Segment Information (Tables)

9 Months Ended

Sep. 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 September 30, 2012
Earned insurance and reinsurance premiums	$	293.9		$	242.9		$	—	$	536.8
Net investment income	12.8			16.7			8.1		37.6
Net realized and unrealized investment gains (losses)	40.0			(8.9		)	41.6		72.7
Other revenue	(.4		)	48.2			2.5		50.3
Total revenues	346.3			298.9			52.2		697.4
Losses and loss adjustment expenses	164.7			143.4			—		308.1
Insurance and reinsurance acquisition expenses	66.6			41.0			—		107.6
Other underwriting expenses	47.4			29.1			.1		76.6
General and administrative expenses	4.4			10.2			44.1		58.7
Interest expense on debt	4.1			6.5			.7		11.3
Total expenses	287.2			230.2			44.9		562.3
Pre-tax income	$	59.1		$	68.7		$	7.3	$	135.1

Millions	OneBeacon			Sirius Group			Other Operations			Total
Three Months Ended September 30, 2011
Earned insurance and reinsurance premiums	$	259.1		$	232.0		$	—		$	491.1
Net investment income	16.1			22.1			4.6			42.8
Net realized and unrealized investment gains (losses)	(47.4		)	65.9			(15.6		)	2.9
Other revenue	.1			(29.3		)	(5.8		)	(35.0		)
Total revenues	227.9			290.7			(16.8		)	501.8
Losses and loss adjustment expenses	149.7			130.5			—			280.2
Insurance and reinsurance acquisition expenses	58.6			48.4			—			107.0
Other underwriting expenses	36.0			28.3			—			64.3
General and administrative expenses	2.5			7.4			26.3			36.2
Interest expense on debt	4.1			6.5			2.2			12.8
Total expenses	250.9			221.1			28.5			500.5
Pre-tax (loss) income	$	(23.0	)	$	69.6		$	(45.3	)	$	1.3

Millions	OneBeacon			Sirius Group		Other Operations			Total
Nine Months Ended September 30, 2012
Earned insurance and reinsurance premiums	$	846.0		$	699.3	$	—		$	1,545.3
Net investment income	41.5			50.9		27.4			119.8
Net realized and unrealized investment gains (losses)	57.9			22.9		42.4			123.2
Other revenue	(.1		)	48.9		32.2			81.0
Total revenues	945.3			822.0		102.0			1,869.3
Losses and loss adjustment expenses	452.5			369.2		—			821.7
Insurance and reinsurance acquisition expenses	185.6			140.6		—			326.2
Other underwriting expenses	146.2			82.1		.1			228.4
General and administrative expenses	9.6			35.4		101.3			146.3
Interest expense on debt	12.2			19.6		1.3			33.1
Total expenses	806.1			646.9		102.7			1,555.7
Pre-tax income (loss)	$	139.2		$	175.1	$	(.7	)	$	313.6

Millions	OneBeacon			Sirius Group			Other Operations			Total
Nine Months Ended September 30, 2011
Earned insurance and reinsurance premiums	$	748.0		$	685.5		$	—		$	1,433.5
Net investment income	55.8			68.3			14.0			138.1
Net realized and unrealized investment gains (losses)	(13.3		)	60.7			(11.0		)	36.4
Other revenue	(12.2		)	(13.8		)	(2.3		)	(28.3		)
Total revenues	778.3			800.7			.7			1,579.7
Losses and loss adjustment expenses	421.3			499.1			—			920.4
Insurance and reinsurance acquisition expenses	161.5			135.1			—			296.6
Other underwriting expenses	124.5			79.4			—			203.9
General and administrative expenses	7.4			23.3			89.7			120.4
Interest expense on debt	16.4			19.6			2.8			38.8
Total expenses	731.1			756.5			92.5			1,580.1
Pre-tax income (loss)	$	47.2		$	44.2		$	(91.8	)	$	(.4	)