun. 30, 2017
Investments Debt And Equity Securities [Abstract]
Investments	4. Investments Composition of Invested Assets The amortized cost, gross unrealized gains, gross unrealized losses and fair value of investments were as follows: June 30, 2017 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities U.S. Governments $ 317.7 $ 0.6 $ 3.2 $ 315.1 Foreign Governments 244.5 3.3 3.6 244.2 Obligations of states and political subdivisions 337.3 11.9 0.8 348.4 Corporate bonds 1,596.9 26.9 11.9 1,611.9 Commercial mortgage-backed securities 145.0 0.3 1.3 144.0 Residential mortgage-backed securities 221.6 3.4 1.7 223.3 Asset-backed securities 129.7 0.4 1.0 129.1 Collateralized loan obligations 255.9 6.1 1.8 260.2 Total fixed maturities 3,248.6 52.9 25.3 3,276.2 Equity securities 321.5 126.3 5.2 442.6 Other investments 530.0 9.5 0.1 539.4 Short-term investments 365.9 — — 365.9 Total investments $ 4,466.0 $ 188.7 $ 30.6 $ 4,624.1 December 31, 2016 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities U.S. Governments $ 275.1 $ 0.6 $ 4.5 $ 271.2 Foreign Governments 244.2 1.1 8.0 237.3 Obligations of states and political subdivisions 375.7 8.9 1.8 382.8 Corporate bonds 1,316.9 23.3 19.5 1,320.7 Commercial mortgage-backed securities 154.9 0.4 1.6 153.7 Residential mortgage-backed securities 174.8 3.7 1.7 176.8 Asset-backed securities 127.6 0.1 2.1 125.6 Collateralized loan obligations 269.6 3.8 9.1 264.3 Total fixed maturities 2,938.8 41.9 48.3 2,932.4 Equity securities 335.2 117.9 5.7 447.4 Other investments 531.6 7.5 0.1 539.0 Short-term investments 405.5 — — 405.5 Total investments $ 4,211.1 $ 167.3 $ 54.1 $ 4,324.3 Included in “Total investments” in our Consolidated Balance Sheets at June 30, 2017 and December 31, 2016 is $155.7 million and $131.9 million, respectively, of assets managed on behalf of the trade capital providers, who are third-party participants that provide underwriting capital to the operations of Syndicate 1200. Contractual Maturity The amortized cost and fair values of fixed maturity investments as of June 30, 2017, by contractual maturity, were as follows: (in millions) Amortized Cost Fair Value Due in one year or less $ 256.5 $ 253.4 Due after one year through five years 1,463.5 1,475.8 Due after five years through ten years 614.2 623.6 Thereafter 162.2 166.8 Structured securities 752.2 756.6 Total $ 3,248.6 $ 3,276.2 The expected maturities may differ from the contractual maturities because debtors may have the right to call or prepay obligations. Other Invested Assets Details regarding the carrying value and unfunded investment commitments of the other invested assets portfolio as of June 30, 2017 and December 31, 2016 were as follows: June 30, 2017 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 178.6 $ — Private equity 163.3 119.7 Long only funds 195.0 — Other investments 2.5 — Total other invested assets $ 539.4 $ 119.7 December 31, 2016 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 180.9 $ — Private equity 179.0 93.4 Long only funds 170.7 — Other investments 8.4 — Total other invested assets $ 539.0 $ 93.4 The following describes each investment type: • Hedge funds: Hedge funds include funds that primarily buy and sell stocks, including short sales, multi-strategy credit, relative value credit and distressed credit. • Private equity: Private equity includes buyout funds, real asset/infrastructure funds, credit special situations funds, mezzanine lending funds and direct investments and strategic non-controlling minority investments in private companies that are principally accounted for using the equity method of accounting. • Long only funds: Our long only funds include a fund that primarily owns international stocks and funds that primarily own investment-grade corporate and sovereign fixed income securities. • Other investments: Other investments include participation in investment pools, foreign exchange currency forward contracts to manage our foreign currency exposure and a portfolio of foreign exchange currency forward contracts that are actively traded by an external currency manager for a total return strategy. 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: June 30, 2017 Less Than One Year One Year or Greater Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Fixed maturities U.S. Governments $ 267.1 $ 3.1 $ 2.7 $ 0.1 $ 269.8 $ 3.2 Foreign Governments 183.8 3.6 — — 183.8 3.6 Obligations of states and political subdivisions (1) 42.1 0.8 1.8 — 43.9 0.8 Corporate bonds 523.1 10.4 32.9 1.5 556.0 11.9 Commercial mortgage-backed securities 83.7 1.3 4.9 — 88.6 1.3 Residential mortgage-backed securities 110.9 1.6 6.2 0.1 117.1 1.7 Asset-backed securities 68.3 0.5 3.5 0.5 71.8 1.0 Collateralized loan obligations 63.1 1.7 3.0 0.1 66.1 1.8 Total fixed maturities 1,342.1 23.0 55.0 2.3 1,397.1 25.3 Equity securities 52.3 5.2 — — 52.3 5.2 Other investments 0.3 0.1 — — 0.3 0.1 Short-term investments (1) 31.6 — — — 31.6 — Total $ 1,426.3 $ 28.3 $ 55.0 $ 2.3 $ 1,481.3 $ 30.6 December 31, 2016 Less Than One Year One Year or Greater Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Fixed maturities U.S. Governments (2) $ 183.4 $ 4.5 $ — $ — $ 183.4 $ 4.5 Foreign Governments 201.2 8.0 — — 201.2 8.0 Obligations of states and political subdivisions (1) 72.6 1.7 1.8 0.1 74.4 1.8 Corporate bonds 490.5 17.7 50.6 1.8 541.1 19.5 Commercial mortgage-backed securities 70.6 1.5 7.1 0.1 77.7 1.6 Residential mortgage-backed securities (2) 87.5 1.7 4.4 — 91.9 1.7 Asset-backed securities 69.7 1.4 8.2 0.7 77.9 2.1 Collateralized loan obligations 122.5 8.6 16.9 0.5 139.4 9.1 Total fixed maturities 1,298.0 45.1 89.0 3.2 1,387.0 48.3 Equity securities 62.1 5.7 — — 62.1 5.7 Other investments 0.3 0.1 — — 0.3 0.1 Short-term investments 4.8 — — — 4.8 — Total $ 1,365.2 $ 50.9 $ 89.0 $ 3.2 $ 1,454.2 $ 54.1 (1) Unrealized losses less than one year are less than $0.1 million. (2) Unrealized losses one year or greater are less than $0.1 million. We regularly evaluate our investments for other-than-temporary impairment. For fixed maturity securities, the evaluation for a credit loss is generally based on the present value of expected cash flows of the security as compared to the amortized book value. For structured securities, frequency and severity of loss inputs are used in projecting future cash flows of the securities. Loss frequency is measured as the credit default rate, which includes such factors as loan-to-value ratios and credit scores of borrowers. For equity securities and other investments, the length of time and the amount of decline in fair value are the principal factors in determining other-than-temporary impairment. We also recognize other-than-temporary losses on fixed maturity securities that we intend to sell. We hold a total of 7,939 securities, of which 2,043 were in an unrealized loss position for less than one year and 123 were in an unrealized loss position for a period one year or greater as of June 30, 2017. Unrealized losses greater than twelve months on fixed maturities were the result of a number of factors, including increased credit spreads, foreign currency fluctuations and higher market yields relative to the date the securities were purchased, and for structured securities, by the performance of the underlying collateral, as well. In considering whether an investment is other-than-temporarily impaired or not, we also considered that we do not intend to sell the investments and it is unlikely that we will be required to sell the investments before recovery of their amortized cost bases, which may be maturity. In situations where we did not recognize other-than-temporary losses on investments in our equity portfolio, we have evaluated the near-term prospects of the investment in relation to the severity and duration of the impairment and based on that evaluation, have the ability and intent to hold these investments until a recovery of the cost basis. We do not consider these investments to be other-than-temporarily impaired at June 30, 2017. We recognized other-than-temporary losses on our fixed maturities and equity portfolio as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Other-than-temporary impairment: Corporate bonds $ — $ (0.5 ) $ — $ (1.1 ) Equity securities (1.1 ) (4.4 ) (1.5 ) (5.5 ) Other-than-temporary impairment losses $ (1.1 ) $ (4.9 ) $ (1.5 ) $ (6.6 ) Realized Gains and Losses The following table presents our gross realized investment and other gains (losses): For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Realized gains Fixed maturities $ 5.5 $ 4.6 $ 12.6 $ 11.0 Equity securities 12.0 5.3 27.7 24.6 Other investments 4.8 16.8 10.8 27.0 Short-term investments 0.3 0.2 0.5 0.4 Gross realized investment and other gains 22.6 26.9 51.6 63.0 Realized losses Fixed maturities (5.0 ) (6.5 ) (11.2 ) (14.9 ) Equity securities (1.8 ) (1.0 ) (2.5 ) (7.1 ) Other investments (10.2 ) (16.6 ) (17.2 ) (39.2 ) Short-term investments — — (0.1 ) (0.1 ) Other-than-temporary impairment losses on fixed maturities — (0.5 ) — (1.1 ) Other-than-temporary impairment losses on equity securities (1.1 ) (4.4 ) (1.5 ) (5.5 ) Gross realized investment and other losses (18.1 ) (29.0 ) (32.5 ) (67.9 ) Net realized investment and other gains (losses) before income taxes 4.5 (2.1 ) 19.1 (4.9 ) Income tax expense (1.3 ) — (5.7 ) (1.2 ) Net realized investment and other gains (losses), net of income taxes $ 3.2 $ (2.1 ) $ 13.4 $ (6.1 ) The cost of securities sold is based on the specific identification method. Changes in unrealized appreciation (depreciation) related to investments are summarized as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Change in unrealized gains (losses) Fixed maturities $ 19.5 $ 25.9 $ 32.0 $ 64.8 Equity securities 3.3 12.9 8.7 4.0 Other investments 2.0 — 2.0 0.6 Short-term investments — — — 0.4 Net unrealized investment and other gains before income taxes 24.8 38.8 42.7 69.8 Income tax provision (5.1 ) (12.3 ) (9.7 ) (16.0 ) Net unrealized investment and other gains, net of income taxes $ 19.7 $ 26.5 $ 33.0 $ 53.8 Foreign Currency Exchange Forward Contracts We entered into foreign currency exchange forward contracts to manage currency exposure on our Canadian dollar (“CAD”) investment portfolio, minimize negative impacts to our investment portfolio returns, manage currency exposure on certain Euro (“EUR”) denominated investments and gain exposure to a total return strategy which invests in multiple currencies. The fair value of our foreign currency exchange forward contracts as of June 30, 2017 and December 31, 2016 was as follows: (in millions) June 30, 2017 December 31, 2016 Operational currency exposure $ (0.4 ) $ — Asset manager investment exposure (1.1 ) 0.7 Total return strategy (0.5 ) 3.3 $ (2.0 ) $ 4.0 The following table represents our gross investment realized gains and losses on our foreign currency exchange forward contracts: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Realized gains Operational currency exposure $ 3.7 $ 4.6 $ 5.7 $ 7.4 Asset manager investment exposure — 2.3 0.5 2.3 Total return strategy 0.5 9.5 3.6 16.2 Gross realized investment gains 4.2 16.4 9.8 25.9 Realized losses Operational currency exposure (3.7 ) (7.0 ) (5.9 ) (15.5 ) Asset manager investment exposure (5.4 ) — (6.8 ) (3.6 ) Total return strategy (0.8 ) (9.4 ) (2.7 ) (18.6 ) Gross realized investment losses (9.9 ) (16.4 ) (15.4 ) (37.7 ) Net realized investment losses on foreign currency exchange forward contracts $ (5.7 ) $ — $ (5.6 ) $ (11.8 ) Regulatory Deposits, Pledged Securities and Letters of Credit (in millions) June 30, 2017 December 31, 2016 Securities on deposit for regulatory and other purposes $ 176.0 $ 168.7 Securities pledged as collateral for letters of credit 29.1 35.9 Securities and cash on deposit supporting Lloyd’s business 397.2 161.8 Total restricted investments $ 602.3 $ 366.4 Fair Value Measurements Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurement assumes that the transaction to sell the asset or transfer the liability occurs in the principal market for the asset or liability, or in the absence of a principal market, the most advantageous market. Market participants are buyers and sellers in the principal (or most advantageous) market that are independent, knowledgeable, able to transact for the asset or liability and willing to transfer the asset or liability. Valuation techniques consistent with the market approach, income approach and/or cost approach are used to measure fair value. The inputs of these valuation techniques are categorized into three levels. • Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that can be accessed at the reporting date. We define actively traded as a security that has traded in the past seven days. We receive one quote per instrument for Level 1 inputs. • Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. We receive one quote per instrument for Level 2 inputs. • Level 3 inputs are unobservable inputs. Unobservable inputs reflect our own judgments about the assumptions market participants would use in pricing the asset or liability based on the best information available in the circumstances. We receive fair value prices from third-party pricing services and our outside investment managers. These prices are determined using observable market information such as dealer quotes, market spreads, cash flows, yield curves, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things. We have reviewed the processes used by the third-party providers for pricing the securities, and have determined that these processes result in fair values consistent with GAAP requirements. In addition, we review these prices for reasonableness, and have not adjusted any prices received from the third-party providers as of June 30, 2017. A description of the valuation techniques we use to measure assets at fair value is as follows: Fixed Maturities (Available-for-Sale) Levels 1 and 2: • United States Treasury securities are typically valued using Level 1 inputs. For these securities, we obtain fair value measurements from third-party pricing services using quoted prices (unadjusted) in active markets at the reporting date. • United States Government agencies, non-U.S. Government securities, obligations of states and political subdivisions, credit securities and foreign denominated government and credit securities are reported at fair value using Level 2 inputs. For these securities, we obtain fair value measurements from third-party pricing services. Observable data may include dealer quotes, market spreads, yield curves, live trading levels, trade execution data, credit information and the security’s terms and conditions, among other things. • Asset and mortgage-backed securities and collateralized loan obligations are reported at fair value using Level 2 inputs. For these securities, we obtain fair value measurements from third-party pricing services. Observable data may include dealer quotes, market spreads, cash flows, yield curves, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the security’s terms and conditions, among other things. Fixed Maturities (Available-for-Sale) Levels 3: • We own a $1.9 million term loan that is valued using unobservable inputs. Equity Securities Level 1: Equity securities are principally reported at fair value using Level 1 inputs. For these securities, we obtain fair value measurements from a third-party pricing service using quoted prices (unadjusted) in active markets at the reporting date. Equity Securities Level 2: We own interests in a mutual fund that is reported at fair value using Level 2 inputs. The valuation is based on the fund’s net asset value per share, at the end of each month. The underlying assets in the fund are valued primarily on the basis of closing market quotations or official closing prices on each valuation day. Equity Securities Level 3: We own certain equity securities that are reported at fair value using Level 3 inputs. The valuation techniques for these securities include the following: • Fair value measurements are obtained from the National Association of Insurance Commissioners’ Security Valuation Office at the reporting date. • Fair value measurements for an investment in an equity fund obtained by applying final prices provided by the administrator of the fund, which is based upon certain estimates and assumptions. Other Investments Level 2: Foreign regulatory deposits are assets held in trust in jurisdictions where there is a legal and regulatory requirement to maintain funds locally in order to protect policyholders. Lloyd’s is the appointed investment manager for the funds. These assets are invested in short-term government securities, agency securities and corporate bonds and are valued using Level 2 inputs based upon values obtained from Lloyd’s. Foreign currency future contracts are valued by our counterparty using market driven foreign currency exchange rates and are considered Level 2 investments. Short-term Investments: Short-term investments are principally reported at fair value using Level 1 inputs, with the exception of short-term corporate bonds reported at fair value using Level 2 inputs as described in the fixed maturities section above. Values for the investments categorized as Level 1 are obtained from various financial institutions as of the reporting date. Transfers Between Level 1 and Level 2 Securities: There were no transfers between Level 1 and Level 2 securities during the three and six months ended June 30, 2017. Based on an analysis of the inputs, our financial assets measured at fair value on a recurring basis have been categorized as follows: Fair (in millions) June 30, 2017 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities U.S. Governments $ 315.1 $ 292.7 $ 22.4 $ — Foreign Governments 244.2 — 244.2 — Obligations of states and political subdivisions 348.4 — 348.4 — Corporate bonds 1,611.9 — 1,610.0 1.9 Commercial mortgage-backed securities 144.0 — 144.0 — Residential mortgage-backed securities 223.3 — 223.3 — Asset-backed securities 129.1 — 129.1 — Collateralized loan obligations 260.2 — 260.2 — Total fixed maturities 3,276.2 292.7 2,981.6 1.9 Equity securities 442.6 440.1 2.1 0.4 Other investments 108.9 — 108.9 — Short-term investments 365.9 348.9 17.0 — $ 4,193.6 $ 1,081.7 $ 3,109.6 $ 2.3 (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, 2016 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities U.S. Governments $ 271.2 $ 228.0 $ 43.2 $ — Foreign Governments 237.3 — 237.3 — Obligations of states and political subdivisions 382.8 — 382.8 — Corporate bonds 1,320.7 — 1,318.7 2.0 Commercial mortgage-backed securities 153.7 — 153.7 — Residential mortgage-backed securities 176.8 — 176.8 — Asset-backed securities 125.6 — 125.6 — Collateralized loan obligations 264.3 — 264.3 — Total fixed maturities 2,932.4 228.0 2,702.4 2.0 Equity securities 447.4 444.9 2.1 0.4 Other investments 95.5 — 95.5 — Short-term investments 405.5 375.1 30.4 — $ 3,880.8 $ 1,048.0 $ 2,830.4 $ 2.4 (a) Quoted prices in active markets for identical assets (b) Significant other observable inputs (c) Significant unobservable inputs The fair value measurements in the tables above do not equal “Total investments” on our Consolidated Balance Sheets as they exclude certain other investments that are accounted for under the equity-method of accounting. A reconciliation of the beginning and ending balances for the investments categorized as Level 3 are as follows: Fair Value Measurements Using Observable Inputs (Level 3) (in millions) Corporate Bonds Equity Securities Total Beginning balance, January 1, 2017 $ 2.0 $ 0.4 $ 2.4 Transfers into Level 3 — — — Transfers out of Level 3 — — — Total gains or losses (realized/unrealized): Included in net income (loss) — — — Included in other comprehensive income (loss) (0.1 ) — (0.1 ) Purchases, issuances, sales, and settlements: Purchases — — — Issuances — — — Sales — — — Settlements — — — Ending balance, June 30, 2017 $ 1.9 $ 0.4 $ 2.3 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 June 30, 2017 $ — $ — $ — (in millions) Corporate Bonds Equity Securities Total Beginning balance, January 1, 2016 $ — $ 0.7 $ 0.7 Transfers into Level 3 — — — Transfers out of Level 3 — — — Total gains or losses (realized/unrealized): Included in net income (loss) — — — Included in other comprehensive income (loss) — — — Purchases, issuances, sales, and settlements: Purchases 2.0 — 2.0 Issuances — — — Sales — (0.3 ) (0.3 ) Settlements — — — Ending balance, December 31, 2016 $ 2.0 $ 0.4 $ 2.4 Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2016 $ — $ — $ — At June 30, 2017 and December 31, 2016, we did not have any financial assets or financial liabilities measured at fair value on a nonrecurring basis or any financial liabilities on a recurring basis.

Reserves for Losses and Loss Ad

Reserves for Losses and Loss Adjustment Expenses	6 Months Ended
	Jun. 30, 2017
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 Six Months Ended June 30, (in millions) 2017 2016 Net reserves beginning of the year $ 2,180.2 $ 2,133.3 Net Maybrooke reserves acquired 132.6 — Add: Losses and LAE incurred during current calendar year, net of reinsurance: Current accident year 447.4 404.1 Prior accident years 5.7 (15.9 ) Losses and LAE incurred during calendar year, net of reinsurance 453.1 388.2 Deduct: Losses and LAE payments made during current calendar year, net of reinsurance: Current accident year 88.9 65.3 Prior accident years 290.8 300.1 Losses and LAE payments made during current calendar year, net of reinsurance: 379.7 365.4 Change in participation interest (1) (23.2 ) (36.3 ) Foreign exchange adjustments 1.8 4.4 Net reserves - end of period 2,364.8 2,124.2 Add: Reinsurance recoverables on unpaid losses and LAE, end of year 1,268.0 1,057.7 Gross reserves - end of period $ 3,632.8 $ 3,181.9 (1) Amount represents decreases in reserves due to change in syndicate participation Reserves for losses and LAE represent the estimated indemnity cost and related adjustment expenses necessary to investigate and settle claims. Such estimates are based upon individual case estimates for reported claims, estimates from ceding companies for reinsurance assumed and actuarial estimates for losses that have been incurred but not yet reported to the insurer. Any change in probable ultimate liabilities is reflected in current operating results. The impact from the unfavorable (favorable) development of prior accident years’ loss and LAE reserves on each reporting segment is presented below: For the Six Months Ended June 30, (in millions) 2017 2016 U.S. Operations $ (18.0 ) $ (11.9 ) International Operations 19.6 (10.2 ) Run-off Lines 4.1 6.2 Total unfavorable (favorable) prior-year development $ 5.7 $ (15.9 ) The following describes the primary factors behind each segment’s prior accident year reserve development for the six months ended June 30, 2017, and 2016: Six months ended June 30, 2017: • U.S. Operations: Favorable development for workers compensation, surety, commercial auto, and commercial multi-peril lines. • International Operations: Unfavorable development in the property, liability, and specialty lines. • Run-off Lines: Unfavorable development in run-off workers compensation and asbestos liability lines. Six months ended June 30, 2016: • U.S. Operations: Favorable development within commercial automobile lines of business, surety, and general and products liability lines. • International Operations: Favorable development within the property, liability, and professional lines. • Run-off Lines: Unfavorable development in run-off workers compensation and asbestos liability lines, partially offset by favorable development in the run-off reinsurance lines. In the opinion of management, our reserves represent the best estimate of our ultimate liabilities, based on currently known facts, current law, current technology and assumptions considered reasonable where facts are not known. Due to the significant uncertainties and related management judgments, there can be no assurance that future favorable or unfavorable loss development, which may be material, will not occur.

Junior Subordinated Debentures

Junior Subordinated Debentures	6 Months Ended
	Jun. 30, 2017
Junior Subordinated Debentures [Member]
Junior Subordinated Debentures	6. Junior Subordinated Debentures Trust Preferred Debentures Through a series of trusts, that are wholly-owned subsidiaries (non-consolidated), we issued debt. The debentures are variable with the rate being reset quarterly and subject to certain interest rate ceilings. Interest payments are payable quarterly. The debentures are all unsecured and are subordinated to other indebtedness. At June 30, 2017 and December 31, 2016, all debentures were eligible for redemption subject to certain terms and conditions at a price equal to 100% of the principal plus accrued and unpaid interest. A summary of our outstanding junior subordinated debentures is presented below: (in millions) Issue Date Trust Preferred Pools Maturity Rate Structure Interest Rate at June 30, 2017 Amount Argo Group 05/15/2003 PXRE Capital Statutory Trust II 05/15/2033 3M LIBOR + 4.10% 5.28% $ 18.1 11/06/2003 PXRE Capital Trust VI 09/30/2033 3M LIBOR + 3.90% 5.20% 10.3 Argo Group US 05/15/2003 Argonaut Group Statutory Trust I 05/15/2033 3M LIBOR + 4.10% 5.28% 15.5 12/16/2003 Argonaut Group Statutory Trust III 01/08/2034 3M LIBOR + 4.10% 5.26% 12.3 04/29/2004 Argonaut Group Statutory Trust IV 04/29/2034 3M LIBOR + 3.85% 5.03% 13.4 05/26/2004 Argonaut Group Statutory Trust V 05/24/2034 3M LIBOR + 3.85% 5.04% 12.3 05/12/2004 Argonaut Group Statutory Trust VI 05/12/2034 3M LIBOR + 3.80% 5.07% 13.4 09/17/2004 Argonaut Group Statutory Trust VII 12/15/2034 3M LIBOR + 3.60% 4.85% 15.5 09/22/2004 Argonaut Group Statutory Trust VIII 09/22/2034 3M LIBOR + 3.55% 4.84% 15.5 10/22/2004 Argonaut Group Statutory Trust IX 12/15/2034 3M LIBOR + 3.60% 4.85% 15.5 09/15/2005 Argonaut Group Statutory Trust X 09/15/2035 3M LIBOR + 3.40% 4.65% 30.9 Total Outstanding $ 172.7 (in millions) Issue Date Trust Preferred Pools Maturity Rate Structure Interest Rate at December 31, 2016 Amount Argo Group 05/15/2003 PXRE Capital Statutory Trust II 05/15/2033 3M LIBOR + 4.10% 5.00% $ 18.1 11/06/2003 PXRE Capital Trust VI 09/30/2033 3M LIBOR + 3.90% 4.90% 10.3 Argo Group US 05/15/2003 Argonaut Group Statutory Trust I 05/15/2033 3M LIBOR + 4.10% 5.00% 15.5 12/16/2003 Argonaut Group Statutory Trust III 01/08/2034 3M LIBOR + 4.10% 4.98% 12.3 04/29/2004 Argonaut Group Statutory Trust IV 04/29/2034 3M LIBOR + 3.85% 4.76% 13.4 05/26/2004 Argonaut Group Statutory Trust V 05/24/2034 3M LIBOR + 3.85% 4.77% 12.3 05/12/2004 Argonaut Group Statutory Trust VI 05/12/2034 3M LIBOR + 3.80% 4.79% 13.4 09/17/2004 Argonaut Group Statutory Trust VII 12/15/2034 3M LIBOR + 3.60% 4.56% 15.5 09/22/2004 Argonaut Group Statutory Trust VIII 09/22/2034 3M LIBOR + 3.55% 4.55% 15.5 10/22/2004 Argonaut Group Statutory Trust IX 12/15/2034 3M LIBOR + 3.60% 4.56% 15.5 09/15/2005 Argonaut Group Statutory Trust X 09/15/2035 3M LIBOR + 3.40% 4.36% 30.9 Total Outstanding $ 172.7 Maybrooke Junior Subordinated Debentures Unsecured junior subordinated debentures with a principal balance of $91.8 million were assumed through the acquisition of Maybrooke (“the Maybrooke debt”). The Maybrooke debt is carried on our consolidated balance sheet at $83.7 million, which represents our initial estimate of the debt’s fair value at the date of acquisition plus accumulated accretion of discount to par value, as required by accounting for business combinations under ASC 805 (see Note 3, “Acquisition of Maybrooke”). This fair value is subject to change based on finalizing the valuation of Maybrooke’s opening balance sheet by the end of 2017. At June 30, 2017, the Maybrooke debt was eligible for redemption at par. Interest accrues on the Maybrooke debt based on a variable rate, which is reset quarterly. Interest payments are payable quarterly. A summary of the terms of the Maybrooke debt outstanding at June 30, 2017 is presented below: (in millions) Issue Date Maturity Rate Structure Interest Rate at June 30, 2017 Principal at June 30, 2017 Carrying Value at June 30, 2017 9/15/2007 9/15/2037 3 month LIBOR + 3.15% 4.40% $ 91.8 $ 83.7

Other Indebtedness

Other Indebtedness	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Other Indebtedness	7. Other Indebtedness Our Consolidated Balance Sheets includes various long-term debt instruments under the caption “Other indebtedness,” as detailed in the table below. Information regarding the terms and principal amounts of each of these debt instruments is also provided. (in millions) Debt Type June 30, 2017 December 31, 2016 Floating rate loan stock $ 56.9 $ 54.8 Term loan 125.0 — Other debt 0.6 0.6 Total other indebtedness $ 182.5 $ 55.4 Floating Rate Loan Stock This debt was assumed through the acquisition of Lloyd’s Syndicate 1200. These notes are unsecured. At June 30, 2017 and December 31, 2016, all notes were eligible for redemption subject to certain terms and conditions at a price equal to 100% of the principal plus accrued and unpaid interest. Interest on the U.S. Dollar and Euro notes is due semiannually and quarterly, respectively. A summary of the notes outstanding at June 30, 2017 and December 31, 2016 is presented below: (in millions) Issue Date Currency Maturity Rate Structure Interest Rate at June 30, 2017 Amount 12/08/2004 U.S. Dollar 11/15/2034 6 month LIBOR + 4.2% 5.53% $ 6.5 09/06/2005 Euro 08/22/2035 3 month LIBOR + 4.0% 3.67% 13.5 10/31/2006 U.S. Dollar 01/15/2036 6 month LIBOR + 4.0% 5.33% 10.0 10/31/2006 Euro 11/22/2036 3 month LIBOR + 4.0% 3.67% 11.8 06/08/2007 Euro 09/15/2037 3 month LIBOR + 3.9% 3.57% 15.1 $ 56.9 (in millions) Issue Date Currency Maturity Rate Structure Interest Rate at December 31, 2016 Amount 12/08/2004 U.S. Dollar 11/15/2034 6 month LIBOR + 4.2% 5.18% $ 6.5 09/06/2005 Euro 08/22/2035 3 month LIBOR + 4.0% 3.70% 12.8 10/31/2006 U.S. Dollar 01/15/2036 6 month LIBOR + 4.0% 4.98% 10.0 10/31/2006 Euro 11/22/2036 3 month LIBOR + 4.0% 3.70% 11.2 06/08/2007 Euro 09/15/2037 3 month LIBOR + 3.9% 3.58% 14.3 $ 54.8 No principal payments have been made since the acquisition of Lloyd’s Syndicate 1200. The floating rate loan stock denominated in Euros fluctuates due to foreign currency translation. The outstanding balance on these loans was $ million and Borrowing Under Credit Facility On March 3, 2017, each of Argo Group, Argo Group US, Inc., Argo International Holdings Limited and Argo Underwriting Agency Limited (the “Borrowers”) entered into a $325.0 million Credit Agreement (“New Credit Agreement”) with JPMorgan Chase Bank, N.A., as administrative agent. The New Credit Agreement replaced and terminated the previous $175.0 million Credit Agreement (“Prior Agreement”). The New Credit Agreement provides for a $200.0 million revolving credit facility with a maturity date of March 3, 2022 unless extended in accordance with the terms of the New Credit Agreement. In addition, the New Credit Agreement includes a $125.0 million term loan borrowing, which Argo Group used to pay off in its entirety the $125.0 million borrowing drawn on January 31, 2017 under the Prior Agreement to help fund the acquisition of Maybrooke. Interest accrues based on a variable rate, which resets and is payable based on reset options selected by Argo Group pursuant to the terms of the New Credit Agreement. A summary of the terms of the outstanding balance at June 30, 2017 is presented below: (in millions) Issue Date Maturity Rate Structure Interest Rate at June 30, 2017 Amount 3/3/2017 3/3/2019 2 month LIBOR + 1.5% 2.54% $ 125.0 Borrowings under the New Credit Agreement may be used for general corporate purposes, including working capital, permitted acquisitions and letters of credit, and each of the Borrowers has agreed to be jointly and severally liable for the obligations of the other Borrowers under the New Credit Agreement. The New Credit Agreement contains customary events of default. If an event of default occurs and is continuing, the Borrowers could 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 could 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 $200.0 million of the revolving credit facility to be used for LOCs, subject to availability. On March 3, 2017, the $0.2 million LOC outstanding under the Prior Credit Agreement was transferred to the New Credit Agreement. At June 30, 2017 and December 31, 2016, there were no borrowings outstanding under the revolving portions of the credit facilities. At June 30, 2017 and December 31, 2016, there were $0.5 million and $0.2 million, respectively in LOCs against the New and Prior Credit Agreement, respectively. Other Debt As part of the ARIS Title Insurance Corporation (“ARIS”) acquisition, at June 30, 2017 and December 31, 2016 $0.6

Disclosures about Fair Value of

Disclosures about Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Disclosures about Fair Value of Financial Instruments	8. Disclosures about Fair Value of Financial Instruments Cash. The carrying amount approximates fair value. Investment securities and short-term investments . See Note 4, “Investments,” for additional information. Premiums receivable and reinsurance recoverables on paid losses. The carrying value of current receivables approximates fair value. At June 30, 2017 and December 31, 2016, the carrying values of premiums receivable over 90 days were $19.3 million and $14.3 million, respectively. Included in “Reinsurance recoverables” in our Consolidated Balance Sheets at June 30, 2017 and December 31, 2016, are amounts that are due from trade capital providers associated with the operations of Syndicate 1200. Upon settlement, the receivable is offset against the liability which is included in “Ceded reinsurance payable, net” in our accompanying Consolidated Balance Sheets. At June 30, 2017 and December 31, 2016, the payable was in excess of the receivable. Of our reinsurance recoverables on paid losses, excluding amounts attributable to Syndicate 1200’s trade capital providers, at June 30, 2017 and December 31, 2016, the carrying values over 90 days were $12.2 million and $11.2 million, respectively. Our methodology for establishing our allowances for doubtful accounts includes specifically identifying all potential uncollectible balances regardless of aging. At June 30, 2017 and December 31, 2016, the allowance for doubtful accounts for premiums receivable was $2.9 million and $2.7 million, respectively, and the allowance for doubtful accounts for reinsurance recoverables on paid losses was $2.1 million. At June 30, 2017, the amount of premiums receivable over 90 days secured by collateral was negligible. At December 31, 2016, premiums receivable over 90 days were secured by collateral in the amount of $0.1 million. Reinsurance recoverables on paid losses over 90 days were secured by collateral in the amount of $0.6 million at June 30, 2017 and December 31, 2016, respectively. Debt . At June 30, 2017 and December 31, 2016, 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: June 30, 2017 December 31, 2016 (in millions) Carrying Amount Fair Value Carrying Amount Fair Value Junior subordinated debentures Trust preferred debentures $ 172.7 $ 167.5 $ 172.7 $ 162.4 Maybrooke subordinated debenture 83.7 85.2 — — Senior unsecured fixed rate notes 139.5 139.3 139.5 139.3 Floating rate loan stock 56.9 55.1 54.8 51.5

Shareholders' Equity

Shareholders' Equity	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Shareholders' Equity	9 . Shareholders’ Equity On August 8, 2017 our Board of Directors declared a quarterly cash dividend in the amount of $0.27 on each share of common stock outstanding. The cash dividend will be paid on September 15, 2017 to shareholders of record at the close of business on September 1, 2017. On June 1, 2017 our Board of Directors declared a quarterly cash dividend in the amount of $0.27 on each share of common stock outstanding. On June 26, 2017, we paid $8.3 million to our shareholders of record on June 12, 2017. On May 3, 2016, our Board of Directors declared a 10% stock dividend, payable on June 15, 2016, to shareholders of record at the close of business on June 1, 2016. As a result of the stock dividend, 2,735,542 additional shares were issued. Cash was paid in lieu of fractional shares of our common shares. All references to share and per share amounts in this document and related disclosures have been adjusted to reflect the stock dividend for all periods presented. On May 3, 2016 our Board of Directors declared a quarterly cash dividend in the amount of $0.22 on each share of common stock outstanding. On June 17, 2016, we paid $6.9 million to our shareholders of record on June 1, 2016. On May 3, 2016, our Board of Directors authorized the repurchase of up to $150.0 million of our common shares (“2016 Repurchase Authorization”). The 2016 Repurchase Authorization supersedes all the previous Repurchase Authorizations. As of June 30, 2017, availability under the 2016 Repurchase Authorization for future repurchases of our common shares was $127.5 million. For the six months ended June 30, 2017, we repurchased a total of 46,500 common shares for $2.8 million. A summary of activity from January 1, 2017 through June 30, 2017 follows. A summary of common shares repurchased for the six months ended June 30, 2016 is shown below: Repurchase Type Date Trading Plan Initiated 2017 Purchase Period Number of Shares Repurchased Average Price of Shares Repurchased Total Cost (in millions) Repurchase Authorization Year 10b5-1 Trading Plan 6/14/2017 06/20/2017-06/28/2017 46,500 $ 59.54 $ 2.8 2016

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	10. Accumulated Other Comprehensive Income (Loss) A summary of changes in accumulated other comprehensive income (loss), net of taxes (where applicable) by component for the six months ended June 30, 2017, and 2016 is presented below: (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance at January 1, 2017 $ (17.6 ) $ 72.4 $ (7.1 ) $ 47.7 Other comprehensive income (loss) before reclassifications (0.6 ) 45.7 — 45.1 Amounts reclassified from accumulated other comprehensive income (loss) — (12.7 ) — (12.7 ) Net current-period other comprehensive income (loss) (0.6 ) 33.0 — 32.4 Balance at June 30, 2017 $ (18.2 ) $ 105.4 $ (7.1 ) $ 80.1 (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance at January 1, 2016 $ (21.6 ) $ 40.0 $ (6.9 ) $ 11.5 Other comprehensive income (loss) before reclassifications 3.8 58.0 — 61.8 Amounts reclassified from accumulated other comprehensive income (loss) — (4.2 ) — (4.2 ) Net current-period other comprehensive income (loss) 3.8 53.8 — 57.6 Balance at June 30, 2016 $ (17.8 ) $ 93.8 $ (6.9 ) $ 69.1 The following table illustrates the amounts reclassified from accumulated other comprehensive income (loss) shown in the above tables that have been included in our Consolidated Statements of Income: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Unrealized gains on securities: Net realized investment gains $ (2.7 ) $ (0.3 ) $ (18.9 ) $ (8.1 ) Provision for income taxes (benefit) 1.0 (0.2 ) 6.2 3.9 Net of taxes $ (1.7 ) $ (0.5 ) $ (12.7 ) $ (4.2 )

Net Income Per Common Share

Net Income Per Common Share	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Net Income Per Common Share	11 . Net Income Per Common Share The following table presents the calculation of net income per common share on a basic and diluted basis: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions, except number of shares and per share amounts) 2017 2016 2017 2016 Net income $ 46.0 $ 30.9 $ 82.7 $ 58.6 Weighted average common shares outstanding - basic 30,201,457 30,187,592 30,124,696 30,333,417 Effect of dilutive securities: Equity compensation awards 846,624 622,564 870,476 637,772 Weighted average common shares outstanding - diluted 31,048,081 30,810,156 30,995,172 30,971,189 Net income per common share: Basic $ 1.52 $ 1.03 $ 2.75 $ 1.93 Diluted $ 1.48 $ 1.00 $ 2.67 $ 1.89 Excluded from the weighted average common shares outstanding calculation at June 30, 2017 and 2016 are 10,075,255

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	6 Months Ended
	Jun. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	12. Supplemental Cash Flow Information Income taxes paid. We paid income taxes of $9.9 million and $1.3 million during the six months ended June 30, 2017, and 2016, respectively. Income taxes recovered . We recovered income taxes of $2.2 million and $0.3 million during the six months ended June 30, 2017, and 2016, respectively. Interest paid was as follows: For the Six Months Ended June 30, (in millions) 2017 2016 Senior unsecured fixed rate notes $ 4.7 $ 4.7 Junior subordinated debentures 6.0 3.8 Other indebtedness 1.6 1.2 Revolving credit facility 0.3 — Total interest paid $ 12.6 $ 9.7

Share-based Compensation

Share-based Compensation	6 Months Ended
	Jun. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based Compensation	13. Share-based Compensation The fair value method of accounting is used for share-based compensation plans. Under the fair value method, compensation cost is measured based on the fair value of the award at the measurement date and recognized over the requisite service period. We use the Black-Scholes model to estimate the fair values on the measurement date for share options and share appreciation rights (“SARs”). The Black-Scholes model uses several assumptions to value a share award. The risk-free rate of return assumption is based on the five-year U.S. Treasury constant maturity rate on the measurement date. The expected dividend yield is based on our history and expected dividend payouts. The expected award life is based upon the average holding period over the history of the incentive plan. The expected volatility assumption is based on the historical change in our stock price over the previous five years preceding the measurement date. The following table summarizes the assumptions we used for the six months ended June 30, 2017, and 2016 : For the Six Months Ended June 30, 2017 2016 Risk-free rate of return 1.83 % 1.00 % Expected dividend yields 1.68 % 1.70 % Expected award life (years) 4.48 4.54 Expected volatility 18.64 % 19.70 % Argo Group’s Long-Term Incentive Plans In November 2007, our shareholders approved the 2007 Long-Term Incentive Plan (the “2007 Plan”), which provides for an aggregate of 4.5 million shares of our common stock that may be issued to executives, non-employee directors, and other key employees. As of May 2014, 1.46 million shares remained available for grant under the 2007 Plan. In May 2014, our shareholders approved the 2014 Long-Term Incentive Plan (the “2014 Plan”), which provides for an additional 2.8 million shares of our common stock to be available for issuance to executives, non-employee directors and other key employees. The share awards may be in the form of share options, SARs, restricted shares, restricted share awards, restricted share unit awards, performance awards, other share-based awards and other cash-based awards. Shares issued under this plan may be shares that are authorized and unissued or shares that we reacquired, including shares purchased on the open market. Share options and SARs will count as one share for the purposes of the limits under the incentive plans; restricted shares, restricted share units, performance units, performance shares or other share-based incentive awards which settle in common shares will count as 2.75 shares for purpose of the limits under the 2014 Plan. Share options may be in the form of incentive share options, non-qualified share options and restorative options. Share options are required to have an exercise price that is not less than the market value on the date of grant. We are prohibited from repricing the options. The term of the share options cannot exceed seven years from the grant date. Restricted Shares A summary of restricted share activity as of June 30, 2017 and changes during the six months then ended is as follows: Shares Weighted-Average Grant Date Fair Value Outstanding at January 1, 2017 702,030 $ 42.69 Granted 204,467 $ 62.68 Vested and issued (146,878 ) $ 41.47 Expired or forfeited (22,969 ) $ 49.62 Outstanding at June 30, 2017 736,650 $ 48.26 The restricted shares vest over one to eight years. Expense recognized under this plan for the restricted shares was $2.4 million and $5.2 million for the three and six months ended June 30, 2017, respectively, as compared to $1.8 million and $3.5 million for the three and six months ended June 30, 2016, 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 June 30, 2017, there was $25.9 million of total unrecognized compensation cost related to restricted share compensation arrangements granted by Argo Group. Stock-Settled SARs In January 2016, we modified certain unvested cash-settled SARs, converting the awards into stock-settled SARs. We evaluated this modification under the terms of ASU 718 “Share Based Payments,” and determined that no additional expense resulted from the conversion. The expense for the stock-settled SARs will be amortized over the remaining vesting period. A summary of stock-settled SARs activity as of June 30, 2017 and changes during the six months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2017 1,982,695 $ 34.80 Exercised (315,835 ) $ 32.61 Expired or forfeited (58,721 ) $ 40.44 Outstanding at June 30, 2017 1,608,139 $ 35.02 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 $2.0 million and $2.7 Cash-Settled SARs A summary of cash-settled SARs activity as of June 30, 2017 and changes during the six months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2017 500,486 $ 32.08 Exercised (185,359 ) $ 32.90 Expired or forfeited (14,503 ) $ 23.69 Outstanding at June 30, 2017 300,624 $ 31.98 As of June 30, 2017, all the cash-settled SARs are fully vested. 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. Due to a decrease in the fair market value of our stock, we recouped $2.3 million and $0.9

Underwriting, Acquisition and I

Underwriting, Acquisition and Insurance Expenses	6 Months Ended
	Jun. 30, 2017
Underwriting Acquisition And Insurance Expenses [Abstract]
Underwriting, Acquisition and Insurance Expenses	14. Underwriting, Acquisition and Insurance Expenses Underwriting, acquisition and insurance expenses were as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Commissions $ 69.2 $ 62.1 $ 130.4 $ 119.2 General expenses 88.0 71.1 176.7 141.7 Premium taxes, boards and bureaus 6.7 6.3 14.1 12.9 163.9 139.5 321.2 273.8 Net deferral of policy acquisition costs (9.2 ) (6.5 ) (12.9 ) (8.2 ) Total underwriting, acquisition and insurance expenses $ 154.7 $ 133.0 $ 308.3 $ 265.6 The $16.9 million and the $35.0 million increases in general expenses for the three months and six ended June 30, 2017, respectively, as compared to the same periods in 2016 was driven by expenses attributable to the operations of Maybrooke coupled with increased information technology, marketing, occupancy and depreciation costs.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	15. Income Taxes We are incorporated under the laws of Bermuda and, under current Bermuda law, are not obligated to pay any taxes in Bermuda based upon income or capital gains. We have received an undertaking from the Supervisor of Insurance in Bermuda pursuant to the provisions of the Exempted Undertakings Tax Protection Act, 2011, which exempts us from any Bermuda taxes computed on profits, income or any capital asset, gain or appreciation or any tax in the nature of estate duty or inheritance tax, at least until the year 2035. We do not consider ourselves to be engaged in a trade or business in the United States or the United Kingdom and, accordingly, do not expect to be subject to direct United States or United Kingdom income taxation. We have subsidiaries based in the United Kingdom that are subject to the tax laws of that country. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Eight of the United Kingdom subsidiaries are deemed to be engaged in business in the United States, and therefore, are subject to United States corporate tax in respect of a proportion of their United States underwriting business only. Relief is available against the United Kingdom tax liabilities in respect of overseas taxes paid that arise from the underwriting business. Our United Kingdom subsidiaries file separate United Kingdom income tax returns. We have subsidiaries based in the United States that are subject to United States tax laws. Under current law, these subsidiaries are taxed at the applicable corporate tax rates. Our United States subsidiaries file a consolidated United States federal income tax return. We also have operations in Belgium, Switzerland, Brazil, France, Malta, Spain, Ireland, and Luxembourg, which also are subject to income taxes imposed by the jurisdiction in which they operate. We have operations in the United Arab Emirates, which are not subject to income tax under the laws of that country. Our income tax provision includes the following components: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Current tax provision $ 15.5 $ 6.5 $ 15.5 $ 8.0 Deferred tax provision related to: Future tax deductions (9.7 ) 2.0 (3.6 ) 4.9 Valuation allowance change (1.0 ) 0.2 (1.1 ) 1.2 Income tax provision $ 4.8 $ 8.7 $ 10.8 $ 14.1 For the three and six months ended June 30, 2017 and 2016, pre-tax income (loss) attributable to our operations and the operations’ effective tax rates were as follows: For the Three Months Ended June 30, (in millions) 2017 2016 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 25.3 0.0 % $ 22.1 0.0 % United States 34.7 23.3 % 26.5 30.9 % United Kingdom (6.5 ) 52.8 % (9.8 ) -5.7 % Belgium 0.1 36.6 % — (1) 16.3 % Brazil 0.6 0.0 % 0.8 0.0 % United Arab Emirates (2.2 ) 0.0 % — (1) 0.0 % Ireland — (1) 0.0 % (0.1 ) 0.0 % Malta 0.5 0.0 % 0.1 0.0 % Luxembourg (1.7 ) 0.0 % — 0.0 % Switzerland — (1) 22.1 % — (1) 22.8 % Total $ 50.8 9.4 % $ 39.6 22.1 % For the Six Months Ended June 30, (in millions) 2017 2016 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 51.7 0.0 % $ 44.1 0.0 % United States 58.7 24.8 % 49.8 27.5 % United Kingdom (12.0 ) 32.3 % (22.1 ) -1.7 % Belgium 0.1 36.2 % — (1) 32.0 % Brazil (0.2 ) 0.0 % 0.7 0.0 % United Arab Emirates (3.5 ) 0.0 % — (1) 0.0 % Ireland — (1) 0.0 % (0.1 ) 0.0 % Malta 1.1 0.0 % 0.3 0.0 % Luxembourg (2.4 ) 0.0 % — 0.0 % Switzerland — (1) 20.8 % — (1) 21.1 % Total $ 93.5 11.5 % $ 72.7 19.4 % (1) Pre-tax income for the respective year was less than $0.1 million. Our expected income tax provision computed on pre-tax income (loss) at the weighted average tax rate has been calculated as the sum of the pre-tax income (loss) in each jurisdiction multiplied by that jurisdiction’s applicable statutory tax rate. A reconciliation of the difference between the provision for income taxes and the expected tax provision at the weighted average tax rate is as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Income tax provision at expected rate $ 10.8 $ 7.6 $ 18.0 $ 13.4 Tax effect of: Tax-exempt interest (0.7 ) (0.9 ) (1.5 ) (1.8 ) Dividends received deduction (0.4 ) (0.8 ) (0.9 ) (1.3 ) Valuation allowance change (1.0 ) 0.2 (1.1 ) 1.2 Other permanent adjustments, net (1.1 ) — (1.0 ) 0.2 Adjustment for prior period — — (0.7 ) — Adjustment for annualized rate (1.8 ) 0.9 (2.5 ) (0.6 ) Other foreign adjustments (0.4 ) (0.6 ) 0.4 (0.6 ) Deferred tax rate reduction — — — (0.3 ) State income tax 0.1 — 0.1 — Foreign exchange adjustments (0.9 ) 2.1 (0.3 ) 3.6 Foreign withholding taxes 0.2 0.2 0.3 0.3 Income tax provision $ 4.8 $ 8.7 $ 10.8 $ 14.1 Income tax provision - Foreign $ (3.3 ) $ 0.6 $ (3.8 ) $ 0.4 Income tax provision - United States, Federal 7.8 7.9 $ 14.2 13.5 Income tax provision - United States, State 0.1 — 0.1 — Foreign withholding tax - United States 0.2 0.2 0.3 0.2 Income tax provision $ 4.8 $ 8.7 $ 10.8 $ 14.1 Our net deferred tax assets (liabilities) are supported by taxes paid in previous periods, reversal of taxable temporary differences and recognition of future income. Management regularly evaluates the recoverability of the deferred tax assets and makes any necessary adjustments to them based upon any changes in management’s expectations of future taxable income. Realization of deferred tax assets is dependent upon our generation of sufficient taxable income in the future to recover tax benefits that cannot be recovered from taxes paid in the carryback period, generally two years for net operating losses and three years for capital losses for our United States operations. At June 30, 2017, we had a total net deferred tax liability of $13.0 million prior to any valuation allowance. Management has determined that a valuation allowance is required for a portion of the tax-effected net operating loss carryforward included as part of the United States consolidated group of $15.4 million generated from PXRE Corporation and for the tax-effected net operating loss carryforward of $1.0 million from ARIS. The valuation allowances have been established as Internal Revenue Code Section 382 limits the application of net operating loss and net capital loss carryforwards following an ownership change. The loss carryforwards available per year are $2.8 million as required by Internal Revenue Code Section 382. Furthermore, due to cumulative losses since inception, management has concluded that a valuation allowance is required for the full amount of the tax-effected net operating losses generated by our Brazil and Malta entities. Accordingly, a valuation allowance of $25.2 million is required as of June 30, 2017 of which $13.5 million relates to the PXRE Corporation and ARIS loss carryforwards, $8.0 million relates to Brazil operations, $2.7 million relates to Maybrooke, and $1.0 million relates to Malta operations. For the six months ended June 30, 2017, the valuation allowance was reduced by $0.5 million pertaining to the PXRE Corporation and ARIS loss carryforwards, $0.3 million pertaining to our Brazil operations, and $0.3 million pertaining to our Malta operations. Additionally, a $2.7 million valuation allowance was acquired with Maybrooke. Of the PXRE Corporation net operating loss carryforwards, $13.9 million will expire if not used by December 31, 2025 and $1.5 million will expire if not used by December 31, 2027. Of the ARIS loss carryforward, $0.2 million will expire if not used by December 31, 2027, $0.4 million will expire if not used by December 31, 2028 and $0.4 million will expire if not used by December 31, 2029. For any uncertain tax positions not meeting the “more-likely-than-not” recognition threshold, accounting standards require recognition, measurement and disclosure in a company’s financial statements. We had no material unrecognized tax benefits as of June 30, 2017 and 2016. Our United States subsidiaries are no longer subject to U.S. federal and state income tax examinations by tax authorities for years before 2013. Our United Kingdom subsidiaries are no longer subject to United Kingdom income tax examinations by Her Majesty’s Revenue and Customs for years before 2014.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	16. 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 $119.7 million related to our limited partnership investments at June 30, 2017. These commitments will be funded as required by the partnership agreements which can be called to be fulfilled at any time, not to exceed thirteen years.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Segment Information	17. Segment Information We are primarily engaged in underwriting property and casualty insurance and reinsurance. We have two ongoing reporting segments: U.S. Operations and International Operations. Additionally, we have a Run-off Lines segment for certain products that we no longer underwrite. See Note 1, “Basis of Presentation,” for information on the changes to our reporting segments that were effective beginning in the first quarter of 2017. We consider many factors, including the nature of each segment’s insurance and reinsurance products, production sources, distribution strategies and the regulatory environment, in determining how to aggregate reporting segments. In evaluating the operating performance of our segments, we focus on core underwriting and investing results before the consideration of realized gains or losses from the sales of investments. Realized investment gains are reported as a component of the Corporate and Other segment, as decisions regarding the acquisition and disposal of securities reside with the investment function and are not under the control of the individual business segments. Identifiable assets by segment are those assets used in the operation of each segment. Revenue and income (loss) before income taxes for each segment were as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Revenue: Earned premiums U.S. Operations $ 229.1 $ 206.8 $ 450.3 $ 413.4 International Operations 169.9 137.9 328.1 276.2 Run-off Lines 0.1 0.2 0.1 0.2 Total earned premiums 399.1 344.9 778.5 689.8 Net investment income U.S. Operations 27.3 21.7 47.2 35.5 International Operations 10.1 9.1 16.7 15.2 Run-off Lines 2.9 3.4 5.0 5.6 Corporate and Other 3.3 1.5 5.2 0.6 Total net investment income 43.6 35.7 74.1 56.9 Fee and other income 3.8 5.8 7.4 12.6 Net realized investment and other gains (losses) 4.5 (2.1 ) 19.1 (4.9 ) Total revenue $ 451.0 $ 384.3 $ 879.1 $ 754.4 For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Income (loss) before income taxes U.S. Operations $ 53.0 $ 45.4 $ 90.2 $ 80.3 International Operations 9.1 15.3 17.4 33.0 Run-off Lines (1.2 ) (3.2 ) (3.7 ) (4.6 ) Total segment income before taxes 60.9 57.5 103.9 108.7 Corporate and Other (14.6 ) (15.8 ) (29.5 ) (31.1 ) Net realized investment and other gains (losses) 4.5 (2.1 ) 19.1 (4.9 ) Total income before income taxes $ 50.8 $ 39.6 $ 93.5 $ 72.7 The table below presents earned premiums by geographic location for the three and six months ended June 30, 2017 and 2016. For this disclosure, we determine geographic location by the country of domicile of our subsidiaries that underwrite the business and not by the location of insureds or reinsureds from whom the business was generated. For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Bermuda $ 23.1 $ 29.0 $ 48.7 $ 57.1 Brazil 12.3 10.0 25.1 19.2 Malta 1.3 0.5 2.3 1.0 United Kingdom 133.3 98.1 252.1 198.7 United States 229.1 207.3 450.3 413.8 Total earned premiums $ 399.1 $ 344.9 $ 778.5 $ 689.8 The following table represents identifiable assets: (in millions) June 30, 2017 December 31, 2016 U.S. Operations $ 4,127.7 $ 3,961.2 International Operations 3,223.6 2,356.9 Run-off Lines 414.6 537.0 Corporate and Other 474.8 349.9 Total $ 8,240.7 $ 7,205.0 Included in total assets at June 30, 2017 and December 31, 2016 are $690.6 million and $630.4 million, respectively, in assets associated with trade capital providers.

Senior Unsecured Fixed Rate Not

Senior Unsecured Fixed Rate Notes	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Senior Unsecured Fixed Rate Notes	18. Senior Unsecured Fixed Rate Notes In September 2012, Argo Group (the “Parent Guarantor”), through its subsidiary Argo Group US (the “Subsidiary Issuer”), issued $143,750,000 aggregate principal amount of the Subsidiary Issuer’s 6.5% Senior Notes due September 15, 2042 (the “Notes”). The Notes are unsecured and unsubordinated obligations of the Subsidiary Issuer and rank equally in right of payment with all of the Subsidiary Issuer’s other unsecured and unsubordinated debt. The Notes are guaranteed on a full and unconditional senior unsecured basis by the Parent Guarantor. The Notes may be redeemed, for cash, in whole or in part, on or after September 15, 2017, at the Subsidiary Issuer’s option, at any time and from time to time, prior to maturity at a redemption price equal to 100% of the principal amount of the Notes to be redeemed, plus accrued but unpaid interest on the principal amount being redeemed to, but not including, the redemption date. In accordance with ASU 2015-03, “Simplifying the Presentation of Debt Issuance Costs” (Topic 835), we present the unamortized debt issuance costs in the balance sheet as a direct deduction from the carrying value of the debt liability. At June 30, 2017 and December 31, 2016, the Notes consisted of the following: (in millions) June 30, 2017 December 31, 2016 Senior unsecured fixed rate notes Principal $ 143.8 $ 143.8 Less: unamortized debt issuance costs (4.3 ) (4.3 ) Senior unsecured fixed rate notes, less unamortized debt issuance costs $ 139.5 $ 139.5 In accordance with Article 10 of SEC Regulation S-X, we have elected to present condensed consolidating financial information in lieu of separate financial statements for the Subsidiary Issuer. The following tables present condensed consolidating financial information at June 30, 2017 and December 31, 2016 and for the three and six months ended June 30, 2017 and 2016, of the Parent Guarantor and the Subsidiary Issuer. The Subsidiary Issuer is an indirect wholly-owned subsidiary of the Parent Guarantor. Investments in subsidiaries are accounted for by the Parent Guarantor under the equity method for purposes of the supplemental consolidating presentation. Earnings of subsidiaries are reflected in the Parent Guarantor’s investment accounts and earnings. The Parent Guarantor fully and unconditionally guarantees certain of the debt of the Subsidiary Issuer. Condensed consolidating financial information of the Subsidiary Issuer is presented on a consolidated basis and consists principally of the net assets, results of operations and cash flows of operating insurance company subsidiaries. CONDENSED CONSOLIDATING BALANCE SHEET June 30, 2017 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Assets Investments $ 1.2 $ 2,893.8 $ 1,729.1 $ — $ 4,624.1 Cash — 46.2 168.3 — 214.5 Accrued investment income — 17.2 5.8 — 23.0 Premiums receivable — 214.0 458.6 — 672.6 Reinsurance recoverables — 1,386.5 133.1 — 1,519.6 Goodwill and other intangible assets, net 43.5 126.1 91.5 — 261.1 Deferred acquisition costs, net — 74.2 88.6 — 162.8 Ceded unearned premiums — 182.0 254.6 — 436.6 Other assets 8.8 171.4 146.2 — 326.4 Intercompany note receivable — 49.6 70.4 (120.0 ) — Investments in subsidiaries 2,156.4 — — (2,156.4 ) — Total assets $ 2,209.9 $ 5,161.0 $ 3,146.2 $ (2,276.4 ) $ 8,240.7 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — $ 2,354.7 $ 1,278.1 $ — $ 3,632.8 Unearned premiums — 618.4 557.8 — 1,176.2 Funds held and ceded reinsurance payable, net — 736.3 8.6 — 744.9 Long-term debt 153.4 284.4 140.6 — 578.4 Current income taxes payable, net — 11.5 1.9 — 13.4 Deferred tax liabilities, net — 29.8 8.4 — 38.2 Accrued underwriting expenses and other liabilities 11.0 80.5 74.0 — 165.5 Due to affiliates 34.2 5.1 (5.1 ) (34.2 ) — Intercompany note payable 120.0 — — (120.0 ) — Total liabilities 318.6 4,120.7 2,064.3 (154.2 ) 6,349.4 Total shareholders' equity 1,891.3 1,040.3 1,081.9 (2,122.2 ) 1,891.3 Total liabilities and shareholders' equity $ 2,209.9 $ 5,161.0 $ 3,146.2 $ (2,276.4 ) $ 8,240.7 (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 BALANCE SHEET December 31, 2016 (in millions) Argo Group International Holdings, Ltd (Parent Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Assets Investments $ 2.2 $ 2,834.2 $ 1,487.9 $ — $ 4,324.3 Cash — 53.7 32.3 — 86.0 Accrued investment income — 16.0 4.7 — 20.7 Premiums receivable — 204.9 258.9 — 463.8 Reinsurance recoverables — 1,348.4 37.2 — 1,385.6 Goodwill and other intangible assets, net — 127.1 92.8 — 219.9 Deferred acquisition costs, net — 63.5 75.6 — 139.1 Ceded unearned premiums — 168.9 133.9 — 302.8 Other assets 8.7 168.0 86.1 — 262.8 Intercompany note receivable — 50.2 (50.2 ) — — Investments in subsidiaries 1,834.4 — — (1,834.4 ) — Total assets $ 1,845.3 $ 5,034.9 $ 2,159.2 $ (1,834.4 ) $ 7,205.0 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — $ 2,322.4 $ 1,028.4 $ — $ 3,350.8 Unearned premiums — 580.0 390.0 — 970.0 Funds held and ceded reinsurance payable, net — 750.2 (206.5 ) — 543.7 Long-term debt 28.4 284.4 54.8 — 367.6 Current income taxes payable, net — 8.5 (0.4 ) — 8.1 Deferred tax liabilities, net — 17.6 6.5 — 24.1 Accrued underwriting expenses and other liabilities 13.7 92.0 42.3 — 148.0 Due to affiliates 10.5 1.8 (1.8 ) (10.5 ) — Total liabilities 52.6 4,056.9 1,313.3 (10.5 ) 5,412.3 Total shareholders' equity 1,792.7 978.0 845.9 (1,823.9 ) 1,792.7 Total liabilities and shareholders' equity $ 1,845.3 $ 5,034.9 $ 2,159.2 $ (1,834.4 ) $ 7,205.0 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE THREE MONTHS ENDED JUNE 30, 2017 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 135.5 $ 263.6 $ — $ 399.1 Net investment (expense) income (0.4 ) 29.3 14.7 — 43.6 Fee and other income — 2.9 0.9 — 3.8 Net realized investment and other gains (losses) — 5.2 (0.7 ) — 4.5 Total revenue (0.4 ) 172.9 278.5 — 451.0 Expenses: Losses and loss adjustment expenses — 72.5 158.1 — 230.6 Underwriting, acquisition and insurance expenses 3.8 58.5 92.4 — 154.7 Interest expense 1.1 4.2 1.7 — 7.0 Fee and other expense — 3.2 0.1 — 3.3 Foreign currency exchange (gains) loss — (0.1 ) 4.7 — 4.6 Total expenses 4.9 138.3 257.0 — 400.2 (Loss) Income before income taxes (5.3 ) 34.6 21.5 — 50.8 Provision for income taxes — 8.1 (3.3 ) — 4.8 Net (loss) income before equity in earnings of subsidiaries (5.3 ) 26.5 24.8 — 46.0 Equity in undistributed earnings of subsidiaries 51.3 — — (51.3 ) — Net income $ 46.0 $ 26.5 $ 24.8 $ (51.3 ) $ 46.0 CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE THREE MONTHS ENDED JUNE 30, 2016 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 120.2 $ 224.7 $ — $ 344.9 Net investment (expense) income (0.5 ) 27.5 8.7 — 35.7 Fee and other income — 4.2 1.6 — 5.8 Net realized investment and other gains (losses) 0.2 1.9 (4.2 ) — (2.1 ) Total revenue (0.3 ) 153.8 230.8 — 384.3 Expenses: Losses and loss adjustment expenses — 69.1 127.5 — 196.6 Underwriting, acquisition and insurance expenses 1.1 49.0 82.9 — 133.0 Interest expense 0.4 3.9 0.6 — 4.9 Fee and other expense — 5.0 0.7 — 5.7 Foreign currency exchange (gains) loss — (0.1 ) 4.6 — 4.5 Total expenses 1.5 126.9 216.3 — 344.7 (Loss) Income before income taxes (1.8 ) 26.9 14.5 — 39.6 Provision for income taxes — 8.3 0.4 — 8.7 Net (loss) income before equity in earnings of subsidiaries (1.8 ) 18.6 14.1 — 30.9 Equity in undistributed earnings of subsidiaries 32.7 — — (32.7 ) — Net income $ 30.9 $ 18.6 $ 14.1 $ (32.7 ) $ 30.9 CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE SIX MONTHS ENDED JUNE 30, 2017 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 266.4 $ 512.1 $ — $ 778.5 Net investment (expense) income (2.1 ) 48.2 28.0 — 74.1 Fee and other income — 5.7 1.7 — 7.4 Net realized investment and other gains (losses) 0.5 19.0 (0.4 ) — 19.1 Total revenue (1.6 ) 339.3 541.4 — 879.1 Expenses: Losses and loss adjustment expenses — 148.6 304.5 — 453.1 Underwriting, acquisition and insurance expenses 12.2 116.7 179.4 — 308.3 Interest expense 1.4 8.5 3.0 — 12.9 Fee and other expense — 6.6 0.8 — 7.4 Foreign currency exchange loss — — 3.9 — 3.9 Total expenses 13.6 280.4 491.6 — 785.6 (Loss) Income before income taxes (15.2 ) 58.9 49.8 — 93.5 Provision for income taxes — 14.5 (3.7 ) — 10.8 Net (loss) income before equity in earnings of subsidiaries (15.2 ) 44.4 53.5 — 82.7 Equity in undistributed earnings of subsidiaries 97.9 — — (97.9 ) — Net income $ 82.7 $ 44.4 $ 53.5 $ (97.9 ) $ 82.7 (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 SIX MONTHS ENDED JUNE 30, 2016 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 240.1 $ 449.7 $ — $ 689.8 Net investment (expense) income (1.1 ) 40.1 17.9 — 56.9 Fee and other income — 9.4 3.2 — 12.6 Net realized investment and other gains (losses) 0.2 13.1 (18.2 ) — (4.9 ) Total revenue (0.9 ) 302.7 452.6 — 754.4 Expenses: Losses and loss adjustment expenses — 137.4 250.8 — 388.2 Underwriting, acquisition and insurance expenses 6.3 96.6 162.7 — 265.6 Interest expense 0.7 7.8 1.2 — 9.7 Fee and other expense — 11.2 1.0 — 12.2 Foreign currency exchange (gains) loss — (0.1 ) 6.1 — 6.0 Total expenses 7.0 252.9 421.8 — 681.7 (Loss) Income before income taxes (7.9 ) 49.8 30.8 — 72.7 Provision for income taxes — 13.7 0.4 — 14.1 Net (loss) income before equity in earnings of subsidiaries (7.9 ) 36.1 30.4 — 58.6 Equity in undistributed earnings of subsidiaries 66.5 — — (66.5 ) — Net income $ 58.6 $ 36.1 $ 30.4 $ (66.5 ) $ 58.6 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE SIX MONTHS ENDED JUNE 30, 2017 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Net cash flows from (used in) operating activities $ 5.3 $ (8.0 ) $ 40.0 $ — $ 37.3 Cash flows from investing activities: Proceeds from sales of investments — 514.4 444.0 — 958.4 Maturities and mandatory calls of fixed maturity investments — 240.6 94.5 — 335.1 Purchases of investments — (811.0 ) (655.0 ) — (1,466.0 ) Change in short-term investments and foreign regulatory deposits 0.4 72.0 228.0 — 300.4 Settlements of foreign currency exchange forward contracts 0.8 — (0.3 ) — 0.5 Acquisition of subsidiaries, net of cash (235.3 ) — 130.1 — (105.2 ) Issuance of intercompany note, net — — (120.0 ) 120.0 — Purchases of fixed assets and other, net (0.1 ) (12.7 ) (24.9 ) — (37.7 ) Cash (used in) provided by investing activities (234.2 ) 3.3 96.4 120.0 (14.5 ) Cash flows from financing activities: Additional long-term borrowings 125.0 — — — 125.0 Borrowing under intercompany note, net 120.0 — — (120.0 ) — Activity under stock incentive plans 0.5 — — — 0.5 Repurchase of Company's common shares — (2.8 ) — — (2.8 ) Payment of cash dividend to common shareholders (16.6 ) — — — (16.6 ) Cash provided by (used in) financing activities 228.9 (2.8 ) — (120.0 ) 106.1 Effect of exchange rate changes on cash — — (0.4 ) — (0.4 ) Change in cash — (7.5 ) 136.0 — 128.5 Cash, beginning of year — 53.7 32.3 — 86.0 Cash, end of period $ — $ 46.2 $ 168.3 $ — $ 214.5 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE SIX MONTHS ENDED JUNE 30, 2016 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Net cash flows from (used in) operating activities $ 14.7 $ (9.2 ) $ 26.1 $ — $ 31.6 Cash flows from investing activities: Proceeds from sales of investments — 490.0 140.5 — 630.5 Maturities and mandatory calls of fixed maturity investments — 296.9 376.4 — 673.3 Purchases of investments — (720.1 ) (535.6 ) — (1,255.7 ) Change in short-term investments and foreign regulatory deposits (1.8 ) (12.3 ) 3.1 — (11.0 ) Settlements of foreign currency exchange forward contracts — — 6.8 — 6.8 Purchases of fixed assets and other, net — (11.2 ) (12.4 ) — (23.6 ) Cash (used in) provided by investing activities (1.8 ) 43.3 (21.2 ) — 20.3 Cash flows from financing activities: Activity under stock incentive plans 0.2 — — — 0.2 Repurchase of Company's common shares — (40.0 ) — — (40.0 ) Payment of cash dividend to common shareholders (13.1 ) — — — (13.1 ) Cash used in financing activities (12.9 ) (40.0 ) — — (52.9 ) Effect of exchange rate changes on cash — — (0.1 ) — (0.1 ) Change in cash — (5.9 ) 4.8 — (1.1 ) Cash, beginning of year — 88.8 32.9 — 121.7 Cash, end of period $ — $ 82.9 $ 37.7 $ — $ 120.6 (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)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements of Argo Group International Holdings, Ltd. (“Argo Group,” “we” or the “Company”) and its subsidiaries have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions for Form 10-Q and Article 10 of Regulation S-X. 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, 2016, filed with the Securities and Exchange Commission on February 24, 2017. Effective February 6, 2017, we completed the acquisition of Maybrooke Holdings, S.A. (“Maybrooke”) and its direct subsidiaries, including Ariel Re. We have accounted for the acquisition in accordance with Accounting Standards Codification (“ASC”) 805, “Business Combinations,” and the purchase price has been preliminarily allocated to the assets acquired and liabilities assumed based on their estimated fair values at the acquisition date. See Note 3, “Acquisition of Maybrooke,” for additional discussion regarding the acquisition and the related financial disclosures. The Consolidated Financial Statements as of and for the three and six months ended June 30, 2017 and the Notes to the Consolidated Financial Statements reflect the consolidated results of Argo Group and Maybrooke commencing on the date of acquisition. The interim financial information as of, and for the three and six months ended June 30, 2017 and 2016 is unaudited. However, in the opinion of management, the interim information includes all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results presented for the interim periods. The operating results for the interim periods are not necessarily indicative of the results to be expected for the full year. All significant intercompany amounts have been eliminated in consolidation. During the first quarter of 2017, we evaluated and modified the presentation of our reportable segments to better reflect our new operating framework and management structure. Under this model, Argo Group’s chief operating decision maker – Mark E. Watson III, President and Chief Executive Officer – evaluates performance and allocates resources based on the review of the U.S. Operations and the International Operations. The U.S. Operations includes the former Excess & Surplus and Commercial Specialty reportable segments. The International Operations includes the former Syndicate 1200, International Specialty reportable segments, and the recently acquired Ariel Re business. (See Note 3, “Acquisition of Maybrooke” for details regarding Ariel Re.) The business unit that produces the risk and not the location of the underlying exposure is the primary characteristic in distinguishing operating and reportable segments. For example, a U.S. property exposure underwritten through our Syndicate platform would be included in International Operations. Consistent with prior periods, the Run-off Lines and Corporate segments include all other activity of Argo Group and are included in our consolidated financial results. Segment results for the three and six months ended June 30, 2016 have been reclassified to conform to the current presentation.

Acquisition of Maybrooke (Table

Acquisition of Maybrooke (Tables)	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
Schedule of Preliminarily Allocation of Purchase Price to Acquired Assets, Liabilities, and Intangible Assets	Therefore, a preliminary allocation of the purchase price to the acquired assets, liabilities, and intangible assets is presented in the table below: (in millions) Assets: Investments $ 340.7 Cash 130.1 Accrued investment income 0.2 Premiums receivable 157.6 Reinsurance recoverables 80.2 Current income taxes receivable 0.6 Deferred acquisition costs, net 9.8 Ceded unearned premiums 92.6 Other assets 24.0 Total assets 835.8 Liabilities: Reserves for losses and loss adjustment expenses 197.0 Unearned premiums 152.5 Accrued underwriting expenses 24.9 Ceded reinsurance payable, net 144.2 Junior subordinated debentures 83.6 Deferred tax liabilities 8.1 Other liabilities 33.7 Total liabilities 644.0 Net assets acquired 191.8 Initial purchase price 235.3 Intangible assets $ 43.5
Summary of Selected Financial Information and Pro Forma Results	The following selected financial information summarizes the results of Maybrooke from the date of acquisition that have been included in our Consolidated Statement of Income: (in millions) For the Three Months Ended June 30, 2017 For the Six Months Ended June 30, 2017 Revenues $ 42.9 $ 66.2 Net income $ 6.4 $ 13.0 For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions, except per share data) 2017 2016 2017 2016 Pro forma revenues $ 449.5 $ 435.3 $ 893.2 $ 874.5 Pro forma net income 46.2 33.3 93.2 76.7 Pro forma net income per share - basic 1.53 1.10 3.09 2.53 Pro forma net income per share - diluted 1.49 1.08 3.01 2.48 The unaudited pro forma results for the three and six months ended June 30, 2016 include the benefits of higher net retention resulting in increased earned premiums and profitability for prior Lloyd’s years of account, partially offset by unfavorable development on claims from prior accident years.

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2017
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: June 30, 2017 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities U.S. Governments $ 317.7 $ 0.6 $ 3.2 $ 315.1 Foreign Governments 244.5 3.3 3.6 244.2 Obligations of states and political subdivisions 337.3 11.9 0.8 348.4 Corporate bonds 1,596.9 26.9 11.9 1,611.9 Commercial mortgage-backed securities 145.0 0.3 1.3 144.0 Residential mortgage-backed securities 221.6 3.4 1.7 223.3 Asset-backed securities 129.7 0.4 1.0 129.1 Collateralized loan obligations 255.9 6.1 1.8 260.2 Total fixed maturities 3,248.6 52.9 25.3 3,276.2 Equity securities 321.5 126.3 5.2 442.6 Other investments 530.0 9.5 0.1 539.4 Short-term investments 365.9 — — 365.9 Total investments $ 4,466.0 $ 188.7 $ 30.6 $ 4,624.1 December 31, 2016 (in millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Fixed maturities U.S. Governments $ 275.1 $ 0.6 $ 4.5 $ 271.2 Foreign Governments 244.2 1.1 8.0 237.3 Obligations of states and political subdivisions 375.7 8.9 1.8 382.8 Corporate bonds 1,316.9 23.3 19.5 1,320.7 Commercial mortgage-backed securities 154.9 0.4 1.6 153.7 Residential mortgage-backed securities 174.8 3.7 1.7 176.8 Asset-backed securities 127.6 0.1 2.1 125.6 Collateralized loan obligations 269.6 3.8 9.1 264.3 Total fixed maturities 2,938.8 41.9 48.3 2,932.4 Equity securities 335.2 117.9 5.7 447.4 Other investments 531.6 7.5 0.1 539.0 Short-term investments 405.5 — — 405.5 Total investments $ 4,211.1 $ 167.3 $ 54.1 $ 4,324.3
Schedule of Amortized Cost and Fair Values of Fixed Maturity Investments, by Contractual Maturity	The amortized cost and fair values of fixed maturity investments as of June 30, 2017, by contractual maturity, were as follows: (in millions) Amortized Cost Fair Value Due in one year or less $ 256.5 $ 253.4 Due after one year through five years 1,463.5 1,475.8 Due after five years through ten years 614.2 623.6 Thereafter 162.2 166.8 Structured securities 752.2 756.6 Total $ 3,248.6 $ 3,276.2
Schedule Of Carrying Value And Unfunded Investment Commitments Of Other Invested Assets Portfolio	Details regarding the carrying value and unfunded investment commitments of the other invested assets portfolio as of June 30, 2017 and December 31, 2016 were as follows: June 30, 2017 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 178.6 $ — Private equity 163.3 119.7 Long only funds 195.0 — Other investments 2.5 — Total other invested assets $ 539.4 $ 119.7 December 31, 2016 (in millions) Carrying Value Unfunded Commitments Investment Type Hedge funds $ 180.9 $ — Private equity 179.0 93.4 Long only funds 170.7 — Other investments 8.4 — Total other invested assets $ 539.0 $ 93.4
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: June 30, 2017 Less Than One Year One Year or Greater Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Fixed maturities U.S. Governments $ 267.1 $ 3.1 $ 2.7 $ 0.1 $ 269.8 $ 3.2 Foreign Governments 183.8 3.6 — — 183.8 3.6 Obligations of states and political subdivisions (1) 42.1 0.8 1.8 — 43.9 0.8 Corporate bonds 523.1 10.4 32.9 1.5 556.0 11.9 Commercial mortgage-backed securities 83.7 1.3 4.9 — 88.6 1.3 Residential mortgage-backed securities 110.9 1.6 6.2 0.1 117.1 1.7 Asset-backed securities 68.3 0.5 3.5 0.5 71.8 1.0 Collateralized loan obligations 63.1 1.7 3.0 0.1 66.1 1.8 Total fixed maturities 1,342.1 23.0 55.0 2.3 1,397.1 25.3 Equity securities 52.3 5.2 — — 52.3 5.2 Other investments 0.3 0.1 — — 0.3 0.1 Short-term investments (1) 31.6 — — — 31.6 — Total $ 1,426.3 $ 28.3 $ 55.0 $ 2.3 $ 1,481.3 $ 30.6 December 31, 2016 Less Than One Year One Year or Greater Total (in millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Fixed maturities U.S. Governments (2) $ 183.4 $ 4.5 $ — $ — $ 183.4 $ 4.5 Foreign Governments 201.2 8.0 — — 201.2 8.0 Obligations of states and political subdivisions (1) 72.6 1.7 1.8 0.1 74.4 1.8 Corporate bonds 490.5 17.7 50.6 1.8 541.1 19.5 Commercial mortgage-backed securities 70.6 1.5 7.1 0.1 77.7 1.6 Residential mortgage-backed securities (2) 87.5 1.7 4.4 — 91.9 1.7 Asset-backed securities 69.7 1.4 8.2 0.7 77.9 2.1 Collateralized loan obligations 122.5 8.6 16.9 0.5 139.4 9.1 Total fixed maturities 1,298.0 45.1 89.0 3.2 1,387.0 48.3 Equity securities 62.1 5.7 — — 62.1 5.7 Other investments 0.3 0.1 — — 0.3 0.1 Short-term investments 4.8 — — — 4.8 — Total $ 1,365.2 $ 50.9 $ 89.0 $ 3.2 $ 1,454.2 $ 54.1 (1) Unrealized losses less than one year are less than $0.1 million. (2) Unrealized losses one year or greater are less than $0.1 million.
Schedule of Recognized Other-than-temporary Losses on Fixed Maturities and Equity Portfolios	We recognized other-than-temporary losses on our fixed maturities and equity portfolio as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Other-than-temporary impairment: Corporate bonds $ — $ (0.5 ) $ — $ (1.1 ) Equity securities (1.1 ) (4.4 ) (1.5 ) (5.5 ) Other-than-temporary impairment losses $ (1.1 ) $ (4.9 ) $ (1.5 ) $ (6.6 )
Schedule of Company's Gross Realized Investment Gains (Losses)	The following table presents our gross realized investment and other gains (losses): For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Realized gains Fixed maturities $ 5.5 $ 4.6 $ 12.6 $ 11.0 Equity securities 12.0 5.3 27.7 24.6 Other investments 4.8 16.8 10.8 27.0 Short-term investments 0.3 0.2 0.5 0.4 Gross realized investment and other gains 22.6 26.9 51.6 63.0 Realized losses Fixed maturities (5.0 ) (6.5 ) (11.2 ) (14.9 ) Equity securities (1.8 ) (1.0 ) (2.5 ) (7.1 ) Other investments (10.2 ) (16.6 ) (17.2 ) (39.2 ) Short-term investments — — (0.1 ) (0.1 ) Other-than-temporary impairment losses on fixed maturities — (0.5 ) — (1.1 ) Other-than-temporary impairment losses on equity securities (1.1 ) (4.4 ) (1.5 ) (5.5 ) Gross realized investment and other losses (18.1 ) (29.0 ) (32.5 ) (67.9 ) Net realized investment and other gains (losses) before income taxes 4.5 (2.1 ) 19.1 (4.9 ) Income tax expense (1.3 ) — (5.7 ) (1.2 ) Net realized investment and other gains (losses), net of income taxes $ 3.2 $ (2.1 ) $ 13.4 $ (6.1 )
Schedule of Changes in Unrealized Appreciation (Depreciation)	Changes in unrealized appreciation (depreciation) related to investments are summarized as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Change in unrealized gains (losses) Fixed maturities $ 19.5 $ 25.9 $ 32.0 $ 64.8 Equity securities 3.3 12.9 8.7 4.0 Other investments 2.0 — 2.0 0.6 Short-term investments — — — 0.4 Net unrealized investment and other gains before income taxes 24.8 38.8 42.7 69.8 Income tax provision (5.1 ) (12.3 ) (9.7 ) (16.0 ) Net unrealized investment and other gains, net of income taxes $ 19.7 $ 26.5 $ 33.0 $ 53.8
Schedule of Fair Value of Foreign Currency Exchange Forward Contracts	The fair value of our foreign currency exchange forward contracts as of June 30, 2017 and December 31, 2016 was as follows: (in millions) June 30, 2017 December 31, 2016 Operational currency exposure $ (0.4 ) $ — Asset manager investment exposure (1.1 ) 0.7 Total return strategy (0.5 ) 3.3 $ (2.0 ) $ 4.0
Schedule of Realized Gains and Losses of Investment on Foreign Currency Exchange Forward Contracts	The following table represents our gross investment realized gains and losses on our foreign currency exchange forward contracts: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Realized gains Operational currency exposure $ 3.7 $ 4.6 $ 5.7 $ 7.4 Asset manager investment exposure — 2.3 0.5 2.3 Total return strategy 0.5 9.5 3.6 16.2 Gross realized investment gains 4.2 16.4 9.8 25.9 Realized losses Operational currency exposure (3.7 ) (7.0 ) (5.9 ) (15.5 ) Asset manager investment exposure (5.4 ) — (6.8 ) (3.6 ) Total return strategy (0.8 ) (9.4 ) (2.7 ) (18.6 ) Gross realized investment losses (9.9 ) (16.4 ) (15.4 ) (37.7 ) Net realized investment losses on foreign currency exchange forward contracts $ (5.7 ) $ — $ (5.6 ) $ (11.8 )
Schedule of Regulatory Deposits, Pledged Securities and Letters of Credit	Regulatory Deposits, Pledged Securities and Letters of Credit (in millions) June 30, 2017 December 31, 2016 Securities on deposit for regulatory and other purposes $ 176.0 $ 168.7 Securities pledged as collateral for letters of credit 29.1 35.9 Securities and cash on deposit supporting Lloyd’s business 397.2 161.8 Total restricted investments $ 602.3 $ 366.4
Financial Assets Measured at Fair Value on Recurring Basis	Based on an analysis of the inputs, our financial assets measured at fair value on a recurring basis have been categorized as follows: Fair (in millions) June 30, 2017 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities U.S. Governments $ 315.1 $ 292.7 $ 22.4 $ — Foreign Governments 244.2 — 244.2 — Obligations of states and political subdivisions 348.4 — 348.4 — Corporate bonds 1,611.9 — 1,610.0 1.9 Commercial mortgage-backed securities 144.0 — 144.0 — Residential mortgage-backed securities 223.3 — 223.3 — Asset-backed securities 129.1 — 129.1 — Collateralized loan obligations 260.2 — 260.2 — Total fixed maturities 3,276.2 292.7 2,981.6 1.9 Equity securities 442.6 440.1 2.1 0.4 Other investments 108.9 — 108.9 — Short-term investments 365.9 348.9 17.0 — $ 4,193.6 $ 1,081.7 $ 3,109.6 $ 2.3 (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, 2016 Level 1 (a) Level 2 (b) Level 3 (c) Fixed maturities U.S. Governments $ 271.2 $ 228.0 $ 43.2 $ — Foreign Governments 237.3 — 237.3 — Obligations of states and political subdivisions 382.8 — 382.8 — Corporate bonds 1,320.7 — 1,318.7 2.0 Commercial mortgage-backed securities 153.7 — 153.7 — Residential mortgage-backed securities 176.8 — 176.8 — Asset-backed securities 125.6 — 125.6 — Collateralized loan obligations 264.3 — 264.3 — Total fixed maturities 2,932.4 228.0 2,702.4 2.0 Equity securities 447.4 444.9 2.1 0.4 Other investments 95.5 — 95.5 — Short-term investments 405.5 375.1 30.4 — $ 3,880.8 $ 1,048.0 $ 2,830.4 $ 2.4 (a) Quoted prices in active markets for identical assets (b) Significant other observable inputs (c) Significant unobservable inputs
Schedule of Reconciliation of Beginning and Ending Balances for Investments Categorized as Level 3	A reconciliation of the beginning and ending balances for the investments categorized as Level 3 are as follows: Fair Value Measurements Using Observable Inputs (Level 3) (in millions) Corporate Bonds Equity Securities Total Beginning balance, January 1, 2017 $ 2.0 $ 0.4 $ 2.4 Transfers into Level 3 — — — Transfers out of Level 3 — — — Total gains or losses (realized/unrealized): Included in net income (loss) — — — Included in other comprehensive income (loss) (0.1 ) — (0.1 ) Purchases, issuances, sales, and settlements: Purchases — — — Issuances — — — Sales — — — Settlements — — — Ending balance, June 30, 2017 $ 1.9 $ 0.4 $ 2.3 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 June 30, 2017 $ — $ — $ — (in millions) Corporate Bonds Equity Securities Total Beginning balance, January 1, 2016 $ — $ 0.7 $ 0.7 Transfers into Level 3 — — — Transfers out of Level 3 — — — Total gains or losses (realized/unrealized): Included in net income (loss) — — — Included in other comprehensive income (loss) — — — Purchases, issuances, sales, and settlements: Purchases 2.0 — 2.0 Issuances — — — Sales — (0.3 ) (0.3 ) Settlements — — — Ending balance, December 31, 2016 $ 2.0 $ 0.4 $ 2.4 Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at December 31, 2016 $ — $ — $ —

Reserves for Losses and Loss 28

Reserves for Losses and Loss Adjustment Expenses (Tables)	6 Months Ended
	Jun. 30, 2017
Insurance [Abstract]
Reserves for Losses and Loss Adjustment Expenses	The following table provides a reconciliation of reserves for losses and loss adjustment expenses (“LAE”): For the Six Months Ended June 30, (in millions) 2017 2016 Net reserves beginning of the year $ 2,180.2 $ 2,133.3 Net Maybrooke reserves acquired 132.6 — Add: Losses and LAE incurred during current calendar year, net of reinsurance: Current accident year 447.4 404.1 Prior accident years 5.7 (15.9 ) Losses and LAE incurred during calendar year, net of reinsurance 453.1 388.2 Deduct: Losses and LAE payments made during current calendar year, net of reinsurance: Current accident year 88.9 65.3 Prior accident years 290.8 300.1 Losses and LAE payments made during current calendar year, net of reinsurance: 379.7 365.4 Change in participation interest (1) (23.2 ) (36.3 ) Foreign exchange adjustments 1.8 4.4 Net reserves - end of period 2,364.8 2,124.2 Add: Reinsurance recoverables on unpaid losses and LAE, end of year 1,268.0 1,057.7 Gross reserves - end of period $ 3,632.8 $ 3,181.9 (1) Amount represents decreases in reserves due to change in syndicate participation
Impact from Unfavorable (Favorable) Development of Prior Accident Years’ Loss and LAE Reserves on Each Reporting Segment	The impact from the unfavorable (favorable) development of prior accident years’ loss and LAE reserves on each reporting segment is presented below: For the Six Months Ended June 30, (in millions) 2017 2016 U.S. Operations $ (18.0 ) $ (11.9 ) International Operations 19.6 (10.2 ) Run-off Lines 4.1 6.2 Total unfavorable (favorable) prior-year development $ 5.7 $ (15.9 )

Junior Subordinated Debentures

Junior Subordinated Debentures (Tables)	6 Months Ended
	Jun. 30, 2017
Junior Subordinated Debentures [Member]
Schedule of Junior Subordinated Debentures	A summary of our outstanding junior subordinated debentures is presented below: (in millions) Issue Date Trust Preferred Pools Maturity Rate Structure Interest Rate at June 30, 2017 Amount Argo Group 05/15/2003 PXRE Capital Statutory Trust II 05/15/2033 3M LIBOR + 4.10% 5.28% $ 18.1 11/06/2003 PXRE Capital Trust VI 09/30/2033 3M LIBOR + 3.90% 5.20% 10.3 Argo Group US 05/15/2003 Argonaut Group Statutory Trust I 05/15/2033 3M LIBOR + 4.10% 5.28% 15.5 12/16/2003 Argonaut Group Statutory Trust III 01/08/2034 3M LIBOR + 4.10% 5.26% 12.3 04/29/2004 Argonaut Group Statutory Trust IV 04/29/2034 3M LIBOR + 3.85% 5.03% 13.4 05/26/2004 Argonaut Group Statutory Trust V 05/24/2034 3M LIBOR + 3.85% 5.04% 12.3 05/12/2004 Argonaut Group Statutory Trust VI 05/12/2034 3M LIBOR + 3.80% 5.07% 13.4 09/17/2004 Argonaut Group Statutory Trust VII 12/15/2034 3M LIBOR + 3.60% 4.85% 15.5 09/22/2004 Argonaut Group Statutory Trust VIII 09/22/2034 3M LIBOR + 3.55% 4.84% 15.5 10/22/2004 Argonaut Group Statutory Trust IX 12/15/2034 3M LIBOR + 3.60% 4.85% 15.5 09/15/2005 Argonaut Group Statutory Trust X 09/15/2035 3M LIBOR + 3.40% 4.65% 30.9 Total Outstanding $ 172.7 (in millions) Issue Date Trust Preferred Pools Maturity Rate Structure Interest Rate at December 31, 2016 Amount Argo Group 05/15/2003 PXRE Capital Statutory Trust II 05/15/2033 3M LIBOR + 4.10% 5.00% $ 18.1 11/06/2003 PXRE Capital Trust VI 09/30/2033 3M LIBOR + 3.90% 4.90% 10.3 Argo Group US 05/15/2003 Argonaut Group Statutory Trust I 05/15/2033 3M LIBOR + 4.10% 5.00% 15.5 12/16/2003 Argonaut Group Statutory Trust III 01/08/2034 3M LIBOR + 4.10% 4.98% 12.3 04/29/2004 Argonaut Group Statutory Trust IV 04/29/2034 3M LIBOR + 3.85% 4.76% 13.4 05/26/2004 Argonaut Group Statutory Trust V 05/24/2034 3M LIBOR + 3.85% 4.77% 12.3 05/12/2004 Argonaut Group Statutory Trust VI 05/12/2034 3M LIBOR + 3.80% 4.79% 13.4 09/17/2004 Argonaut Group Statutory Trust VII 12/15/2034 3M LIBOR + 3.60% 4.56% 15.5 09/22/2004 Argonaut Group Statutory Trust VIII 09/22/2034 3M LIBOR + 3.55% 4.55% 15.5 10/22/2004 Argonaut Group Statutory Trust IX 12/15/2034 3M LIBOR + 3.60% 4.56% 15.5 09/15/2005 Argonaut Group Statutory Trust X 09/15/2035 3M LIBOR + 3.40% 4.36% 30.9 Total Outstanding $ 172.7
Maybrooke Junior Subordinated Debentures [Member]
Schedule of Junior Subordinated Debentures	A summary of the terms of the Maybrooke debt outstanding at June 30, 2017 is presented below: (in millions) Issue Date Maturity Rate Structure Interest Rate at June 30, 2017 Principal at June 30, 2017 Carrying Value at June 30, 2017 9/15/2007 9/15/2037 3 month LIBOR + 3.15% 4.40% $ 91.8 $ 83.7

Other Indebtedness (Tables)

Other Indebtedness (Tables)	6 Months Ended
	Jun. 30, 2017
Schedule of Terms and Principal Amounts of Each Debt Instrument	Our Consolidated Balance Sheets includes various long-term debt instruments under the caption “Other indebtedness,” as detailed in the table below. Information regarding the terms and principal amounts of each of these debt instruments is also provided. (in millions) Debt Type June 30, 2017 December 31, 2016 Floating rate loan stock $ 56.9 $ 54.8 Term loan 125.0 — Other debt 0.6 0.6 Total other indebtedness $ 182.5 $ 55.4
Floating Rate Loan Stock [Member]
Schedule of Junior Subordinated Debentures	A summary of the notes outstanding at June 30, 2017 and December 31, 2016 is presented below: (in millions) Issue Date Currency Maturity Rate Structure Interest Rate at June 30, 2017 Amount 12/08/2004 U.S. Dollar 11/15/2034 6 month LIBOR + 4.2% 5.53% $ 6.5 09/06/2005 Euro 08/22/2035 3 month LIBOR + 4.0% 3.67% 13.5 10/31/2006 U.S. Dollar 01/15/2036 6 month LIBOR + 4.0% 5.33% 10.0 10/31/2006 Euro 11/22/2036 3 month LIBOR + 4.0% 3.67% 11.8 06/08/2007 Euro 09/15/2037 3 month LIBOR + 3.9% 3.57% 15.1 $ 56.9 (in millions) Issue Date Currency Maturity Rate Structure Interest Rate at December 31, 2016 Amount 12/08/2004 U.S. Dollar 11/15/2034 6 month LIBOR + 4.2% 5.18% $ 6.5 09/06/2005 Euro 08/22/2035 3 month LIBOR + 4.0% 3.70% 12.8 10/31/2006 U.S. Dollar 01/15/2036 6 month LIBOR + 4.0% 4.98% 10.0 10/31/2006 Euro 11/22/2036 3 month LIBOR + 4.0% 3.70% 11.2 06/08/2007 Euro 09/15/2037 3 month LIBOR + 3.9% 3.58% 14.3 $ 54.8
New Credit Agreement [Member]
Schedule of Floating Rate Loan Stock and Borrowing Under Credit Facility, Notes Outstanding	A summary of the terms of the outstanding balance at June 30, 2017 is presented below: (in millions) Issue Date Maturity Rate Structure Interest Rate at June 30, 2017 Amount 3/3/2017 3/3/2019 2 month LIBOR + 1.5% 2.54% $ 125.0

Disclosures about Fair Value 31

Disclosures about Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Summary of Company's Financial Instruments Whose Carrying Amount Did Not Equal Fair Value	A summary of our financial instruments whose carrying value did not equal fair value is shown below: June 30, 2017 December 31, 2016 (in millions) Carrying Amount Fair Value Carrying Amount Fair Value Junior subordinated debentures Trust preferred debentures $ 172.7 $ 167.5 $ 172.7 $ 162.4 Maybrooke subordinated debenture 83.7 85.2 — — Senior unsecured fixed rate notes 139.5 139.3 139.5 139.3 Floating rate loan stock 56.9 55.1 54.8 51.5

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Schedule of Repurchase of Shares	A summary of common shares repurchased for the six months ended June 30, 2016 is shown below: Repurchase Type Date Trading Plan Initiated 2017 Purchase Period Number of Shares Repurchased Average Price of Shares Repurchased Total Cost (in millions) Repurchase Authorization Year 10b5-1 Trading Plan 6/14/2017 06/20/2017-06/28/2017 46,500 $ 59.54 $ 2.8 2016

Accumulated Other Comprehensi33

Accumulated Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 30, 2017
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 six months ended June 30, 2017, and 2016 is presented below: (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance at January 1, 2017 $ (17.6 ) $ 72.4 $ (7.1 ) $ 47.7 Other comprehensive income (loss) before reclassifications (0.6 ) 45.7 — 45.1 Amounts reclassified from accumulated other comprehensive income (loss) — (12.7 ) — (12.7 ) Net current-period other comprehensive income (loss) (0.6 ) 33.0 — 32.4 Balance at June 30, 2017 $ (18.2 ) $ 105.4 $ (7.1 ) $ 80.1 (in millions) Foreign Currency Translation Adjustments Unrealized Holding Gains on Securities Defined Benefit Pension Plans Total Balance at January 1, 2016 $ (21.6 ) $ 40.0 $ (6.9 ) $ 11.5 Other comprehensive income (loss) before reclassifications 3.8 58.0 — 61.8 Amounts reclassified from accumulated other comprehensive income (loss) — (4.2 ) — (4.2 ) Net current-period other comprehensive income (loss) 3.8 53.8 — 57.6 Balance at June 30, 2016 $ (17.8 ) $ 93.8 $ (6.9 ) $ 69.1
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	The following table illustrates the amounts reclassified from accumulated other comprehensive income (loss) shown in the above tables that have been included in our Consolidated Statements of Income: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Unrealized gains on securities: Net realized investment gains $ (2.7 ) $ (0.3 ) $ (18.9 ) $ (8.1 ) Provision for income taxes (benefit) 1.0 (0.2 ) 6.2 3.9 Net of taxes $ (1.7 ) $ (0.5 ) $ (12.7 ) $ (4.2 )

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Net Income Per Common Share on Basic and Diluted Basis	The following table presents the calculation of net income per common share on a basic and diluted basis: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions, except number of shares and per share amounts) 2017 2016 2017 2016 Net income $ 46.0 $ 30.9 $ 82.7 $ 58.6 Weighted average common shares outstanding - basic 30,201,457 30,187,592 30,124,696 30,333,417 Effect of dilutive securities: Equity compensation awards 846,624 622,564 870,476 637,772 Weighted average common shares outstanding - diluted 31,048,081 30,810,156 30,995,172 30,971,189 Net income per common share: Basic $ 1.52 $ 1.03 $ 2.75 $ 1.93 Diluted $ 1.48 $ 1.00 $ 2.67 $ 1.89

Supplemental Cash Flow Inform35

Supplemental Cash Flow Information (Tables)	6 Months Ended
	Jun. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Schedule of Interest Paid	Interest paid was as follows: For the Six Months Ended June 30, (in millions) 2017 2016 Senior unsecured fixed rate notes $ 4.7 $ 4.7 Junior subordinated debentures 6.0 3.8 Other indebtedness 1.6 1.2 Revolving credit facility 0.3 — Total interest paid $ 12.6 $ 9.7

Share-based Compensation (Table

Share-based Compensation (Tables)	6 Months Ended
	Jun. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Fair Value Assumptions	The following table summarizes the assumptions we used for the six months ended June 30, 2017, and 2016 : For the Six Months Ended June 30, 2017 2016 Risk-free rate of return 1.83 % 1.00 % Expected dividend yields 1.68 % 1.70 % Expected award life (years) 4.48 4.54 Expected volatility 18.64 % 19.70 %
Summary of Restricted Share Activity	A summary of restricted share activity as of June 30, 2017 and changes during the six months then ended is as follows: Shares Weighted-Average Grant Date Fair Value Outstanding at January 1, 2017 702,030 $ 42.69 Granted 204,467 $ 62.68 Vested and issued (146,878 ) $ 41.47 Expired or forfeited (22,969 ) $ 49.62 Outstanding at June 30, 2017 736,650 $ 48.26
Summary of Stock-Settled SARs Activity	A summary of stock-settled SARs activity as of June 30, 2017 and changes during the six months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2017 1,982,695 $ 34.80 Exercised (315,835 ) $ 32.61 Expired or forfeited (58,721 ) $ 40.44 Outstanding at June 30, 2017 1,608,139 $ 35.02
Summary of Cash-Settled SARs Activity	A summary of cash-settled SARs activity as of June 30, 2017 and changes during the six months then ended is as follows: Shares Weighted-Average Exercise Price Outstanding at January 1, 2017 500,486 $ 32.08 Exercised (185,359 ) $ 32.90 Expired or forfeited (14,503 ) $ 23.69 Outstanding at June 30, 2017 300,624 $ 31.98

Underwriting, Acquisition and37

Underwriting, Acquisition and Insurance Expenses (Tables)	6 Months Ended
	Jun. 30, 2017
Underwriting Acquisition And Insurance Expenses [Abstract]
Underwriting, Acquisition and Insurance Expenses	Underwriting, acquisition and insurance expenses were as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Commissions $ 69.2 $ 62.1 $ 130.4 $ 119.2 General expenses 88.0 71.1 176.7 141.7 Premium taxes, boards and bureaus 6.7 6.3 14.1 12.9 163.9 139.5 321.2 273.8 Net deferral of policy acquisition costs (9.2 ) (6.5 ) (12.9 ) (8.2 ) Total underwriting, acquisition and insurance expenses $ 154.7 $ 133.0 $ 308.3 $ 265.6

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Tax Provision (Benefit)	Our income tax provision includes the following components: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Current tax provision $ 15.5 $ 6.5 $ 15.5 $ 8.0 Deferred tax provision related to: Future tax deductions (9.7 ) 2.0 (3.6 ) 4.9 Valuation allowance change (1.0 ) 0.2 (1.1 ) 1.2 Income tax provision $ 4.8 $ 8.7 $ 10.8 $ 14.1
Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates	For the three and six months ended June 30, 2017 and 2016, pre-tax income (loss) attributable to our operations and the operations’ effective tax rates were as follows: For the Three Months Ended June 30, (in millions) 2017 2016 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 25.3 0.0 % $ 22.1 0.0 % United States 34.7 23.3 % 26.5 30.9 % United Kingdom (6.5 ) 52.8 % (9.8 ) -5.7 % Belgium 0.1 36.6 % — (1) 16.3 % Brazil 0.6 0.0 % 0.8 0.0 % United Arab Emirates (2.2 ) 0.0 % — (1) 0.0 % Ireland — (1) 0.0 % (0.1 ) 0.0 % Malta 0.5 0.0 % 0.1 0.0 % Luxembourg (1.7 ) 0.0 % — 0.0 % Switzerland — (1) 22.1 % — (1) 22.8 % Total $ 50.8 9.4 % $ 39.6 22.1 % For the Six Months Ended June 30, (in millions) 2017 2016 Pre-Tax Income (Loss) Effective Tax Rate Pre-Tax Income (Loss) Effective Tax Rate Bermuda $ 51.7 0.0 % $ 44.1 0.0 % United States 58.7 24.8 % 49.8 27.5 % United Kingdom (12.0 ) 32.3 % (22.1 ) -1.7 % Belgium 0.1 36.2 % — (1) 32.0 % Brazil (0.2 ) 0.0 % 0.7 0.0 % United Arab Emirates (3.5 ) 0.0 % — (1) 0.0 % Ireland — (1) 0.0 % (0.1 ) 0.0 % Malta 1.1 0.0 % 0.3 0.0 % Luxembourg (2.4 ) 0.0 % — 0.0 % Switzerland — (1) 20.8 % — (1) 21.1 % Total $ 93.5 11.5 % $ 72.7 19.4 % (1) Pre-tax income for the respective year was less than $0.1 million.
Reconciliation of Difference Between Provision for Income Taxes and Expected Tax Provision at Weighted Average Tax Rate	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. A reconciliation of the difference between the provision for income taxes and the expected tax provision at the weighted average tax rate is as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Income tax provision at expected rate $ 10.8 $ 7.6 $ 18.0 $ 13.4 Tax effect of: Tax-exempt interest (0.7 ) (0.9 ) (1.5 ) (1.8 ) Dividends received deduction (0.4 ) (0.8 ) (0.9 ) (1.3 ) Valuation allowance change (1.0 ) 0.2 (1.1 ) 1.2 Other permanent adjustments, net (1.1 ) — (1.0 ) 0.2 Adjustment for prior period — — (0.7 ) — Adjustment for annualized rate (1.8 ) 0.9 (2.5 ) (0.6 ) Other foreign adjustments (0.4 ) (0.6 ) 0.4 (0.6 ) Deferred tax rate reduction — — — (0.3 ) State income tax 0.1 — 0.1 — Foreign exchange adjustments (0.9 ) 2.1 (0.3 ) 3.6 Foreign withholding taxes 0.2 0.2 0.3 0.3 Income tax provision $ 4.8 $ 8.7 $ 10.8 $ 14.1 Income tax provision - Foreign $ (3.3 ) $ 0.6 $ (3.8 ) $ 0.4 Income tax provision - United States, Federal 7.8 7.9 $ 14.2 13.5 Income tax provision - United States, State 0.1 — 0.1 — Foreign withholding tax - United States 0.2 0.2 0.3 0.2 Income tax provision $ 4.8 $ 8.7 $ 10.8 $ 14.1

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Revenue and Income (Loss) Before Income Taxes for Each Segment	Revenue and income (loss) before income taxes for each segment were as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Revenue: Earned premiums U.S. Operations $ 229.1 $ 206.8 $ 450.3 $ 413.4 International Operations 169.9 137.9 328.1 276.2 Run-off Lines 0.1 0.2 0.1 0.2 Total earned premiums 399.1 344.9 778.5 689.8 Net investment income U.S. Operations 27.3 21.7 47.2 35.5 International Operations 10.1 9.1 16.7 15.2 Run-off Lines 2.9 3.4 5.0 5.6 Corporate and Other 3.3 1.5 5.2 0.6 Total net investment income 43.6 35.7 74.1 56.9 Fee and other income 3.8 5.8 7.4 12.6 Net realized investment and other gains (losses) 4.5 (2.1 ) 19.1 (4.9 ) Total revenue $ 451.0 $ 384.3 $ 879.1 $ 754.4 For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Income (loss) before income taxes U.S. Operations $ 53.0 $ 45.4 $ 90.2 $ 80.3 International Operations 9.1 15.3 17.4 33.0 Run-off Lines (1.2 ) (3.2 ) (3.7 ) (4.6 ) Total segment income before taxes 60.9 57.5 103.9 108.7 Corporate and Other (14.6 ) (15.8 ) (29.5 ) (31.1 ) Net realized investment and other gains (losses) 4.5 (2.1 ) 19.1 (4.9 ) Total income before income taxes $ 50.8 $ 39.6 $ 93.5 $ 72.7
Schedule of Earned Premiums by Geographic Location	The table below presents earned premiums by geographic location for the three and six months ended June 30, 2017 and 2016. For this disclosure, we determine geographic location by the country of domicile of our subsidiaries that underwrite the business and not by the location of insureds or reinsureds from whom the business was generated. For the Three Months Ended June 30, For the Six Months Ended June 30, (in millions) 2017 2016 2017 2016 Bermuda $ 23.1 $ 29.0 $ 48.7 $ 57.1 Brazil 12.3 10.0 25.1 19.2 Malta 1.3 0.5 2.3 1.0 United Kingdom 133.3 98.1 252.1 198.7 United States 229.1 207.3 450.3 413.8 Total earned premiums $ 399.1 $ 344.9 $ 778.5 $ 689.8
Identifiable Assets	The following table represents identifiable assets: (in millions) June 30, 2017 December 31, 2016 U.S. Operations $ 4,127.7 $ 3,961.2 International Operations 3,223.6 2,356.9 Run-off Lines 414.6 537.0 Corporate and Other 474.8 349.9 Total $ 8,240.7 $ 7,205.0

Senior Unsecured Fixed Rate N40

Senior Unsecured Fixed Rate Notes (Tables)	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Schedule Of Unamortized Debt Issuance Costs Deducted From Carrying Value Of Debt Liability	At June 30, 2017 and December 31, 2016, the Notes consisted of the following: (in millions) June 30, 2017 December 31, 2016 Senior unsecured fixed rate notes Principal $ 143.8 $ 143.8 Less: unamortized debt issuance costs (4.3 ) (4.3 ) Senior unsecured fixed rate notes, less unamortized debt issuance costs $ 139.5 $ 139.5
Condensed Consolidating Balance Sheet	CONDENSED CONSOLIDATING BALANCE SHEET June 30, 2017 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Assets Investments $ 1.2 $ 2,893.8 $ 1,729.1 $ — $ 4,624.1 Cash — 46.2 168.3 — 214.5 Accrued investment income — 17.2 5.8 — 23.0 Premiums receivable — 214.0 458.6 — 672.6 Reinsurance recoverables — 1,386.5 133.1 — 1,519.6 Goodwill and other intangible assets, net 43.5 126.1 91.5 — 261.1 Deferred acquisition costs, net — 74.2 88.6 — 162.8 Ceded unearned premiums — 182.0 254.6 — 436.6 Other assets 8.8 171.4 146.2 — 326.4 Intercompany note receivable — 49.6 70.4 (120.0 ) — Investments in subsidiaries 2,156.4 — — (2,156.4 ) — Total assets $ 2,209.9 $ 5,161.0 $ 3,146.2 $ (2,276.4 ) $ 8,240.7 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — $ 2,354.7 $ 1,278.1 $ — $ 3,632.8 Unearned premiums — 618.4 557.8 — 1,176.2 Funds held and ceded reinsurance payable, net — 736.3 8.6 — 744.9 Long-term debt 153.4 284.4 140.6 — 578.4 Current income taxes payable, net — 11.5 1.9 — 13.4 Deferred tax liabilities, net — 29.8 8.4 — 38.2 Accrued underwriting expenses and other liabilities 11.0 80.5 74.0 — 165.5 Due to affiliates 34.2 5.1 (5.1 ) (34.2 ) — Intercompany note payable 120.0 — — (120.0 ) — Total liabilities 318.6 4,120.7 2,064.3 (154.2 ) 6,349.4 Total shareholders' equity 1,891.3 1,040.3 1,081.9 (2,122.2 ) 1,891.3 Total liabilities and shareholders' equity $ 2,209.9 $ 5,161.0 $ 3,146.2 $ (2,276.4 ) $ 8,240.7 (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 BALANCE SHEET December 31, 2016 (in millions) Argo Group International Holdings, Ltd (Parent Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Assets Investments $ 2.2 $ 2,834.2 $ 1,487.9 $ — $ 4,324.3 Cash — 53.7 32.3 — 86.0 Accrued investment income — 16.0 4.7 — 20.7 Premiums receivable — 204.9 258.9 — 463.8 Reinsurance recoverables — 1,348.4 37.2 — 1,385.6 Goodwill and other intangible assets, net — 127.1 92.8 — 219.9 Deferred acquisition costs, net — 63.5 75.6 — 139.1 Ceded unearned premiums — 168.9 133.9 — 302.8 Other assets 8.7 168.0 86.1 — 262.8 Intercompany note receivable — 50.2 (50.2 ) — — Investments in subsidiaries 1,834.4 — — (1,834.4 ) — Total assets $ 1,845.3 $ 5,034.9 $ 2,159.2 $ (1,834.4 ) $ 7,205.0 Liabilities and Shareholders' Equity Reserves for losses and loss adjustment expenses $ — $ 2,322.4 $ 1,028.4 $ — $ 3,350.8 Unearned premiums — 580.0 390.0 — 970.0 Funds held and ceded reinsurance payable, net — 750.2 (206.5 ) — 543.7 Long-term debt 28.4 284.4 54.8 — 367.6 Current income taxes payable, net — 8.5 (0.4 ) — 8.1 Deferred tax liabilities, net — 17.6 6.5 — 24.1 Accrued underwriting expenses and other liabilities 13.7 92.0 42.3 — 148.0 Due to affiliates 10.5 1.8 (1.8 ) (10.5 ) — Total liabilities 52.6 4,056.9 1,313.3 (10.5 ) 5,412.3 Total shareholders' equity 1,792.7 978.0 845.9 (1,823.9 ) 1,792.7 Total liabilities and shareholders' equity $ 1,845.3 $ 5,034.9 $ 2,159.2 $ (1,834.4 ) $ 7,205.0 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations.
Condensed Consolidating Statement of Income	CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE THREE MONTHS ENDED JUNE 30, 2017 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 135.5 $ 263.6 $ — $ 399.1 Net investment (expense) income (0.4 ) 29.3 14.7 — 43.6 Fee and other income — 2.9 0.9 — 3.8 Net realized investment and other gains (losses) — 5.2 (0.7 ) — 4.5 Total revenue (0.4 ) 172.9 278.5 — 451.0 Expenses: Losses and loss adjustment expenses — 72.5 158.1 — 230.6 Underwriting, acquisition and insurance expenses 3.8 58.5 92.4 — 154.7 Interest expense 1.1 4.2 1.7 — 7.0 Fee and other expense — 3.2 0.1 — 3.3 Foreign currency exchange (gains) loss — (0.1 ) 4.7 — 4.6 Total expenses 4.9 138.3 257.0 — 400.2 (Loss) Income before income taxes (5.3 ) 34.6 21.5 — 50.8 Provision for income taxes — 8.1 (3.3 ) — 4.8 Net (loss) income before equity in earnings of subsidiaries (5.3 ) 26.5 24.8 — 46.0 Equity in undistributed earnings of subsidiaries 51.3 — — (51.3 ) — Net income $ 46.0 $ 26.5 $ 24.8 $ (51.3 ) $ 46.0 CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE THREE MONTHS ENDED JUNE 30, 2016 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 120.2 $ 224.7 $ — $ 344.9 Net investment (expense) income (0.5 ) 27.5 8.7 — 35.7 Fee and other income — 4.2 1.6 — 5.8 Net realized investment and other gains (losses) 0.2 1.9 (4.2 ) — (2.1 ) Total revenue (0.3 ) 153.8 230.8 — 384.3 Expenses: Losses and loss adjustment expenses — 69.1 127.5 — 196.6 Underwriting, acquisition and insurance expenses 1.1 49.0 82.9 — 133.0 Interest expense 0.4 3.9 0.6 — 4.9 Fee and other expense — 5.0 0.7 — 5.7 Foreign currency exchange (gains) loss — (0.1 ) 4.6 — 4.5 Total expenses 1.5 126.9 216.3 — 344.7 (Loss) Income before income taxes (1.8 ) 26.9 14.5 — 39.6 Provision for income taxes — 8.3 0.4 — 8.7 Net (loss) income before equity in earnings of subsidiaries (1.8 ) 18.6 14.1 — 30.9 Equity in undistributed earnings of subsidiaries 32.7 — — (32.7 ) — Net income $ 30.9 $ 18.6 $ 14.1 $ (32.7 ) $ 30.9 CONDENSED CONSOLIDATING STATEMENT OF INCOME FOR THE SIX MONTHS ENDED JUNE 30, 2017 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 266.4 $ 512.1 $ — $ 778.5 Net investment (expense) income (2.1 ) 48.2 28.0 — 74.1 Fee and other income — 5.7 1.7 — 7.4 Net realized investment and other gains (losses) 0.5 19.0 (0.4 ) — 19.1 Total revenue (1.6 ) 339.3 541.4 — 879.1 Expenses: Losses and loss adjustment expenses — 148.6 304.5 — 453.1 Underwriting, acquisition and insurance expenses 12.2 116.7 179.4 — 308.3 Interest expense 1.4 8.5 3.0 — 12.9 Fee and other expense — 6.6 0.8 — 7.4 Foreign currency exchange loss — — 3.9 — 3.9 Total expenses 13.6 280.4 491.6 — 785.6 (Loss) Income before income taxes (15.2 ) 58.9 49.8 — 93.5 Provision for income taxes — 14.5 (3.7 ) — 10.8 Net (loss) income before equity in earnings of subsidiaries (15.2 ) 44.4 53.5 — 82.7 Equity in undistributed earnings of subsidiaries 97.9 — — (97.9 ) — Net income $ 82.7 $ 44.4 $ 53.5 $ (97.9 ) $ 82.7 (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 SIX MONTHS ENDED JUNE 30, 2016 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Premiums and other revenue: Earned premiums $ — $ 240.1 $ 449.7 $ — $ 689.8 Net investment (expense) income (1.1 ) 40.1 17.9 — 56.9 Fee and other income — 9.4 3.2 — 12.6 Net realized investment and other gains (losses) 0.2 13.1 (18.2 ) — (4.9 ) Total revenue (0.9 ) 302.7 452.6 — 754.4 Expenses: Losses and loss adjustment expenses — 137.4 250.8 — 388.2 Underwriting, acquisition and insurance expenses 6.3 96.6 162.7 — 265.6 Interest expense 0.7 7.8 1.2 — 9.7 Fee and other expense — 11.2 1.0 — 12.2 Foreign currency exchange (gains) loss — (0.1 ) 6.1 — 6.0 Total expenses 7.0 252.9 421.8 — 681.7 (Loss) Income before income taxes (7.9 ) 49.8 30.8 — 72.7 Provision for income taxes — 13.7 0.4 — 14.1 Net (loss) income before equity in earnings of subsidiaries (7.9 ) 36.1 30.4 — 58.6 Equity in undistributed earnings of subsidiaries 66.5 — — (66.5 ) — Net income $ 58.6 $ 36.1 $ 30.4 $ (66.5 ) $ 58.6 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations.
Condensed Consolidating Statement of Cash Flows	CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE SIX MONTHS ENDED JUNE 30, 2017 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Net cash flows from (used in) operating activities $ 5.3 $ (8.0 ) $ 40.0 $ — $ 37.3 Cash flows from investing activities: Proceeds from sales of investments — 514.4 444.0 — 958.4 Maturities and mandatory calls of fixed maturity investments — 240.6 94.5 — 335.1 Purchases of investments — (811.0 ) (655.0 ) — (1,466.0 ) Change in short-term investments and foreign regulatory deposits 0.4 72.0 228.0 — 300.4 Settlements of foreign currency exchange forward contracts 0.8 — (0.3 ) — 0.5 Acquisition of subsidiaries, net of cash (235.3 ) — 130.1 — (105.2 ) Issuance of intercompany note, net — — (120.0 ) 120.0 — Purchases of fixed assets and other, net (0.1 ) (12.7 ) (24.9 ) — (37.7 ) Cash (used in) provided by investing activities (234.2 ) 3.3 96.4 120.0 (14.5 ) Cash flows from financing activities: Additional long-term borrowings 125.0 — — — 125.0 Borrowing under intercompany note, net 120.0 — — (120.0 ) — Activity under stock incentive plans 0.5 — — — 0.5 Repurchase of Company's common shares — (2.8 ) — — (2.8 ) Payment of cash dividend to common shareholders (16.6 ) — — — (16.6 ) Cash provided by (used in) financing activities 228.9 (2.8 ) — (120.0 ) 106.1 Effect of exchange rate changes on cash — — (0.4 ) — (0.4 ) Change in cash — (7.5 ) 136.0 — 128.5 Cash, beginning of year — 53.7 32.3 — 86.0 Cash, end of period $ — $ 46.2 $ 168.3 $ — $ 214.5 (1) Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations. (2) Includes all Argo Group parent company eliminations. CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS FOR THE SIX MONTHS ENDED JUNE 30, 2016 (in millions) (Unaudited) Argo Group International Holdings, Ltd (Parent Guarantor) Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) Other Subsidiaries and Eliminations (1) Consolidating Adjustments (2) Total Net cash flows from (used in) operating activities $ 14.7 $ (9.2 ) $ 26.1 $ — $ 31.6 Cash flows from investing activities: Proceeds from sales of investments — 490.0 140.5 — 630.5 Maturities and mandatory calls of fixed maturity investments — 296.9 376.4 — 673.3 Purchases of investments — (720.1 ) (535.6 ) — (1,255.7 ) Change in short-term investments and foreign regulatory deposits (1.8 ) (12.3 ) 3.1 — (11.0 ) Settlements of foreign currency exchange forward contracts — — 6.8 — 6.8 Purchases of fixed assets and other, net — (11.2 ) (12.4 ) — (23.6 ) Cash (used in) provided by investing activities (1.8 ) 43.3 (21.2 ) — 20.3 Cash flows from financing activities: Activity under stock incentive plans 0.2 — — — 0.2 Repurchase of Company's common shares — (40.0 ) — — (40.0 ) Payment of cash dividend to common shareholders (13.1 ) — — — (13.1 ) Cash used in financing activities (12.9 ) (40.0 ) — — (52.9 ) Effect of exchange rate changes on cash — — (0.1 ) — (0.1 ) Change in cash — (5.9 ) 4.8 — (1.1 ) Cash, beginning of year — 88.8 32.9 — 121.7 Cash, end of period $ — $ 82.9 $ 37.7 $ — $ 120.6 (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 - Additio

Basis of Presentation - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2017
Maybrooke [Member]
Basis Of Presentation [Line Items]
Effective date of acquisition	Feb. 6, 2017

Acquisition of Maybrooke - Addi

Acquisition of Maybrooke - Additional Information (Detail) - USD ($)	Feb. 06, 2017	Jan. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Business Acquisition [Line Items]
Underwriting, acquisition and insurance expenses			$ 154,700,000		$ 133,000,000	$ 308,300,000	$ 265,600,000
Interest expense			7,000,000		$ 4,900,000	12,900,000	9,700,000
Favorable development from prior accident years						$ 5,700,000	$ (15,900,000)
Maybrooke [Member]
Business Acquisition [Line Items]
Business acquisition effective date						Feb. 6, 2017
Initial purchase price paid	$ 235,300,000
Initial purchase price subject to post closing adjustments, due date	90 days
Intangible assets	$ 43,500,000		43,500,000			$ 43,500,000
Amortization of Intangible Assets						0
Transaction cost from acquisition			2,500,000	$ 2,500,000		2,500,000
Underwriting, acquisition and insurance expenses				2,200,000
Additional transaction costs			$ 0
Favorable development from prior accident years						$ 6,500,000
Maybrooke [Member] | One Specific Claim [Member]
Business Acquisition [Line Items]
Favorable development from prior accident years		$ 6,200,000
Maybrooke [Member] | Credit Facility [Member]
Business Acquisition [Line Items]
Interest expense				$ 300,000

Acquisition of Maybrooke - Sche

Acquisition of Maybrooke - Schedule of Preliminarily Allocation of Purchase Price to Acquired Assets, Liabilities, and Intangible Assets (Detail) - Maybrooke [Member] - USD ($) $ in Millions	Feb. 06, 2017	Jun. 30, 2017
Assets:
Investments	$ 340.7
Cash	130.1
Accrued investment income	0.2
Premiums receivable	157.6
Reinsurance recoverables	80.2
Current income taxes receivable	0.6
Deferred acquisition costs, net	9.8
Ceded unearned premiums	92.6
Other assets	24
Total assets	835.8
Liabilities:
Reserves for losses and loss adjustment expenses	197
Unearned premiums	152.5
Accrued underwriting expenses	24.9
Ceded reinsurance payable, net	144.2
Junior subordinated debentures	83.6
Deferred tax liabilities	8.1
Other liabilities	33.7
Total liabilities	644
Net assets acquired	191.8
Initial purchase price	235.3
Intangible assets	$ 43.5	$ 43.5

Acquisition of Maybrooke - Summ

Acquisition of Maybrooke - Summary of Selected Financial Information (Detail) - Maybrooke [Member] - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Business Acquisition [Line Items]
Revenues	$ 42.9	$ 66.2
Net income	$ 6.4	$ 13

Acquisition of Maybrooke - Su45

Acquisition of Maybrooke - Summary of Pro Forma Results (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Business Combinations [Abstract]
Pro forma revenues	$ 449.5	$ 435.3	$ 893.2	$ 874.5
Pro forma net income	$ 46.2	$ 33.3	$ 93.2	$ 76.7
Pro forma net income per share - basic	$ 1.53	$ 1.10	$ 3.09	$ 2.53
Pro forma net income per share - diluted	$ 1.49	$ 1.08	$ 3.01	$ 2.48

Investments - Schedule of Amort

Investments - Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value of Investments (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Schedule of Invested Assets [Line Items]
Amortized Cost	$ 3,248.6	$ 2,938.8	[1]
Fair Value	3,276.2	2,932.4	[1]
Amortized Cost	321.5	335.2	[1]
Fair Value	442.6	447.4	[1]
Invested Assets Amortized Cost	4,466	4,211.1
Investments Gross Unrealized Gains	188.7	167.3
Investments Gross Unrealized losses	30.6	54.1
Total investments	4,624.1	4,324.3	[1]
Fixed Maturities [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	3,248.6	2,938.8
Gross Unrealized Gains	52.9	41.9
Gross Unrealized Losses	25.3	48.3
Fair Value	3,276.2	2,932.4
Fixed Maturities [Member] | Collateralized Loan Obligations [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	255.9	269.6
Gross Unrealized Gains	6.1	3.8
Gross Unrealized Losses	1.8	9.1
Fair Value	260.2	264.3
Fixed Maturities [Member] | Residential Mortgage-backed Securities [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	221.6	174.8
Gross Unrealized Gains	3.4	3.7
Gross Unrealized Losses	1.7	1.7
Fair Value	223.3	176.8
Fixed Maturities [Member] | U.S. Governments [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	317.7	275.1
Gross Unrealized Gains	0.6	0.6
Gross Unrealized Losses	3.2	4.5
Fair Value	315.1	271.2
Fixed Maturities [Member] | Foreign Governments [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	244.5	244.2
Gross Unrealized Gains	3.3	1.1
Gross Unrealized Losses	3.6	8
Fair Value	244.2	237.3
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	337.3	375.7
Gross Unrealized Gains	11.9	8.9
Gross Unrealized Losses	0.8	1.8
Fair Value	348.4	382.8
Fixed Maturities [Member] | Corporate Bonds [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	1,596.9	1,316.9
Gross Unrealized Gains	26.9	23.3
Gross Unrealized Losses	11.9	19.5
Fair Value	1,611.9	1,320.7
Fixed Maturities [Member] | Commercial Mortgage-backed Securities [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	145	154.9
Gross Unrealized Gains	0.3	0.4
Gross Unrealized Losses	1.3	1.6
Fair Value	144	153.7
Fixed Maturities [Member] | Asset-backed Securities [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	129.7	127.6
Gross Unrealized Gains	0.4	0.1
Gross Unrealized Losses	1	2.1
Fair Value	129.1	125.6
Equity Securities [Member]
Schedule of Invested Assets [Line Items]
Amortized Cost	321.5	335.2
Gross Unrealized Gains	126.3	117.9
Gross Unrealized Losses	5.2	5.7
Fair Value	442.6	447.4
Other Investments [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost	530	531.6
Investments Gross Unrealized Gains	9.5	7.5
Investments Gross Unrealized losses	0.1	0.1
Total investments	539.4	539
Short-Term Investments [Member]
Schedule of Invested Assets [Line Items]
Invested Assets Amortized Cost	365.9	405.5
Investments Gross Unrealized Gains	0	0
Investments Gross Unrealized losses	0	0
Total investments	$ 365.9	$ 405.5
[1]	Derived from audited consolidated financial statements.

Investments - Additional Inform

Investments - Additional Information (Detail)	Jun. 30, 2017USD ($)Security	Dec. 31, 2016USD ($)
Schedule Of Investments [Line Items]
Fair value of investments, assets managed on behalf of the trade capital providers	$ 155,700,000	$ 131,900,000
Number of securities in an unrealized loss position, total | Security	7,939
Number of securities in an unrealized loss position for less than one year | Security	2,043
Number of securities in an unrealized loss position for a period of one year or greater | Security	123
Transfers between Level 1 and Level 2 securities	$ 0
Transfers between Level 2 and Level 1 securities	0
Fixed Maturities Term Loan [Member]
Schedule Of Investments [Line Items]
Own term loan fixed maturity levels (Available-for-sale) 3 value	$ 1,900,000

Investments - Schedule of Amo48

Investments - Schedule of Amortized Cost and Fair Values of Fixed Maturity Investments, by Contractual Maturity (Detail) $ in Millions	Jun. 30, 2017USD ($)
Investments Debt And Equity Securities [Abstract]
Amortized Cost, Due in one year or less	$ 256.5
Amortized Cost, Due after one year through five years	1,463.5
Amortized Cost, Due after five years through ten years	614.2
Amortized Cost, Thereafter	162.2
Amortized Cost, Structured securities	752.2
Amortized Cost, Total	3,248.6
Fair Value, Due in one year or less	253.4
Fair Value, Due after one year through five years	1,475.8
Fair Value, Due after five years through ten years	623.6
Fair Value, Thereafter	166.8
Fair Value, Structured securities	756.6
Fair Value, Total	$ 3,276.2

Investments - Schedule of Carry

Investments - Schedule of Carrying Value and Unfunded Investment Commitments of Other Invested Assets Portfolio (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Schedule Of Investments [Line Items]
Carrying Value	$ 4,624.1	$ 4,324.3	[1]
Hedge funds [Member]
Schedule Of Investments [Line Items]
Carrying Value	178.6	180.9
Unfunded Commitments	0	0
Private equity [Member]
Schedule Of Investments [Line Items]
Carrying Value	163.3	179
Unfunded Commitments	119.7	93.4
Long only funds [Member]
Schedule Of Investments [Line Items]
Carrying Value	195	170.7
Unfunded Commitments	0	0
Other Investments [Member]
Schedule Of Investments [Line Items]
Carrying Value	2.5	8.4
Unfunded Commitments	0	0
Other Invested Assets [Member]
Schedule Of Investments [Line Items]
Carrying Value	539.4	539
Unfunded Commitments	$ 119.7	$ 93.4
[1]	Derived from audited consolidated financial statements.

Investments - Schedule of Aging

Investments - Schedule of Aging of Unrealized Losses on Company's Investments in Fixed Maturities, Equity Securities and Other Investments (Detail) - USD ($) $ in Millions		Jun. 30, 2017		Dec. 31, 2016
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		$ 1,426.3		$ 1,365.2
Unrealized Losses, Less Than One Year		28.3		50.9
Fair Value, One Year or Greater		55		89
Unrealized Losses, One Year or Greater		2.3		3.2
Fair Value, Total		1,481.3		1,454.2
Unrealized Losses, Total		30.6		54.1
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		1,342.1		1,298
Unrealized Losses, Less Than One Year		23		45.1
Fair Value, One Year or Greater		55		89
Unrealized Losses, One Year or Greater		2.3		3.2
Fair Value, Total		1,397.1		1,387
Unrealized Losses, Total		25.3		48.3
Fixed Maturities [Member] | Collateralized Loan Obligations [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		63.1		122.5
Unrealized Losses, Less Than One Year		1.7		8.6
Fair Value, One Year or Greater		3		16.9
Unrealized Losses, One Year or Greater		0.1		0.5
Fair Value, Total		66.1		139.4
Unrealized Losses, Total		1.8		9.1
Fixed Maturities [Member] | Residential Mortgage-backed Securities [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		110.9		87.5	[1]
Unrealized Losses, Less Than One Year		1.6		1.7	[1]
Fair Value, One Year or Greater		6.2		4.4	[1]
Unrealized Losses, One Year or Greater		0.1		0	[1]
Fair Value, Total		117.1		91.9	[1]
Unrealized Losses, Total		1.7		1.7	[1]
Fixed Maturities [Member] | U.S. Governments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		267.1		183.4	[1]
Unrealized Losses, Less Than One Year		3.1		4.5	[1]
Fair Value, One Year or Greater		2.7		0	[1]
Unrealized Losses, One Year or Greater		0.1		0	[1]
Fair Value, Total		269.8		183.4	[1]
Unrealized Losses, Total		3.2		4.5	[1]
Fixed Maturities [Member] | Foreign Governments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		183.8		201.2
Unrealized Losses, Less Than One Year		3.6		8
Fair Value, One Year or Greater		0		0
Unrealized Losses, One Year or Greater		0		0
Fair Value, Total		183.8		201.2
Unrealized Losses, Total		3.6		8
Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year	[2]	42.1		72.6
Unrealized Losses, Less Than One Year	[2]	0.8		1.7
Fair Value, One Year or Greater	[2]	1.8		1.8
Unrealized Losses, One Year or Greater	[2]	0		0.1
Fair Value, Total	[2]	43.9		74.4
Unrealized Losses, Total	[2]	0.8		1.8
Fixed Maturities [Member] | Corporate Bonds [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		523.1		490.5
Unrealized Losses, Less Than One Year		10.4		17.7
Fair Value, One Year or Greater		32.9		50.6
Unrealized Losses, One Year or Greater		1.5		1.8
Fair Value, Total		556		541.1
Unrealized Losses, Total		11.9		19.5
Fixed Maturities [Member] | Commercial Mortgage-backed Securities [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		83.7		70.6
Unrealized Losses, Less Than One Year		1.3		1.5
Fair Value, One Year or Greater		4.9		7.1
Unrealized Losses, One Year or Greater		0		0.1
Fair Value, Total		88.6		77.7
Unrealized Losses, Total		1.3		1.6
Fixed Maturities [Member] | Asset-backed Securities [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		68.3		69.7
Unrealized Losses, Less Than One Year		0.5		1.4
Fair Value, One Year or Greater		3.5		8.2
Unrealized Losses, One Year or Greater		0.5		0.7
Fair Value, Total		71.8		77.9
Unrealized Losses, Total		1		2.1
Equity Securities [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		52.3		62.1
Unrealized Losses, Less Than One Year		5.2		5.7
Fair Value, One Year or Greater		0		0
Unrealized Losses, One Year or Greater		0		0
Fair Value, Total		52.3		62.1
Unrealized Losses, Total		5.2		5.7
Other Investments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		0.3		0.3
Unrealized Losses, Less Than One Year		0.1		0.1
Fair Value, One Year or Greater		0		0
Unrealized Losses, One Year or Greater		0		0
Fair Value, Total		0.3		0.3
Unrealized Losses, Total		0.1		0.1
Short-Term Investments [Member]
Schedule Of Investments [Line Items]
Fair Value, Less Than One Year		31.6	[2]	4.8
Unrealized Losses, Less Than One Year		0	[2]	0
Fair Value, One Year or Greater		0	[2]	0
Unrealized Losses, One Year or Greater		0	[2]	0
Fair Value, Total		31.6	[2]	4.8
Unrealized Losses, Total		$ 0	[2]	$ 0
[1]	Unrealized losses one year or greater are less than $0.1 million.
[2]	Unrealized losses less than one year are less than $0.1 million.

Investments - Schedule of Agi51

Investments - Schedule of Aging of Unrealized Losses on Company's Investments in Fixed Maturities, Equity Securities and Other Investments (Parenthetical) (Detail) $ in Millions	Dec. 31, 2016USD ($)
Investments Debt And Equity Securities [Abstract]
Unrealized losses less than one year	$ 0.1
Unrealized losses one year or greater	$ 0.1

Investments - Schedule of Recog

Investments - Schedule of Recognized Other-than-temporary Losses on Fixed Maturities and Equity Portfolios (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Other-than-temporary impairment:
Other-than-temporary impairment losses	$ (1.1)	$ (4.9)	$ (1.5)	$ (6.6)
Corporate Bonds [Member]
Other-than-temporary impairment:
Other-than-temporary impairment losses	0	(0.5)	0	(1.1)
Equity Securities [Member]
Other-than-temporary impairment:
Other-than-temporary impairment losses	$ (1.1)	$ (4.4)	$ (1.5)	$ (5.5)

Investments - Schedule of Compa

Investments - Schedule of Company's Gross Realized Investment Gains (Losses) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule Of Investments [Line Items]
Gross realized investment and other gains	$ 22.6	$ 26.9	$ 51.6	$ 63
Gross realized investment and other losses	(18.1)	(29)	(32.5)	(67.9)
Net realized investment and other gains (losses)	4.5	(2.1)	19.1	(4.9)
Income tax expense	(1.3)	0	(5.7)	(1.2)
Net realized investment and other gains (losses), net of income taxes	3.2	(2.1)	13.4	(6.1)
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other gains	5.5	4.6	12.6	11
Gross realized investment and other losses	(5)	(6.5)	(11.2)	(14.9)
Equity Securities [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other gains	12	5.3	27.7	24.6
Gross realized investment and other losses	(1.8)	(1)	(2.5)	(7.1)
Other Investments [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other gains	4.8	16.8	10.8	27
Gross realized investment and other losses	(10.2)	(16.6)	(17.2)	(39.2)
Short-Term Investments [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other gains	0.3	0.2	0.5	0.4
Gross realized investment and other losses	0	0	(0.1)	(0.1)
Other-Than-Temporary Impairment Losses on Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other losses	0	(0.5)	0	(1.1)
Other-Than-Temporary Impairment Losses on Equity Securities [Member]
Schedule Of Investments [Line Items]
Gross realized investment and other losses	$ (1.1)	$ (4.4)	$ (1.5)	$ (5.5)

Investments - Schedule of Chang

Investments - Schedule of Changes in Unrealized Appreciation (Depreciation) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule Of Investments [Line Items]
Net unrealized investment and other gains before income taxes	$ 24.8	$ 38.8	$ 42.7	$ 69.8
Income tax provision	(5.1)	(12.3)	(9.7)	(16)
Net unrealized investment and other gains, net of income taxes	19.7	26.5	33	53.8
Fixed Maturities [Member]
Schedule Of Investments [Line Items]
Net unrealized investment and other gains before income taxes	19.5	25.9	32	64.8
Equity Securities [Member]
Schedule Of Investments [Line Items]
Net unrealized investment and other gains before income taxes	3.3	12.9	8.7	4
Other Investments [Member]
Schedule Of Investments [Line Items]
Net unrealized investment and other gains before income taxes	2	0	2	0.6
Short-Term Investments [Member]
Schedule Of Investments [Line Items]
Net unrealized investment and other gains before income taxes	$ 0	$ 0	$ 0	$ 0.4

Investments - Schedule of Fair

Investments - Schedule of Fair Value of Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts [Member] - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Schedule Of Investments [Line Items]
Fair value of foreign currency exchange forward contracts	$ (2)	$ 4
Operational Currency Exposure [Member]
Schedule Of Investments [Line Items]
Fair value of foreign currency exchange forward contracts	(0.4)	0
Asset Manager Investment Exposure [Member]
Schedule Of Investments [Line Items]
Fair value of foreign currency exchange forward contracts	(1.1)	0.7
Total return strategy [Member]
Schedule Of Investments [Line Items]
Fair value of foreign currency exchange forward contracts	$ (0.5)	$ 3.3

Investments - Schedule of Reali

Investments - Schedule of Realized Gains and Losses of Investment on Foreign Currency Exchange Forward Contracts (Detail) - Foreign Currency Exchange Forward Contracts [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts	$ 4.2	$ 16.4	$ 9.8	$ 25.9
Realized losses from foreign currency exchange forward contracts	(9.9)	(16.4)	(15.4)	(37.7)
Net realized investment losses on foreign currency exchange forward contracts	(5.7)	0	(5.6)	(11.8)
Operational Currency Exposure [Member]
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts	3.7	4.6	5.7	7.4
Realized losses from foreign currency exchange forward contracts	(3.7)	(7)	(5.9)	(15.5)
Asset Manager Investment Exposure [Member]
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts	0	2.3	0.5	2.3
Realized losses from foreign currency exchange forward contracts	(5.4)	0	(6.8)	(3.6)
Total return strategy [Member]
Schedule Of Investments [Line Items]
Realized gains from foreign currency exchange forward contracts	0.5	9.5	3.6	16.2
Realized losses from foreign currency exchange forward contracts	$ (0.8)	$ (9.4)	$ (2.7)	$ (18.6)

Investments - Regulatory Deposi

Investments - Regulatory Deposits, Pledged Securities and Letters of Credit (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Securities and cash on deposit supporting Lloyd’s business	$ 397.2	$ 161.8
Total restricted investments	602.3	366.4
Securities Deposits For Regulatory and Other Purposes [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Securities on deposit for regulatory and other purposes	176	168.7
Securities Pledged as Collateral [Member]
Other Than Temporary Impairment Credit Losses Recognized In Earnings [Line Items]
Securities pledged as collateral for letters of credit	$ 29.1	$ 35.9

Investments - Financial Assets

Investments - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		$ 4,624.1	$ 4,324.3	[1]
Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		539.4	539
Short-Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		365.9	405.5
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		4,193.6	3,880.8
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	1,081.7	1,048
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	3,109.6	2,830.4
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	2.3	2.4
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		3,276.2	2,932.4
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Collateralized Loan Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		260.2	264.3
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Residential Mortgage-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		223.3	176.8
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	292.7	228
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Collateralized Loan Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Residential Mortgage-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	2,981.6	2,702.4
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Collateralized Loan Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	260.2	264.3
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Residential Mortgage-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	223.3	176.8
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	1.9	2
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Collateralized Loan Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Residential Mortgage-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | U.S. Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		315.1	271.2
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | U.S. Governments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	292.7	228
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | U.S. Governments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	22.4	43.2
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | U.S. Governments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Governments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		244.2	237.3
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Governments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Governments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	244.2	237.3
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Foreign Governments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		348.4	382.8
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	348.4	382.8
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Obligations of States and Political Subdivisions [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		1,611.9	1,320.7
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Corporate Bonds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Corporate Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	1,610	1,318.7
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Corporate Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	1.9	2
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Commercial Mortgage-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		144	153.7
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Commercial Mortgage-backed Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Commercial Mortgage-backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	144	153.7
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Commercial Mortgage-backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		129.1	125.6
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Asset-backed Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	0	0
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Asset-backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	129.1	125.6
Fair Value, Measurements, Recurring [Member] | Fixed Maturities [Member] | Asset-backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	0	0
Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		108.9	95.5
Fair Value, Measurements, Recurring [Member] | Other Investments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	0	0
Fair Value, Measurements, Recurring [Member] | Other Investments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	108.9	95.5
Fair Value, Measurements, Recurring [Member] | Other Investments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	0	0
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		442.6	447.4
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	440.1	444.9
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	2.1	2.1
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	0.4	0.4
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments		365.9	405.5
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[2]	348.9	375.1
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[3]	17	30.4
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments	[4]	$ 0	$ 0
[1]	Derived from audited consolidated financial statements.
[2]	Quoted prices in active markets for identical assets
[3]	Significant other observable inputs
[4]	Significant unobservable inputs

Investments - Schedule of Recon

Investments - Schedule of Reconciliation of Beginning and Ending Balances for Investments Categorized as Level 3 (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 2.4	$ 0.7
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)	(0.1)	0
Purchases	0	2
Issuances	0	0
Sales	0	(0.3)
Settlements	0	0
Ending balance	2.3	2.4
Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at end of period	0	0
Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	0.4	0.7
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	(0.3)
Settlements	0	0
Ending balance	0.4	0.4
Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at end of period	0	0
Corporate Bonds [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	2	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in net income (loss)	0	0
Included in other comprehensive income (loss)	(0.1)	0
Purchases	0	2
Issuances	0	0
Sales	0	0
Settlements	0	0
Ending balance	1.9	2
Amount of total gains or losses for the year included in net income (loss) attributable to the change in unrealized gains or losses relating to assets still held at end of period	$ 0	$ 0

Reserves for Losses and Loss 60

Reserves for Losses and Loss Adjustment Expenses - Reserves for Losses and Loss Adjustment Expenses (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	[2]
Liability for Claims and Claims Adjustment Expense [Abstract]
Net reserves beginning of the year				$ 2,180.2	$ 2,133.3
Net Maybrooke reserves acquired				132.6	0
Losses and LAE incurred during current calendar year, net of reinsurance:
Current accident year				447.4	404.1
Prior accident years				5.7	(15.9)
Losses and LAE incurred during calendar year, net of reinsurance		$ 230.6	$ 196.6	453.1	388.2
Current accident year				88.9	65.3
Prior accident years				290.8	300.1
Losses and LAE payments made during current calendar year, net of reinsurance:				379.7	365.4
Change in participation interest	[1]			(23.2)	(36.3)
Foreign exchange adjustments				1.8	4.4
Net reserves - end of period		2,364.8	2,124.2	2,364.8	2,124.2
Reinsurance recoverables on unpaid losses and LAE, end of year		(1,268)	(1,057.7)	(1,268)	(1,057.7)
Gross reserves - end of period		$ 3,632.8	$ 3,181.9	$ 3,632.8	$ 3,181.9	$ 3,350.8
[1]	Amount represents decreases in reserves due to change in syndicate participation
[2]	Derived from audited consolidated financial statements.

Reserves for Losses and Loss 61

Reserves for Losses and Loss Adjustment Expenses - Impact from Unfavorable (Favorable) Development of Prior Accident Years' Loss and LAE Reserves on Each Reporting Segment (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total unfavorable (favorable) prior-year development	$ 5.7	$ (15.9)
U.S. Operations [Member]
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total unfavorable (favorable) prior-year development	(18)	(11.9)
International Operations [Member]
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total unfavorable (favorable) prior-year development	19.6	(10.2)
Run Off Lines [Member]
Schedule Of Prior Accident Years Loss And Loss Adjustment Expense Reserves Development [Line Items]
Total unfavorable (favorable) prior-year development	$ 4.1	$ 6.2

Junior Subordinated Debenture62

Junior Subordinated Debentures - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Junior subordinated debentures	$ 256.4	$ 172.7	[1]
Maybrooke Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Unsecured Debt	83.7
Junior subordinated debentures	91.8
Trust Preferred Debentures [Member]
Debt Instrument [Line Items]
Junior subordinated debentures	$ 172.7	$ 172.7
Trust Preferred Debentures [Member] | Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	100.00%	100.00%
[1]	Derived from audited consolidated financial statements.

Junior Subordinated Debenture63

Junior Subordinated Debentures - Schedule of Junior Subordinated Debentures (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Junior subordinated debentures, Amount	$ 256.4	$ 172.7	[1]
Trust Preferred Debentures [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Amount	$ 172.7	$ 172.7
Trust Preferred Debentures [Member] | PXRE Capital Statutory Trust II [Member] | Argo Group [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	May 15, 2003	May 15, 2003
Junior subordinated debentures, Maturity date	May 15, 2033	May 15, 2033
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	5.28%	5.00%
Junior subordinated debentures, Amount	$ 18.1	$ 18.1
Trust Preferred Debentures [Member] | PXRE Capital Trust VI [Member] | Argo Group [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	Nov. 6, 2003	Nov. 6, 2003
Junior subordinated debentures, Maturity date	Sep. 30, 2033	Sep. 30, 2033
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	5.20%	4.90%
Junior subordinated debentures, Amount	$ 10.3	$ 10.3
Trust Preferred Debentures [Member] | Argonaut Group Statutory Trust I [Member] | Argo Group US [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	May 15, 2003	May 15, 2003
Junior subordinated debentures, Maturity date	May 15, 2033	May 15, 2033
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	5.28%	5.00%
Junior subordinated debentures, Amount	$ 15.5	$ 15.5
Trust Preferred Debentures [Member] | Argonaut Group Statutory Trust III [Member] | Argo Group US [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	Dec. 16, 2003	Dec. 16, 2003
Junior subordinated debentures, Maturity date	Jan. 8, 2034	Jan. 8, 2034
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	5.26%	4.98%
Junior subordinated debentures, Amount	$ 12.3	$ 12.3
Trust Preferred Debentures [Member] | Argonaut Group Statutory Trust IV [Member] | Argo Group US [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	Apr. 29, 2004	Apr. 29, 2004
Junior subordinated debentures, Maturity date	Apr. 29, 2034	Apr. 29, 2034
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	5.03%	4.76%
Junior subordinated debentures, Amount	$ 13.4	$ 13.4
Trust Preferred Debentures [Member] | Argonaut Group Statutory Trust V [Member] | Argo Group US [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	May 26, 2004	May 26, 2004
Junior subordinated debentures, Maturity date	May 24, 2034	May 24, 2034
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	5.04%	4.77%
Junior subordinated debentures, Amount	$ 12.3	$ 12.3
Trust Preferred Debentures [Member] | Argonaut Group Statutory Trust VI [Member] | Argo Group US [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	May 12, 2004	May 12, 2004
Junior subordinated debentures, Maturity date	May 12, 2034	May 12, 2034
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	5.07%	4.79%
Junior subordinated debentures, Amount	$ 13.4	$ 13.4
Trust Preferred Debentures [Member] | Argonaut Group Statutory Trust VII [Member] | Argo Group US [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	Sep. 17, 2004	Sep. 17, 2004
Junior subordinated debentures, Maturity date	Dec. 15, 2034	Dec. 15, 2031
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	4.85%	4.56%
Junior subordinated debentures, Amount	$ 15.5	$ 15.5
Trust Preferred Debentures [Member] | Argonaut Group Statutory Trust VIII [Member] | Argo Group US [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	Sep. 22, 2004	Sep. 22, 2004
Junior subordinated debentures, Maturity date	Sep. 22, 2034	Sep. 22, 2034
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	4.84%	4.55%
Junior subordinated debentures, Amount	$ 15.5	$ 15.5
Trust Preferred Debentures [Member] | Argonaut Group Statutory Trust IX [Member] | Argo Group US [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	Oct. 22, 2004	Oct. 22, 2004
Junior subordinated debentures, Maturity date	Dec. 15, 2034	Dec. 15, 2034
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	4.85%	4.56%
Junior subordinated debentures, Amount	$ 15.5	$ 15.5
Trust Preferred Debentures [Member] | Argonaut Group Statutory Trust X [Member] | Argo Group US [Member]
Debt Instrument [Line Items]
Junior subordinated debentures, Issue date	Sep. 15, 2005	Sep. 15, 2005
Junior subordinated debentures, Maturity date	Sep. 15, 2035	Sep. 15, 2035
Junior subordinated debentures, Rate Structure	2016 and 2015: 3M LIBOR + 4.10%
Junior subordinated debentures, interest rate stated percentage	4.65%	4.36%
Junior subordinated debentures, Amount	$ 30.9	$ 30.9
[1]	Derived from audited consolidated financial statements.

Junior Subordinated Debenture64

Junior Subordinated Debentures - Schedule of Maybrooke Junior Subordinated Debentures (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Principal	$ 143.8	$ 143.8
Maybrooke Junior Subordinated Debentures [Member]
Debt Instrument [Line Items]
Issue Date	Sep. 15, 2007
Maturity	Sep. 15, 2037
Rate Structure	3M LIBOR + 3.15%
Interest Rate	4.40%
Principal	$ 91.8
Carrying Value	$ 83.7

Other Indebtedness - Schedule o

Other Indebtedness - Schedule of Terms and Principal Amounts of Each Debt Instrument (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Other indebtedness	$ 182.5	$ 55.4	[1]
Term Loan [Member]
Debt Instrument [Line Items]
Other indebtedness	125	0
Floating Rate Loan Stock [Member]
Debt Instrument [Line Items]
Other indebtedness	56.9	54.8
Other Debt [Member]
Debt Instrument [Line Items]
Other indebtedness	$ 0.6	$ 0.6
[1]	Derived from audited consolidated financial statements.

Other Indebtedness - Additional

Other Indebtedness - Additional Information (Detail) - USD ($)	1 Months Ended	6 Months Ended	12 Months Ended
	Jan. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Mar. 03, 2017	Mar. 07, 2014
Debt Instrument [Line Items]
Floating rate loan stock denominated in Euros		$ 40,400,000	$ 38,300,000
New Credit Agreement [Member]
Debt Instrument [Line Items]
Maturity		Mar. 3, 2019
New Credit Agreement [Member] | J P Morgan Chase Bank [Member]
Debt Instrument [Line Items]
Line of credit, maximum borrowing amount				$ 325,000,000
New Credit Agreement [Member] | Revolving Credit Facility [Member] | J P Morgan Chase Bank [Member]
Debt Instrument [Line Items]
Line of credit, maximum borrowing amount				200,000,000
Revolving credit facility maturity date		Mar. 3, 2022
Letter of credit facility amount outstanding		$ 0	0
New Credit Agreement [Member] | Term Loan [Member] | J P Morgan Chase Bank [Member]
Debt Instrument [Line Items]
Line of credit, maximum borrowing amount				125,000,000
New Credit Agreement [Member] | Letter Of Credit [Member] | J P Morgan Chase Bank [Member]
Debt Instrument [Line Items]
Line of credit, maximum borrowing amount		200,000,000
Letter of credit facility amount		$ 500,000		$ 200,000
Prior Agreement [Member] | Revolving Credit Facility [Member] | Maybrooke [Member]
Debt Instrument [Line Items]
Repayments of borrowings	$ 125,000,000
Prior Agreement [Member] | Revolving Credit Facility [Member] | J P Morgan Chase Bank [Member]
Debt Instrument [Line Items]
Line of credit, maximum borrowing amount					$ 175,000,000
Prior Agreement [Member] | Letter Of Credit [Member] | J P Morgan Chase Bank [Member]
Debt Instrument [Line Items]
Letter of credit facility amount			$ 200,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage		100.00%	100.00%
Other Debt [Member]
Debt Instrument [Line Items]
Note payable as part of ARIS acquisition		$ 600,000	$ 600,000
Maturity		Apr. 1, 2019
Debt instrument, interest rate terms		The note had a variable interest rate of 2.00% above 30-day LIBOR, with the variable interest rate being reset quarterly and subject to certain interest rate ceilings. Interest payments are payable quarterly.
Other Debt [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Variable interest rate of note payable, above 30-day LIBOR		2.00%

Other Indebtedness - Schedule67

Other Indebtedness - Schedule of Floating Rate Loan Stock, Notes Outstanding (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Amount	$ 56.9	$ 54.8
Other indebtedness, Amount	$ 182.5	$ 55.4	[1]
Floating Rate Loan Stock, U.S. Dollar, Start Year 2004 [Member]
Debt Instrument [Line Items]
Issue Date	Dec. 8, 2004	Dec. 8, 2004
Maturity	Nov. 15, 2034	Nov. 15, 2034
Rate Structure	First Quarter of 2017 and 2016: 6 month LIBOR + 4.2%
Interest Rate	5.53%	5.18%
Amount	$ 6.5	$ 6.5
Floating Rate Loan Stock, Euro, Start Year 2005 [Member]
Debt Instrument [Line Items]
Issue Date	Sep. 6, 2005	Sep. 6, 2005
Maturity	Aug. 22, 2035	Aug. 22, 2035
Rate Structure	First Quarter of 2017 and 2016: 3 month LIBOR + 4.0%
Interest Rate	3.67%	3.70%
Amount	$ 13.5	$ 12.8
Floating Rate Loan Stock, U.S. Dollar, Start Year 2006 [Member]
Debt Instrument [Line Items]
Issue Date	Oct. 31, 2006	Oct. 31, 2006
Maturity	Jan. 15, 2036	Jan. 15, 2036
Rate Structure	First Quarter of 2017 and 2016: 6 month LIBOR + 4.0%
Interest Rate	5.33%	4.98%
Amount	$ 10	$ 10
Floating Rate Loan Stock, Euro, Start Year 2006 [Member]
Debt Instrument [Line Items]
Issue Date	Oct. 31, 2006	Oct. 31, 2006
Maturity	Nov. 22, 2036	Nov. 22, 2036
Rate Structure	First Quarter of 2017 and 2016: 3 month LIBOR + 4.0%
Interest Rate	3.67%	3.70%
Amount	$ 11.8	$ 11.2
Floating Rate Loan Stock, Euro, Start Year 2007 [Member]
Debt Instrument [Line Items]
Issue Date	Jun. 8, 2007	Jun. 8, 2007
Maturity	Sep. 15, 2037	Sep. 15, 2037
Rate Structure	First Quarter of 2017and 2016: 3 month LIBOR + 3.9%
Interest Rate	3.57%	3.58%
Amount	$ 15.1	$ 14.3
New Credit Agreement [Member]
Debt Instrument [Line Items]
Issue Date	Mar. 3, 2017
Maturity	Mar. 3, 2019
Rate Structure	2 month LIBOR + 1.5%
Interest Rate	2.54%
Other indebtedness, Amount	$ 125
[1]	Derived from audited consolidated financial statements.

Disclosures about Fair Value 68

Disclosures about Fair Value of Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Financial Instruments Owned and Pledged as Collateral [Line Items]
Premiums receivable	$ 672.6	$ 463.8	[1]
Reinsurance recoverables	1,519.6	1,385.6	[1]
Premiums receivable, allowance for doubtful accounts	2.9	2.7
Over 90 Days [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Premiums receivable	19.3	14.3
Reinsurance recoverables	12.2	11.2
Reinsurance recoverables, allowance for doubtful accounts	2.1	2.1
Premiums receivables, secured by collateral		0.1
Reinsurance recoverables, secured by collateral	$ 0.6	$ 0.6
[1]	Derived from audited consolidated financial statements.

Disclosures about Fair Value 69

Disclosures about Fair Value of Financial Instruments - Summary of Company's Financial Instruments Whose Carrying Amount Did Not Equal Fair Value (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Maybrooke Junior Subordinated Debentures [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	$ 83.7	$ 0
Maybrooke Junior Subordinated Debentures [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	85.2	0
Junior Subordinated Debentures [Member] | Trust Preferred Debentures [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	172.7	172.7
Junior Subordinated Debentures [Member] | Trust Preferred Debentures [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	167.5	162.4
Senior Unsecured Fixed Rate Notes [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	139.5	139.5
Senior Unsecured Fixed Rate Notes [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	139.3	139.3
Floating Rate Loan Stock [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	56.9	54.8
Floating Rate Loan Stock [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Instruments	$ 55.1	$ 51.5

Shareholders Equity - Additiona

Shareholders Equity - Additional Information (Detail) - USD ($)	Aug. 08, 2017	Jun. 26, 2017	Jun. 01, 2017	Jun. 17, 2016	May 03, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Class Of Stock [Line Items]
Dividends declaration date			Jun. 1, 2017
Dividend declared per common share			$ 0.27			$ 0.27	$ 0.22	$ 0.54	$ 0.42
Dividends payable date			Jun. 26, 2017
Dividend payable, date of record			Jun. 12, 2017
Cash dividends paid - common shares, total		$ 8,300,000
2016 Repurchase Authorization [Member]
Class Of Stock [Line Items]
Remaining number of shares available under repurchase authorization, Value						$ 127,500,000		$ 127,500,000
Common shares repurchased on open market								46,500
Common shares repurchased on open market, total cost								$ 2,800,000
2016 Repurchase Authorization [Member] | Maximum [Member]
Class Of Stock [Line Items]
Total number of shares authorized for purchase, Value					$ 150,000,000
Stock Dividend [Member]
Class Of Stock [Line Items]
Dividends declaration date					May 3, 2016
Dividends payable date					Jun. 15, 2016
Dividend payable, date of record					Jun. 1, 2016
Stock dividend declared					10.00%
Additional stock issued as dividend					2,735,542
Cash Dividend [Member]
Class Of Stock [Line Items]
Dividends declaration date					May 3, 2016
Dividend declared per common share					$ 0.22
Dividends payable date					Jun. 17, 2016
Dividend payable, date of record					Jun. 1, 2016
Cash dividends paid - common shares, total				$ 6,900,000
Subsequent Event [Member]
Class Of Stock [Line Items]
Dividends declaration date	Aug. 8, 2017
Dividend declared per common share	$ 0.27
Dividends payable date	Sep. 15, 2017
Dividend payable, date of record	Sep. 1, 2017

Shareholders Equity - Schedule

Shareholders Equity - Schedule of Repurchase of Shares (Detail) - 10b5-1 Trading Plan Initiated In 06/14/2017 [Member] $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2016USD ($)$ / sharesshares
Equity Class Of Treasury Stock [Line Items]
Date Trading Plan Initiated	Jun. 14, 2017
Trading Plan Purchase Period Start Date	Jun. 20, 2017
Common shares repurchased on open market | shares	46,500
Average Price of Shares Repurchased | $ / shares	$ 59.54
Total Cost (in millions) | $	$ 2.8
Repurchase Authorization Year	2,016
Trading Plan Purchase Period End Date	Jun. 28, 2017

Accumulated Other Comprehensi72

Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017		Jun. 30, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			$ 47.7	[1]	$ 11.5
Other comprehensive income (loss) before reclassifications			45.1		61.8
Amounts reclassified from accumulated other comprehensive income (loss)			(12.7)		(4.2)
Other comprehensive income, net of tax	$ 18.5	$ 28.8	32.4		57.6
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	80.1	69.1	80.1		69.1
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			(17.6)		(21.6)
Other comprehensive income (loss) before reclassifications			(0.6)		3.8
Amounts reclassified from accumulated other comprehensive income (loss)			0		0
Other comprehensive income, net of tax			(0.6)		3.8
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	(18.2)	(17.8)	(18.2)		(17.8)
Unrealized Holding Gains on Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			72.4		40
Other comprehensive income (loss) before reclassifications			45.7		58
Amounts reclassified from accumulated other comprehensive income (loss)			(12.7)		(4.2)
Other comprehensive income, net of tax			33		53.8
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	105.4	93.8	105.4		93.8
Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Beginning Balance			(7.1)		(6.9)
Other comprehensive income (loss) before reclassifications			0		0
Amounts reclassified from accumulated other comprehensive income (loss)			0		0
Other comprehensive income, net of tax			0		0
Accumulated Other Comprehensive Income (Loss) Net Of Tax, Ending Balance	$ (7.1)	$ (6.9)	$ (7.1)		$ (6.9)
[1]	Derived from audited consolidated financial statements.

Accumulated Other Comprehensi73

Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Unrealized gains on securities:
Reclassification adjustment for gains included in net income	$ (2.7)	$ (0.3)	$ (18.9)	$ (8.1)
Provision for income taxes (benefit)	1	(0.2)	6.2	3.9
Net of taxes			(12.7)	(4.2)
Unrealized Holding Gains on Securities [Member]
Unrealized gains on securities:
Net of taxes			(12.7)	(4.2)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Holding Gains on Securities [Member]
Unrealized gains on securities:
Reclassification adjustment for gains included in net income	(2.7)	(0.3)	(18.9)	(8.1)
Provision for income taxes (benefit)	1	(0.2)	6.2	3.9
Net of taxes	$ (1.7)	$ (0.5)	$ (12.7)	$ (4.2)

Net Income Per Common Share - N

Net Income Per Common Share - Net Income Per Common Share on Basic and Diluted Basis (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 46	$ 30.9	$ 82.7	$ 58.6
Weighted average common shares outstanding - basic	30,201,457	30,187,592	30,124,696	30,333,417
Effect of dilutive securities:
Equity compensation awards	846,624	622,564	870,476	637,772
Weighted average common shares outstanding - diluted	31,048,081	30,810,156	30,995,172	30,971,189
Net income per common share - basic	$ 1.52	$ 1.03	$ 2.75	$ 1.93
Net income per common share - diluted	$ 1.48	$ 1	$ 2.67	$ 1.89

Net Income Per Common Share - A

Net Income Per Common Share - Additional Information (Detail) - shares	Jun. 30, 2017	Dec. 31, 2016		Jun. 30, 2016
Earnings Per Share [Abstract]
Treasury shares, shares	10,075,255	10,028,755	[1]	9,900,239
[1]	Derived from audited consolidated financial statements.

Supplemental Cash Flow Inform76

Supplemental Cash Flow Information - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Income Taxes Paid Net [Abstract]
Income taxes paid	$ 9.9	$ 1.3
Income taxes recovered	$ 2.2	$ 0.3

Supplemental Cash Flow Inform77

Supplemental Cash Flow Information - Schedule of Interest Paid (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Supplemental Cash Flow [Line Items]
Total interest paid	$ 12.6	$ 9.7
Revolving Credit Facility [Member]
Supplemental Cash Flow [Line Items]
Total interest paid	0.3	0
Senior Unsecured Fixed Rate Notes [Member]
Supplemental Cash Flow [Line Items]
Total interest paid	4.7	4.7
Junior Subordinated Debentures [Member]
Supplemental Cash Flow [Line Items]
Total interest paid	6	3.8
Other Indebtedness [Member]
Supplemental Cash Flow [Line Items]
Total interest paid	$ 1.6	$ 1.2

Share-based Compensation - Addi

Share-based Compensation - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based compensation arrangement by share-based payment award, award vesting period, years	5 years	5 years

Share-based Compensation - Fair

Share-based Compensation - Fair Value Assumptions (Detail)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free rate of return	1.83%	1.00%
Expected dividend yields	1.68%	1.70%
Expected award life (years)	4 years 5 months 23 days	4 years 6 months 14 days
Expected volatility	18.64%	19.70%

Share-Based Compensation - 2014

Share-Based Compensation - 2014 Long-Term Incentive Plan - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2014	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Nov. 30, 2007
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period, years				5 years	5 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, compensation expense		$ 2.4	$ 1.8	$ 5.2	$ 3.5
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		25.9		$ 25.9
Restricted Stock Units (RSUs) [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period, years				5 years
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period, years				8 years
Stock-Settled SARs Activity [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, compensation expense		2	1.2	$ 2.7	2.6
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		6		$ 6
Stock-Settled SARs Activity [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period, years				1 year
Stock-Settled SARs Activity [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period, years				4 years
Cash-Settled SARs Activity [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, compensation expense		2.3		$ 0.9
Employee service share-based compensation, unrecognized compensation costs on non-vested awards		$ 0		$ 0
Share-based compensation arrangement by share-based payment award, compensation expense recouped			$ 0.2		$ 0.5
2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized						4,500,000
Share-based compensation arrangement by share-based payment award, number of shares available for grant	1,460,000
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, additional number of shares authorized	2,800,000
Count of restricted shares, settle in common shares				2.75

Share-based Compensation - Summ

Share-based Compensation - Summary of Restricted Share Activity (Detail) - Restricted Stock Units (RSUs) [Member]	6 Months Ended
	Jun. 30, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2017 | shares	702,030
Granted, Shares | shares	204,467
Vested and issued, Shares | shares	(146,878)
Expired or forfeited, Shares | shares	(22,969)
Shares, Outstanding at June 30, 2017 | shares	736,650
Weighted-Average Grant Date Fair Value, Outstanding at January 1, 2017 | $ / shares	$ 42.69
Granted, Weighted-Average Grant Date Fair Value | $ / shares	62.68
Vested and issued, Weighted-Average Grant Date Fair Value | $ / shares	41.47
Expired or forfeited, Weighted-Average Grant Date Fair Value | $ / shares	49.62
Weighted-Average Grant Date Fair Value, Outstanding at June 30, 2017 | $ / shares	$ 48.26

Share-based Compensation - Su82

Share-based Compensation - Summary of Stock-Settled SARs Activity (Detail) - Stock-Settled SARs Activity [Member]	6 Months Ended
	Jun. 30, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2017 | shares	1,982,695
Exercised, Shares | shares	(315,835)
Expired or forfeited, Shares | shares	(58,721)
Shares, Outstanding at June 30, 2017 | shares	1,608,139
Weighted-Average Exercise Price, Outstanding at January 1, 2017 | $ / shares	$ 34.80
Exercised, Weighted-Average Exercise Price | $ / shares	32.61
Expired or forfeited, Weighted-Average Exercise Price | $ / shares	40.44
Weighted-Average Exercise Price, Outstanding at June 30, 2017 | $ / shares	$ 35.02

Share-based Compensation - Su83

Share-based Compensation - Summary of Cash-Settled SARs Activity (Detail) - Cash-Settled SARs Activity [Member]	6 Months Ended
	Jun. 30, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2017 | shares	500,486
Exercised, Shares | shares	(185,359)
Expired or forfeited, Shares | shares	(14,503)
Shares, Outstanding at June 30, 2017 | shares	300,624
Weighted-Average Exercise Price, Outstanding at January 1, 2017 | $ / shares	$ 32.08
Exercised, Weighted-Average Exercise Price | $ / shares	32.90
Expired or forfeited, Weighted-Average Exercise Price | $ / shares	23.69
Weighted-Average Exercise Price, Outstanding at June 30, 2017 | $ / shares	$ 31.98

Underwriting, Acquisition and84

Underwriting, Acquisition and Insurance Expenses - Underwriting, Acquisition and Insurance Expenses (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Underwriting Acquisition And Insurance Expenses [Abstract]
Commissions	$ 69.2	$ 62.1	$ 130.4	$ 119.2
General expenses	88	71.1	176.7	141.7
Premium taxes, boards and bureaus	6.7	6.3	14.1	12.9
Underwriting, acquisition and insurance expenses, total	163.9	139.5	321.2	273.8
Net deferral of policy acquisition costs	(9.2)	(6.5)	(12.9)	(8.2)
Total underwriting, acquisition and insurance expenses	$ 154.7	$ 133	$ 308.3	$ 265.6

Underwriting, Acquisition and85

Underwriting, Acquisition and Insurance Expenses - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Underwriting Acquisition And Insurance Expenses [Abstract]
Increase in general expense	$ 16.9	$ 35

Income Taxes - Income Tax Provi

Income Taxes - Income Tax Provision (Benefit) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Current tax provision	$ 15.5	$ 6.5	$ 15.5	$ 8
Future tax deductions	(9.7)	2	(3.6)	4.9
Valuation allowance change	(1)	0.2	(1.1)	1.2
Income tax provision	$ 4.8	$ 8.7	$ 10.8	$ 14.1

Income Taxes - Schedule of Pre-

Income Taxes - Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates (Detail) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ 50.8		$ 39.6		$ 93.5		$ 72.7
Effective Tax Rate		9.40%		22.10%		11.50%		19.40%
Bermuda [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ 25.3		$ 22.1		$ 51.7		$ 44.1
Effective Tax Rate		0.00%		0.00%		0.00%		0.00%
United States [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ 34.7		$ 26.5		$ 58.7		$ 49.8
Effective Tax Rate		23.30%		30.90%		24.80%		27.50%
United Kingdom [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ (6.5)		$ (9.8)		$ (12)		$ (22.1)
Effective Tax Rate		52.80%		(5.70%)		32.30%		(1.70%)
Belgium [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ 0.1		$ 0	[1]	$ 0.1		$ 0	[1]
Effective Tax Rate		36.60%		16.30%		36.20%		32.00%
Brazil [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ 0.6		$ 0.8		$ (0.2)		$ 0.7
Effective Tax Rate		0.00%		0.00%		0.00%		0.00%
United Arab Emirates [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ (2.2)		$ 0	[1]	$ (3.5)		$ 0	[1]
Effective Tax Rate		0.00%		0.00%		0.00%		0.00%
Ireland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ 0	[1]	$ (0.1)		$ 0	[1]	$ (0.1)
Effective Tax Rate		0.00%		0.00%		0.00%		0.00%
Malta [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ 0.5		$ 0.1		$ 1.1		$ 0.3
Effective Tax Rate		0.00%		0.00%		0.00%		0.00%
Luxembourg [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ (1.7)		$ 0		$ (2.4)		$ 0
Effective Tax Rate		0.00%		0.00%		0.00%		0.00%
Switzerland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	[1]	$ 0		$ 0		$ 0		$ 0
Effective Tax Rate		22.10%		22.80%		20.80%		21.10%
[1]	Pre-tax income for the respective year was less than $0.1 million.

Income Taxes - Schedule of Pr88

Income Taxes - Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates (Parenthetical) (Detail) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ 50.8		$ 39.6		$ 93.5		$ 72.7
Belgium [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		0.1		0	[1]	0.1		0	[1]
United Arab Emirates [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		(2.2)		0	[1]	(3.5)		0	[1]
Ireland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		0	[1]	(0.1)		0	[1]	(0.1)
Switzerland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	[1]	0		0		0		0
Maximum [Member] | Belgium [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)				0.1				0.1
Maximum [Member] | United Arab Emirates [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)				0.1				0.1
Maximum [Member] | Ireland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		0.1				0.1
Maximum [Member] | Switzerland [Member]
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)		$ 0.1		$ 0.1		$ 0.1		$ 0.1
[1]	Pre-tax income for the respective year was less than $0.1 million.

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Difference Between Provision for Income Taxes and Expected Tax Provision at Weighted Average Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Income tax provision at expected rate	$ 10.8	$ 7.6	$ 18	$ 13.4
Tax-exempt interest	(0.7)	(0.9)	(1.5)	(1.8)
Dividends received deduction	(0.4)	(0.8)	(0.9)	(1.3)
Valuation allowance change	(1)	0.2	(1.1)	1.2
Other permanent adjustments, net	(1.1)	0	(1)	0.2
Adjustment for prior period	0	0	(0.7)	0
Adjustment for annualized rate	(1.8)	0.9	(2.5)	(0.6)
Other foreign adjustments	(0.4)	(0.6)	0.4	(0.6)
Deferred tax rate reduction	0	0	0	(0.3)
State income tax	0.1	0	0.1	0
Foreign exchange adjustments	(0.9)	2.1	(0.3)	3.6
Foreign withholding taxes	0.2	0.2	0.3	0.3
Income tax provision	4.8	8.7	10.8	14.1
Income tax provision - Foreign	(3.3)	0.6	(3.8)	0.4
Income tax provision - United States, Federal	7.8	7.9	14.2	13.5
Income tax provision - United States, State	0.1	0	0.1	0
Foreign withholding tax - United States	$ 0.2	$ 0.2	$ 0.3	$ 0.2

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Taxes Disclosure [Line Items]
Net operating losses carryback period			2 years
Capital losses carryback period			3 years
Total net deferred tax liabilities	$ 13,000,000		$ 13,000,000
Net operating loss carryforward	15,400,000		15,400,000
Loss carryforwards per year	2,800,000		2,800,000
Valuation allowance	25,200,000		25,200,000
Increase (decrease) in valuation allowance	1,000,000	$ (200,000)	1,100,000	$ (1,200,000)
Unrecognized tax benefits	0	$ 0	0	$ 0
December 31, 2025 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized			13,900,000
December 31, 2027 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized			1,500,000
Brazil [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	8,000,000		8,000,000
Increase (decrease) in valuation allowance			300,000
Maybrooke [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	2,700,000		2,700,000
Increase (decrease) in valuation allowance			2,700,000
Malta [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	1,000,000		1,000,000
Increase (decrease) in valuation allowance			300,000
PXRE Reinsurance Company [Member]
Income Taxes Disclosure [Line Items]
Valuation allowance	13,500,000		13,500,000
Increase (decrease) in valuation allowance			500,000
ARIS [Member]
Income Taxes Disclosure [Line Items]
Net operating loss carryforward	$ 1,000,000		1,000,000
ARIS [Member] | December 31, 2027 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized			200,000
ARIS [Member] | December 31, 2028 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized			400,000
ARIS [Member] | December 31, 2029 [Member]
Income Taxes Disclosure [Line Items]
Loss carryforwards, amounts expiring if not utilized			$ 400,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2017USD ($)
Commitments And Contingencies [Line Items]
Contractual commitments related to its limited partnership investments	$ 119.7
Maximum [Member]
Commitments And Contingencies [Line Items]
Contractual commitments period	13 years

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2017USD ($)Segment	Dec. 31, 2016USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment	2
Assets associated with trade capital providers | $	$ 690.6	$ 630.4

Segment Information - Revenue a

Segment Information - Revenue and Income (Loss) Before Income Taxes for Each Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Earned premiums	$ 399.1	$ 344.9	$ 778.5	$ 689.8
Net investment income	43.6	35.7	74.1	56.9
Fee and other income	3.8	5.8	7.4	12.6
Net realized investment and other gains (losses)	4.5	(2.1)	19.1	(4.9)
Total revenue	451	384.3	879.1	754.4
Income (loss) before income taxes	50.8	39.6	93.5	72.7
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net investment income	3.3	1.5	5.2	0.6
Income (loss) before income taxes	(14.6)	(15.8)	(29.5)	(31.1)
Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	60.9	57.5	103.9	108.7
U.S. Operations [Member]
Segment Reporting Information [Line Items]
Earned premiums	229.1	206.8	450.3	413.4
Net investment income	27.3	21.7	47.2	35.5
U.S. Operations [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	53	45.4	90.2	80.3
International Operations [Member]
Segment Reporting Information [Line Items]
Earned premiums	169.9	137.9	328.1	276.2
Net investment income	10.1	9.1	16.7	15.2
International Operations [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	9.1	15.3	17.4	33
Run Off Lines [Member]
Segment Reporting Information [Line Items]
Earned premiums	0.1	0.2	0.1	0.2
Net investment income	2.9	3.4	5	5.6
Run Off Lines [Member] | Operating Segments [Members]
Segment Reporting Information [Line Items]
Income (loss) before income taxes	$ (1.2)	$ (3.2)	$ (3.7)	$ (4.6)

Segment Information - Schedule

Segment Information - Schedule of Earned Premiums by Geographic Location (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	$ 399.1	$ 344.9	$ 778.5	$ 689.8
Bermuda [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	23.1	29	48.7	57.1
Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	12.3	10	25.1	19.2
Malta [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	1.3	0.5	2.3	1
United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	133.3	98.1	252.1	198.7
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total earned premiums	$ 229.1	$ 207.3	$ 450.3	$ 413.8

Segment Information - Identifia

Segment Information - Identifiable Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 8,240.7	$ 7,205	[1]
U.S. Operations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	4,127.7	3,961.2
International Operations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	3,223.6	2,356.9
Run Off Lines [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	414.6	537
Corporate and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Identifiable assets	$ 474.8	$ 349.9
[1]	Derived from audited consolidated financial statements.

Senior Unsecured Fixed Rate N96

Senior Unsecured Fixed Rate Notes - Additional Information (Detail) - USD ($)	1 Months Ended	6 Months Ended
	Sep. 30, 2012	Jun. 30, 2017	Dec. 31, 2016
Schedule Of Equity Method Investments [Line Items]
Principal amount of senior note		$ 143,800,000	$ 143,800,000
Senior Unsecured Fixed Rate Notes [Member]
Schedule Of Equity Method Investments [Line Items]
Principal amount of senior note	$ 143,750,000
Debt instrument interest rate stated percentage	6.50%
Maturity		Sep. 15, 2042
Initial maturity date		Sep. 15, 2017
Debt Instrument, Redemption Price, Percentage	100.00%

Senior Unsecured Fixed Rate N97

Senior Unsecured Fixed Rate Notes - Schedule Of Unamortized Debt Issuance Costs Deducted From Carrying Value Of Debt Liability (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Principal	$ 143.8	$ 143.8
Less: unamortized debt issuance costs	(4.3)	(4.3)
Senior unsecured fixed rate notes, less unamortized debt issuance costs	$ 139.5	$ 139.5	[1]
[1]	Derived from audited consolidated financial statements.

Senior Unsecured Fixed Rate N98

Senior Unsecured Fixed Rate Notes - Condensed Consolidating Balance Sheet (Detail) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016		Jun. 30, 2016	Dec. 31, 2015
Assets
Investments		$ 4,624.1	$ 4,324.3	[1]
Cash		214.5	86	[1]	$ 120.6	$ 121.7
Accrued investment income		23	20.7	[1]
Premiums receivable		672.6	463.8	[1]
Reinsurance recoverables		1,519.6	1,385.6	[1]
Goodwill and other intangible assets, net		261.1	219.9
Deferred acquisition costs, net		162.8	139.1	[1]
Ceded unearned premiums		436.6	302.8	[1]
Other assets		326.4	262.8	[1]
Intercompany note receivable		0	0
Investments in subsidiaries		0	0
Total assets		8,240.7	7,205	[1]
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses		3,632.8	3,350.8	[1]	3,181.9
Unearned premiums		1,176.2	970	[1]
Funds held and ceded reinsurance payable, net		744.9	543.7
Long-term debt		578.4	367.6
Current income taxes payable, net		13.4	8.1	[1]
Deferred tax liabilities, net		38.2	24.1	[1]
Accrued underwriting expenses and other liabilities		165.5	148
Due to affiliates		0	0
Intercompany note payable		0
Total liabilities		6,349.4	5,412.3	[1]
Total shareholders' equity		1,891.3	1,792.7	[1]
Total liabilities and shareholders' equity		8,240.7	7,205	[1]
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]
Assets
Investments		1.2	2.2
Cash		0	0		0	0
Accrued investment income		0	0
Premiums receivable		0	0
Reinsurance recoverables		0	0
Goodwill and other intangible assets, net		43.5	0
Deferred acquisition costs, net		0	0
Ceded unearned premiums		0	0
Other assets		8.8	8.7
Intercompany note receivable		0	0
Investments in subsidiaries		2,156.4	1,834.4
Total assets		2,209.9	1,845.3
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses		0	0
Unearned premiums		0	0
Funds held and ceded reinsurance payable, net		0	0
Long-term debt		153.4	28.4
Current income taxes payable, net		0	0
Deferred tax liabilities, net		0	0
Accrued underwriting expenses and other liabilities		11	13.7
Due to affiliates		34.2	10.5
Intercompany note payable		120
Total liabilities		318.6	52.6
Total shareholders' equity		1,891.3	1,792.7
Total liabilities and shareholders' equity		2,209.9	1,845.3
Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) [Member]
Assets
Investments		2,893.8	2,834.2
Cash		46.2	53.7		82.9	88.8
Accrued investment income		17.2	16
Premiums receivable		214	204.9
Reinsurance recoverables		1,386.5	1,348.4
Goodwill and other intangible assets, net		126.1	127.1
Deferred acquisition costs, net		74.2	63.5
Ceded unearned premiums		182	168.9
Other assets		171.4	168
Intercompany note receivable		49.6	50.2
Investments in subsidiaries		0	0
Total assets		5,161	5,034.9
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses		2,354.7	2,322.4
Unearned premiums		618.4	580
Funds held and ceded reinsurance payable, net		736.3	750.2
Long-term debt		284.4	284.4
Current income taxes payable, net		11.5	8.5
Deferred tax liabilities, net		29.8	17.6
Accrued underwriting expenses and other liabilities		80.5	92
Due to affiliates		5.1	1.8
Intercompany note payable		0
Total liabilities		4,120.7	4,056.9
Total shareholders' equity		1,040.3	978
Total liabilities and shareholders' equity		5,161	5,034.9
Other Subsidiaries and Eliminations [Member]
Assets
Investments	[2]	1,729.1	1,487.9
Cash	[2]	168.3	32.3		37.7	32.9
Accrued investment income	[2]	5.8	4.7
Premiums receivable	[2]	458.6	258.9
Reinsurance recoverables	[2]	133.1	37.2
Goodwill and other intangible assets, net	[2]	91.5	92.8
Deferred acquisition costs, net	[2]	88.6	75.6
Ceded unearned premiums	[2]	254.6	133.9
Other assets	[2]	146.2	86.1
Intercompany note receivable	[2]	70.4	(50.2)
Investments in subsidiaries	[2]	0	0
Total assets	[2]	3,146.2	2,159.2
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses	[2]	1,278.1	1,028.4
Unearned premiums	[2]	557.8	390
Funds held and ceded reinsurance payable, net	[2]	8.6	(206.5)
Long-term debt	[2]	140.6	54.8
Current income taxes payable, net	[2]	1.9	(0.4)
Deferred tax liabilities, net	[2]	8.4	6.5
Accrued underwriting expenses and other liabilities	[2]	74	42.3
Due to affiliates	[2]	(5.1)	(1.8)
Intercompany note payable	[2]	0
Total liabilities	[2]	2,064.3	1,313.3
Total shareholders' equity	[2]	1,081.9	845.9
Total liabilities and shareholders' equity	[2]	3,146.2	2,159.2
Consolidating Adjustments [Member]
Assets
Investments	[3]	0	0
Cash	[3]	0	0		$ 0	$ 0
Accrued investment income	[3]	0	0
Premiums receivable	[3]	0	0
Reinsurance recoverables	[3]	0	0
Goodwill and other intangible assets, net	[3]	0	0
Deferred acquisition costs, net	[3]	0	0
Ceded unearned premiums	[3]	0	0
Other assets	[3]	0	0
Intercompany note receivable	[3]	(120)	0
Investments in subsidiaries	[3]	(2,156.4)	(1,834.4)
Total assets	[3]	(2,276.4)	(1,834.4)
Liabilities and Shareholders' Equity
Reserves for losses and loss adjustment expenses	[3]	0	0
Unearned premiums	[3]	0	0
Funds held and ceded reinsurance payable, net	[3]	0	0
Long-term debt	[3]	0	0
Current income taxes payable, net	[3]	0	0
Deferred tax liabilities, net	[3]	0	0
Accrued underwriting expenses and other liabilities	[3]	0	0
Due to affiliates	[3]	(34.2)	(10.5)
Intercompany note payable	[3]	(120)
Total liabilities	[3]	(154.2)	(10.5)
Total shareholders' equity	[3]	(2,122.2)	(1,823.9)
Total liabilities and shareholders' equity	[3]	$ (2,276.4)	$ (1,834.4)
[1]	Derived from audited consolidated financial statements.
[2]	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations.
[3]	Includes all Argo Group parent company eliminations.

Senior Unsecured Fixed Rate N99

Senior Unsecured Fixed Rate Notes - Condensed Consolidating Statement of Income (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Premiums and other revenue:
Earned premiums		$ 399.1	$ 344.9	$ 778.5	$ 689.8
Net investment (expense) income		43.6	35.7	74.1	56.9
Fee and other income		3.8	5.8	7.4	12.6
Net realized investment and other gains (losses)		4.5	(2.1)	19.1	(4.9)
Total revenue		451	384.3	879.1	754.4
Expenses:
Losses and loss adjustment expenses		230.6	196.6	453.1	388.2
Underwriting, acquisition and insurance expenses		154.7	133	308.3	265.6
Interest expense		7	4.9	12.9	9.7
Fee and other expense		3.3	5.7	7.4	12.2
Foreign currency exchange (gains) loss		4.6	4.5	3.9	6
Total expenses		400.2	344.7	785.6	681.7
Income before income taxes		50.8	39.6	93.5	72.7
Provision for income taxes		4.8	8.7	10.8	14.1
Net (loss) income before equity in earnings of subsidiaries		46	30.9	82.7	58.6
Equity in undistributed earnings of subsidiaries		0	0	0	0
Net income		46	30.9	82.7	58.6
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]
Premiums and other revenue:
Earned premiums		0	0	0	0
Net investment (expense) income		(0.4)	(0.5)	(2.1)	(1.1)
Fee and other income		0	0	0	0
Net realized investment and other gains (losses)		0	0.2	0.5	0.2
Total revenue		(0.4)	(0.3)	(1.6)	(0.9)
Expenses:
Losses and loss adjustment expenses		0	0	0	0
Underwriting, acquisition and insurance expenses		3.8	1.1	12.2	6.3
Interest expense		1.1	0.4	1.4	0.7
Fee and other expense		0	0	0	0
Foreign currency exchange (gains) loss		0	0	0	0
Total expenses		4.9	1.5	13.6	7
Income before income taxes		(5.3)	(1.8)	(15.2)	(7.9)
Provision for income taxes		0	0	0	0
Net (loss) income before equity in earnings of subsidiaries		(5.3)	(1.8)	(15.2)	(7.9)
Equity in undistributed earnings of subsidiaries		51.3	32.7	97.9	66.5
Net income		46	30.9	82.7	58.6
Argo Group US, Inc. and Subsidiaries (Subsidiary Issuer) [Member]
Premiums and other revenue:
Earned premiums		135.5	120.2	266.4	240.1
Net investment (expense) income		29.3	27.5	48.2	40.1
Fee and other income		2.9	4.2	5.7	9.4
Net realized investment and other gains (losses)		5.2	1.9	19	13.1
Total revenue		172.9	153.8	339.3	302.7
Expenses:
Losses and loss adjustment expenses		72.5	69.1	148.6	137.4
Underwriting, acquisition and insurance expenses		58.5	49	116.7	96.6
Interest expense		4.2	3.9	8.5	7.8
Fee and other expense		3.2	5	6.6	11.2
Foreign currency exchange (gains) loss		(0.1)	(0.1)	0	(0.1)
Total expenses		138.3	126.9	280.4	252.9
Income before income taxes		34.6	26.9	58.9	49.8
Provision for income taxes		8.1	8.3	14.5	13.7
Net (loss) income before equity in earnings of subsidiaries		26.5	18.6	44.4	36.1
Equity in undistributed earnings of subsidiaries		0	0	0	0
Net income		26.5	18.6	44.4	36.1
Other Subsidiaries and Eliminations [Member]
Premiums and other revenue:
Earned premiums	[1]	263.6	224.7	512.1	449.7
Net investment (expense) income	[1]	14.7	8.7	28	17.9
Fee and other income	[1]	0.9	1.6	1.7	3.2
Net realized investment and other gains (losses)	[1]	(0.7)	(4.2)	(0.4)	(18.2)
Total revenue	[1]	278.5	230.8	541.4	452.6
Expenses:
Losses and loss adjustment expenses	[1]	158.1	127.5	304.5	250.8
Underwriting, acquisition and insurance expenses	[1]	92.4	82.9	179.4	162.7
Interest expense	[1]	1.7	0.6	3	1.2
Fee and other expense	[1]	0.1	0.7	0.8	1
Foreign currency exchange (gains) loss	[1]	4.7	4.6	3.9	6.1
Total expenses	[1]	257	216.3	491.6	421.8
Income before income taxes	[1]	21.5	14.5	49.8	30.8
Provision for income taxes	[1]	(3.3)	0.4	(3.7)	0.4
Net (loss) income before equity in earnings of subsidiaries	[1]	24.8	14.1	53.5	30.4
Equity in undistributed earnings of subsidiaries	[1]	0	0	0	0
Net income	[1]	24.8	14.1	53.5	30.4
Consolidating Adjustments [Member]
Premiums and other revenue:
Earned premiums	[2]	0	0	0	0
Net investment (expense) income	[2]	0	0	0	0
Fee and other income	[2]	0	0	0	0
Net realized investment and other gains (losses)	[2]	0	0	0	0
Total revenue	[2]	0	0	0	0
Expenses:
Losses and loss adjustment expenses	[2]	0	0	0	0
Underwriting, acquisition and insurance expenses	[2]	0	0	0	0
Interest expense	[2]	0	0	0	0
Fee and other expense	[2]	0	0	0	0
Foreign currency exchange (gains) loss	[2]	0	0	0	0
Total expenses	[2]	0	0	0	0
Income before income taxes	[2]	0	0	0	0
Provision for income taxes	[2]	0	0	0	0
Net (loss) income before equity in earnings of subsidiaries	[2]	0	0	0	0
Equity in undistributed earnings of subsidiaries	[2]	(51.3)	(32.7)	(97.9)	(66.5)
Net income	[2]	$ (51.3)	$ (32.7)	$ (97.9)	$ (66.5)
[1]	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations.
[2]	Includes all Argo Group parent company eliminations.

Senior Unsecured Fixed Rate 100

Senior Unsecured Fixed Rate Notes - Condensed Consolidating Statement of Cash Flows (Detail) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016
Condensed Financial Statements, Captions [Line Items]
Net cash flows from (used in) operating activities		$ 37.3		$ 31.6
Cash flows from investing activities:
Proceeds from sales of investments		958.4		630.5
Maturities and mandatory calls of fixed maturity investments		335.1		673.3
Purchases of investments		(1,466)		(1,255.7)
Change in short-term investments and foreign regulatory deposits		300.4		(11)
Settlements of foreign currency exchange forward contracts		0.5		6.8
Acquisition of subsidiaries, net of cash		(105.2)		0
Issuance of intercompany note, net		0
Purchases of fixed assets and other, net		(37.7)		(23.6)
Cash (used in) provided by investing activities		(14.5)		20.3
Cash flows from financing activities:
Additional long-term borrowings		125		0
Borrowing under intercompany note, net		0
Activity under stock incentive plans		0.5		0.2
Repurchase of Company's common shares		(2.8)		(40)
Payment of cash dividends to common shareholders		(16.6)		(13.1)
Cash provided by (used in) financing activities		106.1		(52.9)
Effect of exchange rate changes on cash		(0.4)		(0.1)
Change in cash		128.5		(1.1)
Cash, beginning of year		86	[1]	121.7
Cash, end of period		214.5		120.6
Argo Group International Holdings, Ltd (Parent Guarantor) [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash flows from (used in) operating activities		5.3		14.7
Cash flows from investing activities:
Proceeds from sales of investments		0		0
Maturities and mandatory calls of fixed maturity investments		0		0
Purchases of investments		0		0
Change in short-term investments and foreign regulatory deposits		0.4		(1.8)
Settlements of foreign currency exchange forward contracts		0.8		0
Acquisition of subsidiaries, net of cash		(235.3)
Issuance of intercompany note, net		0
Purchases of fixed assets and other, net		(0.1)		0
Cash (used in) provided by investing activities		(234.2)		(1.8)
Cash flows from financing activities:
Additional long-term borrowings		125
Borrowing under intercompany note, net		120
Activity under stock incentive plans		0.5		0.2
Repurchase of Company's common shares		0		0
Payment of cash dividends to common shareholders		(16.6)		(13.1)
Cash provided by (used in) financing activities		228.9		(12.9)
Effect of exchange rate changes on cash		0		0
Change in cash		0		0
Cash, beginning of year		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 (used in) operating activities		(8)		(9.2)
Cash flows from investing activities:
Proceeds from sales of investments		514.4		490
Maturities and mandatory calls of fixed maturity investments		240.6		296.9
Purchases of investments		(811)		(720.1)
Change in short-term investments and foreign regulatory deposits		72		(12.3)
Settlements of foreign currency exchange forward contracts		0		0
Acquisition of subsidiaries, net of cash		0
Issuance of intercompany note, net		0
Purchases of fixed assets and other, net		(12.7)		(11.2)
Cash (used in) provided by investing activities		3.3		43.3
Cash flows from financing activities:
Additional long-term borrowings		0
Borrowing under intercompany note, net		0
Activity under stock incentive plans		0		0
Repurchase of Company's common shares		(2.8)		(40)
Payment of cash dividends to common shareholders		0		0
Cash provided by (used in) financing activities		(2.8)		(40)
Effect of exchange rate changes on cash		0		0
Change in cash		(7.5)		(5.9)
Cash, beginning of year		53.7		88.8
Cash, end of period		46.2		82.9
Other Subsidiaries and Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash flows from (used in) operating activities	[2]	40		26.1
Cash flows from investing activities:
Proceeds from sales of investments	[2]	444		140.5
Maturities and mandatory calls of fixed maturity investments	[2]	94.5		376.4
Purchases of investments	[2]	(655)		(535.6)
Change in short-term investments and foreign regulatory deposits	[2]	228		3.1
Settlements of foreign currency exchange forward contracts	[2]	(0.3)		6.8
Acquisition of subsidiaries, net of cash	[2]	130.1
Issuance of intercompany note, net	[2]	(120)
Purchases of fixed assets and other, net	[2]	(24.9)		(12.4)
Cash (used in) provided by investing activities	[2]	96.4		(21.2)
Cash flows from financing activities:
Additional long-term borrowings	[2]	0
Borrowing under intercompany note, net	[2]	0
Activity under stock incentive plans	[2]	0		0
Repurchase of Company's common shares	[2]	0		0
Payment of cash dividends to common shareholders	[2]	0		0
Cash provided by (used in) financing activities	[2]	0		0
Effect of exchange rate changes on cash	[2]	(0.4)		(0.1)
Change in cash	[2]	136		4.8
Cash, beginning of year	[2]	32.3		32.9
Cash, end of period	[2]	168.3		37.7
Consolidating Adjustments [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash flows from (used in) operating activities	[3]	0		0
Cash flows from investing activities:
Proceeds from sales of investments	[3]	0		0
Maturities and mandatory calls of fixed maturity investments	[3]	0		0
Purchases of investments	[3]	0		0
Change in short-term investments and foreign regulatory deposits	[3]	0		0
Settlements of foreign currency exchange forward contracts	[3]	0		0
Acquisition of subsidiaries, net of cash	[3]	0
Issuance of intercompany note, net	[3]	120
Purchases of fixed assets and other, net	[3]	0		0
Cash (used in) provided by investing activities	[3]	120		0
Cash flows from financing activities:
Additional long-term borrowings	[3]	0
Borrowing under intercompany note, net	[3]	(120)
Activity under stock incentive plans	[3]	0		0
Repurchase of Company's common shares	[3]	0		0
Payment of cash dividends to common shareholders	[3]	0		0
Cash provided by (used in) financing activities	[3]	(120)		0
Effect of exchange rate changes on cash	[3]	0		0
Change in cash	[3]	0		0
Cash, beginning of year	[3]	0		0
Cash, end of period	[3]	$ 0		$ 0
[1]	Derived from audited consolidated financial statements.
[2]	Includes all other subsidiaries of Argo Group International Holdings, Ltd. and all intercompany eliminations.
[3]	Includes all Argo Group parent company eliminations.