Segment Information (Tables)

6 Months Ended

Jun. 30, 2012

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:

Millions	OneBeacon			Sirius Group			Other Operations			Total
Three Months Ended June 30, 2012
Earned insurance and reinsurance premiums	$	282.0		$	230.2		$	—		$	512.2
Net investment income	14.0			17.1			9.3			40.4
Net realized and unrealized investment (losses) gains	(11.9		)	18.1			(14.3		)	(8.1		)
Other revenue	.2			(17.6		)	16.9			(.5		)
Total revenues	284.3			247.8			11.9			544.0
Losses and loss adjustment expenses	152.5			112.5			—			265.0
Insurance and reinsurance acquisition expenses	60.1			48.6			—			108.7
Other underwriting expenses	52.0			27.0			—			79.0
General and administrative expenses	2.6			6.2			33.3			42.1
Interest expense on debt	4.0			6.6			.3			10.9
Total expenses	271.2			200.9			33.6			505.7
Pre-tax income (loss)	$	13.1		$	46.9		$	(21.7	)	$	38.3

Millions	OneBeacon			Sirius Group			Other Operations			Total
Three Months Ended June 30, 2011
Earned insurance and reinsurance premiums	$	247.5		$	230.8		$	—		$	478.3
Net investment income	18.7			22.7			4.4			45.8
Net realized and unrealized investment gains	11.0			31.0			.8			42.8
Other revenue	(11.5		)	(9.5		)	7.7			(13.3		)
Total revenues	265.7			275.0			12.9			553.6
Losses and loss adjustment expenses	137.9			140.6			—			278.5
Insurance and reinsurance acquisition expenses	53.5			45.0			—			98.5
Other underwriting expenses	44.1			27.3			—			71.4
General and administrative expenses	2.6			9.2			44.4			56.2
Interest expense on debt	6.0			6.6			.3			12.9
Total expenses	244.1			228.7			44.7			517.5
Pre-tax income (loss)	$	21.6		$	46.3		$	(31.8	)	$	36.1

Millions	OneBeacon		Sirius Group		Other Operations			Total
Six Months Ended June 30, 2012
Earned insurance and reinsurance premiums	$	554.8	$	456.4	$	—		$	1,011.2
Net investment income	28.7		34.2		19.3			82.2
Net realized and unrealized investment gains	17.9		31.8		.8			50.5
Other revenue	.3		.7		29.7			30.7
Total revenues	601.7		523.1		49.8			1,174.6
Losses and loss adjustment expenses	301.8		225.9		—			527.7
Insurance and reinsurance acquisition expenses	117.5		99.6		—			217.1
Other underwriting expenses	100.8		53.0		—			153.8
General and administrative expenses	5.3		25.1		57.2			87.6
Interest expense on debt	8.1		13.1		.6			21.8
Total expenses	533.5		416.7		57.8			1,008.0
Pre-tax income (loss)	$	68.2	$	106.4	$	(8.0	)	$	166.6

Millions	OneBeacon			Sirius Group			Other Operations			Total
Six Months Ended June 30, 2011
Earned insurance and reinsurance premiums	$	492.6		$	453.5		$	—		$	946.1
Net investment income	39.7			46.2			9.4			95.3
Net realized and unrealized investment gains (losses)	34.1			(5.1		)	4.6			33.6
Other revenue	(10.7		)	15.4			3.5			8.2
Total revenues	555.7			510.0			17.5			1,083.2
Losses and loss adjustment expenses	268.3			368.6			—			636.9
Insurance and reinsurance acquisition expenses	102.5			86.7			—			189.2
Other underwriting expenses	93.4			51.1			—			144.5
General and administrative expenses	4.9			15.9			63.4			84.2
Interest expense on debt	12.3			13.1			.6			26.0
Total expenses	481.4			535.4			64.0			1,080.8
Pre-tax income (loss)	$	74.3		$	(25.4	)	$	(46.5	)	$	2.4