CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) (USD $) In Millions, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Revenues:
Earned insurance and reinsurance premiums	$ 495.8	$ 649.4	$ 982.0	$ 1,315.2
Net investment income	45.8	52.7	95.3	108.5
Net realized and unrealized investment gains	57.3	11.1	76.6	93.1
Other revenue	(27.8)	(23.6)	(34.8)	(13.5)
Total revenues	571.1	689.6	1,119.1	1,503.3
Expenses:
Loss and loss adjustment expenses	292.4	402.1	665.0	954.0
Insurance and reinsurance acquisition expenses	100.4	134.6	193.1	273.6
Other underwriting expenses	74.8	81.9	151.0	177.5
General and administrative expenses	56.2	52.3	84.2	87.4
Interest expense on debt	12.9	14.7	26.0	31.0
Total expenses	536.7	685.6	1,119.3	1,523.5
Pre-tax income (loss) from continuing operations	34.4	4.0	(0.2)	(20.2)
Income tax (expense) benefit	(9.5)	2.1	(1.6)	2.3
Net income (loss) from continuing operations	24.9	6.1	(1.8)	(17.9)
Net income (loss) from discontinued operations, net of tax	(0.3)	1.8	2.9	(0.8)
Income (loss) before equity in earnings (losses) of unconsolidated affiliates	24.6	7.9	1.1	(18.7)
Equity in earnings (losses) of unconsolidated affiliates	7.9	5.3	14.6	(6.3)
Net income (loss)	32.5	13.2	15.7	(25.0)
Net income attributable to noncontrolling interests	(20.8)	(10.7)	(32.2)	(12.1)
Net income (loss) attributable to White Mountains' common shareholders	11.7	2.5	(16.5)	(37.1)
Comprehensive income (loss), net of tax:
Change in equity in net unrealized gains from investments in unconsolidated affiliates	22.1	50.4	22.1	83.3
Change in foreign currency translation and other	(5.5)	(69.4)	56.5	(81.0)
Comprehensive income (loss)	28.3	(16.5)	62.1	(34.8)
Comprehensive income attributable to noncontrolling interests	0		0
Comprehensive income (loss) attributable to White Mountains' common shareholders	$ 28.3	$ (16.5)	$ 62.1	$ (34.8)
Basic income (loss) per share
Continuing operations (in dollars per share)	$ 1.51	$ 0.08	$ (2.42)	$ (4.15)
Discontinued operations (in dollars per share)	$ (0.03)	$ 0.20	$ 0.36	$ (0.09)
Diluted income (loss) per share
Continuing operations (in dollars per share)	$ 1.51	$ 0.08	$ (2.42)	$ (4.15)
Discontinued operations (in dollars per share)	$ (0.03)	$ 0.20	$ 0.36	$ (0.09)
Dividends declared and paid per White Mountains' common share (in dollars per share)			$ 1.00	$ 1.00