CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (USD $) In Millions, unless otherwise specified	Total	Common shareholders' equity	Common shares and paid-in surplus	Retained earnings	Accum. other comprehensive income (loss), after tax	Noncontrolling interests, after tax
Balances at Dec. 31, 2008		$ 1,155.1	$ 1,016.7	$ 163.4	$ (25.0)	$ 17.2
Increase (Decrease) in Stockholders' Equity
Net income	344.1	342.0		342.0		2.1
Amortization of restricted share and option awards		1.1	1.1
Issuance of common shares		0.3	0.3			0.3
Dividends		(79.9)		(79.9)		(0.6)
Contributions						5.1
Distributions						(5.0)
Distribution to White Mountains Insurance Group, Ltd.		(8.4)	(8.4)
Other comprehensive income and loss items, after tax:
Change in foreign currency translation	(0.1)	(0.1)			(0.1)
Change in interest rate swap	6.8	6.8			6.8
Change in pension	12.1	12.1			12.1
Other comprehensive income (loss), after tax	18.8	18.8			18.8
Balances at Dec. 31, 2009		1,429.0	1,009.7	425.5	(6.2)	19.1
Increase (Decrease) in Stockholders' Equity
Net income	119.9	118.3		118.3		1.6
Amortization of restricted share and option awards		0.9	0.9
Issuance of common shares		0.4	0.4			0.3
Repurchases and retirements of common shares		(10.5)	(10.5)
Dividends		(315.6)		(315.6)		(0.7)
Contributions						0.6
Distributions						(1.0)
Other comprehensive income and loss items, after tax:
Change in foreign currency translation	0.7	0.7			0.7
Change in pension	5.8	5.8			5.8
Other comprehensive income (loss), after tax	6.5	6.5			6.5
Balances at Dec. 31, 2010	1,248.9	1,229.0	1,000.5	228.2	0.3	19.9
Increase (Decrease) in Stockholders' Equity
Net income	56.1	55.1		55.1		1.0
Amortization of restricted share and option awards		1.4	1.4
Issuance of common shares		0.3	0.3			0.3
Repurchases and retirements of common shares						(1.3)
Dividends		(174.8)		(174.8)		(0.9)
Contributions						0.1
Distributions						(5.0)
Other comprehensive income and loss items, after tax:
Change in pension	(11.2)	(11.2)			(11.2)
Other comprehensive income (loss), after tax	(11.2)	(11.2)			(11.2)
Balances at Dec. 31, 2011	$ 1,113.9	$ 1,099.8	$ 1,002.2	$ 108.5	$ (10.9)	$ 14.1