OneBeacon Insurance 10-Q 29 Oct 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2014	Oct. 24, 2014	Oct. 24, 2014
		Class A common	Class B common
Entity Registrant Name	'OneBeacon Insurance Group, Ltd.	'	'
Entity Central Index Key	'0001369817	'	'
Document Type	'10-Q	'	'
Document Period End Date	30-Sep-14	'	'
Amendment Flag	'false	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Filer Category	'Accelerated Filer	'	'
Entity Common Stock, Shares Outstanding	'	23,541,649	71,754,738
Document Fiscal Year Focus	'2014	'	'
Document Fiscal Period Focus	'Q3	'	'

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Investment Securities:	'		'
Fixed maturity investments, at fair value	$1,715.70		$1,700.90
Short-term investments, at amortized cost (which approximates fair value)	238.4		157
Common equity securities, at fair value	315.5		336.9
Convertible fixed maturity investments, at fair value	17.3		30.5
Other investments	134.8		139.6
Total investments	2,421.70		2,364.90
Cash	187.5		168.1
Reinsurance recoverables	114.1	[1]	89.9
Premiums receivable	283.7		228.2
Deferred acquisition costs	121.8		103.7
Net deferred tax asset	86.7		90.6
Investment income accrued	9.3		10.1
Accounts receivable on unsettled investment sales	22		3.3
Other assets	307.2		272.7
Assets held for sale	1,699.20		1,880.10
Total assets	5,253.20		5,211.60
Liabilities	'		'
Unpaid loss and loss adjustment expense reserves	1,159.60		1,054.30
Unearned premiums	625.2		544.9
Debt	274.7		274.7
Accounts payable on unsettled investment purchases	23.5		11.6
Other liabilities	352.1		338.6
Liabilities held for sale	1,699.20		1,880.10
Total liabilities	4,134.30		4,104.20
OneBeacon's common shareholders' equity	'		'
Common shares and paid-in surplus (par value $0.01; authorized, 200,000,000 shares; issued and outstanding, 95,296,387 and 95,404,138 shares)	1,023		1,022.50
Retained earnings	85.7		75
Accumulated other comprehensive loss, after tax	6.9		6.8
Total OneBeacon's common shareholders' equity	1,115.60		1,104.30
Total noncontrolling interests, after tax	3.3		3.1
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,118.90		1,107.40
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	$5,253.20		$5,211.60
[1]	Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB+" (Adequate).

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]	'	'
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)	95,296,387	95,404,138
Common shares, outstanding shares (in shares)	95,296,387	95,404,138

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues	'	'	'	'
Earned premiums	$305.40	$278.90	$872.80	$846.20
Net investment income	10.4	10.1	32.1	30.9
Net realized and change in unrealized investment gains	-16	17	24.8	19.9
Net other revenues	1.3	5.5	3.3	30.1
Total revenues	301.1	311.5	933	927.1
Expenses	'	'	'	'
Loss and loss adjustment expenses	185.2	167.8	520.7	473.7
Policy acquisition expenses	54.6	53.6	150.9	160.9
Other underwriting expenses	51.2	46.8	152.3	150.7
General and administrative expenses	2.4	4.1	9.3	11
Interest expense	3.2	3.3	9.7	9.8
Total expenses	296.6	275.6	842.9	806.1
Pre-tax income from continuing operations	4.5	35.9	90.1	121
Income tax (expense) benefit	1.7	2.9	-10.1	-15.9
Net income from continuing operations	6.2	38.8	80	105.1
Income (loss) from discontinued operations, net of tax	-0.3	0.3	-0.9	0.3
Net income (loss), including noncontrolling interests	-1.1	39.1	71.6	105.4
Less: Net income attributable to noncontrolling interests	0	0	-0.9	-0.8
Net income (loss) attributable to OneBeacon's common shareholders	-1.1	39.1	70.7	104.6
Other comprehensive income, net of tax	0	0.2	0.1	0.5
Comprehensive income attributable to OneBeacon's common shareholders	($1.10)	$39.30	$70.80	$105.10
Earnings (loss) per share attributable to OneBeacon's common shareholdersbbasic and diluted	'	'	'	'
Net income from continuing operations, per share	$0.06	$0.41	$0.83	$1.09
Loss from discontinued operations, net of tax, per share	($0.07)	$0	($0.09)	$0
Net income (loss) attributable to OneBeacon's common shareholders per share	($0.01)	$0.41	$0.74	$1.09
Dividends declared and paid per OneBeacon's common share	$0.21	$0.21	$0.63	$0.63

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (USD $)	Total	Common shares and paid-in surplus	Retained earnings	Accum. other comprehensive income (loss)	Total OneBeacon common shareholders' equity	Noncontrolling interests, after tax
Balances at Dec. 31, 2012	$1,017,300,000	$1,019,100,000	$9,200,000	($13,800,000)	$1,014,500,000	$2,800,000
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'
Net income	105,400,000	0	104,600,000	0	104,600,000	800,000
Net change in benefit plan assets and obligations, net of tax	500,000	0	0	500,000	500,000	0
Total comprehensive income	105,900,000	0	104,600,000	500,000	105,100,000	800,000
Amortization of restricted share awards	2,300,000	2,300,000	0	0	2,300,000	0
Issuance of common shares	400,000	300,000	0	0	300,000	100,000
Dividends, Common Stock, Cash	-60,900,000	0	-60,100,000	0	-60,100,000	-800,000
Balances at Sep. 30, 2013	1,065,000,000	1,021,700,000	53,700,000	-13,300,000	1,062,100,000	2,900,000
Balances at Dec. 31, 2013	1,107,400,000	1,022,500,000	75,000,000	6,800,000	1,104,300,000	3,100,000
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'
Net income	71,600,000	0	70,700,000	0	70,700,000	900,000
Net change in benefit plan assets and obligations, net of tax	100,000	0	0	100,000	100,000	0
Total comprehensive income	71,700,000	0	70,700,000	100,000	70,800,000	900,000
Amortization of restricted share awards	2,300,000	2,300,000	0	0	2,300,000	0
Issuance of common shares	200,000	0	0	0	0	200,000
Repurchase and retirement of common shares	-1,800,000	-1,800,000	0	0	-1,800,000	0
Dividends, Common Stock, Cash	-60,900,000	0	-60,000,000	0	-60,000,000	-900,000
Balances at Sep. 30, 2014	$1,118,900,000	$1,023,000,000	$85,700,000	$6,900,000	$1,115,600,000	$3,300,000

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operations:	'	'
Net income (loss) including noncontrolling interests	$71.60	$105.40
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:	'	'
Net (income) loss from discontinued operations	0.9	-0.3
Net loss from sale of discontinued operations	-7.5	0
Net realized and change in unrealized investment gains	-24.8	-19.9
Net realized gain on sale of business	0	-23
Deferred income tax expense	8.6	12.3
Other operating items:	'	'
Net change in loss and LAE reserves	105.3	52.9
Net change in unearned premiums	80.3	-21.1
Net change in premiums receivable	-55.5	-30.3
Net change in reinsurance recoverable on paid and unpaid losses	-24.2	24.5
Net change in other assets and liabilities	-22.8	77.8
Net cash provided from operationsbcontinuing operations	146.9	178.3
Net cash used for operationsbdiscontinued operations	-44.8	-98
Net cash provided from (used for) operations	102.1	80.3
Cash flows from investing activities:	'	'
Net maturities, purchases and sales of short-term investments	-81.5	67.3
Maturities of fixed maturity investments	202.6	196.6
Sales of fixed maturity investments	1,459.60	1,208.60
Sales of common equity securities	97.5	142
Sales of convertible fixed maturity investments	20.6	39.5
Distributions and redemptions of other investments	11.1	13.1
Purchases of fixed maturity investments	-1,641.20	-1,381.80
Purchases of common equity securities	-63	-168.5
Purchases of convertible fixed maturity investments	-11.3	-12
Contributions for other investments	-3.6	-7.1
Proceeds from sale of business	0	31.3
Net change in unsettled investment purchases and sales	-6.8	-7.7
Net acquisitions of property and equipment	-0.9	-7.6
Net cash (used for) provided from investing activitiesbcontinuing operations	-16.9	113.7
Net cash provided from investing activitiesbdiscontinued operations	0	0
Net cash provided from investing activities	-16.9	113.7
Cash flows from financing activities:	'	'
Cash dividends paid to common shareholders	-60	-60.1
Payments for repurchase of common stock	-1.8	0
Payments on capital lease obligation	4	4
Net cash used for financing activitiesbcontinuing operations	-65.8	-64.1
Net cash used for financing activitiesbdiscontinued operations	0	0
Net cash used for financing activities	-65.8	-64.1
Net increase (decrease) in cash during period	19.4	129.9
Cash balance at beginning of period	168.1	43.9
Cash balance at end of period	$187.50	$173.80

Nature_of_Operations_and_Summa

Nature of Operations and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2014
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. The OneBeacon U.S.-based operating companies are property and casualty insurance writers, most of which historically have operated in a multi-company pool or have participated in 100% quota share reinsurance agreements. OneBeacon formed an indirect wholly-owned subsidiary in 2013, Split Rock Insurance, Ltd. ("Split Rock"), a Bermuda-based reinsurance company, which reinsures certain risks of affiliated entities. 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 was acquired by White Mountains Insurance Group, Ltd. ("White Mountains") from Aviva plc ("Aviva") in 2001 (the "OneBeacon Acquisition"). White Mountains is a holding company whose businesses provide property and casualty insurance, reinsurance and certain other products. As of September 30, 2014, White Mountains owned 75.3% of the Company's common shares. Within this report, the term "OneBeacon" is used to refer to one or more entities within the consolidated organization, as the context requires. 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 601 Carlson Parkway, Minnetonka, Minnesota 55305 and its registered office is located at Clarendon House, 2 Church Street, Hamilton HM 11, Bermuda.
	In October 2012, one of OneBeacon's indirect wholly-owned subsidiaries, OneBeacon Insurance Group LLC ("OneBeacon LLC"), entered into a definitive agreement (as amended, the "Stock Purchase Agreement") with Trebuchet US Holdings, Inc. ("Trebuchet"), a wholly-owned subsidiary of Armour Group Holdings Limited (together with Trebuchet, “Armour”), to sell its run-off business. See Note 2—"Acquisitions and Dispositions" and Note 15—"Discontinued Operations." OneBeacon's run-off business includes the results of OneBeacon's remaining non-specialty commercial lines business and certain other run-off business, including the vast majority of asbestos and environmental reserves, as well as certain purchase accounting adjustments related to the run-off business and the OneBeacon Acquisition (the “Runoff Business,” the sale of which is referred to as the “Runoff Transaction”). The assets and liabilities associated with the Runoff Business as of September 30, 2014 and December 31, 2013, have been presented in the balance sheet as held for sale assuming the investing and financing steps required to effect the sale were completed as of the current balance sheet date. The Runoff Business has been presented as discontinued operations in the consolidated statements of operations and cash flows. The Runoff Business disposal group excludes investing and financing activities from amounts classified as discontinued operations. OneBeacon's investing and financing operations are conducted on an overall consolidated level and, accordingly, there are no separately identifiable investing or financing cash flows associated with the Runoff Business. Pursuant to the terms of the Stock Purchase Agreement, the legal entities included in the sale and expected to be transferred to Armour will hold an agreed upon level of invested assets and capital at closing.
	In anticipation of the Runoff Transaction, and as a means to separate the Runoff Business from the ongoing specialty business, OneBeacon sought and received various regulatory approvals to terminate, enter into or amend various intercompany reinsurance agreements which took effect on October 1, 2012.
	OneBeacon's reportable segments are Specialty Products, Specialty Industries, and Investing, Financing and Corporate. The Specialty Products segment is comprised of eight underwriting operating segments, including a new Crop underwriting operating segment, as well as the Collector Cars and Boats underwriting operating segment that was exited in 2013, representing an aggregation based on those that offer distinct products and tailored coverages and services to a broad customer base across the United States. During 2013, the Company received approval to provide Multiple Peril Crop Insurance ("MPCI") through the federal crop insurance program administered by the U.S. Department of Agriculture's Risk Management Agency ("RMA"). The Company has entered into an exclusive agreement with a managing general agency, Climate Crop Insurance Agency LLC ("The Climate Corporation"), to provide coverages through the federal program and other supplemental coverages, including crop-hail. MPCI net written premiums are estimated based on processed applications, which are typically received around the sales closing date, with necessary adjustments made as the Company receives acreage reports from the policyholders. Premiums written on this business are recognized as revenues and are earned ratably over the period of risk commencing with the sales closing date, which approximates the inception of the planting season, and ending with the estimated crop harvest date. The Company began writing crop business in the fourth quarter of 2013.
	The Specialty Industries segment is comprised of six underwriting operating segments, including the Energy underwriting operating segment that was exited in 2013, 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, consisting of a normal recurring nature, 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 2013 Annual Report on Form 10-K. The preparation of financial statements in conformity with GAAP 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 2013 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
	Unrecognized Tax Benefits
	Effective January 1, 2014, OneBeacon prospectively adopted ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists (ASC 740). The new ASU requires balance sheet presentation of an unrecognized tax benefit as a reduction of a deferred tax asset for a net operating loss ("NOL") carryforward or tax credit carryforward rather than as a liability. The exception is in circumstances where a carryforward is not available to settle the additional taxes that might arise upon disallowance of the tax position under the tax law of the applicable jurisdiction. Prior to the issuance of ASU 2013-11, the guidance for unrecognized tax benefits under ASC 740 did not provide explicit guidance on whether an entity should present an unrecognized tax benefit as a liability or as a reduction of NOL carryforwards or other tax credits. In circumstances where an NOL carryforward is not available to offset settlement of any additional taxes arising from a disallowed tax position, the unrecognized tax benefit should be presented as a liability. This adoption did not have any impact on the Company's financial statements.
	Recently Issued Accounting Pronouncements
	Qualified Affordable Housing Projects
	In January 2014 the FASB issued ASU 2014-01, Accounting for Investments in Qualified Affordable Housing Projects ("QAHP"), which permits companies to make an accounting policy election to account for investments in a QAHP using the proportional amortization method, if certain conditions are met. Under this method, the initial cost of the investment is amortized in proportion to the tax credits and other tax benefits received, with the net investment performance recognized in the income statement as a component of income tax expense. The new guidance also requires certain new disclosures for all QAHP investments. ASU 2014-01 is effective for annual and interim reporting periods beginning after December 15, 2014 and may be applied retrospectively to all periods presented upon adoption. The Company currently holds an investment in a QAHP that is accounted for under the equity method and does not expect the adoption to have a material impact on its financial position, results of operations, or cash flows.
	Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity
	In April 2014, the FASB issued ASU 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, to reduce diversity in practice for reporting discontinued operations. Under the previous guidance, any component of an entity that was a reportable segment, an operating segment, a reporting unit, a subsidiary, or an asset group was eligible for discontinued operations presentation. The revised guidance only allows disposals of components of an entity that represent a strategic shift (e.g., disposal of a major geographical area, a major line of business, a major equity method investment, or other major parts of an entity) and that have a major effect on a reporting entity’s operations and financial results to be reported as discontinued operations. The revised guidance also requires expanded disclosure in the financial statements for discontinued operations as well as for disposals of significant components of an entity that do not qualify for discontinued operations presentation. The updated guidance is effective for transactions entered into after December 15, 2014.
	Revenue from Contracts with Customers
	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. 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. ASU 2014-09 is effective for annual and interim reporting periods beginning after December 15, 2016.
	Share-Based Compensation Awards
	In June 2014, the FASB issued 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. The new guidance is intended to eliminate diversity in practice for employee share-based awards containing performance targets that could be achieved after the requisite service period. Some reporting entities account for performance targets that can be achieved after the requisite service period as performance conditions that affect the vesting of the award while other reporting entities treat those performance targets as nonvesting conditions that affect the grant-date fair value of the award. The updated 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 should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the periods for which service has been rendered. 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. The new guidance is effective for annual and interim reporting periods beginning after December 15, 2015.

Acqusitions_and_Dispositions

Acqusitions and Dispositions	9 Months Ended
	Sep. 30, 2014
Business Combinations [Abstract]	'
Acquisitions and Dispositions	'
	Acquisitions and Dispositions
	Runoff Business
	As described in Note 1, in October 2012, OneBeacon entered into the Stock Purchase Agreement with respect to the sale of its Runoff Business to Armour. Pursuant to the terms of the Stock Purchase Agreement, at closing, OneBeacon will transfer to Armour all of the issued and outstanding shares of common stock of certain legal entities that will contain the assets, liabilities (including gross and ceded loss reserves) and capital supporting the business as well as certain elements of the Runoff Business infrastructure, including staff and office space. As disclosed in the Form 8-K filed by the Company on June 23, 2014, the Company amended the Stock Purchase Agreement during the second quarter of 2014, primarily to increase the cap on seller financing by $6.7 million to $80.9 million, as well as to extend the termination date to December 31, 2014. Consistent with the proposed closing balance sheet, pro forma as of June 30, 2014, the Company expects to provide seller financing at closing in the form of surplus notes with an estimated par value of $80.9 million. The loss on sale of the Runoff Business is currently estimated at $80.5 million.
	The Runoff Transaction is subject to various closing conditions, primarily the receipt of regulatory approvals. The Pennsylvania Insurance Department is currently conducting its regulatory review of the Runoff Transaction, which included a public hearing on July 23, 2014. Subsequent to the public hearing, the Pennsylvania Insurance Department re-opened the public comment period, which expired on October 17, 2014. The regulatory review process has included a third party actuarial review of the Runoff Business loss and LAE reserves, completed in September 2013, and, subsequently, an independent stochastic modeling of the future cash flows of the Runoff Business, which was completed in June 2014. The Company expects the Runoff Transaction to close in the fourth quarter of 2014.
	At closing, Armour and/or OneBeacon Insurance Company ("OBIC") and certain legal entities within the ongoing OneBeacon structure will enter into various ancillary agreements, including the amendment of existing reinsurance agreements and administrative services agreements, to support the separation of the Runoff Business and subsequent transfer to Armour. Also as part of the Runoff Transaction, at closing, OneBeacon and Armour will enter into a Transition Services Agreement (“TSA”), pursuant to which OneBeacon will provide certain transition services to Armour during the term of the TSA, which has an initial term of one year. OneBeacon has concluded that continuing involvement after the closing of the transaction is insignificant relative to the business being sold.
	As described in Note 1, the Runoff Business is presented as held for sale as of September 30, 2014 and December 31, 2013, and as discontinued operations for the three and nine months ended September 30, 2014 and 2013. See Note 15—"Discontinued Operations" for further information regarding balances classified as held for sale and activity reported as discontinued operations.
	Essentia Insurance Company
	Effective January 1, 2013, OneBeacon completed the sale of Essentia Insurance Company ("Essentia"), an indirect wholly-owned subsidiary which wrote the collector cars and boats business, to Markel Corporation. Concurrently, OneBeacon and Hagerty Insurance Agency ("Hagerty") terminated their underwriting arrangement with respect to the collector cars and boats business. OneBeacon recognized a pre-tax gain on sale of $23.0 million ($15.0 million after tax) in the first quarter of 2013. The Company had negligible earned premiums for the three and nine months ended September 30, 2014 and earned premiums of $15.8 million and $85.2 million for the three and nine months ended September 30, 2013, respectively, related to the Collector Cars and Boats underwriting operating segment.

Unpaid_Loss_and_Loss_Adjustmen

Unpaid Loss and Loss Adjustment Expense (LAE) Reserves	9 Months Ended
	Sep. 30, 2014
Insurance Loss Reserves [Abstract]	'
Unpaid Loss and Loss Adjustment Expense (LAE) Reserves	'
	Unpaid Loss and Loss Adjustment Expense (LAE) Reserves
	Loss and LAE reserve summary - Ongoing Business
	The following table summarizes the loss and LAE reserve activities of OneBeacon's insurance subsidiaries for the three and nine months ended September 30, 2014 and 2013:
		Three months ended						Nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
		($ in millions)
	Gross beginning balance	$	1,125.40		$	1,027.80		$	1,054.30		$	1,000.00
	Less beginning reinsurance recoverables on unpaid losses	(92.0		)	(81.8		)	(80.2		)	(107.3		)
	Net beginning loss and LAE reserves	1,033.40			946			974.1			892.7
	Loss and LAE incurred relating to:
	Current year losses	177.9			164			506.4			473.8
	Prior year losses	7.3			3.8			14.3			(0.1		)
	Total incurred loss and LAE from continuing operations	185.2			167.8			520.7			473.7
	Loss and LAE paid relating to:
	Current year losses	(55.7		)	(54.0		)	(115.3		)	(115.0		)
	Prior year losses	(104.7		)	(87.1		)	(321.3		)	(278.7		)
	Total loss and LAE payments from continuing operations	(160.4		)	(141.1		)	(436.6		)	(393.7		)
	Net ending loss and LAE reserves	1,058.20			972.7			1,058.20			972.7
	Plus ending reinsurance recoverables on unpaid losses	101.4			80.2			101.4			80.2
	Gross ending loss and LAE reserves	$	1,159.60		$	1,052.90		$	1,159.60		$	1,052.90
	Loss and LAE development - Ongoing Business
	Loss and LAE development—2014
	During the three months and nine months ended September 30, 2014, OneBeacon experienced $7.3 million and $14.3 million, respectively, of net unfavorable loss and LAE reserve development on prior accident year reserves. Net unfavorable loss and LAE reserve development during the three months ended September 30, 2014 was primarily attributable to the professional liability, management liability, and financial services businesses included in the Professional Insurance underwriting operating segment, the Accident underwriting operating segment, and the inland marine business in the International Marine Underwriters ("IMU") underwriting operating segment. This unfavorable development during the three months ended September 30, 2014 was partially offset by favorable development in the healthcare business in the Professional Insurance underwriting operating segment and in the Technology underwriting operating segment. Net unfavorable loss and LAE reserve development during the nine months ended September 30, 2014 was primarily attributable to the professional liability and management liability businesses included in the Professional Insurance underwriting operating segment, the Accident underwriting operating segment, and the inland marine business in the IMU underwriting operating segment. This unfavorable development during the nine months ended September 30, 2014 was partially offset by favorable development in the healthcare business included in the Professional Insurance underwriting operating segment, the Specialty Property underwriting operating segment, and the ocean marine business in the IMU underwriting operating segment.
	Loss and LAE development—2013
	During the three and nine months ended September 30, 2013, OneBeacon recorded $3.8 million of unfavorable and $0.1 million of favorable, respectively, loss and LAE reserve development on prior accident year reserves. Unfavorable development during the three months ended September 30, 2013 was primarily related to the Specialty Property and Entertainment underwriting operating segments, which was partially offset by favorable development in its ocean marine business, included in the IMU underwriting operating segment, and in the healthcare business included in the Professional Insurance underwriting operating segment. Unfavorable development for the nine months ended September 30, 2013, primarily related to the Specialty Property underwriting operating segment, was more than offset by favorable development in other underwriting operating segments, primarily IMU and Professional Insurance.
	See Note 15—"Discontinued Operations" for a discussion of impacts to reserves for unpaid losses and LAE related to discontinued operations.

Reinsurance

Reinsurance	9 Months Ended
	Sep. 30, 2014
Reinsurance Disclosures [Abstract]	'
Reinsurance	'
	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. See Note 15—"Discontinued Operations" for amounts related to the Runoff Business.
	Reinsurance Treaties
	The Company's catastrophe reinsurance coverage is discussed in Note 4—"Reinsurance" in the Company's 2013 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 2013 Annual Report on Form 10-K.
	Effective May 1, 2014, OneBeacon renewed its property catastrophe reinsurance program through April 30, 2015. The program provides coverage for OneBeacon's property business as well as certain acts of terrorism. Under the program, the first $20.0 million of losses resulting from any single catastrophe are retained and 100% of the next $110.0 million of losses resulting from the catastrophe are reinsured. Any part of a catastrophe loss in excess of $130.0 million would be retained in full. In the event of a catastrophe, OneBeacon's property catastrophe reinsurance program is reinstated for the remainder of the original contract term by paying a reinstatement premium that is based on the percentage of coverage reinstated and the original property catastrophe coverage premium.
	Also effective May 1, 2014, OneBeacon lowered its retention on its property-per-risk reinsurance program from $10.0 million to $5.0 million.
	Effective January 1, 2014, OneBeacon entered into reinsurance treaties to provide coverage for the 2014 crop year. OneBeacon purchased an aggregate stop loss on its MPCI portfolio, providing 48.5% of coverage in excess of a 101.5% loss ratio on premiums covered by the contract and a separate aggregate stop loss providing 80% of coverage in excess of a 100% loss ratio on its crop-hail portfolio.
	In addition to the corporate catastrophe reinsurance protection, the Company also purchased dedicated reinsurance protection for certain specific lines of business.
	Reinsurance Recoverables
	At September 30, 2014, OneBeacon had reinsurance recoverables on paid losses of $12.7 million and reinsurance recoverables on unpaid losses of $101.4 million. Reinsurance contracts do not relieve OneBeacon of its obligations. Therefore, collectibility of balances due from reinsurers is critical to OneBeacon's financial strength. The following table summarizes Standard & Poor's Financial Services, LLC ("Standard & Poor's") ratings for OneBeacon's reinsurers for its continuing insurance operations, excluding industry pools and associations, based upon reinsurance recoverables amounts on paid and unpaid losses and LAE:
		Balance at		% of total
		30-Sep-14
	Standard & Poor's Rating(1):	($ in millions)
	AA	$	46.5	41	%
	A	64.1		56	%
	BBB+, Not Rated and Other	3.5		3	%
	Total reinsurance recoverables	$	114.1	100	%
	_______________________________________________________________________________
	(1) Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB+" (Adequate).

Investment_Securities

Investment Securities	9 Months Ended
	Sep. 30, 2014
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 2013 Annual Report on Form 10-K for a complete discussion.
	OneBeacon classifies its portfolio of fixed maturity investments and common equity securities, including convertible fixed maturity investments, 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 in total revenues as net realized and unrealized investment gains in revenues on a pre-tax basis.
	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 hedge funds and private equity funds. OneBeacon measures its investments in hedge funds and private equity funds at fair value with changes therein 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 and a tax advantaged federal affordable housing development fund which is accounted for under the equity method.
	OneBeacon's net investment income is comprised primarily of interest income associated with fixed maturity investments, dividend income from its equity investments, and interest income from its short-term investments. Other investments primarily include hedge funds and private equity funds. Net investment income for the three and nine months ended September 30, 2014, and 2013 consisted of the following:
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
			($ in millions)
	Fixed maturity investments		$	10.5		$	10.4		$	31.4		$	30.7
	Common equity securities		1.5			1.5			5.2			4.4
	Convertible fixed maturity investments		0.5			0.2			0.6			0.9
	Other investments		(0.3		)	(0.4		)	—			—
	Gross investment income		12.2			11.7			37.2			36
	Less investment expenses		(1.8		)	(1.6		)	(5.1		)	(5.1		)
	Net investment income		$	10.4		$	10.1		$	32.1		$	30.9
	The composition of net realized investment gains consisted of the following:
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
			($ in millions)
	Fixed maturity investments		$	2.2		$	(5.0	)	$	4.6		$	2.8
	Short-term investments		—			—			—			0.1
	Common equity securities		13.5			2.7			25.4			20.6
	Convertible fixed maturity investments		1			—			3.3			(0.4		)
	Other investments		2.6			(1.9		)	2.6			2.8
	Net realized investment gains		$	19.3		$	(4.2	)	$	35.9		$	25.9
	Accounts payable on unsettled investment purchases as of September 30, 2014 and December 31, 2013 were $23.5 million and $11.6 million, respectively, and accounts receivable on unsettled investment sales were $22.0 million and $3.3 million, respectively.
	The net changes in fair value for the three and nine months ended September 30, 2014, and 2013 are as follows:
			Three months ended September 30, 2014									Nine months ended September 30, 2014
			Changes in net			Changes in net			Total net changes			Changes in net			Changes in net			Total net changes
			unrealized investment			foreign currency			in fair value reflected			unrealized investment			foreign currency			in fair value reflected
			gains (losses)(1)			translation			in revenues(1)			gains(1)			translation			in revenues(1)
						gains (losses)(1)									gains (losses)(1)
			($ in millions)
	Fixed maturity investments		$	(8.0	)	$	—		$	(8.0	)	$	4		$	—		$	4
	Short-term investments		—			(0.1		)	(0.1		)	—			(0.1		)	(0.1		)
	Common equity securities		(21.5		)	(0.4		)	(21.9		)	(11.8		)	(0.4		)	(12.2		)
	Convertible fixed maturity investments		(1.8		)	—			(1.8		)	(4.1		)	—			(4.1		)
	Other investments		(3.5		)	—			(3.5		)	1.3			—			1.3
	Net change in fair value		$	(34.8	)	$	(0.5	)	$	(35.3	)	$	(10.6	)	$	(0.5	)	$	(11.1	)
			Three months ended September 30, 2013									Nine months ended September 30, 2013
			Changes in net			Changes in net			Total net changes			Changes in net			Changes in net			Total net changes
			unrealized investment			foreign currency			in fair value reflected			unrealized investment			foreign currency			in fair value reflected
			gains (losses)(1)			translation			in revenues(1)			gains (1)			translation			in revenues(1)
						gains (losses)(1)									gains (losses)(1)
			($ in millions)
	Fixed maturity investments		$	0.5		$	0.1		$	0.6		$	(33.7	)	$	—		$	(33.7	)
	Short-term investments		—			—			—			—			—			—
	Common equity securities		15.8			0.1			15.9			21.3			0.1			21.4
	Convertible fixed maturity investments		1			—			1			(0.6		)	—			(0.6		)
	Other investments		3.7			—			3.7			6.9			—			6.9
	Net change in fair value		$	21		$	0.2		$	21.2		$	(6.1	)	$	0.1		$	(6.0	)
	_______________________________________________________________________________
	-1	Includes pre-tax changes in net deferred gains and losses on sales of investments between OneBeacon and entities under White Mountains' common control of $(0.7) million and $(0.8) million for the three and nine months ended September 30, 2013, respectively, with no such changes in net deferred gains and losses for the three and nine months ended September 30, 2014.
	The components of OneBeacon's ending net unrealized investment gains and losses, excluding the impact of net unrealized foreign currency translation gains and losses, on its investment portfolio as of September 30, 2014 and December 31, 2013 were as follows:
			September 30,			December 31,
			2014			2013
			($ in millions)
	Investment securities:
	Gross unrealized investment gains		$	125		$	133.7
	Gross unrealized investment losses		(11.2		)	(9.3		)
Total net unrealized investment gains, pre-tax		113.8			124.4
Income taxes		(31.3		)	(33.8		)
Total net unrealized investment gains, after tax		$	82.5		$	90.6
The cost or amortized cost, gross unrealized pre-tax investment gains and losses, net unrealized foreign currency translation gains (losses) and carrying values of fixed maturity investments as of September 30, 2014 and December 31, 2013 were as follows:
		September 30, 2014(1)
		Cost or			Gross			Gross			Net unrealized foreign			Carrying
		amortized			unrealized			unrealized			currency			value
		cost			gains			losses			translation gains (losses)
		($ in millions)
U.S. Government and agency obligations		$	73.3		$	—		$	—		$	—		$	73.3
Debt securities issued by corporations		799.9			13.7			(1.0		)	—			812.6
Municipal obligations		65.1			1.2			(0.2		)	—			66.1
Mortgage-backed and asset-backed securities		882.2			1.4			(2.0		)	—			881.6
Foreign government obligations		1			0.3			—			—			1.3
Preferred stocks		78.3			6.4			—			—			84.7
Total fixed maturity investments		$	1,899.80		$	23		$	(3.2	)	$	—		$	1,919.60
		December 31, 2013(1)
		Cost or			Gross			Gross			Net unrealized foreign			Carrying
		amortized			unrealized			unrealized			currency			value
		cost			gains			losses			translation gains (losses)
		($ in millions)
U.S. Government and agency obligations		$	131		$	0.2		$	(0.1	)	$	—		$	131.1
Debt securities issued by corporations		741.7			14.1			(1.3		)	—			754.5
Municipal obligations		16.9			—			(0.4		)	—			16.5
Mortgage-backed and asset-backed securities		951.5			1.2			(3.2		)	—			949.5
Foreign government obligations		2			0.3			—			—			2.3
Preferred stocks		78.3			5			—			—			83.3
Total fixed maturity investments		$	1,921.40		$	20.8		$	(5.0	)	$	—		$	1,937.20
_______________________________________________________________________________
-1	Includes carrying value of $203.9 million and $236.3 million of fixed maturity investments reclassified to assets held for sale in the consolidated balance sheets as part of the Runoff Transaction as of September 30, 2014 and December 31, 2013, respectively.
The cost or amortized cost, gross unrealized pre-tax investment gains and losses, net unrealized foreign currency translation gains (losses) and carrying values of common equity securities, convertible fixed maturity investments and other investments as of September 30, 2014 and December 31, 2013 were as follows:
		30-Sep-14
		Cost or			Gross			Gross			Net unrealized foreign			Carrying
		amortized			unrealized			unrealized			currency			value
		cost			gains			losses			translation gains (losses)
		($ in millions)
Common equity securities		$	258.1		$	61.3		$	(3.7	)	$	(0.2	)	$	315.5
Convertible fixed maturity investments		17.2			0.6			(0.5		)	—			17.3
Other investments		98.5			40.1			(3.8		)	—			134.8
Total common equity securities, convertible fixed maturity investments and other investments		$	373.8		$	102		$	(8.0	)	$	(0.2	)	$	467.6
		31-Dec-13
		Cost or			Gross			Gross			Net unrealized foreign			Carrying
		amortized			unrealized			unrealized			currency			value
		cost			gains			losses			translation gains (losses)
		($ in millions)
Common equity securities		$	267.2		$	70.4		$	(0.9	)	$	0.2		$	336.9
Convertible fixed maturity investments		26.3			4.5			(0.3		)	—			30.5
Other investments		104.7			38			(3.1		)	—			139.6
Total common equity securities, convertible fixed maturity investments and other investments		$	398.2		$	112.9		$	(4.3	)	$	0.2		$	507
As of September 30, 2014 and December 31, 2013, the Company held unrestricted collateral from its customers, which is included in cash and invested assets, relating to its surety business of $76.1 million and $63.3 million, respectively. The obligation to return these funds is included in other liabilities in the consolidated balance sheets.
Fair value measurements
As of both September 30, 2014 and December 31, 2013, approximately 92% of the investment portfolio recorded at fair value was priced based upon observable inputs.
The fair values of OneBeacon's investments in hedge funds and private equity funds have been classified as Level 3 under the fair value hierarchy since the fund managers do not provide sufficient information to independently evaluate the pricing inputs and methods for each underlying investment, and therefore the inputs are considered to be unobservable. At September 30, 2014 and December 31, 2013, 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 September 30, 2014 and December 31, 2013, other investments reported at fair value represented approximately 4% and 5%, respectively, of the investment portfolio recorded at fair value. Other investments accounted for at fair value as of September 30, 2014 and December 31, 2013 were comprised of $47.6 million and $49.4 million, respectively, in hedge funds, $54.4 million and $56.1 million, respectively, in private equity funds, and $14.2 million and $14.4 million, respectively, in an investment in a community reinvestment vehicle. Additionally, other investments accounted for at fair value as of September 30, 2014 included $0.2 million in trust certificates issued upon dissolution of a private equity fund, with no such investments held as of December 31, 2013. As of both September 30, 2014 and December 31, 2013, OneBeacon held investments in 8 hedge funds and 17 and 19 private equity funds, respectively. The largest investment in a single fund was $15.6 million and $14.9 million at September 30, 2014 and December 31, 2013, respectively. As of September 30, 2014 and December 31, 2013, other investments also included $18.4 million and $19.7 million, respectively, of an investment in a tax advantaged federal affordable housing development fund which is accounted for using the equity method.
The following tables summarize the Company's fair value measurements for investments at September 30, 2014 and December 31, 2013 by level:
		Fair value at			Level 1			Level 2			Level 3
		September 30, 2014(2)
		($ in millions)
Fixed maturity investments:
U.S. Government and agency obligations		$	73.3		$	73.3		$	—		$	—
Debt securities issued by corporations:
Consumer		279			—			279			—
Financial		141			—			141			—
Industrial		104.4			—			104.4			—
Communications		87.2			—			87.2			—
Basic materials		68			—			64.9			3.1
Energy		67.1			—			67.1			—
Utilities		36.9			—			36.9			—
Technology		29			—			29			—
Debt securities issued by corporations		812.6			—			809.5			3.1
Mortgage-backed and asset-backed securities		881.6			—			870.7			10.9
Preferred stocks		84.7			—			13.2			71.5
Municipal obligations		66.1			—			66.1			—
Foreign government obligations		1.3			0.6			0.7			—
Fixed maturity investments		1,919.60			73.9			1,760.20			85.5
Short-term investments		238.4			238.1			0.3			—
Common equity securities:
Consumer		114.4			114.4			—			—
Financials		71.2			70.8			—			0.4
Energy		27.1			27.1			—			—
Basic Materials		19.1			19.1			—			—
Utilities		10.3			10.3			—			—
Other		73.4			73.4			—			—
Common equity securities		315.5			315.1			—			0.4
Convertible fixed maturity investments		17.3			—			17.3			—
Other investments(1)		116.4			—			—			116.4
Total(1)		$	2,607.20		$	627.1		$	1,777.80		$	202.3
_______________________________________________________________________________
-1	Excludes the carrying value of $18.4 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of September 30, 2014.
-2	Fair value includes $203.9 million of fixed maturity investments reclassified to assets held for sale in the September 30, 2014 consolidated balance sheets as part of the Runoff Transaction.
		Fair value at			Level 1			Level 2			Level 3
		December 31, 2013(2)
		($ in millions)
Fixed maturity investments:
U.S. Government and agency obligations		$	131.1		$	131.1		$	—		$	—
Debt securities issued by corporations:
Consumer		239.6			—			239.6			—
Financial		145.5			—			145.5			—
Industrial		106			—			106			—
Communications		91.5			—			91.5			—
Basic materials		64.4			—			64.4			—
Energy		40.5			—			40.5			—
Utilities		38			—			38			—
Technology		29			—			29			—
Debt securities issued by corporations		754.5			—			754.5			—
Mortgage-backed and asset-backed securities		949.5			—			938.6			10.9
Preferred stocks		83.3			—			12.3			71
Municipal obligations		16.5			—			16.5			—
Foreign government obligations		2.3			1.6			0.7			—
Fixed maturity investments		1,937.20			132.7			1,722.60			81.9
Short-term investments		157			155.9			1.1			—
Common equity securities:
Consumer		122.6			122.6			—			—
Financials		83.3			83.2			—			0.1
Energy		34.7			34.7			—			—
Basic Materials		20.3			20.3			—			—
Utilities		8.3			8.3			—			—
Other		67.7			67.7			—			—
Common equity securities		336.9			336.8			—			0.1
Convertible fixed maturity investments		30.5			—			30.5			—
Other investments(1)		119.9			—			—			119.9
Total(1)		$	2,581.50		$	625.4		$	1,754.20		$	201.9
_______________________________________________________________________________
-1	Excludes the carrying value of $19.7 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of December 31, 2013.
-2	Fair value includes $236.3 million of fixed maturity investments reclassified to assets held for sale in the December 31, 2013 consolidated balance sheets as part of the Runoff Transaction.
At September 30, 2014 and December 31, 2013, OneBeacon held one private preferred stock that represented approximately 84% and 85%, respectively, of its preferred stock portfolio. OneBeacon calculated its fair value using projected discounted cash flows based on a discount yield. The discounted yield was determined with inputs from quoted market yields for similar securities and adjusted for liquidity based on management’s best estimate of market conditions; this security is classified as a Level 3 measurement.
The following table summarizes the ratings of OneBeacon's corporate debt securities as of September 30, 2014 and December 31, 2013:
		September 30,			December 31,
		2014			2013
		($ in millions)
AA		$	55.2		$	51.2
A		327.1			357.9
BBB		426.2			345.4
BB		—			—
Not rated		4.1			—
Debt securities issued by corporations(1)		$	812.6		$	754.5
_______________________________________________________________________________
(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”).
Rollforwards of Fair Value Measurements by Level
The changes in Level 1 fair value measurements for the three and nine months ended September 30, 2014 are as follows:
		Fixed			Common			Convertible			Other			Total(1)
		maturity			equity			fixed			investments
		investments			securities			maturity
								investments
		($ in millions)
Balance at January 1, 2014		$	132.7		$	336.8		$	—		$	—		$	469.5
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		0.1			8.5			—			—			8.6
Purchases		114.6			26			—			—			140.6
Sales		(35.7		)	(24.3		)	—			—			(60.0		)
Transfers in		—			—			—			—			—
Transfers out		—			—			—			—			—
Balance at March 31, 2014		211.7			347			—			—			558.7
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		1.3			12.8			—			—			14.1
Purchases		256.6			22.6			—			—			279.2
Sales		(309.4		)	(23.3		)	—			—			(332.7		)
Transfers in		—			—			—			—			—
Transfers out		—			—			—			—			—
Balance at June 30, 2014		160.2			359.1			—			—			519.3
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		—			(8.5		)	—			—			(8.5		)
Purchases		113.7			14.4			—			—			128.1
Sales		(200.0		)	(49.9		)	—			—			(249.9		)
Transfers in		—			—			—			—			—
Transfers out		—			—			—			—			—
Balance at September 30, 2014		$	73.9		$	315.1		$	—		$	—		$	389
_______________________________________________________________________________
-1	Excludes short-term investments which are deemed to have a Level 1 designation.
The changes in Level 2 fair value measurements for the three and nine months ended September 30, 2014 are as follows:
		Fixed			Common			Convertible			Other			Total(1)
		maturity			equity			fixed			investments
		investments			securities			maturity
								investments
		($ in millions)
Balance at January 1, 2014		$	1,722.60		$	—		$	30.5		$	—		$	1,753.10
Amortization/accretion		(2.6		)	—			(0.1		)	—			(2.7		)
Net realized and unrealized gains (losses)		5			—			1.9			—			6.9
Purchases		344			—			3.8			—			347.8
Sales		(404.6		)	—			(6.8		)	—			(411.4		)
Transfers in		—			—			—			—			—
Transfer out		—			—			—			—			—
Balance at March 31, 2014		1,664.40			—			29.3			—			1,693.70
Amortization/accretion		(2.7		)	—			(0.1		)	—			(2.8		)
Net realized and unrealized gains (losses)		7.2			—			(1.7		)	—			5.5
Purchases		345.1			—			4.7			—			349.8
Sales		(285.8		)	—			(6.3		)	—			(292.1		)
Transfers in		7.5			—			—			—			7.5
Transfer out		—			—			—			—			—
Balance at June 30, 2014		1,735.70			—			25.9			—			1,761.60
Amortization/accretion		(2.8		)	—			(0.1		)	—			(2.9		)
Net realized and unrealized gains (losses)		(6.8		)	—			(0.9		)	—			(7.7		)
Purchases		423.5			—			2.8			—			426.3
Sales		(423.7		)	—			(10.4		)	—			(434.1		)
Transfers in		34.3			—			—			—			34.3
Transfer out		—			—			—			—			—
Balance at September 30, 2014		$	1,760.20		$	—		$	17.3		$	—		$	1,777.50
_______________________________________________________________________________
(1)	Excludes short-term investments which are deemed to have a Level 2 designation.
The changes in Level 3 fair value measurements for the three and nine months ended September 30, 2014 and 2013 are as follows:
		Fixed			Common			Convertible			Other			Total(1)
		maturity			equity			fixed			investments(1)
		investments			securities			maturity
								investments
		($ in millions)
Balance at January 1, 2014		$	81.9		$	0.1		$	—		$	119.9		$	201.9
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		0.3			—			—			3.1			3.4
Purchases		7.5			—			—			2.3			9.8
Sales		—			—			—			(1.6		)	(1.6		)
Transfers in		—			—			—			—			—
Transfers out		—			—			—			—			—
Balance at March 31, 2014		$	89.7		$	0.1		$	—		$	123.7		$	213.5
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		0.3			0.4			—			1.7			2.4
Purchases		34.2			—			—			1			35.2
Sales		—			—			—			(1.5		)	(1.5		)
Transfers in		—			—			—			—			—
Transfers out		(7.5		)	—			—			—			(7.5		)
Balance at June 30, 2014		116.7			0.5			—			124.9			242.1
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		1.1			(0.1		)	—			(0.9		)	0.1
Purchases		2			—			—			0.3			2.3
Sales		—			—			—			(7.9		)	(7.9		)
Transfers in		—			—			—			—			—
Transfers out		(34.3		)	—			—			—			(34.3		)
Balance at September 30, 2014		$	85.5		$	0.4		$	—		$	116.4		$	202.3
_______________________________________________________________________________
(1)	Excludes the carrying value of $18.4 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of September 30, 2014.
		Fixed			Common			Convertible			Other			Total(1)
		maturity			equity			fixed			investments(1)
		investments			securities			maturity
								investments
		($ in millions)
Balance at January 1, 2013		$	76.1		$	0.1		$	—		$	122.7		$	198.9
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		0.1			—			—			3.7			3.8
Purchases		1.8			—			—			1.8			3.6
Sales		—			—			—			(4.5		)	(4.5		)
Transfers in		—			—			—			—			—
Transfers out		—			—			—			—			—
Balance at March 31, 2013		78			0.1			—			123.7			201.8
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		(0.2		)	—			—			4.2			4
Purchases		14			—			—			3.4			17.4
Sales		—			—			—			(6.7		)	(6.7		)
Transfers in		—			—			—			—			—
Transfers out		(1.8		)	—			—			—			(1.8		)
Balance at June 30, 2013		90			0.1			—			124.6			214.7
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		(1.8		)	—			—			1.9			0.1
Purchases		—			—			—			1.3			1.3
Sales		(0.5		)	—			—			(1.8		)	(2.3		)
Transfers in		61.3			—			—			—			61.3
Transfers out		(13.8		)	—			—			—			(13.8		)
Balance at September 30, 2013		$	135.2		$	0.1		$	—		$	126		$	261.3
_______________________________________________________________________________
-1	Excludes the carrying value of $20.2 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of September 30, 2013.
“Transfers in” to Level 3 fixed maturity investments of $61.3 million for the nine months ended September 30, 2013 were comprised of one agency commercial mortgage-backed security for which the estimated fair value was determined using industry standard pricing models that take into account unobservable inputs such as prepayment rate, default rate and swap spread. There were no such transfers for the nine months ended September 30, 2014.
“Transfers out” of Level 3 fixed maturity investments of $41.8 million and $15.6 million for the nine months ended September 30, 2014 and 2013, respectively, were comprised of one commercial mortgage-backed security and one residential mortgage-backed security which were recategorized as Level 2 measurements when quoted market prices that were considered reliable and could be validated against alternative sources became available and one commercial mortgage-backed security which was recategorized as a Level 2 measurement when a quoted market price that was considered reliable and could be validated against an alternative source became available, respectively.
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 investment securities classified within Level 3, other than hedge funds and private equity funds, at September 30, 2014. The fair value of investments in hedge funds and private equity funds, which are classified within Level 3, are estimated using the net asset value of the funds.
Description(1)		Fair Value			Rating(2)		Valuation Technique	Unobservable Inputs		Range
Preferred stock		$	71.5		NR		Discounted cash flow	Discount yield		6.60%
Other asset-backed securities		$	10.9		AA+		Broker pricing	Broker quote		N/A
Debt securities issued by corporations		$	3.1		NR		Exchange transaction(3)	N/A		N/A
_________________________________________________________________________
(1)	As of September 30, 2014, each asset type consists of one security.
(2)	Credit ratings are assigned based on the following hierarchy: 1) Standard & Poor's and 2) Moody's
(3)	Derived from the exchange of a convertible fixed maturity investment, where the valuation of the debt security issued by a corporation represents a portion of the total exchange price after taking into consideration the cash and value of the common equity security that was also received in the exchange transaction.
The assumed prepayment rate is a significant unobservable input used to estimate the fair value of investments in agency commercial mortgage-backed securities. Generally for securities priced at a premium, increases in prepayment speeds will result in a lower fair value, while decreases in prepayment speed may result in a higher fair value, with the inverse for securities priced at a discount.
The following table summarizes the change in net unrealized gains or losses for assets designated as Level 3 for the three and nine months ended September 30, 2014 and 2013:
		Three months ended						Nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
		($ in millions)
Fixed maturity investments		$	1.1		$	(1.8	)	$	1.7		$	(1.8	)
Short-term investments		—			—			—			—
Common equity securities		—			—			—			—
Convertible fixed maturity investments		—			—			—			—
Other investments		(3.5		)	3.7			1.3			6.9
Total		$	(2.4	)	$	1.9		$	3		$	5.1
Mortgage-backed Securities
OneBeacon purchases commercial mortgage-backed securities ("CMBS") and residential mortgage-backed securities ("RMBS") to maximize its risk adjusted returns in the context of a diversified portfolio. OneBeacon's non-agency CMBS are generally short tenor and structurally senior, with more than 20 points of subordination on average for fixed rate and floating rate non-agency CMBS as of September 30, 2014. In general, subordination represents the percentage of principal loss on the underlying collateral that would have to occur before the security incurs a loss. These collateral losses, instead, are first absorbed by other securities lower in the capital structure. OneBeacon believes this structural protection mitigates the risk of loss tied to refinancing challenges facing the commercial real estate market. As of September 30, 2014, on average less than 1% of the underlying loans were reported as non-performing for both agency and non-agency CMBS held by OneBeacon. OneBeacon is not an originator of residential mortgage loans. OneBeacon did not hold any RMBS categorized as sub-prime as of September 30, 2014. OneBeacon's investments in hedge funds and private equity funds contain negligible amounts of sub-prime mortgage-backed securities as of September 30, 2014. OneBeacon considers sub-prime mortgage-backed securities to be those that have underlying loan pools that exhibit weak credit characteristics or are issued from dedicated sub-prime shelves or dedicated second-lien shelf registrations (i.e., OneBeacon considers investments backed primarily by second-liens to be sub-prime risks regardless of credit scores or other metrics).
There are also mortgage-backed securities that OneBeacon categorizes as "non-prime" (also called "Alt A" or "A-") that are backed by collateral that has overall credit quality between prime and sub-prime, as determined based on OneBeacon's review of the characteristics of their underlying mortgage loan pools, such as credit scores and financial ratios. As of September 30, 2014, OneBeacon held one mortgage-backed security with a market value of $4.1 million that was classified as non-prime. OneBeacon's non-agency residential mortgage-backed portfolio is generally of moderate average life, fixed rate and structurally senior. OneBeacon does not own any collateralized debt obligations, including residential mortgage-backed collateralized debt obligations.
The following table summarizes the carrying value of OneBeacon's mortgage-backed and asset-backed securities as of September 30, 2014 and December 31, 2013:
		September 30, 2014									December 31, 2013
		Fair Value			Level 2			Level 3			Fair Value			Level 2			Level 3
		($ in millions)
Mortgage-backed securities:
Agency:
GNMA		$	267.7		$	267.7		$	—		$	321.8		$	321.8		$	—
FNMA		20.6			20.6			—			36.5			36.5			—
FHLMC		1.1			1.1			—			24.3			24.3			—
Total agency(1)		289.4			289.4			—			382.6			382.6			—
Non-agency:
Residential		94.7			94.7			—			51.5			51.5			—
Commercial		109.2			109.2			—			155			155			—
Total Non-agency		203.9			203.9			—			206.5			206.5			—
Total mortgage-backed securities		493.3			493.3			—			589.1			589.1			—
Other asset-backed securities:
Credit card receivables		182.4			171.5			10.9			124.2			113.3			10.9
Vehicle receivables		162.1			162.1			—			189.3			189.3			—
Other		43.8			43.8			—			46.9			46.9			—
Total other asset-backed securities		388.3			377.4			10.9			360.4			349.5			10.9
Total mortgage-backed and asset-backed securities		$	881.6		$	870.7		$	10.9		$	949.5		$	938.6		$	10.9
_______________________________________________________________________________
-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).
Non-agency Mortgage-backed Securities
The security issuance years of OneBeacon's investments in non-agency RMBS and non-agency CMBS securities as of September 30, 2014 are as follows:
		Fair Value			Security Issuance Year
					2004			2005			2006			2007			2008			2009		2010		2011		2012		2013		2014
		($ in millions)
Total non-agency RMBS		$	94.7		$	5.4		$	4.4		$	5.3		$	—		$	5.7		$	—	$	4.1	$	15.5	$	4	$	17.2	$	33.1
Total non-agency CMBS		109.2			—			—			—			0.7			—			—		6.7		—		6.3		38.9		56.6
Total non-agency		$	203.9		$	5.4		$	4.4		$	5.3		$	0.7		$	5.7		$	—	$	10.8	$	15.5	$	10.3	$	56.1	$	89.7
Non-agency Residential Mortgage-backed Securities
The classification of the underlying collateral quality and the tranche levels of OneBeacon's non-agency RMBS securities are as follows as of September 30, 2014:
		Fair Value			Super Senior(1)			Senior(2)			Subordinate(3)
		($ in millions)
Prime		$	90.6		$	38.7		$	51.9		$	—
Non-prime		4.1			—			4.1			—
Total non-agency RMBS		$	94.7		$	38.7		$	56		$	—
_______________________________________________________________________________
-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 securities.
Non-agency Commercial Mortgage-backed Securities
The amount of fixed and floating rate securities and their tranche levels of OneBeacon's non-agency CMBS securities are as follows as of September 30, 2014:
		Fair Value			Super Senior(1)			Senior(2)			Subordinate(3)
		($ in millions)
Fixed rate CMBS		$	62.3		$	24.5		$	20.3		$	17.5
Floating rate CMBS		46.9			0.7			—			46.2
Total non-agency CMBS		$	109.2		$	25.2		$	20.3		$	63.7
_______________________________________________________________________________
-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 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 securities.
Other Investments
OneBeacon holds investments in hedge funds and private equity funds which are included in other investments. The fair value of these investments has been estimated using the net asset value of the funds. The following table summarizes investments in hedge funds and private equity funds at September 30, 2014 and December 31, 2013:
		30-Sep-14						31-Dec-13
		Fair			Unfunded			Fair			Unfunded
		Value			Commitments			Value			Commitments
		($ in millions)
Hedge funds
Long/short equity		$	36.6		$	—		$	39.1		$	—
Long/short credit and distressed		8.5			—			8.1			—
Long/short equity activist		2.4			—			2.1			—
Long bank loan		0.1			—			0.1			—
Total hedge funds		47.6			—			49.4			—
Private equity funds
Energy infrastructure and services		26.3			4.8			26			5.9
Multi-sector		15.1			2.2			14.5			2.5
Private equity secondaries		6.3			2.1			6.4			2.1
Healthcare		2.9			1.4			2.8			1.4
Insurance		2.2			0.1			2.3			0.1
Real estate		1.6			0.1			3.9			0.1
Distressed residential real estate		—			—			0.2			—
Total private equity funds		54.4			10.7			56.1			12.1
Total hedge funds and private equity funds(1)		$	102		$	10.7		$	105.5		$	12.1
_______________________________________________________________________________
-1	Excluded from the above table as of September 30, 2014 and December 31, 2013 are other investments, which include an investment in a community reinvestment vehicle of $14.2 million and $14.4 million, respectively, and an investment in a tax advantaged federal affordable housing development fund of $18.4 million and $19.7 million, respectively. Additionally, other investments include trust certificates issued upon dissolution of a private equity fund of $0.2 million as of September 30, 2014, with no such investment held as of December 31, 2013.
Redemptions of investments in certain funds are subject to restrictions including "lock-up" periods where no redemptions or withdrawals are allowed, restrictions on redemption frequency and advance notice periods for redemptions. Amounts requested for redemptions remain subject to market fluctuations until the redemption effective date, which generally falls at the end of the defined redemption period. The following summarizes the September 30, 2014 fair value of hedge funds subject to restrictions on redemption frequency and advance notice period requirements for investments in active hedge funds:
		Hedge Funds—Active Funds
		30 - 59 days			60 - 89 days			90 - 119 days			120+ days			Total
		notice			notice			notice			notice
		($ in millions)
Redemption frequency
Monthly		$	1.8		$	—		$	—		$	—		$	1.8
Quarterly		28.8			8.5			6			—			43.3
Annual		—			—			2.4			0.1			2.5
Total hedge funds		$	30.6		$	8.5		$	8.4		$	0.1		$	47.6
Certain hedge fund investments are no longer active and are in the process of disposing of their underlying investments. Distributions from such funds are remitted to investors as the fund's underlying investments are liquidated. At September 30, 2014, $0.9 million of hedge funds were in liquidation. The actual amount of the final distribution is subject to market fluctuations. The date at which such distributions will be received is not determinable at September 30, 2014.
OneBeacon has also submitted redemption requests for certain of its investments in active hedge funds. At September 30, 2014, redemptions of $8.5 million were outstanding and are subject to market fluctuations. Such redemptions are expected to be received in the first quarter of 2015. Redemptions are recorded as receivables when the investment is no longer subject to market fluctuations.
Investments in private equity funds are generally subject to lock-up periods during which investors may not request a redemption. Distributions prior to the expected termination date of the fund may be limited to dividends or proceeds arising from the liquidation of the fund's underlying investment. In addition, certain private equity funds provide an option to extend the lock-up period at either the sole discretion of the fund manager or upon agreement between the fund and the investors. At September 30, 2014, investments in private equity funds were subject to lock-up periods as follows:
		1 - 3 years			3 - 5 years			5 - 10 years			>10 years			Total
		($ in millions)
Private Equity Funds—expected lock-up period remaining		$	9.6		$	18.2		$	26.6		$	—		$	54.4

Debt

Debt	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Debt	'
	Debt
	OneBeacon's debt outstanding as of September 30, 2014 and December 31, 2013 consisted of the following:
		September 30,			December 31,
		2014			2013
		($ in millions)
	Senior unsecured notes, at face value	$	275		$	275
	Unamortized original issue discount	(0.3		)	(0.3		)
	Senior unsecured notes, carrying value	$	274.7		$	274.7
	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. OBH incurred $2.8 million in expenses related to the issuance of the 2012 Senior Notes (including the $1.8 million underwriting discount), which were deferred and are being recognized as interest expense over the life of the 2012 Senior Notes. 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.
	Debt Covenants
	At September 30, 2014, OneBeacon was in compliance with all of the covenants under the 2012 Senior Notes.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	Segment Information
	The Company has fourteen underwriting operating segments, including two that were exited in 2013, 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 segment is comprised of eight operating segments, including a new Crop underwriting operating segment, as well as the Collector Cars and Boats underwriting operating segment that was exited in the first quarter of 2013 (see Note 2—"Acquisitions and Dispositions"), representing an aggregation based on those that offer distinct products and tailored coverages and services to a broad customer base across the United States. In addition to Crop and Collector Cars and Boats, the Specialty Products segment includes the Professional Insurance, Specialty Property, Environmental, Tuition Reimbursement, Programs, and Surety underwriting operating segments. During 2013, the Company received approval to provide multiple peril crop insurance through the federal crop insurance program administered by the U.S. Department of Agriculture's Risk Management Agency. The Company entered into an exclusive agreement with a managing general agency, The Climate Corporation, to provide coverages through the federal crop insurance program and other supplemental coverages, including crop-hail. The Company began writing crop business in the fourth quarter of 2013.
	The Specialty Industries segment is comprised of six underwriting operating segments, including the Energy underwriting operating segment that was exited in the first quarter of 2013, 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 International Marine Underwriters, Technology, Accident, Government Risks, and Entertainment underwriting operating segments.
	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.
	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
			Specialty			Specialty			Corporate			Consolidated
			Products			Industries
			($ in millions)
	Three months ended September 30, 2014
	Earned premiums		$	151.7		$	153.7		$	—		$	305.4
	Loss and loss adjustment expense		(98.2		)	(87.0		)	—			(185.2		)
	Policy acquisition expenses		(26.6		)	(28.0		)	—			(54.6		)
	Other underwriting expenses		(23.2		)	(28.0		)	—			(51.2		)
	Total underwriting income		3.7			10.7			—			14.4
	Net investment income		—			—			10.4			10.4
	Net realized and change in unrealized investment gains		—			—			(16.0		)	(16.0		)
	Net other revenues		(0.3		)	0.5			1.1			1.3
	General and administrative expenses		—			(0.8		)	(1.6		)	(2.4		)
	Interest expense		—			—			(3.2		)	(3.2		)
	Pre-tax income (loss) from continuing operations		$	3.4		$	10.4		$	(9.3	)	$	4.5
	Three months ended September 30, 2013
	Earned premiums		$	132.2		$	146.7		$	—		$	278.9
	Loss and loss adjustment expense		(84.2		)	(83.6		)	—			(167.8		)
	Policy acquisition expenses		(27.4		)	(26.2		)	—			(53.6		)
	Other underwriting expenses		(21.2		)	(25.6		)	—			(46.8		)
	Total underwriting income (loss)		(0.6		)	11.3			—			10.7
	Net investment income		—			—			10.1			10.1
	Net realized and change in unrealized investment gains		—			—			17			17
	Net other revenues		—			0.6			4.9			5.5
	General and administrative expenses		—			(1.1		)	(3.0		)	(4.1		)
	Interest expense		—			—			(3.3		)	(3.3		)
	Pre-tax income (loss) from continuing operations		$	(0.6	)	$	10.8		$	25.7		$	35.9
			Insurance Operations						Investing,
									Financing
									and
			Specialty			Specialty			Corporate			Consolidated
			Products			Industries
			($ in millions)
	Nine months ended September 30, 2014
	Earned premiums		$	433		$	439.8		$	—		$	872.8
	Loss and loss adjustment expense		(277.5		)	(243.2		)	—			(520.7		)
	Policy acquisition expenses		(71.4		)	(79.5		)	—			(150.9		)
	Other underwriting expenses		(68.1		)	(84.2		)	—			(152.3		)
	Total underwriting income		16			32.9			—			48.9
	Net investment income		—			—			32.1			32.1
	Net realized and change in unrealized investment gains		—			—			24.8			24.8
	Net other revenues		(0.1		)	0.8			2.6			3.3
	General and administrative expenses		0.1			(1.8		)	(7.6		)	(9.3		)
	Interest expense		—			—			(9.7		)	(9.7		)
	Pre-tax income from continuing operations		$	16		$	31.9		$	42.2		$	90.1
	Nine months ended September 30, 2013
	Earned premiums		$	426.9		$	419.3		$	—		$	846.2
	Loss and loss adjustment expense		(240.6		)	(233.1		)	—			(473.7		)
	Policy acquisition expenses		(84.3		)	(76.6		)	—			(160.9		)
	Other underwriting expenses		(72.5		)	(78.2		)	—			(150.7		)
	Total underwriting income		29.5			31.4			—			60.9
	Net investment income		—			—			30.9			30.9
Net realized and change in unrealized investment gains		—			—			19.9			19.9
Net other revenues		0.3			0.9			28.9			30.1
General and administrative expenses		(0.1		)	(2.3		)	(8.6		)	(11.0		)
Interest expense		—			—			(9.8		)	(9.8		)
Pre-tax income from continuing operations		$	29.7		$	30		$	61.3		$	121
		Insurance Operations						Investing,
								Financing
								and
		Specialty			Specialty			Corporate(1)			Consolidated
		Products			Industries
		($ in millions)
30-Sep-14
Assets
Total investment securities		$	—		$	—		$	2,421.70		$	2,421.70
Reinsurance recoverables		85.5			28.6			—			114.1
Deferred acquisition costs		66			55.8			—			121.8
Liabilities
Unpaid loss and loss adjustment expense reserves		678.2			481.4			—			1,159.60
Unearned premiums		332.4			292.8			—			625.2
Debt		—			—			274.7			274.7
31-Dec-13
Assets
Total investment securities		$	—		$	—		$	2,364.90		$	2,364.90
Reinsurance recoverables		60.2			29.7			—			89.9
Deferred acquisition costs		53.6			50.1			—			103.7
Liabilities
Unpaid loss and loss adjustment expense reserves		607.8			446.5			—			1,054.30
Unearned premiums		275.4			269.5			—			544.9
Debt		—			—			274.7			274.7
_______________________________________________________________________________
(1)As described in Note 2—"Acquisitions and Dispositions," balances related to the the Runoff Business are presented as held for sale. Total investment securities excludes $203.9 million and $236.3 million of fixed maturity investments reclassified to assets held for sale as of September 30, 2014 and December 31, 2013, respectively.
The following tables provide net written premiums, earned premiums and underwriting ratios for OneBeacon's insurance operations by reportable segment and in total, for the three and nine months ended September 30, 2014, and 2013:
		Three months ended September 30, 2014									Three months ended September 30, 2013
		Insurance Operations									Insurance Operations
($ in millions)		Specialty			Specialty			Consolidated			Specialty			Specialty			Consolidated
		Products			Industries						Products			Industries
Net written premiums		$	188.3		$	157.3		$	345.6		$	172		$	142.1		$	314.1
Earned premiums		151.7			153.7			305.4			132.2			146.7			278.9
Underwriting ratios:(1)
Loss and LAE		64.7		%	56.7		%	60.6		%	63.7		%	56.9		%	60.1		%
Expense		32.9			36.4			34.7			36.7			35.4			36
Total combined ratio		97.6		%	93.1		%	95.3		%	100.4		%	92.3		%	96.1		%
		Nine months ended September 30, 2014									Nine months ended September 30, 2013
		Insurance Operations									Insurance Operations
($ in millions)		Specialty			Specialty			Consolidated			Specialty			Specialty			Consolidated
		Products			Industries						Products			Industries
Net written premiums		$	488.6		$	464		$	952.6		$	393.3		$	432.8		$	826.1
Earned premiums		433			439.8			872.8			426.9			419.3			846.2
Underwriting ratios:(1)
Loss and LAE		64.1		%	55.3		%	59.7		%	56.4		%	55.6		%	56		%
Expense		32.2			37.2			34.7			36.7			36.9			36.8
Total combined ratio		96.3		%	92.5		%	94.4		%	93.1		%	92.5		%	92.8		%
_______________________________________________________________________________
-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	9 Months Ended
	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]	'
Retirement Plans	'
	Retirement Plans
	OneBeacon sponsors qualified and non-qualified, non-contributory, defined benefit pension plans 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. Current plans include the OneBeacon qualified pension plan (the "Qualified Plan") and the OneBeacon non-qualified pension plan (the "Non-qualified Plan") (collectively the "Plans"). OneBeacon's Plans were frozen and curtailed in 2002 and, as a result, the projected benefit obligation is equal to the accumulated benefit obligation.
	The benefits for the Plans are based primarily on years of service and employees’ compensation through December 31, 2002. OneBeacon’s funding policy is consistent with the funding requirements of U.S. federal laws and regulations.
	The components of net periodic benefit cost for the three and nine months ended September 30, 2014 and 2013 were as follows:
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
			($ in millions)
	Service cost		$	0.2		$	0.2		$	0.5		$	0.6
	Interest cost		1.2			1.1			3.5			3.2
	Expected return on plan assets		(2.2		)	(1.8		)	(6.4		)	(5.4		)
	Amortization of unrecognized loss		0.1			0.2			0.3			0.7
	Net periodic pension income before special termination benefits		(0.7		)	(0.3		)	(2.1		)	(0.9		)
	Special termination benefits expense(1)		—			—			0.3			0.3
	Total net periodic benefit income		$	(0.7	)	$	(0.3	)	$	(1.8	)	$	(0.6	)
	_______________________________________________________________________________
	-1	Special termination benefits represent additional payments made from the Qualified Plan to certain vested participants when their employment was terminated due to a reduction in force.
	OneBeacon does not expect to make a contribution to its Qualified Plan in 2014. OneBeacon anticipates contributing $2.2 million to the Non-qualified Plan in 2014, for which OneBeacon has assets held in a rabbi trust. During the three and nine months ended September 30, 2014, the Company contributed $0.5 million and $1.6 million, respectively, to the Non-qualified Plan.

Employee_ShareBased_Incentive_

Employee Share-Based Incentive Compensation Plans	9 Months Ended
	Sep. 30, 2014
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 and restricted shares, 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 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. 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 of $1.8 million and $0.8 million for the three months ended September 30, 2014 and 2013, respectively, and $4.8 million and $3.6 million for the nine months ended September 30, 2014 and 2013, respectively.
	Performance Shares
	The following summarizes performance share activity for the three and nine months ended September 30, 2014 and 2013:
			Three months ended September 30,
			2014					2013
			Target OB		Accrued			Target OB		Accrued
			Performance		expense			Performance		expense
			Shares					Shares
			outstanding					outstanding
			($ in millions)
	Beginning of period		512,938		$	4.4		489,867		$	2.4
	Payments and deferrals		—		—			—		—
	New awards		—		—			—		—
	Forfeitures and net change in assumed forfeitures		—		—			—		—
	Expense recognized		—		1.1			—		0.1
	End of period		512,938		$	5.5		489,867		$	2.5
			Nine months ended September 30,
			2014					2013
			Target OB		Accrued			Target OB		Accrued
			Performance		expense			Performance		expense
			Shares					Shares
			outstanding					outstanding
			($ in millions)
	Beginning of period		493,421		$	4		563,190		$	1.2
	Payments and deferrals(1)		(142,138	)	(1.0		)	(238,658	)	—
	New awards		165,800		—			179,000		—
	Forfeitures and net change in assumed forfeitures		(4,145	)	—			(13,665	)	(0.1		)
	Expense recognized		—		2.5			—		1.4
	End of period		512,938		$	5.5		489,867		$	2.5
	_______________________________________________________________________________
	(1)	Performance share payments in 2014 for the 2011-2013 performance cycle were based upon a performance factor of 37.1%. No payments were made in 2013 for the 2010-2012 performance cycle as the performance factor was zero.
	The following summarizes performance shares outstanding and accrued performance share expense at September 30, 2014 for each performance cycle:
			Target OB		Accrued
			Performance		expense
			Shares
			outstanding
			($ in millions)
	Performance cycle:
	2012 - 2014		181,290		$	2.8
	2013 - 2015		179,000		2.2
	2014 - 2016		165,800		0.6
	Subtotal		526,090		5.6
	Assumed forfeitures		(13,152	)	(0.1		)
	Total at September 30, 2014		512,938		$	5.5
	If 100% of the outstanding performance shares had been vested on September 30, 2014, the total additional compensation cost to be recognized would have been $3.7 million, based on current accrual factors (common share price, accumulated dividends and payout assumptions) at September 30, 2014.
	All performance shares earned and paid were settled in cash or by deferral into OneBeacon's deferred compensation plan.
	Restricted Shares
	On March 1, 2012, OneBeacon issued shares of restricted stock to certain employees. Of these restricted shares, 142,500 restricted shares vested on February 28, 2014 and the remaining 140,000 restricted shares outstanding and held by employees as of September 30, 2014 are scheduled to vest on February 28, 2015. On May 25, 2011, OneBeacon issued to its CEO 630,000 shares of restricted stock, of which 157,500 of these restricted shares vested on February 22, 2014 and the remaining 472,500 restricted shares held by the CEO are scheduled to vest in equal installments on February 22, 2015, 2016 and 2017. The restricted shares contain dividend participation features and therefore are considered participating securities.
	The following summarizes restricted shares activity for the three and nine months ended September 30, 2014 and 2013:
			Three months ended September 30,
			2014					2013
			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
			($ in millions)
	Beginning of period		612,500		$	4.9		918,000		$	8
	New awards		—		—			—		—
	Forfeitures		—		—			(3,000	)	—
	Vested		—		—			—		—
	Expense recognized		—		(0.7		)	—		(0.7		)
	End of period		612,500		$	4.2		915,000		$	7.3
			Nine months ended September 30,
			2014					2013
			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
		($ in millions)
Beginning of period		915,000		$	6.5		927,000		$	9.6
New awards		—		—			—		—
Forfeitures		(2,500	)	—			(3,000	)	—
Vested		(300,000	)	—			(9,000	)	—
Expense recognized		—		(2.3		)	—		(2.3		)
End of period		612,500		$	4.2		915,000		$	7.3
Restricted shares that vested during the nine months ended September 30, 2014 and 2013 had a grant date fair value of $4.3 million and $0.1 million, respectively. No restricted shares vested during the three months ended September 30, 2014 or 2013. As of September 30, 2014, unrecognized compensation expense of $4.2 million related to restricted stock awards is expected to be recognized over a weighted-average period of 2.1 years.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2014
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, Luxembourg and the United States. U.S. operations are financed with a combination of debt and equity and the financing income currently accounts for the majority of non-U.S. earnings.
	OneBeacon's income tax expense related to pre-tax income from continuing operations for the three months ended September 30, 2014 and 2013, represented net effective tax rates of (37.8)% and (8.1)%, respectively. The net effective tax rates for the nine months ended September 30, 2014 and 2013 were 11.2% and 13.1%, respectively. The effective tax rates for the three and nine months ended September 30, 2014 and 2013, 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 taxed in a jurisdiction with a lower effective tax rate. Additionally, the rate for the three months ended September 30, 2014 was impacted by a pre-tax loss from operations in the United States and the rate for the nine months ended September 30, 2014 was impacted by a $5.0 million favorable settlement of the 2005-2006 IRS exam, as noted below. The rates for the three and nine months ended September 30, 2013 were impacted by a $6.8 million tax benefit associated with the restructuring of the surplus note issued by Houston General Insurance Exchange. For the three months ended September 30, 2014 and 2013, the effective tax rate on non-U.S. income was 1.7% and 0.5%, respectively. For the nine months ended September 30, 2014 and 2013, the effective tax rate on non-U.S. income was 1.3% and 0.3%, respectively.
	In arriving at the effective tax rate for the three and nine months ended September 30, 2014 and 2013, OneBeacon forecasted all income and expense items including the realized and change in unrealized investment gains for the years ending December 31, 2014 and 2013, and included these gains in the effective tax rate calculation.
	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 2005. On February 14, 2014, OneBeacon received Form 870-AD (Offer to Waive Restrictions on Assessment and Collection Tax Deficiency and to Accept Over assessment) from the IRS Appeals Office relating to the examination of tax years 2005 and 2006. All disputed items have now been agreed and resolved with the Joint Committee. OneBeacon recorded a tax benefit of $5.0 million in the first quarter of 2014 relating to the settlement of the IRS examination for tax years 2005 and 2006.
	On July 28, 2011, the IRS commenced an examination of OneBeacon's U.S. income tax returns for 2007, 2008 and 2009. On July 17, 2013, OneBeacon received a revised Form 4549-A (Income Tax Discrepancy Adjustments) from the IRS relating to the examination of tax years 2007, 2008 and 2009. The estimated total assessment, including interest, utilization of alternative minimum and foreign tax credit carryovers and capital loss carrybacks, is $72.0 million. However, $60.2 million of the proposed adjustments relate to items for which the expense deduction has been disallowed in a year being examined, but ultimate deductibility is highly certain to occur in a later period. Because of the impact of deferred tax accounting, other than interest and penalties, the disallowance of the deduction in the exam period would not affect the effective tax rate but would accelerate the payment of cash to the taxing authority. OneBeacon disagrees with the adjustments proposed by the IRS and is defending its position. Although the timing of the resolution of these issues is uncertain, it is reasonably possible that the resolution could occur within the next twelve months. An estimate of the range of potential outcomes cannot be made at this time. OneBeacon does not expect the resolution of this examination to result in a material change to its financial position.
	On September 2, 2013, the IRS commenced an examination of OneBeacon's U.S. income tax returns for 2010, 2011 and 2012. OneBeacon does not expect the resolution of this examination to result in a material change to its financial position.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2014
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 equity method investments 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, other than financial guarantees, and investment contracts.
	At September 30, 2014 and December 31, 2013, the fair value of OneBeacon's 2012 Senior Notes (its fixed-rate, long-term indebtedness) was $281.4 million and $269.8 million, respectively, which compared to a carrying value of $274.7 million as of both September 30, 2014 and December 31, 2013. The fair value measurement of the Senior Notes is classified as Level 2 in the valuation hierarchy.

Legal_Contingencies

Legal Contingencies	9 Months Ended
	Sep. 30, 2014
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 do 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 September 30, 2014:
	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 Noteholder Actions in September 2013 and Plaintiffs have filed a notice of appeal. Oral argument is scheduled for November 5, 2014.
	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.

Earnings_per_Share

Earnings per Share	9 Months Ended
	Sep. 30, 2014
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 and nine months ended September 30, 2014 and 2013:
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
	Earnings attributable to OneBeacon's common shareholders—basic and diluted (in millions):
	Net income from continuing operations attributable to OneBeacon's common shareholders		$	6.2		$	38.8		$	79.1		$	104.3
	Allocation of income for participating unvested restricted common shares		(0.1		)	(0.4		)	(0.6		)	(1.0		)
	Dividends paid on participating restricted common shares		(0.2		)	(0.2		)	(0.4		)	(0.6		)
	Total allocation to restricted common shares		(0.3		)	(0.6		)	(1.0		)	(1.6		)
	Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts		$	5.9		$	38.2		$	78.1		$	102.7
	Undistributed (overdistributed) net earnings (in millions):
	Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts		$	5.9		$	38.2		$	78.1		$	102.7
	Dividends paid, net of restricted common share amounts		(19.8		)	(19.8		)	(59.6		)	(59.5		)
	Total undistributed (overdistributed) net earnings, net of restricted common share amounts		$	(13.9	)	$	18.4		$	18.5		$	43.2
	Earnings per share denominator—basic and diluted (in millions):
	Total weighted average common shares outstanding		95.3			95.4			95.3			95.4
	Weighted average unvested restricted common shares(1)		(0.6		)	(0.9		)	(0.7		)	(0.9		)
	Basic and diluted earnings per share denominator		94.7			94.5			94.6			94.5
	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		$	0.06		$	0.41		$	0.83		$	1.09
	Dividends declared and paid		(0.21		)	(0.21		)	(0.63		)	(0.63		)
	Undistributed (overdistributed) earnings		$	(0.15	)	$	0.2		$	0.2		$	0.46
	_______________________________________________________________________________
	(1)	Restricted shares outstanding vest in equal installments upon a stated date or upon the occurrence of a specified event.
	Basic and diluted income per share amounts for discontinued operations are included in Note 15—"Discontinued Operations."

Common_Shareholders_Equity

Common Shareholders' Equity	9 Months Ended
	Sep. 30, 2014
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 nine months ended September 30, 2014 and 2013, no shares were repurchased under the share repurchase authorization. The amount of authorization remaining is $87.7 million as of September 30, 2014.
	During the nine months ended September 30, 2014 and 2013, the Company repurchased 106,366 and 3,300 common shares, 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.
	Dividends on Common Shares
	During the nine months ended September 30, 2014 and 2013, the Company declared and paid cash dividends to OneBeacon shareholders of $60.0 million and $60.1 million, respectively, or $0.63 per common share for each nine month period.
	Accumulated Other Comprehensive Income
	For the nine months ended September 30, 2014 and 2013, OneBeacon recorded pre-tax changes to accumulated other comprehensive income for net increases in net benefit plan assets and obligations of $0.2 million ($0.1 million after tax) and $0.7 million ($0.5 million after tax), respectively.

Discontinued_Operations

Discontinued Operations	9 Months Ended
	Sep. 30, 2014
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,” in October 2012, OneBeacon entered into the Stock Purchase Agreement with respect to the sale of its Runoff Business to Armour. Pursuant to the terms of the Stock Purchase Agreement, at closing, OneBeacon will transfer to Armour all of the issued and outstanding shares of common stock of certain legal entities that will contain the assets, liabilities (including gross and ceded loss reserves) and capital supporting the business as well as certain elements of the Runoff Business infrastructure, including staff and office space. As disclosed in the Form 8-K filed by the Company on June 23, 2014, the Company amended the Stock Purchase Agreement during the second quarter of 2014, primarily to increase the cap on seller financing by $6.7 million to $80.9 million, as well as to extend the termination date to December 31, 2014. Consistent with the proposed closing balance sheet, pro forma as of June 30, 2014, the Company expects to provide seller financing at closing in the form of surplus notes with an estimated par value of $80.9 million. The loss on sale of the Runoff Business is currently estimated at $80.5 million.
	The estimated loss on sale may change prior to closing as a result of, among other factors, changes in the estimated fair value of the surplus notes. The internal valuation model used to estimate the fair value of the surplus notes is sensitive to changes in treasury rates and credit spreads, and to 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 and likelihood of interest and principal payments on the notes, which are subject to regulatory approval and therefore may vary from the contractual terms. Although these variables involve considerable judgment, the Company does not currently expect any resulting change in the estimated value of the surplus notes to be material to its financial position.
	In anticipation of the Runoff Transaction, OneBeacon received regulatory approval as required from various state departments of insurance effective October 1, 2012 to terminate the then-existing pooling agreement and intercompany 100% quota share reinsurance agreements and to enter into new 100% quota share reinsurance agreements. The result is that the Runoff Business is assumed and retained by OBIC, one of the legal entities that will be transferred to Armour at closing, and that the ongoing specialty business is assumed and retained by Atlantic Specialty Insurance Company ("ASIC"), one of the entities that OneBeacon will continue to own post-closing.
	The Runoff Transaction is subject to various closing conditions, primarily the receipt of regulatory approvals. The Pennsylvania Insurance Department is currently conducting its regulatory review of the Runoff Transaction, which included a public hearing on July 23, 2014. Subsequent to the public hearing, the Pennsylvania Insurance Department re-opened the public comment period, which expired on October 17, 2014. The regulatory review process included a third party actuarial review of the Runoff Business loss and LAE reserves, completed in September 2013 and, subsequently, an independent stochastic modeling of the future cash flows of the Runoff Business, which was completed in June 2014. The Company expects the Runoff Transaction to close in the fourth quarter of 2014.
	Summary of Reclassified Balances and Related Items
	As of September 30, 2014 and December 31, 2013, the Runoff Transaction met the criteria for held for sale accounting. As a result, the assets and liabilities associated with the businesses being sold, after effecting the various steps contemplated by the Stock Purchase Agreement, are presented separately as single line items in the asset and liability sections of the consolidated balance sheets as of September 30, 2014 and December 31, 2013. The following summarizes the major categories of assets and liabilities associated with the business classified as held for sale:
			September 30,			December 31,
			2014			2013
			($ in millions)
	Assets:
	Investments		$	203.9		$	236.3
	Premiums receivable		11.6			9.1
	Reinsurance recoverables on unpaid losses(1)		1,458.40			1,604.70
	Reinsurance recoverables on paid losses		7.4			10.7
	Net deferred tax asset		2.5			3.3
	Other assets		15.4			16
	Total assets held for sale		$	1,699.20		$	1,880.10
	Liabilities:
	Unpaid loss and loss adjustment expense reserves(1)		$	1,600.90		$	1,793.10
	Unearned premiums		—			0.2
	Ceded reinsurance payable		12.1			12.3
	Other liabilities(2)		86.2			74.5
	Total liabilities held for sale		$	1,699.20		$	1,880.10
	_______________________________________________________________________________
	-1	The September 30, 2014 and December 31, 2013 balances include the remaining purchase accounting fair value adjustments of $127.0 million and $136.9 million, respectively, relating to the OneBeacon Acquisition. As of September 30, 2014 and December 31, 2013, reinsurance recoverables on unpaid losses, gross of purchase accounting adjustments, were $1,585.4 million and $1,741.6 million, respectively, and unpaid loss and LAE reserves, gross of purchase accounting adjustments, were $1,727.9 million and $1,930.0 million for each period.
	-2	Other liabilities as of September 30, 2014 and December 31, 2013 include the accrual related to the pre-tax loss on sale of the Runoff Business of $80.5 million and $69.0 million, respectively.
	As described in Note 1—"Nature of Operations and Summary of Significant Accounting Policies" and Note 2—“Acquisitions and Dispositions,” the results of operations for the Runoff Business have been classified as discontinued operations and are presented as such, net of related income taxes, in the statements of operations and comprehensive income (loss) and cash flows for all periods. Investing and financing activities for OneBeacon are managed on a consolidated basis and reported within the Investing, Financing and Corporate segment. Therefore, no investment or financing activity is included in discontinued operations.
	The following summarizes the results of operations, including related income taxes associated with the business classified as discontinued operations:
			Three months ended							Nine months ended
			September 30,							September 30,
			2014			2013				2014			2013
			($ in millions)
	Net written premiums		$	0.1		$	1			$	(0.1	)	$	0.4
	Revenues
	Earned premiums		$	0.3		$	1.1			$	0.1		$	0.7
	Other revenue		—			—				—			7.8
	Total revenues		0.3			1.1				0.1			8.5
	Expenses
	Loss and loss adjustment expenses		—			0.1				(0.7		)	7.6
	Policy acquisition expenses		0.1			0.1				0.1			0.1
	Other underwriting expenses		0.8			0.4				2.2			0.3
	Total expenses		0.9			0.6				1.6			8
	Pre-tax income (loss)		(0.6		)	0.5				(1.5		)	0.5
	Income tax (expense) benefit		0.3			(0.2		)		0.6			(0.2		)
	Income (loss) from discontinued operations, net of tax		(0.3		)	0.3				(0.9		)	0.3
	Loss from sale of discontinued operations, net of tax		(7.0		)	—				(7.5		)	—
	Net income (loss) from discontinued operations, net of tax		$	(7.3	)	$	0.3			$	(8.4	)	$	0.3
	Loss per Share Related to Discontinued Operations
	Basic loss per share amounts are based on the weighted average number of common shares outstanding including unvested restricted shares that are considered participating securities. Diluted loss per share amounts are based on the weighted average number of common shares including unvested restricted shares.
	The following table outlines the computation of loss per share for discontinued operations attributable to OneBeacon's common shareholders for the three and nine months ended September 30, 2014 and 2013:
			Three months ended							Nine months ended
			September 30,							September 30,
			2014			2013				2014			2013
	Income (loss) attributable to OneBeacon's common shareholders—basic and diluted (in millions):
	Net income (loss) from discontinued operations attributable to OneBeacon's common shareholders		$	(7.3	)	$	0.3			$	(8.4	)	$	0.3
	Allocation of income (loss) for participating unvested restricted common shares		0.1			—				0.1			—
	Net income (loss) from discontinued operations attributable to OneBeacon's common shareholders, net of restricted common share amounts		$	(7.2	)	$	0.3			$	(8.3	)	$	0.3
	Income (loss) per share denominator—basic and diluted (in millions):
	Total weighted average common shares outstanding		95.3			95.4				95.3			95.4
	Weighted average unvested restricted common shares(1)		(0.6		)	(0.9		)		(0.7		)	(0.9		)
	Basic and diluted income (loss) per share denominator		94.7			94.5				94.6			94.5
Loss per share attributable to OneBeacon's common shareholders—basic and diluted (in dollars):
Loss from discontinued operations attributable to OneBeacon's common shareholders per share		$	(0.07	)	$	—			$	(0.09	)	$	—
_______________________________________________________________________________
(1)	Restricted shares outstanding vest in equal installments upon a stated date or upon the occurrence of a specified event.
Additional Disclosures
Due to the relative significance of the transactions described above, OneBeacon has expanded the disclosures herein to provide additional insight into the balances and related activity reclassified to held for sale and discontinued operations.
Results of Discontinued Operations
The net income (loss) from discontinued operations, which is net of income taxes, includes both the income (loss) from discontinued operations, which is the underwriting impact of discontinued operations, as well as the estimated loss from sale of discontinued operations. The net income (loss) from discontinued operations was a net loss of $7.3 million for the three months ended September 30, 2014, compared to net income of $0.3 million for the three months ended September 30, 2013. The net income (loss) from discontinued operations was a net loss of $8.4 million for the nine months ended September 30, 2014, compared to net income of $0.3 million for the nine months ended September 30, 2013.
The loss from discontinued operations for the three and nine months ended September 30, 2014 of $0.3 million and $0.9 million, respectively, was a result of non-claims expenses related to the Runoff Business, including dedicated staff. Income from discontinued operations for both the three and nine months ended September 30, 2013 was $0.3 million. The income for the nine months ended September 30, 2013 is net of other revenue of $7.8 million associated with a settlement award in the Safeco v. American International Group, Inc. (“AIG”) class action related to AIG's alleged underreporting of workers' compensation premiums to the National Workers' Compensation Reinsurance Pool. Partially offsetting this increase in other revenue in 2013, the Company increased loss and LAE reserves in the second quarter of 2013 by $7.4 million in light of the ongoing regulatory review of the Runoff Transaction, which included a third party actuarial review.
The loss from sale of discontinued operations, net of tax, for the three and nine months ended September 30, 2014 was $7.0 million and $7.5 million, respectively, compared to no impact to loss on sale for either the three or nine months ended September 30, 2013. The adjusted estimated loss on sale as of September 30, 2014 is $80.5 million, pre-tax.
As disclosed in the Form 8-K filed by the Company on June 23, 2014, the Company amended the Stock Purchase Agreement during the second quarter of 2014, primarily to increase the cap on seller financing by $6.7 million to $80.9 million, as well as to extend the termination date to December 31, 2014. Consistent with the proposed closing balance sheet, pro forma as of June 30, 2014, the Company expects to provide seller financing at closing in the form of surplus notes with an estimated par value of $80.9 million. When issued, the Company will record these surplus notes at their estimated fair value at that time which, based on the internal valuation models, are expected to be less than their par value. As of June 30, 2014, the estimated fair value of the surplus notes was $8.2 million, pre-tax, less than their par value. As a result, in the second quarter of 2014, the Company recorded an increase of $8.2 million ($5.3 million after tax) in the estimated loss on sale of the Runoff Business to reflect the estimated difference between the estimated fair value at that time and par value of the surplus notes upon issuance.
Also at that time, the Company's expectation of the treatment under the Stock Purchase Agreement of the $7.4 million reserve charge recorded during the quarter ended June 30, 2013 changed. Previously, the Company had expected that the Stock Purchase Agreement would be amended to provide for the transfer of $7.4 million of additional assets to support this reserve charge; as previously noted, the Stock Purchase Agreement was instead revised to increase the cap on seller financing. As a result, the $7.4 million reserve charge ($4.8 million after-tax) was recorded as a reduction to the estimated loss on sale of discontinued operations during the quarter ended June 30, 2014.
In the third quarter of 2014, the Company updated its estimated loss on sale to reflect the change in the valuation of the $80.9 million face value of surplus notes expected to be issued in conjunction with the closing of the Runoff Transaction. The change in the valuation estimate resulted in an additional loss of $10.3 million, pre-tax, which was a result of widening credit spreads during the quarter, as well as an increase to the estimated discount rate related to the private nature of the notes (and the related lack of liquidity). This additional loss results in the total valuation impact included in the estimated loss on sale from discontinued operations, as pertains to the $80.9 million par value surplus notes, to $18.5 million, or an estimated fair value of $62.4 million for the surplus notes.
The $7.0 million after-tax change to the estimated loss on sale in the third quarter of 2014 was primarily driven by the $10.3 million, pre-tax, change in valuation estimate described above. The nine months ended September 30, 2014 loss on sale of $7.5 million included both the $7.0 million from the third quarter, as well as the net effect of the two items from the second quarter, as described in more detail above.
These changes, along with certain other adjustments, resulted in a net increase in the estimated loss on sale of $11.5 million ($7.5 million after tax) during the nine months ended September 30, 2014, resulting in a revised pre-tax estimated loss on sale of $80.5 million ($52.4 million after tax). The estimated loss on sale may change prior to closing as a result of, among other factors, changes in the estimated fair value of these surplus notes.
As of September 30, 2014, the recorded net unpaid loss and LAE reserves associated with the Runoff Business totaled $142.5 million. Management believes that the recorded net loss and LAE reserves reflect a reasonable provision for expected future loss and LAE payments and represent management’s best estimate within a range of reasonable estimates.
OneBeacon made loss and LAE payments of $16.4 million and $17.4 million for the three months ended September 30, 2014 and 2013, respectively, and $45.2 million and $88.8 million for the nine months ended September 30, 2014 and 2013, respectively.
Fair Value Adjustment
In connection with purchase accounting for the OneBeacon Acquisition, the Company was required to adjust to fair value the loss and LAE reserves and the related reinsurance recoverables. Loss and LAE reserves and the related reinsurance recoverables presented in the summary of reclassified balances within assets and liabilities held for sale as of September 30, 2014 and December 31, 2013, are net of $127.0 million and $136.9 million, respectively, related to the outstanding pre-tax unaccreted adjustment.
Reinsurance
As described in Note 4—"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.
In connection with the OneBeacon Acquisition, Aviva caused OneBeacon to purchase two reinsurance contracts from subsidiaries of Berkshire Hathaway Inc.: a reinsurance contract with National Indemnity Company (“NICO”) for up to $2.5 billion in old asbestos and environmental ("A&E") claims and certain other exposures (the “NICO Cover”) and an adverse loss reserve development cover from General Reinsurance Corporation (“GRC”) for up to $570.0 million, comprised of $400.0 million of adverse loss reserve development occurring in years 2000 and prior (the “GRC Cover”) in addition to $170.0 million of reserves ceded as of the date of the OneBeacon Acquisition. The NICO Cover and GRC Cover, which were contingent on and occurred contemporaneously with the OneBeacon Acquisition, were put in place in lieu of a seller guarantee of loss and LAE reserves and are therefore accounted for under GAAP as a seller guarantee.
NICO Cover
Under the terms of the NICO Cover, NICO receives the economic benefit of reinsurance recoverables from certain of OneBeacon’s third party reinsurers (“Third Party Reinsurers”) in existence at the time the NICO Cover was executed (“Third Party Recoverables”). As a result, the underlying Third Party Recoverables serve to protect the $2.5 billion limit of NICO coverage for the benefit of OneBeacon. OneBeacon estimates that on an incurred basis it has used approximately $2.3 billion of the coverage provided by NICO at September 30, 2014. Net losses paid totaled approximately $1.7 billion as of September 30, 2014. To the extent that actual experience differs from OneBeacon’s estimate of ultimate A&E losses and Third-Party Recoverables, future losses could exceed the $198.3 million of protection remaining under the NICO Cover at September 30, 2014.
GRC Cover
Pursuant to the GRC Cover, OneBeacon is not entitled to recover losses to the full contract limit if such losses are reimbursed by GRC more quickly than anticipated at the time the contract was signed. OneBeacon intends to seek reimbursement from GRC only for claims which result in payment patterns similar to those supporting its recoverables recorded pursuant to the GRC Cover. The economic cost of not submitting certain other eligible claims to GRC is primarily the investment spread between the rate credited by GRC and the rate achieved by OneBeacon on its own investments. This cost, if any, is expected to be nominal. As of September 30, 2014, OneBeacon has ceded estimated incurred losses of $562.0 million to GRC under the GRC Cover. As of September 30, 2014, OneBeacon has $337.3 million of reinsurance recoverables on unpaid losses outstanding under the GRC Cover.
At September 30, 2014, OneBeacon had $7.4 million of reinsurance recoverables on paid losses and $1,585.4 million (gross of $127.0 million in purchase accounting adjustments, as described above) that will become recoverable if claims are paid in accordance with current reserve estimates, related to the Runoff Business that have been reclassified to assets held for sale. Reinsurance contracts do not relieve OneBeacon of its obligations. Therefore, collectibility of balances due from reinsurers is critical to OneBeacon's financial strength. The following table provides a listing of the top reinsurers related to the Runoff Business reported in assets held for sale, excluding industry pools and associations, based on reinsurance recoverable amounts on paid and unpaid losses, the percentage of the total reported as held for sale (gross of the $127.0 million in purchase accounting adjustment), and the reinsurers' A.M. Best ratings.
($ in millions)		Balance at			% of total			A.M. Best
		30-Sep-14						Rating(1)
National Indemnity Company ("NICO") and General Reinsurance Corporation(2)		$	1,127.40		71	%		A++
Hanover Insurance Company		30.7			2	%		A
Munich Reinsurance America		28.3			2	%		A++
Tokio Marine and Nichido Fire(3)		25.4			2	%		A+
Everest Reinsurance		14			1	%		A+
_______________________________________________________________________________
-1	A.M. Best ratings as detailed above are: “A++” (Superior, which is the highest of sixteen financial strength ratings), “A+” (Superior, which is the second highest of sixteen financial strength ratings), and “A” (Excellent, which is the third highest of sixteen financial strength ratings).
-2	Includes $198.3 million of Third Party Recoverables, which NICO would pay under the terms of the NICO Cover if they are unable to collect from third party reinsurers.
-3	Excludes $21.8 million of reinsurance recoverables from the various reinsurers that are guaranteed by Tokio Marine and Nichido Fire.

Consolidating_Financial_Inform

Consolidating Financial Information	9 Months Ended
	Sep. 30, 2014
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. The following tables present OneBeacon's consolidating balance sheets as of September 30, 2014 and December 31, 2013 and statements of operations and comprehensive income for the three and nine months ended September 30, 2014 and 2013 and cash flows for the nine months ended September 30, 2014 and 2013. 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	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
	as of September 30, 2014	(in millions)
	Assets
	Investment Securities:
	Fixed maturity investments, at fair value	$	—		$	1,738.40		$	2.9		$	(25.6	)	$	1,715.70
	Short-term investments, at amortized cost (which approximates fair value)	10.3			224.8			3.3			—			238.4
	Common equity securities, at fair value	—			315.5			—			—			315.5
	Convertible fixed maturity investments, at fair value	—			17.3			—			—			17.3
	Other investments	—			134.8			—			—			134.8
	Total investment securities	10.3			2,430.80			6.2			(25.6		)	2,421.70
	Cash	—			187.5			—			—			187.5
	Reinsurance recoverables	—			114.1			—			—			114.1
	Premiums receivable	—			283.7			—			—			283.7
	Deferred acquisition costs	—			121.8			—						121.8
	Net deferred tax asset	—			86.4			—			0.3			86.7
	Investment income accrued	—			9.8			—			(0.5		)	9.3
	Accounts receivable on unsettled investment sales	—			22			—			—			22
	Investments in subsidiaries	1,106.90			—			1,079.40			(2,186.3		)	—
	Other assets	0.5			304.3			2.4			—			307.2
	Assets held for sale	—			1,699.20			—			—			1,699.20
	Total assets	$	1,117.70		$	5,259.60		$	1,088.00		$	(2,212.1	)	$	5,253.20
	Liabilities
	Unpaid loss and loss adjustment expense reserves	$	—		$	1,159.60		$	—		$	—		$	1,159.60
	Unearned premiums	—			625.2			—			—			625.2
	Debt	—			—			299.7			(25.0		)	274.7
	Accounts payable on unsettled investment purchases	—			23.5			—			—			23.5
	Other liabilities	2.1			340			10.5			(0.5		)	352.1
	Liabilities held for sale	—			1,699.20			—			—			1,699.20
	Total liabilities	2.1			3,847.50			310.2			(25.5		)	4,134.30
	OneBeacon's common shareholders' equity and noncontrolling interests
	Total OneBeacon's common shareholders' equity	1,115.60			1,408.80			777.8			(2,186.6		)	1,115.60
	Total noncontrolling interests	—			3.3			—			—			3.3
	Total OneBeacon's common shareholders' equity and noncontrolling interests	1,115.60			1,412.10			777.8			(2,186.6		)	1,118.90
	Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	$	1,117.70		$	5,259.60		$	1,088.00		$	(2,212.1	)	$	5,253.20
	Consolidating Balance Sheet	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
	as of December 31, 2013	(in millions)
	Assets
	Investment Securities:
	Fixed maturity investments, at fair value	$	—		$	1,725.40		$	—		$	(24.5	)	$	1,700.90
	Short-term investments, at amortized cost (which approximates fair value)	13			140			4			—			157
	Common equity securities, at fair value	—			336.9			—			—			336.9
	Convertible fixed maturity investments, at fair value	—			30.5			—			—			30.5
	Other investments	—			139.6			—			—			139.6
	Total investment securities	13			2,372.40			4			(24.5		)	2,364.90
	Cash	—			166.6			1.5			—			168.1
	Reinsurance recoverables	—			89.9			—			—			89.9
	Premiums receivable	—			228.2			—			—			228.2
	Deferred acquisition costs	—			103.7			—			—			103.7
	Net deferred tax asset	—			93.1			(2.4		)	(0.1		)	90.6
	Investment income accrued	—			10.3			—			(0.2		)	10.1
	Accounts receivable on unsettled investment sales	—			3.3			—			—			3.3
	Investments in subsidiaries	1,092.00			—			1,034.90			(2,126.9		)	—
	Other assets	(0.8		)	272.4			1.1			—			272.7
	Assets held for sale	—			1,880.10			—			—			1,880.10
	Total assets	$	1,104.20		$	5,220.00		$	1,039.10		$	(2,151.7	)	$	5,211.60
	Liabilities
	Unpaid loss and loss adjustment expense reserves	$	—		$	1,054.30		$	—		$	—		$	1,054.30
	Unearned premiums	—			544.9			—			—			544.9
	Debt	—			—			299.7			(25.0		)	274.7
	Accounts payable on unsettled investment purchases	—			11.6			—			—			11.6
	Other liabilities	(0.1		)	335			3.9			(0.2		)	338.6
Liabilities held for sale	—			1,880.10			—			—			1,880.10
Total liabilities	(0.1		)	3,825.90			303.6			(25.2		)	4,104.20
OneBeacon's common shareholders' equity and noncontrolling interests
Total OneBeacon's common shareholders' equity	1,104.30			1,391.00			735.5			(2,126.5		)	1,104.30
Total noncontrolling interests	—			3.1			—			—			3.1
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,104.30			1,394.10			735.5			(2,126.5		)	1,107.40
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	$	1,104.20		$	5,220.00		$	1,039.10		$	(2,151.7	)	$	5,211.60
Consolidating Statement of Operations and Comprehensive Income (Loss)	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
Three months ended September 30, 2014	(in millions)
Revenues
Earned premiums	$	—		$	305.4		$	—		$	—		$	305.4
Net investment income	—			10.7			—			(0.3		)	10.4
Net realized and change in unrealized investment gains	—			(16.3		)	—			0.3			(16.0		)
Net other revenues	—			1.3			—			—			1.3
Total revenues	—			301.1			—			—			301.1
Expenses
Loss and loss adjustment expenses	—			185.2			—			—			185.2
Policy acquisition expenses	—			54.6			—			—			54.6
Other underwriting expenses	—			51.2			—			—			51.2
General and administrative expenses	0.5			1.9			—			—			2.4
Interest expense	—			—			3.5			(0.3		)	3.2
Total expenses	0.5			292.9			3.5			(0.3		)	296.6
Pre-tax income (loss) from continuing operations	(0.5		)	8.2			(3.5		)	0.3			4.5
Income tax benefit	—			1.6			0.3			(0.2		)	1.7
Net income (loss) from continuing operations	(0.5		)	9.8			(3.2		)	0.1			6.2
Loss from discontinued operations, net of tax	—			(0.3		)	—			—			(0.3		)
Loss from sale of discontinued operations, net of tax	—			(7.0		)	—			—			(7.0		)
Income (loss) before equity in earnings of unconsolidated affiliates	(0.5		)	2.5			(3.2		)	0.1			(1.1		)
Equity in earnings of subsidiaries, net of tax	(0.6		)	—			(3.6		)	4.2			—
Net income (loss) including noncontrolling interests	(1.1		)	2.5			(6.8		)	4.3			(1.1		)
Less: Net income attributable to noncontrolling interests	—			—			—			—			—
Net income (loss) attributable to OneBeacon's common shareholders	(1.1		)	2.5			(6.8		)	4.3			(1.1		)
Other comprehensive income, net of tax	—			—			—			—			—
Comprehensive income (loss) attributable to OneBeacon's common shareholders	$	(1.1	)	$	2.5		$	(6.8	)	$	4.3		$	(1.1	)
Consolidating Statement of Operations and Comprehensive Income	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
Three months ended September 30, 2013	(in millions)
Revenues
Earned premiums	$	—		$	278.9		$	—		$	—		$	278.9
Net investment income	—			10.2			0.2			(0.3		)	10.1
Net realized and change in unrealized investment gains	—			17.2			(0.4		)	0.2			17
Net other revenues	—			5.5			—			—			5.5
Total revenues	—			311.8			(0.2		)	(0.1		)	311.5
Expenses
Loss and loss adjustment expenses	—			167.8			—			—			167.8
Policy acquisition expenses	—			53.6			—			—			53.6
Other underwriting expenses	—			46.8			—			—			46.8
General and administrative expenses	1.7			2.2			0.2			—			4.1
Interest expense	—			—			3.5			(0.2		)	3.3
Total expenses	1.7			270.4			3.7			(0.2		)	275.6
Pre-tax income (loss) from continuing operations	(1.7		)	41.4			(3.9		)	0.1			35.9
Income tax benefit	—			0.5			2.5			(0.1		)	2.9
Net income (loss) from continuing operations	(1.7		)	41.9			(1.4		)	—			38.8
Income from discontinued operations, net of tax	—			0.3			—			—			0.3
Net income (loss) before equity in earnings of unconsolidated affiliates	(1.7		)	42.2			(1.4		)	—			39.1
Equity in earnings of subsidiaries, net of tax(1)	40.8			—			34			(74.8		)	—
Net income including noncontrolling interests(1)	39.1			42.2			32.6			(74.8		)	39.1
Less: Net income attributable to noncontrolling interests	—			—			—			—			—
Net income attributable to OneBeacon's common shareholders(1)	39.1			42.2			32.6			(74.8		)	39.1
Other comprehensive income, net of tax	0.2			—			0.2			(0.2		)	0.2
Comprehensive income attributable to OneBeacon's common shareholders(1)	$	39.3		$	42.2		$	32.8		$	(75.0	)	$	39.3
_______________________________________________________________________________
(1) "The Company (guarantor)" column's equity in earnings of subsidiaries, net of tax, for the three months ended September 30, 2013, has been revised from the prior year's presentation to appropriately reflect the earnings for that period. This item was reduced by $3.7 million and offset in the "Consolidating adjustments" column.
Consolidating Statement of Operations and Comprehensive Income	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
Nine months ended September 30, 2014	(in millions)
Revenues
Earned premiums	$	—		$	872.8		$	—		$	—		$	872.8
Net investment income	—			32.9			0.1			(0.9		)	32.1
Net realized and change in unrealized investment gains	—			25.8			—			(1.0		)	24.8
Net other revenues	—			3.3			—			—			3.3
Total revenues	—			934.8			0.1			(1.9		)	933
Expenses
Loss and loss adjustment expenses	—			520.7			—			—			520.7
Policy acquisition expenses	—			150.9			—			—			150.9
Other underwriting expenses	—			152.3			—			—			152.3
General and administrative expenses	4			5.1			0.2			—			9.3
Interest expense	—			—			10.6			(0.9		)	9.7
Total expenses	4			829			10.8			(0.9		)	842.9
Pre-tax income (loss) from continuing operations	(4.0		)	105.8			(10.7		)	(1.0		)	90.1
Income tax (expense) benefit	—			(13.9		)	3.5			0.3			(10.1		)
Net income (loss) from continuing operations	(4.0		)	91.9			(7.2		)	(0.7		)	80
Loss from discontinued operations, net of tax	—			(0.9		)	—			—			(0.9		)
Loss from sale of discontinued operations, net of tax	—			(7.5		)	—			—			(7.5		)
Income (loss) before equity in earnings of unconsolidated affiliates	(4.0		)	83.5			(7.2		)	(0.7		)	71.6
Equity in earnings of subsidiaries, net of tax	74.7			—			49.3			(124.0		)	—
Net income including noncontrolling interests	70.7			83.5			42.1			(124.7		)	71.6
Less: Net income attributable to noncontrolling interests	—			(0.9		)	—			—			(0.9		)
Net income attributable to OneBeacon's common shareholders	70.7			82.6			42.1			(124.7		)	70.7
Other comprehensive income, net of tax	0.1			—			0.1			(0.1		)	0.1
Comprehensive income attributable to OneBeacon's common shareholders	$	70.8		$	82.6		$	42.2		$	(124.8	)	$	70.8
Consolidating Statement of Operations and Comprehensive Income	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
Nine months ended September 30, 2013	(in millions)
Revenues
Earned premiums	$	—		$	846.2		$	—		$	—		$	846.2
Net investment income (expense)	—			32.1			(0.3		)	(0.9		)	30.9
Net realized and change in unrealized investment gains	—			19.7			(0.8		)	1			19.9
Net other revenues	—			30.1			—			—			30.1
Total revenues	—			928.1			(1.1		)	0.1			927.1
Expenses
Loss and loss adjustment expenses	—			473.7			—			—			473.7
Policy acquisition expenses	—			160.9			—			—			160.9
Other underwriting expenses	—			150.7			—			—			150.7
General and administrative expenses	3.6			7.5			(0.1		)	—			11
Interest expense	—			—			10.6			(0.8		)	9.8
Total expenses	3.6			792.8			10.5			(0.8		)	806.1
Pre-tax income (loss) from continuing operations	(3.6		)	135.3			(11.6		)	0.9			121
Income tax (expense) benefit	0.1			(23.3		)	7.7			(0.4		)	(15.9		)
Net income (loss) from continuing operations	(3.5		)	112			(3.9		)	0.5			105.1
Income from discontinued operations, net of tax	—			0.3			—			—			0.3
Net (loss) income before equity in earnings of unconsolidated affiliates	(3.5		)	112.3			(3.9		)	0.5			105.4
Equity in earnings of subsidiaries, net of tax(1)	108.1			—			91.6			(199.7		)	—
Net income including noncontrolling interests(1)	104.6			112.3			87.7			(199.2		)	105.4
Less: Net income attributable to noncontrolling interests	—			(0.8		)	—			—			(0.8		)
Net income attributable to OneBeacon's common shareholders(1)	104.6			111.5			87.7			(199.2		)	104.6
Other comprehensive income, net of tax	0.5			—			0.5			(0.5		)	0.5
Comprehensive income attributable to OneBeacon's common shareholders(1)	$	105.1		$	111.5		$	88.2		$	(199.7	)	$	105.1
_______________________________________________________________________________
(1) "The Company (guarantor)" column's equity in earnings of subsidiaries, net of tax, for the nine months ended September 30, 2013, has been revised from the prior year's presentation to appropriately reflect the earnings for that period. This item was reduced by $3.7 million and offset in the "Consolidating adjustments" column.
Consolidating Statement of Cash Flows	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
Nine months ended September 30, 2014	($ in millions)
Cash flows from operations:
Net income including noncontrolling interests	$	70.7		$	83.5		$	42.1		$	(124.7	)	$	71.6
Charges (credits) to reconcile net income to cash flows provided from (used for) operations:
Undistributed earnings from subsidiaries	(74.7		)	—			(49.3		)	124			—
Net loss from discontinued operations	—			0.9			—			—			0.9
Net loss from sale of discontinued operations	—			7.5			—			—			7.5
Net realized and change in unrealized investment gains	—			(25.8		)	—			1			(24.8		)
Deferred income tax expense	—			9			—			(0.4		)	8.6
Dividends received from subsidiaries	60.4			—			5			(65.4		)	—
Other operating items:
Net change in loss and LAE reserves	—			105.3			—			—			105.3
Net change in unearned premiums	—			80.3			—			—			80.3
Net change in premiums receivable	—			(55.5		)	—			—			(55.5		)
Net change in reinsurance recoverables on paid and unpaid losses	—			(24.2		)	—			—			(24.2		)
Net change in other assets and liabilities	2.7			(28.4		)	2.8			0.1			(22.8		)
Net cash provided from operations—continuing operations	59.1			152.6			0.6			(65.4		)	146.9
Net cash used for operations—discontinued operations	—			(44.8		)	—			—			(44.8		)
Net cash provided from (used for) operations	59.1			107.8			0.6			(65.4		)	102.1
Cash flows from investing activities:
Net maturities, purchases and sales of short-term investments	2.7			(84.9		)	0.7			—			(81.5		)
Maturities of fixed maturity investments	—			202.6			—			—			202.6
Sales of fixed maturity investments	—			1,450.00			9.6			—			1,459.60
Sales of common equity securities	—			97.5			—			—			97.5
Sales of convertible fixed maturity investments	—			20.6			—			—			20.6
Return of capital and distributions of other investments	—			11.1			—			—			11.1
Purchases of fixed maturity investments	—			(1,628.8		)	(12.4		)	—			(1,641.2		)
Purchases of common equity securities	—			(63.0		)	—			—			(63.0		)
Purchases of convertible fixed maturity investments	—			(11.3		)	—			—			(11.3		)
Contributions for other investments	—			(3.6		)	—			—			(3.6		)
Net change in unsettled investment purchases and sales	—			(6.8		)	—			—			(6.8		)
Net acquisitions of property and equipment	—			(0.9		)	—			—			(0.9		)
Net cash provided from (used for) investing activities—continuing operations	2.7			(17.5		)	(2.1		)	—			(16.9		)
Net cash provided from investing activities—discontinued operations	—			—			—			—			—
Net cash provided from (used for) investing activities	2.7			(17.5		)	(2.1		)	—			(16.9		)
Cash flows from financing activities:
Cash dividends paid to common shareholders	(60.0		)	—			—			—			(60.0		)
Cash dividends paid to parent	—			(65.4		)	—			65.4			—
Repurchases and retirements of common stock	(1.8		)	—			—			—			(1.8		)
Payments on capital lease obligation	—			(4.0		)	—			—			(4.0		)
Net cash used for financing activities—continuing operations	(61.8		)	(69.4		)	—			65.4			(65.8		)
Net cash used for financing activities—discontinued operations	—			—			—			—			—
Net cash used for financing activities	(61.8		)	(69.4		)	—			65.4			(65.8		)
Net increase (decrease) in cash during period	—			20.9			(1.5		)	—			19.4
Cash balance at beginning of period	—			166.6			1.5			—			168.1
Cash balance at end of period	$	—		$	187.5		$	—		$	—		$	187.5
Consolidating Statement of Cash Flows	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
Nine months ended September 30, 2013	($ in millions)
Cash flows from operations:
Net income including noncontrolling interests(1)	$	104.6		$	112.3		$	87.7		$	(199.2	)	$	105.4
Charges (credits) to reconcile net income to cash flows provided from (used for) operations:
Undistributed earnings from subsidiaries(1)	(108.1		)	—			(91.6		)	199.7			—
Net income from discontinued operations	—			(0.3		)	—			—			(0.3		)
Net realized and change in unrealized investment gains	—			(19.7		)	0.8			(1.0		)	(19.9		)
Net realized gain on sale of business	—			(23.0		)	—			—			(23.0		)
Deferred income tax expense (benefit)	—			12.5			(0.5		)	0.3			12.3
Dividends received from subsidiaries	62			—			23			(85.0		)	—
Other operating items:
Net change in loss and LAE reserves	—			52.9			—			—			52.9
Net change in unearned premiums	—			(21.1		)	—			—			(21.1		)
Net change in premiums receivable	—			(30.3		)	—			—			(30.3		)
Net change in reinsurance recoverables on paid and unpaid losses	—			24.5			—			—			24.5
Net change in other assets and liabilities	3.1			70.4			4.1			0.2			77.8
Net cash provided from operations—continuing operations	61.6			178.2			23.5			(85.0		)	178.3
Net cash used for operations—discontinued operations	—			(98.0		)	—			—			(98.0		)
Net cash provided from (used for) operations	61.6			80.2			23.5			(85.0		)	80.3
Cash flows from investing activities:
Net maturities, purchases and sales of short-term investments	(1.5		)	13.2			55.6			—			67.3
Maturities of fixed maturity investments	—			185.3			11.3			—			196.6
Sales of fixed maturity investments	—			1,114.60			129.7			(35.7		)	1,208.60
Sales of common equity securities	—			142			—			—			142
Sales of convertible fixed maturity investments	—			39.5			—			—			39.5
Return of capital and distributions of other investments	—			13.1			—			—			13.1
Purchases of fixed maturity investments	—			(1,227.8		)	(189.7		)	35.7			(1,381.8		)
Purchases of common equity securities	—			(168.5		)	—			—			(168.5		)
Purchases of convertible fixed maturity investments	—			(12.0		)	—			—			(12.0		)
Contributions for other investments	—			(7.1		)	—			—			(7.1		)
Proceeds from sale of business	—			31.3			—			—			31.3
Net change in unsettled investment purchases and sales	—			(7.7		)	—			—			(7.7		)
Net acquisitions of property and equipment	—			(7.6		)	—			—			(7.6		)
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	—			30			—			(30.0		)	—
Net cash provided from (used for) investing activities—continuing operations	(1.5		)	138.3			6.9			(30.0		)	113.7
Net cash provided from investing activities—discontinued operations	—			—			—			—			—
Net cash provided from (used for) investing activities	(1.5		)	138.3			6.9			(30.0		)	113.7
Cash flows from financing activities:
Cash dividends paid to common shareholders	(60.1		)	—			—			—			(60.1		)
Cash dividends paid to parent	—			(85.0		)	—			85			—
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	—			—			(30.0		)	30			—
Payments on capital lease obligation	—			(4.0		)	—			—			(4.0		)
Net cash used for financing activities—continuing operations	(60.1		)	(89.0		)	(30.0		)	115			(64.1		)
Net cash used for financing activities—discontinued operations	—			—			—			—			—
Net cash used for financing activities	(60.1		)	(89.0		)	(30.0		)	115			(64.1		)
Net increase in cash during period	—			129.5			0.4			—			129.9
Cash balance at beginning of period	—			43.9			—			—			43.9
Cash balance at end of period	$	—		$	173.4		$	0.4		$	—		$	173.8
_______________________________________________________________________________
(1) "The Company (guarantor)" column's undistributed earnings from subsidiaries and equity in net income including noncontrolling interests for the nine months ended September 30, 2013, have been revised from the prior year's presentation to appropriately reflect the earnings for that period. These items were reduced by $3.7 million and offset in the "Consolidating adjustments" column.

Nature_of_Operations_and_Summa1

Nature of Operations and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Recently Adopted Changes in Accounting Principles	'
	Recently Adopted Changes in Accounting Principles
	Unrecognized Tax Benefits
	Effective January 1, 2014, OneBeacon prospectively adopted ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists (ASC 740). The new ASU requires balance sheet presentation of an unrecognized tax benefit as a reduction of a deferred tax asset for a net operating loss ("NOL") carryforward or tax credit carryforward rather than as a liability. The exception is in circumstances where a carryforward is not available to settle the additional taxes that might arise upon disallowance of the tax position under the tax law of the applicable jurisdiction. Prior to the issuance of ASU 2013-11, the guidance for unrecognized tax benefits under ASC 740 did not provide explicit guidance on whether an entity should present an unrecognized tax benefit as a liability or as a reduction of NOL carryforwards or other tax credits. In circumstances where an NOL carryforward is not available to offset settlement of any additional taxes arising from a disallowed tax position, the unrecognized tax benefit should be presented as a liability. This adoption did not have any impact on the Company's financial statements.
	Recently Issued Accounting Pronouncements
	Qualified Affordable Housing Projects
	In January 2014 the FASB issued ASU 2014-01, Accounting for Investments in Qualified Affordable Housing Projects ("QAHP"), which permits companies to make an accounting policy election to account for investments in a QAHP using the proportional amortization method, if certain conditions are met. Under this method, the initial cost of the investment is amortized in proportion to the tax credits and other tax benefits received, with the net investment performance recognized in the income statement as a component of income tax expense. The new guidance also requires certain new disclosures for all QAHP investments. ASU 2014-01 is effective for annual and interim reporting periods beginning after December 15, 2014 and may be applied retrospectively to all periods presented upon adoption. The Company currently holds an investment in a QAHP that is accounted for under the equity method and does not expect the adoption to have a material impact on its financial position, results of operations, or cash flows.
	Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity
	In April 2014, the FASB issued ASU 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, to reduce diversity in practice for reporting discontinued operations. Under the previous guidance, any component of an entity that was a reportable segment, an operating segment, a reporting unit, a subsidiary, or an asset group was eligible for discontinued operations presentation. The revised guidance only allows disposals of components of an entity that represent a strategic shift (e.g., disposal of a major geographical area, a major line of business, a major equity method investment, or other major parts of an entity) and that have a major effect on a reporting entity’s operations and financial results to be reported as discontinued operations. The revised guidance also requires expanded disclosure in the financial statements for discontinued operations as well as for disposals of significant components of an entity that do not qualify for discontinued operations presentation. The updated guidance is effective for transactions entered into after December 15, 2014.
	Revenue from Contracts with Customers
	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. 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. ASU 2014-09 is effective for annual and interim reporting periods beginning after December 15, 2016.
	Share-Based Compensation Awards
	In June 2014, the FASB issued 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. The new guidance is intended to eliminate diversity in practice for employee share-based awards containing performance targets that could be achieved after the requisite service period. Some reporting entities account for performance targets that can be achieved after the requisite service period as performance conditions that affect the vesting of the award while other reporting entities treat those performance targets as nonvesting conditions that affect the grant-date fair value of the award. The updated 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 should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the periods for which service has been rendered. 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. The new guidance is effective for annual and interim reporting periods beginning after December 15, 2015.

Unpaid_Loss_and_Loss_Adjustmen1

Unpaid Loss and Loss Adjustment Expense (LAE) Reserves (Tables)	9 Months Ended
	Sep. 30, 2014
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 and nine months ended September 30, 2014 and 2013:
		Three months ended						Nine months ended
		September 30,						September 30,
		2014			2013			2014			2013
		($ in millions)
	Gross beginning balance	$	1,125.40		$	1,027.80		$	1,054.30		$	1,000.00
	Less beginning reinsurance recoverables on unpaid losses	(92.0		)	(81.8		)	(80.2		)	(107.3		)
	Net beginning loss and LAE reserves	1,033.40			946			974.1			892.7
	Loss and LAE incurred relating to:
	Current year losses	177.9			164			506.4			473.8
	Prior year losses	7.3			3.8			14.3			(0.1		)
	Total incurred loss and LAE from continuing operations	185.2			167.8			520.7			473.7
	Loss and LAE paid relating to:
	Current year losses	(55.7		)	(54.0		)	(115.3		)	(115.0		)
	Prior year losses	(104.7		)	(87.1		)	(321.3		)	(278.7		)
	Total loss and LAE payments from continuing operations	(160.4		)	(141.1		)	(436.6		)	(393.7		)
	Net ending loss and LAE reserves	1,058.20			972.7			1,058.20			972.7
	Plus ending reinsurance recoverables on unpaid losses	101.4			80.2			101.4			80.2
	Gross ending loss and LAE reserves	$	1,159.60		$	1,052.90		$	1,159.60		$	1,052.90

Reinsurance_Tables

Reinsurance (Tables)	9 Months Ended
	Sep. 30, 2014
Reinsurance Disclosures [Abstract]	'
Reinsurers	'
	The following table summarizes Standard & Poor's Financial Services, LLC ("Standard & Poor's") ratings for OneBeacon's reinsurers for its continuing insurance operations, excluding industry pools and associations, based upon reinsurance recoverables amounts on paid and unpaid losses and LAE:
			Balance at		% of total
			30-Sep-14
	Standard & Poor's Rating(1):		($ in millions)
	AA		$	46.5	41	%
	A		64.1		56	%
	BBB+, Not Rated and Other		3.5		3	%
	Total reinsurance recoverables		$	114.1	100	%
	_______________________________________________________________________________
	(1) Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB+" (Adequate).
	($ in millions)		Balance at		% of total		A.M. Best
			30-Sep-14				Rating(1)
	National Indemnity Company ("NICO") and General Reinsurance Corporation(2)		$	1,127.40	71	%	A++
	Hanover Insurance Company		30.7		2	%	A
	Munich Reinsurance America		28.3		2	%	A++
	Tokio Marine and Nichido Fire(3)		25.4		2	%	A+
	Everest Reinsurance		14		1	%	A+
	_______________________________________________________________________________
	-1	A.M. Best ratings as detailed above are: “A++” (Superior, which is the highest of sixteen financial strength ratings), “A+” (Superior, which is the second highest of sixteen financial strength ratings), and “A” (Excellent, which is the third highest of sixteen financial strength ratings).
	-2	Includes $198.3 million of Third Party Recoverables, which NICO would pay under the terms of the NICO Cover if they are unable to collect from third party reinsurers.
	-3	Excludes $21.8 million of reinsurance recoverables from the various reinsurers that are guaranteed by Tokio Marine and Nichido Fire.

Investment_Securities_Tables

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 2014
Schedule of Investments [Abstract]	'
Net investment income, pre-tax	'
	Net investment income for the three and nine months ended September 30, 2014, and 2013 consisted of the following:
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
			($ in millions)
	Fixed maturity investments		$	10.5		$	10.4		$	31.4		$	30.7
	Common equity securities		1.5			1.5			5.2			4.4
	Convertible fixed maturity investments		0.5			0.2			0.6			0.9
	Other investments		(0.3		)	(0.4		)	—			—
	Gross investment income		12.2			11.7			37.2			36
	Less investment expenses		(1.8		)	(1.6		)	(5.1		)	(5.1		)
	Net investment income		$	10.4		$	10.1		$	32.1		$	30.9
Net realized and unrealized investment gains (losses), pre-tax	'
	The composition of net realized investment gains consisted of the following:
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
			($ in millions)
	Fixed maturity investments		$	2.2		$	(5.0	)	$	4.6		$	2.8
	Short-term investments		—			—			—			0.1
	Common equity securities		13.5			2.7			25.4			20.6
	Convertible fixed maturity investments		1			—			3.3			(0.4		)
	Other investments		2.6			(1.9		)	2.6			2.8
	Net realized investment gains		$	19.3		$	(4.2	)	$	35.9		$	25.9
Net unrealized investment gains (losses)	'
	The net changes in fair value for the three and nine months ended September 30, 2014, and 2013 are as follows:
			Three months ended September 30, 2014									Nine months ended September 30, 2014
			Changes in net			Changes in net			Total net changes			Changes in net			Changes in net			Total net changes
			unrealized investment			foreign currency			in fair value reflected			unrealized investment			foreign currency			in fair value reflected
			gains (losses)(1)			translation			in revenues(1)			gains(1)			translation			in revenues(1)
						gains (losses)(1)									gains (losses)(1)
			($ in millions)
	Fixed maturity investments		$	(8.0	)	$	—		$	(8.0	)	$	4		$	—		$	4
	Short-term investments		—			(0.1		)	(0.1		)	—			(0.1		)	(0.1		)
	Common equity securities		(21.5		)	(0.4		)	(21.9		)	(11.8		)	(0.4		)	(12.2		)
	Convertible fixed maturity investments		(1.8		)	—			(1.8		)	(4.1		)	—			(4.1		)
	Other investments		(3.5		)	—			(3.5		)	1.3			—			1.3
	Net change in fair value		$	(34.8	)	$	(0.5	)	$	(35.3	)	$	(10.6	)	$	(0.5	)	$	(11.1	)
			Three months ended September 30, 2013									Nine months ended September 30, 2013
			Changes in net			Changes in net			Total net changes			Changes in net			Changes in net			Total net changes
			unrealized investment			foreign currency			in fair value reflected			unrealized investment			foreign currency			in fair value reflected
			gains (losses)(1)			translation			in revenues(1)			gains (1)			translation			in revenues(1)
						gains (losses)(1)									gains (losses)(1)
			($ in millions)
	Fixed maturity investments		$	0.5		$	0.1		$	0.6		$	(33.7	)	$	—		$	(33.7	)
	Short-term investments		—			—			—			—			—			—
	Common equity securities		15.8			0.1			15.9			21.3			0.1			21.4
	Convertible fixed maturity investments		1			—			1			(0.6		)	—			(0.6		)
	Other investments		3.7			—			3.7			6.9			—			6.9
	Net change in fair value		$	21		$	0.2		$	21.2		$	(6.1	)	$	0.1		$	(6.0	)
	_______________________________________________________________________________
	-1	Includes pre-tax changes in net deferred gains and losses on sales of investments between OneBeacon and entities under White Mountains' common control of $(0.7) million and $(0.8) million for the three and nine months ended September 30, 2013, respectively, with no such changes in net deferred gains and losses for the three and nine months ended September 30, 2014.
Gross unrealized investment gains or losses	'
	The components of OneBeacon's ending net unrealized investment gains and losses, excluding the impact of net unrealized foreign currency translation gains and losses, on its investment portfolio as of September 30, 2014 and December 31, 2013 were as follows:
			September 30,			December 31,
			2014			2013
			($ in millions)
	Investment securities:
	Gross unrealized investment gains		$	125		$	133.7
	Gross unrealized investment losses		(11.2		)	(9.3		)
	Total net unrealized investment gains, pre-tax		113.8			124.4
	Income taxes		(31.3		)	(33.8		)
	Total net unrealized investment gains, after tax		$	82.5		$	90.6
Investment holdings, fixed maturity investments	'
	The cost or amortized cost, gross unrealized pre-tax investment gains and losses, net unrealized foreign currency translation gains (losses) and carrying values of fixed maturity investments as of September 30, 2014 and December 31, 2013 were as follows:
			September 30, 2014(1)
			Cost or			Gross			Gross			Net unrealized foreign			Carrying
			amortized			unrealized			unrealized			currency			value
			cost			gains			losses			translation gains (losses)
			($ in millions)
	U.S. Government and agency obligations		$	73.3		$	—		$	—		$	—		$	73.3
	Debt securities issued by corporations		799.9			13.7			(1.0		)	—			812.6
	Municipal obligations		65.1			1.2			(0.2		)	—			66.1
	Mortgage-backed and asset-backed securities		882.2			1.4			(2.0		)	—			881.6
	Foreign government obligations		1			0.3			—			—			1.3
	Preferred stocks		78.3			6.4			—			—			84.7
	Total fixed maturity investments		$	1,899.80		$	23		$	(3.2	)	$	—		$	1,919.60
			December 31, 2013(1)
			Cost or			Gross			Gross			Net unrealized foreign			Carrying
			amortized			unrealized			unrealized			currency			value
			cost			gains			losses			translation gains (losses)
			($ in millions)
	U.S. Government and agency obligations		$	131		$	0.2		$	(0.1	)	$	—		$	131.1
	Debt securities issued by corporations		741.7			14.1			(1.3		)	—			754.5
	Municipal obligations		16.9			—			(0.4		)	—			16.5
	Mortgage-backed and asset-backed securities		951.5			1.2			(3.2		)	—			949.5
	Foreign government obligations		2			0.3			—			—			2.3
	Preferred stocks		78.3			5			—			—			83.3
	Total fixed maturity investments		$	1,921.40		$	20.8		$	(5.0	)	$	—		$	1,937.20
	_______________________________________________________________________________
	-1	Includes carrying value of $203.9 million and $236.3 million of fixed maturity investments reclassified to assets held for sale in the consolidated balance sheets as part of the Runoff Transaction as of September 30, 2014 and December 31, 2013, respectively.
Investment holdings, common equity securities, convertible fixed maturity investments and other investments	'
	The cost or amortized cost, gross unrealized pre-tax investment gains and losses, net unrealized foreign currency translation gains (losses) and carrying values of common equity securities, convertible fixed maturity investments and other investments as of September 30, 2014 and December 31, 2013 were as follows:
			30-Sep-14
			Cost or			Gross			Gross			Net unrealized foreign			Carrying
			amortized			unrealized			unrealized			currency			value
			cost			gains			losses			translation gains (losses)
			($ in millions)
	Common equity securities		$	258.1		$	61.3		$	(3.7	)	$	(0.2	)	$	315.5
	Convertible fixed maturity investments		17.2			0.6			(0.5		)	—			17.3
	Other investments		98.5			40.1			(3.8		)	—			134.8
	Total common equity securities, convertible fixed maturity investments and other investments		$	373.8		$	102		$	(8.0	)	$	(0.2	)	$	467.6
			31-Dec-13
			Cost or			Gross			Gross			Net unrealized foreign			Carrying
			amortized			unrealized			unrealized			currency			value
			cost			gains			losses			translation gains (losses)
			($ in millions)
	Common equity securities		$	267.2		$	70.4		$	(0.9	)	$	0.2		$	336.9
	Convertible fixed maturity investments		26.3			4.5			(0.3		)	—			30.5
	Other investments		104.7			38			(3.1		)	—			139.6
	Total common equity securities, convertible fixed maturity investments and other investments		$	398.2		$	112.9		$	(4.3	)	$	0.2		$	507
Fair value measurements by level, investment securities	'
	The following tables summarize the Company's fair value measurements for investments at September 30, 2014 and December 31, 2013 by level:
			Fair value at			Level 1			Level 2			Level 3
			September 30, 2014(2)
			($ in millions)
	Fixed maturity investments:
	U.S. Government and agency obligations		$	73.3		$	73.3		$	—		$	—
	Debt securities issued by corporations:
	Consumer		279			—			279			—
	Financial		141			—			141			—
	Industrial		104.4			—			104.4			—
	Communications		87.2			—			87.2			—
	Basic materials		68			—			64.9			3.1
	Energy		67.1			—			67.1			—
	Utilities		36.9			—			36.9			—
	Technology		29			—			29			—
	Debt securities issued by corporations		812.6			—			809.5			3.1
	Mortgage-backed and asset-backed securities		881.6			—			870.7			10.9
	Preferred stocks		84.7			—			13.2			71.5
	Municipal obligations		66.1			—			66.1			—
	Foreign government obligations		1.3			0.6			0.7			—
	Fixed maturity investments		1,919.60			73.9			1,760.20			85.5
	Short-term investments		238.4			238.1			0.3			—
	Common equity securities:
	Consumer		114.4			114.4			—			—
	Financials		71.2			70.8			—			0.4
	Energy		27.1			27.1			—			—
	Basic Materials		19.1			19.1			—			—
	Utilities		10.3			10.3			—			—
	Other		73.4			73.4			—			—
	Common equity securities		315.5			315.1			—			0.4
	Convertible fixed maturity investments		17.3			—			17.3			—
	Other investments(1)		116.4			—			—			116.4
	Total(1)		$	2,607.20		$	627.1		$	1,777.80		$	202.3
	_______________________________________________________________________________
	-1	Excludes the carrying value of $18.4 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of September 30, 2014.
	-2	Fair value includes $203.9 million of fixed maturity investments reclassified to assets held for sale in the September 30, 2014 consolidated balance sheets as part of the Runoff Transaction.
			Fair value at			Level 1			Level 2			Level 3
			December 31, 2013(2)
			($ in millions)
	Fixed maturity investments:
	U.S. Government and agency obligations		$	131.1		$	131.1		$	—		$	—
	Debt securities issued by corporations:
	Consumer		239.6			—			239.6			—
	Financial		145.5			—			145.5			—
	Industrial		106			—			106			—
	Communications		91.5			—			91.5			—
	Basic materials		64.4			—			64.4			—
	Energy		40.5			—			40.5			—
	Utilities		38			—			38			—
	Technology		29			—			29			—
	Debt securities issued by corporations		754.5			—			754.5			—
	Mortgage-backed and asset-backed securities		949.5			—			938.6			10.9
	Preferred stocks		83.3			—			12.3			71
	Municipal obligations		16.5			—			16.5			—
	Foreign government obligations		2.3			1.6			0.7			—
	Fixed maturity investments		1,937.20			132.7			1,722.60			81.9
	Short-term investments		157			155.9			1.1			—
	Common equity securities:
	Consumer		122.6			122.6			—			—
	Financials		83.3			83.2			—			0.1
	Energy		34.7			34.7			—			—
	Basic Materials		20.3			20.3			—			—
	Utilities		8.3			8.3			—			—
Other		67.7			67.7			—			—
Common equity securities		336.9			336.8			—			0.1
Convertible fixed maturity investments		30.5			—			30.5			—
Other investments(1)		119.9			—			—			119.9
Total(1)		$	2,581.50		$	625.4		$	1,754.20		$	201.9
_______________________________________________________________________________
-1	Excludes the carrying value of $19.7 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of December 31, 2013.
-2	Fair value includes $236.3 million of fixed maturity investments reclassified to assets held for sale in the December 31, 2013 consolidated balance sheets as part of the Runoff Transaction.
Debt securities, credit ratings	'
	The following table summarizes the ratings of OneBeacon's corporate debt securities as of September 30, 2014 and December 31, 2013:
			September 30,			December 31,
			2014			2013
			($ in millions)
	AA		$	55.2		$	51.2
	A		327.1			357.9
	BBB		426.2			345.4
	BB		—			—
	Not rated		4.1			—
	Debt securities issued by corporations(1)		$	812.6		$	754.5
	_______________________________________________________________________________
	(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 changes in Level 1 fair value measurements for the three and nine months ended September 30, 2014 are as follows:
			Fixed			Common			Convertible			Other			Total(1)
			maturity			equity			fixed			investments
			investments			securities			maturity
									investments
			($ in millions)
	Balance at January 1, 2014		$	132.7		$	336.8		$	—		$	—		$	469.5
	Amortization/accretion		—			—			—			—			—
	Net realized and unrealized gains (losses)		0.1			8.5			—			—			8.6
	Purchases		114.6			26			—			—			140.6
	Sales		(35.7		)	(24.3		)	—			—			(60.0		)
	Transfers in		—			—			—			—			—
	Transfers out		—			—			—			—			—
	Balance at March 31, 2014		211.7			347			—			—			558.7
	Amortization/accretion		—			—			—			—			—
	Net realized and unrealized gains (losses)		1.3			12.8			—			—			14.1
	Purchases		256.6			22.6			—			—			279.2
	Sales		(309.4		)	(23.3		)	—			—			(332.7		)
	Transfers in		—			—			—			—			—
	Transfers out		—			—			—			—			—
	Balance at June 30, 2014		160.2			359.1			—			—			519.3
	Amortization/accretion		—			—			—			—			—
	Net realized and unrealized gains (losses)		—			(8.5		)	—			—			(8.5		)
	Purchases		113.7			14.4			—			—			128.1
	Sales		(200.0		)	(49.9		)	—			—			(249.9		)
	Transfers in		—			—			—			—			—
	Transfers out		—			—			—			—			—
	Balance at September 30, 2014		$	73.9		$	315.1		$	—		$	—		$	389
	_______________________________________________________________________________
	-1	Excludes short-term investments which are deemed to have a Level 1 designation.
	The changes in Level 2 fair value measurements for the three and nine months ended September 30, 2014 are as follows:
			Fixed			Common			Convertible			Other			Total(1)
			maturity			equity			fixed			investments
			investments			securities			maturity
									investments
			($ in millions)
	Balance at January 1, 2014		$	1,722.60		$	—		$	30.5		$	—		$	1,753.10
	Amortization/accretion		(2.6		)	—			(0.1		)	—			(2.7		)
	Net realized and unrealized gains (losses)		5			—			1.9			—			6.9
	Purchases		344			—			3.8			—			347.8
	Sales		(404.6		)	—			(6.8		)	—			(411.4		)
	Transfers in		—			—			—			—			—
	Transfer out		—			—			—			—			—
	Balance at March 31, 2014		1,664.40			—			29.3			—			1,693.70
	Amortization/accretion		(2.7		)	—			(0.1		)	—			(2.8		)
	Net realized and unrealized gains (losses)		7.2			—			(1.7		)	—			5.5
	Purchases		345.1			—			4.7			—			349.8
	Sales		(285.8		)	—			(6.3		)	—			(292.1		)
	Transfers in		7.5			—			—			—			7.5
	Transfer out		—			—			—			—			—
	Balance at June 30, 2014		1,735.70			—			25.9			—			1,761.60
	Amortization/accretion		(2.8		)	—			(0.1		)	—			(2.9		)
	Net realized and unrealized gains (losses)		(6.8		)	—			(0.9		)	—			(7.7		)
	Purchases		423.5			—			2.8			—			426.3
	Sales		(423.7		)	—			(10.4		)	—			(434.1		)
	Transfers in		34.3			—			—			—			34.3
	Transfer out		—			—			—			—			—
	Balance at September 30, 2014		$	1,760.20		$	—		$	17.3		$	—		$	1,777.50
	_______________________________________________________________________________
	(1)	Excludes short-term investments which are deemed to have a Level 2 designation.
	The changes in Level 3 fair value measurements for the three and nine months ended September 30, 2014 and 2013 are as follows:
			Fixed			Common			Convertible			Other			Total(1)
			maturity			equity			fixed			investments(1)
investments			securities			maturity
						investments
		($ in millions)
Balance at January 1, 2014		$	81.9		$	0.1		$	—		$	119.9		$	201.9
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		0.3			—			—			3.1			3.4
Purchases		7.5			—			—			2.3			9.8
Sales		—			—			—			(1.6		)	(1.6		)
Transfers in		—			—			—			—			—
Transfers out		—			—			—			—			—
Balance at March 31, 2014		$	89.7		$	0.1		$	—		$	123.7		$	213.5
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		0.3			0.4			—			1.7			2.4
Purchases		34.2			—			—			1			35.2
Sales		—			—			—			(1.5		)	(1.5		)
Transfers in		—			—			—			—			—
Transfers out		(7.5		)	—			—			—			(7.5		)
Balance at June 30, 2014		116.7			0.5			—			124.9			242.1
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		1.1			(0.1		)	—			(0.9		)	0.1
Purchases		2			—			—			0.3			2.3
Sales		—			—			—			(7.9		)	(7.9		)
Transfers in		—			—			—			—			—
Transfers out		(34.3		)	—			—			—			(34.3		)
Balance at September 30, 2014		$	85.5		$	0.4		$	—		$	116.4		$	202.3
_______________________________________________________________________________
(1)	Excludes the carrying value of $18.4 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of September 30, 2014.
		Fixed			Common			Convertible			Other			Total(1)
		maturity			equity			fixed			investments(1)
		investments			securities			maturity
								investments
		($ in millions)
Balance at January 1, 2013		$	76.1		$	0.1		$	—		$	122.7		$	198.9
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		0.1			—			—			3.7			3.8
Purchases		1.8			—			—			1.8			3.6
Sales		—			—			—			(4.5		)	(4.5		)
Transfers in		—			—			—			—			—
Transfers out		—			—			—			—			—
Balance at March 31, 2013		78			0.1			—			123.7			201.8
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		(0.2		)	—			—			4.2			4
Purchases		14			—			—			3.4			17.4
Sales		—			—			—			(6.7		)	(6.7		)
Transfers in		—			—			—			—			—
Transfers out		(1.8		)	—			—			—			(1.8		)
Balance at June 30, 2013		90			0.1			—			124.6			214.7
Amortization/accretion		—			—			—			—			—
Net realized and unrealized gains (losses)		(1.8		)	—			—			1.9			0.1
Purchases		—			—			—			1.3			1.3
Sales		(0.5		)	—			—			(1.8		)	(2.3		)
Transfers in		61.3			—			—			—			61.3
Transfers out		(13.8		)	—			—			—			(13.8		)
Balance at September 30, 2013		$	135.2		$	0.1		$	—		$	126		$	261.3
_______________________________________________________________________________
-1	Excludes the carrying value of $20.2 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of September 30, 2013.
Fair value, significant unobservable inputs	'
	The following summarizes significant unobservable inputs used in estimating the fair value of investment securities classified within Level 3, other than hedge funds and private equity funds, at September 30, 2014. The fair value of investments in hedge funds and private equity funds, which are classified within Level 3, are estimated using the net asset value of the funds.
	Description(1)		Fair Value			Rating(2)		Valuation Technique	Unobservable Inputs		Range
	Preferred stock		$	71.5		NR		Discounted cash flow	Discount yield		6.60%
	Other asset-backed securities		$	10.9		AA+		Broker pricing	Broker quote		N/A
	Debt securities issued by corporations		$	3.1		NR		Exchange transaction(3)	N/A		N/A
	_________________________________________________________________________
	(1)	As of September 30, 2014, each asset type consists of one security.
	(2)	Credit ratings are assigned based on the following hierarchy: 1) Standard & Poor's and 2) Moody's
	(3)	Derived from the exchange of a convertible fixed maturity investment, where the valuation of the debt security issued by a corporation represents a portion of the total exchange price after taking into consideration the cash and value of the common equity security that was also received in the exchange transaction.
Net unrealized gains or losses for Level 3 investments	'
	The following table summarizes the change in net unrealized gains or losses for assets designated as Level 3 for the three and nine months ended September 30, 2014 and 2013:
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
			($ in millions)
	Fixed maturity investments		$	1.1		$	(1.8	)	$	1.7		$	(1.8	)
	Short-term investments		—			—			—			—
	Common equity securities		—			—			—			—
	Convertible fixed maturity investments		—			—			—			—
	Other investments		(3.5		)	3.7			1.3			6.9
	Total		$	(2.4	)	$	1.9		$	3		$	5.1
Mortgage-backed and asset-backed securities	'
	The following table summarizes the carrying value of OneBeacon's mortgage-backed and asset-backed securities as of September 30, 2014 and December 31, 2013:
			September 30, 2014									December 31, 2013
			Fair Value			Level 2			Level 3			Fair Value			Level 2			Level 3
			($ in millions)
	Mortgage-backed securities:
	Agency:
	GNMA		$	267.7		$	267.7		$	—		$	321.8		$	321.8		$	—
	FNMA		20.6			20.6			—			36.5			36.5			—
	FHLMC		1.1			1.1			—			24.3			24.3			—
	Total agency(1)		289.4			289.4			—			382.6			382.6			—
	Non-agency:
	Residential		94.7			94.7			—			51.5			51.5			—
	Commercial		109.2			109.2			—			155			155			—
	Total Non-agency		203.9			203.9			—			206.5			206.5			—
	Total mortgage-backed securities		493.3			493.3			—			589.1			589.1			—
	Other asset-backed securities:
	Credit card receivables		182.4			171.5			10.9			124.2			113.3			10.9
	Vehicle receivables		162.1			162.1			—			189.3			189.3			—
	Other		43.8			43.8			—			46.9			46.9			—
	Total other asset-backed securities		388.3			377.4			10.9			360.4			349.5			10.9
	Total mortgage-backed and asset-backed securities		$	881.6		$	870.7		$	10.9		$	949.5		$	938.6		$	10.9
	_______________________________________________________________________________
	-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 September 30, 2014 are as follows:
			Fair Value			Security Issuance Year
						2004			2005			2006			2007			2008			2009		2010		2011		2012		2013		2014
			($ in millions)
	Total non-agency RMBS		$	94.7		$	5.4		$	4.4		$	5.3		$	—		$	5.7		$	—	$	4.1	$	15.5	$	4	$	17.2	$	33.1
	Total non-agency CMBS		109.2			—			—			—			0.7			—			—		6.7		—		6.3		38.9		56.6
	Total non-agency		$	203.9		$	5.4		$	4.4		$	5.3		$	0.7		$	5.7		$	—	$	10.8	$	15.5	$	10.3	$	56.1	$	89.7
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 September 30, 2014:
			Fair Value			Super Senior(1)			Senior(2)			Subordinate(3)
			($ in millions)
	Prime		$	90.6		$	38.7		$	51.9		$	—
	Non-prime		4.1			—			4.1			—
	Total non-agency RMBS		$	94.7		$	38.7		$	56		$	—
	_______________________________________________________________________________
	-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 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 September 30, 2014:
			Fair Value			Super Senior(1)			Senior(2)			Subordinate(3)
			($ in millions)
	Fixed rate CMBS		$	62.3		$	24.5		$	20.3		$	17.5
	Floating rate CMBS		46.9			0.7			—			46.2
	Total non-agency CMBS		$	109.2		$	25.2		$	20.3		$	63.7
	_______________________________________________________________________________
	-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 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 securities.
Other investments	'
	The following table summarizes investments in hedge funds and private equity funds at September 30, 2014 and December 31, 2013:
			30-Sep-14						31-Dec-13
			Fair			Unfunded			Fair			Unfunded
			Value			Commitments			Value			Commitments
			($ in millions)
	Hedge funds
	Long/short equity		$	36.6		$	—		$	39.1		$	—
	Long/short credit and distressed		8.5			—			8.1			—
	Long/short equity activist		2.4			—			2.1			—
	Long bank loan		0.1			—			0.1			—
	Total hedge funds		47.6			—			49.4			—
	Private equity funds
	Energy infrastructure and services		26.3			4.8			26			5.9
	Multi-sector		15.1			2.2			14.5			2.5
	Private equity secondaries		6.3			2.1			6.4			2.1
	Healthcare		2.9			1.4			2.8			1.4
	Insurance		2.2			0.1			2.3			0.1
	Real estate		1.6			0.1			3.9			0.1
	Distressed residential real estate		—			—			0.2			—
	Total private equity funds		54.4			10.7			56.1			12.1
	Total hedge funds and private equity funds(1)		$	102		$	10.7		$	105.5		$	12.1
	_______________________________________________________________________________
	-1	Excluded from the above table as of September 30, 2014 and December 31, 2013 are other investments, which include an investment in a community reinvestment vehicle of $14.2 million and $14.4 million, respectively, and an investment in a tax advantaged federal affordable housing development fund of $18.4 million and $19.7 million, respectively. Additionally, other investments include trust certificates issued upon dissolution of a private equity fund of $0.2 million as of September 30, 2014, with no such investment held as of December 31, 2013.
Fair value of hedge funds subject to restrictions on redemption frequency and advance notice period requirements for investments in active hedge funds	'
	The following summarizes the September 30, 2014 fair value of hedge funds subject to restrictions on redemption frequency and advance notice period requirements for investments in active hedge funds:
			Hedge Funds—Active Funds
			30 - 59 days			60 - 89 days			90 - 119 days			120+ days			Total
			notice			notice			notice			notice
			($ in millions)
	Redemption frequency
	Monthly		$	1.8		$	—		$	—		$	—		$	1.8
	Quarterly		28.8			8.5			6			—			43.3
	Annual		—			—			2.4			0.1			2.5
	Total hedge funds		$	30.6		$	8.5		$	8.4		$	0.1		$	47.6
Fair Value of private equity funds subject to lock-up periods	'
	At September 30, 2014, investments in private equity funds were subject to lock-up periods as follows:
			1 - 3 years			3 - 5 years			5 - 10 years			>10 years			Total
			($ in millions)
	Private Equity Funds—expected lock-up period remaining		$	9.6		$	18.2		$	26.6		$	—		$	54.4

Debt_Tables

Debt (Tables)	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Schedule of debt outstanding	'
	OneBeacon's debt outstanding as of September 30, 2014 and December 31, 2013 consisted of the following:
		September 30,			December 31,
		2014			2013
		($ in millions)
	Senior unsecured notes, at face value	$	275		$	275
	Unamortized original issue discount	(0.3		)	(0.3		)
	Senior unsecured notes, carrying value	$	274.7		$	274.7

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Financial information for OneBeacon's segments	'
	Financial information for OneBeacon's reportable segments is as follows:
			Insurance Operations						Investing,
									Financing
									and
			Specialty			Specialty			Corporate			Consolidated
			Products			Industries
			($ in millions)
	Three months ended September 30, 2014
	Earned premiums		$	151.7		$	153.7		$	—		$	305.4
	Loss and loss adjustment expense		(98.2		)	(87.0		)	—			(185.2		)
	Policy acquisition expenses		(26.6		)	(28.0		)	—			(54.6		)
	Other underwriting expenses		(23.2		)	(28.0		)	—			(51.2		)
	Total underwriting income		3.7			10.7			—			14.4
	Net investment income		—			—			10.4			10.4
	Net realized and change in unrealized investment gains		—			—			(16.0		)	(16.0		)
	Net other revenues		(0.3		)	0.5			1.1			1.3
	General and administrative expenses		—			(0.8		)	(1.6		)	(2.4		)
	Interest expense		—			—			(3.2		)	(3.2		)
	Pre-tax income (loss) from continuing operations		$	3.4		$	10.4		$	(9.3	)	$	4.5
	Three months ended September 30, 2013
	Earned premiums		$	132.2		$	146.7		$	—		$	278.9
	Loss and loss adjustment expense		(84.2		)	(83.6		)	—			(167.8		)
	Policy acquisition expenses		(27.4		)	(26.2		)	—			(53.6		)
	Other underwriting expenses		(21.2		)	(25.6		)	—			(46.8		)
	Total underwriting income (loss)		(0.6		)	11.3			—			10.7
	Net investment income		—			—			10.1			10.1
	Net realized and change in unrealized investment gains		—			—			17			17
	Net other revenues		—			0.6			4.9			5.5
	General and administrative expenses		—			(1.1		)	(3.0		)	(4.1		)
	Interest expense		—			—			(3.3		)	(3.3		)
	Pre-tax income (loss) from continuing operations		$	(0.6	)	$	10.8		$	25.7		$	35.9
			Insurance Operations						Investing,
									Financing
									and
			Specialty			Specialty			Corporate			Consolidated
			Products			Industries
			($ in millions)
	Nine months ended September 30, 2014
	Earned premiums		$	433		$	439.8		$	—		$	872.8
	Loss and loss adjustment expense		(277.5		)	(243.2		)	—			(520.7		)
	Policy acquisition expenses		(71.4		)	(79.5		)	—			(150.9		)
	Other underwriting expenses		(68.1		)	(84.2		)	—			(152.3		)
	Total underwriting income		16			32.9			—			48.9
	Net investment income		—			—			32.1			32.1
	Net realized and change in unrealized investment gains		—			—			24.8			24.8
	Net other revenues		(0.1		)	0.8			2.6			3.3
	General and administrative expenses		0.1			(1.8		)	(7.6		)	(9.3		)
	Interest expense		—			—			(9.7		)	(9.7		)
	Pre-tax income from continuing operations		$	16		$	31.9		$	42.2		$	90.1
	Nine months ended September 30, 2013
	Earned premiums		$	426.9		$	419.3		$	—		$	846.2
	Loss and loss adjustment expense		(240.6		)	(233.1		)	—			(473.7		)
	Policy acquisition expenses		(84.3		)	(76.6		)	—			(160.9		)
	Other underwriting expenses		(72.5		)	(78.2		)	—			(150.7		)
	Total underwriting income		29.5			31.4			—			60.9
	Net investment income		—			—			30.9			30.9
	Net realized and change in unrealized investment gains		—			—			19.9			19.9
	Net other revenues		0.3			0.9			28.9			30.1
	General and administrative expenses		(0.1		)	(2.3		)	(8.6		)	(11.0		)
	Interest expense		—			—			(9.8		)	(9.8		)
	Pre-tax income from continuing operations		$	29.7		$	30		$	61.3		$	121
Schedule of selected balance sheet of the segments	'
			Insurance Operations						Investing,
									Financing
									and
			Specialty			Specialty			Corporate(1)			Consolidated
			Products			Industries
			($ in millions)
	30-Sep-14
	Assets
	Total investment securities		$	—		$	—		$	2,421.70		$	2,421.70
	Reinsurance recoverables		85.5			28.6			—			114.1
	Deferred acquisition costs		66			55.8			—			121.8
	Liabilities
	Unpaid loss and loss adjustment expense reserves		678.2			481.4			—			1,159.60
	Unearned premiums		332.4			292.8			—			625.2
	Debt		—			—			274.7			274.7
	31-Dec-13
	Assets
	Total investment securities		$	—		$	—		$	2,364.90		$	2,364.90
	Reinsurance recoverables		60.2			29.7			—			89.9
	Deferred acquisition costs		53.6			50.1			—			103.7
	Liabilities
	Unpaid loss and loss adjustment expense reserves		607.8			446.5			—			1,054.30
	Unearned premiums		275.4			269.5			—			544.9
	Debt		—			—			274.7			274.7
	_______________________________________________________________________________
	(1)As described in Note 2—"Acquisitions and Dispositions," balances related to the the Runoff Business are presented as held for sale. Total investment securities excludes $203.9 million and $236.3 million of fixed maturity investments reclassified to assets held for sale as of September 30, 2014 and December 31, 2013, respectively.
Schedule of net written premiums, earned premiums and ratios for OneBeacon's insurance operations by segment and in total, as well as for the three major underwriting units within Specialty Insurance Operations	'
	The following tables provide net written premiums, earned premiums and underwriting ratios for OneBeacon's insurance operations by reportable segment and in total, for the three and nine months ended September 30, 2014, and 2013:
			Three months ended September 30, 2014									Three months ended September 30, 2013
			Insurance Operations									Insurance Operations
	($ in millions)		Specialty			Specialty			Consolidated			Specialty			Specialty			Consolidated
			Products			Industries						Products			Industries
	Net written premiums		$	188.3		$	157.3		$	345.6		$	172		$	142.1		$	314.1
	Earned premiums		151.7			153.7			305.4			132.2			146.7			278.9
	Underwriting ratios:(1)
	Loss and LAE		64.7		%	56.7		%	60.6		%	63.7		%	56.9		%	60.1		%
	Expense		32.9			36.4			34.7			36.7			35.4			36
	Total combined ratio		97.6		%	93.1		%	95.3		%	100.4		%	92.3		%	96.1		%
			Nine months ended September 30, 2014									Nine months ended September 30, 2013
			Insurance Operations									Insurance Operations
	($ in millions)		Specialty			Specialty			Consolidated			Specialty			Specialty			Consolidated
			Products			Industries						Products			Industries
	Net written premiums		$	488.6		$	464		$	952.6		$	393.3		$	432.8		$	826.1
	Earned premiums		433			439.8			872.8			426.9			419.3			846.2
	Underwriting ratios:(1)
	Loss and LAE		64.1		%	55.3		%	59.7		%	56.4		%	55.6		%	56		%
	Expense		32.2			37.2			34.7			36.7			36.9			36.8
	Total combined ratio		96.3		%	92.5		%	94.4		%	93.1		%	92.5		%	92.8		%
	_______________________________________________________________________________
	-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)	9 Months Ended
	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]	'
Schedule of components of net periodic benefit cost (income)	'
	The components of net periodic benefit cost for the three and nine months ended September 30, 2014 and 2013 were as follows:
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
			($ in millions)
	Service cost		$	0.2		$	0.2		$	0.5		$	0.6
	Interest cost		1.2			1.1			3.5			3.2
	Expected return on plan assets		(2.2		)	(1.8		)	(6.4		)	(5.4		)
	Amortization of unrecognized loss		0.1			0.2			0.3			0.7
	Net periodic pension income before special termination benefits		(0.7		)	(0.3		)	(2.1		)	(0.9		)
	Special termination benefits expense(1)		—			—			0.3			0.3
	Total net periodic benefit income		$	(0.7	)	$	(0.3	)	$	(1.8	)	$	(0.6	)
	_______________________________________________________________________________
	-1	Special termination benefits represent additional payments made from the Qualified Plan to certain vested participants when their employment was terminated due to a reduction in force.

Employee_ShareBased_Incentive_1

Employee Share-Based Incentive Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Summary of performance share activity	'
	The following summarizes performance share activity for the three and nine months ended September 30, 2014 and 2013:
			Three months ended September 30,
			2014					2013
			Target OB		Accrued			Target OB		Accrued
			Performance		expense			Performance		expense
			Shares					Shares
			outstanding					outstanding
			($ in millions)
	Beginning of period		512,938		$	4.4		489,867		$	2.4
	Payments and deferrals		—		—			—		—
	New awards		—		—			—		—
	Forfeitures and net change in assumed forfeitures		—		—			—		—
	Expense recognized		—		1.1			—		0.1
	End of period		512,938		$	5.5		489,867		$	2.5
			Nine months ended September 30,
			2014					2013
			Target OB		Accrued			Target OB		Accrued
			Performance		expense			Performance		expense
			Shares					Shares
			outstanding					outstanding
			($ in millions)
	Beginning of period		493,421		$	4		563,190		$	1.2
	Payments and deferrals(1)		(142,138	)	(1.0		)	(238,658	)	—
	New awards		165,800		—			179,000		—
	Forfeitures and net change in assumed forfeitures		(4,145	)	—			(13,665	)	(0.1		)
	Expense recognized		—		2.5			—		1.4
	End of period		512,938		$	5.5		489,867		$	2.5
	_______________________________________________________________________________
	(1)	Performance share payments in 2014 for the 2011-2013 performance cycle were based upon a performance factor of 37.1%. No payments were made in 2013 for the 2010-2012 performance cycle as the performance factor was zero.
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 September 30, 2014 for each performance cycle:
			Target OB		Accrued
			Performance		expense
			Shares
			outstanding
			($ in millions)
	Performance cycle:
	2012 - 2014		181,290		$	2.8
	2013 - 2015		179,000		2.2
	2014 - 2016		165,800		0.6
	Subtotal		526,090		5.6
	Assumed forfeitures		(13,152	)	(0.1		)
	Total at September 30, 2014		512,938		$	5.5
Summary of restricted shares activity	'
	The following summarizes restricted shares activity for the three and nine months ended September 30, 2014 and 2013:
			Three months ended September 30,
			2014					2013
			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
			($ in millions)
	Beginning of period		612,500		$	4.9		918,000		$	8
	New awards		—		—			—		—
	Forfeitures		—		—			(3,000	)	—
	Vested		—		—			—		—
	Expense recognized		—		(0.7		)	—		(0.7		)
	End of period		612,500		$	4.2		915,000		$	7.3
			Nine months ended September 30,
			2014					2013
			Restricted Shares		Unamortized Issue Date Fair Value			Restricted Shares		Unamortized Issue Date Fair Value
			($ in millions)
	Beginning of period		915,000		$	6.5		927,000		$	9.6
	New awards		—		—			—		—
	Forfeitures		(2,500	)	—			(3,000	)	—
	Vested		(300,000	)	—			(9,000	)	—
	Expense recognized		—		(2.3		)	—		(2.3		)
	End of period		612,500		$	4.2		915,000		$	7.3

Earnings_per_Share_Tables

Earnings per Share (Tables)	9 Months Ended
	Sep. 30, 2014
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 and nine months ended September 30, 2014 and 2013:
			Three months ended						Nine months ended
			September 30,						September 30,
			2014			2013			2014			2013
	Earnings attributable to OneBeacon's common shareholders—basic and diluted (in millions):
	Net income from continuing operations attributable to OneBeacon's common shareholders		$	6.2		$	38.8		$	79.1		$	104.3
	Allocation of income for participating unvested restricted common shares		(0.1		)	(0.4		)	(0.6		)	(1.0		)
	Dividends paid on participating restricted common shares		(0.2		)	(0.2		)	(0.4		)	(0.6		)
	Total allocation to restricted common shares		(0.3		)	(0.6		)	(1.0		)	(1.6		)
	Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts		$	5.9		$	38.2		$	78.1		$	102.7
	Undistributed (overdistributed) net earnings (in millions):
	Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts		$	5.9		$	38.2		$	78.1		$	102.7
	Dividends paid, net of restricted common share amounts		(19.8		)	(19.8		)	(59.6		)	(59.5		)
	Total undistributed (overdistributed) net earnings, net of restricted common share amounts		$	(13.9	)	$	18.4		$	18.5		$	43.2
	Earnings per share denominator—basic and diluted (in millions):
	Total weighted average common shares outstanding		95.3			95.4			95.3			95.4
	Weighted average unvested restricted common shares(1)		(0.6		)	(0.9		)	(0.7		)	(0.9		)
	Basic and diluted earnings per share denominator		94.7			94.5			94.6			94.5
	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		$	0.06		$	0.41		$	0.83		$	1.09
	Dividends declared and paid		(0.21		)	(0.21		)	(0.63		)	(0.63		)
	Undistributed (overdistributed) earnings		$	(0.15	)	$	0.2		$	0.2		$	0.46
	_______________________________________________________________________________
	(1)	Restricted shares outstanding vest in equal installments upon a stated date or upon the occurrence of a specified event.

Discontinued_Operations_Tables

Discontinued Operations (Tables)	9 Months Ended
	Sep. 30, 2014
Discontinued Operations and Disposal Groups [Abstract]	'
Schedule of discontinued operations balance sheet statement of operations and other disclosures	'
	The following table outlines the computation of loss per share for discontinued operations attributable to OneBeacon's common shareholders for the three and nine months ended September 30, 2014 and 2013:
			Three months ended							Nine months ended
			September 30,							September 30,
			2014			2013				2014			2013
	Income (loss) attributable to OneBeacon's common shareholders—basic and diluted (in millions):
	Net income (loss) from discontinued operations attributable to OneBeacon's common shareholders		$	(7.3	)	$	0.3			$	(8.4	)	$	0.3
	Allocation of income (loss) for participating unvested restricted common shares		0.1			—				0.1			—
	Net income (loss) from discontinued operations attributable to OneBeacon's common shareholders, net of restricted common share amounts		$	(7.2	)	$	0.3			$	(8.3	)	$	0.3
	Income (loss) per share denominator—basic and diluted (in millions):
	Total weighted average common shares outstanding		95.3			95.4				95.3			95.4
	Weighted average unvested restricted common shares(1)		(0.6		)	(0.9		)		(0.7		)	(0.9		)
	Basic and diluted income (loss) per share denominator		94.7			94.5				94.6			94.5
	Loss per share attributable to OneBeacon's common shareholders—basic and diluted (in dollars):
	Loss from discontinued operations attributable to OneBeacon's common shareholders per share		$	(0.07	)	$	—			$	(0.09	)	$	—
	_______________________________________________________________________________
	(1)	Restricted shares outstanding vest in equal installments upon a stated date or upon the occurrence of a specified event.
	As of September 30, 2014 and December 31, 2013, the Runoff Transaction met the criteria for held for sale accounting. As a result, the assets and liabilities associated with the businesses being sold, after effecting the various steps contemplated by the Stock Purchase Agreement, are presented separately as single line items in the asset and liability sections of the consolidated balance sheets as of September 30, 2014 and December 31, 2013. The following summarizes the major categories of assets and liabilities associated with the business classified as held for sale:
			September 30,			December 31,
			2014			2013
			($ in millions)
	Assets:
	Investments		$	203.9		$	236.3
	Premiums receivable		11.6			9.1
	Reinsurance recoverables on unpaid losses(1)		1,458.40			1,604.70
	Reinsurance recoverables on paid losses		7.4			10.7
	Net deferred tax asset		2.5			3.3
	Other assets		15.4			16
	Total assets held for sale		$	1,699.20		$	1,880.10
	Liabilities:
	Unpaid loss and loss adjustment expense reserves(1)		$	1,600.90		$	1,793.10
	Unearned premiums		—			0.2
	Ceded reinsurance payable		12.1			12.3
	Other liabilities(2)		86.2			74.5
	Total liabilities held for sale		$	1,699.20		$	1,880.10
	_______________________________________________________________________________
	-1	The September 30, 2014 and December 31, 2013 balances include the remaining purchase accounting fair value adjustments of $127.0 million and $136.9 million, respectively, relating to the OneBeacon Acquisition. As of September 30, 2014 and December 31, 2013, reinsurance recoverables on unpaid losses, gross of purchase accounting adjustments, were $1,585.4 million and $1,741.6 million, respectively, and unpaid loss and LAE reserves, gross of purchase accounting adjustments, were $1,727.9 million and $1,930.0 million for each period.
	-2	Other liabilities as of September 30, 2014 and December 31, 2013 include the accrual related to the pre-tax loss on sale of the Runoff Business of $80.5 million and $69.0 million, respectively.
	The following summarizes the results of operations, including related income taxes associated with the business classified as discontinued operations:
			Three months ended							Nine months ended
			September 30,							September 30,
			2014			2013				2014			2013
			($ in millions)
	Net written premiums		$	0.1		$	1			$	(0.1	)	$	0.4
	Revenues
	Earned premiums		$	0.3		$	1.1			$	0.1		$	0.7
	Other revenue		—			—				—			7.8
	Total revenues		0.3			1.1				0.1			8.5
	Expenses
	Loss and loss adjustment expenses		—			0.1				(0.7		)	7.6
	Policy acquisition expenses		0.1			0.1				0.1			0.1
	Other underwriting expenses		0.8			0.4				2.2			0.3
	Total expenses		0.9			0.6				1.6			8
	Pre-tax income (loss)		(0.6		)	0.5				(1.5		)	0.5
	Income tax (expense) benefit		0.3			(0.2		)		0.6			(0.2		)
	Income (loss) from discontinued operations, net of tax		(0.3		)	0.3				(0.9		)	0.3
	Loss from sale of discontinued operations, net of tax		(7.0		)	—				(7.5		)	—
	Net income (loss) from discontinued operations, net of tax		$	(7.3	)	$	0.3			$	(8.4	)	$	0.3
Reinsurers	'
	The following table summarizes Standard & Poor's Financial Services, LLC ("Standard & Poor's") ratings for OneBeacon's reinsurers for its continuing insurance operations, excluding industry pools and associations, based upon reinsurance recoverables amounts on paid and unpaid losses and LAE:
			Balance at			% of total
			30-Sep-14
	Standard & Poor's Rating(1):		($ in millions)
	AA		$	46.5		41	%
	A		64.1			56	%
	BBB+, Not Rated and Other		3.5			3	%
	Total reinsurance recoverables		$	114.1		100	%
	_______________________________________________________________________________
	(1) Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB+" (Adequate).
	($ in millions)		Balance at			% of total			A.M. Best
			30-Sep-14						Rating(1)
	National Indemnity Company ("NICO") and General Reinsurance Corporation(2)		$	1,127.40		71	%		A++
	Hanover Insurance Company		30.7			2	%		A
	Munich Reinsurance America		28.3			2	%		A++
	Tokio Marine and Nichido Fire(3)		25.4			2	%		A+
	Everest Reinsurance		14			1	%		A+
	_______________________________________________________________________________
	-1	A.M. Best ratings as detailed above are: “A++” (Superior, which is the highest of sixteen financial strength ratings), “A+” (Superior, which is the second highest of sixteen financial strength ratings), and “A” (Excellent, which is the third highest of sixteen financial strength ratings).
	-2	Includes $198.3 million of Third Party Recoverables, which NICO would pay under the terms of the NICO Cover if they are unable to collect from third party reinsurers.
	-3	Excludes $21.8 million of reinsurance recoverables from the various reinsurers that are guaranteed by Tokio Marine and Nichido Fire.

Consolidating_Financial_Inform1

Consolidating Financial Information (Tables)	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Consolidating Balance Sheet	'
	The following tables present OneBeacon's consolidating balance sheets as of September 30, 2014 and December 31, 2013 and statements of operations and comprehensive income for the three and nine months ended September 30, 2014 and 2013 and cash flows for the nine months ended September 30, 2014 and 2013. 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	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
	as of September 30, 2014	(in millions)
	Assets
	Investment Securities:
	Fixed maturity investments, at fair value	$	—		$	1,738.40		$	2.9		$	(25.6	)	$	1,715.70
	Short-term investments, at amortized cost (which approximates fair value)	10.3			224.8			3.3			—			238.4
	Common equity securities, at fair value	—			315.5			—			—			315.5
	Convertible fixed maturity investments, at fair value	—			17.3			—			—			17.3
	Other investments	—			134.8			—			—			134.8
	Total investment securities	10.3			2,430.80			6.2			(25.6		)	2,421.70
	Cash	—			187.5			—			—			187.5
	Reinsurance recoverables	—			114.1			—			—			114.1
	Premiums receivable	—			283.7			—			—			283.7
	Deferred acquisition costs	—			121.8			—						121.8
	Net deferred tax asset	—			86.4			—			0.3			86.7
	Investment income accrued	—			9.8			—			(0.5		)	9.3
	Accounts receivable on unsettled investment sales	—			22			—			—			22
	Investments in subsidiaries	1,106.90			—			1,079.40			(2,186.3		)	—
	Other assets	0.5			304.3			2.4			—			307.2
	Assets held for sale	—			1,699.20			—			—			1,699.20
	Total assets	$	1,117.70		$	5,259.60		$	1,088.00		$	(2,212.1	)	$	5,253.20
	Liabilities
	Unpaid loss and loss adjustment expense reserves	$	—		$	1,159.60		$	—		$	—		$	1,159.60
	Unearned premiums	—			625.2			—			—			625.2
	Debt	—			—			299.7			(25.0		)	274.7
	Accounts payable on unsettled investment purchases	—			23.5			—			—			23.5
	Other liabilities	2.1			340			10.5			(0.5		)	352.1
	Liabilities held for sale	—			1,699.20			—			—			1,699.20
	Total liabilities	2.1			3,847.50			310.2			(25.5		)	4,134.30
	OneBeacon's common shareholders' equity and noncontrolling interests
	Total OneBeacon's common shareholders' equity	1,115.60			1,408.80			777.8			(2,186.6		)	1,115.60
	Total noncontrolling interests	—			3.3			—			—			3.3
	Total OneBeacon's common shareholders' equity and noncontrolling interests	1,115.60			1,412.10			777.8			(2,186.6		)	1,118.90
	Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	$	1,117.70		$	5,259.60		$	1,088.00		$	(2,212.1	)	$	5,253.20
	Consolidating Balance Sheet	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
	as of December 31, 2013	(in millions)
	Assets
	Investment Securities:
	Fixed maturity investments, at fair value	$	—		$	1,725.40		$	—		$	(24.5	)	$	1,700.90
	Short-term investments, at amortized cost (which approximates fair value)	13			140			4			—			157
	Common equity securities, at fair value	—			336.9			—			—			336.9
	Convertible fixed maturity investments, at fair value	—			30.5			—			—			30.5
	Other investments	—			139.6			—			—			139.6
	Total investment securities	13			2,372.40			4			(24.5		)	2,364.90
	Cash	—			166.6			1.5			—			168.1
	Reinsurance recoverables	—			89.9			—			—			89.9
	Premiums receivable	—			228.2			—			—			228.2
	Deferred acquisition costs	—			103.7			—			—			103.7
	Net deferred tax asset	—			93.1			(2.4		)	(0.1		)	90.6
	Investment income accrued	—			10.3			—			(0.2		)	10.1
	Accounts receivable on unsettled investment sales	—			3.3			—			—			3.3
	Investments in subsidiaries	1,092.00			—			1,034.90			(2,126.9		)	—
	Other assets	(0.8		)	272.4			1.1			—			272.7
	Assets held for sale	—			1,880.10			—			—			1,880.10
	Total assets	$	1,104.20		$	5,220.00		$	1,039.10		$	(2,151.7	)	$	5,211.60
	Liabilities
	Unpaid loss and loss adjustment expense reserves	$	—		$	1,054.30		$	—		$	—		$	1,054.30
	Unearned premiums	—			544.9			—			—			544.9
	Debt	—			—			299.7			(25.0		)	274.7
	Accounts payable on unsettled investment purchases	—			11.6			—			—			11.6
	Other liabilities	(0.1		)	335			3.9			(0.2		)	338.6
	Liabilities held for sale	—			1,880.10			—			—			1,880.10
Total liabilities	(0.1		)	3,825.90			303.6			(25.2		)	4,104.20
OneBeacon's common shareholders' equity and noncontrolling interests
Total OneBeacon's common shareholders' equity	1,104.30			1,391.00			735.5			(2,126.5		)	1,104.30
Total noncontrolling interests	—			3.1			—			—			3.1
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,104.30			1,394.10			735.5			(2,126.5		)	1,107.40
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	$	1,104.20		$	5,220.00		$	1,039.10		$	(2,151.7	)	$	5,211.60
Consolidating Statement of Operations and Comprehensive (Loss) Income	'
	Consolidating Statement of Operations and Comprehensive Income (Loss)	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
	Three months ended September 30, 2014	(in millions)
	Revenues
	Earned premiums	$	—		$	305.4		$	—		$	—		$	305.4
	Net investment income	—			10.7			—			(0.3		)	10.4
	Net realized and change in unrealized investment gains	—			(16.3		)	—			0.3			(16.0		)
	Net other revenues	—			1.3			—			—			1.3
	Total revenues	—			301.1			—			—			301.1
	Expenses
	Loss and loss adjustment expenses	—			185.2			—			—			185.2
	Policy acquisition expenses	—			54.6			—			—			54.6
	Other underwriting expenses	—			51.2			—			—			51.2
	General and administrative expenses	0.5			1.9			—			—			2.4
	Interest expense	—			—			3.5			(0.3		)	3.2
	Total expenses	0.5			292.9			3.5			(0.3		)	296.6
	Pre-tax income (loss) from continuing operations	(0.5		)	8.2			(3.5		)	0.3			4.5
	Income tax benefit	—			1.6			0.3			(0.2		)	1.7
	Net income (loss) from continuing operations	(0.5		)	9.8			(3.2		)	0.1			6.2
	Loss from discontinued operations, net of tax	—			(0.3		)	—			—			(0.3		)
	Loss from sale of discontinued operations, net of tax	—			(7.0		)	—			—			(7.0		)
	Income (loss) before equity in earnings of unconsolidated affiliates	(0.5		)	2.5			(3.2		)	0.1			(1.1		)
	Equity in earnings of subsidiaries, net of tax	(0.6		)	—			(3.6		)	4.2			—
	Net income (loss) including noncontrolling interests	(1.1		)	2.5			(6.8		)	4.3			(1.1		)
	Less: Net income attributable to noncontrolling interests	—			—			—			—			—
	Net income (loss) attributable to OneBeacon's common shareholders	(1.1		)	2.5			(6.8		)	4.3			(1.1		)
	Other comprehensive income, net of tax	—			—			—			—			—
	Comprehensive income (loss) attributable to OneBeacon's common shareholders	$	(1.1	)	$	2.5		$	(6.8	)	$	4.3		$	(1.1	)
	Consolidating Statement of Operations and Comprehensive Income	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
	Three months ended September 30, 2013	(in millions)
	Revenues
	Earned premiums	$	—		$	278.9		$	—		$	—		$	278.9
	Net investment income	—			10.2			0.2			(0.3		)	10.1
	Net realized and change in unrealized investment gains	—			17.2			(0.4		)	0.2			17
	Net other revenues	—			5.5			—			—			5.5
	Total revenues	—			311.8			(0.2		)	(0.1		)	311.5
	Expenses
	Loss and loss adjustment expenses	—			167.8			—			—			167.8
	Policy acquisition expenses	—			53.6			—			—			53.6
	Other underwriting expenses	—			46.8			—			—			46.8
	General and administrative expenses	1.7			2.2			0.2			—			4.1
	Interest expense	—			—			3.5			(0.2		)	3.3
	Total expenses	1.7			270.4			3.7			(0.2		)	275.6
	Pre-tax income (loss) from continuing operations	(1.7		)	41.4			(3.9		)	0.1			35.9
	Income tax benefit	—			0.5			2.5			(0.1		)	2.9
	Net income (loss) from continuing operations	(1.7		)	41.9			(1.4		)	—			38.8
	Income from discontinued operations, net of tax	—			0.3			—			—			0.3
	Net income (loss) before equity in earnings of unconsolidated affiliates	(1.7		)	42.2			(1.4		)	—			39.1
	Equity in earnings of subsidiaries, net of tax(1)	40.8			—			34			(74.8		)	—
	Net income including noncontrolling interests(1)	39.1			42.2			32.6			(74.8		)	39.1
	Less: Net income attributable to noncontrolling interests	—			—			—			—			—
	Net income attributable to OneBeacon's common shareholders(1)	39.1			42.2			32.6			(74.8		)	39.1
	Other comprehensive income, net of tax	0.2			—			0.2			(0.2		)	0.2
	Comprehensive income attributable to OneBeacon's common shareholders(1)	$	39.3		$	42.2		$	32.8		$	(75.0	)	$	39.3
	_______________________________________________________________________________
	(1) "The Company (guarantor)" column's equity in earnings of subsidiaries, net of tax, for the three months ended September 30, 2013, has been revised from the prior year's presentation to appropriately reflect the earnings for that period. This item was reduced by $3.7 million and offset in the "Consolidating adjustments" column.
Consolidating Statement of Cash Flows	'
	Consolidating Statement of Cash Flows	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
	Nine months ended September 30, 2014	($ in millions)
	Cash flows from operations:
	Net income including noncontrolling interests	$	70.7		$	83.5		$	42.1		$	(124.7	)	$	71.6
	Charges (credits) to reconcile net income to cash flows provided from (used for) operations:
	Undistributed earnings from subsidiaries	(74.7		)	—			(49.3		)	124			—
	Net loss from discontinued operations	—			0.9			—			—			0.9
	Net loss from sale of discontinued operations	—			7.5			—			—			7.5
	Net realized and change in unrealized investment gains	—			(25.8		)	—			1			(24.8		)
	Deferred income tax expense	—			9			—			(0.4		)	8.6
	Dividends received from subsidiaries	60.4			—			5			(65.4		)	—
	Other operating items:
	Net change in loss and LAE reserves	—			105.3			—			—			105.3
	Net change in unearned premiums	—			80.3			—			—			80.3
	Net change in premiums receivable	—			(55.5		)	—			—			(55.5		)
	Net change in reinsurance recoverables on paid and unpaid losses	—			(24.2		)	—			—			(24.2		)
	Net change in other assets and liabilities	2.7			(28.4		)	2.8			0.1			(22.8		)
	Net cash provided from operations—continuing operations	59.1			152.6			0.6			(65.4		)	146.9
	Net cash used for operations—discontinued operations	—			(44.8		)	—			—			(44.8		)
	Net cash provided from (used for) operations	59.1			107.8			0.6			(65.4		)	102.1
	Cash flows from investing activities:
	Net maturities, purchases and sales of short-term investments	2.7			(84.9		)	0.7			—			(81.5		)
	Maturities of fixed maturity investments	—			202.6			—			—			202.6
	Sales of fixed maturity investments	—			1,450.00			9.6			—			1,459.60
	Sales of common equity securities	—			97.5			—			—			97.5
	Sales of convertible fixed maturity investments	—			20.6			—			—			20.6
	Return of capital and distributions of other investments	—			11.1			—			—			11.1
	Purchases of fixed maturity investments	—			(1,628.8		)	(12.4		)	—			(1,641.2		)
	Purchases of common equity securities	—			(63.0		)	—			—			(63.0		)
	Purchases of convertible fixed maturity investments	—			(11.3		)	—			—			(11.3		)
	Contributions for other investments	—			(3.6		)	—			—			(3.6		)
	Net change in unsettled investment purchases and sales	—			(6.8		)	—			—			(6.8		)
	Net acquisitions of property and equipment	—			(0.9		)	—			—			(0.9		)
	Net cash provided from (used for) investing activities—continuing operations	2.7			(17.5		)	(2.1		)	—			(16.9		)
	Net cash provided from investing activities—discontinued operations	—			—			—			—			—
	Net cash provided from (used for) investing activities	2.7			(17.5		)	(2.1		)	—			(16.9		)
	Cash flows from financing activities:
	Cash dividends paid to common shareholders	(60.0		)	—			—			—			(60.0		)
	Cash dividends paid to parent	—			(65.4		)	—			65.4			—
	Repurchases and retirements of common stock	(1.8		)	—			—			—			(1.8		)
	Payments on capital lease obligation	—			(4.0		)	—			—			(4.0		)
	Net cash used for financing activities—continuing operations	(61.8		)	(69.4		)	—			65.4			(65.8		)
	Net cash used for financing activities—discontinued operations	—			—			—			—			—
	Net cash used for financing activities	(61.8		)	(69.4		)	—			65.4			(65.8		)
	Net increase (decrease) in cash during period	—			20.9			(1.5		)	—			19.4
	Cash balance at beginning of period	—			166.6			1.5			—			168.1
	Cash balance at end of period	$	—		$	187.5		$	—		$	—		$	187.5
	Consolidating Statement of Cash Flows	The Company (guarantor)			Non-guarantor subsidiaries			OBH (issuer)			Consolidating adjustments			Consolidated
	Nine months ended September 30, 2013	($ in millions)
	Cash flows from operations:
	Net income including noncontrolling interests(1)	$	104.6		$	112.3		$	87.7		$	(199.2	)	$	105.4
	Charges (credits) to reconcile net income to cash flows provided from (used for) operations:
	Undistributed earnings from subsidiaries(1)	(108.1		)	—			(91.6		)	199.7			—
	Net income from discontinued operations	—			(0.3		)	—			—			(0.3		)
	Net realized and change in unrealized investment gains	—			(19.7		)	0.8			(1.0		)	(19.9		)
	Net realized gain on sale of business	—			(23.0		)	—			—			(23.0		)
	Deferred income tax expense (benefit)	—			12.5			(0.5		)	0.3			12.3
	Dividends received from subsidiaries	62			—			23			(85.0		)	—
	Other operating items:
	Net change in loss and LAE reserves	—			52.9			—			—			52.9
	Net change in unearned premiums	—			(21.1		)	—			—			(21.1		)
	Net change in premiums receivable	—			(30.3		)	—			—			(30.3		)
	Net change in reinsurance recoverables on paid and unpaid losses	—			24.5			—			—			24.5
Net change in other assets and liabilities	3.1			70.4			4.1			0.2			77.8
Net cash provided from operations—continuing operations	61.6			178.2			23.5			(85.0		)	178.3
Net cash used for operations—discontinued operations	—			(98.0		)	—			—			(98.0		)
Net cash provided from (used for) operations	61.6			80.2			23.5			(85.0		)	80.3
Cash flows from investing activities:
Net maturities, purchases and sales of short-term investments	(1.5		)	13.2			55.6			—			67.3
Maturities of fixed maturity investments	—			185.3			11.3			—			196.6
Sales of fixed maturity investments	—			1,114.60			129.7			(35.7		)	1,208.60
Sales of common equity securities	—			142			—			—			142
Sales of convertible fixed maturity investments	—			39.5			—			—			39.5
Return of capital and distributions of other investments	—			13.1			—			—			13.1
Purchases of fixed maturity investments	—			(1,227.8		)	(189.7		)	35.7			(1,381.8		)
Purchases of common equity securities	—			(168.5		)	—			—			(168.5		)
Purchases of convertible fixed maturity investments	—			(12.0		)	—			—			(12.0		)
Contributions for other investments	—			(7.1		)	—			—			(7.1		)
Proceeds from sale of business	—			31.3			—			—			31.3
Net change in unsettled investment purchases and sales	—			(7.7		)	—			—			(7.7		)
Net acquisitions of property and equipment	—			(7.6		)	—			—			(7.6		)
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	—			30			—			(30.0		)	—
Net cash provided from (used for) investing activities—continuing operations	(1.5		)	138.3			6.9			(30.0		)	113.7
Net cash provided from investing activities—discontinued operations	—			—			—			—			—
Net cash provided from (used for) investing activities	(1.5		)	138.3			6.9			(30.0		)	113.7
Cash flows from financing activities:
Cash dividends paid to common shareholders	(60.1		)	—			—			—			(60.1		)
Cash dividends paid to parent	—			(85.0		)	—			85			—
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	—			—			(30.0		)	30			—
Payments on capital lease obligation	—			(4.0		)	—			—			(4.0		)
Net cash used for financing activities—continuing operations	(60.1		)	(89.0		)	(30.0		)	115			(64.1		)
Net cash used for financing activities—discontinued operations	—			—			—			—			—
Net cash used for financing activities	(60.1		)	(89.0		)	(30.0		)	115			(64.1		)
Net increase in cash during period	—			129.5			0.4			—			129.9
Cash balance at beginning of period	—			43.9			—			—			43.9
Cash balance at end of period	$	—		$	173.4		$	0.4		$	—		$	173.8
_______________________________________________________________________________
(1) "The Company (guarantor)" column's undistributed earnings from subsidiaries and equity in net income including noncontrolling interests for the nine months ended September 30, 2013, have been revised from the prior year's presentation to appropriately reflect the earnings for that period. These items were reduced by $3.7 million and offset in the "Consolidating adjustments" column.

Nature_of_Operations_and_Summa2

Nature of Operations and Summary of Significant Accounting Policies (Details)	9 Months Ended
	Sep. 30, 2014
	segment
Basis of presentation	'
Participation percentage in quota share reinsurance agreements	100.00%
Number of underwriting segments	14
White Mountains Insurance Group Ltd	'
Basis of presentation	'
Ownership interest (as a percent)	75.30%
Specialty Products	'
Basis of presentation	'
Number of underwriting segments	8
Specialty Industries	'
Basis of presentation	'
Number of underwriting segments	6

Acqusitions_and_Dispositions_D

Acqusitions and Dispositions (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Mar. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Jun. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Dec. 31, 2013

Essentia Insurance Company

Essentia Insurance Company

Essentia Insurance Company

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Runoff [Member]

Runoff [Member]

Segment, Discontinued Operations

Segment, Discontinued Operations

Dispositions

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Change In Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations

'

'

'

'

'

'

'

'

$6.70

'

'

'

'

'

Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations

'

'

'

'

'

'

'

80.9

'

'

80.9

'

'

'

Pre-tax income (loss)

'

'

'

'

'

'

'

'

'

'

'

'

80.5

69

Gain on sale of discontinued operation, pre-tax

'

'

'

'

'

23

'

'

'

'

-11.5

'

'

'

Net loss from sale of discontinued operations

-7

0

-7.5

0

'

15

'

-7

'

0

-7.5

0

'

'

Premiums Earned, Net

$305.40

$278.90

$872.80

$846.20

$15.80

'

$85.20

$0.30

'

$1.10

$0.10

$0.70

'

'

Unpaid_Loss_and_Loss_Adjustmen2

Unpaid Loss and Loss Adjustment Expense (LAE) Reserves (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]	'	'	'	'	'	'	'	'
Gross beginning balance	$1,125.40	$1,027.80	$1,054.30	$1,000	'	'	'	'
Less beginning reinsurance recoverables on unpaid losses	-92	-81.8	-80.2	-107.3	'	'	'	'
Loss and LAE incurred relating to Current year losses	177.9	164	506.4	473.8	'	'	'	'
Loss and LAE incurred relating to prior year losses	7.3	3.8	14.3	-0.1	'	'	'	'
Total incurred loss and LAE from continuing operations	185.2	167.8	520.7	473.7	'	'	'	'
Loss and LAE paid relating to Current year losses	-55.7	-54	-115.3	-115	'	'	'	'
Loss and LAE paid relating to Prior year losses	-104.7	-87.1	-321.3	-278.7	'	'	'	'
Total loss and LAE payments from continuing operations	-160.4	-141.1	-436.6	-393.7	'	'	'	'
Net ending loss and LAE reserves	1,058.20	972.7	1,058.20	972.7	1,033.40	974.1	946	892.7
Plus ending reinsurance recoverables on unpaid losses	-101.4	-80.2	-101.4	-80.2	'	'	'	'
Gross ending balance	$1,159.60	$1,052.90	$1,159.60	$1,052.90	'	'	'	'

Reinsurance_Details

Reinsurance (Details) (USD $)

Sep. 30, 2014

Jun. 30, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Dec. 31, 2012

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

1-May-14

1-May-14

Sep. 30, 2014

Mar. 31, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Property Catastrophe Reinsurance [Member]

Property Catastrophe Reinsurance [Member]

Property Catastrophe Reinsurance [Member]

Property Per Risk Reinsurance Program [Member]

Property Per Risk Reinsurance Program [Member]

MPCI Portfolio [Member]

Crop-Hail Portfolio [Member]

Crop-Hail Portfolio [Member]

Layer Three [Member]

Standard & Poor's, AA Rating [Member]

Standard & Poor's, A Rating [Member]

Standard & Poor's, BBB+ Rating [Member]

Minimum [Member]

Maximum

Minimum [Member]

Maximum

Property Catastrophe Reinsurance [Member]

Maximum

Reinsurance Retention Policy [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reinsurance Retention Policy, Amount Retained

'

'

'

'

'

'

$20,000,000

'

'

'

'

'

'

'

'

'

'

'

Reinsurance Retention Policy, Excess Retention, Amount Reinsured

'

'

'

'

'

'

'

1

110,000,000

10,000,000

5,000,000

'

'

'

130,000,000

'

'

'

Coverage in Excess of Retained Amount

'

'

'

'

'

'

'

'

'

'

'

48.50%

'

80.00%

'

'

'

'

Retained Losses

'

'

'

'

'

'

'

'

'

'

'

101.50%

100.00%

'

'

'

'

'

Reinsurance recoverables on paid losses

12,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reinsurance recoverable on unpaid losses

101,400,000

92,000,000

80,200,000

80,200,000

81,800,000

107,300,000

'

'

'

'

'

'

'

'

'

'

'

'

Reinsurance recoverables

$114,100,000

[1]

'

$89,900,000

'

'

'

'

'

'

'

'

'

'

'

'

$46,500,000

[1]

$64,100,000

[1]

$3,500,000

[1]

Percentage of total paid and unpaid reinsurance recoverables

100.00%

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

41.00%

[1]

56.00%

[1]

3.00%

[1]

[1]

Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB+" (Adequate).

Investment_Securities_Net_inve

Investment Securities (Net investment income) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Gross investment income	$12.20	$11.70	$37.20	$36
Less investment expenses	-1.8	-1.6	-5.1	-5.1
Net investment income	10.4	10.1	32.1	30.9
Fixed maturity investments	'	'	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Gross investment income	10.5	10.4	31.4	30.7
Common equity securities	'	'	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Gross investment income	1.5	1.5	5.2	4.4
Convertible fixed maturity investments	'	'	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Gross investment income	0.5	0.2	0.6	0.9
Other investments	'	'	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Gross investment income	($0.30)	($0.40)	$0	$0

Investment_Securities_Net_real

Investment Securities (Net realized investment gains (losses)) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Net realized investment gains	$19.30	($4.20)	$35.90	$25.90
Fixed maturity investments	'	'	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Net realized investment gains	2.2	-5	4.6	2.8
Short-term investments	'	'	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Net realized investment gains	0	0	0	0.1
Common equity securities	'	'	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Net realized investment gains	13.5	2.7	25.4	20.6
Convertible fixed maturity investments	'	'	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Net realized investment gains	1	0	3.3	-0.4
Other investments	'	'	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'	'	'
Net realized investment gains	$2.60	($1.90)	$2.60	$2.80

Investment_Securities_Changes_

Investment Securities (Changes in fair value) (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Total net changes in fair value reflected in revenues	'		'		'		'
Changes in net unrealized investment gains (losses)	($34.80)	[1]	$21		($10.60)	[1]	($6.10)	[1]
Changes in net foreign currency translation gains (losses)	-0.5	[1]	0.2		-0.5	[1]	0.1	[1]
Total net changes in fair value reflected in revenues	-35.3	[1]	21.2	[1]	-11.1	[1]	-6	[1]
Change in Deferred Gains (Losses)	0		-0.7		0		-0.8
Fixed maturity investments	'		'		'		'
Total net changes in fair value reflected in revenues	'		'		'		'
Changes in net unrealized investment gains (losses)	-8		0.5		4	[1]	-33.7	[1]
Changes in net foreign currency translation gains (losses)	0		0.1		0		0	[1]
Total net changes in fair value reflected in revenues	-8	[1]	0.6	[1]	4	[1]	-33.7	[1]
Short-term investments	'		'		'		'
Total net changes in fair value reflected in revenues	'		'		'		'
Changes in net unrealized investment gains (losses)	0		0		0		0
Changes in net foreign currency translation gains (losses)	-0.1		0		-0.1		0
Total net changes in fair value reflected in revenues	-0.1	[1]	0		-0.1	[1]	0	[1]
Common equity securities	'		'		'		'
Total net changes in fair value reflected in revenues	'		'		'		'
Changes in net unrealized investment gains (losses)	-21.5		15.8		-11.8	[1]	21.3	[1]
Changes in net foreign currency translation gains (losses)	-0.4		0.1		-0.4		0.1	[1]
Total net changes in fair value reflected in revenues	-21.9	[1]	15.9	[1]	-12.2	[1]	21.4	[1]
Convertible fixed maturity investments	'		'		'		'
Total net changes in fair value reflected in revenues	'		'		'		'
Changes in net unrealized investment gains (losses)	-1.8		1		-4.1	[1]	-0.6	[1]
Changes in net foreign currency translation gains (losses)	0		0		0		0	[1]
Total net changes in fair value reflected in revenues	-1.8	[1]	1	[1]	-4.1	[1]	-0.6	[1]
Other investments	'		'		'		'
Total net changes in fair value reflected in revenues	'		'		'		'
Changes in net unrealized investment gains (losses)	-3.5		3.7		1.3	[1]	6.9	[1]
Changes in net foreign currency translation gains (losses)	0		0		0		0
Total net changes in fair value reflected in revenues	($3.50)	[1]	$3.70	[1]	$1.30	[1]	$6.90	[1]
[1]	Includes pre-tax changes in net deferred gains and losses on sales of investments between OneBeacon and entities under White Mountains' common control of $(0.7) million and $(0.8) million for the three and nine months ended SeptemberB 30, 2013, respectively, with no such changes in net deferred gains and losses for the three and nine months ended September 30, 2014.

Investment_Securities_Net_unre

Investment Securities (Net unrealized investment gains and losses) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Schedule of Investments [Abstract]	'	'
Trading Securities Gross Unrealized Gain	$125	$133.70
Trading Securities Gross Unrealized Loss	-11.2	-9.3
Gross Unrealized Gains (Losses) on Trading Securities Pretax	113.8	124.4
Deferred Tax Liabilities, Unrealized Gains on Trading Securities	-31.3	-33.8
Unrealized gains (losses) on trading securities, net of tax	82.5	90.6
Accounts payable on unsettled investment purchases	23.5	11.6
Accounts receivable on unsettled investment sales	$22	$3.30

Investment_Securities_Fixed_ma

Investment Securities (Fixed maturity investment gains and losses) (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Trading Securities Gross Unrealized Gain	$125		$133.70
Gross unrealized losses	-11.2		-9.3
Carrying value	1,715.70		1,700.90
U.S. Government and agency obligations	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Cost or amortized cost	73.3		131	[1]
Trading Securities Gross Unrealized Gain	0		0.2	[1]
Gross unrealized losses	0		-0.1	[1]
Net unrealized foreign currency translation gains (losses)	0		0	[1]
Carrying value	73.3	[1]	131.1	[1]
Debt securities issued by corporations	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Cost or amortized cost	799.9		741.7	[1]
Trading Securities Gross Unrealized Gain	13.7		14.1	[1]
Gross unrealized losses	-1		-1.3	[1]
Net unrealized foreign currency translation gains (losses)	0		0	[1]
Carrying value	812.6	[1]	754.5	[1]
Municipal obligations	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Cost or amortized cost	65.1		16.9	[1]
Trading Securities Gross Unrealized Gain	1.2		0	[1]
Gross unrealized losses	-0.2		-0.4	[1]
Net unrealized foreign currency translation gains (losses)	0		0	[1]
Carrying value	66.1	[1]	16.5	[1]
Mortgage-backed and asset-backed securities	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Cost or amortized cost	882.2		951.5	[1]
Trading Securities Gross Unrealized Gain	1.4		1.2	[1]
Gross unrealized losses	-2		-3.2	[1]
Net unrealized foreign currency translation gains (losses)	0		0	[1]
Carrying value	881.6	[1]	949.5	[1]
Foreign government obligations	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Cost or amortized cost	1		2	[1]
Trading Securities Gross Unrealized Gain	0.3		0.3	[1]
Gross unrealized losses	0		0	[1]
Net unrealized foreign currency translation gains (losses)	0		0	[1]
Carrying value	1.3	[1]	2.3	[1]
Preferred stocks	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Cost or amortized cost	78.3		78.3	[1]
Trading Securities Gross Unrealized Gain	6.4		5	[1]
Gross unrealized losses	0		0	[1]
Net unrealized foreign currency translation gains (losses)	0		0	[1]
Carrying value	84.7	[1]	83.3	[1]
Total fixed maturity investments	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Cost or amortized cost	1,899.80	[1]	1,921.40	[1]
Trading Securities Gross Unrealized Gain	23	[1]	20.8	[1]
Gross unrealized losses	-3.2	[1]	-5	[1]
Net unrealized foreign currency translation gains (losses)	0	[1]	0	[1]
Carrying value	$1,919.60	[1]	$1,937.20	[1]
[1]	Includes carrying value of $203.9 million and $236.3 million of fixed maturity investments reclassified to assets held for sale in the consolidated balance sheets as part of the Runoff Transaction as of SeptemberB 30, 2014 and DecemberB 31, 2013, respectively.

Investment_Securities_Converti

Investment Securities (Convertible fixed maturity investments and other investments) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading Securities Gross Unrealized Gain	$125	$133.70
Trading Securities Gross Unrealized Loss	11.2	9.3
Carrying value	1,715.70	1,700.90
Unrestricted Collateral From Customers	76.1	63.3
Total investment securities	2,421.70	2,364.90
Common equity securities	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Cost or amortized cost	258.1	267.2
Trading Securities Gross Unrealized Gain	61.3	70.4
Trading Securities Gross Unrealized Loss	3.7	0.9
Net unrealized foreign currency translation gains (losses)	-0.2	0.2
Carrying value	315.5	336.9
Convertible fixed maturity investments	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Cost or amortized cost	17.2	26.3
Trading Securities Gross Unrealized Gain	0.6	4.5
Trading Securities Gross Unrealized Loss	0.5	0.3
Net unrealized foreign currency translation gains (losses)	0	0
Carrying value	17.3	30.5
Other investments	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Cost or amortized cost	98.5	104.7
Trading Securities Gross Unrealized Gain	40.1	38
Trading Securities Gross Unrealized Loss	3.8	3.1
Net unrealized foreign currency translation gains (losses)	0	0
Carrying value	134.8	139.6
Total common equity securities, convertible fixed maturity investments and other investments	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Cost or amortized cost	373.8	398.2
Trading Securities Gross Unrealized Gain	102	112.9
Trading Securities Gross Unrealized Loss	8	4.3
Net unrealized foreign currency translation gains (losses)	-0.2	0.2
Carrying value	467.6	507
Runoff | Segment, Discontinued Operations	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Total investment securities	$203.90	$236.30

Investment_Securities_Fair_val

Investment Securities (Fair value measurements) (Details) (USD $)

3 Months Ended

9 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Level 1

Level 1

Level 1

Level 1

Level 2

Level 2

Level 2

Level 2

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Hedge funds

Hedge funds

Private equity funds

Private equity funds

Community Reinvestment Vehicle [Member]

Community Reinvestment Vehicle [Member]

Trust Preferred Securities Subject to Mandatory Redemption [Member]

Trust Preferred Securities Subject to Mandatory Redemption [Member]

Single Fund

Single Fund

Tax Development Fund [Member]

Tax Development Fund [Member]

Tax Development Fund [Member]

Debt securities issued by corporations

Debt securities issued by corporations

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Commercial

Commercial

Commercial

Commercial

Commercial

Commercial

Preferred stocks

Preferred stocks

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Recurring basis

Segment, Discontinued Operations

Segment, Discontinued Operations

fund

fund

fund

Fair Value

Fair Value

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 2

Level 2

Level 3

Level 3

fund

fund

Level 1

Level 1

Level 1

Level 1

Level 2

Level 2

Level 2

Level 2

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 1

Level 1

Level 1

Level 1

Level 2

Level 2

Level 2

Level 2

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 1

Level 1

Level 1

Level 1

Level 2

Level 2

Level 2

Level 2

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

U.S. Government and agency obligations

U.S. Government and agency obligations

U.S. Government and agency obligations

U.S. Government and agency obligations

U.S. Government and agency obligations

U.S. Government and agency obligations

U.S. Government and agency obligations

U.S. Government and agency obligations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Debt securities issued by corporations

Municipal obligations

Municipal obligations

Municipal obligations

Municipal obligations

Municipal obligations

Municipal obligations

Municipal obligations

Municipal obligations

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Mortgage-backed and asset-backed securities

Foreign government obligations

Foreign government obligations

Foreign government obligations

Foreign government obligations

Foreign government obligations

Foreign government obligations

Foreign government obligations

Foreign government obligations

Preferred stocks

Preferred stocks

Preferred stocks

Preferred stocks

Preferred stocks

Preferred stocks

Preferred stocks

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Fixed maturity investments

Short-term investments

Short-term investments

Short-term investments

Short-term investments

Short-term investments

Short-term investments

Short-term investments

Short-term investments

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Common equity securities

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Convertible fixed maturity investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Other investments

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Consumer

Consumer

Consumer

Consumer

Consumer

Consumer

Consumer

Consumer

Industrial

Industrial

Industrial

Industrial

Industrial

Industrial

Industrial

Industrial

Financial

Financial

Financial

Financial

Financial

Financial

Financial

Financial

Communications

Communications

Communications

Communications

Communications

Communications

Communications

Communications

Energy

Energy

Energy

Energy

Energy

Energy

Energy

Energy

Basic materials

Basic materials

Basic materials

Basic materials

Basic materials

Basic materials

Basic materials

Basic materials

Utilities

Utilities

Utilities

Utilities

Utilities

Utilities

Utilities

Utilities

Technology

Technology

Technology

Technology

Technology

Technology

Technology

Technology

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Consumer

Consumer

Consumer

Consumer

Consumer

Consumer

Consumer

Consumer

Financial

Financial

Financial

Financial

Financial

Financial

Financial

Financial

Energy

Energy

Energy

Energy

Energy

Energy

Energy

Energy

Basic materials

Basic materials

Basic materials

Basic materials

Basic materials

Basic materials

Basic materials

Basic materials

Utilities

Utilities

Utilities

Utilities

Utilities

Utilities

Utilities

Utilities

Other

Other

Other

Other

Other

Other

Other

Other

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Fair Value

Fair Value

Level 1

Level 1

Level 2

Level 2

Level 3

Level 3

Schedule of Trading Securities and Other Trading Assets [Line Items]

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Maximum Percentage Differences Between Prices Provided by Pricing Services Considered Outliers

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Change in Deferred Gains (Losses)

$0

($0.70)

$0

($0.80)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total investment securities

2,421.70

'

2,421.70

'

2,364.90

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unrestricted Collateral From Customers

76.1

'

76.1

'

63.3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt securities issued by corporations

'

'

'

'

'

389

[1]

519.3

[1]

558.7

[1]

469.5

[1]

1,777.50

[2]

1,761.60

[2]

1,693.70

[2]

1,753.10

[2]

202.3

[3]

242.1

[3]

213.5

[3]

201.9

[3]

261.3

[3]

214.7

[3]

201.8

[3]

198.9

[3]

'

'

'

'

'

'

'

'

'

'

'

'

'

812.6

[4]

754.5

[4]

881.6

949.5

870.7

938.6

10.9

10.9

109.2

155

109.2

155

0

0

'

'

73.9

160.2

211.7

132.7

1,760.20

1,735.70

1,664.40

1,722.60

85.5

116.7

89.7

81.9

135.2

90

78

76.1

0

0

0

0

17.3

25.9

29.3

30.5

0

0

0

0

0

0

0

0

'

'

0

0

0

0

0

0

0

0

116.4

124.9

123.7

119.9

126

124.6

123.7

122.7

2,607.20

[5],[6]

2,581.50

[7]

627.1

[6]

625.4

[7]

1,777.80

[6]

1,754.20

[7]

202.3

[6]

201.9

[7]

73.3

[6]

131.1

[8]

73.3

131.1

0

0

0

0

812.6

[6]

754.5

[8]

0

0

809.5

754.5

3.1

0

279

[6]

239.6

[8]

0

0

279

239.6

0

0

87.2

[6]

106

[8]

0

0

104.4

106

0

0

141

[6]

145.5

[8]

0

0

141

145.5

0

0

104.4

[6]

91.5

[8]

0

0

87.2

91.5

0

0

68

[6]

40.5

[8]

0

0

67.1

40.5

3.1

0

67.1

[6]

64.4

[8]

0

0

64.9

64.4

0

0

36.9

[6]

38

[8]

0

0

36.9

38

0

0

29

[6]

29

[8]

0

0

29

29

0

0

66.1

[6]

16.5

[8]

0

0

66.1

16.5

0

0

881.6

[6]

949.5

[8]

0

0

870.7

938.6

10.9

10.9

1.3

[6]

2.3

[8]

0.6

1.6

0.7

0.7

0

0

84.7

[7]

83.3

[8]

0

0

13.2

12.3

71

1,919.60

[6]

1,937.20

[8]

73.9

132.7

1,760.20

1,722.60

85.5

81.9

238.4

[6]

157

[8]

238.1

155.9

0.3

1.1

0

0

315.5

[6]

336.9

[8]

315.1

336.8

0

0

0.4

0.1

114.4

[6]

122.6

[8]

114.4

122.6

0

0

0

0

71.2

[6]

83.3

[8]

70.8

83.2

0

0

0.4

0.1

27.1

[6]

34.7

[8]

27.1

34.7

0

0

0

0

19.1

[7]

20.3

[8]

19.1

20.3

0

0

0

0

10.3

[6]

8.3

[8]

10.3

8.3

0

0

0

0

73.4

[6]

67.7

[8]

73.4

67.7

0

0

0

0

17.3

[6]

30.5

[8]

0

0

17.3

30.5

0

0

116.4

[5],[6]

119.9

[7],[8]

0

[5]

0

[7]

0

[5]

0

[7]

116.4

[5]

119.9

[7]

'

'

Percentage of investments based on observable inputs

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4.00%

5.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of Fair Value Investments Using Observable Inputs

'

'

'

'

92.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other investments

134.8

'

134.8

'

139.6

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

47.6

49.4

54.4

56.1

14.2

14.4

0.2

0

15.6

14.9

18.4

19.7

20.2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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$203.90

$236.30

Percentage of private preferred stock

84.00%

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[1]

Excludes short-term investments which are deemed to have a LevelB 1 designation.

[2]

Excludes short-term investments which are deemed to have a LevelB 2 designation.

[3]

Excludes the carrying value of $20.2 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of September 30, 2013.

[4]

Credit ratings are assigned based on the following hierarchy: 1) Standard and Poorbs Financial Services LLC (bStandard and Poorbsb) and 2) Moodybs Investor Service (bMoodybsb).

[5]

Excludes the carrying value of $18.4 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of SeptemberB 30, 2014.

[6]

Fair value includes $203.9 million of fixed maturity investments reclassified to assets held for sale in the SeptemberB 30, 2014 consolidated balance sheets as part of the Runoff Transaction.

[7]

Excludes the carrying value of $19.7 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of DecemberB 31, 2013.

[8]

Fair value includes $236.3 million of fixed maturity investments reclassified to assets held for sale in the DecemberB 31, 2013 consolidated balance sheets as part of the Runoff Transaction.

Investment_Securities_Corporat

Investment Securities (Corporate debt securites) (Details) (Debt securities issued by corporations, USD $)	Sep. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	$812.60	[1]	$754.50	[1]
AA	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	55.2		51.2
A	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	327.1		357.9
BBB	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	426.2		345.4
BB	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		0
Other	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	$4.10		$0
[1]	Credit ratings are assigned based on the following hierarchy: 1) Standard and Poorbs Financial Services LLC (bStandard and Poorbsb) and 2) Moodybs Investor Service (bMoodybsb).

Investment_Securities_Fair_val1

Investment Securities (Fair value rollforward) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013
In Millions, unless otherwise specified			Level 2		Level 2		Level 2		Level 1		Level 1		Level 1		Level 3		Level 3		Level 3		Level 3		Level 3		Level 3		Tax Development Fund [Member]	Tax Development Fund [Member]	Tax Development Fund [Member]	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Fixed maturity investments	Common equity securities	Common equity securities	Common equity securities	Common equity securities	Common equity securities	Common equity securities	Common equity securities	Common equity securities	Common equity securities	Common equity securities	Common equity securities	Common equity securities	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Convertible fixed maturity investments	Other investments	Other investments	Other investments	Other investments	Other investments	Other investments	Other investments	Other investments	Other investments	Other investments	Other investments	Other investments
																														Level 2	Level 2	Level 2	Level 1	Level 1	Level 1	Level 3	Level 3	Level 3	Level 3	Level 3	Level 3	Level 3	Level 3	Level 2	Level 2	Level 2	Level 1	Level 1	Level 1	Level 3	Level 3	Level 3	Level 3	Level 3	Level 3	Level 2	Level 2	Level 2	Level 1	Level 1	Level 1	Level 3	Level 3	Level 3	Level 3	Level 3	Level 3	Level 2	Level 2	Level 2	Level 1	Level 1	Level 1	Level 3	Level 3	Level 3	Level 3	Level 3	Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'	'		'		'		'		'		'		'		'		'		'		'		'		'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'
Beginning Balance	'	'	$1,761.60	[1]	$1,693.70	[1]	$1,753.10	[1]	$519.30	[2]	$558.70	[2]	$469.50	[2]	$242.10	[3]	$213.50	[3]	$201.90	[3]	$214.70	[3]	$201.80	[3]	$198.90	[3]	'	'	'	$1,735.70	$1,664.40	$1,722.60	$160.20	$211.70	$132.70	$116.70	$89.70	$81.90	$90	$78	$76.10	$81.90	$76.10	$0	$0	$0	$359.10	$347	$336.80	$0.50	$0.10	$0.10	$0.10	$0.10	$0.10	$25.90	$29.30	$30.50	$0	$0	$0	$0	$0	$0	$0	$0	$0	$0	$0	$0	$0	$0	$0	$124.90	$123.70	$119.90	$124.60	$123.70	$122.70
Amortization/accretion	'	'	-2.9	[1]	-2.8	[1]	-2.7	[1]	0	[2]	0	[2]	0	[2]	0	[3]	0	[3]	0	[3]	0	[3]	0	[3]	0	[3]	'	'	'	-2.8	-2.7	-2.6	0	0	0	0	0	0	0	0	0	'	'	0	0	0	0	0	0	0	0	0	0	0	0	-0.1	-0.1	-0.1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Total net realized and unrealized gains (losses)	'	'	-7.7	[1]	5.5	[1]	6.9	[1]	-8.5	[2]	14.1	[2]	8.6	[2]	0.1	[3]	2.4	[3]	3.4	[3]	0.1	[3]	4	[3]	3.8	[3]	'	'	'	-6.8	7.2	5	0	1.3	0.1	1.1	0.3	0.3	-1.8	-0.2	0.1	'	'	0	0	0	-8.5	12.8	8.5	-0.1	0.4	0	0	0	0	-0.9	-1.7	1.9	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	-0.9	1.7	3.1	1.9	4.2	3.7
Purchases	'	'	426.3	[1]	349.8	[1]	347.8	[1]	128.1	[2]	279.2	[2]	140.6	[2]	2.3	[3]	35.2	[3]	9.8	[3]	1.3	[3]	17.4	[3]	3.6	[3]	'	'	'	423.5	345.1	344	113.7	256.6	114.6	2	34.2	7.5	0	14	1.8	'	'	0	0	0	14.4	22.6	26	0	0	0	0	0	0	2.8	4.7	3.8	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.3	1	2.3	1.3	3.4	1.8
Sales	'	'	-434.1	[1]	-292.1	[1]	-411.4	[1]	-249.9	[2]	-332.7	[2]	-60	[2]	-7.9	[3]	-1.5	[3]	-1.6	[3]	-2.3	[3]	-6.7	[3]	-4.5	[3]	'	'	'	-423.7	-285.8	-404.6	-200	-309.4	-35.7	0	0	0	-0.5	0	0	'	'	0	0	0	-49.9	-23.3	-24.3	0	0	0	0	0	0	-10.4	-6.3	-6.8	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	-7.9	-1.5	-1.6	-1.8	-6.7	-4.5
Transfers in	'	'	34.3	[1]	7.5	[1]	0	[1]	0	[2]	0	[2]	0	[2]	0	[3]	0	[3]	0	[3]	61.3	[3]	0	[3]	0	[3]	'	'	'	34.3	7.5	0	0	0	0	0	0	0	61.3	0	0	0	61.3	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Transfers out	'	'	0	[1]	0	[1]	0	[1]	0	[2]	0	[2]	0	[2]	-34.3	[3]	-7.5	[3]	0	[3]	-13.8	[3]	-1.8	[3]	0	[3]	'	'	'	0	0	0	0	0	0	-34.3	-7.5	0	-13.8	-1.8	0	'	'	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Ending Balance	'	'	1,777.50	[1]	1,761.60	[1]	1,693.70	[1]	389	[2]	519.3	[2]	558.7	[2]	202.3	[3]	242.1	[3]	213.5	[3]	261.3	[3]	214.7	[3]	201.8	[3]	'	'	'	1,760.20	1,735.70	1,664.40	73.9	160.2	211.7	85.5	116.7	89.7	135.2	90	78	85.5	135.2	0	0	0	315.1	359.1	347	0.4	0.5	0.1	0.1	0.1	0.1	17.3	25.9	29.3	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	116.4	124.9	123.7	126	124.6	123.7
Other Investments	134.8	139.6	'		'		'		'		'		'		'		'		'		'		'		'		18.4	19.7	20.2	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'
Fair Value Assets Measured on Recurring Basis Transfers out Recategorized	'	'	'		'		'		'		'		'		'		'		'		'		'		'		'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	$41.80	$15.60	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'
[1]	Excludes short-term investments which are deemed to have a LevelB 2 designation.
[2]	Excludes short-term investments which are deemed to have a LevelB 1 designation.
[3]	Excludes the carrying value of $20.2 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of September 30, 2013.

Investment_Securities_Securiti

Investment Securities (Securities classified as level 3) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Significant unobservable inputs	'
Number of Securities in each Asset type	1
Standard & Poor's, AA+ Rating [Member] | Mortgage-backed and asset-backed securities | Broker Pricing [Member]	'
Significant unobservable inputs	'
Assets, Fair Value Disclosure	$10.90	[1],[2]
Standard Poors N R Rating [Member] | Commercial | Discounted cash flow	'
Significant unobservable inputs	'
Assets, Fair Value Disclosure	3.1	[1],[2]
Default rate	1.20%
Standard Poors N R Rating [Member] | Preferred stocks | Discounted cash flow	'
Significant unobservable inputs	'
Assets, Fair Value Disclosure	$71.50	[1],[2]
Discount Rate	6.60%
[1]	As of SeptemberB 30, 2014, each asset type consists of one security.
[2]	Credit ratings are assigned based on the following hierarchy: 1) Standard & Poor's and 2) Moody's

Investment_Securities_Change_i

Investment Securities (Change in net unrealized gains or losses for Level 3 assets) (Details) (USD $)	3 Months Ended			9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	($34.80)	[1]	$21	($10.60)	[1]	($6.10)	[1]
Fixed maturity investments	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	-8		0.5	4	[1]	-33.7	[1]
Short-term investments	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	0		0	0		0
Convertible fixed maturity investments	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	-1.8		1	-4.1	[1]	-0.6	[1]
Other investments	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	-3.5		3.7	1.3	[1]	6.9	[1]
Level 3	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	-2.4		1.9	3		5.1
Level 3 | Fixed maturity investments	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	1.1		-1.8	1.7		-1.8
Level 3 | Short-term investments	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	0		0	0		0
Level 3 | Common equity securities	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	0		0	0		0
Level 3 | Convertible fixed maturity investments	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	0		0	0		0
Level 3 | Other investments	'		'	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'	'		'
Unrealized gains (losses) on unsold securities	($3.50)		$3.70	$1.30		$6.90
[1]	Includes pre-tax changes in net deferred gains and losses on sales of investments between OneBeacon and entities under White Mountains' common control of $(0.7) million and $(0.8) million for the three and nine months ended SeptemberB 30, 2013, respectively, with no such changes in net deferred gains and losses for the three and nine months ended September 30, 2014.

Investment_Securities_Asset_ba

Investment Securities (Asset backed securities) (Details) (USD $)

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

In Millions, unless otherwise specified

Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

$1,777.50

[1]

$1,761.60

[1]

$1,693.70

[1]

$1,753.10

[1]

'

'

'

'

Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

202.3

[2]

242.1

[2]

213.5

[2]

201.9

[2]

261.3

[2]

214.7

[2]

201.8

[2]

198.9

[2]

Fixed rate CMBS

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Average basis points of subordination

2000.00%

'

'

'

'

'

'

'

Fixed rate CMBS | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

62.3

'

'

'

'

'

'

'

Floating rate CMBS | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

46.9

'

'

'

'

'

'

'

GNMA | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

267.7

'

'

321.8

'

'

'

'

GNMA | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

267.7

'

'

321.8

'

'

'

'

GNMA | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

'

'

0

'

'

'

'

FNMA | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

20.6

'

'

36.5

'

'

'

'

FNMA | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

20.6

'

'

36.5

'

'

'

'

FNMA | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

'

'

0

'

'

'

'

FHLMC | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

1.1

'

'

24.3

'

'

'

'

FHLMC | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

1.1

'

'

24.3

'

'

'

'

FHLMC | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

'

'

0

'

'

'

'

Agency commercial mortgage-backed securities | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

289.4

[3]

'

'

382.6

[3]

'

'

'

'

Agency commercial mortgage-backed securities | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

289.4

[3]

'

'

382.6

[3]

'

'

'

'

Agency commercial mortgage-backed securities | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

[3]

'

'

0

[3]

'

'

'

'

Residential

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

94.7

'

'

'

'

'

'

'

Residential | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

94.7

'

'

51.5

'

'

'

'

Residential | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

94.7

'

'

51.5

'

'

'

'

Residential | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

'

'

0

'

'

'

'

Commercial | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

109.2

'

'

155

'

'

'

'

Commercial | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

109.2

'

'

155

'

'

'

'

Commercial | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

'

'

0

'

'

'

'

Total Non-agency | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

203.9

'

'

206.5

'

'

'

'

Total Non-agency | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

203.9

'

'

206.5

'

'

'

'

Total Non-agency | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

'

'

0

'

'

'

'

Total mortgage-backed securities | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

493.3

'

'

589.1

'

'

'

'

Total mortgage-backed securities | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

493.3

'

'

589.1

'

'

'

'

Total mortgage-backed securities | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

'

'

0

'

'

'

'

Credit card receivables | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

182.4

'

'

124.2

'

'

'

'

Credit card receivables | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

171.5

'

'

113.3

'

'

'

'

Credit card receivables | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

10.9

'

'

10.9

'

'

'

'

Vehicle receivables | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

162.1

'

'

189.3

'

'

'

'

Vehicle receivables | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

162.1

'

'

189.3

'

'

'

'

Vehicle receivables | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

'

'

0

'

'

'

'

Other | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

43.8

'

'

46.9

'

'

'

'

Other | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

43.8

'

'

46.9

'

'

'

'

Other | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

0

'

'

0

'

'

'

'

Total other asset-backed securities | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

388.3

'

'

360.4

'

'

'

'

Total other asset-backed securities | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

377.4

'

'

349.5

'

'

'

'

Total other asset-backed securities | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

10.9

'

'

10.9

'

'

'

'

Total mortgage-backed and asset-backed securities | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

881.6

'

'

949.5

'

'

'

'

Total mortgage-backed and asset-backed securities | Level 2

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

870.7

'

'

938.6

'

'

'

'

Total mortgage-backed and asset-backed securities | Level 3

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

10.9

'

'

10.9

'

'

'

'

Non-Prime Residential Mortgage Backed Security | Fair Value

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Debt securities issued by corporations

$4.10

'

'

'

'

'

'

'

Maximum | Commercial

'

'

'

'

'

'

'

'

Schedule of Trading Securities and Other Trading Assets [Line Items]

'

'

'

'

'

'

'

'

Percentage of underlying loans reported as non-performing

1.00%

'

'

'

'

'

'

'

[1]

Excludes short-term investments which are deemed to have a LevelB 2 designation.

[2]

Excludes the carrying value of $20.2 million associated with a tax advantaged federal affordable housing development fund accounted for using the equity method as of September 30, 2013.

[3]

Represents publicly traded mortgage-backed securities which carry the full faith and credit guarantee of the U.S. government (i.e.,B GNMA) or are guaranteed by a government sponsored entity (i.e.,B FNMA, FHLMC).

Investment_Securities_Nonagenc

Investment Securities (Non-agency securities) (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	$94.70		'
Super Senior | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	38.7	[1]	'
Senior | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	56	[2]	'
Subordinate | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0	[3]	'
Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	94.7		51.5
Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	109.2		155
Fair Value | Commercial Mortgage Backed Securities Floating Rate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	46.9		'
Fair Value | Commercial Mortgage Backed Securities Fixed Rate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	62.3		'
Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	203.9		206.5
Fair Value | Super Senior | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	25.2	[4]	'
Fair Value | Super Senior | Commercial Mortgage Backed Securities Floating Rate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0.7	[4]	'
Fair Value | Super Senior | Commercial Mortgage Backed Securities Fixed Rate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	24.5	[4]	'
Fair Value | Senior | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	20.3	[2]	'
Fair Value | Senior | Commercial Mortgage Backed Securities Floating Rate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0	[2]	'
Fair Value | Senior | Commercial Mortgage Backed Securities Fixed Rate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	20.3	[2]	'
Fair Value | Subordinate | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	63.7	[3]	'
Fair Value | Subordinate | Commercial Mortgage Backed Securities Floating Rate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	46.2	[3]	'
Fair Value | Subordinate | Commercial Mortgage Backed Securities Fixed Rate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	17.5	[3]	'
Securities Issued in 2004 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	5.4		'
Securities Issued in 2004 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		'
Securities Issued in 2004 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	5.4		'
Securities Issued in 2005 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	4.4		'
Securities Issued in 2005 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		'
Securities Issued in 2005 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	4.4		'
Securities Issued in 2006 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	5.3		'
Securities Issued in 2006 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		'
Securities Issued in 2006 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	5.3		'
Securities issued in 2007 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		'
Securities issued in 2007 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0.7		'
Securities issued in 2007 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0.7		'
Securities Issued in 2008 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	5.7		'
Securities Issued in 2008 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		'
Securities Issued in 2008 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	5.7		'
Securities Issued in 2009 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		'
Securities Issued in 2009 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		'
Securities Issued in 2009 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		'
Securities issued in 2010 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	4.1		'
Securities issued in 2010 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	6.7		'
Securities issued in 2010 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	10.8		'
Securities issued in 2011 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	15.5		'
Securities issued in 2011 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0		'
Securities issued in 2011 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	15.5		'
Securities issued in 2012 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	4		'
Securities issued in 2012 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	6.3		'
Securities issued in 2012 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	10.3		'
Securities Issued in 2013 | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	17.2		'
Securities Issued in 2013 | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	38.9		'
Securities Issued in 2013 | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	56.1		'
Securities Issued in 2014 [Member] | Fair Value | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	33.1		'
Securities Issued in 2014 [Member] | Fair Value | Commercial	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	56.6		'
Securities Issued in 2014 [Member] | Fair Value | Total	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	89.7		'
Residential, Prime, Financing Receivable [Member] | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	90.6		'
Residential, Prime, Financing Receivable [Member] | Super Senior | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	38.7	[1]	'
Residential, Prime, Financing Receivable [Member] | Senior | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	51.9	[2]	'
Residential, Prime, Financing Receivable [Member] | Subordinate | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0	[3]	'
Residential, Subprime, Financing Receivable [Member] | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	4.1		'
Residential, Subprime, Financing Receivable [Member] | Super Senior | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	0	[1]	'
Residential, Subprime, Financing Receivable [Member] | Senior | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	4.1	[2]	'
Residential, Subprime, Financing Receivable [Member] | Subordinate | Non-agency RMBS	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities issued by corporations	$0	[3]	'
[1]	At issuance, Super Senior, or in the case of resecuritization, the underlying securities, were rated AAA by StandardB & 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 StandardB & 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 StandardB & Poor's, Aaa by Moody's, or AAA by Fitch and were junior to other securities.
[4]	At issuance, Super Senior, or in the case of resecuritization, the underlying securities, were rated AAA by StandardB & Poor's, Aaa by Moody's or AAA by Fitch and were senior to other AAA or Aaa securities.

Investment_Securities_Other_in

Investment Securities (Other investments) (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments	$134.80		$139.60
Community Reinvestment Vehicle [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments	14.2		14.4
Long/short credit and distressed	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	8.5		8.1
Long bank loan	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	0.1		0.1
Long/short equity	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	36.6		39.1
Long/short equity activist	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	2.4		2.1
Hedge funds	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments	47.6		49.4
Other investments at fair value	47.6		49.4
Distributions from inactive hedge funds	0.9		'
Redemption requests	8.5		'
Hedge funds | 60 - 89 days notice	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	8.5		'
Hedge funds | Investment Redemption Notice Period over 120 Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	0.1		'
Hedge funds | Investment Redemption Notice Period 90 to 119 Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	8.4		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period thirty to fifty nine Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	30.6		'
Hedge funds | Monthly	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	1.8		'
Hedge funds | Monthly | 60 - 89 days notice	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	0		'
Hedge funds | Monthly | Investment Redemption Notice Period over 120 Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	0		'
Hedge funds | Monthly | Investment Redemption Notice Period 90 to 119 Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	0		'
Hedge funds | Monthly | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period thirty to fifty nine Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	1.8		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	43.3		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member] | 60 - 89 days notice	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	8.5		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member] | Investment Redemption Notice Period over 120 Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	0		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member] | Investment Redemption Notice Period 90 to 119 Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	6		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Quarterly [Member] | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period thirty to fifty nine Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	28.8		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	2.5		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member] | 60 - 89 days notice	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	0		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member] | Investment Redemption Notice Period over 120 Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	0.1		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member] | Investment Redemption Notice Period 90 to 119 Days [Member]	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	2.4		'
Hedge funds | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Frequency Annual [Member] | Fair Value Investments Entities that Calculate Net Asset Value Per Share Investment Redemption Notice Period thirty to fifty nine Days [Member]	'		'
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		2.3
Net asset value per share of unfunded commitments	0.1		0.1
Distressed residential real estate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	0		0.2
Net asset value per share of unfunded commitments	0		0
Energy infrastructure and services	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	26.3		26
Net asset value per share of unfunded commitments	4.8		5.9
Healthcare	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	2.9		2.8
Net asset value per share of unfunded commitments	1.4		1.4
Multi-sector	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	15.1		14.5
Net asset value per share of unfunded commitments	2.2		2.5
Private equity secondaries	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	6.3		6.4
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	1.6		3.9
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	54.4		56.1
Other investments at fair value	54.4		56.1
Net asset value per share of unfunded commitments	10.7		12.1
Private equity funds | 1 - 3 years	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	9.6		'
Private equity funds | 3 - 5 years	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	18.2		'
Private equity funds | 5 - 10 years	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Other investments at fair value	26.6		'
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	102	[1]	105.5	[1]
Net asset value per share of unfunded commitments	$10.70	[1]	$12.10	[1]
[1]	Excluded from the above table as of SeptemberB 30, 2014 and DecemberB 31, 2013 are other investments, which include an investment in a community reinvestment vehicle of $14.2 million and $14.4 million, respectively, and an investment in a tax advantaged federal affordable housing development fund of $18.4 million and $19.7 million, respectively. Additionally, other investments include trust certificates issued upon dissolution of a private equity fund of $0.2 million as of SeptemberB 30, 2014, with no such investment held as of DecemberB 31, 2013.

Debt_Details

Debt (Details) (OBH (issuer), USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Dec. 31, 2013	Nov. 30, 2012	Nov. 30, 2012	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified			OBH Senior Notes	OBH Senior Notes	OBH Senior Notes	2012 OBH Senior Notes	2012 OBH Senior Notes	Carrying Value	Carrying Value
Debt	'	'	'	'	'	'	'	'	'
Senior unsecured notes, at face value	'	'	$275	$275	$275	'	'	'	'
Unamortized original issue discount	-0.3	-0.3	'	'	'	'	'	'	'
Senior unsecured notes, carrying value	'	'	'	'	'	'	'	274.7	274.7
Percentage of par value at which debt was issued	'	'	'	'	'	99.90%	'	'	'
Issuance of debt, net of debt issuance costs	'	'	'	'	'	272.9	'	'	'
Interest rate (as a percent)	'	'	'	'	'	'	4.60%	'	'
Debt issue costs	'	'	'	'	'	2.8	'	'	'
Underwriting discount	'	'	'	'	'	$1.80	'	'	'
Effective yield (as a percent)	'	'	'	'	'	'	4.70%	'	'

Segment_Information_Details

Segment Information (Details) (USD $)

3 Months Ended

9 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2013

Dec. 31, 2012

segment

Units

Segment Information

'

'

'

'

'

'

'

'

Number of Major Underwriting Units

'

'

2

'

'

'

'

'

Net written premiums

$345.60

$314.10

$952.60

$826.10

'

'

'

'

Earned premiums

305.4

278.9

872.8

846.2

'

'

'

'

Loss and loss adjustment expense

-185.2

-167.8

-520.7

-473.7

'

'

'

'

Policy acquisition expenses

-54.6

-53.6

-150.9

-160.9

'

'

'

'

Other underwriting expenses

-51.2

-46.8

-152.3

-150.7

'

'

'

'

Total underwriting income (loss)

14.4

10.7

48.9

60.9

'

'

'

'

Net investment income

10.4

10.1

32.1

30.9

'

'

'

'

Net realized and change in unrealized investment gains

-16

17

24.8

19.9

'

'

'

'

Net other revenues

1.3

5.5

3.3

30.1

'

'

'

'

General and administrative expenses

-2.4

-4.1

-9.3

-11

'

'

'

'

Interest expense

-3.2

-3.3

-9.7

-9.8

'

'

'

'

Pre-tax income from continuing operations

4.5

35.9

90.1

121

'

'

'

'

Segment Information, Additional Disclosure

'

'

'

'

'

'

'

'

Total investment securities

2,421.70

'

2,421.70

'

'

2,364.90

'

'

Reinsurance recoverables

114.1

[1]

'

114.1

[1]

'

'

89.9

'

'

Deferred acquisition costs

121.8

'

121.8

'

'

103.7

'

'

Unpaid loss and loss adjustment expense reserves

1,159.60

1,052.90

1,159.60

1,052.90

1,125.40

1,054.30

1,027.80

1,000

Unearned premiums

625.2

'

625.2

'

'

544.9

'

'

Debt

274.7

'

274.7

'

'

274.7

'

'

Loss and LAE Ratio

60.60%

[2]

60.10%

[2]

59.70%

[2]

56.00%

[2]

'

'

'

'

Expense Ratio

34.70%

[2]

36.00%

[2]

34.70%

[2]

36.80%

[2]

'

'

'

'

Combined Ratio

95.30%

[2]

96.10%

[2]

94.40%

[2]

92.80%

[2]

'

'

'

'

Number of underwriting segments

'

'

14

'

'

'

'

'

Specialty Products

'

'

'

'

'

'

'

'

Segment Information

'

'

'

'

'

'

'

'

Net written premiums

188.3

172

488.6

393.3

'

'

'

'

Earned premiums

151.7

132.2

433

426.9

'

'

'

'

Loss and loss adjustment expense

-98.2

-84.2

-277.5

-240.6

'

'

'

'

Policy acquisition expenses

-26.6

-27.4

-71.4

-84.3

'

'

'

'

Other underwriting expenses

-23.2

-21.2

-68.1

-72.5

'

'

'

'

Total underwriting income (loss)

3.7

-0.6

16

29.5

'

'

'

'

Net investment income

0

0

0

0

'

'

'

'

Net realized and change in unrealized investment gains

0

0

0

0

'

'

'

'

Net other revenues

-0.3

0

-0.1

0.3

'

'

'

'

General and administrative expenses

0

0

0.1

-0.1

'

'

'

'

Interest expense

0

0

0

0

'

'

'

'

Pre-tax income from continuing operations

3.4

-0.6

16

29.7

'

'

'

'

Segment Information, Additional Disclosure

'

'

'

'

'

'

'

'

Total investment securities

0

'

0

'

'

0

'

'

Reinsurance recoverables

85.5

'

85.5

'

'

60.2

'

'

Deferred acquisition costs

66

'

66

'

'

53.6

'

'

Unpaid loss and loss adjustment expense reserves

678.2

'

678.2

'

'

607.8

'

'

Unearned premiums

332.4

'

332.4

'

'

275.4

'

'

Debt

0

'

0

'

'

0

'

'

Loss and LAE Ratio

64.70%

[2]

63.70%

[2]

64.10%

[2]

56.40%

[2]

'

'

'

'

Expense Ratio

32.90%

[2]

36.70%

[2]

32.20%

[2]

36.70%

[2]

'

'

'

'

Combined Ratio

97.60%

[2]

100.40%

[2]

96.30%

[2]

93.10%

[2]

'

'

'

'

Number of underwriting segments

'

'

8

'

'

'

'

'

Specialty Industries

'

'

'

'

'

'

'

'

Segment Information

'

'

'

'

'

'

'

'

Net written premiums

157.3

142.1

464

432.8

'

'

'

'

Earned premiums

153.7

146.7

439.8

419.3

'

'

'

'

Loss and loss adjustment expense

-87

-83.6

-243.2

-233.1

'

'

'

'

Policy acquisition expenses

-28

-26.2

-79.5

-76.6

'

'

'

'

Other underwriting expenses

-28

-25.6

-84.2

-78.2

'

'

'

'

Total underwriting income (loss)

10.7

11.3

32.9

31.4

'

'

'

'

Net investment income

0

0

0

0

'

'

'

'

Net realized and change in unrealized investment gains

0

0

0

0

'

'

'

'

Net other revenues

0.5

0.6

0.8

0.9

'

'

'

'

General and administrative expenses

-0.8

-1.1

-1.8

-2.3

'

'

'

'

Interest expense

0

0

0

0

'

'

'

'

Pre-tax income from continuing operations

10.4

10.8

31.9

30

'

'

'

'

Segment Information, Additional Disclosure

'

'

'

'

'

'

'

'

Total investment securities

0

'

0

'

'

0

'

'

Reinsurance recoverables

28.6

'

28.6

'

'

29.7

'

'

Deferred acquisition costs

55.8

'

55.8

'

'

50.1

'

'

Unpaid loss and loss adjustment expense reserves

481.4

'

481.4

'

'

446.5

'

'

Unearned premiums

292.8

'

292.8

'

'

269.5

'

'

Debt

0

'

0

'

'

0

'

'

Loss and LAE Ratio

56.70%

[2]

56.90%

[2]

55.30%

[2]

55.60%

[2]

'

'

'

'

Expense Ratio

36.40%

[2]

35.40%

[2]

37.20%

[2]

36.90%

[2]

'

'

'

'

Combined Ratio

93.10%

[2]

92.30%

[2]

92.50%

[2]

92.50%

'

'

'

'

Number of underwriting segments

'

'

6

'

'

'

'

'

Investing, Financing and Corporate

'

'

'

'

'

'

'

'

Segment Information

'

'

'

'

'

'

'

'

Earned premiums

0

0

0

0

'

'

'

'

Loss and loss adjustment expense

0

0

0

0

'

'

'

'

Policy acquisition expenses

0

0

0

0

'

'

'

'

Other underwriting expenses

0

0

0

0

'

'

'

'

Total underwriting income (loss)

0

0

0

0

'

'

'

'

Net investment income

10.4

10.1

32.1

30.9

'

'

'

'

Net realized and change in unrealized investment gains

-16

17

24.8

19.9

'

'

'

'

Net other revenues

1.1

4.9

2.6

28.9

'

'

'

'

General and administrative expenses

-1.6

-3

-7.6

-8.6

'

'

'

'

Interest expense

-3.2

-3.3

-9.7

-9.8

'

'

'

'

Pre-tax income from continuing operations

-9.3

25.7

42.2

61.3

'

'

'

'

Segment Information, Additional Disclosure

'

'

'

'

'

'

'

'

Total investment securities

2,421.70

[3]

'

2,421.70

[3]

'

'

2,364.90

[3]

'

'

Reinsurance recoverables

0

[3]

'

0

[3]

'

'

0

[3]

'

'

Deferred acquisition costs

0

[3]

'

0

[3]

'

'

0

[3]

'

'

Unpaid loss and loss adjustment expense reserves

0

[3]

'

0

[3]

'

'

0

[3]

'

'

Unearned premiums

0

[3]

'

0

[3]

'

'

0

[3]

'

'

Debt

274.7

[3]

'

274.7

[3]

'

'

274.7

[3]

'

'

Segment, Discontinued Operations

'

'

'

'

'

'

'

'

Segment Information

'

'

'

'

'

'

'

'

Net written premiums

0.1

1

-0.1

0.4

'

'

'

'

Securities reclassified to assets held for sale

203.9

'

203.9

'

'

236.3

'

'

Earned premiums

0.3

1.1

0.1

0.7

'

'

'

'

Loss and loss adjustment expense

0

-0.1

0.7

-7.6

'

'

'

'

Policy acquisition expenses

-0.8

-0.4

-2.2

-0.3

'

'

'

'

Segment Information, Additional Disclosure

'

'

'

'

'

'

'

'

Unpaid loss and loss adjustment expense reserves

$1,727.90

'

$1,727.90

'

'

$1,930

'

'

[1]

Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB+" (Adequate).

[2]

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.

[3]

As described in Note 2b"Acquisitions and Dispositions," balances related to the the Runoff Business are presented as held for sale. Total investment securities excludes $203.9 million and $236.3 million of fixed maturity investments reclassified to assets held for sale as of SeptemberB 30, 2014 and DecemberB 31, 2013, respectively.

Retirement_Plans_Periodic_Bene

Retirement Plans (Periodic Benefit Cost) (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Compensation and Retirement Disclosure [Abstract]	'		'		'		'
Service cost	$0.20		$0.20		$0.50		$0.60
Interest cost	1.2		1.1		3.5		3.2
Expected return on plan assets	-2.2		-1.8		-6.4		-5.4
Amortization of unrecognized loss	0.1		0.2		0.3		0.7
Net periodic pension income before special termination benefits	-0.7		-0.3		-2.1		-0.9
Special termination benefits expense(1)	0	[1]	0	[1]	0.3	[1]	0.3	[1]
Total net periodic benefit cost	-0.7		-0.3		-1.8		-0.6
Contributions to non-qualified plan in 2014	'		'		2.2		'
Pension contributions	$0.50		'		$1.60		'
[1]	Special termination benefits represent additional payments made from the Qualified Plan to certain vested participants when their employment was terminated due to a reduction in force.

Employee_ShareBased_Incentive_2

Employee Share-Based Incentive Compensation Plans Employee Share-Based Compensation Plans (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'	'	'	'
Allocated Share-based Compensation Expense	$0.80	$1.80	$4.80	$3.60

Employee_ShareBased_Incentive_3

Employee Share-Based Incentive Compensation Plans (Performance Shares) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Expense amortized	'	'	'		'
Expense recognized	($0.80)	($1.80)	($4.80)		($3.60)
Long Term Incentive Plan | Performance shares	'	'	'		'
Activity in plan	'	'	'		'
Beginning of period (in shares)	512,938	489,867	493,421		563,190
Payments and deferrals (in shares)	0	0	-142,138	[1]	-238,658	[1]
New awards (in shares)	0	0	165,800		179,000
Forfeitures and net change in assumed forfeitures (in shares)	0	0	-4,145		-13,665
End of period (in shares)	512,938	489,867	512,938		489,867
Expense amortized	'	'	'		'
Accrued expense at beginning of period	4.4	2.4	4		1.2
Payments and deferrals	0	0	-1	[1]	0	[1]
Forfeitures and net change in assumed forfeitures	0	0	0		-0.1
Expense recognized	-1.1	-0.1	-2.5		-1.4
Accrued expense at end of period	5.5	2.5	5.5		2.5
Additional disclosures	'	'	'		'
Target OB Performance Shares outstanding	512,938	'	512,938		'
Assumed forfeitures (in shares)	-13,152	'	-13,152		'
Assumed forfeitures	-0.1	'	-0.1		'
Additional compensation cost that would be recognized if all outstanding performance shares vested	3.7	'	3.7		'
Long Term Incentive Plan | Performance shares | Performance cycle 2011 - 2013	'	'	'		'
Additional disclosures	'	'	'		'
Growth target percentage	'	'	37.10%		'
Long Term Incentive Plan | Performance shares | Performance cycle 2012 - 2014	'	'	'		'
Expense amortized	'	'	'		'
Accrued expense at end of period	2.8	'	2.8		'
Additional disclosures	'	'	'		'
Target OB Performance Shares outstanding	181,290	'	181,290		'
Long Term Incentive Plan | Performance shares | Performance cycle 2013 - 2015	'	'	'		'
Expense amortized	'	'	'		'
Accrued expense at end of period	2.2	'	2.2		'
Additional disclosures	'	'	'		'
Target OB Performance Shares outstanding	179,000	'	179,000		'
Long Term Incentive Plan | Performance shares | Performance cycle 2014 - 2016	'	'	'		'
Expense amortized	'	'	'		'
Accrued expense at end of period	0.6	'	0.6		'
Additional disclosures	'	'	'		'
Target OB Performance Shares outstanding	165,800	'	165,800		'
Long Term Incentive Plan | Performance shares | Performance cycle 2012 - 2016	'	'	'		'
Expense amortized	'	'	'		'
Accrued expense at end of period	$5.60	'	$5.60		'
Additional disclosures	'	'	'		'
Target OB Performance Shares outstanding	526,090	'	526,090		'
Long Term Incentive Plan | Performance shares | Performance Cycle 2010 To 2012	'	'	'		'
Additional disclosures	'	'	'		'
Growth target percentage	'	'	0.00%		'
[1]	Performance share payments in 2014 for the 2011-2013 performance cycle were based upon a performance factor of 37.1%. No payments were made in 2013 for the 2010-2012 performance cycle as the performance factor was zero.

Employee_ShareBased_Incentive_4

Employee Share-Based Incentive Compensation Plans (Restricted) (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended			0 Months Ended	9 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	25-May-11	Sep. 30, 2014
					Restricted Stock [Member]	Restricted Stock [Member]	Restricted Stock [Member]	Restricted Stock [Member]	Awards Issued in 2012 [Member]	Chief Executive Officer [Member]	Chief Executive Officer [Member]
									Restricted Stock [Member]	Awards Issued in 2011 [Member]	Awards Issued in 2011 [Member]
										Restricted Stock [Member]	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	'	'	'	'	'	'	'2 years 0 months 19 days	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested	'	'	'	'	'	'	$4.30	$0.10	'	'	'
Activity in plan	'	'	'	'	'	'	'	'	'	'	'
Beginning of period (in shares)	'	'	'	'	612,500	918,000	915,000	927,000	'	'	'
New awards (in shares)	'	'	'	'	0	0	0	0	'	630,000	'
Forfeitures (in shares)	'	'	'	'	0	-3,000	-2,500	-3,000	'	'	'
Vested (in shares)	'	'	'	'	0	0	-300,000	-9,000	-142,500	'	-157,500
End of period (in shares)	'	'	'	'	612,500	915,000	612,500	915,000	140,000	'	472,500
Unamortized grant date fair value	'	'	'	'	'	'	'	'	'	'	'
Unamortized grant date fair value, beginning of period	'	'	'	'	4.9	8	6.5	9.6	'	'	'
Issued	'	'	'	'	0	0	0	0	'	'	'
Expense recognized	-0.8	-1.8	-4.8	-3.6	-0.7	-0.7	-2.3	-2.3	'	'	'
Unamortized grant date fair value, end of period	'	'	'	'	$4.20	$7.30	$4.20	$7.30	'	'	'

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Tax Contingency [Line Items]	'	'	'	'
Effective tax rate	-37.80%	-8.10%	11.20%	13.10%
Federal statutory rate	'	'	35.00%	35.00%
Income tax (expense) benefit	($1.70)	($2.90)	$10.10	$15.90
Foreign Tax Authority	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent	1.70%	0.50%	1.30%	0.30%
Tax Year 2005 to 2006 [Member] | Internal Revenue Service (IRS)	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Income tax (expense) benefit	'	'	5	'
Tax Assessment Year 2007 to 2009 | Internal Revenue Service (IRS)	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Income Tax Examination, Increase (Decrease) in Liability from Prior Year	72	'	72	'
Income Tax Examination, Increase (Decrease) in Liability from Prior Year, Related to Items with Unallowable Deductions	60.2	'	60.2	'
SurplusNoteRestructuring [Member]	'	'	'	'
Income Tax Contingency [Line Items]	'	'	'	'
Income tax (expense) benefit	'	$6.80	'	$6.80

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Details) (OBH (issuer), USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value	'	'
Fair Value of Financial Instruments	'	'
Senior unsecured notes, carrying value	$281.40	$269.80
Carrying Value	'	'
Fair Value of Financial Instruments	'	'
Senior unsecured notes, carrying value	$274.70	$274.70

Legal_Contingencies_Details

Legal Contingencies (Details) (Pending Litigation, Tribune Company Litigation, USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Pending Litigation | Tribune Company Litigation	'
Loss Contingencies [Line Items]	'
Proceeds common stock, litigation settlement	$32

Earnings_per_Share_Details

Earnings per Share (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Earnings attributable to OneBeacon's common shareholdersbbasic and diluted (in millions):	'		'		'		'
Net income from continuing operations attributable to OneBeacon's common shareholders	$6.20		$38.80		$79.10		$104.30
Allocation of loss (income) for participating unvested restricted common shares	-0.1		-0.4		-0.6		-1
Dividends paid on participating restricted common shares	-0.2		-0.2		-0.4		-0.6
Total allocation to restricted common shares	-0.3		-0.6		-1		-1.6
Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts	5.9		38.2		78.1		102.7
Undistributed Earnings, Basic [Abstract]	'		'		'		'
Net income from continuing operations attributable to OneBeacon's common shareholders, net of restricted common share amounts	5.9		38.2		78.1		102.7
Dividends paid, net of restricted common share amounts	-19.8		-19.8		-59.6		-59.5
Total undistributed (overdistributed) net earnings, net of restricted common share amounts	($13.90)		$18.40		$18.50		$43.20
Weighted Average Number of Shares Outstanding, Basic [Abstract]	'		'		'		'
Total weighted average common shares outstanding	95.3		95.4		95.3		95.4
Weighted average unvested restricted common shares	-0.6	[1]	-0.9	[1]	-0.7	[1]	-0.9	[1]
Basic and diluted earnings (loss) per share denominator	94.7		94.5		94.6		94.5
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]	'		'		'		'
Net income from continuing operations attributable to OneBeacon's common shareholders	$0.06		$0.41		$0.83		$1.09
Dividends declared and paid	($0.21)		($0.21)		($0.63)		($0.63)
Undistributed (overdistributed) earnings	($0.15)		$0.20		$0.20		$0.46
Total OneBeacon common shareholders' equity	'		'		'		'
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]	'		'		'		'
Dividends declared and paid	($0.21)		($0.21)		($0.63)		($0.63)
[1]	Restricted shares outstanding vest in equal installments upon a stated date or upon the occurrence of a specified event.

Common_Shareholders_Equity_Det

Common Shareholders' Equity (Details) (USD $)

3 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

12 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Aug. 22, 2007

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Class A common

Class A common

Common Stock

Common Stock

Total OneBeacon common shareholders' equity

Total OneBeacon common shareholders' equity

Total OneBeacon common shareholders' equity

Total OneBeacon common shareholders' equity

Accum. other comprehensive income (loss)

Accum. other comprehensive income (loss)

Equity, Class of Treasury Stock [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock Repurchase Program, Authorized Amount

'

'

'

'

$200,000,000

$87,700,000

'

'

'

'

'

'

'

'

Repurchase and retirement of common shares

'

'

1,800,000

'

'

'

106,366

3,300

'

'

1,800,000

'

0

'

Dividends

'

'

60,900,000

60,900,000

'

'

'

'

'

'

60,000,000

60,100,000

0

0

Dividends, per share, cash paid

$0.21

$0.21

$0.63

$0.63

'

'

'

'

$0.21

$0.21

$0.63

$0.63

'

'

Pre-tax changes to accumulated other comprehensive income

'

'

200,000

700,000

'

'

'

'

'

'

'

'

'

'

Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax

$0

($200,000)

($100,000)

($500,000)

'

'

'

'

'

'

($100,000)

($500,000)

($100,000)

($500,000)

Discontinued_Operations_Summar

Discontinued Operations (Summary of Reclassified Balances and Related Items) (Details) (USD $)	Sep. 30, 2014		Jun. 30, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
In Millions, unless otherwise specified
Discontinued Operations	'		'	'		'	'	'	'
Quota Share Reinsurance Agreement Percentage	'		'	'		'	'	'	100.00%
Assets	'		'	'		'	'	'	'
Investments	$2,421.70		'	$2,364.90		'	'	'	'
Premiums receivable	283.7		'	228.2		'	'	'	'
Reinsurance recoverable on unpaid losses	101.4		92	80.2		80.2	81.8	107.3	'
Reinsurance recoverables on paid losses	12.7		'	'		'	'	'	'
Other assets	307.2		'	272.7		'	'	'	'
Total assets	5,253.20		'	5,211.60		'	'	'	'
Liabilities	'		'	'		'	'	'	'
Unpaid loss and loss adjustment expense reserves	1,159.60		1,125.40	1,054.30		1,052.90	1,027.80	1,000	'
Unearned premiums	625.2		'	544.9		'	'	'	'
Other liabilities	352.1		'	338.6		'	'	'	'
Total liabilities	4,134.30		'	4,104.20		'	'	'	'
Segment, Discontinued Operations	'		'	'		'	'	'	'
Discontinued Operations	'		'	'		'	'	'	'
Reinsurance Recoverables, Gross	127		'	136.9		'	'	'	'
Assets	'		'	'		'	'	'	'
Reinsurance recoverable on unpaid losses	1,585.40		'	1,741.60		'	'	'	'
Liabilities	'		'	'		'	'	'	'
Unpaid loss and loss adjustment expense reserves	1,727.90		'	1,930		'	'	'	'
Segment, Discontinued Operations | Runoff	'		'	'		'	'	'	'
Assets	'		'	'		'	'	'	'
Investments	203.9		'	236.3		'	'	'	'
Premiums receivable	11.6		'	9.1		'	'	'	'
Reinsurance recoverable on unpaid losses	1,458.40	[1]	'	1,604.70	[1]	'	'	'	'
Reinsurance recoverables on paid losses	7.4		'	10.7		'	'	'	'
Net deferred tax asset	2.5		'	3.3		'	'	'	'
Other assets	15.4		'	16		'	'	'	'
Total assets	1,699.20		'	1,880.10		'	'	'	'
Liabilities	'		'	'		'	'	'	'
Unpaid loss and loss adjustment expense reserves	1,600.90		'	1,793.10		'	'	'	'
Unearned premiums	0		'	0.2		'	'	'	'
Ceded reinsurance payable	12.1		'	12.3		'	'	'	'
Other liabilities	86.2	[2]	'	74.5	[2]	'	'	'	'
Total liabilities	1,699.20		'	1,880.10		'	'	'	'
Pre-tax income (loss)	$80.50		'	$69		'	'	'	'
[1]	The SeptemberB 30, 2014 and DecemberB 31, 2013 balances include the remaining purchase accounting fair value adjustments of $127.0 million and $136.9 million, respectively, relating to the OneBeacon Acquisition. As of SeptemberB 30, 2014 and DecemberB 31, 2013, reinsurance recoverables on unpaid losses, gross of purchase accounting adjustments, were $1,585.4 million and $1,741.6 million, respectively, and unpaid loss and LAE reserves, gross of purchase accounting adjustments, were $1,727.9 million and $1,930.0 million for each period.
[2]	Other liabilities as of SeptemberB 30, 2014 and DecemberB 31, 2013 include the accrual related to the pre-tax loss on sale of the Runoff Business of $80.5 million and $69.0 million, respectively.

Discontinued_Operations_Summar1

Discontinued Operations (Summary of the Results of Operations) (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended			12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Dec. 31, 2013
					Segment, Discontinued Operations	Segment, Discontinued Operations	Segment, Discontinued Operations	Segment, Discontinued Operations	Runoff	Runoff
									Segment, Discontinued Operations	Segment, Discontinued Operations
Discontinued Operations	'	'	'	'	'	'	'	'	'	'
Net written premiums	$345.60	$314.10	$952.60	$826.10	$0.10	$1	($0.10)	$0.40	'	'
Revenues	'	'	'	'	'	'	'	'	'	'
Earned premiums	305.4	278.9	872.8	846.2	0.3	1.1	0.1	0.7	'	'
Other revenue	'	'	'	'	0	0	0	7.8	'	'
Total revenues	301.1	311.5	933	927.1	0.3	1.1	0.1	8.5	'	'
Expenses	'	'	'	'	'	'	'	'	'	'
Loss and loss adjustment expenses	185.2	167.8	520.7	473.7	0	0.1	-0.7	7.6	'	'
Policy acquisition expenses	'	'	'	'	0.1	0.1	0.1	0.1	'	'
Other underwriting expenses	54.6	53.6	150.9	160.9	0.8	0.4	2.2	0.3	'	'
Total expenses	296.6	275.6	842.9	806.1	0.9	0.6	1.6	8	'	'
Pre-tax income (loss)	'	'	'	'	-0.6	0.5	-1.5	0.5	'	69
Income tax (expense) benefit	-1.7	-2.9	10.1	15.9	0.3	-0.2	0.6	-0.2	'	'
Income (loss) from discontinued operations, net of tax	'	'	'	'	-0.3	0.3	-0.9	0.3	'	'
Net loss from sale of discontinued operations	-7	0	-7.5	0	-7	0	-7.5	0	'	'
Income (loss) from discontinued operations, net of tax	($0.30)	$0.30	($0.90)	$0.30	($7.30)	$0.30	($8.40)	$0.30	$52.40	'

Discontinued_Operations_Loss_p

Discontinued Operations (Loss per Share Related to Discontinued Operations) (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Income (loss) attributable to OneBeacon's common shareholdersbbasic and diluted (in millions):	'		'		'		'
Net income (loss) from discontinued operations attributable to OneBeacon's common shareholders	($0.30)		$0.30		($0.90)		$0.30
Allocation of income (loss) for participating unvested restricted common shares	-0.1		-0.4		-0.6		-1
Income (loss) per share denominatorbbasic and diluted (in millions):	'		'		'		'
Total weighted average common shares outstanding	95.3		95.4		95.3		95.4
Weighted average unvested restricted common shares	-0.6	[1]	-0.9	[1]	-0.7	[1]	-0.9	[1]
Basic and diluted earnings (loss) per share denominator	94.7		94.5		94.6		94.5
Loss per share attributable to OneBeacon's common shareholdersbbasic and diluted (in dollars):	'		'		'		'
Loss from discontinued operations attributable to OneBeacon's common shareholders per share	($0.01)		$0.41		$0.74		$1.09
Segment, Discontinued Operations	'		'		'		'
Income (loss) attributable to OneBeacon's common shareholdersbbasic and diluted (in millions):	'		'		'		'
Net income (loss) from discontinued operations attributable to OneBeacon's common shareholders	-7.3		0.3		-8.4		0.3
Allocation of income (loss) for participating unvested restricted common shares	0.1		0		0.1		0
Income (loss) from discontinued operations, net of tax	($7.20)		$0.30		($8.30)		$0.30
Income (loss) per share denominatorbbasic and diluted (in millions):	'		'		'		'
Total weighted average common shares outstanding	95.3		95.4		95.3		95.4
Weighted average unvested restricted common shares	-0.6		-0.9		-0.7		-0.9
Basic and diluted earnings (loss) per share denominator	94.7		94.5		94.6		94.5
Loss per share attributable to OneBeacon's common shareholdersbbasic and diluted (in dollars):	'		'		'		'
Loss from discontinued operations attributable to OneBeacon's common shareholders per share	($0.07)		$0		($0.09)		$0
[1]	Restricted shares outstanding vest in equal installments upon a stated date or upon the occurrence of a specified event.

Discontinued_Operations_Additi

Discontinued Operations (Additional Disclosures) (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Jun. 30, 2014

Dec. 31, 2013

Jun. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 30, 2014

Jun. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2001

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Dec. 31, 2013

Dec. 31, 2001

Sep. 30, 2014

Jun. 30, 2014

Sep. 30, 2014

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Runoff

Runoff

Runoff

Runoff

Runoff

Runoff

General Reinsurance Corporation Cover

Surplus Notes For Sale Of Discontinued Operations [Member]

Surplus Notes For Sale Of Discontinued Operations [Member]

Surplus Notes For Sale Of Discontinued Operations [Member]

rating

rating

GRC Cover

GRC Cover

NICO Cover

National Indemnity Company (NICO) and General Reinsurance Corporation

Hanover Insurance Company

Tokio Marine and Nichido Fire

Munich Reinsurance America

Tower Insurance Company

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

Segment, Discontinued Operations

GRC Cover

Dispositions

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Change In Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations

'

'

'

'

'

'

'

'

'

'

$6,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations

'

'

'

'

'

'

'

'

'

80,900,000

'

'

80,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Income (loss) from discontinued operations, net of tax

'

'

'

'

'

'

'

'

'

-7,200,000

'

300,000

-8,300,000

300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Quota Share Reinsurance Agreement Percentage

'

'

'

'

'

'

'

'

100.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reinsurance Recoverables, Gross

'

'

'

'

'

'

'

'

'

127,000,000

'

'

127,000,000

'

136,900,000

'

570,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reinsurance recoverable on unpaid losses

101,400,000

80,200,000

101,400,000

80,200,000

92,000,000

80,200,000

81,800,000

107,300,000

'

1,585,400,000

'

'

1,585,400,000

'

1,741,600,000

'

'

2,500,000,000

'

'

'

'

'

'

'

'

'

1,458,400,000

[1]

1,604,700,000

[1]

'

'

'

'

Unpaid loss and loss adjustment expense reserves

1,159,600,000

1,052,900,000

1,159,600,000

1,052,900,000

1,125,400,000

1,054,300,000

1,027,800,000

1,000,000,000

'

1,727,900,000

'

'

1,727,900,000

'

1,930,000,000

'

'

'

'

'

'

'

'

'

'

'

'

1,600,900,000

1,793,100,000

'

'

'

'

Pre-tax income (loss)

'

'

'

'

'

'

'

'

'

-600,000

'

500,000

-1,500,000

500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

69,000,000

'

'

'

'

Income (loss) from discontinued operations, net of tax

-300,000

300,000

-900,000

300,000

'

'

'

'

'

-7,300,000

'

300,000

-8,400,000

300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

52,400,000

'

'

'

'

'

Income (loss) from discontinued operations, net of tax

'

'

'

'

'

'

'

'

'

-300,000

'

300,000

-900,000

300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other revenue

'

'

'

'

'

'

'

'

'

0

'

0

0

7,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Liability for Unpaid Claims and Claims Adjustment Expense, Net

1,058,200,000

972,700,000

1,058,200,000

972,700,000

1,033,400,000

974,100,000

946,000,000

892,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

142,500,000

'

142,500,000

'

'

'

'

'

'

'

Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid

160,400,000

141,100,000

436,600,000

393,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-16,400,000

-17,400,000

-45,200,000

-88,800,000

'

'

'

'

'

'

Loss and loss adjustment expenses

185,200,000

167,800,000

520,700,000

473,700,000

'

'

'

'

'

0

'

100,000

-700,000

7,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net loss from sale of discontinued operations

-7,000,000

0

-7,500,000

0

'

'

'

'

'

-7,000,000

'

0

-7,500,000

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,300,000

'

Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense, Amount

'

'

'

'

'

'

'

'

'

7,400,000

7,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Causes Of Increase Decrease In Liability For Unpaid Claims And Claims Adjustment Expense Amount, net of tax

'

'

'

'

'

'

'

'

'

4,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax

'

'

'

'

'

'

'

'

'

'

'

'

-11,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

10,300,000

8,200,000

18,500,000

Surplus Notes Issued As Seller Financing In Sale Of Discontinued Operations, Fair Value

'

'

'

'

'

'

'

'

'

62,400,000

'

'

62,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Adverse loss reserve development on losses occurring in years 2000 and prior

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

400,000,000

'

'

'

Loss reserves ceded at acquisition

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

170,000,000

'

'

'

LAE claims, net

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,300,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reinsurance recoverables

114,100,000

[2]

'

114,100,000

[2]

'

'

89,900,000

'

'

'

'

'

'

'

'

'

337,300,000

'

1,700,000,000

1,127,400,000

[3]

30,700,000

25,400,000

[4]

28,300,000

14,000,000

'

'

'

'

'

'

'

'

'

'

LAE claims, estimated future losses

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

198,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Estimated incurred losses ceded

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

562,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reinsurance recoverables on paid losses

12,700,000

'

12,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7,400,000

10,700,000

'

'

'

'

Percentage of total paid and unpaid reinsurance recoverables

100.00%

[2]

'

100.00%

[2]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

71.00%

[3]

2.00%

2.00%

[4]

2.00%

1.00%

'

'

'

'

'

'

'

'

'

'

Number of ratings in A.M. Best ratings

'

'

'

'

'

'

'

'

'

16

'

'

16

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reinsurance recoverables

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$198,300,000

'

$21,800,000

'

'

'

'

'

'

'

'

'

'

'

'

[1]

The SeptemberB 30, 2014 and DecemberB 31, 2013 balances include the remaining purchase accounting fair value adjustments of $127.0 million and $136.9 million, respectively, relating to the OneBeacon Acquisition. As of SeptemberB 30, 2014 and DecemberB 31, 2013, reinsurance recoverables on unpaid losses, gross of purchase accounting adjustments, were $1,585.4 million and $1,741.6 million, respectively, and unpaid loss and LAE reserves, gross of purchase accounting adjustments, were $1,727.9 million and $1,930.0 million for each period.

[2]

Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB+" (Adequate).

[3]

Includes $198.3 million of Third Party Recoverables, which NICO would pay under the terms of the NICO Cover if they are unable to collect from third party reinsurers.

[4]

Excludes $21.8 million of reinsurance recoverables from the various reinsurers that are guaranteed by Tokio Marine and Nichido Fire.

Consolidating_Financial_Inform2

Consolidating Financial Information (Consolidating Balance Sheet) (Details) (USD $)	Sep. 30, 2014		Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Investments, Debt and Equity Securities [Abstract]	'		'	'	'	'	'
Fixed maturity investments, at fair value	$1,715.70		'	$1,700.90	'	'	'
Short-term investments, at amortized cost (which approximates fair value)	238.4		'	157	'	'	'
Common equity securities, at fair value	315.5		'	336.9	'	'	'
Convertible fixed maturity investments, at fair value	17.3		'	30.5	'	'	'
Other investments	134.8		'	139.6	'	'	'
Total investments	2,421.70		'	2,364.90	'	'	'
Cash	187.5		'	168.1	173.8	'	43.9
Reinsurance recoverables	114.1	[1]	'	89.9	'	'	'
Premiums receivable	283.7		'	228.2	'	'	'
Deferred acquisition costs	121.8		'	103.7	'	'	'
Net deferred tax asset	86.7		'	90.6	'	'	'
Investment income accrued	9.3		'	10.1	'	'	'
Accounts receivable on unsettled investment sales	22		'	3.3	'	'	'
Investments in subsidiaries	0		'	0	'	'	'
Other assets	307.2		'	272.7	'	'	'
Assets held for sale	1,699.20		'	1,880.10	'	'	'
Total assets	5,253.20		'	5,211.60	'	'	'
Liabilities	'		'	'	'	'	'
Unpaid loss and loss adjustment expense reserves	1,159.60		1,125.40	1,054.30	1,052.90	1,027.80	1,000
Unearned premiums	625.2		'	544.9	'	'	'
Debt	274.7		'	274.7	'	'	'
Accounts payable on unsettled investment purchases	23.5		'	11.6	'	'	'
Other liabilities	352.1		'	338.6	'	'	'
Liabilities held for sale	1,699.20		'	1,880.10	'	'	'
Total liabilities	4,134.30		'	4,104.20	'	'	'
Equity [Abstract]	'		'	'	'	'	'
OneBeacon's common shareholders' equity	1,115.60		'	1,104.30	'	'	'
Total noncontrolling interests	3.3		'	3.1	'	'	'
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,118.90		'	1,107.40	1,065	'	1,017.30
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	5,253.20		'	5,211.60	'	'	'
The Company (guarantor)	'		'	'	'	'	'
Investments, Debt and Equity Securities [Abstract]	'		'	'	'	'	'
Fixed maturity investments, at fair value	0		'	0	'	'	'
Short-term investments, at amortized cost (which approximates fair value)	10.3		'	13	'	'	'
Common equity securities, at fair value	0		'	0	'	'	'
Convertible fixed maturity investments, at fair value	0		'	0	'	'	'
Other investments	0		'	0	'	'	'
Total investments	10.3		'	13	'	'	'
Cash	0		'	0	0	'	0
Reinsurance recoverables	0		'	0	'	'	'
Premiums receivable	0		'	0	'	'	'
Deferred acquisition costs	0		'	0	'	'	'
Net deferred tax asset	0		'	0	'	'	'
Investment income accrued	0		'	0	'	'	'
Accounts receivable on unsettled investment sales	0		'	0	'	'	'
Investments in subsidiaries	1,106.90		'	1,092	'	'	'
Other assets	0.5		'	-0.8	'	'	'
Assets held for sale	0		'	0	'	'	'
Total assets	1,117.70		'	1,104.20	'	'	'
Liabilities	'		'	'	'	'	'
Unpaid loss and loss adjustment expense reserves	0		'	0	'	'	'
Unearned premiums	0		'	0	'	'	'
Debt	0		'	0	'	'	'
Accounts payable on unsettled investment purchases	0		'	0	'	'	'
Other liabilities	2.1		'	-0.1	'	'	'
Liabilities held for sale	0		'	0	'	'	'
Total liabilities	2.1		'	-0.1	'	'	'
Equity [Abstract]	'		'	'	'	'	'
OneBeacon's common shareholders' equity	1,115.60		'	1,104.30	'	'	'
Total noncontrolling interests	0		'	0	'	'	'
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,115.60		'	1,104.30	'	'	'
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	1,117.70		'	1,104.20	'	'	'
Non-guarantor subsidiaries	'		'	'	'	'	'
Investments, Debt and Equity Securities [Abstract]	'		'	'	'	'	'
Fixed maturity investments, at fair value	1,738.40		'	1,725.40	'	'	'
Short-term investments, at amortized cost (which approximates fair value)	224.8		'	140	'	'	'
Common equity securities, at fair value	315.5		'	336.9	'	'	'
Convertible fixed maturity investments, at fair value	17.3		'	30.5	'	'	'
Other investments	134.8		'	139.6	'	'	'
Total investments	2,430.80		'	2,372.40	'	'	'
Cash	187.5		'	166.6	173.4	'	43.9
Reinsurance recoverables	114.1		'	89.9	'	'	'
Premiums receivable	283.7		'	228.2	'	'	'
Deferred acquisition costs	121.8		'	103.7	'	'	'
Net deferred tax asset	86.4		'	93.1	'	'	'
Investment income accrued	9.8		'	10.3	'	'	'
Accounts receivable on unsettled investment sales	22		'	3.3	'	'	'
Investments in subsidiaries	0		'	0	'	'	'
Other assets	304.3		'	272.4	'	'	'
Assets held for sale	1,699.20		'	1,880.10	'	'	'
Total assets	5,259.60		'	5,220	'	'	'
Liabilities	'		'	'	'	'	'
Unpaid loss and loss adjustment expense reserves	1,159.60		'	1,054.30	'	'	'
Unearned premiums	625.2		'	544.9	'	'	'
Debt	0		'	0	'	'	'
Accounts payable on unsettled investment purchases	23.5		'	11.6	'	'	'
Other liabilities	340		'	335	'	'	'
Liabilities held for sale	1,699.20		'	1,880.10	'	'	'
Total liabilities	3,847.50		'	3,825.90	'	'	'
Equity [Abstract]	'		'	'	'	'	'
OneBeacon's common shareholders' equity	1,408.80		'	1,391	'	'	'
Total noncontrolling interests	3.3		'	3.1	'	'	'
Total OneBeacon's common shareholders' equity and noncontrolling interests	1,412.10		'	1,394.10	'	'	'
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	5,259.60		'	5,220	'	'	'
OBH (issuer)	'		'	'	'	'	'
Investments, Debt and Equity Securities [Abstract]	'		'	'	'	'	'
Fixed maturity investments, at fair value	2.9		'	0	'	'	'
Short-term investments, at amortized cost (which approximates fair value)	3.3		'	4	'	'	'
Common equity securities, at fair value	0		'	0	'	'	'
Convertible fixed maturity investments, at fair value	0		'	0	'	'	'
Other investments	0		'	0	'	'	'
Total investments	6.2		'	4	'	'	'
Cash	0		'	1.5	0.4	'	0
Reinsurance recoverables	0		'	0	'	'	'
Premiums receivable	0		'	0	'	'	'
Deferred acquisition costs	0		'	0	'	'	'
Net deferred tax asset	0		'	-2.4	'	'	'
Investment income accrued	0		'	0	'	'	'
Accounts receivable on unsettled investment sales	0		'	0	'	'	'
Investments in subsidiaries	1,079.40		'	1,034.90	'	'	'
Other assets	2.4		'	1.1	'	'	'
Assets held for sale	0		'	0	'	'	'
Total assets	1,088		'	1,039.10	'	'	'
Liabilities	'		'	'	'	'	'
Unpaid loss and loss adjustment expense reserves	0		'	0	'	'	'
Unearned premiums	0		'	0	'	'	'
Debt	299.7		'	299.7	'	'	'
Accounts payable on unsettled investment purchases	0		'	0	'	'	'
Other liabilities	10.5		'	3.9	'	'	'
Liabilities held for sale	0		'	0	'	'	'
Total liabilities	310.2		'	303.6	'	'	'
Equity [Abstract]	'		'	'	'	'	'
OneBeacon's common shareholders' equity	777.8		'	735.5	'	'	'
Total noncontrolling interests	0		'	0	'	'	'
Total OneBeacon's common shareholders' equity and noncontrolling interests	777.8		'	735.5	'	'	'
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	1,088		'	1,039.10	'	'	'
Consolidating adjustments	'		'	'	'	'	'
Investments, Debt and Equity Securities [Abstract]	'		'	'	'	'	'
Fixed maturity investments, at fair value	-25.6		'	-24.5	'	'	'
Short-term investments, at amortized cost (which approximates fair value)	0		'	0	'	'	'
Common equity securities, at fair value	0		'	0	'	'	'
Convertible fixed maturity investments, at fair value	0		'	0	'	'	'
Other investments	0		'	0	'	'	'
Total investments	-25.6		'	-24.5	'	'	'
Cash	0		'	0	0	'	0
Reinsurance recoverables	0		'	0	'	'	'
Premiums receivable	0		'	0	'	'	'
Deferred acquisition costs	'		'	0	'	'	'
Net deferred tax asset	0.3		'	-0.1	'	'	'
Investment income accrued	-0.5		'	-0.2	'	'	'
Accounts receivable on unsettled investment sales	0		'	0	'	'	'
Investments in subsidiaries	-2,186.30		'	-2,126.90	'	'	'
Other assets	0		'	0	'	'	'
Assets held for sale	0		'	0	'	'	'
Total assets	-2,212.10		'	-2,151.70	'	'	'
Liabilities	'		'	'	'	'	'
Unpaid loss and loss adjustment expense reserves	0		'	0	'	'	'
Unearned premiums	0		'	0	'	'	'
Debt	-25		'	-25	'	'	'
Accounts payable on unsettled investment purchases	0		'	0	'	'	'
Other liabilities	-0.5		'	-0.2	'	'	'
Liabilities held for sale	0		'	0	'	'	'
Total liabilities	-25.5		'	-25.2	'	'	'
Equity [Abstract]	'		'	'	'	'	'
OneBeacon's common shareholders' equity	-2,186.60		'	-2,126.50	'	'	'
Total noncontrolling interests	0		'	0	'	'	'
Total OneBeacon's common shareholders' equity and noncontrolling interests	-2,186.60		'	-2,126.50	'	'	'
Total liabilities, OneBeacon's common shareholders' equity and noncontrolling interests	($2,212.10)		'	($2,151.70)	'	'	'
[1]	Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB+" (Adequate).

Consolidating_Financial_Inform3

Consolidating Financial Information (Consolidating Statement of Operations and Comprehensive (Loss)) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues	'	'	'	'
Earned premiums	$305.40	$278.90	$872.80	$846.20
Net investment income (expense)	10.4	10.1	32.1	30.9
Net realized and change in unrealized investment gains	-16	17	24.8	19.9
Net other revenues	1.3	5.5	3.3	30.1
Total revenues	301.1	311.5	933	927.1
Expenses	'	'	'	'
Loss and loss adjustment expenses	185.2	167.8	520.7	473.7
Policy acquisition expenses	54.6	53.6	150.9	160.9
Other underwriting expenses	51.2	46.8	152.3	150.7
General and administrative expenses	2.4	4.1	9.3	11
Interest expense	3.2	3.3	9.7	9.8
Total expenses	296.6	275.6	842.9	806.1
Pre-tax (loss) income from continuing operations	4.5	35.9	90.1	121
Income tax (expense) benefit	1.7	2.9	-10.1	-15.9
Net loss from sale of discontinued operations	-7	0	-7.5	0
Net income from continuing operations	6.2	38.8	80	105.1
Net (income) loss from discontinued operations	0.3	-0.3	0.9	-0.3
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	-1.1	39.1	71.6	105.4
Equity in earnings of subsidiaries, net of tax	0	0	0	0
Net income (loss), including noncontrolling interests	-1.1	39.1	71.6	105.4
Less: Net income attributable to noncontrolling interests	0	0	-0.9	-0.8
Net income (loss) attributable to OneBeacon's common shareholders	-1.1	39.1	70.7	104.6
Net change in benefit plan assets and obligations, net of tax	0	0.2	0.1	0.5
Comprehensive income attributable to OneBeacon's common shareholders	-1.1	39.3	70.8	105.1
The Company (guarantor)	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
IncomeLossEquityMethodInvestmentsReclassification	'	3.7	'	3.7
Revenues	'	'	'	'
Earned premiums	0	0	0	0
Net investment income (expense)	0	0	0	0
Net realized and change in unrealized investment gains	0	0	0	0
Net other revenues	0	0	0	0
Total revenues	0	0	0	0
Expenses	'	'	'	'
Loss and loss adjustment expenses	0	0	0	0
Policy acquisition expenses	0	0	0	0
Other underwriting expenses	0	0	0	0
General and administrative expenses	0.5	1.7	4	3.6
Interest expense	0	0	0	0
Total expenses	0.5	1.7	4	3.6
Pre-tax (loss) income from continuing operations	-0.5	-1.7	-4	-3.6
Income tax (expense) benefit	0	0	0	0.1
Net loss from sale of discontinued operations	0	'	0	'
Net income from continuing operations	-0.5	-1.7	-4	-3.5
Net (income) loss from discontinued operations	0	0	0	0
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	-0.5	-1.7	-4	-3.5
Equity in earnings of subsidiaries, net of tax	-0.6	40.8	74.7	108.1
Net income (loss), including noncontrolling interests	-1.1	39.1	70.7	104.6
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to OneBeacon's common shareholders	-1.1	39.1	70.7	104.6
Net change in benefit plan assets and obligations, net of tax	0	0.2	0.1	0.5
Comprehensive income attributable to OneBeacon's common shareholders	-1.1	39.3	70.8	105.1
Non-guarantor subsidiaries	'	'	'	'
Revenues	'	'	'	'
Earned premiums	305.4	278.9	872.8	846.2
Net investment income (expense)	10.7	10.2	32.9	32.1
Net realized and change in unrealized investment gains	-16.3	17.2	25.8	19.7
Net other revenues	1.3	5.5	3.3	30.1
Total revenues	301.1	311.8	934.8	928.1
Expenses	'	'	'	'
Loss and loss adjustment expenses	185.2	167.8	520.7	473.7
Policy acquisition expenses	54.6	53.6	150.9	160.9
Other underwriting expenses	51.2	46.8	152.3	150.7
General and administrative expenses	1.9	2.2	5.1	7.5
Interest expense	0	0	0	0
Total expenses	292.9	270.4	829	792.8
Pre-tax (loss) income from continuing operations	8.2	41.4	105.8	135.3
Income tax (expense) benefit	1.6	0.5	-13.9	-23.3
Net loss from sale of discontinued operations	-7	'	-7.5	'
Net income from continuing operations	9.8	41.9	91.9	112
Net (income) loss from discontinued operations	0.3	-0.3	0.9	-0.3
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	2.5	42.2	83.5	112.3
Equity in earnings of subsidiaries, net of tax	0	0	0	0
Net income (loss), including noncontrolling interests	2.5	42.2	83.5	112.3
Less: Net income attributable to noncontrolling interests	0	0	-0.9	-0.8
Net income (loss) attributable to OneBeacon's common shareholders	2.5	42.2	82.6	111.5
Net change in benefit plan assets and obligations, net of tax	0	0	0	0
Comprehensive income attributable to OneBeacon's common shareholders	2.5	42.2	82.6	111.5
OBH (issuer)	'	'	'	'
Revenues	'	'	'	'
Earned premiums	0	0	0	0
Net investment income (expense)	0	0.2	0.1	-0.3
Net realized and change in unrealized investment gains	0	-0.4	0	-0.8
Net other revenues	0	0	0	0
Total revenues	0	-0.2	0.1	-1.1
Expenses	'	'	'	'
Loss and loss adjustment expenses	0	0	0	0
Policy acquisition expenses	0	0	0	0
Other underwriting expenses	0	0	0	0
General and administrative expenses	0	0.2	0.2	-0.1
Interest expense	3.5	3.5	10.6	10.6
Total expenses	3.5	3.7	10.8	10.5
Pre-tax (loss) income from continuing operations	-3.5	-3.9	-10.7	-11.6
Income tax (expense) benefit	0.3	2.5	3.5	7.7
Net loss from sale of discontinued operations	0	'	0	'
Net income from continuing operations	-3.2	-1.4	-7.2	-3.9
Net (income) loss from discontinued operations	0	0	0	0
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	-3.2	-1.4	-7.2	-3.9
Equity in earnings of subsidiaries, net of tax	-3.6	34	49.3	91.6
Net income (loss), including noncontrolling interests	-6.8	32.6	42.1	87.7
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to OneBeacon's common shareholders	-6.8	32.6	42.1	87.7
Net change in benefit plan assets and obligations, net of tax	0	0.2	0.1	0.5
Comprehensive income attributable to OneBeacon's common shareholders	-6.8	32.8	42.2	88.2
Consolidating adjustments	'	'	'	'
Revenues	'	'	'	'
Earned premiums	0	0	0	0
Net investment income (expense)	-0.3	-0.3	-0.9	-0.9
Net realized and change in unrealized investment gains	0.3	0.2	-1	1
Net other revenues	0	0	0	0
Total revenues	0	-0.1	-1.9	0.1
Expenses	'	'	'	'
Loss and loss adjustment expenses	0	0	0	0
Policy acquisition expenses	0	0	0	0
Other underwriting expenses	0	0	0	0
General and administrative expenses	0	0	0	0
Interest expense	-0.3	-0.2	-0.9	-0.8
Total expenses	-0.3	-0.2	-0.9	-0.8
Pre-tax (loss) income from continuing operations	0.3	0.1	-1	0.9
Income tax (expense) benefit	-0.2	-0.1	0.3	-0.4
Net loss from sale of discontinued operations	0	'	0	'
Net income from continuing operations	0.1	0	-0.7	0.5
Net (income) loss from discontinued operations	0	0	0	0
(Loss) income before equity in (losses) earnings of unconsolidated affiliates	0.1	0	-0.7	0.5
Equity in earnings of subsidiaries, net of tax	4.2	-74.8	-124	-199.7
Net income (loss), including noncontrolling interests	4.3	-74.8	-124.7	-199.2
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to OneBeacon's common shareholders	4.3	-74.8	-124.7	-199.2
Net change in benefit plan assets and obligations, net of tax	0	-0.2	-0.1	-0.5
Comprehensive income attributable to OneBeacon's common shareholders	$4.30	($75)	($124.80)	($199.70)

Consolidating_Financial_Inform4

Consolidating Financial Information (Consolidating Statement of Cash Flows) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]	'	'
Net income (loss) including noncontrolling interests	$71.60	$105.40
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	0.9	-0.3
Net loss from sale of discontinued operations	7.5	0
Net realized and change in unrealized investment gains	-24.8	-19.9
Net realized gain on sale of business	0	-23
Deferred income tax expense	8.6	12.3
Dividends received from subsidiaries	0	0
Other operating items:	'	'
Net change in loss and LAE reserves	105.3	52.9
Net change in unearned premiums	80.3	-21.1
Net change in premiums receivable	-55.5	-30.3
Net change in reinsurance recoverable on paid and unpaid losses	-24.2	24.5
Net change in other assets and liabilities	-22.8	77.8
Net cash provided from operationsbcontinuing operations	146.9	178.3
Net cash used for operationsbdiscontinued operations	-44.8	-98
Net cash provided from (used for) operations	102.1	80.3
Cash flows from investing activities:	'	'
Net maturities, purchases and sales of short-term investments	-81.5	67.3
Maturities of fixed maturity investments	202.6	196.6
Sales of fixed maturity investments	1,459.60	1,208.60
Sales of common equity securities	97.5	142
Sales of convertible fixed maturity investments	20.6	39.5
Distributions and redemptions of other investments	11.1	13.1
Purchases of fixed maturity investments	-1,641.20	-1,381.80
Purchases of common equity securities	-63	-168.5
Purchases of convertible fixed maturity investments	-11.3	-12
Contributions for other investments	-3.6	-7.1
Proceeds from sale of business	0	31.3
Net change in unsettled investment purchases and sales	-6.8	-7.7
Net acquisitions of property and equipment	-0.9	-7.6
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	'	0
Net cash provided from investing activitiesbcontinuing operations	-16.9	113.7
Net cash provided from investing activitiesbdiscontinued operations	0	0
Net cash provided from investing activities	-16.9	113.7
Cash flows from financing activities:	'	'
Cash dividends paid to common shareholders	-60	-60.1
Cash dividends paid to parent	0	0
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	-1.8	0
Net cash used for financing activitiesbcontinuing operations	-65.8	-64.1
Net cash used for financing activitiesbdiscontinued operations	0	0
Net cash used for financing activities	-65.8	-64.1
Net increase in cash during period	19.4	129.9
Cash balance at beginning of period	168.1	43.9
Cash balance at end of period	187.5	173.8
Proceeds from Contributed Capital	'	0
Repayments of Long-term Capital Lease Obligations	-4	-4
The Company (guarantor)	'	'
Condensed Financial Statements, Captions [Line Items]	'	'
IncomeLossEquityMethodInvestmentsReclassification	'	3.7
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]	'	'
Net income (loss) including noncontrolling interests	70.7	104.6
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:	'	'
Undistributed earnings from subsidiaries	-74.7	-108.1
Net loss from discontinued operations	0	0
Net loss from sale of discontinued operations	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	60.4	62
Other operating items:	'	'
Net change in loss and LAE reserves	0	0
Net change in unearned premiums	0	0
Net change in premiums receivable	0	0
Net change in reinsurance recoverable on paid and unpaid losses	0	0
Net change in other assets and liabilities	2.7	3.1
Net cash provided from operationsbcontinuing operations	59.1	61.6
Net cash used for operationsbdiscontinued operations	0	0
Net cash provided from (used for) operations	59.1	61.6
Cash flows from investing activities:	'	'
Net maturities, purchases and sales of short-term investments	2.7	-1.5
Maturities of fixed maturity investments	0	0
Sales of fixed maturity investments	0	0
Sales of common equity securities	0	0
Sales of convertible fixed maturity investments	0	0
Distributions and redemptions of other investments	0	0
Purchases of fixed maturity investments	0	0
Purchases of common equity securities	0	0
Purchases of convertible fixed maturity investments	0	0
Contributions for other investments	0	0
Proceeds from sale of business	'	0
Net change in unsettled investment purchases and sales	0	0
Net acquisitions of property and equipment	0	0
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	'	0
Net cash provided from investing activitiesbcontinuing operations	2.7	-1.5
Net cash provided from investing activitiesbdiscontinued operations	0	0
Net cash provided from investing activities	2.7	-1.5
Cash flows from financing activities:	'	'
Cash dividends paid to common shareholders	-60	-60.1
Cash dividends paid to parent	0	0
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	-1.8	'
Net cash used for financing activitiesbcontinuing operations	-61.8	-60.1
Net cash used for financing activitiesbdiscontinued operations	0	0
Net cash used for financing activities	-61.8	-60.1
Net increase in cash during period	0	0
Cash balance at beginning of period	0	0
Cash balance at end of period	0	0
Proceeds from Contributed Capital	'	0
Repayments of Long-term Capital Lease Obligations	0	0
Non-guarantor subsidiaries	'	'
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]	'	'
Net income (loss) including noncontrolling interests	83.5	112.3
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	0.9	-0.3
Net loss from sale of discontinued operations	7.5	'
Net realized and change in unrealized investment gains	-25.8	-19.7
Net realized gain on sale of business	'	-23
Deferred income tax expense	9	12.5
Dividends received from subsidiaries	0	0
Other operating items:	'	'
Net change in loss and LAE reserves	105.3	52.9
Net change in unearned premiums	80.3	-21.1
Net change in premiums receivable	-55.5	-30.3
Net change in reinsurance recoverable on paid and unpaid losses	-24.2	24.5
Net change in other assets and liabilities	-28.4	70.4
Net cash provided from operationsbcontinuing operations	152.6	178.2
Net cash used for operationsbdiscontinued operations	-44.8	-98
Net cash provided from (used for) operations	107.8	80.2
Cash flows from investing activities:	'	'
Net maturities, purchases and sales of short-term investments	-84.9	13.2
Maturities of fixed maturity investments	202.6	185.3
Sales of fixed maturity investments	1,450	1,114.60
Sales of common equity securities	97.5	142
Sales of convertible fixed maturity investments	20.6	39.5
Distributions and redemptions of other investments	11.1	13.1
Purchases of fixed maturity investments	-1,628.80	-1,227.80
Purchases of common equity securities	-63	-168.5
Purchases of convertible fixed maturity investments	-11.3	-12
Contributions for other investments	-3.6	-7.1
Proceeds from sale of business	'	31.3
Net change in unsettled investment purchases and sales	-6.8	-7.7
Net acquisitions of property and equipment	-0.9	-7.6
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	'	30
Net cash provided from investing activitiesbcontinuing operations	-17.5	138.3
Net cash provided from investing activitiesbdiscontinued operations	0	0
Net cash provided from investing activities	-17.5	138.3
Cash flows from financing activities:	'	'
Cash dividends paid to common shareholders	0	0
Cash dividends paid to parent	-65.4	-85
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	0	'
Net cash used for financing activitiesbcontinuing operations	-69.4	-89
Net cash used for financing activitiesbdiscontinued operations	0	0
Net cash used for financing activities	-69.4	-89
Net increase in cash during period	20.9	129.5
Cash balance at beginning of period	166.6	43.9
Cash balance at end of period	187.5	173.4
Proceeds from Contributed Capital	'	0
Repayments of Long-term Capital Lease Obligations	-4	-4
OBH (issuer)	'	'
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]	'	'
Net income (loss) including noncontrolling interests	42.1	87.7
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:	'	'
Undistributed earnings from subsidiaries	-49.3	-91.6
Net loss from discontinued operations	0	0
Net loss from sale of discontinued operations	0	'
Net realized and change in unrealized investment gains	0	0.8
Net realized gain on sale of business	'	0
Deferred income tax expense	0	-0.5
Dividends received from subsidiaries	5	23
Other operating items:	'	'
Net change in loss and LAE reserves	0	0
Net change in unearned premiums	0	0
Net change in premiums receivable	0	0
Net change in reinsurance recoverable on paid and unpaid losses	0	0
Net change in other assets and liabilities	2.8	4.1
Net cash provided from operationsbcontinuing operations	0.6	23.5
Net cash used for operationsbdiscontinued operations	0	0
Net cash provided from (used for) operations	0.6	23.5
Cash flows from investing activities:	'	'
Net maturities, purchases and sales of short-term investments	0.7	55.6
Maturities of fixed maturity investments	0	11.3
Sales of fixed maturity investments	9.6	129.7
Sales of common equity securities	0	0
Sales of convertible fixed maturity investments	0	0
Distributions and redemptions of other investments	0	0
Purchases of fixed maturity investments	-12.4	-189.7
Purchases of common equity securities	0	0
Purchases of convertible fixed maturity investments	0	0
Contributions for other investments	0	0
Proceeds from sale of business	'	0
Net change in unsettled investment purchases and sales	0	0
Net acquisitions of property and equipment	0	0
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	'	0
Net cash provided from investing activitiesbcontinuing operations	-2.1	6.9
Net cash provided from investing activitiesbdiscontinued operations	0	0
Net cash provided from investing activities	-2.1	6.9
Cash flows from financing activities:	'	'
Cash dividends paid to common shareholders	0	0
Cash dividends paid to parent	0	0
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	0	'
Net cash used for financing activitiesbcontinuing operations	0	-30
Net cash used for financing activitiesbdiscontinued operations	0	0
Net cash used for financing activities	0	-30
Net increase in cash during period	-1.5	0.4
Cash balance at beginning of period	1.5	0
Cash balance at end of period	0	0.4
Proceeds from Contributed Capital	'	-30
Repayments of Long-term Capital Lease Obligations	0	0
Consolidating adjustments	'	'
Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract]	'	'
Net income (loss) including noncontrolling interests	-124.7	-199.2
Charges (credits) to reconcile net income to cash flows (used for) provided from operations:	'	'
Undistributed earnings from subsidiaries	124	199.7
Net loss from discontinued operations	0	0
Net loss from sale of discontinued operations	0	'
Net realized and change in unrealized investment gains	1	-1
Net realized gain on sale of business	'	0
Deferred income tax expense	-0.4	0.3
Dividends received from subsidiaries	-65.4	-85
Other operating items:	'	'
Net change in loss and LAE reserves	0	0
Net change in unearned premiums	0	0
Net change in premiums receivable	0	0
Net change in reinsurance recoverable on paid and unpaid losses	0	0
Net change in other assets and liabilities	0.1	0.2
Net cash provided from operationsbcontinuing operations	-65.4	-85
Net cash used for operationsbdiscontinued operations	0	0
Net cash provided from (used for) operations	-65.4	-85
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	0	-35.7
Sales of common equity securities	0	0
Sales of convertible fixed maturity investments	0	0
Distributions and redemptions of other investments	0	0
Purchases of fixed maturity investments	0	35.7
Purchases of common equity securities	0	0
Purchases of convertible fixed maturity investments	0	0
Contributions for other investments	0	0
Proceeds from sale of business	'	0
Net change in unsettled investment purchases and sales	0	0
Net acquisitions of property and equipment	0	0
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	'	-30
Net cash provided from investing activitiesbcontinuing operations	0	-30
Net cash provided from investing activitiesbdiscontinued operations	0	0
Net cash provided from investing activities	0	-30
Cash flows from financing activities:	'	'
Cash dividends paid to common shareholders	0	0
Cash dividends paid to parent	65.4	85
Return of capital to OneBeacon U.S. Enterprises Holdings, Inc.	0	'
Net cash used for financing activitiesbcontinuing operations	65.4	115
Net cash used for financing activitiesbdiscontinued operations	0	0
Net cash used for financing activities	65.4	115
Net increase in cash during period	0	0
Cash balance at beginning of period	0	0
Cash balance at end of period	0	0
Proceeds from Contributed Capital	'	30
Repayments of Long-term Capital Lease Obligations	$0	$0