OneBeacon Insurance 10-Q 2 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2016	Apr. 28, 2016
Entity Registrant Name	OneBeacon Insurance Group, Ltd.
Entity Central Index Key	1,369,817
Document Type	10-Q
Document Period End Date	Mar. 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Class A common
Entity Common Stock, Shares Outstanding		22,589,822
Class B common
Entity Common Stock, Shares Outstanding		71,754,738

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Investment Securities:
Fixed maturity investments, at fair value (amortized cost: $2,011.5 in 2016 and $2,078.3 in 2015)	$ 2,028.7	$ 2,080.5
Short-term investments, at amortized cost (which approximates fair value)	119.7	69.2
Common equity securities, at fair value (amortized cost - $262.5 in 2016 and $295.0 in 2015)	275.9	298.7
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	137.8	143
Total investments	2,562.1	2,591.4
Cash	108.8	95.2
Reinsurance recoverables	167	193.5
Premiums receivable	230.4	219
Deferred acquisition costs	102	100.7
Ceded unearned premiums	36.3	29.5
Net deferred tax asset	134.1	140.2
Investment income accrued	9.4	10.1
Accounts receivable on unsettled investment sales	4.5	30.5
Other assets	174.4	192.5
Total assets	3,529	3,602.6
Liabilities
Unpaid loss and loss adjustment expense reserves	1,343.8	1,389.8
Unearned premiums	568.6	560.3
Funds held under insurance contracts	134.9	137.7
Debt	272.9	272.9
Accounts payable on unsettled investment purchases	1.5	0
Other liabilities	187.5	237.4
Total liabilities	2,509.2	2,598.1
OneBeacon's common shareholders' equity
Preference shares (Par value $0.01; 80,000,000 authorized shares; none issued or outstanding)	0	0
Common shares and paid-in surplus (Class A: par value $0.01; 200,000,000 authorized shares; 22,589,822 and 23,334,502 issued and outstanding)(Class B: par value $0.01; 200,000,000 authorized shares; 71,754,738 issued and outstanding for both periods)	1,011.1	1,022
Retained earnings	10.7	(15.9)
Accumulated other comprehensive loss, after tax	(5.2)	(5.2)
Total OneBeacon's common shareholders' equity	1,016.6	1,000.9
Total noncontrolling interests, after tax	3.2	3.6
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,019.8	1,004.5
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	$ 3,529	$ 3,602.6

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Common shares, issued shares (in shares)	94,344,560	95,089,240
Common shares, outstanding shares (in shares)	94,344,560	95,089,240
Preferred shares, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred shares, authorized shares (in shares)	80,000,000	80,000,000
Preferred shares, issued shares (in shares)	0	0
Preferred shares, outstanding shares (in shares)	0	0
Trading Securities, Debt, Amortized Cost	$ 2,011.5	$ 2,078.3
Trading Securities, Short-term Investments, Amortized Cost	119.7	69.2
Trading Securities, Equity, Cost	262.5	295
Other Investments and Securities, at Cost	$ 132.6	$ 135.6
Class A common
Common shares, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares, authorized shares (in shares)	200,000,000	200,000,000
Common shares, issued shares (in shares)	22,589,822	23,334,502
Common shares, outstanding shares (in shares)	22,589,822	23,334,502
Class B common
Common shares, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares, authorized shares (in shares)	200,000,000	200,000,000
Common shares, issued shares (in shares)	71,754,738	71,754,738
Common shares, outstanding shares (in shares)	71,754,738	71,754,738

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues
Earned premiums	$ 278.6	$ 286.6
Net investment income	14.4	10.5
Net realized and change in unrealized investment gains	16.6	14.2
Net other revenues (expenses)	0.9	(3.1)
Total revenues	310.5	308.2
Expenses
Loss and loss adjustment expenses	158.8	165.9
Policy acquisition expenses	51	51
Other underwriting expenses	55.3	55.9
General and administrative expenses	3.9	4.1
Interest expense	3.3	3.2
Total expenses	272.3	280.1
Pre-tax income from continuing operations	38.2	28.1
Income tax benefit (expense)	8.7	(3.4)
Net income from continuing operations	46.9	24.7
Loss from discontinued operations, net of tax	0	(0.1)
Net income including noncontrolling interests	46.9	24.6
Less: Net income attributable to noncontrolling interests	(0.5)	(0.5)
Net income attributable to OneBeacon's common shareholders	46.4	24.1
Other comprehensive income, net of tax	0	0.2
Comprehensive income attributable to OneBeacon's common shareholders	$ 46.4	$ 24.3
Net income attributable to OneBeacon's common shareholders per share	$ 0.49	$ 0.25
Dividends declared and paid per OneBeacon's common share	$ 0.21	$ 0.21

CONSOLIDATED STATEMENTS OF COMM

CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common shares and paid-in surplus	Retained earnings	Accum. other comprehensive loss	Total OneBeacon common shareholders' equity	Noncontrolling interests, after tax	Common equity securities
Increase (Decrease) in Stockholders' Equity
Common shares, outstanding shares (in shares)							95,296,387
Balances at Dec. 31, 2014	$ 1,049.3	$ 1,023.7	$ 27.3	$ (5.2)	$ 1,045.8	$ 3.5
Increase (Decrease) in Stockholders' Equity
Net income	24.6	0	24.1	0	24.1	0.5
Net change in benefit plan assets and obligations, net of tax	0.2	0	0	0.2	0.2	0
Total comprehensive income	24.8	0	24.1	0.2	24.3	0.5
Amortization of restricted share awards	0.6	0.6	0	0	0.6	0
Issuance of common shares (in shares)							75,950
Issuance of common shares	0.1	0	0	0	0	0.1
Repurchase and retirement of common shares (in shares)							(113,551)
Repurchase and retirement of common shares	(1.6)	(1.6)	0	0	(1.6)	0
Dividends	(21.1)	0	(20)	0	(20)	(1.1)
Balances at Mar. 31, 2015	$ 1,052.1	1,022.7	31.4	(5)	1,049.1	3
Increase (Decrease) in Stockholders' Equity
Common shares, outstanding shares (in shares)							95,258,786
Common shares, outstanding shares (in shares)	95,089,240						95,089,240
Balances at Dec. 31, 2015	$ 1,004.5	1,022	(15.9)	(5.2)	1,000.9	3.6
Increase (Decrease) in Stockholders' Equity
Net income	46.9	0	46.4	0	46.4	0.5
Net change in benefit plan assets and obligations, net of tax	0	0	0	0	0	0
Total comprehensive income	46.9	0	46.4	0	46.4	0.5
Amortization of restricted share awards	0.6	0.6	0	0	0.6	0
Issuance of common shares (in shares)							170,650
Issuance of common shares	0.1	0	0	0	0	0.1
Repurchase and retirement of common shares (in shares)							(915,330)
Repurchase and retirement of common shares	(11.5)	(11.5)	0	0	(11.5)	0
Dividends	(20.8)	0	(19.8)	0	(19.8)	(1)
Balances at Mar. 31, 2016	$ 1,019.8	$ 1,011.1	$ 10.7	$ (5.2)	$ 1,016.6	$ 3.2
Increase (Decrease) in Stockholders' Equity
Common shares, outstanding shares (in shares)	94,344,560						94,344,560

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operations:
Net income including noncontrolling interests	$ 46.9	$ 24.6
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:
Net loss from discontinued operations	0	0.1
Net realized and change in unrealized investment gains	(16.6)	(14.2)
Net adjustment to gain on sale of business	0	3.7
Deferred income tax expense	6.7	0.5
Other operating items:
Net change in loss and LAE reserves	(46)	(38.2)
Net change in unearned premiums	8.3	2
Net change in ceded unearned premium	(6.8)	(1.4)
Net change in premiums receivable	(11.4)	(16.6)
Net change in reinsurance recoverables on paid and unpaid losses	26.5	14
Net change in funds held under reinsurance contracts	0	19.7
Net change in funds held under insurance contracts	(2.8)	12
Net change in other assets and liabilities	(28.3)	17.2
Net cash provided from (used for) operations—continuing operations	(23.5)	23.4
Net cash used for operations—discontinued operations	0	(0.1)
Net cash provided from (used for) operations	(23.5)	23.3
Cash flows from investing activities:
Net maturities, purchases and sales of short-term investments	(50.5)	8
Maturities of fixed maturity investments	110.1	32.9
Sales of fixed maturity investments	161.9	177.6
Sales of common equity securities	103.2	39.6
Return of capital and distributions of other investments	3	3.7
Purchases of fixed maturity investments	(209.8)	(273)
Purchases of common equity securities	(75.4)	(26.2)
Contributions for other investments	(0.3)	(1.9)
Net change in unsettled investment purchases and sales	27.6	40.3
Net acquisitions of property and equipment	(0.9)	(0.4)
Net cash used for investing activities	68.9	0.6
Cash flows from financing activities:
Cash dividends paid to common shareholders	(19.8)	(20)
Repurchases and retirements of common stock	(11.5)	(1.6)
Payments on capital lease obligation	(0.5)	(1.4)
Net cash used for financing activities	(31.8)	(23)
Net increase (decrease) in cash during period	13.6	0.9
Cash balance at beginning of period	95.2	87
Cash balance at end of period	$ 108.8	$ 87.9

Nature of Operations and Summar

Nature of Operations and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
Nature of Operations and Summary of Significant Accounting Policies	Nature of Operations and Summary of Significant Accounting Policies Basis of presentation These interim consolidated financial statements include the accounts of OneBeacon Insurance Group, Ltd. (the "Company" or the "Registrant") and its subsidiaries (collectively, "OneBeacon") and have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP"). The Company is an exempted Bermuda limited liability company with U.S.-based underwriting operating companies that are property and casualty insurance writers and a Bermuda-based reinsurance company, Split Rock Insurance, Ltd. ("Split Rock"). OneBeacon offers a wide range of specialty insurance products and services primarily through independent agencies, regional and national brokers, wholesalers and managing general agencies. OneBeacon is 76.1% owned by White Mountains Insurance Group, Ltd. ("White Mountains"), a holding company whose businesses provide property and casualty insurance, reinsurance and certain other products. The Company's headquarters are located at 14 Wesley Street, 5th Floor, Hamilton HM 11, Bermuda. The Company's U.S. corporate headquarters are located at 605 North Highway 169, Plymouth, Minnesota 55441 and its registered office is located at Clarendon House, 2 Church Street, Hamilton HM 11, Bermuda. On December 23, 2014, OneBeacon completed the sale of its run-off business to a subsidiary of Armour Group Holdings Limited (“Armour”). See Note 2—"Acquisitions and Dispositions" and Note 15—"Discontinued Operations." The run-off business included the results of OneBeacon's non-specialty commercial lines business as well as the vast majority of asbestos and environmental reserves (the “Runoff Business,” the sale of which is referred to as the “Runoff Transaction”). The Runoff Business has been presented as discontinued operations in the consolidated statements of operations and in the consolidated statements of cash flows for the three months ended March 31, 2016 and 2015. OneBeacon's reportable segments are Specialty Products, Specialty Industries and Investing, Financing and Corporate. The Specialty Products segment is comprised of ten active underwriting operating segments, representing an aggregation based on those that offer distinct products and tailored coverages and services to a broad customer base across the United States. The Specialty Industries segment is comprised of six active underwriting operating segments, representing an aggregation based on those that focus on solving the unique needs of a particular customer or industry group. The Investing, Financing and Corporate segment includes the investing and financing activities for OneBeacon on a consolidated basis, and certain other activities conducted through the Company and its intermediate subsidiaries. All significant intercompany transactions have been eliminated in consolidation. These interim financial statements include all adjustments considered necessary by management to fairly state the financial position, results of operations and cash flows of OneBeacon. These interim financial statements may not be indicative of financial results for the full year and should be read in conjunction with the Company’s 2015 Annual Report on Form 10-K. The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Refer to the Company’s 2015 Annual Report on Form 10-K for a complete discussion regarding OneBeacon’s significant accounting policies. Certain amounts in the prior period financial statements have been reclassified to conform to the current presentation. Recently Adopted Changes in Accounting Principles Business Combinations - Measurement Period Adjustments Effective January 1, 2016, OneBeacon adopted ASU 2015-16, Simplifying the Accounting for Measurement-Period Adjustments, which requires adjustments to provisional amounts recorded in connection with a business combination that are identified during the measurement period are to be recorded in the reporting period in which the adjustment amounts are determined, rather than as retroactive adjustments to prior periods. OneBeacon has not recognized any adjustments to estimated purchase accounting amounts for the year to date period ended March 31, 2016 and accordingly, there was no effect to OneBeacon's financial statements upon adoption. Fair Value Measurements Effective January 1, 2016, OneBeacon adopted ASU 2015-07, Fair Value Measurement - Disclosures for Investments in Certain Entities that Calculate Net Asset Value per Share (or Its Equivalent) (ASC 820) which eliminates the requirement to disclose the fair value hierarchy level for investments for which fair value is measured at net asset value ("NAV") using the practical expedient in ASC 820. OneBeacon measures the fair value of its investments in hedge funds and private equity funds using this practical expedient. Upon adoption, these fair value measurements are no longer classified within the fair value hierarchy. Prior year amounts have been modified to conform to the current year's disclosures. Amendments to Consolidation Analysis On January 1, 2016, OneBeacon adopted ASU 2015-02, Amendments to the Consolidation Analysis (ASC 810) which amends the guidance for determining whether an entity is a variable interest entity (“VIE”). ASU 2015-02 eliminates the separate consolidation guidance for limited partnerships and with it, the presumption that a general partner should consolidate a limited partnership. In addition, ASU 2015-02 changes the guidance for determining if fee arrangements qualify as variable interests and the effect fee arrangements have on the determination of the primary beneficiary. Adoption of ASU 2015-02 did not affect the consolidation analysis for any of OneBeacon's investments. Share-Based Compensation Awards On January 1, 2016, OneBeacon adopted ASU 2014-12, Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period (ASC 718) . The new guidance requires that a performance target that affects vesting and that can be achieved after the requisite service period be treated as a performance condition. Compensation cost is to be recognized in the period when it becomes probable the performance target will be achieved in an amount equal to the compensation cost attributable to the periods for which service has been rendered. There was no effect to OneBeacon's financial statements upon adoption. Debt Issuance Costs Effective January 1, 2016, OneBeacon adopted ASU 2015-03, Imputation of Interest (ASC 835) which requires debt issuance costs to be presented as a deduction from the carrying amount of the related debt, consistent with the treatment required for debt discounts. The new guidance requires amortization of debt issuance costs to be classified within interest expense and also requires disclosure of the debt's effective interest rate. OneBeacon has applied the guidance retrospectively and as a result has reclassified $1.9 million of debt issuance costs from other assets, reflecting these amounts as reduction from the related debt and has modified its disclosures to include the required effective interest rate on its debt. Adoption of ASU 2015-03 did not have a material impact on OneBeacon's financial position, results of operations, or cash flows. In addition, effective January 1, 2016, OneBeacon adopted ASU 2015-15, Imputation of Interest (ASC 835), which addresses the presentation and subsequent measurement of debt issuance costs related to line-of-credit arrangements. Adoption of ASU 2015-15 did not have a significant effect on OneBeacon's financial position, results of operations, cash flows, presentation or disclosures. Recently Issued Accounting Pronouncements Stock Compensation On March 30, 2016, the Board issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (ASC 718) which is intended to simplify certain aspects of the accounting for share-based compensation. The new guidance provides an accounting policy election to account for forfeitures by either applying an assumption, as required under existing guidance, or by recognizing forfeitures when they actually occur. The new guidance is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods with early adoption permitted. OneBeacon does not expect a significant effect upon adoption. Leases On February 25, 2016, the FASB issued ASU 2016-02, Leases (ASC 842). The new guidance requires lessees to recognize lease assets and liabilities on the balance sheet for both operating and financing leases, with the exception of leases with an original term of 12 months or less. Under existing guidance recognition of lease assets and liabilities is not required for operating leases. The lease assets and liabilities to be recognized are both measured initially based on the present value of the lease payments. Under the new guidance, a sale-leaseback transaction must meet the recognition criteria under ASC 606, Revenues in order to be accounted for as sale. The new guidance is effective for OneBeacon for years beginning after December 15, 2018, including interim periods therein. OneBeacon is evaluating the expected impact of this new guidance and available adoption methods. Financial Instruments - Recognition and Measurement On January 5, 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (ASC 825-10). The new guidance requires all equity securities with readily determinable fair values to be measured at fair value with changes therein recognized through current period earnings. In addition, the new ASU simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment, and for impaired equity security investments to be measured at fair value. ASU 2016-01 is effective for fiscal years beginning after December 15, 2017, with early adoption permitted. OneBeacon has taken the fair value election for its portfolio of equity security investments and accordingly, does not expect the adoption of ASU 2016-01 to have a significant impact on its financial statements. Insurance Contracts In May 2015, the FASB issued ASU 2015-09, Disclosures about Short Duration Contracts (ASC 944) which requires expanded footnote disclosures about loss and loss adjustment expense ("LAE") reserves. Under the new guidance, some disclosures currently presented outside of OneBeacon’s financial statements, such as loss development tables and a reconciliation of loss development data to the loss and LAE reserves reflected on the balance sheet, will become part of the financial statement footnotes. In addition, the loss development tables required to be presented under the new ASU must be presented on a disaggregated basis by accident year rather than by reporting year as currently presented. Some of the expanded disclosures are new requirements, such as the disclosure of reserves for losses incurred but not reported ("IBNR") plus expected development on reported claims, which must be presented by accident year on a disaggregated basis. The new guidance also requires new disclosures about claim frequency data together with descriptions of the approach used to measure that data. Qualitative descriptions of methodologies and assumptions used to develop IBNR estimates must be presented together with the disaggregated amounts of IBNR to which they relate, along with a discussion of any significant changes in methodology and assumptions and the related effect upon the loss reserves. The new guidance will be effective for annual periods beginning after December 15, 2015 and interim periods within annual periods beginning after December 15, 2016 with retrospective restatement of prior periods required. OneBeacon will modify its financial statement footnote disclosures to conform to the requirements of ASU 2015-09 upon adoption, including revisions to prior year’s disclosures. Revenue Recognition In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (ASC 606) , which modifies the guidance for revenue recognition. The scope of the new ASU excludes insurance contracts but is applicable to certain fee arrangements, such as investment management fees. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (ASC 606), which delayed the effective date of ASU 2014-09 by one year. As a result, the standard is effective for annual and interim periods beginning after December 15, 2017. The Company is in the process of evaluating the new guidance and has not yet determined the potential effect of adoption on its financial position, results of operations, or cash flows.

Acqusitions and Dispositions

Acqusitions and Dispositions	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Acquisitions and Dispositions	Acquisitions and Dispositions Crop Business On July 31, 2015, Monsanto Company sold Climate Crop Insurance Agency ("CCIA"), the third party agency with which OneBeacon previously had an exclusive managing general agency agreement, to an affiliate of AmTrust Financial Services, Inc. ("AmTrust"). As a result of the sale, the Company exited the multiple peril crop insurance ("MPCI") business and its related crop-hail business (collectively, "Crop Business"). As a result of the transaction, OneBeacon and CCIA agreed to an early termination of the existing five year agreement. In connection with the termination of the agreement, OneBeacon received a payment of $3.0 million . Also related to the transaction, OneBeacon withdrew its 2016 Plan of Operations, which previously authorized it to write MPCI for the 2016 Reinsurance Year, and affiliates of AmTrust agreed to reinsure the Company’s remaining net Crop Business exposure for the 2015 Reinsurance Year under a related 100% quota share reinsurance agreement which, coupled with other transfer and assignment agreements as well as communications with policyholders and agents, had the effect of assumption reinsurance. As a result of this transaction, the Company has no material net exposure related to the Crop Business. Runoff Business As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies," on December 23, 2014, OneBeacon completed the sale of its Runoff Business to Armour. OneBeacon provided financing in the form of surplus notes issued by Bedivere Insurance Company ("Bedivere"), one of the legal entities transferred as part of the transaction, having a par value of $101.0 million , which had a fair value of $64.9 million on the date of sale. See Note 15—"Discontinued Operations" for further information. Essentia Insurance Company Effective January 1, 2013, OneBeacon completed the sale of Essentia Insurance Company ("Essentia"), which wrote the collector cars and boats business, to Markel Corporation. During the first quarter of 2015, the Company recognized in net other revenues (expenses) a $3.7 million negative adjustment to the pre-tax gain on sale of Essentia in connection with an assessment from the Michigan Catastrophic Claims Association (MCCA) payable to Markel Corporation pursuant to the indemnification provisions in the stock purchase agreement governing the sale of Essentia. Except as described above, during the three months ended March 31, 2016 and 2015 , there were no significant acquisitions or dispositions.

Unpaid Loss and Loss Adjustment

Unpaid Loss and Loss Adjustment Expense (LAE) Reserves	3 Months Ended
	Mar. 31, 2016
Insurance Loss Reserves [Abstract]
Unpaid Loss and Loss Adjustment Expense (LAE) Reserves	Loss and LAE reserve summary The following table summarizes the loss and LAE reserve activities of OneBeacon's insurance subsidiaries for the three months ended March 31, 2016 and 2015 : Three months ended ($ in millions) 2016 2015 Gross beginning balance $ 1,389.8 $ 1,342.2 Less beginning reinsurance recoverables on unpaid losses (186.0 ) (161.6 ) Net beginning loss and LAE reserves 1,203.8 1,180.6 Loss and LAE incurred relating to: Current year losses 158.8 167.7 Prior year losses — (1.8 ) Total incurred loss and LAE 158.8 165.9 Loss and LAE paid relating to: Current year losses (22.0 ) (22.1 ) Prior year losses (147.2 ) (162.0 ) Total loss and LAE payments (169.2 ) (184.1 ) Net ending loss and LAE reserves 1,193.4 1,162.4 Plus ending reinsurance recoverables on unpaid losses 150.4 141.6 Gross ending loss and LAE reserves $ 1,343.8 $ 1,304.0 Loss and LAE development Loss and LAE development—2016 During the three months ended March 31, 2016 , OneBeacon experienced no net loss and LAE reserve development on prior accident year reserves, as favorable development from several businesses, most notably Technology and Accident was offset by unfavorable development primarily in Healthcare due to large claims and heavy loss activity. Loss and LAE development—2015 During the three months ended March 31, 2015 , OneBeacon experienced $1.8 million of net favorable loss and LAE reserve development on prior accident year reserves, primarily attributable to favorable development from Crop resulting from the 2014 crop year and favorable development in several other businesses, most notably from Ocean Marine , Technology , Government Risks , Surety and Specialty Property . This favorable development was mostly offset by unfavorable development in Entertainment driven by several large and small to mid-sized claims and by losses within the Inland Marine business resulting from a few large claims.

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2016
Reinsurance Disclosures [Abstract]
Reinsurance	In the normal course of business, OneBeacon's insurance subsidiaries seek to limit losses that may arise from catastrophes or other events by reinsuring with third-party reinsurers. OneBeacon remains liable for risks reinsured even if the reinsurer does not honor its obligations under reinsurance contracts. Reinsurance Treaties The Company's reinsurance coverage is discussed in Note 4—"Reinsurance" in the Company's 2015 Annual Report on Form 10-K. Except as discussed below, there have been no material changes to the Company's reinsurance coverage from that reported in the 2015 Annual Report on Form 10-K. The Company entered into a 50% quota share reinsurance agreement related to its Financial Institutions business. Reinsurance Recoverables As of March 31, 2016 , OneBeacon had reinsurance recoverables on paid losses of $16.6 million and reinsurance recoverables on unpaid losses of $150.4 million . As reinsurance contracts do not relieve OneBeacon of its obligations, collectibility of balances due from reinsurers is critical to OneBeacon's financial strength. The following table summarizes Standard & Poor's Financial Services, LLC ("Standard & Poor's") ratings for OneBeacon's reinsurers, excluding industry pools and associations, based upon reinsurance recoverable amounts on paid and unpaid losses and LAE: Balance at March 31, 2016 % of total Standard & Poor's Rating (1) : ($ in millions) AA $ 42.7 26 % A 98.2 59 % BBB, Not Rated and Other (2) 26.1 15 % Total reinsurance recoverables $ 167.0 100 % _______________________________________________________________________________ (1) Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB" (Adequate). (2) Includes reinsurance recoverable on unpaid losses from Bedivere of $19.4 million .

Investment Securities

Investment Securities	3 Months Ended
	Mar. 31, 2016
Schedule of Investments [Abstract]
Investment Securities	Investment Securities OneBeacon's invested assets are comprised of securities and other investments held for general investment purposes. Refer to the Company's 2015 Annual Report on Form 10-K for a complete discussion. OneBeacon classifies its portfolio of fixed maturity investments and common equity securities held for general investment purposes as trading securities. Trading securities are reported at fair value as of the balance sheet date as determined by quoted market prices when available. Realized and change in unrealized investment gains on trading securities are reported, on a pre-tax basis, in total revenues as net realized and change in unrealized investment gains. Short-term investments consist of money market funds, certificates of deposit and other securities which, at the time of purchase, mature or become available for use within one year. Short-term investments are carried at amortized cost, which approximates fair value. Other investments primarily include surplus notes, private equity funds and hedge funds. OneBeacon measures its investments in private equity funds and hedge funds at fair value with changes therein reported in total revenues as net realized and change in unrealized investment gains. Surplus notes provided in conjunction with the financing of the Runoff Transaction are measured at their estimated fair value based on discounted expected cash flows, with changes in fair value reported in total revenues as net realized and change in unrealized investment gains. Other investments also include an investment in a community reinvestment vehicle which is accounted for at fair value, with changes in fair value reported in total revenues as net realized and change in unrealized investment gains and a tax advantaged federal affordable housing development fund which is accounted for under the proportional amortization method. Prospector Partners, LLC (“Prospector”), was the primary manager of OneBeacon's publicly-traded common equity securities portfolio. The Prospector-managed separate accounts were liquidated during the second quarter of 2015, and a Prospector-managed hedge fund was redeemed. As the separate accounts were liquidated, OneBeacon reinvested the majority of the proceeds into exchange traded funds ("ETFs") that seek to provide investment results that, before expenses, generally correspond to the performance of the S&P 500, Russell 1000, and Russell 1000 Value indices. OneBeacon's net investment income is comprised primarily of interest income associated with fixed maturity investments and dividend income from its equity investments. Net investment income for the three months ended March 31, 2016 and 2015 consisted of the following: Three months ended ($ in millions) 2016 2015 Fixed maturity investments $ 12.1 $ 10.2 Common equity securities 1.0 1.6 Other investments (1) 2.5 0.1 Gross investment income 15.6 11.9 Less external investment expenses (1.2 ) (1.4 ) Net investment income, pre-tax $ 14.4 $ 10.5 _______________________________________________________________________________ (1) Includes an interest payment on the surplus notes of $2.4 million received in the three months ended March 31, 2016 . The composition of net realized investment gains (losses) consisted of the following: Three months ended ($ in millions) 2016 2015 Fixed maturity investments $ (1.4 ) $ 0.7 Common equity securities (4.7 ) 9.8 Other investments 0.2 (1.0 ) Net realized investment gains (losses), pre-tax $ (5.9 ) $ 9.5 The net changes in net unrealized gains for the three months ended March 31, 2016 and 2015 are as follows: Three months ended March 31, 2016 ($ in millions) Changes in net unrealized investment gains Changes in net foreign currency gains (losses) Total net changes in unrealized gains reflected in revenues Fixed maturity investments $ 15.0 $ — $ 15.0 Common equity securities 9.7 — 9.7 Other investments (2.2 ) — (2.2 ) Net change, pre-tax $ 22.5 $ — $ 22.5 Three months ended March 31, 2015 ($ in millions) Changes in net unrealized investment gains Changes in net foreign currency gains (losses) Total net changes in unrealized gains reflected in revenues Fixed maturity investments $ 6.6 $ — $ 6.6 Common equity securities (4.4 ) (0.1 ) (4.5 ) Other investments 2.6 — 2.6 Net change, pre-tax $ 4.8 $ (0.1 ) $ 4.7 The components of OneBeacon's ending net unrealized investment gains and losses, excluding the impact of net unrealized foreign currency translation gains and losses, on its investment portfolio as of March 31, 2016 and December 31, 2015 were as follows: ($ in millions) March 31, December 31, Investment securities: Gross unrealized investment gains $ 63.5 $ 46.5 Gross unrealized investment losses (27.7 ) (33.2 ) Total net unrealized investment gains, pre-tax 35.8 13.3 Income taxes (12.4 ) (6.5 ) Total net unrealized investment gains, after-tax $ 23.4 $ 6.8 The cost or amortized cost, gross unrealized pre-tax investment gains and losses, net foreign currency losses and carrying values of OneBeacon's fixed maturity investments as of March 31, 2016 and December 31, 2015 were as follows: March 31, 2016 ($ in millions) Cost or amortized cost Gross unrealized gains Gross unrealized losses Net unrealized foreign currency gains (losses) Carrying value U.S. Government and agency obligations $ 53.5 $ 0.1 $ — $ — $ 53.6 Debt securities issued by corporations 733.3 11.2 (0.9 ) — 743.6 Municipal obligations 67.6 1.8 (0.1 ) — 69.3 Mortgage and asset-backed securities 1,077.8 3.7 (3.7 ) — 1,077.8 Foreign government obligations 1.0 0.2 — — 1.2 Preferred stocks 78.3 4.9 — — 83.2 Total fixed maturity investments $ 2,011.5 $ 21.9 $ (4.7 ) $ — $ 2,028.7 December 31, 2015 ($ in millions) Cost or amortized cost Gross unrealized gains Gross unrealized losses Net unrealized foreign Carrying value U.S. Government and agency obligations $ 85.4 $ — $ (0.1 ) $ — $ 85.3 Debt securities issued by corporations 810.8 4.1 (4.5 ) — 810.4 Municipal obligations 67.7 1.5 (0.2 ) — 69.0 Mortgage and asset-backed securities 1,035.1 1.3 (4.5 ) — 1,031.9 Foreign government obligations 1.0 0.2 — — 1.2 Preferred stocks 78.3 4.4 — — 82.7 Total fixed maturity investments $ 2,078.3 $ 11.5 $ (9.3 ) $ — $ 2,080.5 The cost or amortized cost, gross unrealized pre-tax investment gains and losses, net unrealized pre-tax foreign currency losses and carrying values of common equity securities and other investments as of March 31, 2016 and December 31, 2015 were as follows: March 31, 2016 ($ in millions) Cost or amortized cost Gross unrealized gains Gross unrealized losses Net unrealized foreign Carrying value Common equity securities $ 262.5 $ 19.4 $ (6.0 ) $ — $ 275.9 Other investments 132.6 22.2 (17.0 ) — 137.8 Total common equity securities and other investments $ 395.1 $ 41.6 $ (23.0 ) $ — $ 413.7 December 31, 2015 ($ in millions) Cost or amortized cost Gross unrealized gains Gross unrealized losses Net unrealized foreign Carrying value Common equity securities $ 295.0 $ 12.7 $ (9.0 ) $ — $ 298.7 Other investments 135.6 22.3 (14.9 ) — 143.0 Total common equity securities and other investments $ 430.6 $ 35.0 $ (23.9 ) $ — $ 441.7 As of March 31, 2016 and December 31, 2015 , the Company held unrestricted collateral from its customers, primarily relating to its surety business, of $134.9 million and $137.7 million , respectively, which is included in cash and invested assets. The obligation to return these funds is classified as funds held under insurance contracts in the consolidated balance sheets. The following table summarizes the ratings of the debt securities issued by corporations owned by OneBeacon as of March 31, 2016 and December 31, 2015 : at Fair value ($ in millions) March 31, December 31, AAA (1) $ 2.6 $ — AA (1) 63.7 42.7 A (1) 252.2 265.4 BBB (1) 425.1 502.3 Debt securities issued by corporations (1) $ 743.6 $ 810.4 _______________________________________________________________________________ (1) Credit ratings are assigned based on the following hierarchy: 1) Standard and Poor’s Financial Services LLC (“Standard and Poor’s”) and 2) Moody’s Investor Service (“Moody’s”). Fair value measurements Fair value measurements are categorized into a hierarchy that distinguishes between inputs based on market data from independent sources ("observable inputs") and a reporting entity's internal assumptions based upon the best information available when external market data is limited or unavailable ("unobservable inputs"). Quoted prices in active markets for identical assets or liabilities have the highest priority ("Level 1"), followed by observable inputs other than quoted prices, including prices for similar but not identical assets or liabilities ("Level 2") and unobservable inputs, including the reporting entity's estimates of the assumptions that market participants would use, having the lowest priority ("Level 3"). As of both March 31, 2016 and December 31, 2015 , approximately 92% of the investment portfolio recorded at fair value was priced based upon observable inputs. Investments valued using Level 1 inputs include fixed maturity investments, primarily investments in U.S. Treasuries, common equity securities and short-term investments, which include U.S. Treasury Bills. Investments valued using Level 2 inputs comprise fixed maturity investments, which have been disaggregated into classes, including debt securities issued by corporations, municipal obligations, mortgage and asset-backed securities, foreign government obligations and preferred stocks. Investments valued using Level 2 inputs also include certain ETFs that track US stock indices such as the S&P 500 but are traded on foreign exchanges and that management values using the fund's published NAV to account for the difference in market close times. Fair value estimates for investments that trade infrequently and have few or no observable market prices are classified as Level 3 measurements. Level 3 fair value estimates based upon unobservable inputs include OneBeacon's investments in surplus notes which are measured at their estimated fair value based on discounted expected cash flows using information as of the measurement date, as well as certain investments in fixed maturity investments, common equity securities and other investments, where quoted market prices are unavailable or are not considered reasonable. OneBeacon determines when transfers between levels have occurred as of the beginning of the period. OneBeacon uses brokers and outside pricing services to assist in determining fair values. For investments in active markets, OneBeacon uses the quoted market prices provided by outside pricing services to determine fair value. The outside pricing services OneBeacon uses have indicated that they will only provide prices where observable inputs are available. In circumstances where quoted market prices are unavailable or are not considered reasonable, OneBeacon estimates the fair value using industry standard pricing models and observable inputs such as benchmark yields, reported trades, broker-dealer quotes, issuer spreads, benchmark securities, bids, offers, prepayment speeds, reference data including research publications and other relevant inputs. Given that many fixed maturity investments do not trade on a daily basis, the outside pricing services evaluate a wide range of fixed maturity investments by regularly drawing parallels from recent trades and quotes of comparable securities with similar features. The characteristics used to identify comparable fixed maturity investments vary by asset type and take into account market convention. OneBeacon's process to assess the reasonableness of the market prices obtained from the outside pricing sources covers substantially all of its fixed maturity investments and includes, but is not limited to, evaluation of model pricing methodologies, review of the pricing services' quality control processes and procedures on at least an annual basis, comparison of market prices to prices obtained from different independent pricing vendors on at least a semi-annual basis, monthly analytical reviews of certain prices and review of assumptions utilized by the pricing service for selected measurements on an ad hoc basis throughout the year. OneBeacon also performs back-testing of selected purchases and sales activity to determine whether there are any significant differences between the market price used to value the security prior to purchase or sale and the actual purchase or sale price on an ad-hoc basis throughout the year. Prices provided by the pricing services that vary by more than 5% and $1.0 million from the expected price based on these procedures are considered outliers. Also considered outliers are prices that haven’t changed from period to period and prices that have trended unusually compared to market conditions. In circumstances where the results of OneBeacon's review process does not appear to support the market price provided by the pricing services, OneBeacon challenges the price. If OneBeacon cannot gain satisfactory evidence to support the challenged price, it relies upon its own pricing methodologies to estimate the fair value of the security in question. The valuation process above is generally applicable to all of OneBeacon’s fixed maturity investments. The techniques and inputs specific to asset classes within OneBeacon's fixed maturity investments for Level 2 securities that use observable inputs are as follows: Debt securities issued by corporations: The fair value of debt securities issued by corporations is determined from an evaluated pricing model that uses information from market sources and integrates relative credit information, observed market movements, and sector news. Key inputs include benchmark yields, reported trades, broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including sector, coupon, quality ratings, duration, credit enhancements, early redemption features and market research publications. Municipal obligations: The fair value of municipal obligations is determined from an evaluated pricing model that uses information from market makers, broker-dealers, buy-side firms, and analysts along with general market information. Key inputs include benchmark yields, reported trades, issuer financial statements, material event notices and new issue data, as well as broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including type, coupon, credit quality ratings, duration, credit enhancements, geographic location and market research publications. Mortgage and asset-backed securities: The fair value of mortgage and asset backed securities is determined from an evaluated pricing model that uses information from market sources and leveraging similar securities. Key inputs include benchmark yields, reported trades, underlying tranche cash flow data, collateral performance, plus new issue data, as well as broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including issuer, vintage, loan type, collateral attributes, prepayment speeds, default rates, recovery rates, cash flow stress testing, credit quality ratings and market research publications. Foreign government obligations: The fair value of foreign government obligations is determined from an evaluated pricing model that uses feeds from data sources in each respective country, including active market makers and inter-dealer brokers. Key inputs include benchmark yields, reported trades, broker-dealer quotes, two-sided markets, benchmark securities, bids, offers, local exchange prices, foreign exchange rates and reference data including coupon, credit quality ratings, duration and market research publications. Preferred stocks: The fair value of preferred stocks is determined from an evaluated pricing model that calculates the appropriate spread over a comparable security for each issue. Key inputs include exchange prices (underlying and common stock of same issuer), benchmark yields, reported trades, broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data including sector, coupon, credit quality ratings, duration, credit enhancements, early redemption features and market research publications. Level 3 valuations are generated from techniques that use assumptions not observable in the market. These unobservable assumptions reflect OneBeacon's assumptions that market participants would use in valuing the investment. Generally, certain securities may start out as Level 3 when they are originally issued but as observable inputs become available in the market, they may be reclassified to Level 2. The fair values of OneBeacon's investments in hedge funds and private equity funds have been classified as net asset value as prescribed by ASU 2015-07. As of March 31, 2016 and December 31, 2015 , OneBeacon did not record a liquidity adjustment to the net asset value related to its investments in hedge funds or private equity funds. As of both March 31, 2016 and December 31, 2015 , other investments reported at fair value represented approximately 5% of the total investment portfolio and consisted of the following: ($ in millions) March 31, December 31, Hedge funds (1) $ 16.2 $ 16.4 Private equity funds (2) 41.3 46.1 Total hedge funds and private equity funds 57.5 62.5 Surplus notes (par value $101.0) (3) 51.8 51.5 Investment in community reinvestment vehicle 14.4 14.3 Total other investments (4) $ 123.7 $ 128.3 _______________________________________________________________________________ (1) Consists of 4 hedge funds as of both March 31, 2016 and December 31, 2015 . (2) Consists of 17 private equity funds as of both March 31, 2016 and December 31, 2015 . (3) The increase in the fair value of the surplus notes during the three months ended March 31, 2016 was primarily due to the time value of money benefit generated by moving one quarter closer to modeled cash receipts, offset by the negative valuation impact of an interest payment received in the first quarter of 2016. (4) Excludes the carrying value of $14.1 million and $14.7 million as of March 31, 2016 and December 31, 2015 , respectively, associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method. The largest investment in a single hedge fund or private equity fund was $12.7 million and $12.9 million as of March 31, 2016 and December 31, 2015 , respectively. As of both March 31, 2016 and December 31, 2015 , OneBeacon held one private preferred stock that represented approximately 85% of its preferred stock portfolio. OneBeacon used quoted market prices for similar securities that were adjusted to reflect management's best estimate of fair value; this security is classified as a Level 3 measurement. Surplus Notes In the fourth quarter of 2014, in conjunction with the Runoff Transaction, OneBeacon provided financing in the form of surplus notes having a par value of $101.0 million , which had a fair value of $51.8 million and $51.5 million as of March 31, 2016 and December 31, 2015 , respectively. The surplus notes, issued by one of the transferred entities, Bedivere (“Issuer”), were in the form of both seller priority and pari passu notes. The internal valuation model used to estimate the fair value is based on discounted expected cash flows using information as of the measurement date. The estimated fair value of the surplus notes is sensitive to changes in treasury rates and public debt credit spreads, as well as changes in estimates with respect to other variables including a discount to reflect the private nature of the notes (and the related lack of liquidity), the credit quality of the notes – based on the financial performance of the Issuer relative to expectations, and the timing, amount, and likelihood of interest and principal payments on the notes, which are subject to regulatory approval and therefore may vary from the contractual terms. An interest payment of $2.4 million was received in the three months ended March 31, 2016 . The Company has assumed for estimating value purposes that subsequent interest payouts will begin in year five (2020) and principal repayments begin on a graduating basis in year ten (2025) for the seller priority note and year fifteen (2030) for the pari passu note. Although these variables involve considerable judgment, the Company does not currently expect any resulting changes in the estimated value of the surplus notes to be material to its financial position. Below is a table illustrating the valuation adjustments taken to arrive at estimated fair value of the surplus notes as of March 31, 2016 and December 31, 2015 : Type of Surplus Note Total as of March 31, 2016 Seller Priority Pari Passu (in millions) Par value $ 57.9 $ 43.1 $ 101.0 Fair value adjustments to reflect: Current market rates on public debt and contract-based repayments (1) (0.5 ) (14.2 ) (14.7 ) Regulatory approval (2) (11.4 ) (13.0 ) (24.4 ) Liquidity adjustment (3) (7.8 ) (2.3 ) (10.1 ) Total (19.7 ) (29.5 ) (49.2 ) Fair value (4) $ 38.2 $ 13.6 $ 51.8 Type of Surplus Note Total as of December 31, 2015 Seller Priority Pari Passu (in millions) Par value $ 57.9 $ 43.1 $ 101.0 Fair value adjustments to reflect: Current market rates on public debt and contract-based repayments (1) (0.4 ) (14.7 ) (15.1 ) Regulatory approval (2) (11.7 ) (12.5 ) (24.2 ) Liquidity adjustment (3) (7.8 ) (2.4 ) (10.2 ) Total (19.9 ) (29.6 ) (49.5 ) Fair value $ 38.0 $ 13.5 $ 51.5 _______________________________________________________________________________ (1) Represents the value of the surplus notes, at current market yields on comparable publicly traded debt, and assuming issuer is allowed to make principal and interest payments when its financial capacity is available, as measured by statutory capital in excess of a 250% score under the National Association of Insurance Commissioners' risk-based capital standards for property and casualty companies. (2) Represents anticipated delay in securing regulatory approvals of interest and principal payments to reflect graduated changes in Issuer's statutory surplus. The monetary impact of the anticipated delay is measured based on credit spreads of public securities with roughly equivalent percentages of discounted payments missed. (3) Represents impact of liquidity spread to account for OneBeacon's sole ownership of the notes, lack of a trading market, and ongoing regulatory approval risk. (4) The increase in the fair value of the surplus notes during the three months ended March 31, 2016 was primarily due to the time value of money benefit generated by moving one quarter closer to modeled cash receipts, offset by the negative valuation impact of an interest payment received in the first quarter of 2016. Fair value measurements by level The following tables summarize the Company's fair value measurements for investments as of March 31, 2016 and December 31, 2015 by level. The major security types were based on the legal form of the securities. OneBeacon has disaggregated its fixed maturity investments based on the issuing entity type, which impacts credit quality, with debt securities issued by U.S. government entities carrying minimal credit risk, while the credit and other risks associated with other issuers, such as corporations, foreign governments, municipalities or entities issuing asset-backed securities vary depending on the nature of the issuing entity type. OneBeacon further disaggregates debt securities issued by corporations and common equity securities by industry sector because investors often reference commonly used benchmarks and their subsectors to monitor risk and performance. Accordingly, OneBeacon has further disaggregated these asset classes into subclasses based on the similar sectors and industry classifications the Company uses to evaluate investment risk and performance against commonly used benchmarks, such as the Barclays Intermediate Aggregate and S&P 500 indices. ($ in millions) Fair value at Level 1 Level 2 Level 3 Fixed maturity investments: U.S. Government and agency obligations $ 53.6 $ 53.6 $ — $ — Debt securities issued by corporations: Consumer 211.6 — 211.6 — Industrial 122.5 — 122.5 — Healthcare 109.5 — 109.5 — Financials 108.4 — 108.4 — Energy 59.8 — 59.8 — Utilities 42.1 — 42.1 — Communications 40.1 — 40.1 — Technology 28.9 — 28.9 — Basic materials 20.7 — 20.7 — Debt securities issued by corporations 743.6 — 743.6 — Municipal obligations 69.3 — 69.3 — Mortgage and asset-backed securities 1,077.8 — 1,077.8 — Foreign government obligations 1.2 0.7 0.5 — Preferred stocks 83.2 — 12.7 70.5 Fixed maturity investments 2,028.7 54.3 1,903.9 70.5 Short-term investments 119.7 119.7 — — Common equity securities: Exchange traded funds (1) 130.5 109.0 21.5 — Consumer 46.7 46.7 — — Technology 29.0 29.0 — — Healthcare 24.4 24.4 — — Communications 20.3 20.3 — — Industrial 17.0 17.0 — — Financials 8.0 8.0 — — Common equity securities 275.9 254.4 21.5 — Other investments (2)(3) 123.7 — — 66.3 Total (1)(2) $ 2,548.0 $ 428.4 $ 1,925.4 $ 136.8 _______________________________________________________________________________ (1) ETF's traded on foreign exchanges are priced using the fund's published NAV to account for the difference in market close times and are therefore designated as level 2 measurements. (2) Excludes the carrying value of $14.1 million associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method as of March 31, 2016 . (3) As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies" investments in hedge funds and private equity funds of $57.4 million measured at fair value for which NAV is the practical expedient are no longer classified within the fair value hierarchy. ($ in millions) Fair value at Level 1 Level 2 Level 3 Fixed maturity investments: U.S. Government and agency obligations $ 85.3 $ 85.3 $ — $ — Debt securities issued by corporations: Consumer 218.3 — 218.3 — Healthcare 136.2 — 136.2 — Industrial 121.8 — 121.8 — Financials 116.0 — 116.0 — Energy 75.2 — 75.2 — Communications 46.0 — 46.0 — Utilities 42.2 — 42.2 — Technology 28.9 — 28.9 — Basic materials 25.8 — 25.8 — Debt securities issued by corporations 810.4 — 810.4 — Municipal obligations 69.0 — 69.0 — Mortgage and asset-backed securities 1,031.9 — 1,031.9 — Foreign government obligations 1.2 0.6 0.6 — Preferred stocks 82.7 — 12.7 70.0 Fixed maturity investments 2,080.5 85.9 1,924.6 70.0 Short-term investments 69.2 69.2 — — Common equity securities: Exchange traded funds (1) 183.3 162.0 21.3 — Consumer 38.2 38.2 — — Communications 23.9 23.9 — — Healthcare 19.6 19.6 — — Technology 14.7 14.7 — — Industrial 14.5 14.5 — — Financials 4.5 4.5 — — Common equity securities 298.7 277.4 21.3 — Other investments (2)(3) 128.3 — — 65.9 Total (1)(2)(3) $ 2,576.7 $ 432.5 $ 1,945.9 $ 135.9 _______________________________________________________________________________ (1) ETF's traded on foreign exchanges are priced using the fund's published NAV to account for the difference in market close times and are therefore designated as level 2 measurements. (2) Excludes the carrying value of $14.7 million associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method as of December 31, 2015 . (3) As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies" investments in hedge funds and private equity funds of $62.4 million measured at fair value for which NAV is the practical expedient are no longer classified within the fair value hierarchy. Rollforwards of Fair Value Measurements by Level The following tables summarize the changes in OneBeacon’s fair value measurements by level for the three months ended March 31, 2016 and 2015 : Level 3 Investments ($ in millions) Level 1 Investments Level 2 Investments Fixed maturity investments Common equity securities Other investments (1) NAV investments (2) Total (1)(2)(3) Balance at January 1, 2016 $ 363.3 $ 1,945.9 $ 70.0 $ — $ 65.9 $ 62.4 $ 2,507.5 Amortization/accretion — (3.2 ) — — — — (3.2 ) Net realized and unrealized gains 5.6 12.5 0.5 — 0.4 (2.3 ) 16.7 Purchases 98.2 187.0 — — — 0.3 285.5 Sales (158.4 ) (216.8 ) — — — (3.0 ) (378.2 ) Transfers in — — — — — — — Transfers out — — — — — — — Balance at March 31, 2016 $ 308.7 $ 1,925.4 $ 70.5 $ — $ 66.3 $ 57.4 $ 2,428.3 _______________________________________________________________________________ (1) Excludes the carrying value of $14.1 million associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method as of March 31, 2016. (2) As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies" investments in hedge funds and private equity funds measured using the NAV practical expedient are no longer classified within the fair value hierarchy. (3) Excludes short-term investments. Level 3 Investments ($ in millions) Level 1 Investments Level 2 Investments Fixed maturity investments Common equity securities Other investments (1) NAV investments (2) Total (1)(2)(3) Balance at January 1, 2015 $ 358.7 $ 1,692.1 $ 74.0 $ — $ 79.6 102.4 $ 2,306.8 Amortization/accretion — (2.9 ) — — — — (2.9 ) Net realized and unrealized gains 5.5 7.3 0.3 — 3.1 (1.9 ) 14.3 Purchases 62.4 208.7 28.4 — — 1.4 300.9 Sales (75.2 ) (175.4 ) — — (0.1 ) (2.9 ) (253.6 ) Transfers in — 2.9 — — — — 2.9 Transfers out — — (2.9 ) — — — (2.9 ) Balance at March 31, 2015 $ 351.4 $ 1,732.7 $ 99.8 $ — $ 82.6 $ 99.0 $ 2,365.5 _______________________________________________________________________________ (1) Excludes the carrying value of $16.2 million associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method as of March 31, 2015. (2) As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies" investments in hedge funds and private equity funds measured using the NAV practical expedient are no longer classified within the fair value hierarchy. (3) Excludes short-term investments. There were no “Transfers in” to Level 3 or “Transfers out” of Level 3 for the three months ended March 31, 2016 . “Transfers out” of Level 3 fixed maturity investments of $2.9 million for the three months ended March 31, 2015 was comprised of one corporate debt security which had been previously classified as a Level 3 measurement and was recategorized as a Level 2 measurement when quoted market prices for similar securities that were considered reliable and could be validated against an alternative source became available. There were no “Transfers in” to Level 3 for the three months ended March 31, 2015. The following table summarizes the change in net pre-tax unrealized gains or losses for assets designated as Level 3 for the three months ended March 31, 2016 and 2015 : Three months ended ($ in millions) 2016 2015 Fixed maturity investments $ 0.5 $ 0.3 Other investments 0.4 3.0 Total $ 0.9 $ 3.3 Significant Unobservable Inputs As previously described, in certain circumstances, OneBeacon estimates the fair value of investments using industry standard pricing models and both observable and unobservable inputs. The following summarizes significant unobservable inputs used in estimating the fair value of fixed maturity and other investments classified within Level 3, as of March 31, 2016 and December 31, 2015 . ($ in millions) As of March 31, 2016 Description Fair Value (in millions) Rating (1) Valuation Technique Unobservable Inputs Input Preferred stock (2) $ 70.5 N/R Discounted cash flow Discount yield 8.1% Surplus notes: 15.8% - Seller priority note $ 38.2 N/R Discounted cash flow Discount rate (3) 12.5% Timing of interest payments (4) 5 years Timing of principal payments (4) 10 years - Pari passu note $ 13.6 N/R Discounted cash flow Discount rate (5) 22.5% Timing of interest payments (4) 5 years Timing of principal payments (4) 15 years ($ in millions) As of December 31, 2015 Description Fair Value (in millions) Rating (1) Valuation Technique Unobservable Inputs Input Preferred stock (2) $ 70.0 N/R Par value (6) Issuer's intent to call $70.0 Surplus notes: 16.1% - Seller priority note $ 38.0 N/R Discounted cash flow Discount rate (3) 13.0% Timing of interest payments (4) 5 years Timing of principal payments (4) 10 years - Pari passu note $ 13.5 N/R D

Debt

Debt	3 Months Ended
	Mar. 31, 2016
Debt Disclosure [Abstract]
Debt	Debt OneBeacon's debt outstanding as of March 31, 2016 and December 31, 2015 consisted of the following: ($ in millions) March 31, December 31, Senior unsecured notes, at face value $ 275.0 $ 275.0 Unamortized original issue discount (0.2 ) (0.2 ) Unamortized issuance costs (1) (1.9 ) (1.9 ) Senior unsecured notes, carrying value $ 272.9 $ 272.9 _______________________________________________________________________________ (1) Unamortized issuance costs have been reclassified from other assets to a decrease of the debt liability in accordance with ASU 2015-03. 2012 Senior Notes In November 2012, OneBeacon U.S. Holdings, Inc. ("OBH") issued $275.0 million face value of senior unsecured notes ("2012 Senior Notes") through a public offering, at an issue price of 99.9% and received $272.9 million of proceeds. The 2012 Senior Notes bear an annual interest rate of 4.6% payable semi-annually in arrears on May 9 and November 9, until maturity on November 9, 2022, and are fully and unconditionally guaranteed as to the payment of principal and interest by the Company. Taking into effect the amortization of the original issue discount and all underwriting and issuance expenses, the 2012 Senior Notes have an effective yield to maturity of approximately 4.7% per annum. Credit Facility On September 29, 2015, the Company and OBH, as co-borrowers and co-guarantors, entered into a revolving credit facility administered by U.S. Bank N.A. and also including BMO Harris Bank N.A., which has a total commitment of $65.0 million and has a maturity date of September 29, 2019 (the "Credit Facility"). As of March 31, 2016, the credit facility was undrawn. Debt Covenants The 2012 Senior Notes were issued under indentures that contain restrictive covenants which, among other things, limit the ability of the Company, OBH, and their respective subsidiaries to create liens and enter into sale and leaseback transactions and limits the ability of OneBeacon to consolidate, merge or transfer its properties and assets. The indentures do not contain any financial ratios or specified levels of net worth or liquidity to which the Company or OBH must adhere. In addition, a failure by the Company or its subsidiaries to pay principal and interest on covered debt, where such failure results in the acceleration of at least $75.0 million of the principal amount of covered debt, could trigger the acceleration of the 2012 Senior Notes. The Credit Facility contains various affirmative, negative and financial covenants which OneBeacon considers to be customary for such borrowings, including certain minimum net worth and maximum debt to capitalization standards. These covenants can restrict the Company in several ways, including its ability to incur additional indebtedness. An uncured breach of these covenants could result in an event of default under the Credit Facility, which would allow lenders to declare any amounts owed under the Credit Facility to be immediately due and payable. As of March 31, 2016 , OneBeacon was in compliance with all of the covenants under the 2012 Senior Notes and the Credit Facility.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Segment Information	pany has sixteen active underwriting operating segments, which are managed by the chief operating decision maker and are aggregated into two underwriting reportable segments. The two underwriting reportable segments were determined based on the nature of products or services, the production process, the method of distribution and the nature of the regulatory environment. The principal difference between the reportable segments is the type or class of customer. The Specialty Products reportable segment is comprised of ten active underwriting operating segments, representing an aggregation based on those that offer distinct products and tailored coverages and services to a broad customer base across the United States. Specialty Products includes the Healthcare, Management Liability, Financial Services, Other Professional Lines, Specialty Property, Environmental, Tuition Reimbursement, Programs, Surety and Financial Institutions underwriting operating segments, as well as Crop, which was exited in the third quarter of 2015. The Specialty Industries reportable segment is comprised of six active underwriting operating segments, representing an aggregation based on those that focus on solving the unique needs of a particular customer or industry group. The Specialty Industries segment includes the Ocean Marine, Inland Marine, Technology, Accident, Government Risks and Entertainment underwriting operating segments. The Investing, Financing and Corporate reportable segment includes the investing and financing activities for OneBeacon on a consolidated basis, and certain other activities conducted through the Company and its intermediate subsidiaries, including the 100% quota share reinsurance agreement with Bedivere, which cedes the losses associated with the legacy Runoff Business to Bedivere, one of the transferred entities that was sold as part of the Runoff Transaction. There is no net retention of the legacy Runoff Business to OneBeacon. Invested assets are not allocated to the Specialty Products and Specialty Industries segments since OneBeacon does not manage them by segment. Invested assets, net investment income and net realized and change in unrealized investment gains related to OneBeacon's Specialty Products and Specialty Industries segments are included in the Investing, Financing and Corporate segment since these assets are available for payment of losses and expenses for all segments. Debt and the related interest expense on debt also are not allocated to or managed by segment and are also included in the Investing, Financing and Corporate segment. Substantially all of the Company's revenue is generated from customers located in the United States. Financial information for OneBeacon's reportable segments is as follows: Insurance Operations Investing, Financing and Corporate ($ in millions) Specialty Products Specialty Industries Consolidated Three months ended March 31, 2016 Earned premiums $ 133.4 $ 145.2 $ — $ 278.6 Loss and loss adjustment expense (91.8 ) (67.0 ) — (158.8 ) Policy acquisition expenses (24.0 ) (27.0 ) — (51.0 ) Other underwriting expenses (23.4 ) (31.9 ) — (55.3 ) Total underwriting income (loss) (5.8 ) 19.3 — 13.5 Net investment income — — 14.4 14.4 Net realized and change in unrealized investment gains — — 16.6 16.6 Net other revenues (expenses) (0.1 ) 0.3 0.7 0.9 General and administrative expenses — (0.5 ) (3.4 ) (3.9 ) Interest expense — — (3.3 ) (3.3 ) Pre-tax income (loss) from continuing operations $ (5.9 ) $ 19.1 $ 25.0 $ 38.2 Three months ended March 31, 2015 Earned premiums $ 136.1 $ 150.5 $ — $ 286.6 Loss and loss adjustment expense (74.1 ) (91.8 ) — (165.9 ) Policy acquisition expenses (22.9 ) (28.1 ) — (51.0 ) Other underwriting expenses (25.7 ) (30.2 ) — (55.9 ) Total underwriting income 13.4 0.4 — 13.8 Net investment income — — 10.5 10.5 Net realized and change in unrealized investment gains — — 14.2 14.2 Net other revenues (expenses) — 0.2 (3.3 ) (3.1 ) General and administrative expenses — (0.5 ) (3.6 ) (4.1 ) Interest expense — — (3.2 ) (3.2 ) Pre-tax income from continuing operations $ 13.4 $ 0.1 $ 14.6 $ 28.1 Insurance Operations Investing, Financing and Corporate ($ in millions) Specialty Products Specialty Industries Consolidated March 31, 2016 Assets Total investment securities $ — $ — $ 2,562.1 $ 2,562.1 Premiums receivable 86.9 143.5 — 230.4 Reinsurance recoverables (1) 113.6 34.0 19.4 167.0 Deferred acquisition costs 52.9 49.1 — 102.0 Ceded unearned premiums 25.4 10.9 — 36.3 Other assets 1.1 0.1 430.0 431.2 Total Assets $ 279.9 $ 237.6 $ 3,011.5 $ 3,529.0 Liabilities Unpaid loss and loss adjustment expense reserves (1) $ 730.7 $ 593.7 $ 19.4 $ 1,343.8 Unearned premiums 305.7 262.9 — 568.6 Funds held under insurance contracts 134.9 — — 134.9 Debt — — 272.9 272.9 Other liabilities — — 189.0 189.0 Total Liabilities $ 1,171.3 $ 856.6 $ 481.3 $ 2,509.2 December 31, 2015 Assets Total investment securities $ — $ — $ 2,591.4 $ 2,591.4 Premiums receivable 63.0 156.0 — 219.0 Reinsurance recoverables (1) 139.5 33.6 20.4 193.5 Deferred acquisition costs 49.6 51.1 — 100.7 Ceded unearned premiums 19.2 10.3 — 29.5 Other assets 0.9 0.1 467.5 468.5 Total Assets $ 272.2 $ 251.1 $ 3,079.3 $ 3,602.6 Liabilities Unpaid loss and loss adjustment expense reserves (1) $ 772.2 $ 597.2 $ 20.4 $ 1,389.8 Unearned premiums 288.1 272.2 — 560.3 Funds held under insurance contracts 137.7 — — 137.7 Debt — — 272.9 272.9 Other liabilities — — 237.4 237.4 Total Liabilities $ 1,198.0 $ 869.4 $ 530.7 $ 2,598.1 _______________________________________________________________________________ (1) As described in Note 15—"Discontinued Operations," Atlantic Specialty Insurance Company (ASIC), the top tier regulated U.S. insurance operating subsidiary of the Company, is ceding to Bedivere 100% of the legacy Runoff Business that was written by ASIC or one of the ongoing entities. As of March 31, 2016 and December 31, 2015, $19.4 million and $20.4 million , respectively, are included in both unpaid loss and loss adjustment expense reserves and reinsurance recoverable included within Investing, Financing, and Corporate. The following tables provide net written premiums, earned premiums and underwriting ratios for OneBeacon's insurance operations by reportable segment and in total, for the three months ended March 31, 2016 and 2015 : Three months ended March 31, 2016 Three months ended March 31, 2015 ($ in millions) Specialty Products Specialty Industries Consolidated Specialty Specialty Consolidated Net written premiums $ 144.7 $ 135.4 $ 280.1 $ 133.6 $ 153.5 $ 287.1 Earned premiums 133.4 145.2 278.6 136.1 150.5 286.6 Underwriting ratios: (1) Loss and LAE 68.8 % 46.1 % 57.0 % 54.4 % 61.0 % 57.9 % Expense 35.6 40.5 38.2 35.8 38.7 37.3 Total combined ratio 104.4 % 86.6 % 95.2 % 90.2 % 99.7 % 95.2 % _______________________________________________________________________________ (1) Underwriting ratios are used to measure the components of underwriting profitability and include: the loss and LAE ratio, calculated by dividing loss and LAE by earned premiums; the expense ratio, calculated by dividing policy acquisition and other underwriting expenses by earned premiums; and the combined ratio, the sum of the loss and LAE ratio and the expense ratio.

Retirement Plans

Retirement Plans	3 Months Ended
	Mar. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Retirement Plans	Retirement Plans OneBeacon previously sponsored the OneBeacon qualified pension plan (the "Qualified Plan"). During the three months ended March 31, 2016, the Qualified Plan finalized its termination by purchasing group annuity contracts from the Principal Financial Group and making lump sum distributions to Qualified Plan participants electing such payments, which eliminated the remaining Qualified Plan liability. As a result of these transactions, the Company recognized a pre-tax pension settlement charge of $0.3 million and no longer has a projected benefit obligation with respect to the Qualified Plan as of March 31, 2016. The Company continues to hold $55.4 million of excess invested assets, of which it expects to transfer the majority of the assets into a defined contribution qualified replacement plan trust during 2016 to fund future benefits. A portion of the assets will remain in the Qualified Plan trust in order to wind-down potential post-termination obligations of that plan, as approved by way of a March 2016 private letter ruling from the IRS. These invested assets are included in other assets and are accounted for at fair value. The annuity purchase is subject to final true-up anticipated in the second quarter to the extent actual experience is different than expected up until OneBeacon ceases administratively paying claims on June 1, 2016. OneBeacon continues to sponsor a non-qualified, non-contributory, defined benefit pension plan ("Non-qualified Plan") covering substantially all employees who were employed as of December 31, 2001 and former employees who had met the eligibility requirements, as well as retirees. The Non-qualified Plan, was frozen and curtailed in 2002, resulting in the pension benefit obligation being equal to the accumulated benefit obligation. The benefits are based primarily on years of service and employees’ compensation through December 31, 2002. OneBeacon’s funding policy is generally to contribute amounts to satisfy actual disbursements for the calendar year. The components of net periodic benefit cost for the three months ended March 31, 2016 and 2015 for the Non-qualified Plan and Qualified Plan were as follows: Three months ended ($ in millions) 2016 2015 Service cost $ 0.2 $ 0.2 Interest cost 0.8 1.2 Expected return on plan assets (1.0 ) (2.2 ) Amortization of unrecognized loss 0.3 0.3 Net periodic pension cost (income) 0.3 (0.5 ) Settlement loss (1) 0.3 — Total net periodic benefit cost (income) $ 0.6 $ (0.5 ) _______________________________________________________________________________ (1) Represents the impact of the termination of the Qualified Pension Plan during the three months ended March 31, 2016 . OneBeacon anticipates contributing $2.1 million to the Non-qualified Plan in 2016, for which OneBeacon has assets held in a rabbi trust. During the three months ended March 31, 2016 , the Company contributed $0.5 million to the Non-qualified Plan. Other Benefit Plans OneBeacon sponsors an employee savings plan (defined contribution plan) covering the majority of employees. The contributory plan provides qualifying employees with matching contributions of 50% of the first 6% of salary (subject to federal limits on allowable contributions in a given year). Total expense for the matching component of this plan was $0.7 million in the three months ended March 31, 2016 and 2015 . The employee savings plan includes an employee stock ownership component. See Note 9—"Employee Share-Based Incentive Compensation Plans." OneBeacon had a post-employment benefit liability related to disability and health benefits available to former employees that are no longer employed by the Company of $3.9 million and $4.1 million as of March 31, 2016 and December 31, 2015, respectively. OneBeacon also had a post-employment benefit liability related to death benefits to beneficiaries of former executives that are no longer employed by the Company of $12.4 million and $12.5 million as of March 31, 2016 and December 31, 2015, respectively. OneBeacon has set aside funds to satisfy its obligation in a rabbi trust of $34.5 million and $33.9 million as of March 31, 2016 and December 31, 2015, respectively.

Employee Share-Based Incentive

Employee Share-Based Incentive Compensation Plans	3 Months Ended
	Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Employee Share-Based Incentive Compensation Plans	Employee Share-Based Incentive Compensation Plans OneBeacon's share-based compensation plans include performance shares, restricted shares and restricted stock units ("RSUs"), which are designed to maximize shareholder value over long periods of time by aligning the financial interests of its management with those of its owners. Performance shares are payable only upon achievement of pre-defined business goals and are valued based on the market value of OneBeacon's common shares at the time awards are earned. Performance shares and restricted stock units are typically paid in cash, though, in some instances, they may be paid in common shares or may be deferred in accordance with the terms of OneBeacon's deferred compensation plan. Restricted shares vest either annually in equal installments over the specified service period or cliff-vest in full after the 2 to 3 -year service period, depending on the award. OneBeacon expenses the full cost of all its share-based compensation over the requisite service period. The Company recognized expense related to its share-based compensation plans, including the OneBeacon 401(k) Savings and Employee Stock Ownership Plan ("KSOP"), of $2.7 million and $2.1 million for the three months ended March 31, 2016 and 2015 , respectively. Performance Shares The following summarizes performance share activity for the three months ended March 31, 2016 and 2015 : Three months ended March 31, 2016 2015 ($ in millions) Target Performance Shares outstanding Accrued expense Target Performance Shares outstanding Accrued expense Beginning of period 449,435 $ 1.4 517,470 $ 3.4 Payments and deferrals (1) (167,300 ) (0.7 ) (181,290 ) (1.5 ) New awards 163,150 — 154,887 — Forfeitures and net change in assumed forfeitures (4,079 ) — (28,920 ) — Expense recognized — 0.4 — 0.2 End of period 441,206 $ 1.1 462,147 $ 2.1 _______________________________________________________________________________ (1) Performance share payments in 2016 for the 2013-2015 performance cycle were based upon a performance factor of 24.3% . Performance share payments in 2015 for the 2012-2014 performance cycle were based upon a performance factor of 45.7% . The following summarizes performance shares outstanding and accrued performance share expense at March 31, 2016 for each performance cycle: ($ in millions) Target OB Performance Shares outstanding Accrued expense Performance cycle: 2014 - 2016 142,710 $ 0.1 2015 - 2017 146,659 0.8 2016 - 2018 163,150 0.2 Subtotal 452,519 1.1 Assumed forfeitures (11,313 ) — Total at March 31, 2016 441,206 $ 1.1 If 100% of the outstanding performance shares had been vested on March 31, 2016 , the total additional compensation cost to be recognized would have been $3.1 million , based on current accrual factors (common share price, accumulated dividends and payout assumptions) at March 31, 2016 . All performance shares earned and paid were settled in cash or by deferral into OneBeacon's deferred compensation plan. Restricted Shares On February 24, 2016, OneBeacon issued to certain employees 170,650 shares of restricted stock having a grant date fair value of $2.3 million , of which 92,500 are scheduled to cliff vest in full on February 24, 2018 and the remaining 78,150 are scheduled to cliff vest in full on January 1, 2019 . On February 24, 2015, OneBeacon issued to certain employees 75,950 shares of restricted stock having a grant date fair value of $1.1 million , which are scheduled to cliff vest in full on January 1, 2018. On May 25, 2011, OneBeacon issued to its CEO 630,000 shares of restricted stock, of which 157,500 restricted shares vested on each of February 22, 2014, 2015 and 2016, and the remaining 157,500 restricted shares are scheduled to vest on February 22, 2017. The restricted shares contain dividend participation features and therefore are considered participating securities. The following summarizes restricted shares activity for the three months ended March 31, 2016 and 2015 : Three months ended March 31, 2016 2015 ($ in millions) Restricted Shares Unamortized Issue Date Fair Value Restricted Shares Unamortized Issue Date Fair Value Beginning of period 382,722 $ 2.5 612,500 $ 3.5 New awards 170,650 2.3 75,950 1.1 Forfeitures — — (1,500 ) — Vested (157,500 ) — (296,000 ) — Expense recognized — (0.5 ) — (0.6 ) End of period 395,872 $ 4.3 390,950 $ 4.0 Restricted shares that vested during the three months ended March 31, 2016 and 2015 had a grant date fair value of $2.1 million and $4.3 million , respectively. As of March 31, 2016 , unrecognized compensation expense of $4.3 million related to restricted stock awards is expected to be recognized over a weighted-average period of 0.9 years. Restricted Stock Units During the three months ended March 31, 2016 , 222,449 RSUs were issued, and were all outstanding as of March 31, 2016 . The RSUs are scheduled to cliff vest in full on January 1, 2019, at which time the RSUs will be paid out in cash or shares at the discretion of the Compensation Committee. During the three months ended March 31, 2015 , 207,848 RSUs were issued, with outstanding RSUs, net of forfeitures, at 198,928 as of March 31, 2016 . The expense associated with the RSUs, which is being recognized over the vesting period, was $0.4 million and $0.1 million for the three months ended March 31, 2016 and 2015, respectively. Other Share-Based Compensation OneBeacon sponsors a defined contribution plan, the KSOP. Under the KSOP, participants have the ability to invest their balances in several different investment options, including the common shares of White Mountains and the common shares of the Company. The employee stock ownership component of the KSOP provides all participants with an annual base contribution in common shares of the Company equal to 3% of their salary, up to the applicable Social Security wage base (or $118,500 with respect to 2016). Additionally, those participants not otherwise eligible to receive certain other Company benefits can earn a variable contribution up to an additional 6% of their salary, capped at the annual covered compensation limits ( $265,000 for 2016), contingent upon OneBeacon's performance. OneBeacon has recorded $1.4 million and $1.2 million in compensation expense to pay benefits and allocate common shares to participants' accounts for the three months ended March 31, 2016 and 2015 , respectively. As of March 31, 2016 and December 31, 2015 , the KSOP owned less than 3% of either of the total White Mountains common shares outstanding or the total Company common shares outstanding. All common shares held by the KSOP are considered outstanding for earnings per share computations.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes OneBeacon and its Bermuda-domiciled subsidiaries are not subject to Bermuda income tax under current Bermuda law. In the event that there is a change in the current law such that taxes are imposed, OneBeacon and its Bermuda-domiciled subsidiaries would be exempt from such tax until March 31, 2035, pursuant to the Bermuda Exempted Undertakings Tax Protection Act of 1966. OneBeacon also has subsidiaries that operate in Gibraltar, Barbados, Luxembourg, the United Kingdom and the United States. U.S. operations are financed with a combination of debt and equity and the financing income and underwriting income currently account for the majority of non-U.S. earnings. OneBeacon's income tax (benefit) expense related to pre-tax income from continuing operations for the three months ended March 31, 2016 and 2015 , represented net effective tax rates of (22.8)% and 12.1% , respectively. The effective tax rates for the three months ended March 31, 2016 and 2015 , were lower than the U.S. statutory rate of 35% due to income generated in jurisdictions other than the United States, principally representing interest income and underwriting income taxed in a jurisdiction with a lower effective tax rate. Additionally, the rate for the three months ended March 31, 2016 was impacted by a $12.8 million favorable settlement of the 2007-2009 IRS exam, as further described below. For the three months ended March 31, 2016 and 2015 , the effective tax rate on non-U.S. income was 0.7% and 1.2% , respectively. In arriving at the effective tax rate for the three months ended March 31, 2016 and 2015 , OneBeacon forecasted all income and expense items including the realized and change in unrealized investment gains for the years ending December 31, 2016 and 2015 , and included these gains in the effective tax rate calculation. OneBeacon records a valuation allowance against deferred tax assets if it becomes more likely than not that all or a portion of a deferred tax asset will not be realized. Changes in valuation allowances from period to period are included in income tax expense in the period of change. In determining whether or not a valuation allowance, or change therein, is warranted, OneBeacon considers factors such as prior earnings history, expected future earnings, carryback and carryforward periods as well as prudent and economically feasible strategies that, if executed would result in the realization of a deferred tax asset. It is possible that certain planning strategies or projected earnings in certain subsidiaries may not be feasible to utilize the entire deferred tax asset, which could result in material changes to OneBeacon’s deferred tax assets and tax expense. OneBeacon classifies all interest and penalties on unrecognized tax benefits as part of income tax expense. With few exceptions, OneBeacon is no longer subject to U.S. federal, state or non-U.S. income tax examinations by tax authorities for years before 2010. On January 19, 2016, OneBeacon received Form 870-AD (Offer to Waive Restrictions on Assessment and Collection Tax Deficiency and to Accept Overassessment) from the IRS Appeals Office relating to the examination of tax years 2007, 2008 and 2009. All disputed items have now been agreed to and resolved with the Joint Committee on Taxation. As the receipt of the Form 870-AD described above represents formal settlement, OneBeacon recorded a tax benefit of $12.8 million in the first quarter of 2016 related to tax years 2007, 2008 and 2009. On September 5, 2013, the IRS commenced an examination of OneBeacon's U.S. income tax returns for 2010, 2011 and 2012. On March 22, 2016, OneBeacon received Form 4549-A (Income Tax Discrepancy Adjustments) from the IRS relating to the examination of tax years 2010, 2011 and 2012. The estimated total overpayment is $6.0 million . However, $4.7 million of the adjustments relate to items for which the expense deduction has been disallowed in an earlier period, but deductibility will occur in a year being examined. Because of the impact of deferred tax accounting, other than interest and penalties, the allowance of the deduction in the exam period would not affect the effective tax rate. OneBeacon does not expect the resolution of this examination to result in a material change to its financial position.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments OneBeacon carries its financial instruments on its balance sheet at fair value with the exception of its investment in qualified affordable housing projects, which is accounted for using the proportional amortization method, and fixed-rate, long-term indebtedness. For certain financial instruments where quoted market prices are not available, other independent valuation techniques and assumptions are used. Because considerable judgment is used, these estimates are not necessarily indicative of amounts that could be realized in a current market exchange. Certain financial instruments are excluded from disclosure, including insurance contracts. As of March 31, 2016 and December 31, 2015 , the fair value of OneBeacon's 2012 Senior Notes (its fixed-rate, long-term indebtedness) was $278.0 million and $276.4 million , respectively. As described in Note 6—"Debt", the net carrying value of the 2012 Senior Notes was $272.9 million as of both March 31, 2016 and December 31, 2015 . The fair value measurement of the 2012 Senior Notes is classified as Level 2 in the valuation hierarchy and determined based on the closing market price at the end of the fiscal quarter.

Legal Contingencies

Legal Contingencies	3 Months Ended
	Mar. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Legal Contingencies	Legal Contingencies OneBeacon, and the insurance and reinsurance industry in general, is routinely subject to claims related litigation and arbitration in the normal course of business, as well as litigation and arbitration that does not arise from, or directly relate to, claims activity. OneBeacon's estimates of the costs of settling matters routinely encountered in claims activity are reflected in the reserves for unpaid loss and LAE. See Note 3—"Unpaid Loss and Loss Adjustment Expense ("LAE") Reserves." OneBeacon evaluates its exposure to non-claims related litigation and arbitration and establishes accruals for litigation and arbitration if it is probable that a loss has been incurred and it can be reasonably estimated. Disclosure of litigation and arbitration is made if it is probable that a loss has been incurred or if there is a reasonable possibility that a loss may have been incurred. Although the ultimate outcome of claims and non-claims related litigation and arbitration, and the amount or range of potential loss at any particular time, is often inherently uncertain, management does not believe that the ultimate outcome of such claims and non-claims related litigation and arbitration will have a material adverse effect on OneBeacon's financial condition, full year results of operations, or cash flows. The following summarizes significant ongoing non-claims related litigation or arbitration as of March 31, 2016 : Deutsche Bank Litigation In June 2011, Deutsche Bank Trust Company Americas, Law Debenture Company of New York and Wilmington Trust Company (collectively referred to as “Plaintiffs”), in their capacity as trustees for certain senior notes issued by the Tribune Company (“Tribune”), filed lawsuits in various jurisdictions (the “Noteholder Actions”) against numerous defendants including OneBeacon, OneBeacon-sponsored benefit plans and other affiliates of White Mountains in their capacity as former shareholders of Tribune seeking recovery of the proceeds from the sale of common stock of Tribune in connection with Tribune's leveraged buyout in 2007 (the “LBO”). Tribune filed for bankruptcy in 2008 in the Delaware bankruptcy court (the “Bankruptcy Court”). The Bankruptcy Court granted Plaintiffs permission to commence these LBO-related actions, and in 2011, the Judicial Panel on Multidistrict Litigation granted a motion to consolidate the actions for pretrial matters and transferred all such proceedings to the United States District Court for the Southern District of New York. Plaintiffs seek recovery of the proceeds received by the former Tribune shareholders on a theory of constructive fraudulent transfer asserting that Tribune purchased or repurchased its common shares without receiving fair consideration at a time when it was, or as a result of the purchases of shares, was rendered, insolvent. OneBeacon has entered into a joint defense agreement with other affiliates of White Mountains that are defendants in the action. OneBeacon and OneBeacon-sponsored benefit plans received approximately $32 million for Tribune common stock tendered in connection with the LBO. The Court granted an omnibus motion to dismiss the Noteholders Action in September 2013 and plaintiffs appealed. On March 29, 2016, a three judge panel of the U.S Second Circuit Court of Appeals affirmed the dismissal of the Noteholders Action. The plaintiffs may now accept the decision, ask the three judge panel to reconsider, file a motion for a rehearing en banc or seek a writ of certiorari to the U.S. Supreme Court. In addition, OneBeacon, OneBeacon-sponsored benefit plans and other affiliates of White Mountains in their capacity as former shareholders of Tribune, along with thousands of former Tribune shareholders, have been named as defendants in an adversary proceeding brought by the Official Committee of Unsecured Creditors of the Tribune Company (the “Committee”), on behalf of the Tribune Company, which seeks to avoid the repurchase of shares by Tribune in the LBO on a theory of intentional fraudulent transfer (the “Committee Action”). Tribune emerged from bankruptcy in 2012, and a litigation trustee replaced the Committee as plaintiff in the Committee Action. This matter was consolidated for pretrial matters with the Noteholder Actions in the United States District Court for the Southern District of New York and was stayed pending the motion to dismiss in the Noteholder Action. An omnibus motion to dismiss the shareholder defendants in the Committee Action was filed in May 2014. No amount has been accrued in connection with this matter as of March 31, 2016 , as the amount of loss, if any, cannot be reasonably estimated.

Earnings (loss) per Share

Earnings (loss) per Share	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share Basic and diluted earnings per share amounts are based on the weighted average number of common shares outstanding, including unvested restricted shares that are considered participating securities. Diluted earnings per share amounts are based on the weighted average number of common shares including unvested restricted shares. The following table outlines the Company's computation of earnings per share for net income from continuing operations attributable to OneBeacon's common shareholders for the three months ended March 31, 2016 and 2015 : Three months ended 2016 2015 Earnings attributable to OneBeacon's common shareholders—basic and diluted (in millions): Net income from continuing operations attributable to OneBeacon's common shareholders $ 46.4 $ 24.2 Allocation of income for participating unvested restricted common shares (0.2 ) (0.1 ) Dividends paid on participating restricted common shares — (0.1 ) Total allocation to restricted common shares (0.2 ) (0.2 ) Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts $ 46.2 $ 24.0 Undistributed net earnings (in millions): Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts $ 46.2 $ 24.0 Dividends paid, net of restricted common share amounts (19.8 ) (19.9 ) Total undistributed net earnings, net of restricted common share amounts $ 26.4 $ 4.1 Earnings per share denominator—basic and diluted (in millions): Total weighted average common shares outstanding 94.5 95.3 Weighted average unvested restricted common shares (1) (0.4 ) (0.5 ) Basic and diluted earnings per share denominator 94.1 94.8 Earnings per share attributable to OneBeacon's common shareholders—basic and diluted (in dollars): Net income from continuing operations attributable to OneBeacon's common shareholders $ 0.49 $ 0.25 Dividends declared and paid (0.21 ) (0.21 ) Undistributed earnings $ 0.28 $ 0.04 _______________________________________________________________________________ (1) Restricted shares outstanding vest in equal installments upon a stated date or upon the occurrence of a specified event.

Common Shareholders' Equity

Common Shareholders' Equity	3 Months Ended
	Mar. 31, 2016
Stockholders' Equity Note [Abstract]
Common Shareholders' Equity	Common Shareholders' Equity Common Shares Repurchased and Retired On August 22, 2007, the Company's Board authorized the repurchase of up to $200.0 million of its Class A common shares from time to time, subject to market conditions. Shares may be repurchased on the open market or through privately negotiated transactions. This authorization does not have a stated expiration date. During the three months ended March 31, 2016 , 850,349 shares were repurchased under the share repurchase authorization for $10.6 million at an average share price of $12.42 . No shares were repurchased under the share repurchase authorization during the three months ended March 31, 2015 . The amount of authorization remaining is $75.0 million as of March 31, 2016 . During the three months ended March 31, 2016 and 2015 , the Company repurchased 64,981 and 112,051 common shares, respectively, for $0.9 million and $1.6 million for the three months ended March 31, 2016 and 2015 , respectively, to satisfy employee income tax withholding, pursuant to employee benefit plans. Shares repurchased pursuant to employee benefit plans do not reduce the board authorization referred to above. During the three months ended March 31, 2016, no restricted shares were forfeited, with 1,500 such forfeitures occurring during the three months ended March 31, 2015. Dividends on Common Shares During the three months ended March 31, 2016 and 2015 the Company declared and paid cash dividends to OneBeacon shareholders of $0.21 per common share for a total of $19.8 million and $20.0 million , respectively. Accumulated Other Comprehensive Loss The pre-tax components of the Company's other comprehensive income and the related tax expense are as follows: Three months ended March 31, ($ in millions) 2016 2015 Net change in benefit plan assets and obligations $ — $ 0.3 Income tax expense — (0.1 ) Net change in benefit plan assets and obligations, net of tax $ — $ 0.2

Discontinued Operations

Discontinued Operations	3 Months Ended
	Mar. 31, 2016
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Discontinued Operations Runoff Business As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies" and Note 2—"Acquisitions and Dispositions," on December 23, 2014, OneBeacon completed the sale of its Runoff Business to Armour. In conjunction with the Runoff Transaction, OneBeacon provided financing in the form of surplus notes issued by Bedivere having a par value of $101.0 million , which had a fair value of $64.9 million on the date of sale. Subsequent to the date of sale, these notes have been included in other investments on OneBeacon's consolidated balance sheet. See Note 5—"Investment Securities" for further disclosures regarding these surplus notes. The vast majority of the gross and net run-off unpaid loss and LAE reserves were included in the entities that were transferred to Armour. As of March 31, 2016 and December 31, 2015 , gross loss and LAE reserves of $19.4 million and $20.4 million , respectively, related to the Runoff Business were ceded to Bedivere, an indirect wholly-owned subsidiary of Armour, by way of a 100% quota share agreement with ASIC. Summary of Results of Operations There was no loss from discontinued operations for the three months ended March 31, 2016 . The loss from discontinued operations, net of tax, of $0.1 million for the three months ended March 31, 2015 , was the result of post-closing expenses incurred in connection with the Runoff Business.

Consolidating Financial Informa

Consolidating Financial Information	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidating Financial Information	Consolidating Financial Information The Company has fully and unconditionally guaranteed the 2012 Senior Notes issued by its 100% owned subsidiary, OBH, as well as any draw made by OBH on the Credit Facility, which was undrawn as of March 31, 2016. The following tables present OneBeacon's consolidating balance sheets as of March 31, 2016 and December 31, 2015 and statements of operations and comprehensive income for the three months ended March 31, 2016 and 2015 and cash flows for the three months ended March 31, 2016 and 2015 . These financial statements reflect the Company's ("guarantor") financial position, results of operations and cash flows on a stand-alone basis, that of OBH ("the issuer") and of the Company's other entities ("non-guarantor subsidiaries") as well as the necessary consolidating adjustments to eliminate intercompany balances and transactions. Consolidating Balance Sheet As of March 31, 2016 (in millions) The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Assets Investment Securities: Fixed maturity investments, at fair value $ — $ 2,028.7 $ — $ — $ 2,028.7 Short-term investments, at amortized cost (which approximates fair value) 4.2 115.4 0.1 — 119.7 Common equity securities, at fair value — 275.9 — — 275.9 Other investments — 137.8 — — 137.8 Total investment securities 4.2 2,557.8 0.1 — 2,562.1 Cash — 108.6 0.2 — 108.8 Reinsurance recoverables — 167.0 — — 167.0 Premiums receivable — 230.4 — — 230.4 Deferred acquisition costs — 102.0 — — 102.0 Ceded unearned premiums — 36.3 — — 36.3 Net deferred tax asset — 134.0 — 0.1 134.1 Investment income accrued — 9.4 — — 9.4 Accounts receivable on unsettled investment sales — 4.5 — — 4.5 Investments in subsidiaries 1,013.5 — 982.8 (1,996.3 ) — Other assets 0.2 171.4 2.8 — 174.4 Total assets $ 1,017.9 $ 3,521.4 $ 985.9 $ (1,996.2 ) $ 3,529.0 Liabilities Unpaid loss and loss adjustment expense reserves $ — $ 1,343.8 $ — $ — $ 1,343.8 Unearned premiums — 568.6 — — 568.6 Funds held under insurance contracts — 134.9 — — 134.9 Debt — — 272.9 — 272.9 Accounts payable on unsettled investment purchases — 1.5 — — 1.5 Other liabilities 1.3 177.1 9.1 — 187.5 Total liabilities 1.3 2,225.9 282.0 — 2,509.2 OneBeacon's common shareholders' equity and noncontrolling interests Total OneBeacon's common shareholders' equity 1,016.6 1,292.3 703.9 (1,996.2 ) 1,016.6 Total noncontrolling interests — 3.2 — — 3.2 Total OneBeacon's common shareholders' equity and noncontrolling interests 1,016.6 1,295.5 703.9 (1,996.2 ) 1,019.8 Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests $ 1,017.9 $ 3,521.4 $ 985.9 $ (1,996.2 ) $ 3,529.0 Consolidating Balance Sheet As of December 31, 2015 (in millions) The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Assets Investment Securities: Fixed maturity investments, at fair value $ — $ 2,074.6 $ 5.9 $ — $ 2,080.5 Short-term investments, at amortized cost (which approximates fair value) 4.4 64.1 0.7 — 69.2 Common equity securities, at fair value — 298.7 — — 298.7 Other investments — 143.0 — — 143.0 Total investment securities 4.4 2,580.4 6.6 — 2,591.4 Cash — 94.6 0.6 — 95.2 Reinsurance recoverables — 193.5 — — 193.5 Premiums receivable — 219.0 — — 219.0 Deferred acquisition costs — 100.7 — — 100.7 Ceded unearned premiums — 29.5 — — 29.5 Net deferred tax asset — 140.1 — 0.1 140.2 Investment income accrued — 10.1 — — 10.1 Accounts receivable on unsettled investment sales — 30.5 — — 30.5 Investments in subsidiaries 996.9 — 951.3 (1,948.2 ) — Other assets 0.5 190.6 1.4 — 192.5 Total assets $ 1,001.8 $ 3,589.0 $ 959.9 $ (1,948.1 ) $ 3,602.6 Liabilities Unpaid loss and loss adjustment expense reserves $ — $ 1,389.8 $ — $ — $ 1,389.8 Unearned premiums — 560.3 — — 560.3 Funds held under insurance contracts — 137.7 — — 137.7 Debt — — 272.9 — 272.9 Other liabilities 0.9 230.4 6.1 — 237.4 Total liabilities 0.9 2,318.2 279.0 — 2,598.1 OneBeacon's common shareholders' equity and noncontrolling interests Total OneBeacon's common shareholders' equity 1,000.9 1,267.2 680.9 (1,948.1 ) 1,000.9 Total noncontrolling interests — 3.6 — — 3.6 Total OneBeacon's common shareholders' equity and noncontrolling interests 1,000.9 1,270.8 680.9 (1,948.1 ) 1,004.5 Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests $ 1,001.8 $ 3,589.0 $ 959.9 $ (1,948.1 ) $ 3,602.6 Consolidating Statement of Operations and Comprehensive Income Three months ended March 31, 2016 The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Revenues Earned premiums $ — $ 278.6 $ — $ — $ 278.6 Net investment income — 14.4 — — 14.4 Net realized and change in unrealized investment gains — 16.6 — — 16.6 Net other revenues — 0.9 — — 0.9 Total revenues — 310.5 — — 310.5 Expenses Loss and loss adjustment expenses — 158.8 — — 158.8 Policy acquisition expenses — 51.0 — — 51.0 Other underwriting expenses — 55.3 — — 55.3 General and administrative expenses 1.2 2.7 — — 3.9 Interest expense — — 3.3 — 3.3 Total expenses 1.2 267.8 3.3 — 272.3 Pre-tax income (loss) from continuing operations (1.2 ) 42.7 (3.3 ) — 38.2 Income tax benefit — 7.1 1.6 — 8.7 Net income (loss) from continuing operations (1.2 ) 49.8 (1.7 ) — 46.9 Loss from discontinued operations, net of tax — — — — — Income (loss) before equity in earnings of unconsolidated affiliates (1.2 ) 49.8 (1.7 ) — 46.9 Equity in earnings of subsidiaries, net of tax 47.6 — 22.7 (70.3 ) — Net income including noncontrolling interests 46.4 49.8 21.0 (70.3 ) 46.9 Less: Net income attributable to noncontrolling interests — (0.5 ) — — (0.5 ) Net income attributable to OneBeacon's common shareholders 46.4 49.3 21.0 (70.3 ) 46.4 Other comprehensive income, net of tax — — — — — Comprehensive income attributable to OneBeacon's common shareholders $ 46.4 $ 49.3 $ 21.0 $ (70.3 ) $ 46.4 Consolidating Statement of Operations and Comprehensive Income Three months ended March 31, 2015 The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Revenues Earned premiums $ — $ 286.6 $ — $ — $ 286.6 Net investment income — 10.5 — — 10.5 Net realized and change in unrealized investment gains — 14.2 — — 14.2 Net other revenues (expenses) — (3.1 ) — — (3.1 ) Total revenues — 308.2 — — 308.2 Expenses Loss and loss adjustment expenses — 165.9 — — 165.9 Policy acquisition expenses — 51.0 — — 51.0 Other underwriting expenses — 55.9 — — 55.9 General and administrative expenses 1.3 2.7 0.1 — 4.1 Interest expense — — 3.2 — 3.2 Total expenses 1.3 275.5 3.3 — 280.1 Pre-tax income (loss) from continuing operations (1.3 ) 32.7 (3.3 ) — 28.1 Income tax (expense) benefit — (4.8 ) 1.4 — (3.4 ) Net income (loss) from continuing operations (1.3 ) 27.9 (1.9 ) — 24.7 Loss from discontinued operations, net of tax — (0.1 ) — — (0.1 ) Net income (loss) before equity in earnings of unconsolidated affiliates (1.3 ) 27.8 (1.9 ) — 24.6 Equity in earnings of subsidiaries, net of tax 25.4 — 12.6 (38.0 ) — Net income including noncontrolling interests 24.1 27.8 10.7 (38.0 ) 24.6 Less: Net income attributable to noncontrolling interests — (0.5 ) — — (0.5 ) Net income attributable to OneBeacon's common shareholders 24.1 27.3 10.7 (38.0 ) 24.1 Other comprehensive income, net of tax 0.2 — 0.2 (0.2 ) 0.2 Comprehensive income attributable to OneBeacon's common shareholders $ 24.3 $ 27.3 $ 10.9 $ (38.2 ) $ 24.3 Consolidating Statement of Cash Flows The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Cash flows from operations: Net income including noncontrolling interests $ 46.4 $ 49.8 $ 21.0 $ (70.3 ) $ 46.9 Charges (credits) to reconcile net income to cash flows provided from (used for) operations: Undistributed earnings from subsidiaries (47.6 ) — (22.7 ) 70.3 — Net realized and change in unrealized investment gains — (16.6 ) — — (16.6 ) Deferred income tax expense — 6.7 — — 6.7 Dividends received from subsidiaries 31.0 — — (31.0 ) — Other operating items: Net change in loss and LAE reserves — (46.0 ) — — (46.0 ) Net change in unearned premiums — 8.3 — — 8.3 Net change in ceded unearned premiums — (6.8 ) — — (6.8 ) Net change in premiums receivable — (11.4 ) — — (11.4 ) Net change in reinsurance recoverables on paid and unpaid losses — 26.5 — — 26.5 Net change in funds held under insurance contracts — (2.8 ) — — (2.8 ) Net change in other assets and liabilities 1.3 (31.2 ) 1.6 — (28.3 ) Net cash provided from (used for) operations 31.1 (23.5 ) (0.1 ) (31.0 ) (23.5 ) Cash flows from investing activities: Net maturities, purchases and sales of short-term investments 0.2 (51.3 ) 0.6 — (50.5 ) Maturities of fixed maturity investments — 110.1 — — 110.1 Sales of fixed maturity investments — 161.9 5.9 (5.9 ) 161.9 Sales of common equity securities — 103.2 — — 103.2 Return of capital and distributions of other investments — 3.0 — — 3.0 Purchases of fixed maturity investments — (215.7 ) — 5.9 (209.8 ) Purchases of common equity securities — (75.4 ) — — (75.4 ) Contributions for other investments — (0.3 ) — — (0.3 ) Net change in unsettled investment purchases and sales — 27.6 — — 27.6 Net acquisitions of property and equipment — (0.9 ) — — (0.9 ) Capital contribution from parent — 8.8 2.0 (10.8 ) — Net cash provided from investing activities 0.2 71.0 8.5 (10.8 ) 68.9 Cash flows from financing activities: Cash dividends paid to common shareholders (19.8 ) — — — (19.8 ) Cash dividends paid to parent — (31.0 ) — 31.0 — Capital contribution to subsidiary — (2.0 ) (8.8 ) 10.8 — Repurchases and retirements of common stock (11.5 ) — — — (11.5 ) Payments on capital lease obligation — (0.5 ) — — (0.5 ) Net cash used for financing activities (31.3 ) (33.5 ) (8.8 ) 41.8 (31.8 ) Net increase (decrease) in cash during period — 14.0 (0.4 ) — 13.6 Cash balance at beginning of period — 94.6 0.6 — 95.2 Cash balance at end of period $ — $ 108.6 $ 0.2 $ — $ 108.8 Consolidating Statement of Cash Flows The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Cash flows from operations: Net income including noncontrolling interests $ 24.1 $ 27.8 $ 10.7 $ (38.0 ) $ 24.6 Charges (credits) to reconcile net income to cash flows provided from (used for) operations: Undistributed earnings from subsidiaries (25.4 ) — (12.6 ) 38.0 — Net loss from discontinued operations — 0.1 — — 0.1 Net realized and change in unrealized investment gains — (14.2 ) — — (14.2 ) Net adjustment to gain on sale of business — 3.7 — — 3.7 Deferred income tax expense — 0.5 — — 0.5 Dividends received from subsidiaries 20.0 — — (20.0 ) — Other operating items: Net change in loss and LAE reserves — (38.2 ) — — (38.2 ) Net change in unearned premiums — 2.0 — — 2.0 Net change in ceded unearned premiums — (1.4 ) — — (1.4 ) Net change in premiums receivable — (16.6 ) — — (16.6 ) Net change in reinsurance recoverables on paid and unpaid losses — 14.0 — — 14.0 Net change in funds held under reinsurance contracts — 19.7 — — 19.7 Net change in funds held under insurance contracts — 12.0 — — 12.0 Net change in other assets and liabilities 2.8 12.1 2.3 — 17.2 Net cash provided from operations—continuing operations 21.5 21.5 0.4 (20.0 ) 23.4 Net cash used for operations—discontinued operations — (0.1 ) — — (0.1 ) Net cash provided from operations 21.5 21.4 0.4 (20.0 ) 23.3 Cash flows from investing activities: Net maturities, purchases and sales of short-term investments 0.1 8.1 (0.2 ) — 8.0 Maturities of fixed maturity investments — 32.9 — — 32.9 Sales of fixed maturity investments — 177.6 — — 177.6 Sales of common equity securities — 39.6 — — 39.6 Return of capital and distributions of other investments — 3.7 — — 3.7 Purchases of fixed maturity investments — (273.0 ) — — (273.0 ) Purchases of common equity securities — (26.2 ) — — (26.2 ) Contributions for other investments — (1.9 ) — — (1.9 ) Net change in unsettled investment purchases and sales — 40.3 — — 40.3 Net acquisitions of property and equipment — (0.4 ) — — (0.4 ) Net cash provided from (used for) investing activities 0.1 0.7 (0.2 ) — 0.6 Cash flows from financing activities: Cash dividends paid to common shareholders (20.0 ) — — — (20.0 ) Cash dividends paid to parent — (20.0 ) — 20.0 — Repurchases and retirements of common stock (1.6 ) — — — (1.6 ) Payments on capital lease obligation — (1.4 ) — — (1.4 ) Net cash used for financing activities (21.6 ) (21.4 ) — 20.0 (23.0 ) Net increase in cash during period — 0.7 0.2 — 0.9 Cash balance at beginning of period — 87.0 — — 87.0 Cash balance at end of period $ — $ 87.7 $ 0.2 $ — $ 87.9

Nature of Operations and Summ23

Nature of Operations and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
Recently Adopted Changes in Accounting Principles	Recently Adopted Changes in Accounting Principles Business Combinations - Measurement Period Adjustments Effective January 1, 2016, OneBeacon adopted ASU 2015-16, Simplifying the Accounting for Measurement-Period Adjustments, which requires adjustments to provisional amounts recorded in connection with a business combination that are identified during the measurement period are to be recorded in the reporting period in which the adjustment amounts are determined, rather than as retroactive adjustments to prior periods. OneBeacon has not recognized any adjustments to estimated purchase accounting amounts for the year to date period ended March 31, 2016 and accordingly, there was no effect to OneBeacon's financial statements upon adoption. Fair Value Measurements Effective January 1, 2016, OneBeacon adopted ASU 2015-07, Fair Value Measurement - Disclosures for Investments in Certain Entities that Calculate Net Asset Value per Share (or Its Equivalent) (ASC 820) which eliminates the requirement to disclose the fair value hierarchy level for investments for which fair value is measured at net asset value ("NAV") using the practical expedient in ASC 820. OneBeacon measures the fair value of its investments in hedge funds and private equity funds using this practical expedient. Upon adoption, these fair value measurements are no longer classified within the fair value hierarchy. Prior year amounts have been modified to conform to the current year's disclosures. Amendments to Consolidation Analysis On January 1, 2016, OneBeacon adopted ASU 2015-02, Amendments to the Consolidation Analysis (ASC 810) which amends the guidance for determining whether an entity is a variable interest entity (“VIE”). ASU 2015-02 eliminates the separate consolidation guidance for limited partnerships and with it, the presumption that a general partner should consolidate a limited partnership. In addition, ASU 2015-02 changes the guidance for determining if fee arrangements qualify as variable interests and the effect fee arrangements have on the determination of the primary beneficiary. Adoption of ASU 2015-02 did not affect the consolidation analysis for any of OneBeacon's investments. Share-Based Compensation Awards On January 1, 2016, OneBeacon adopted ASU 2014-12, Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period (ASC 718) . The new guidance requires that a performance target that affects vesting and that can be achieved after the requisite service period be treated as a performance condition. Compensation cost is to be recognized in the period when it becomes probable the performance target will be achieved in an amount equal to the compensation cost attributable to the periods for which service has been rendered. There was no effect to OneBeacon's financial statements upon adoption. Debt Issuance Costs Effective January 1, 2016, OneBeacon adopted ASU 2015-03, Imputation of Interest (ASC 835) which requires debt issuance costs to be presented as a deduction from the carrying amount of the related debt, consistent with the treatment required for debt discounts. The new guidance requires amortization of debt issuance costs to be classified within interest expense and also requires disclosure of the debt's effective interest rate. OneBeacon has applied the guidance retrospectively and as a result has reclassified $1.9 million of debt issuance costs from other assets, reflecting these amounts as reduction from the related debt and has modified its disclosures to include the required effective interest rate on its debt. Adoption of ASU 2015-03 did not have a material impact on OneBeacon's financial position, results of operations, or cash flows. In addition, effective January 1, 2016, OneBeacon adopted ASU 2015-15, Imputation of Interest (ASC 835), which addresses the presentation and subsequent measurement of debt issuance costs related to line-of-credit arrangements. Adoption of ASU 2015-15 did not have a significant effect on OneBeacon's financial position, results of operations, cash flows, presentation or disclosures. Recently Issued Accounting Pronouncements Stock Compensation On March 30, 2016, the Board issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (ASC 718) which is intended to simplify certain aspects of the accounting for share-based compensation. The new guidance provides an accounting policy election to account for forfeitures by either applying an assumption, as required under existing guidance, or by recognizing forfeitures when they actually occur. The new guidance is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods with early adoption permitted. OneBeacon does not expect a significant effect upon adoption. Leases On February 25, 2016, the FASB issued ASU 2016-02, Leases (ASC 842). The new guidance requires lessees to recognize lease assets and liabilities on the balance sheet for both operating and financing leases, with the exception of leases with an original term of 12 months or less. Under existing guidance recognition of lease assets and liabilities is not required for operating leases. The lease assets and liabilities to be recognized are both measured initially based on the present value of the lease payments. Under the new guidance, a sale-leaseback transaction must meet the recognition criteria under ASC 606, Revenues in order to be accounted for as sale. The new guidance is effective for OneBeacon for years beginning after December 15, 2018, including interim periods therein. OneBeacon is evaluating the expected impact of this new guidance and available adoption methods. Financial Instruments - Recognition and Measurement On January 5, 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (ASC 825-10). The new guidance requires all equity securities with readily determinable fair values to be measured at fair value with changes therein recognized through current period earnings. In addition, the new ASU simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment, and for impaired equity security investments to be measured at fair value. ASU 2016-01 is effective for fiscal years beginning after December 15, 2017, with early adoption permitted. OneBeacon has taken the fair value election for its portfolio of equity security investments and accordingly, does not expect the adoption of ASU 2016-01 to have a significant impact on its financial statements. Insurance Contracts In May 2015, the FASB issued ASU 2015-09, Disclosures about Short Duration Contracts (ASC 944) which requires expanded footnote disclosures about loss and loss adjustment expense ("LAE") reserves. Under the new guidance, some disclosures currently presented outside of OneBeacon’s financial statements, such as loss development tables and a reconciliation of loss development data to the loss and LAE reserves reflected on the balance sheet, will become part of the financial statement footnotes. In addition, the loss development tables required to be presented under the new ASU must be presented on a disaggregated basis by accident year rather than by reporting year as currently presented. Some of the expanded disclosures are new requirements, such as the disclosure of reserves for losses incurred but not reported ("IBNR") plus expected development on reported claims, which must be presented by accident year on a disaggregated basis. The new guidance also requires new disclosures about claim frequency data together with descriptions of the approach used to measure that data. Qualitative descriptions of methodologies and assumptions used to develop IBNR estimates must be presented together with the disaggregated amounts of IBNR to which they relate, along with a discussion of any significant changes in methodology and assumptions and the related effect upon the loss reserves. The new guidance will be effective for annual periods beginning after December 15, 2015 and interim periods within annual periods beginning after December 15, 2016 with retrospective restatement of prior periods required. OneBeacon will modify its financial statement footnote disclosures to conform to the requirements of ASU 2015-09 upon adoption, including revisions to prior year’s disclosures. Revenue Recognition In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (ASC 606) , which modifies the guidance for revenue recognition. The scope of the new ASU excludes insurance contracts but is applicable to certain fee arrangements, such as investment management fees. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (ASC 606), which delayed the effective date of ASU 2014-09 by one year. As a result, the standard is effective for annual and interim periods beginning after December 15, 2017. The Company is in the process of evaluating the new guidance and has not yet determined the potential effect of adoption on its financial position, results of operations, or cash flows.

Unpaid Loss and Loss Adjustme24

Unpaid Loss and Loss Adjustment Expense (LAE) Reserves (Tables)	3 Months Ended
	Mar. 31, 2016
Insurance Loss Reserves [Abstract]
Loss and loss adjustment expense (LAE) reserve activities	The following table summarizes the loss and LAE reserve activities of OneBeacon's insurance subsidiaries for the three months ended March 31, 2016 and 2015 : Three months ended ($ in millions) 2016 2015 Gross beginning balance $ 1,389.8 $ 1,342.2 Less beginning reinsurance recoverables on unpaid losses (186.0 ) (161.6 ) Net beginning loss and LAE reserves 1,203.8 1,180.6 Loss and LAE incurred relating to: Current year losses 158.8 167.7 Prior year losses — (1.8 ) Total incurred loss and LAE 158.8 165.9 Loss and LAE paid relating to: Current year losses (22.0 ) (22.1 ) Prior year losses (147.2 ) (162.0 ) Total loss and LAE payments (169.2 ) (184.1 ) Net ending loss and LAE reserves 1,193.4 1,162.4 Plus ending reinsurance recoverables on unpaid losses 150.4 141.6 Gross ending loss and LAE reserves $ 1,343.8 $ 1,304.0

Reinsurance (Tables)

Reinsurance (Tables)	3 Months Ended
	Mar. 31, 2016
Reinsurance Disclosures [Abstract]
Reinsurers	The following table summarizes Standard & Poor's Financial Services, LLC ("Standard & Poor's") ratings for OneBeacon's reinsurers, excluding industry pools and associations, based upon reinsurance recoverable amounts on paid and unpaid losses and LAE: Balance at March 31, 2016 % of total Standard & Poor's Rating (1) : ($ in millions) AA $ 42.7 26 % A 98.2 59 % BBB, Not Rated and Other (2) 26.1 15 % Total reinsurance recoverables $ 167.0 100 % _______________________________________________________________________________ (1) Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB" (Adequate). (2) Includes reinsurance recoverable on unpaid losses from Bedivere of $19.4 million .

Investment Securities (Tables)

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2016
Investment Holdings [Line Items]
Other Investments Not Readily Marketable [Table Text Block]	As of both March 31, 2016 and December 31, 2015 , other investments reported at fair value represented approximately 5% of the total investment portfolio and consisted of the following: ($ in millions) March 31, December 31, Hedge funds (1) $ 16.2 $ 16.4 Private equity funds (2) 41.3 46.1 Total hedge funds and private equity funds 57.5 62.5 Surplus notes (par value $101.0) (3) 51.8 51.5 Investment in community reinvestment vehicle 14.4 14.3 Total other investments (4) $ 123.7 $ 128.3 _______________________________________________________________________________ (1) Consists of 4 hedge funds as of both March 31, 2016 and December 31, 2015 . (2) Consists of 17 private equity funds as of both March 31, 2016 and December 31, 2015 . (3) The increase in the fair value of the surplus notes during the three months ended March 31, 2016 was primarily due to the time value of money benefit generated by moving one quarter closer to modeled cash receipts, offset by the negative valuation impact of an interest payment received in the first quarter of 2016. (4) Excludes the carrying value of $14.1 million and $14.7 million as of March 31, 2016 and December 31, 2015 , respectively, associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method.
Net investment income, pre-tax	Net investment income for the three months ended March 31, 2016 and 2015 consisted of the following: Three months ended ($ in millions) 2016 2015 Fixed maturity investments $ 12.1 $ 10.2 Common equity securities 1.0 1.6 Other investments (1) 2.5 0.1 Gross investment income 15.6 11.9 Less external investment expenses (1.2 ) (1.4 ) Net investment income, pre-tax $ 14.4 $ 10.5 _______________________________________________________________________________ (1) Includes an interest payment on the surplus notes of $2.4 million received in the three months ended March 31, 2016 .
Net realized and unrealized investment gains (losses), pre-tax	The composition of net realized investment gains (losses) consisted of the following: Three months ended ($ in millions) 2016 2015 Fixed maturity investments $ (1.4 ) $ 0.7 Common equity securities (4.7 ) 9.8 Other investments 0.2 (1.0 ) Net realized investment gains (losses), pre-tax $ (5.9 ) $ 9.5
Net unrealized investment gains (losses)	The net changes in net unrealized gains for the three months ended March 31, 2016 and 2015 are as follows: Three months ended March 31, 2016 ($ in millions) Changes in net unrealized investment gains Changes in net foreign currency gains (losses) Total net changes in unrealized gains reflected in revenues Fixed maturity investments $ 15.0 $ — $ 15.0 Common equity securities 9.7 — 9.7 Other investments (2.2 ) — (2.2 ) Net change, pre-tax $ 22.5 $ — $ 22.5 Three months ended March 31, 2015 ($ in millions) Changes in net unrealized investment gains Changes in net foreign currency gains (losses) Total net changes in unrealized gains reflected in revenues Fixed maturity investments $ 6.6 $ — $ 6.6 Common equity securities (4.4 ) (0.1 ) (4.5 ) Other investments 2.6 — 2.6 Net change, pre-tax $ 4.8 $ (0.1 ) $ 4.7
Gross unrealized investment gains or losses	The components of OneBeacon's ending net unrealized investment gains and losses, excluding the impact of net unrealized foreign currency translation gains and losses, on its investment portfolio as of March 31, 2016 and December 31, 2015 were as follows: ($ in millions) March 31, December 31, Investment securities: Gross unrealized investment gains $ 63.5 $ 46.5 Gross unrealized investment losses (27.7 ) (33.2 ) Total net unrealized investment gains, pre-tax 35.8 13.3 Income taxes (12.4 ) (6.5 ) Total net unrealized investment gains, after-tax $ 23.4 $ 6.8
Investment holdings, fixed maturity investments	The cost or amortized cost, gross unrealized pre-tax investment gains and losses, net foreign currency losses and carrying values of OneBeacon's fixed maturity investments as of March 31, 2016 and December 31, 2015 were as follows: March 31, 2016 ($ in millions) Cost or amortized cost Gross unrealized gains Gross unrealized losses Net unrealized foreign currency gains (losses) Carrying value U.S. Government and agency obligations $ 53.5 $ 0.1 $ — $ — $ 53.6 Debt securities issued by corporations 733.3 11.2 (0.9 ) — 743.6 Municipal obligations 67.6 1.8 (0.1 ) — 69.3 Mortgage and asset-backed securities 1,077.8 3.7 (3.7 ) — 1,077.8 Foreign government obligations 1.0 0.2 — — 1.2 Preferred stocks 78.3 4.9 — — 83.2 Total fixed maturity investments $ 2,011.5 $ 21.9 $ (4.7 ) $ — $ 2,028.7 December 31, 2015 ($ in millions) Cost or amortized cost Gross unrealized gains Gross unrealized losses Net unrealized foreign Carrying value U.S. Government and agency obligations $ 85.4 $ — $ (0.1 ) $ — $ 85.3 Debt securities issued by corporations 810.8 4.1 (4.5 ) — 810.4 Municipal obligations 67.7 1.5 (0.2 ) — 69.0 Mortgage and asset-backed securities 1,035.1 1.3 (4.5 ) — 1,031.9 Foreign government obligations 1.0 0.2 — — 1.2 Preferred stocks 78.3 4.4 — — 82.7 Total fixed maturity investments $ 2,078.3 $ 11.5 $ (9.3 ) $ — $ 2,080.5
Investment holdings, common equity securities, convertible fixed maturity investments and other investments	The cost or amortized cost, gross unrealized pre-tax investment gains and losses, net unrealized pre-tax foreign currency losses and carrying values of common equity securities and other investments as of March 31, 2016 and December 31, 2015 were as follows: March 31, 2016 ($ in millions) Cost or amortized cost Gross unrealized gains Gross unrealized losses Net unrealized foreign Carrying value Common equity securities $ 262.5 $ 19.4 $ (6.0 ) $ — $ 275.9 Other investments 132.6 22.2 (17.0 ) — 137.8 Total common equity securities and other investments $ 395.1 $ 41.6 $ (23.0 ) $ — $ 413.7 December 31, 2015 ($ in millions) Cost or amortized cost Gross unrealized gains Gross unrealized losses Net unrealized foreign Carrying value Common equity securities $ 295.0 $ 12.7 $ (9.0 ) $ — $ 298.7 Other investments 135.6 22.3 (14.9 ) — 143.0 Total common equity securities and other investments $ 430.6 $ 35.0 $ (23.9 ) $ — $ 441.7
Fair value measurements by level, investment securities	The following tables summarize the Company's fair value measurements for investments as of March 31, 2016 and December 31, 2015 by level. The major security types were based on the legal form of the securities. OneBeacon has disaggregated its fixed maturity investments based on the issuing entity type, which impacts credit quality, with debt securities issued by U.S. government entities carrying minimal credit risk, while the credit and other risks associated with other issuers, such as corporations, foreign governments, municipalities or entities issuing asset-backed securities vary depending on the nature of the issuing entity type. OneBeacon further disaggregates debt securities issued by corporations and common equity securities by industry sector because investors often reference commonly used benchmarks and their subsectors to monitor risk and performance. Accordingly, OneBeacon has further disaggregated these asset classes into subclasses based on the similar sectors and industry classifications the Company uses to evaluate investment risk and performance against commonly used benchmarks, such as the Barclays Intermediate Aggregate and S&P 500 indices. ($ in millions) Fair value at Level 1 Level 2 Level 3 Fixed maturity investments: U.S. Government and agency obligations $ 53.6 $ 53.6 $ — $ — Debt securities issued by corporations: Consumer 211.6 — 211.6 — Industrial 122.5 — 122.5 — Healthcare 109.5 — 109.5 — Financials 108.4 — 108.4 — Energy 59.8 — 59.8 — Utilities 42.1 — 42.1 — Communications 40.1 — 40.1 — Technology 28.9 — 28.9 — Basic materials 20.7 — 20.7 — Debt securities issued by corporations 743.6 — 743.6 — Municipal obligations 69.3 — 69.3 — Mortgage and asset-backed securities 1,077.8 — 1,077.8 — Foreign government obligations 1.2 0.7 0.5 — Preferred stocks 83.2 — 12.7 70.5 Fixed maturity investments 2,028.7 54.3 1,903.9 70.5 Short-term investments 119.7 119.7 — — Common equity securities: Exchange traded funds (1) 130.5 109.0 21.5 — Consumer 46.7 46.7 — — Technology 29.0 29.0 — — Healthcare 24.4 24.4 — — Communications 20.3 20.3 — — Industrial 17.0 17.0 — — Financials 8.0 8.0 — — Common equity securities 275.9 254.4 21.5 — Other investments (2)(3) 123.7 — — 66.3 Total (1)(2) $ 2,548.0 $ 428.4 $ 1,925.4 $ 136.8 _______________________________________________________________________________ (1) ETF's traded on foreign exchanges are priced using the fund's published NAV to account for the difference in market close times and are therefore designated as level 2 measurements. (2) Excludes the carrying value of $14.1 million associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method as of March 31, 2016 . (3) As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies" investments in hedge funds and private equity funds of $57.4 million measured at fair value for which NAV is the practical expedient are no longer classified within the fair value hierarchy. ($ in millions) Fair value at Level 1 Level 2 Level 3 Fixed maturity investments: U.S. Government and agency obligations $ 85.3 $ 85.3 $ — $ — Debt securities issued by corporations: Consumer 218.3 — 218.3 — Healthcare 136.2 — 136.2 — Industrial 121.8 — 121.8 — Financials 116.0 — 116.0 — Energy 75.2 — 75.2 — Communications 46.0 — 46.0 — Utilities 42.2 — 42.2 — Technology 28.9 — 28.9 — Basic materials 25.8 — 25.8 — Debt securities issued by corporations 810.4 — 810.4 — Municipal obligations 69.0 — 69.0 — Mortgage and asset-backed securities 1,031.9 — 1,031.9 — Foreign government obligations 1.2 0.6 0.6 — Preferred stocks 82.7 — 12.7 70.0 Fixed maturity investments 2,080.5 85.9 1,924.6 70.0 Short-term investments 69.2 69.2 — — Common equity securities: Exchange traded funds (1) 183.3 162.0 21.3 — Consumer 38.2 38.2 — — Communications 23.9 23.9 — — Healthcare 19.6 19.6 — — Technology 14.7 14.7 — — Industrial 14.5 14.5 — — Financials 4.5 4.5 — — Common equity securities 298.7 277.4 21.3 — Other investments (2)(3) 128.3 — — 65.9 Total (1)(2)(3) $ 2,576.7 $ 432.5 $ 1,945.9 $ 135.9 _______________________________________________________________________________ (1) ETF's traded on foreign exchanges are priced using the fund's published NAV to account for the difference in market close times and are therefore designated as level 2 measurements. (2) Excludes the carrying value of $14.7 million associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method as of December 31, 2015 .
Debt securities, credit ratings	The following table summarizes the ratings of the debt securities issued by corporations owned by OneBeacon as of March 31, 2016 and December 31, 2015 : at Fair value ($ in millions) March 31, December 31, AAA (1) $ 2.6 $ — AA (1) 63.7 42.7 A (1) 252.2 265.4 BBB (1) 425.1 502.3 Debt securities issued by corporations (1) $ 743.6 $ 810.4 _______________________________________________________________________________ (1) Credit ratings are assigned based on the following hierarchy: 1) Standard and Poor’s Financial Services LLC (“Standard and Poor’s”) and 2) Moody’s Investor Service (“Moody’s”).
Fair Value Assets Measured on Recurring Basis Measurement Input Reconciliation	The following tables summarize the changes in OneBeacon’s fair value measurements by level for the three months ended March 31, 2016 and 2015 : Level 3 Investments ($ in millions) Level 1 Investments Level 2 Investments Fixed maturity investments Common equity securities Other investments (1) NAV investments (2) Total (1)(2)(3) Balance at January 1, 2016 $ 363.3 $ 1,945.9 $ 70.0 $ — $ 65.9 $ 62.4 $ 2,507.5 Amortization/accretion — (3.2 ) — — — — (3.2 ) Net realized and unrealized gains 5.6 12.5 0.5 — 0.4 (2.3 ) 16.7 Purchases 98.2 187.0 — — — 0.3 285.5 Sales (158.4 ) (216.8 ) — — — (3.0 ) (378.2 ) Transfers in — — — — — — — Transfers out — — — — — — — Balance at March 31, 2016 $ 308.7 $ 1,925.4 $ 70.5 $ — $ 66.3 $ 57.4 $ 2,428.3 _______________________________________________________________________________ (1) Excludes the carrying value of $14.1 million associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method as of March 31, 2016. (2) As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies" investments in hedge funds and private equity funds measured using the NAV practical expedient are no longer classified within the fair value hierarchy. (3) Excludes short-term investments. Level 3 Investments ($ in millions) Level 1 Investments Level 2 Investments Fixed maturity investments Common equity securities Other investments (1) NAV investments (2) Total (1)(2)(3) Balance at January 1, 2015 $ 358.7 $ 1,692.1 $ 74.0 $ — $ 79.6 102.4 $ 2,306.8 Amortization/accretion — (2.9 ) — — — — (2.9 ) Net realized and unrealized gains 5.5 7.3 0.3 — 3.1 (1.9 ) 14.3 Purchases 62.4 208.7 28.4 — — 1.4 300.9 Sales (75.2 ) (175.4 ) — — (0.1 ) (2.9 ) (253.6 ) Transfers in — 2.9 — — — — 2.9 Transfers out — — (2.9 ) — — — (2.9 ) Balance at March 31, 2015 $ 351.4 $ 1,732.7 $ 99.8 $ — $ 82.6 $ 99.0 $ 2,365.5 _______________________________________________________________________________ (1) Excludes the carrying value of $16.2 million associated with a tax advantaged federal affordable housing development fund accounted for using the proportional amortization method as of March 31, 2015. (2) As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies" investments in hedge funds and private equity funds measured using the NAV practical expedient are no longer classified within the fair value hierarchy. (3) Excludes short-term investments.
Fair value, significant unobservable inputs	The following summarizes significant unobservable inputs used in estimating the fair value of fixed maturity and other investments classified within Level 3, as of March 31, 2016 and December 31, 2015 . ($ in millions) As of March 31, 2016 Description Fair Value (in millions) Rating (1) Valuation Technique Unobservable Inputs Input Preferred stock (2) $ 70.5 N/R Discounted cash flow Discount yield 8.1% Surplus notes: 15.8% - Seller priority note $ 38.2 N/R Discounted cash flow Discount rate (3) 12.5% Timing of interest payments (4) 5 years Timing of principal payments (4) 10 years - Pari passu note $ 13.6 N/R Discounted cash flow Discount rate (5) 22.5% Timing of interest payments (4) 5 years Timing of principal payments (4) 15 years ($ in millions) As of December 31, 2015 Description Fair Value (in millions) Rating (1) Valuation Technique Unobservable Inputs Input Preferred stock (2) $ 70.0 N/R Par value (6) Issuer's intent to call $70.0 Surplus notes: 16.1% - Seller priority note $ 38.0 N/R Discounted cash flow Discount rate (3) 13.0% Timing of interest payments (4) 5 years Timing of principal payments (4) 10 years - Pari passu note $ 13.5 N/R Discounted cash flow Discount rate (5) 22.4% Timing of interest payments (4) 5 years Timing of principal payments (4) 15 years _________________________________________________________________________ (1) Credit ratings, if rated, are assigned based on the following hierarchy: 1) Standard & Poor's and 2) Moody's (2) As of March 31, 2016 and December 31, 2015 , asset type consists of one security. (3) Stochastic modeling supporting the fair value estimation indicates that the average percentage of discounted payments missed on the seller priority note is roughly equivalent to that of a conventional debt security with a credit rating of ‘B’. The corresponding credit spread increased by an additional 250 bps to reflect both a liquidity discount for a private debt instrument and regulatory payment approval uncertainty, which was added to the treasury rate to determine the discount rate for the seller priority note. (4) As of March 31, 2016 and December 31, 2015 , the Company assumed for the purpose of estimating the fair value that future interest payouts begin in year five (2020) and principal repayments begin on a graduated basis in year ten (2025) for the seller priority note and year fifteen (2030) for the pari passu note. (5) Stochastic modeling supporting the fair value estimation indicates that the average percentage of discounted payments missed on the pari passu note is roughly equivalent to that of a conventional debt security with a credit rating of ‘CCC’. The corresponding credit spread increased by an additional 250 bps to reflect both a liquidity discount for a private debt instrument and regulatory payment approval uncertainty, which was added to the treasury rate to determine the discount rate for the pari passu note. (6) Valuation based on issuer's intent as of December 31, 2015 to call the security in the near term.
Net unrealized gains or losses for Level 3 investments	The following table summarizes the change in net pre-tax unrealized gains or losses for assets designated as Level 3 for the three months ended March 31, 2016 and 2015 : Three months ended ($ in millions) 2016 2015 Fixed maturity investments $ 0.5 $ 0.3 Other investments 0.4 3.0 Total $ 0.9 $ 3.3
Mortgage-backed and asset-backed securities	The following table summarizes the carrying value of OneBeacon's asset-backed securities as of March 31, 2016 and December 31, 2015 : March 31, 2016 December 31, 2015 ($ in millions) Fair Value Level 2 Level 3 Fair Value Level 2 Level 3 Mortgage-backed securities: Agency: GNMA $ 216.0 $ 216.0 $ — $ 220.5 $ 220.5 $ — FNMA 1.4 1.4 — 1.4 1.4 — FHLMC 2.9 2.9 — 3.1 3.1 — Total agency (1) 220.3 220.3 — 225.0 225.0 — Non-agency: Residential 131.8 131.8 — 132.7 132.7 — Commercial 128.8 128.8 — 140.4 140.4 — Total Non-agency 260.6 260.6 — 273.1 273.1 — Total mortgage-backed securities 480.9 480.9 — 498.1 498.1 — Other asset-backed securities: Credit card receivables 249.3 249.3 — 202.7 202.7 — Vehicle receivables 265.0 265.0 — 255.6 255.6 — Other 82.6 82.6 — 75.5 75.5 — Total other asset-backed securities 596.9 596.9 — 533.8 533.8 — Total mortgage-backed and asset-backed securities $ 1,077.8 $ 1,077.8 $ — $ 1,031.9 $ 1,031.9 $ — _______________________________________________________________________________ (1) Represents publicly traded mortgage-backed securities which carry the full faith and credit guarantee of the U.S. government (i.e., GNMA) or are guaranteed by a government sponsored entity (i.e., FNMA, FHLMC).
Schedule of security issuance years of investments in non-agency RMBS and non-agency CMBS securities	The security issuance years of OneBeacon's investments in non-agency RMBS and non-agency CMBS securities as of March 31, 2016 are as follows: Fair Value Security Issuance Year ($ in millions) 2004 2005 2006 2008 2010 2011 2012 2013 2014 2015 Total non-agency RMBS $ 131.8 $ 22.8 $ 8.1 $ 3.6 $ 3.4 $ 13.1 $ 12.6 $ 9.3 $ 13.2 $ 45.7 $ — Total non-agency CMBS 128.8 — — — — 5.2 — 18.3 15.4 44.8 45.1 Total non-agency $ 260.6 $ 22.8 $ 8.1 $ 3.6 $ 3.4 $ 18.3 $ 12.6 $ 27.6 $ 28.6 $ 90.5 $ 45.1
Non-agency RMBS, collateral quality and tranche levels	The classification of the underlying collateral quality and the tranche levels of OneBeacon's non-agency RMBS securities are as follows as of March 31, 2016 : ($ in millions) Fair Value Super Senior (1) Senior (2) Subordinate (3) Prime $ 124.4 $ 63.1 $ 61.3 $ — Non-prime 7.4 — 7.4 — Total non-agency RMBS $ 131.8 $ 63.1 $ 68.7 $ — _______________________________________________________________________________ (1) At issuance, Super Senior, or in the case of resecuritization, the underlying securities, were rated AAA by Standard & Poor's, Aaa by Moody's, or AAA by Fitch Ratings ("Fitch") and were senior to other AAA or Aaa securities. (2) At issuance, Senior, or in the case of resecuritization, the underlying securities, were rated AAA by Standard & Poor's, Aaa by Moody's, or AAA by Fitch and were senior to non-AAA or non-Aaa securities. (3) At issuance, Subordinate were not rated AAA by Standard & Poor's, Aaa by Moody's, or AAA by Fitch and were junior to other AAA or Aaa securities.
Non-agency CMBS, type of interest rate and tranche levels	The amount of fixed and floating rate securities and their tranche levels of OneBeacon's non-agency CMBS securities are as follows as of March 31, 2016 : ($ in millions) Fair Value Super Senior (1) Senior (2) Subordinate (3) Fixed rate CMBS $ 96.0 $ 8.8 $ 46.0 $ 41.2 Floating rate CMBS 32.8 — — 32.8 Total non-agency CMBS $ 128.8 $ 8.8 $ 46.0 $ 74.0 _______________________________________________________________________________ (1) At issuance, Super Senior, or in the case of resecuritization, the underlying securities, were rated AAA by Standard & Poor's, Aaa by Moody's or AAA by Fitch and were senior to other AAA or Aaa securities. (2) At issuance, Senior, or in the case of resecuritization, the underlying securities, were rated AAA by Standard & Poor's, Aaa by Moody's, or AAA by Fitch and were senior to non-AAA or non-Aaa securities. (3) At issuance, Subordinate were not rated AAA by Standard & Poor's, Aaa by Moody's, or AAA by Fitch and were junior to other AAA or Aaa securities.
Other investments	The following table summarizes investments in hedge funds and private equity funds as of March 31, 2016 and December 31, 2015 : March 31, 2016 December 31, 2015 ($ in millions) Fair Value Unfunded Commitments Fair Value Unfunded Commitments Hedge funds Long/short equity banks and financial $ 12.7 $ — $ 12.8 $ — Other 3.5 — 3.6 — Total hedge funds 16.2 — 16.4 — Private equity funds Energy infrastructure and services 18.0 3.2 20.7 3.4 Multi-sector 13.0 2.1 14.8 2.1 Private equity secondaries 4.0 2.1 4.4 2.1 Healthcare 3.8 0.4 3.8 0.4 Insurance 2.0 0.1 2.0 0.1 Real estate 0.5 0.1 0.4 0.1 Total private equity funds 41.3 8.0 46.1 8.2 Total hedge funds and private equity funds $ 57.5 $ 8.0 $ 62.5 $ 8.2
Fair value of hedge funds subject to restrictions on redemption frequency and advance notice period requirements for investments in active hedge funds	The following summarizes the March 31, 2016 fair value of hedge funds subject to restrictions on redemption frequency and advance notice period requirements for investments in active hedge funds: Hedge Funds Notice Period ($ in millions) 30 - 59 days notice 60 - 89 days notice 90 - 119 days notice 120+ days notice Total Redemption frequency Monthly $ — $ — $ — $ — $ — Quarterly 13.7 — — — 13.7 Annual — — 2.5 — 2.5 Total hedge funds $ 13.7 $ — $ 2.5 $ — $ 16.2
Fair Value of private equity funds subject to lock-up periods	As of March 31, 2016 , investments in private equity funds were subject to lock-up periods as follows: ($ in millions) 1 - 3 years 3 - 5 years 5 - 10 years >10 years Total Private Equity Funds—expected lock-up period remaining $ 26.3 $ 3.8 $ 11.2 $ — $ 41.3

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2016
Debt Disclosure [Abstract]
Schedule of debt outstanding	OneBeacon's debt outstanding as of March 31, 2016 and December 31, 2015 consisted of the following: ($ in millions) March 31, December 31, Senior unsecured notes, at face value $ 275.0 $ 275.0 Unamortized original issue discount (0.2 ) (0.2 ) Unamortized issuance costs (1) (1.9 ) (1.9 ) Senior unsecured notes, carrying value $ 272.9 $ 272.9

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Financial information for OneBeacon's segments	Financial information for OneBeacon's reportable segments is as follows: Insurance Operations Investing, Financing and Corporate ($ in millions) Specialty Products Specialty Industries Consolidated Three months ended March 31, 2016 Earned premiums $ 133.4 $ 145.2 $ — $ 278.6 Loss and loss adjustment expense (91.8 ) (67.0 ) — (158.8 ) Policy acquisition expenses (24.0 ) (27.0 ) — (51.0 ) Other underwriting expenses (23.4 ) (31.9 ) — (55.3 ) Total underwriting income (loss) (5.8 ) 19.3 — 13.5 Net investment income — — 14.4 14.4 Net realized and change in unrealized investment gains — — 16.6 16.6 Net other revenues (expenses) (0.1 ) 0.3 0.7 0.9 General and administrative expenses — (0.5 ) (3.4 ) (3.9 ) Interest expense — — (3.3 ) (3.3 ) Pre-tax income (loss) from continuing operations $ (5.9 ) $ 19.1 $ 25.0 $ 38.2 Three months ended March 31, 2015 Earned premiums $ 136.1 $ 150.5 $ — $ 286.6 Loss and loss adjustment expense (74.1 ) (91.8 ) — (165.9 ) Policy acquisition expenses (22.9 ) (28.1 ) — (51.0 ) Other underwriting expenses (25.7 ) (30.2 ) — (55.9 ) Total underwriting income 13.4 0.4 — 13.8 Net investment income — — 10.5 10.5 Net realized and change in unrealized investment gains — — 14.2 14.2 Net other revenues (expenses) — 0.2 (3.3 ) (3.1 ) General and administrative expenses — (0.5 ) (3.6 ) (4.1 ) Interest expense — — (3.2 ) (3.2 ) Pre-tax income from continuing operations $ 13.4 $ 0.1 $ 14.6 $ 28.1
Schedule of selected balance sheet of the segments	Insurance Operations Investing, Financing and Corporate ($ in millions) Specialty Products Specialty Industries Consolidated March 31, 2016 Assets Total investment securities $ — $ — $ 2,562.1 $ 2,562.1 Premiums receivable 86.9 143.5 — 230.4 Reinsurance recoverables (1) 113.6 34.0 19.4 167.0 Deferred acquisition costs 52.9 49.1 — 102.0 Ceded unearned premiums 25.4 10.9 — 36.3 Other assets 1.1 0.1 430.0 431.2 Total Assets $ 279.9 $ 237.6 $ 3,011.5 $ 3,529.0 Liabilities Unpaid loss and loss adjustment expense reserves (1) $ 730.7 $ 593.7 $ 19.4 $ 1,343.8 Unearned premiums 305.7 262.9 — 568.6 Funds held under insurance contracts 134.9 — — 134.9 Debt — — 272.9 272.9 Other liabilities — — 189.0 189.0 Total Liabilities $ 1,171.3 $ 856.6 $ 481.3 $ 2,509.2 December 31, 2015 Assets Total investment securities $ — $ — $ 2,591.4 $ 2,591.4 Premiums receivable 63.0 156.0 — 219.0 Reinsurance recoverables (1) 139.5 33.6 20.4 193.5 Deferred acquisition costs 49.6 51.1 — 100.7 Ceded unearned premiums 19.2 10.3 — 29.5 Other assets 0.9 0.1 467.5 468.5 Total Assets $ 272.2 $ 251.1 $ 3,079.3 $ 3,602.6 Liabilities Unpaid loss and loss adjustment expense reserves (1) $ 772.2 $ 597.2 $ 20.4 $ 1,389.8 Unearned premiums 288.1 272.2 — 560.3 Funds held under insurance contracts 137.7 — — 137.7 Debt — — 272.9 272.9 Other liabilities — — 237.4 237.4 Total Liabilities $ 1,198.0 $ 869.4 $ 530.7 $ 2,598.1
Schedule of net written premiums, earned premiums and ratios for OneBeacon's insurance operations by segment and in total, as well as for the three major underwriting units within Specialty Insurance Operations	The following tables provide net written premiums, earned premiums and underwriting ratios for OneBeacon's insurance operations by reportable segment and in total, for the three months ended March 31, 2016 and 2015 : Three months ended March 31, 2016 Three months ended March 31, 2015 ($ in millions) Specialty Products Specialty Industries Consolidated Specialty Specialty Consolidated Net written premiums $ 144.7 $ 135.4 $ 280.1 $ 133.6 $ 153.5 $ 287.1 Earned premiums 133.4 145.2 278.6 136.1 150.5 286.6 Underwriting ratios: (1) Loss and LAE 68.8 % 46.1 % 57.0 % 54.4 % 61.0 % 57.9 % Expense 35.6 40.5 38.2 35.8 38.7 37.3 Total combined ratio 104.4 % 86.6 % 95.2 % 90.2 % 99.7 % 95.2 % _______________________________________________________________________________ (1) Underwriting ratios are used to measure the components of underwriting profitability and include: the loss and LAE ratio, calculated by dividing loss and LAE by earned premiums; the expense ratio, calculated by dividing policy acquisition and other underwriting expenses by earned premiums; and the combined ratio, the sum of the loss and LAE ratio and the expense ratio.

Retirement Plans (Tables)

Retirement Plans (Tables)	3 Months Ended
	Mar. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Schedule of components of net periodic benefit cost (income)	The components of net periodic benefit cost for the three months ended March 31, 2016 and 2015 for the Non-qualified Plan and Qualified Plan were as follows: Three months ended ($ in millions) 2016 2015 Service cost $ 0.2 $ 0.2 Interest cost 0.8 1.2 Expected return on plan assets (1.0 ) (2.2 ) Amortization of unrecognized loss 0.3 0.3 Net periodic pension cost (income) 0.3 (0.5 ) Settlement loss (1) 0.3 — Total net periodic benefit cost (income) $ 0.6 $ (0.5 ) _______________________________________________________________________________ (1) Represents the impact of the termination of the Qualified Pension Plan during

Employee Share-Based Incentiv30

Employee Share-Based Incentive Compensation Plans (Tables)	3 Months Ended
	Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of performance share activity	The following summarizes performance share activity for the three months ended March 31, 2016 and 2015 : Three months ended March 31, 2016 2015 ($ in millions) Target Performance Shares outstanding Accrued expense Target Performance Shares outstanding Accrued expense Beginning of period 449,435 $ 1.4 517,470 $ 3.4 Payments and deferrals (1) (167,300 ) (0.7 ) (181,290 ) (1.5 ) New awards 163,150 — 154,887 — Forfeitures and net change in assumed forfeitures (4,079 ) — (28,920 ) — Expense recognized — 0.4 — 0.2 End of period 441,206 $ 1.1 462,147 $ 2.1 _______________________________________________________________________________ (1) Performance share payments in 2016 for the 2013-2015 performance cycle were based upon a performance factor of 24.3% . Performance share payments in 2015 for the 2012-2014 performance cycle were based upon a performance factor of 45.7% .
Summary of performance shares outstanding and accrued expense for performance shares awarded under the OB Incentive Plan	The following summarizes performance shares outstanding and accrued performance share expense at March 31, 2016 for each performance cycle: ($ in millions) Target OB Performance Shares outstanding Accrued expense Performance cycle: 2014 - 2016 142,710 $ 0.1 2015 - 2017 146,659 0.8 2016 - 2018 163,150 0.2 Subtotal 452,519 1.1 Assumed forfeitures (11,313 ) — Total at March 31, 2016 441,206 $ 1.1
Summary of restricted shares activity	The following summarizes restricted shares activity for the three months ended March 31, 2016 and 2015 : Three months ended March 31, 2016 2015 ($ in millions) Restricted Shares Unamortized Issue Date Fair Value Restricted Shares Unamortized Issue Date Fair Value Beginning of period 382,722 $ 2.5 612,500 $ 3.5 New awards 170,650 2.3 75,950 1.1 Forfeitures — — (1,500 ) — Vested (157,500 ) — (296,000 ) — Expense recognized — (0.5 ) — (0.6 ) End of period 395,872 $ 4.3 390,950 $ 4.0

Earnings (loss) per Share (Tabl

Earnings (loss) per Share (Tables)	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Schedule of computation of earnings per share	The following table outlines the Company's computation of earnings per share for net income from continuing operations attributable to OneBeacon's common shareholders for the three months ended March 31, 2016 and 2015 : Three months ended 2016 2015 Earnings attributable to OneBeacon's common shareholders—basic and diluted (in millions): Net income from continuing operations attributable to OneBeacon's common shareholders $ 46.4 $ 24.2 Allocation of income for participating unvested restricted common shares (0.2 ) (0.1 ) Dividends paid on participating restricted common shares — (0.1 ) Total allocation to restricted common shares (0.2 ) (0.2 ) Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts $ 46.2 $ 24.0 Undistributed net earnings (in millions): Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts $ 46.2 $ 24.0 Dividends paid, net of restricted common share amounts (19.8 ) (19.9 ) Total undistributed net earnings, net of restricted common share amounts $ 26.4 $ 4.1 Earnings per share denominator—basic and diluted (in millions): Total weighted average common shares outstanding 94.5 95.3 Weighted average unvested restricted common shares (1) (0.4 ) (0.5 ) Basic and diluted earnings per share denominator 94.1 94.8 Earnings per share attributable to OneBeacon's common shareholders—basic and diluted (in dollars): Net income from continuing operations attributable to OneBeacon's common shareholders $ 0.49 $ 0.25 Dividends declared and paid (0.21 ) (0.21 ) Undistributed earnings $ 0.28 $ 0.04 _______________________________________________________________________________ (1) Restricted shares outstanding vest in equal installments upon a stated date or upon the occurrence of a specified event.

Common Shareholders' Equity Com

Common Shareholders' Equity Common Shareholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2016
Accumulated Other Comprehensive Income [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The pre-tax components of the Company's other comprehensive income and the related tax expense are as follows: Three months ended March 31, ($ in millions) 2016 2015 Net change in benefit plan assets and obligations $ — $ 0.3 Income tax expense — (0.1 ) Net change in benefit plan assets and obligations, net of tax $ — $ 0.2

Consolidating Financial Infor33

Consolidating Financial Information (Tables)	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidating Balance Sheet	The following tables present OneBeacon's consolidating balance sheets as of March 31, 2016 and December 31, 2015 and statements of operations and comprehensive income for the three months ended March 31, 2016 and 2015 and cash flows for the three months ended March 31, 2016 and 2015 . These financial statements reflect the Company's ("guarantor") financial position, results of operations and cash flows on a stand-alone basis, that of OBH ("the issuer") and of the Company's other entities ("non-guarantor subsidiaries") as well as the necessary consolidating adjustments to eliminate intercompany balances and transactions. Consolidating Balance Sheet As of March 31, 2016 (in millions) The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Assets Investment Securities: Fixed maturity investments, at fair value $ — $ 2,028.7 $ — $ — $ 2,028.7 Short-term investments, at amortized cost (which approximates fair value) 4.2 115.4 0.1 — 119.7 Common equity securities, at fair value — 275.9 — — 275.9 Other investments — 137.8 — — 137.8 Total investment securities 4.2 2,557.8 0.1 — 2,562.1 Cash — 108.6 0.2 — 108.8 Reinsurance recoverables — 167.0 — — 167.0 Premiums receivable — 230.4 — — 230.4 Deferred acquisition costs — 102.0 — — 102.0 Ceded unearned premiums — 36.3 — — 36.3 Net deferred tax asset — 134.0 — 0.1 134.1 Investment income accrued — 9.4 — — 9.4 Accounts receivable on unsettled investment sales — 4.5 — — 4.5 Investments in subsidiaries 1,013.5 — 982.8 (1,996.3 ) — Other assets 0.2 171.4 2.8 — 174.4 Total assets $ 1,017.9 $ 3,521.4 $ 985.9 $ (1,996.2 ) $ 3,529.0 Liabilities Unpaid loss and loss adjustment expense reserves $ — $ 1,343.8 $ — $ — $ 1,343.8 Unearned premiums — 568.6 — — 568.6 Funds held under insurance contracts — 134.9 — — 134.9 Debt — — 272.9 — 272.9 Accounts payable on unsettled investment purchases — 1.5 — — 1.5 Other liabilities 1.3 177.1 9.1 — 187.5 Total liabilities 1.3 2,225.9 282.0 — 2,509.2 OneBeacon's common shareholders' equity and noncontrolling interests Total OneBeacon's common shareholders' equity 1,016.6 1,292.3 703.9 (1,996.2 ) 1,016.6 Total noncontrolling interests — 3.2 — — 3.2 Total OneBeacon's common shareholders' equity and noncontrolling interests 1,016.6 1,295.5 703.9 (1,996.2 ) 1,019.8 Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests $ 1,017.9 $ 3,521.4 $ 985.9 $ (1,996.2 ) $ 3,529.0 Consolidating Balance Sheet As of December 31, 2015 (in millions) The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Assets Investment Securities: Fixed maturity investments, at fair value $ — $ 2,074.6 $ 5.9 $ — $ 2,080.5 Short-term investments, at amortized cost (which approximates fair value) 4.4 64.1 0.7 — 69.2 Common equity securities, at fair value — 298.7 — — 298.7 Other investments — 143.0 — — 143.0 Total investment securities 4.4 2,580.4 6.6 — 2,591.4 Cash — 94.6 0.6 — 95.2 Reinsurance recoverables — 193.5 — — 193.5 Premiums receivable — 219.0 — — 219.0 Deferred acquisition costs — 100.7 — — 100.7 Ceded unearned premiums — 29.5 — — 29.5 Net deferred tax asset — 140.1 — 0.1 140.2 Investment income accrued — 10.1 — — 10.1 Accounts receivable on unsettled investment sales — 30.5 — — 30.5 Investments in subsidiaries 996.9 — 951.3 (1,948.2 ) — Other assets 0.5 190.6 1.4 — 192.5 Total assets $ 1,001.8 $ 3,589.0 $ 959.9 $ (1,948.1 ) $ 3,602.6 Liabilities Unpaid loss and loss adjustment expense reserves $ — $ 1,389.8 $ — $ — $ 1,389.8 Unearned premiums — 560.3 — — 560.3 Funds held under insurance contracts — 137.7 — — 137.7 Debt — — 272.9 — 272.9 Other liabilities 0.9 230.4 6.1 — 237.4 Total liabilities 0.9 2,318.2 279.0 — 2,598.1 OneBeacon's common shareholders' equity and noncontrolling interests Total OneBeacon's common shareholders' equity 1,000.9 1,267.2 680.9 (1,948.1 ) 1,000.9 Total noncontrolling interests — 3.6 — — 3.6 Total OneBeacon's common shareholders' equity and noncontrolling interests 1,000.9 1,270.8 680.9 (1,948.1 ) 1,004.5 Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests $ 1,001.8 $ 3,589.0 $ 959.9 $ (1,948.1 ) $ 3,602.6
Consolidating Statement of Operations and Comprehensive (Loss) Income	Consolidating Statement of Operations and Comprehensive Income Three months ended March 31, 2016 The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Revenues Earned premiums $ — $ 278.6 $ — $ — $ 278.6 Net investment income — 14.4 — — 14.4 Net realized and change in unrealized investment gains — 16.6 — — 16.6 Net other revenues — 0.9 — — 0.9 Total revenues — 310.5 — — 310.5 Expenses Loss and loss adjustment expenses — 158.8 — — 158.8 Policy acquisition expenses — 51.0 — — 51.0 Other underwriting expenses — 55.3 — — 55.3 General and administrative expenses 1.2 2.7 — — 3.9 Interest expense — — 3.3 — 3.3 Total expenses 1.2 267.8 3.3 — 272.3 Pre-tax income (loss) from continuing operations (1.2 ) 42.7 (3.3 ) — 38.2 Income tax benefit — 7.1 1.6 — 8.7 Net income (loss) from continuing operations (1.2 ) 49.8 (1.7 ) — 46.9 Loss from discontinued operations, net of tax — — — — — Income (loss) before equity in earnings of unconsolidated affiliates (1.2 ) 49.8 (1.7 ) — 46.9 Equity in earnings of subsidiaries, net of tax 47.6 — 22.7 (70.3 ) — Net income including noncontrolling interests 46.4 49.8 21.0 (70.3 ) 46.9 Less: Net income attributable to noncontrolling interests — (0.5 ) — — (0.5 ) Net income attributable to OneBeacon's common shareholders 46.4 49.3 21.0 (70.3 ) 46.4 Other comprehensive income, net of tax — — — — — Comprehensive income attributable to OneBeacon's common shareholders $ 46.4 $ 49.3 $ 21.0 $ (70.3 ) $ 46.4 Consolidating Statement of Operations and Comprehensive Income Three months ended March 31, 2015 The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Revenues Earned premiums $ — $ 286.6 $ — $ — $ 286.6 Net investment income — 10.5 — — 10.5 Net realized and change in unrealized investment gains — 14.2 — — 14.2 Net other revenues (expenses) — (3.1 ) — — (3.1 ) Total revenues — 308.2 — — 308.2 Expenses Loss and loss adjustment expenses — 165.9 — — 165.9 Policy acquisition expenses — 51.0 — — 51.0 Other underwriting expenses — 55.9 — — 55.9 General and administrative expenses 1.3 2.7 0.1 — 4.1 Interest expense — — 3.2 — 3.2 Total expenses 1.3 275.5 3.3 — 280.1 Pre-tax income (loss) from continuing operations (1.3 ) 32.7 (3.3 ) — 28.1 Income tax (expense) benefit — (4.8 ) 1.4 — (3.4 ) Net income (loss) from continuing operations (1.3 ) 27.9 (1.9 ) — 24.7 Loss from discontinued operations, net of tax — (0.1 ) — — (0.1 ) Net income (loss) before equity in earnings of unconsolidated affiliates (1.3 ) 27.8 (1.9 ) — 24.6 Equity in earnings of subsidiaries, net of tax 25.4 — 12.6 (38.0 ) — Net income including noncontrolling interests 24.1 27.8 10.7 (38.0 ) 24.6 Less: Net income attributable to noncontrolling interests — (0.5 ) — — (0.5 ) Net income attributable to OneBeacon's common shareholders 24.1 27.3 10.7 (38.0 ) 24.1 Other comprehensive income, net of tax 0.2 — 0.2 (0.2 ) 0.2 Comprehensive income attributable to OneBeacon's common shareholders $ 24.3 $ 27.3 $ 10.9 $ (38.2 ) $ 24.3
Consolidating Statement of Cash Flows	Consolidating Statement of Cash Flows The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Cash flows from operations: Net income including noncontrolling interests $ 46.4 $ 49.8 $ 21.0 $ (70.3 ) $ 46.9 Charges (credits) to reconcile net income to cash flows provided from (used for) operations: Undistributed earnings from subsidiaries (47.6 ) — (22.7 ) 70.3 — Net realized and change in unrealized investment gains — (16.6 ) — — (16.6 ) Deferred income tax expense — 6.7 — — 6.7 Dividends received from subsidiaries 31.0 — — (31.0 ) — Other operating items: Net change in loss and LAE reserves — (46.0 ) — — (46.0 ) Net change in unearned premiums — 8.3 — — 8.3 Net change in ceded unearned premiums — (6.8 ) — — (6.8 ) Net change in premiums receivable — (11.4 ) — — (11.4 ) Net change in reinsurance recoverables on paid and unpaid losses — 26.5 — — 26.5 Net change in funds held under insurance contracts — (2.8 ) — — (2.8 ) Net change in other assets and liabilities 1.3 (31.2 ) 1.6 — (28.3 ) Net cash provided from (used for) operations 31.1 (23.5 ) (0.1 ) (31.0 ) (23.5 ) Cash flows from investing activities: Net maturities, purchases and sales of short-term investments 0.2 (51.3 ) 0.6 — (50.5 ) Maturities of fixed maturity investments — 110.1 — — 110.1 Sales of fixed maturity investments — 161.9 5.9 (5.9 ) 161.9 Sales of common equity securities — 103.2 — — 103.2 Return of capital and distributions of other investments — 3.0 — — 3.0 Purchases of fixed maturity investments — (215.7 ) — 5.9 (209.8 ) Purchases of common equity securities — (75.4 ) — — (75.4 ) Contributions for other investments — (0.3 ) — — (0.3 ) Net change in unsettled investment purchases and sales — 27.6 — — 27.6 Net acquisitions of property and equipment — (0.9 ) — — (0.9 ) Capital contribution from parent — 8.8 2.0 (10.8 ) — Net cash provided from investing activities 0.2 71.0 8.5 (10.8 ) 68.9 Cash flows from financing activities: Cash dividends paid to common shareholders (19.8 ) — — — (19.8 ) Cash dividends paid to parent — (31.0 ) — 31.0 — Capital contribution to subsidiary — (2.0 ) (8.8 ) 10.8 — Repurchases and retirements of common stock (11.5 ) — — — (11.5 ) Payments on capital lease obligation — (0.5 ) — — (0.5 ) Net cash used for financing activities (31.3 ) (33.5 ) (8.8 ) 41.8 (31.8 ) Net increase (decrease) in cash during period — 14.0 (0.4 ) — 13.6 Cash balance at beginning of period — 94.6 0.6 — 95.2 Cash balance at end of period $ — $ 108.6 $ 0.2 $ — $ 108.8 Consolidating Statement of Cash Flows The Company (guarantor) Non-guarantor subsidiaries OBH (issuer) Consolidating adjustments Consolidated Cash flows from operations: Net income including noncontrolling interests $ 24.1 $ 27.8 $ 10.7 $ (38.0 ) $ 24.6 Charges (credits) to reconcile net income to cash flows provided from (used for) operations: Undistributed earnings from subsidiaries (25.4 ) — (12.6 ) 38.0 — Net loss from discontinued operations — 0.1 — — 0.1 Net realized and change in unrealized investment gains — (14.2 ) — — (14.2 ) Net adjustment to gain on sale of business — 3.7 — — 3.7 Deferred income tax expense — 0.5 — — 0.5 Dividends received from subsidiaries 20.0 — — (20.0 ) — Other operating items: Net change in loss and LAE reserves — (38.2 ) — — (38.2 ) Net change in unearned premiums — 2.0 — — 2.0 Net change in ceded unearned premiums — (1.4 ) — — (1.4 ) Net change in premiums receivable — (16.6 ) — — (16.6 ) Net change in reinsurance recoverables on paid and unpaid losses — 14.0 — — 14.0 Net change in funds held under reinsurance contracts — 19.7 — — 19.7 Net change in funds held under insurance contracts — 12.0 — — 12.0 Net change in other assets and liabilities 2.8 12.1 2.3 — 17.2 Net cash provided from operations—continuing operations 21.5 21.5 0.4 (20.0 ) 23.4 Net cash used for operations—discontinued operations — (0.1 ) — — (0.1 ) Net cash provided from operations 21.5 21.4 0.4 (20.0 ) 23.3 Cash flows from investing activities: Net maturities, purchases and sales of short-term investments 0.1 8.1 (0.2 ) — 8.0 Maturities of fixed maturity investments — 32.9 — — 32.9 Sales of fixed maturity investments — 177.6 — — 177.6 Sales of common equity securities — 39.6 — — 39.6 Return of capital and distributions of other investments — 3.7 — — 3.7 Purchases of fixed maturity investments — (273.0 ) — — (273.0 ) Purchases of common equity securities — (26.2 ) — — (26.2 ) Contributions for other investments — (1.9 ) — — (1.9 ) Net change in unsettled investment purchases and sales — 40.3 — — 40.3 Net acquisitions of property and equipment — (0.4 ) — — (0.4 ) Net cash provided from (used for) investing activities 0.1 0.7 (0.2 ) — 0.6 Cash flows from financing activities: Cash dividends paid to common shareholders (20.0 ) — — — (20.0 ) Cash dividends paid to parent — (20.0 ) — 20.0 — Repurchases and retirements of common stock (1.6 ) — — — (1.6 ) Payments on capital lease obligation — (1.4 ) — — (1.4 ) Net cash used for financing activities (21.6 ) (21.4 ) — 20.0 (23.0 ) Net increase in cash during period — 0.7 0.2 — 0.9 Cash balance at beginning of period — 87.0 — — 87.0 Cash balance at end of period $ — $ 87.7 $ 0.2 $ — $ 87.9

Nature of Operations and Summ34

Nature of Operations and Summary of Significant Accounting Policies (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)segment	Dec. 31, 2015USD ($)
Basis of presentation
Unamortized Debt Issuance Expense | $	$ 1.9	$ 1.9
Number of underwriting segments | segment	16
White Mountains Insurance Group Ltd
Basis of presentation
Ownership interest (as a percent)	76.10%

Acquisitions and Dispositions (

Acquisitions and Dispositions (Details) - USD ($) $ in Millions	Jul. 31, 2015	Mar. 31, 2015	Mar. 31, 2016	Dec. 23, 2014
Dispositions
Net Business Exposure			$ 0
Runoff [Member]
Dispositions
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations				$ 101
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Fair Value				$ 64.9
Essentia Insurance Company [Member]
Dispositions
Gain on sale of discontinued operation, pre-tax		$ 3.7
Crop [Member]
Dispositions
Agreement Length	5 years
Disposal Group, Including Discontinued Operation, Consideration	$ 3
Quota Share Reinsurance Agreement Percentage	100.00%

Unpaid Loss and Loss Adjustme36

Unpaid Loss and Loss Adjustment Expense (LAE) Reserves (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross beginning balance	$ 1,389.8	$ 1,342.2
Less beginning reinsurance recoverables on unpaid losses	(186)	(161.6)
Net beginning loss and LAE reserves	1,203.8	1,180.6
Current year losses	158.8	167.7
Prior year losses	0	(1.8)
Total incurred loss and LAE	158.8	165.9
Current year losses	(22)	(22.1)
Prior year losses	(147.2)	(162)
Total loss and LAE payments	(169.2)	(184.1)
Net ending loss and LAE reserves	1,193.4	1,162.4
Plus ending reinsurance recoverables on unpaid losses	(150.4)	(141.6)
Gross ending loss and LAE reserves	$ 1,343.8	$ 1,304

Reinsurance (Details)

Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Reinsurance Retention Policy [Line Items]
Reinsurance recoverables on paid losses	$ 16.6
Reinsurance recoverable on unpaid losses	150.4	$ 186	$ 141.6	$ 161.6
Reinsurance recoverables	$ 167	$ 193.5
Percentage of total paid and unpaid reinsurance recoverables	100.00%
Standard & Poor's, AA Rating [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance recoverables	$ 42.7
Percentage of total paid and unpaid reinsurance recoverables	26.00%
Standard & Poor's, A Rating [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance recoverables	$ 98.2
Percentage of total paid and unpaid reinsurance recoverables	59.00%
Standard & Poor's, BBB rating
Reinsurance Retention Policy [Line Items]
Reinsurance recoverables	$ 26.1
Percentage of total paid and unpaid reinsurance recoverables	15.00%
Runoff [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance Recoverables on Unpaid Losses	$ 19.4
Financial Institutions [Member]
Reinsurance Retention Policy [Line Items]
Quota Share Reinsurance Agreement Percentage	50.00%

Investment Securities (Net inve

Investment Securities (Net investment income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Gross Investment Income	$ 15.6	$ 11.9
Less external investment expenses	(1.2)	(1.4)
Net investment income, pre-tax	14.4	10.5
Surplus notes
Schedule of Trading Securities and Other Trading Assets [Line Items]
Proceeds from Interest Received	2.4
Fixed maturity investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Gross Investment Income	12.1	10.2
Common equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Gross Investment Income	1	1.6
Other investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Gross Investment Income	$ 2.5	$ 0.1

Investment Securities (Net real

Investment Securities (Net realized investment gains (losses)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized investment gains (losses), pre-tax	$ (5.9)	$ 9.5
Fixed maturity investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized investment gains (losses), pre-tax	(1.4)	0.7
Common equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized investment gains (losses), pre-tax	(4.7)	9.8
Other investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized investment gains (losses), pre-tax	$ 0.2	$ (1)

Investment Securities (Changes

Investment Securities (Changes in fair value) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Total net changes in fair value reflected in revenues
Changes in net unrealized investment gains (losses)	$ 22.5	$ 4.8
Changes in net foreign currency translation gains (losses)	0	(0.1)
Total net changes in fair value reflected in revenues	22.5	4.7
Fixed maturity investments
Total net changes in fair value reflected in revenues
Changes in net unrealized investment gains (losses)	15	6.6
Changes in net foreign currency translation gains (losses)	0	0
Total net changes in fair value reflected in revenues	15	6.6
Common equity securities
Total net changes in fair value reflected in revenues
Changes in net unrealized investment gains (losses)	9.7	(4.4)
Changes in net foreign currency translation gains (losses)	0	(0.1)
Total net changes in fair value reflected in revenues	9.7	(4.5)
Other investments
Total net changes in fair value reflected in revenues
Changes in net unrealized investment gains (losses)	(2.2)	2.6
Changes in net foreign currency translation gains (losses)	0	0
Total net changes in fair value reflected in revenues	$ (2.2)	$ 2.6

Investment Securities (Net unre

Investment Securities (Net unrealized investment gains and losses) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Schedule of Investments [Abstract]
Trading Securities Gross Unrealized Gain	$ 63.5	$ 46.5
Trading Securities Gross Unrealized Loss	(27.7)	(33.2)
Gross Unrealized Gains (Losses) on Trading Securities Pretax	35.8	13.3
Trading Securities, Unrealized Gains and Losses, Tax	(12.4)	(6.5)
Unrealized gains (losses) on trading securities, net of tax	$ 23.4	$ 6.8

Investment Securities (Fixed ma

Investment Securities (Fixed maturity investment gains and losses) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities Gross Unrealized Gain	$ 63.5	$ 46.5
Gross unrealized losses	(27.7)	(33.2)
Carrying Value	2,028.7	2,080.5
U.S. Government and agency obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	53.5	85.4
Trading Securities Gross Unrealized Gain	0.1	0
Gross unrealized losses	0	(0.1)
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	53.6	85.3
Debt securities issued by corporations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	733.3	810.8
Trading Securities Gross Unrealized Gain	11.2	4.1
Gross unrealized losses	(0.9)	(4.5)
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	743.6	810.4
Municipal obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	67.6	67.7
Trading Securities Gross Unrealized Gain	1.8	1.5
Gross unrealized losses	(0.1)	(0.2)
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	69.3	69
Mortgage and asset-backed securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	1,077.8	1,035.1
Trading Securities Gross Unrealized Gain	3.7	1.3
Gross unrealized losses	(3.7)	(4.5)
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	1,077.8	1,031.9
Foreign government obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	1	1
Trading Securities Gross Unrealized Gain	0.2	0.2
Gross unrealized losses	0	0
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	1.2	1.2
Preferred stocks
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	78.3	78.3
Trading Securities Gross Unrealized Gain	4.9	4.4
Gross unrealized losses	0	0
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	83.2	82.7
Total fixed maturity investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	2,011.5	2,078.3
Trading Securities Gross Unrealized Gain	21.9	11.5
Gross unrealized losses	(4.7)	(9.3)
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	$ 2,028.7	$ 2,080.5

Investment Securities (Converti

Investment Securities (Convertible fixed maturity investments and other investments) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Funds held under insurance contracts	$ 134.9	$ 137.7
Trading Securities Gross Unrealized Gain	63.5	46.5
Gross unrealized losses	(27.7)	(33.2)
Carrying Value	2,028.7	2,080.5
Common equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	262.5	295
Trading Securities Gross Unrealized Gain	19.4	12.7
Gross unrealized losses	(6)	(9)
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	275.9	298.7
Other investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	132.6	135.6
Trading Securities Gross Unrealized Gain	22.2	22.3
Gross unrealized losses	(17)	(14.9)
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	137.8	143
Total common equity securities and other investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Cost or amortized cost	395.1	430.6
Trading Securities Gross Unrealized Gain	41.6	35
Gross unrealized losses	(23)	(23.9)
Net unrealized foreign currency gains (losses)	0	0
Carrying Value	$ 413.7	$ 441.7

Investment Securities (Fair val

Investment Securities (Fair value measurements) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)fundRate	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)fundRate	Dec. 31, 2014USD ($)fund	Dec. 23, 2014USD ($)
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized investment gains (losses), pre-tax	$ (5.9)	$ 9.5
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	137.8		$ 143
Fair value of investments	$ 2,428.3	2,365.5	$ 2,507.5	$ 2,306.8
Percentage of Fair Value Investments Using Observable Inputs	92.00%		92.00%
Maximum Percentage Differences Between Prices Provided by Pricing Services Considered Outliers	5.00%
Maximum Differences Between Prices Provided By Pricing Services Considered Outliers	$ 1
Percentage of private preferred stock	85.00%		85.00%
Fair Value Assets Measured on Recurring Basis Transfers out	$ 0	2.9
Other investments at fair value	123.7		$ 128.3
Fair Value Assets Measured on Recurring Basis Transfers in	0	2.9
Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	308.7	351.4	363.3	358.7
Fair Value Assets Measured on Recurring Basis Transfers out	0	0
Fair Value Assets Measured on Recurring Basis Transfers in	0	0
Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,925.4	1,732.7	$ 1,945.9	$ 1,692.1
Fair Value Assets Measured on Recurring Basis Transfers out	0	0
Fair Value Assets Measured on Recurring Basis Transfers in	0	2.9
Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair Value Assets Measured on Recurring Basis Transfers out	0
Fair Value Assets Measured on Recurring Basis Transfers in	$ 0	0
Hedge funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Liquidity adjustment | Rate	0.00%		0.00%
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	$ 16.2		$ 16.4
Other investments at fair value	$ 16.2		$ 16.4
Number of Investments | fund	4		4
Private equity funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	$ 41.3		$ 46.1
Other investments at fair value	$ 41.3		46.1
Number of Investments | fund	17			17
Community reinvestment vehicle
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	$ 14.4		14.3
Single Fund
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	12.7		12.9
Tax development fund
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	14.1	$ 16.2	14.7
Debt securities issued by corporations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	743.6		810.4
Debt securities issued by corporations | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Number of Investments		1
Mortgage and asset-backed securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,077.8		1,031.9
Mortgage and asset-backed securities | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,077.8		1,031.9
Mortgage and asset-backed securities | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	128.8		140.4
Commercial Mortgage Backed Securities [Member] | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	128.8		140.4
Commercial Mortgage Backed Securities [Member] | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Fixed maturity investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized investment gains (losses), pre-tax	(1.4)	$ 0.7
Fixed maturity investments | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	70.5	99.8	70	$ 74
Fair Value Assets Measured on Recurring Basis Transfers out	0	2.9
Fair Value Assets Measured on Recurring Basis Transfers in	0	0
Common equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized investment gains (losses), pre-tax	(4.7)	9.8
Hedge funds and private equity funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	57.5		$ 62.5
Other investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized investment gains (losses), pre-tax	$ 0.2	(1)
Investments, Percent of Total	5.00%		5.00%
Other investments | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 66.3	82.6	$ 65.9	79.6
Fair Value Assets Measured on Recurring Basis Transfers out	0	0
Fair Value Assets Measured on Recurring Basis Transfers in	0	0
Surplus notes
Schedule of Trading Securities and Other Trading Assets [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Fair Value	51.8		51.5
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations	51.8		51.5		$ 101
Recurring basis
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	2,548		2,576.7
Recurring basis | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	428.4		432.5
Recurring basis | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,925.4		1,945.9
Recurring basis | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	136.8		135.9
Recurring basis | U.S. Government and agency obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	53.6		85.3
Recurring basis | U.S. Government and agency obligations | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	53.6		85.3
Recurring basis | U.S. Government and agency obligations | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | U.S. Government and agency obligations | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	743.6		810.4
Recurring basis | Debt securities issued by corporations | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	743.6		810.4
Recurring basis | Debt securities issued by corporations | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Consumer
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	211.6		218.3
Recurring basis | Debt securities issued by corporations | Consumer | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Consumer | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	211.6		218.3
Recurring basis | Debt securities issued by corporations | Consumer | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Industrial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	122.5		121.8
Recurring basis | Debt securities issued by corporations | Industrial | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Industrial | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	122.5		121.8
Recurring basis | Debt securities issued by corporations | Industrial | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Health care
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	109.5		136.2
Recurring basis | Debt securities issued by corporations | Health care | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Health care | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	109.5		136.2
Recurring basis | Debt securities issued by corporations | Health care | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Financials
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	108.4		116
Recurring basis | Debt securities issued by corporations | Financials | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Financials | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	108.4		116
Recurring basis | Debt securities issued by corporations | Financials | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Communications
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	40.1		46
Recurring basis | Debt securities issued by corporations | Communications | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Communications | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	40.1		46
Recurring basis | Debt securities issued by corporations | Communications | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Energy
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	59.8		75.2
Recurring basis | Debt securities issued by corporations | Energy | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Energy | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	59.8		75.2
Recurring basis | Debt securities issued by corporations | Energy | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Basic materials
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	20.7		25.8
Recurring basis | Debt securities issued by corporations | Basic materials | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Basic materials | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	20.7		25.8
Recurring basis | Debt securities issued by corporations | Basic materials | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Utilities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	42.1		42.2
Recurring basis | Debt securities issued by corporations | Utilities | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Utilities | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	42.1		42.2
Recurring basis | Debt securities issued by corporations | Utilities | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Technology
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	28.9		28.9
Recurring basis | Debt securities issued by corporations | Technology | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Debt securities issued by corporations | Technology | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	28.9		28.9
Recurring basis | Debt securities issued by corporations | Technology | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Municipal obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	69.3		69
Recurring basis | Municipal obligations | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Municipal obligations | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	69.3		69
Recurring basis | Municipal obligations | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Mortgage and asset-backed securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,077.8		1,031.9
Recurring basis | Mortgage and asset-backed securities | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Mortgage and asset-backed securities | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,077.8		1,031.9
Recurring basis | Mortgage and asset-backed securities | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Foreign government obligations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1.2		1.2
Recurring basis | Foreign government obligations | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0.7		0.6
Recurring basis | Foreign government obligations | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0.5		0.6
Recurring basis | Foreign government obligations | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Preferred stocks
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	83.2		82.7
Recurring basis | Preferred stocks | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Preferred stocks | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	12.7		12.7
Recurring basis | Preferred stocks | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	70.5		70
Recurring basis | Fixed maturity investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	2,028.7		2,080.5
Recurring basis | Fixed maturity investments | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	54.3		85.9
Recurring basis | Fixed maturity investments | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,903.9		1,924.6
Recurring basis | Fixed maturity investments | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	70.5		70
Recurring basis | Short-term investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	119.7		69.2
Recurring basis | Short-term investments | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	119.7		69.2
Recurring basis | Short-term investments | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Short-term investments | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	275.9		298.7
Recurring basis | Common equity securities | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	254.4		277.4
Recurring basis | Common equity securities | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	21.5		21.3
Recurring basis | Common equity securities | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Consumer
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	46.7		38.2
Recurring basis | Common equity securities | Consumer | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	46.7		38.2
Recurring basis | Common equity securities | Consumer | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Consumer | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Industrial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	17		14.5
Recurring basis | Common equity securities | Industrial | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	17		14.5
Recurring basis | Common equity securities | Industrial | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Industrial | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Health care
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	24.4		19.6
Recurring basis | Common equity securities | Health care | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	24.4		19.6
Recurring basis | Common equity securities | Health care | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Health care | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Financials
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	8		4.5
Recurring basis | Common equity securities | Financials | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	8		4.5
Recurring basis | Common equity securities | Financials | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Financials | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Communications
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	20.3		23.9
Recurring basis | Common equity securities | Communications | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	20.3		23.9
Recurring basis | Common equity securities | Communications | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Communications | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Technology
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	29		14.7
Recurring basis | Common equity securities | Technology | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	29		14.7
Recurring basis | Common equity securities | Technology | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Technology | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Common equity securities | Exchange Traded Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	130.5		183.3
Recurring basis | Common equity securities | Exchange Traded Funds [Member] | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	109		162
Recurring basis | Common equity securities | Exchange Traded Funds [Member] | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	21.5		21.3
Recurring basis | Common equity securities | Exchange Traded Funds [Member] | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Other investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	123.7		128.3
Recurring basis | Other investments | Level 1
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Other investments | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0		0
Recurring basis | Other investments | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 66.3		$ 65.9
Runoff [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Fair Value					64.9
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations					$ 101
Preferred stocks
Schedule of Trading Securities and Other Trading Assets [Line Items]
Number of Investments | fund	1		1
NAV Valuation Technique [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 57.4	99	$ 62.4	$ 102.4
Fair Value Assets Measured on Recurring Basis Transfers out	0	0
Fair Value Assets Measured on Recurring Basis Transfers in	$ 0	$ 0

Investment Securities (Corporat

Investment Securities (Corporate debt securites) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	$ 2,428.3	$ 2,507.5	$ 2,365.5	$ 2,306.8
Debt securities issued by corporations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	743.6	810.4
AAA | Debt securities issued by corporations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	2.6	0
AA | Debt securities issued by corporations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	63.7	42.7
A | Debt securities issued by corporations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	252.2	265.4
BBB | Debt securities issued by corporations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	425.1	502.3
Recurring basis
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	2,548	2,576.7
Recurring basis | Debt securities issued by corporations
Schedule of Trading Securities and Other Trading Assets [Line Items]
Debt securities issued by corporations	$ 743.6	$ 810.4

Investment Securities (Fair v46

Investment Securities (Fair value rollforward) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)
Investment securities
Changes in net unrealized investment gains (losses)	$ 22.5	$ 4.8
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	2,507.5	2,306.8
Amortization/accretion	(3.2)	(2.9)
Total net realized and unrealized gains (losses)	16.7	14.3
Purchases	285.5	300.9
Sales	(378.2)	(253.6)
Fair Value Assets Measured on Recurring Basis Transfers in	0	2.9
Transfers out	0	(2.9)
Ending Balance	2,428.3	2,365.5
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	137.8		$ 143
Level 3
Investment securities
Changes in net unrealized investment gains (losses)	0.9	3.3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets Measured on Recurring Basis Transfers in	0	0
Transfers out	0
Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	363.3	358.7
Amortization/accretion	0	0
Total net realized and unrealized gains (losses)	5.6	5.5
Purchases	98.2	62.4
Sales	(158.4)	(75.2)
Fair Value Assets Measured on Recurring Basis Transfers in	0	0
Transfers out	0	0
Ending Balance	308.7	351.4
Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,945.9	1,692.1
Amortization/accretion	(3.2)	(2.9)
Total net realized and unrealized gains (losses)	12.5	7.3
Purchases	187	208.7
Sales	(216.8)	(175.4)
Fair Value Assets Measured on Recurring Basis Transfers in	0	2.9
Transfers out	0	0
Ending Balance	1,925.4	1,732.7
Tax development fund
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	14.1	$ 16.2	$ 14.7
Residential Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	132.7
Ending Balance	131.8
Residential Mortgage Backed Securities [Member] | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0
Ending Balance	0
Residential Mortgage Backed Securities [Member] | Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	132.7
Ending Balance	131.8
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	140.4
Ending Balance	128.8
Commercial Mortgage Backed Securities [Member] | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0
Ending Balance	0
Commercial Mortgage Backed Securities [Member] | Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	140.4
Ending Balance	128.8
Mortgage and asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,031.9
Ending Balance	1,077.8
Mortgage and asset-backed securities | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0
Ending Balance	0
Mortgage and asset-backed securities | Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,031.9
Ending Balance	1,077.8
Debt securities issued by corporations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	810.4
Ending Balance	743.6
Debt securities issued by corporations | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Number of Investments		1
Common equity securities | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0	$ 0
Amortization/accretion	0	0
Total net realized and unrealized gains (losses)	0	0
Purchases	0	0
Sales	0	0
Fair Value Assets Measured on Recurring Basis Transfers in	0	0
Transfers out	0	0
Ending Balance	0	0
Other investments
Investment securities
Changes in net unrealized investment gains (losses)	$ (2.2)	2.6
Investments, Percent of Total	5.00%		5.00%
Other investments | Level 3
Investment securities
Changes in net unrealized investment gains (losses)	$ 0.4	3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	65.9	79.6
Amortization/accretion	0	0
Total net realized and unrealized gains (losses)	0.4	3.1
Purchases	0	0
Sales	0	(0.1)
Fair Value Assets Measured on Recurring Basis Transfers in	0	0
Transfers out	0	0
Ending Balance	66.3	82.6
Fixed maturity investments
Investment securities
Changes in net unrealized investment gains (losses)	15	6.6
Fixed maturity investments | Level 3
Investment securities
Changes in net unrealized investment gains (losses)	0.5	0.3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	70	74
Amortization/accretion	0	0
Total net realized and unrealized gains (losses)	0.5	0.3
Purchases	0	28.4
Sales	0	0
Fair Value Assets Measured on Recurring Basis Transfers in	0	0
Transfers out	0	(2.9)
Ending Balance	70.5	99.8
NAV Valuation Technique [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	62.4	102.4
Amortization/accretion	0	0
Total net realized and unrealized gains (losses)	(2.3)	(1.9)
Purchases	0.3	1.4
Sales	(3)	(2.9)
Fair Value Assets Measured on Recurring Basis Transfers in	0	0
Transfers out	0	0
Ending Balance	$ 57.4	$ 99

Investment Securities (Signific

Investment Securities (Significant unobservable inputs) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)fund	Mar. 31, 2015	Dec. 31, 2015USD ($)fund
Standard Poors N R Rating [Member] | Preferred stocks | Discounted cash flow
Significant unobservable inputs
Assets, Fair Value Disclosure	$ 70.5		$ 70
Discount Rate	8.10%
Standard Poors N R Rating [Member] | Surplus notes | Discounted cash flow
Significant unobservable inputs
Discount Rate	15.80%	16.10%
Preferred stocks
Significant unobservable inputs
Number of Investments | fund	1		1
Seller priority [Member] | Standard Poors N R Rating [Member] | Surplus notes | Discounted cash flow
Significant unobservable inputs
Assets, Fair Value Disclosure	$ 38.2		$ 38
Discount Rate	12.50%	13.00%
Fair Value Inputs, Interest Payment Schedule	5 years	5 years
Fair Value Inputs, Principal Payment Schedule	10 years	10 years
Increase in credit spread	2.50%	2.50%
Pari passu [Member] | Standard Poors N R Rating [Member] | Surplus notes | Discounted cash flow
Significant unobservable inputs
Assets, Fair Value Disclosure	$ 13.6		$ 13.5
Discount Rate	22.50%	22.40%
Fair Value Inputs, Interest Payment Schedule	5 years	5 years
Fair Value Inputs, Principal Payment Schedule	15 years	15 years
Increase in credit spread	2.50%	2.50%

Investment Securities (Change i

Investment Securities (Change in net unrealized gains or losses for Level 3 assets) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unrealized gains (losses) on unsold securities	$ 22.5	$ 4.8
Fixed maturity investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unrealized gains (losses) on unsold securities	15	6.6
Other investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unrealized gains (losses) on unsold securities	(2.2)	2.6
Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unrealized gains (losses) on unsold securities	0.9	3.3
Level 3 | Fixed maturity investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unrealized gains (losses) on unsold securities	0.5	0.3
Level 3 | Other investments
Schedule of Trading Securities and Other Trading Assets [Line Items]
Unrealized gains (losses) on unsold securities	$ 0.4	$ 3

Investment Securities (Asset ba

Investment Securities (Asset backed securities) (Details) $ in Millions	Mar. 31, 2016USD ($)Rate	Dec. 31, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 2,428.3	$ 2,507.5	$ 2,365.5	$ 2,306.8
Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,925.4	1,945.9	$ 1,732.7	$ 1,692.1
Fixed rate CMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	96
Floating rate CMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	32.8
GNMA
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	216	220.5
GNMA | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	216	220.5
GNMA | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
FNMA
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1.4	1.4
FNMA | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1.4	1.4
FNMA | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
FHLMC
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	2.9	3.1
FHLMC | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	2.9	3.1
FHLMC | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Agency commercial mortgage-backed securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	220.3	225
Agency commercial mortgage-backed securities | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	220.3	225
Agency commercial mortgage-backed securities | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Residential
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	131.8	132.7
Residential | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	131.8	132.7
Residential | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	128.8	140.4
Commercial Mortgage Backed Securities [Member] | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	128.8	140.4
Commercial Mortgage Backed Securities [Member] | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Total Non-agency
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	260.6	273.1
Total Non-agency | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	260.6	273.1
Total Non-agency | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Total mortgage-backed securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	480.9	498.1
Total mortgage-backed securities | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	480.9	498.1
Total mortgage-backed securities | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Credit card receivables
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	249.3	202.7
Credit card receivables | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	249.3	202.7
Credit card receivables | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Vehicle receivables
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	265	255.6
Vehicle receivables | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	265	255.6
Vehicle receivables | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Other
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	82.6	75.5
Other | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	82.6	75.5
Other | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Total other asset-backed securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	596.9	533.8
Total other asset-backed securities | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	596.9	533.8
Total other asset-backed securities | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	0
Total mortgage-backed and asset-backed securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,077.8	1,031.9
Total mortgage-backed and asset-backed securities | Level 2
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	1,077.8	1,031.9
Total mortgage-backed and asset-backed securities | Level 3
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0	$ 0
Non-Agency Residential Mortgage Backed Security [Domain]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 36
Maximum | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Percentage of underlying loans reported as non-performing	1.00%
Residential | Residential
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 131.8
Residential, Subprime, Financing Receivable [Member] | Residential
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 7.4
Residential, Subprime, Financing Receivable [Member] | Total mortgage-backed securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Number of securities	1
Subordinate | Fixed rate CMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 41.2
Average basis points of subordination | Rate	30.00%
Subordinate | Floating rate CMBS
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 32.8
Average basis points of subordination | Rate	30.00%
Subordinate | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 74
Subordinate | Residential | Residential
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 0
Number of securities	0
Subordinate | Residential, Subprime, Financing Receivable [Member] | Residential
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 0

Investment Securities (Non-agen

Investment Securities (Non-agency securities) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 2,428.3	$ 2,507.5	$ 2,365.5	$ 2,306.8
Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	131.8	132.7
Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	128.8	140.4
Commercial Mortgage Backed Securities Fixed Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	96
Commercial Mortgage Backed Securities Floating Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	32.8
Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	260.6	$ 273.1
Super Senior | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	8.8
Super Senior | Commercial Mortgage Backed Securities Fixed Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	8.8
Super Senior | Commercial Mortgage Backed Securities Floating Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Senior | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	46
Senior | Commercial Mortgage Backed Securities Fixed Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	46
Senior | Commercial Mortgage Backed Securities Floating Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Subordinate | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	74
Subordinate | Commercial Mortgage Backed Securities Fixed Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	41.2
Subordinate | Commercial Mortgage Backed Securities Floating Rate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	32.8
Securities Issued in 2004 | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	22.8
Securities Issued in 2004 | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Securities Issued in 2004 | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	22.8
Securities Issued in 2005 | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	8.1
Securities Issued in 2005 | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Securities Issued in 2005 | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	8.1
Securities Issued in 2006 | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	3.6
Securities Issued in 2006 | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Securities Issued in 2006 | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	3.6
Securities Issued in 2008 | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	3.4
Securities Issued in 2008 | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Securities Issued in 2008 | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	3.4
Securities issued in 2010 | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	13.1
Securities issued in 2010 | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	5.2
Securities issued in 2010 | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	18.3
Securities issued in 2011 | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	12.6
Securities issued in 2011 | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Securities issued in 2011 | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	12.6
Securities issued in 2012 | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	9.3
Securities issued in 2012 | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	18.3
Securities issued in 2012 | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	27.6
Securities Issued in 2013 | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	13.2
Securities Issued in 2013 | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	15.4
Securities Issued in 2013 | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	28.6
Securities Issued in 2014 [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	45.7
Securities Issued in 2014 [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	44.8
Securities Issued in 2014 [Member] | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	90.5
Securities Issued in 2015 [Member] [Domain] | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Securities Issued in 2015 [Member] [Domain] | Commercial Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	45.1
Securities Issued in 2015 [Member] [Domain] | Total
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	45.1
Residential, Prime, Financing Receivable [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	124.4
Residential, Prime, Financing Receivable [Member] | Super Senior | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	63.1
Residential, Prime, Financing Receivable [Member] | Senior | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	61.3
Residential, Prime, Financing Receivable [Member] | Subordinate | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Residential, Subprime, Financing Receivable [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	7.4
Residential, Subprime, Financing Receivable [Member] | Super Senior | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Residential, Subprime, Financing Receivable [Member] | Senior | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	7.4
Residential, Subprime, Financing Receivable [Member] | Subordinate | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	0
Residential Mortgage Backed Securities [Member] | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	131.8
Residential Mortgage Backed Securities [Member] | Super Senior | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	63.1
Residential Mortgage Backed Securities [Member] | Senior | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	68.7
Residential Mortgage Backed Securities [Member] | Subordinate | Residential Mortgage Backed Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Fair value of investments	$ 0

Investment Securities (Hedge Fu

Investment Securities (Hedge Funds and Private Equity Funds) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	$ 137.8	$ 143
Surplus notes
Schedule of Trading Securities and Other Trading Assets [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Fair Value	51.8	51.5
Community reinvestment vehicle
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	14.4	14.3
Hedge funds other
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	3.5	3.6
Net asset value per share of unfunded commitments	0	0
Long/short equity banks and financial
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	12.7	12.8
Net asset value per share of unfunded commitments	0	0
Hedge funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	16.2	16.4
Other investments at fair value	16.2	16.4
Net asset value per share of unfunded commitments	0	0
Distributions from inactive hedge funds	1
Redemption requests	2.5
Hedge funds | 30 - 59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	13.7
Hedge funds | 60 - 89 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Hedge funds | 90 - 119 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2.5
Hedge funds | Over 120 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Insurance
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2	2
Net asset value per share of unfunded commitments	0.1	0.1
Energy infrastructure and services
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	18	20.7
Net asset value per share of unfunded commitments	3.2	3.4
Healthcare
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	3.8	3.8
Net asset value per share of unfunded commitments	0.4	0.4
Multi-sector
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	13	14.8
Net asset value per share of unfunded commitments	2.1	2.1
Private equity secondaries
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	4	4.4
Net asset value per share of unfunded commitments	2.1	2.1
Real estate
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0.5	0.4
Net asset value per share of unfunded commitments	0.1	0.1
Private equity funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	41.3	46.1
Other investments at fair value	41.3	46.1
Net asset value per share of unfunded commitments	8	8.2
Private equity funds | 1 - 3 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	26.3
Private equity funds | 3 - 5 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	3.8
Private equity funds | 5 - 10 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	11.2
Private equity funds | >10 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Hedge funds and private equity funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	57.5	62.5
Net asset value per share of unfunded commitments	8	$ 8.2
Monthly | Hedge funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Monthly | Hedge funds | 30 - 59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Monthly | Hedge funds | 60 - 89 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Monthly | Hedge funds | 90 - 119 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Monthly | Hedge funds | Over 120 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Quarterly | Hedge funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	13.7
Quarterly | Hedge funds | 30 - 59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	13.7
Quarterly | Hedge funds | 60 - 89 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Quarterly | Hedge funds | 90 - 119 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Quarterly | Hedge funds | Over 120 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Annually | Hedge funds
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2.5
Annually | Hedge funds | 30 - 59 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Annually | Hedge funds | 60 - 89 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	0
Annually | Hedge funds | 90 - 119 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	2.5
Annually | Hedge funds | Over 120 days notice
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other investments at fair value	$ 0

Investment Securities (Surplus

Investment Securities (Surplus Notes) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Dec. 23, 2014
Surplus Note Valuation [Line Items]
Statutory Excess Capital Percentage			250.00%
Surplus notes
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations	$ 51.8	$ 51.5	$ 101
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(49.2)	(49.5)
Surplus notes | Pari passu [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations	13.6	13.5	43.1
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(29.5)	(29.6)
Surplus notes | Seller priority [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations	38.2	38	$ 57.9
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(19.7)	(19.9)
Surplus notes | Current market rates on public debt and contract-based repayments [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(14.7)	(15.1)
Surplus notes | Current market rates on public debt and contract-based repayments [Member] | Pari passu [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(14.2)	(14.7)
Surplus notes | Current market rates on public debt and contract-based repayments [Member] | Seller priority [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(0.5)	(0.4)
Surplus notes | Regulatory approval [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(24.4)	(24.2)
Surplus notes | Regulatory approval [Member] | Pari passu [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(13)	(12.5)
Surplus notes | Regulatory approval [Member] | Seller priority [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(11.4)	(11.7)
Surplus notes | Liquidity adjustment [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(10.1)	(10.2)
Surplus notes | Liquidity adjustment [Member] | Pari passu [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	(2.3)	(2.4)
Surplus notes | Liquidity adjustment [Member] | Seller priority [Member]
Surplus Note Valuation [Line Items]
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Adjustments to Fair Value	$ (7.8)	$ (7.8)

Debt (Details)

Debt (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Nov. 30, 2012	Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Senior unsecured notes, at face value		$ 275	$ 275
Unamortized original issue discount		(0.2)	(0.2)
Unamortized issuance costs(1)		(1.9)	(1.9)
Senior unsecured notes, carrying value		272.9	$ 272.9
Carrying Value | Onebeacon U S Holdings Inc [Member]
Debt Instrument [Line Items]
Senior unsecured notes, carrying value		272.9
Revolving Credit Facility [Member] | Onebeacon U S Holdings Inc [Member]
Debt Instrument [Line Items]
Credit facility balance		0
Total commitment		65
2012 OBH Senior Notes [Member] | Onebeacon U S Holdings Inc [Member]
Debt Instrument [Line Items]
Senior unsecured notes, at face value	$ 275
Issue price as a percentage of par value	99.90%
Proceeds from the issuance of senior notes	$ 272.9
Senior notes annual interest rate	4.60%
Effective yield to maturity	4.70%
Debt Instrument, Acceleration Clause, Repayments of Long-term Debt		$ 75

Segment Information (Details)

Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016USD ($)segmentUnitsRate	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Segment Information
Number of underwriting segments | segment	16
Earned premiums	$ 278.6	$ 286.6
Loss and loss adjustment expense	(158.8)	(165.9)
Policy acquisition expenses	(51)	(51)
Other underwriting expenses	(55.3)	(55.9)
Total underwriting income (loss)	13.5	13.8
Net investment income	14.4	10.5
Net realized and change in unrealized investment gains	16.6	14.2
Net other revenues (expenses)	0.9	(3.1)
General and administrative expenses	(3.9)	(4.1)
Interest expense	(3.3)	(3.2)
Pre-tax income (loss) from continuing operations	38.2	28.1
Total investment securities	2,562.1		$ 2,591.4
Premiums receivable	230.4		219
Reinsurance recoverables	167		193.5
Deferred acquisition costs	102		100.7
Ceded unearned premiums	36.3		29.5
Other assets	431.2		468.5
Total assets	3,529		3,602.6
Unpaid loss and loss adjustment expense reserves	1,343.8	1,304	1,389.8	$ 1,342.2
Unearned premiums	568.6		560.3
Funds held under insurance contracts	134.9		137.7
Debt	272.9		272.9
Other liabilities	189		237.4
Total liabilities	2,509.2		2,598.1
Segment Information, Additional Disclosure
Net written premiums	$ 280.1	$ 287.1
Loss Ratio	57.00%	57.90%
Underwriting Expense Ratio	38.20%	37.30%
Combined Ratio	95.20%	95.20%
Runoff [Member]
Segment Information
Quota Share Reinsurance Agreement Percentage | Rate	100.00%
Investing, Financing and Corporate
Segment Information
Earned premiums	$ 0	$ 0
Loss and loss adjustment expense	0	0
Policy acquisition expenses	0	0
Other underwriting expenses	0	0
Total underwriting income (loss)	0	0
Net investment income	14.4	10.5
Net realized and change in unrealized investment gains	16.6	14.2
Net other revenues (expenses)	0.7	(3.3)
General and administrative expenses	(3.4)	(3.6)
Interest expense	(3.3)	(3.2)
Pre-tax income (loss) from continuing operations	25	14.6
Total investment securities	2,562.1		2,591.4
Premiums receivable	0		0
Deferred acquisition costs	0		0
Ceded unearned premiums	0		0
Other assets	430		467.5
Total assets	3,011.5		3,079.3
Unpaid loss and loss adjustment expense reserves	19.4		20.4
Unearned premiums	0		0
Funds held under insurance contracts	0		0
Debt	272.9		272.9
Other liabilities	189		237.4
Total liabilities	$ 481.3		530.7
Insurance Operations
Segment Information
Number of underwriting segments | Units	2
Specialty Industries [Member] | Insurance Operations
Segment Information
Number of underwriting segments | segment	6
Earned premiums	$ 145.2	150.5
Loss and loss adjustment expense	(67)	(91.8)
Policy acquisition expenses	(27)	(28.1)
Other underwriting expenses	(31.9)	(30.2)
Total underwriting income (loss)	19.3	0.4
Net investment income	0	0
Net realized and change in unrealized investment gains	0	0
Net other revenues (expenses)	0.3	0.2
General and administrative expenses	(0.5)	(0.5)
Interest expense	0	0
Pre-tax income (loss) from continuing operations	19.1	0.1
Total investment securities	0		0
Premiums receivable	143.5		156
Reinsurance recoverables	34		33.6
Deferred acquisition costs	49.1		51.1
Ceded unearned premiums	10.9		10.3
Other assets	0.1		0.1
Total assets	237.6		251.1
Unpaid loss and loss adjustment expense reserves	593.7		597.2
Unearned premiums	262.9		272.2
Funds held under insurance contracts	0		0
Debt	0		0
Other liabilities	0		0
Total liabilities	856.6		869.4
Segment Information, Additional Disclosure
Net written premiums	$ 135.4	$ 153.5
Loss Ratio	46.10%	61.00%
Underwriting Expense Ratio	40.50%	38.70%
Combined Ratio	86.60%	99.70%
Specialty Products [Member] | Insurance Operations
Segment Information
Number of underwriting segments | segment	10
Earned premiums	$ 133.4	$ 136.1
Loss and loss adjustment expense	(91.8)	(74.1)
Policy acquisition expenses	(24)	(22.9)
Other underwriting expenses	(23.4)	(25.7)
Total underwriting income (loss)	(5.8)	13.4
Net investment income	0	0
Net realized and change in unrealized investment gains	0	0
Net other revenues (expenses)	(0.1)	0
General and administrative expenses	0	0
Interest expense	0	0
Pre-tax income (loss) from continuing operations	(5.9)	13.4
Total investment securities	0		0
Premiums receivable	86.9		63
Reinsurance recoverables	113.6		139.5
Deferred acquisition costs	52.9		49.6
Ceded unearned premiums	25.4		19.2
Other assets	1.1		0.9
Total assets	279.9		272.2
Unpaid loss and loss adjustment expense reserves	730.7		772.2
Unearned premiums	305.7		288.1
Funds held under insurance contracts	134.9		137.7
Debt	0		0
Other liabilities	0		0
Total liabilities	1,171.3		$ 1,198
Segment Information, Additional Disclosure
Net written premiums	$ 144.7	$ 133.6
Loss Ratio	68.80%	54.40%
Underwriting Expense Ratio	35.60%	35.80%
Combined Ratio	104.40%	90.20%

Retirement Plans (Periodic Bene

Retirement Plans (Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	$ 55.4
Service cost	0.2	$ 0.2
Interest cost	0.8	1.2
Expected return on plan assets	(1)	(2.2)
Amortization of unrecognized loss	0.3	0.3
Net periodic pension cost (income)	0.3	(0.5)
Defined Benefit Plan, Settlements, Benefit Obligation	0.3	0
Total net periodic benefit cost	0.6	$ (0.5)
Defined Benefit Plan, Expected Contributions in Current Fiscal Year	2.1
Defined Benefit Plan, Contributions by Employer	$ 0.5

Retirement Plans (Other Benefit

Retirement Plans (Other Benefit Plans) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined Contribution Plan, Cost Recognized	$ 0.7	$ 0.7
Supplemental Employee Retirement Plan [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Postemployment Benefits Liability, Noncurrent	3.9		$ 4.1
Postretirement Life Insurance [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Assets Held-in-trust, Noncurrent	34.5		33.9
Postemployment Benefits Liability, Noncurrent	$ 12.4		$ 12.5

Employee Share-Based Incentiv57

Employee Share-Based Incentive Compensation Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Employee Share-Based Incentive Compensation Plans
Expense recognized	$ 2.7	$ 2.1
Restricted Stock [Member]
Employee Share-Based Incentive Compensation Plans
Expense recognized	$ 0.5	$ 0.6
Share-based Compensation Award, Tranche One [Member] | Long Term Incentive Plan | Restricted Stock [Member]
Employee Share-Based Incentive Compensation Plans
Vesting period	2 years
Share-based Compensation Award, Tranche Two [Member] | Long Term Incentive Plan | Restricted Stock [Member]
Employee Share-Based Incentive Compensation Plans
Vesting period	3 years

Employee Share-Based Incentiv58

Employee Share-Based Incentive Compensation Plans (Performance Shares) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Expense amortized
Expense recognized	$ 2.7	$ 2.1
Restricted Stock [Member]
Employee Share-Based Incentive Compensation Plans
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested	2.1	4.3
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 4.3	$ 4	$ 2.5	$ 3.5
Activity in plan
Beginning of period (in shares)	382,722	612,500
New awards (in shares)	170,650	75,950
Forfeitures and net change in assumed forfeitures (in shares)	0	(1,500)
End of period (in shares)	395,872	390,950
Expense amortized
Forfeitures and net change in assumed forfeitures	$ 0	$ 0
Expense recognized	$ 0.5	$ 0.6
Long Term Incentive Plan | Performance shares
Activity in plan
Beginning of period (in shares)	449,435	517,470
Payments and deferrals (in shares)	(167,300)	(181,290)
New awards (in shares)	163,150	154,887
Forfeitures and net change in assumed forfeitures (in shares)	(4,079)	(28,920)
End of period (in shares)	441,206	462,147
Expense amortized
Accrued expense at beginning of period	$ 1.4	$ 3.4
Payments and deferrals	(0.7)	(1.5)
Forfeitures and net change in assumed forfeitures	0	0
Expense recognized	0.4	0.2
Accrued expense at end of period	$ 1.1	$ 2.1
Additional disclosures
Target OB Performance Shares outstanding	441,206
Assumed forfeitures (in shares)	(11,313)
Assumed forfeitures	$ 0
Percentage of shares required to vest	100.00%
Additional compensation cost that would be recognized if all outstanding performance shares vested	$ 3.1
Long Term Incentive Plan | Performance shares | Performance cycle 2011 - 2013
Additional disclosures
Growth target percentage		45.70%
Long Term Incentive Plan | Performance shares | Performance cycle 2013 - 2015
Additional disclosures
Growth target percentage	24.30%
Long Term Incentive Plan | Performance shares | Performance cycle 2015 - 2017
Expense amortized
Accrued expense at end of period	$ 0.1
Additional disclosures
Target OB Performance Shares outstanding	142,710
Long Term Incentive Plan | Performance shares | Range of Performance Cycle from 2015 to 2017 [Member]
Expense amortized
Accrued expense at end of period	$ 0.8
Additional disclosures
Target OB Performance Shares outstanding	146,659
Long Term Incentive Plan | Performance shares | Range of Performance Cycle from 2016 to 2018 [Member]
Expense amortized
Accrued expense at end of period	$ 0.2
Additional disclosures
Target OB Performance Shares outstanding	163,150
Long Term Incentive Plan | Performance shares | Subtotal
Expense amortized
Accrued expense at end of period	$ 1.1
Additional disclosures
Target OB Performance Shares outstanding	452,519

Employee Share-Based Incentiv59

Employee Share-Based Incentive Compensation Plans (Restricted Shares) (Details) - USD ($) $ in Millions	Feb. 24, 2016	Feb. 24, 2015	May. 25, 2011	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Unamortized grant date fair value
Expense recognized				$ (2.7)	$ (2.1)
Restricted Stock [Member]
Employee Share-Based Incentive Compensation Plans
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms				10 months 24 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested				$ 2.1	$ 4.3
Activity in plan
Beginning of period (in shares)				382,722	612,500
New awards (in shares)				170,650	75,950
Forfeitures (in shares)				0	(1,500)
Vested (in shares)				(157,500)	(296,000)
End of period (in shares)				395,872	390,950
Unamortized grant date fair value
Unamortized grant date fair value, beginning of period				$ 2.5	$ 3.5
Issued				2.3	1.1
Share Based Compensation Arrangement by Share Based Payment Award Equity Instruments Other than Options Nonvested Number before Forfeitures				0	0
Expense recognized				(0.5)	(0.6)
Unamortized grant date fair value, end of period				$ 4.3	$ 4
Awards Issued in 2016 [Member] | Restricted Stock [Member]
Activity in plan
New awards (in shares)	170,650
Unamortized grant date fair value
Issued	$ 2.3
Awards Issued in 2016 [Member] | Restricted Stock Units (RSUs) [Member]
Activity in plan
New awards (in shares)				222,449
End of period (in shares)				222,449
Awards Issued in 2015 [Member] | Restricted Stock [Member]
Activity in plan
New awards (in shares)		75,950
Unamortized grant date fair value
Issued		$ 1.1
Awards Issued in 2015 [Member] | Restricted Stock Units (RSUs) [Member]
Activity in plan
New awards (in shares)					207,848
End of period (in shares)				198,928
Unamortized grant date fair value
Expense recognized				$ (0.4)	$ (0.1)
Chief Executive Officer [Member] | Awards Issued in 2011 [Member] | Restricted Stock [Member]
Activity in plan
New awards (in shares)			630,000
Vested (in shares)				(157,500)	(157,500)	(157,500)
End of period (in shares)				157,500
Share-based Compensation Award, Tranche One [Member] | Awards Issued in 2016 [Member] | Restricted Stock [Member]
Activity in plan
End of period (in shares)				92,500
Share-based Compensation Award, Tranche Two [Member] | Awards Issued in 2016 [Member] | Restricted Stock [Member]
Activity in plan
End of period (in shares)				78,150

Employee Share-Based Incentiv60

Employee Share-Based Incentive Compensation Plans Employee Share-Based Incentive Compensation Plans (Other Share-Based Compensation) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Employee Share-Based Incentive Compensation Plans
Employee Stock Ownership Plan (ESOP), Annual Base Contribution Provided to Participants Expressed as Percentage of Salary	6.00%
Annual Compensation Cap	$ 265,000
Percentage Owned of Common Stock	3.00%		3.00%
Expense recognized	$ 2,700,000	$ 2,100,000
Employee Stock Ownership Plan (ESOP), Annual Contribution Provided to Participants Expressed as Percentage of Salary	3.00%
Employee Stock Ownership Plan (ESOP), Social Security Wage Base Amount Maximum	$ 118,500
KSOP [Member]
Employee Share-Based Incentive Compensation Plans
Expense recognized	$ 1,400,000	$ 1,200,000

Employee Share-Based Incentiv61

Employee Share-Based Incentive Compensation Plans Employee Share-Based Incentive Compensation Plans (Restricted Stock Units) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Employee Share-Based Incentive Compensation Plans
Expense recognized	$ 2.7	$ 2.1
Awards Issued in 2016 [Member] | Restricted Stock Units (RSUs) [Member]
Employee Share-Based Incentive Compensation Plans
New awards (in shares)	222,449
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	222,449
Awards Issued in 2015 [Member] | Restricted Stock Units (RSUs) [Member]
Employee Share-Based Incentive Compensation Plans
New awards (in shares)		207,848
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	198,928
Expense recognized	$ 0.4	$ 0.1

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Tax Contingency [Line Items]
Effective tax rate	(22.80%)	12.10%
Federal statutory rate	35.00%	35.00%
Income tax benefit	$ 8.7	$ (3.4)
Foreign Tax Authority
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent	0.70%	1.20%
Tax Assessment Year 2007 to 2009 [Member] | Internal Revenue Service (IRS)
Income Tax Contingency [Line Items]
Income tax benefit	$ 12.8
Tax Years 2010 - 2012 [Member] | Internal Revenue Service (IRS)
Income Tax Contingency [Line Items]
Income Tax Examination, Increase (Decrease) in Liability from Prior Year, Related to Items with Unallowable Deductions	4.7
Increase (Decrease) in Income Taxes Receivable	$ 6

Fair Value of Financial Instr63

Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fair Value of Financial Instruments
Debt	$ 272.9	$ 272.9
Fair Value | Onebeacon U S Holdings Inc [Member]
Fair Value of Financial Instruments
Long-term Debt, Fair Value	278	$ 276.4
Carrying Value | Onebeacon U S Holdings Inc [Member]
Fair Value of Financial Instruments
Debt	$ 272.9

Legal Contingencies (Details)

Legal Contingencies (Details) - Pending Litigation - Tribune Company Litigation	3 Months Ended
	Mar. 31, 2016USD ($)
Loss Contingencies [Line Items]
Proceeds common stock, litigation settlement	$ 32,000,000
Estimated Litigation Liability	$ 0

Earnings (loss) per Share (Deta

Earnings (loss) per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings attributable to OneBeacon's common shareholders—basic and diluted (in millions):
Net income from continuing operations attributable to OneBeacon's common shareholders	$ 46.4	$ 24.2
Allocation of income for participating unvested restricted common shares	(0.2)	(0.1)
Dividends paid on participating restricted common shares	0	(0.1)
Total allocation to restricted common shares	(0.2)	(0.2)
Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts	46.2	24
Undistributed Earnings, Basic [Abstract]
Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts	46.2	24
Dividends paid, net of restricted common share amounts	(19.8)	(19.9)
Total undistributed net earnings, net of restricted common share amounts	$ 26.4	$ 4.1
Weighted Average Number of Shares Outstanding, Basic [Abstract]
Total weighted average common shares outstanding	94.5	95.3
Weighted average unvested restricted common shares	(0.4)	(0.5)
Basic and diluted earnings per share denominator	94.1	94.8
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income from continuing operations attributable to OneBeacon's common shareholders	$ 0.49	$ 0.25
Dividends declared and paid	(0.21)	(0.21)
Undistributed earnings	0.28	0.04
Total OneBeacon common shareholders' equity
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Dividends declared and paid	$ (0.21)	$ (0.21)

Common Shareholders' Equity (De

Common Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Aug. 22, 2007
Equity, Class of Treasury Stock [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures	0	1,500
Dividends, Common Stock, Cash	$ 20.8	$ 21.1
Dividends, per share, cash paid	$ 0.21	$ 0.21
Net change in benefit plan assets and obligations	$ 0	$ 0.3
Income tax expense	0	0.1
Net change in benefit plan assets and obligations, net of tax	0	(0.2)
Class A common
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount			$ 200
Stock Repurchase Program, Remaining Authorized Repurchase Amount	75
Total OneBeacon common shareholders' equity
Equity, Class of Treasury Stock [Line Items]
Dividends, Common Stock, Cash	$ 19.8	$ 20
Dividends, per share, cash paid	$ 0.21	$ 0.21
Net change in benefit plan assets and obligations, net of tax	$ 0	$ (0.2)
Accum. other comprehensive loss
Equity, Class of Treasury Stock [Line Items]
Dividends, Common Stock, Cash	0	0
Net change in benefit plan assets and obligations, net of tax	$ 0	$ (0.2)
Share Repurchase Program [Domain] | Class A common
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Shares	850,349	0
Stock Repurchased During Period, Value	$ 10.6
Treasury Stock Acquired, Average Cost Per Share	$ 12.42	$ 0
Restricted Stock [Member] | Class A common
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Value	$ 0.9	$ 1.6
Shares Paid for Tax Withholding for Share Based Compensation	64,981	112,051

Discontinued Operations (Summar

Discontinued Operations (Summary of the Results of Operations) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 23, 2014
Discontinued Operations
Unpaid loss and loss adjustment expense reserves	$ 1,343.8	$ 1,304	$ 1,389.8	$ 1,342.2
Segment, Discontinued Operations
Discontinued Operations
Loss from discontinued operations, net of tax	$ 0	$ (0.1)
Runoff [Member]
Discontinued Operations
Quota Share Reinsurance Agreement Percentage	100.00%
Surplus notes
Discontinued Operations
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations	$ 51.8		51.5		$ 101
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Fair Value	51.8		51.5
Runoff [Member]
Discontinued Operations
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations					101
Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Fair Value					$ 64.9
Investing, Financing and Corporate
Discontinued Operations
Unpaid loss and loss adjustment expense reserves	$ 19.4		$ 20.4

Consolidating Financial Infor68

Consolidating Financial Information (Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Fixed maturity investments, at fair value (amortized cost: $2,011.5 in 2016 and $2,078.3 in 2015)	$ 2,028.7	$ 2,080.5
Short-term investments, at amortized cost (which approximates fair value)	119.7	69.2
Common equity securities, at fair value (amortized cost - $262.5 in 2016 and $295.0 in 2015)	275.9	298.7
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	137.8	143
Total investment securities	2,562.1	2,591.4
Cash	108.8	95.2	$ 87.9	$ 87
Reinsurance recoverables	167	193.5
Premiums receivable	230.4	219
Deferred acquisition costs	102	100.7
Ceded unearned premiums	36.3	29.5
Net deferred tax asset	134.1	140.2
Investment income accrued	9.4	10.1
Accounts receivable on unsettled investment sales	4.5	30.5
Investments in subsidiaries	0	0
Other assets	174.4	192.5
Total assets	3,529	3,602.6
Liabilities
Unpaid loss and loss adjustment expense reserves	1,343.8	1,389.8	1,304	1,342.2
Unearned premiums	568.6	560.3
Funds held under insurance contracts	134.9	137.7
Debt	272.9	272.9
Accounts payable on unsettled investment purchases	1.5	0
Other liabilities	187.5	237.4
Total liabilities	2,509.2	2,598.1
Equity [Abstract]
Total OneBeacon's common shareholders' equity	1,016.6	1,000.9
Total noncontrolling interests	3.2	3.6
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,019.8	1,004.5	1,052.1	1,049.3
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	3,529	3,602.6
The Company (guarantor)
Investments, Debt and Equity Securities [Abstract]
Fixed maturity investments, at fair value (amortized cost: $2,011.5 in 2016 and $2,078.3 in 2015)	0	0
Short-term investments, at amortized cost (which approximates fair value)	4.2	4.4
Common equity securities, at fair value (amortized cost - $262.5 in 2016 and $295.0 in 2015)	0	0
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	0	0
Total investment securities	4.2	4.4
Cash	0	0	0	0
Reinsurance recoverables	0	0
Premiums receivable	0	0
Deferred acquisition costs	0	0
Ceded unearned premiums	0	0
Net deferred tax asset	0	0
Investment income accrued	0	0
Accounts receivable on unsettled investment sales	0	0
Investments in subsidiaries	1,013.5	996.9
Other assets	0.2	0.5
Total assets	1,017.9	1,001.8
Liabilities
Unpaid loss and loss adjustment expense reserves	0	0
Unearned premiums	0	0
Funds held under insurance contracts	0	0
Debt	0	0
Accounts payable on unsettled investment purchases	0
Other liabilities	1.3	0.9
Total liabilities	1.3	0.9
Equity [Abstract]
Total OneBeacon's common shareholders' equity	1,016.6	1,000.9
Total noncontrolling interests	0	0
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,016.6	1,000.9
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	1,017.9	1,001.8
Non-guarantor subsidiaries
Investments, Debt and Equity Securities [Abstract]
Fixed maturity investments, at fair value (amortized cost: $2,011.5 in 2016 and $2,078.3 in 2015)	2,028.7	2,074.6
Short-term investments, at amortized cost (which approximates fair value)	115.4	64.1
Common equity securities, at fair value (amortized cost - $262.5 in 2016 and $295.0 in 2015)	275.9	298.7
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	137.8	143
Total investment securities	2,557.8	2,580.4
Cash	108.6	94.6	87.7	87
Reinsurance recoverables	167	193.5
Premiums receivable	230.4	219
Deferred acquisition costs	102	100.7
Ceded unearned premiums	36.3	29.5
Net deferred tax asset	134	140.1
Investment income accrued	9.4	10.1
Accounts receivable on unsettled investment sales	4.5	30.5
Investments in subsidiaries	0	0
Other assets	171.4	190.6
Total assets	3,521.4	3,589
Liabilities
Unpaid loss and loss adjustment expense reserves	1,343.8	1,389.8
Unearned premiums	568.6	560.3
Funds held under insurance contracts	134.9	137.7
Debt	0	0
Accounts payable on unsettled investment purchases	1.5
Other liabilities	177.1	230.4
Total liabilities	2,225.9	2,318.2
Equity [Abstract]
Total OneBeacon's common shareholders' equity	1,292.3	1,267.2
Total noncontrolling interests	3.2	3.6
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,295.5	1,270.8
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	3,521.4	3,589
OBH (issuer)
Investments, Debt and Equity Securities [Abstract]
Fixed maturity investments, at fair value (amortized cost: $2,011.5 in 2016 and $2,078.3 in 2015)	0	5.9
Short-term investments, at amortized cost (which approximates fair value)	0.1	0.7
Common equity securities, at fair value (amortized cost - $262.5 in 2016 and $295.0 in 2015)	0	0
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	0	0
Total investment securities	0.1	6.6
Cash	0.2	0.6	0.2	0
Reinsurance recoverables	0	0
Premiums receivable	0	0
Deferred acquisition costs	0	0
Ceded unearned premiums	0	0
Net deferred tax asset	0	0
Investment income accrued	0	0
Accounts receivable on unsettled investment sales	0	0
Investments in subsidiaries	982.8	951.3
Other assets	2.8	1.4
Total assets	985.9	959.9
Liabilities
Unpaid loss and loss adjustment expense reserves	0	0
Unearned premiums	0	0
Funds held under insurance contracts	0	0
Debt	272.9	272.9
Accounts payable on unsettled investment purchases	0
Other liabilities	9.1	6.1
Total liabilities	282	279
Equity [Abstract]
Total OneBeacon's common shareholders' equity	703.9	680.9
Total noncontrolling interests	0	0
Total OneBeacon's common shareholders' equity and noncontrolling interests	703.9	680.9
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	985.9	959.9
Consolidating adjustments
Investments, Debt and Equity Securities [Abstract]
Fixed maturity investments, at fair value (amortized cost: $2,011.5 in 2016 and $2,078.3 in 2015)	0	0
Short-term investments, at amortized cost (which approximates fair value)	0	0
Common equity securities, at fair value (amortized cost - $262.5 in 2016 and $295.0 in 2015)	0	0
Other investments, at fair value (amortized cost - $132.6 in 2016 and $135.6 in 2015)	0	0
Total investment securities	0	0
Cash	0	0	$ 0	$ 0
Reinsurance recoverables	0	0
Premiums receivable	0	0
Deferred acquisition costs	0	0
Ceded unearned premiums	0	0
Net deferred tax asset	0.1	0.1
Investment income accrued	0	0
Accounts receivable on unsettled investment sales	0	0
Investments in subsidiaries	(1,996.3)	(1,948.2)
Other assets	0	0
Total assets	(1,996.2)	(1,948.1)
Liabilities
Unpaid loss and loss adjustment expense reserves	0	0
Unearned premiums	0	0
Funds held under insurance contracts	0	0
Debt	0	0
Accounts payable on unsettled investment purchases	0
Other liabilities	0	0
Total liabilities	0	0
Equity [Abstract]
Total OneBeacon's common shareholders' equity	(1,996.2)	(1,948.1)
Total noncontrolling interests	0	0
Total OneBeacon's common shareholders' equity and noncontrolling interests	(1,996.2)	(1,948.1)
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	(1,996.2)	$ (1,948.1)
Revolving Credit Facility [Member] | Onebeacon U S Holdings Inc [Member]
Liabilities
Credit facility balance	$ 0

Consolidating Financial Infor69

Consolidating Financial Information (Consolidating Statement of Operations and Comprehensive (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues
Earned premiums	$ 278.6	$ 286.6
Net investment income	14.4	10.5
Net realized and change in unrealized investment gains	16.6	14.2
Net other revenues (expenses)	0.9	(3.1)
Total revenues	310.5	308.2
Expenses
Loss and loss adjustment expenses	158.8	165.9
Policy acquisition expenses	51	51
Other underwriting expenses	55.3	55.9
General and administrative expenses	3.9	4.1
Interest expense	3.3	3.2
Total expenses	272.3	280.1
Pre-tax income (loss) from continuing operations	38.2	28.1
Income tax benefit (expense)	8.7	(3.4)
Net income from continuing operations	46.9	24.7
Loss from discontinued operations, net of tax	0	0.1
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	46.9	24.6
Equity in earnings of subsidiaries, net of tax	0	0
Net income including noncontrolling interests	46.9	24.6
Less: Net income attributable to noncontrolling interests	(0.5)	(0.5)
Net income attributable to OneBeacon's common shareholders	46.4	24.1
Net change in benefit plan assets and obligations, net of tax	0	0.2
Comprehensive income attributable to OneBeacon's common shareholders	46.4	24.3
The Company (guarantor)
Revenues
Earned premiums	0	0
Net investment income	0	0
Net realized and change in unrealized investment gains	0	0
Net other revenues (expenses)	0	0
Total revenues	0	0
Expenses
Loss and loss adjustment expenses	0	0
Policy acquisition expenses	0	0
Other underwriting expenses	0	0
General and administrative expenses	1.2	1.3
Interest expense	0	0
Total expenses	1.2	1.3
Pre-tax income (loss) from continuing operations	(1.2)	(1.3)
Income tax benefit (expense)	0	0
Net income from continuing operations	(1.2)	(1.3)
Loss from discontinued operations, net of tax	0	0
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	(1.2)	(1.3)
Equity in earnings of subsidiaries, net of tax	47.6	25.4
Net income including noncontrolling interests	46.4	24.1
Less: Net income attributable to noncontrolling interests	0	0
Net income attributable to OneBeacon's common shareholders	46.4	24.1
Net change in benefit plan assets and obligations, net of tax	0	0.2
Comprehensive income attributable to OneBeacon's common shareholders	46.4	24.3
Non-guarantor subsidiaries
Revenues
Earned premiums	278.6	286.6
Net investment income	14.4	10.5
Net realized and change in unrealized investment gains	16.6	14.2
Net other revenues (expenses)	0.9	(3.1)
Total revenues	310.5	308.2
Expenses
Loss and loss adjustment expenses	158.8	165.9
Policy acquisition expenses	51	51
Other underwriting expenses	55.3	55.9
General and administrative expenses	2.7	2.7
Interest expense	0	0
Total expenses	267.8	275.5
Pre-tax income (loss) from continuing operations	42.7	32.7
Income tax benefit (expense)	7.1	(4.8)
Net income from continuing operations	49.8	27.9
Loss from discontinued operations, net of tax	0	0.1
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	49.8	27.8
Equity in earnings of subsidiaries, net of tax	0	0
Net income including noncontrolling interests	49.8	27.8
Less: Net income attributable to noncontrolling interests	(0.5)	(0.5)
Net income attributable to OneBeacon's common shareholders	49.3	27.3
Net change in benefit plan assets and obligations, net of tax	0	0
Comprehensive income attributable to OneBeacon's common shareholders	49.3	27.3
OBH (issuer)
Revenues
Earned premiums	0	0
Net investment income	0	0
Net realized and change in unrealized investment gains	0	0
Net other revenues (expenses)	0	0
Total revenues	0	0
Expenses
Loss and loss adjustment expenses	0	0
Policy acquisition expenses	0	0
Other underwriting expenses	0	0
General and administrative expenses	0	0.1
Interest expense	3.3	3.2
Total expenses	3.3	3.3
Pre-tax income (loss) from continuing operations	(3.3)	(3.3)
Income tax benefit (expense)	1.6	1.4
Net income from continuing operations	(1.7)	(1.9)
Loss from discontinued operations, net of tax	0	0
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	(1.7)	(1.9)
Equity in earnings of subsidiaries, net of tax	22.7	12.6
Net income including noncontrolling interests	21	10.7
Less: Net income attributable to noncontrolling interests	0	0
Net income attributable to OneBeacon's common shareholders	21	10.7
Net change in benefit plan assets and obligations, net of tax	0	0.2
Comprehensive income attributable to OneBeacon's common shareholders	21	10.9
Consolidating adjustments
Revenues
Earned premiums	0	0
Net investment income	0	0
Net realized and change in unrealized investment gains	0	0
Net other revenues (expenses)	0	0
Total revenues	0	0
Expenses
Loss and loss adjustment expenses	0	0
Policy acquisition expenses	0	0
Other underwriting expenses	0	0
General and administrative expenses	0	0
Interest expense	0	0
Total expenses	0	0
Pre-tax income (loss) from continuing operations	0	0
Income tax benefit (expense)	0	0
Net income from continuing operations	0	0
Loss from discontinued operations, net of tax	0	0
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	0	0
Equity in earnings of subsidiaries, net of tax	(70.3)	(38)
Net income including noncontrolling interests	(70.3)	(38)
Less: Net income attributable to noncontrolling interests	0	0
Net income attributable to OneBeacon's common shareholders	(70.3)	(38)
Net change in benefit plan assets and obligations, net of tax	0	(0.2)
Comprehensive income attributable to OneBeacon's common shareholders	$ (70.3)	$ (38.2)

Consolidating Financial Infor70

Consolidating Financial Information (Consolidating Statement of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]
Net income including noncontrolling interests	$ 46.9	$ 24.6
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:
Undistributed earnings from subsidiaries	0	0
Net loss from discontinued operations	0	0.1
Net realized and change in unrealized investment gains	(16.6)	(14.2)
Net realized gain on sale of business	0	3.7
Deferred income tax expense	6.7	0.5
Dividends received from subsidiaries	0	0
Other operating items:
Net change in loss and LAE reserves	(46)	(38.2)
Net change in unearned premiums	8.3	2
Net change in ceded unearned premium	6.8	1.4
Net change in premiums receivable	(11.4)	(16.6)
Net change in reinsurance recoverable on paid and unpaid losses	26.5	14
Net change in funds held under reinsurance contracts	0	19.7
Net change in funds held under insurance contracts	(2.8)	12
Net change in other assets and liabilities	(28.3)	17.2
Net cash provided from (used for) operations—continuing operations	(23.5)	23.4
Net cash used for operations—discontinued operations	0	(0.1)
Net cash provided from (used for) operations	(23.5)	23.3
Cash flows from investing activities:
Net maturities, purchases and sales of short-term investments	(50.5)	8
Maturities of fixed maturity investments	110.1	32.9
Sales of fixed maturity investments	161.9	177.6
Sales of common equity securities	103.2	39.6
Return of capital and distributions of other investments	3	3.7
Purchases of fixed maturity investments	(209.8)	(273)
Purchases of common equity securities	(75.4)	(26.2)
Contributions for other investments	(0.3)	(1.9)
Net change in unsettled investment purchases and sales	27.6	40.3
Net acquisitions of property and equipment	(0.9)	(0.4)
Capital contribution from parent	0
Net cash used for investing activities	68.9	0.6
Cash flows from financing activities:
Cash dividends paid to common shareholders	(19.8)	(20)
Cash dividends paid to parent	0	0
Capital contribution to subsidiary	0
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	(11.5)	(1.6)
Payments on capital lease obligation	(0.5)	(1.4)
Net cash used for financing activities	(31.8)	(23)
Net increase (decrease) in cash during period	13.6	0.9
Cash balance at beginning of period	95.2	87
Cash balance at end of period	108.8	87.9
The Company (guarantor)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]
Net income including noncontrolling interests	46.4	24.1
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:
Undistributed earnings from subsidiaries	(47.6)	(25.4)
Net loss from discontinued operations	0	0
Net realized and change in unrealized investment gains	0	0
Net realized gain on sale of business		0
Deferred income tax expense	0	0
Dividends received from subsidiaries	31	20
Other operating items:
Net change in loss and LAE reserves	0	0
Net change in unearned premiums	0	0
Net change in ceded unearned premium	0	0
Net change in premiums receivable	0	0
Net change in reinsurance recoverable on paid and unpaid losses	0	0
Net change in funds held under reinsurance contracts		0
Net change in funds held under insurance contracts	0	0
Net change in other assets and liabilities	1.3	2.8
Net cash provided from (used for) operations—continuing operations		21.5
Net cash used for operations—discontinued operations		0
Net cash provided from (used for) operations	31.1	21.5
Cash flows from investing activities:
Net maturities, purchases and sales of short-term investments	0.2	0.1
Maturities of fixed maturity investments	0	0
Sales of fixed maturity investments	0	0
Sales of common equity securities	0	0
Return of capital and distributions of other investments	0	0
Purchases of fixed maturity investments	0	0
Purchases of common equity securities	0	0
Contributions for other investments	0	0
Net change in unsettled investment purchases and sales	0	0
Net acquisitions of property and equipment	0	0
Capital contribution from parent	0
Net cash used for investing activities	0.2	0.1
Cash flows from financing activities:
Cash dividends paid to common shareholders	(19.8)	(20)
Cash dividends paid to parent	0	0
Capital contribution to subsidiary	0
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	(11.5)	(1.6)
Payments on capital lease obligation	0	0
Net cash used for financing activities	(31.3)	(21.6)
Net increase (decrease) in cash during period	0	0
Cash balance at beginning of period	0	0
Cash balance at end of period	0	0
Non-guarantor subsidiaries
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]
Net income including noncontrolling interests	49.8	27.8
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:
Undistributed earnings from subsidiaries	0	0
Net loss from discontinued operations	0	0.1
Net realized and change in unrealized investment gains	(16.6)	(14.2)
Net realized gain on sale of business		3.7
Deferred income tax expense	6.7	0.5
Dividends received from subsidiaries	0	0
Other operating items:
Net change in loss and LAE reserves	(46)	(38.2)
Net change in unearned premiums	8.3	2
Net change in ceded unearned premium	6.8	1.4
Net change in premiums receivable	(11.4)	(16.6)
Net change in reinsurance recoverable on paid and unpaid losses	26.5	14
Net change in funds held under reinsurance contracts		19.7
Net change in funds held under insurance contracts	(2.8)	12
Net change in other assets and liabilities	(31.2)	12.1
Net cash provided from (used for) operations—continuing operations		21.5
Net cash used for operations—discontinued operations		(0.1)
Net cash provided from (used for) operations	(23.5)	21.4
Cash flows from investing activities:
Net maturities, purchases and sales of short-term investments	(51.3)	8.1
Maturities of fixed maturity investments	110.1	32.9
Sales of fixed maturity investments	161.9	177.6
Sales of common equity securities	103.2	39.6
Return of capital and distributions of other investments	3	3.7
Purchases of fixed maturity investments	(215.7)	(273)
Purchases of common equity securities	(75.4)	(26.2)
Contributions for other investments	(0.3)	(1.9)
Net change in unsettled investment purchases and sales	27.6	40.3
Net acquisitions of property and equipment	(0.9)	(0.4)
Capital contribution from parent	8.8
Net cash used for investing activities	71	0.7
Cash flows from financing activities:
Cash dividends paid to common shareholders	0	0
Cash dividends paid to parent	(31)	(20)
Capital contribution to subsidiary	(2)
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	0	0
Payments on capital lease obligation	(0.5)	(1.4)
Net cash used for financing activities	(33.5)	(21.4)
Net increase (decrease) in cash during period	14	0.7
Cash balance at beginning of period	94.6	87
Cash balance at end of period	108.6	87.7
OBH (issuer)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]
Net income including noncontrolling interests	21	10.7
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:
Undistributed earnings from subsidiaries	(22.7)	(12.6)
Net loss from discontinued operations	0	0
Net realized and change in unrealized investment gains	0	0
Net realized gain on sale of business		0
Deferred income tax expense	0	0
Dividends received from subsidiaries	0	0
Other operating items:
Net change in loss and LAE reserves	0	0
Net change in unearned premiums	0	0
Net change in ceded unearned premium	0	0
Net change in premiums receivable	0	0
Net change in reinsurance recoverable on paid and unpaid losses	0	0
Net change in funds held under reinsurance contracts		0
Net change in funds held under insurance contracts	0	0
Net change in other assets and liabilities	1.6	2.3
Net cash provided from (used for) operations—continuing operations		0.4
Net cash used for operations—discontinued operations		0
Net cash provided from (used for) operations	(0.1)	0.4
Cash flows from investing activities:
Net maturities, purchases and sales of short-term investments	0.6	(0.2)
Maturities of fixed maturity investments	0	0
Sales of fixed maturity investments	5.9	0
Sales of common equity securities	0	0
Return of capital and distributions of other investments	0	0
Purchases of fixed maturity investments	0	0
Purchases of common equity securities	0	0
Contributions for other investments	0	0
Net change in unsettled investment purchases and sales	0	0
Net acquisitions of property and equipment	0	0
Capital contribution from parent	2
Net cash used for investing activities	8.5	(0.2)
Cash flows from financing activities:
Cash dividends paid to common shareholders	0	0
Cash dividends paid to parent	0	0
Capital contribution to subsidiary	(8.8)
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	0	0
Payments on capital lease obligation	0	0
Net cash used for financing activities	(8.8)	0
Net increase (decrease) in cash during period	(0.4)	0.2
Cash balance at beginning of period	0.6	0
Cash balance at end of period	0.2	0.2
Consolidating adjustments
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]
Net income including noncontrolling interests	(70.3)	(38)
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:
Undistributed earnings from subsidiaries	70.3	38
Net loss from discontinued operations	0	0
Net realized and change in unrealized investment gains	0	0
Net realized gain on sale of business		0
Deferred income tax expense	0	0
Dividends received from subsidiaries	(31)	(20)
Other operating items:
Net change in loss and LAE reserves	0	0
Net change in unearned premiums	0	0
Net change in ceded unearned premium	0	0
Net change in premiums receivable	0	0
Net change in reinsurance recoverable on paid and unpaid losses	0	0
Net change in funds held under reinsurance contracts		0
Net change in funds held under insurance contracts	0	0
Net change in other assets and liabilities	0	0
Net cash provided from (used for) operations—continuing operations		(20)
Net cash used for operations—discontinued operations		0
Net cash provided from (used for) operations	(31)	(20)
Cash flows from investing activities:
Net maturities, purchases and sales of short-term investments	0	0
Maturities of fixed maturity investments	0	0
Sales of fixed maturity investments	(5.9)	0
Sales of common equity securities	0	0
Return of capital and distributions of other investments	0	0
Purchases of fixed maturity investments	5.9	0
Purchases of common equity securities	0	0
Contributions for other investments	0	0
Net change in unsettled investment purchases and sales	0	0
Net acquisitions of property and equipment	0	0
Capital contribution from parent	(10.8)
Net cash used for investing activities	(10.8)	0
Cash flows from financing activities:
Cash dividends paid to common shareholders	0	0
Cash dividends paid to parent	31	20
Capital contribution to subsidiary	10.8
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	0	0
Payments on capital lease obligation	0	0
Net cash used for financing activities	41.8	20
Net increase (decrease) in cash during period	0	0
Cash balance at beginning of period	0	0
Cash balance at end of period	$ 0	$ 0