CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE (LOSS) INCOME (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues
Earned premiums	$ 293.9	$ 259.1	$ 846.0	$ 748.0
Net investment income	12.8	16.1	41.5	55.8
Net realized and unrealized investment gains (losses)	40.0	(47.4)	57.9	(13.3)
Net other expenses	(0.4)		(0.1)	(12.2)
Total revenues	346.3	227.8	945.3	778.3
Expenses
Loss and loss adjustment expenses	164.7	149.7	452.5	421.3
Policy acquisition expenses	66.6	58.6	185.6	161.5
Other underwriting expenses	47.4	36.0	146.2	124.5
General and administrative expenses	4.4	2.5	9.7	7.4
Interest expense on debt	4.0	4.1	12.1	16.4
Total expenses	287.1	250.9	806.1	731.1
Pre-tax income (loss) from continuing operations	59.2	(23.1)	139.2	47.2
Income tax (expense) benefit	(14.2)	11.1	(28.1)	(1.9)
Net income (loss) from continuing operations	45.0	(12.0)	111.1	45.3
Loss from discontinued operations, net of tax	(15.8)	(2.5)	(24.8)	(1.5)
Loss from sale of discontinued operations, net of tax	(91.0)	(18.2)	(91.0)	(18.2)
Net (loss) income including noncontrolling interests	(61.8)	(32.7)	(4.7)	25.6
Less: Net income attributable to noncontrolling interests	(0.4)	(0.2)	(1.2)	(1.1)
Net (loss) income attributable to OneBeacon's common shareholders	(62.2)	(32.9)	(5.9)	24.5
Change in other comprehensive income and loss items	(2.0)	0.2	(1.7)	0.3
Comprehensive (loss) income attributable to OneBeacon's common shareholders	$ (64.2)	$ (32.7)	$ (7.6)	$ 24.8
Earnings (loss) per share attributable to OneBeacon's common shareholders - basic and diluted
Net income (loss) from continuing operations per Share (in dollars per share)	$ 0.47	$ (0.13)	$ 1.15	$ 0.46
Loss from discontinued operations, net of tax, per Share (in dollars per share)	$ (0.17)	$ (0.03)	$ (0.27)	$ (0.02)
Loss from sale of discontinued operations, net of tax, per share (in dollars per share)	$ (0.95)	$ (0.19)	$ (0.95)	$ (0.19)
Net (loss) income attributable to OneBeacon's common shareholders per share (in dollars per share)	$ (0.65)	$ (0.35)	$ (0.07)	$ 0.25
Dividends declared and paid per OneBeacon's common share (in dollars per share)	$ 0.21	$ 0.21	$ 0.63	$ 1.63