Segment Information (Tables)

3 Months Ended

Mar. 31, 2013

Segment Reporting [Abstract]

Financial information for White Mountains' segments

Significant intercompany transactions among White Mountains’ segments have been eliminated herein. Financial information for White Mountains’ segments follows:

					HG Global/BAM
Millions	OneBeacon		Sirius Group		HG			BAM			Other Operations			Total
Three Months Ended March 31, 2013
Earned insurance and reinsurance premiums	$	286.5	$	208.9	$	—		$	—		$	—		$	495.4
Net investment income	9.4		13.1		.3			1.1			4.6			28.5
Net investment income - surplus note income	—		—		10.1			(10.1		)	—			—
Net realized and unrealized investment    gains (losses)	28.4		13.1		(.2		)	(1.1		)	35.0			75.2
Other revenue	24.0		10.5		—			.1			(6.3		)	28.3
Total revenues	348.3		245.6		10.2			(10.0		)	33.3			627.4
Losses and loss adjustment expenses	148.9		95.4		—			—			—			244.3
Insurance and reinsurance acquisition expenses	54.8		43.3		—			.1			—			98.2
Other underwriting expenses	49.3		29.7		—			.1			—			79.1
General and administrative expenses	4.0		9.5		.3			8.2			21.8			43.8
Interest expense on debt	3.2		6.6		—			—			.4			10.2
Total expenses	260.2		184.5		.3			8.4			22.2			475.6
Pre-tax income (loss)	$	88.1	$	61.1	$	9.9		$	(18.4	)	$	11.1		$	151.8

Millions	OneBeacon		Sirius Group		Other Operations		Total
Three Months Ended March 31, 2012
Earned insurance and reinsurance premiums	$	271.8	$	226.2	$	—	$	498.0
Net investment income	14.7		17.1		10.0		41.8
Net realized and unrealized investment gains	29.8		13.7		15.1		58.6
Other revenue	.1		18.3		12.8		31.2
Total revenues	316.4		275.3		37.9		629.6
Losses and loss adjustment expenses	136.4		113.4		—		249.8
Insurance and reinsurance acquisition expenses	58.1		51.0		—		109.1
Other underwriting expenses	47.5		26.0		—		73.5
General and administrative expenses	2.7		18.9		23.9		45.5
Interest expense on debt	4.1		6.5		.3		10.9
Total expenses	248.8		215.8		24.2		488.8
Pre-tax income	$	67.6	$	59.5	$	13.7	$	140.8