CONSOLIDATED BALANCE SHEETS (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets
Fixed maturity investments, at fair value	$ 6,221.9	$ 5,786.1
Short-term investments, at amortized cost (which approximates fair value)	846.0	975.3
Common equity securities, at fair value	755.0	667.0
Convertible fixed maturity investments, at fair value	143.8	143.0
Other long-term investments	301.3	372.1
Total investments	8,268.0	7,943.5
Cash (restricted $453.5 and $286.7)	705.4	395.0
Reinsurance recoverable on unpaid losses	2,507.3	2,344.0
Reinsurance recoverable on paid losses	30.5	63.1
Insurance and reinsurance premiums receivable	489.2	532.5
Funds held by ceding companies	106.5	118.7
Investments in unconsolidated affiliates	275.3	389.7
Deferred acquisition costs	187.0	176.1
Deferred tax asset	536.9	431.9
Ceded unearned insurance and reinsurance premiums	87.3	184.0
Accrued investment income	51.4	63.3
Accounts receivable on unsettled investment sales	4.7	39.5
Other assets	681.9	730.0
Assets held for sale	132.6	1,122.8
Total assets	14,064.0	14,534.1
Liabilities
Loss and loss adjustment expense reserves	5,702.3	5,736.8
Unearned insurance and reinsurance premiums	846.9	938.7
Variable annuity benefit guarantee	768.5	610.2
Debt	671.2	818.8
Deferred tax liability	365.5	373.2
Accrued incentive compensation	187.9	157.4
Funds held under reinsurance treaties	42.9	85.8
Ceded reinsurance payable	134.6	221.1
Accounts payable on unsettled investment purchases	34.6	22.3
Other liabilities	534.1	557.5
Liabilities held for sale	107.6	751.5
Total liabilities	9,396.1	10,273.3
White Mountains' common shareholders' equity
White Mountains' common shares at $1 par value per share-authorized 50,000,000 shares; issued and outstanding 7,577,855 and 8,194,925 shares	7.6	8.2
Paid-in surplus	1,253.7	1,350.8
Retained earnings	2,789.7	2,175.6
Accumulated other comprehensive income (loss), after-tax:
Equity in unrealized gains (losses) from investments in unconsolidated affiliates		58.5
Net unrealized foreign currency translation gains	46.1	61.4
Pension liability and other	(9.4)	(1.5)
Total White Mountains' common shareholders' equity	4,087.7	3,653.0
Noncontrolling interests
Noncontrolling interest-OneBeacon, Ltd.	273.1	295.0
Noncontrolling interest-SIG Preference Shares	250.0	250.0
Noncontrolling interest-consolidated limited partnerships and A.W.G Dewar	57.1	62.8
Total noncontrolling interests	580.2	607.8
Total equity	4,667.9	4,260.8
Total liabilities and equity	$ 14,064.0	$ 14,534.1