Segment Information (Tables)

6 Months Ended

Jun. 30, 2015

Segment Reporting [Abstract]

Financial information for White Mountains' segments

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

							HG Global/BAM
Millions	OneBeacon			Sirius Group			HG			BAM			Other Operations			Total
Three Months Ended June 30, 2015
Earned insurance and reinsurance premiums	$	319.3		$	215.5		$	.6		$	.1		$	1.8		$	537.3
Net investment income	10.1			9.3			.5			.8			3.1			23.8
Net investment income (loss) - surplus note    interest	—			—			3.9			(3.9		)	—			—
Net realized and unrealized investment losses	(14.0		)	(42.7		)	(1.4		)	(1.9		)	(1.1		)	(61.1		)
Other (loss) revenue	(1.2		)	5.4			—			.2			83.1			87.5
Total revenues	314.2			187.5			3.6			(4.7		)	86.9			587.5
Losses and LAE	194.5			92.1			—			—			1.7			288.3
Insurance and reinsurance acquisition expenses	56.4			47.5			.1			.6			.7			105.3
Other underwriting expenses	52.9			27.7			—			.1			—			80.7
General and administrative expenses	4.2			6.8			.4			8.7			88.0			108.1
Interest expense	3.3			6.6			—			—			1.0			10.9
Total expenses	311.3			180.7			.5			9.4			91.4			593.3
Pre-tax income (loss)	$	2.9		$	6.8		$	3.1		$	(14.1	)	$	(4.5	)	$	(5.8	)

							HG Global/BAM
Millions	OneBeacon			Sirius Group			HG			BAM			Other Operations			Total
Six Months Ended June 30, 2015
Earned insurance and reinsurance premiums	$	605.9		$	420.5		$	1.1		$	.3		$	3.8		$	1,031.6
Net investment income	20.6			17.3			.9			1.8			6.5			47.1
Net investment income (loss) - surplus note    interest	—			—			7.9			(7.9		)	—			—
Net realized and unrealized investment gains (loses)	.2			37.2			(.3		)	1.1			4.1			42.3
Other revenue (loss)	(4.3		)	(22.0		)	—			.3			149.3			123.3
Total revenues	622.4			453.0			9.6			(4.4		)	163.7			1,244.3
Losses and LAE	360.4			189.6			—			—			3.7			553.7
Insurance and reinsurance acquisition expenses	107.4			90.1			.2			1.4			1.8			200.9
Other underwriting expenses	108.8			53.2			—			.2			—			162.2
General and administrative expenses	8.3			13.0			.8			16.9			185.5			224.5
Interest expense	6.5			13.4			—			—			2.1			22.0
Total expenses	591.4			359.3			1.0			18.5			193.1			1,163.3
Pre-tax income (loss)	$	31.0		$	93.7		$	8.6		$	(22.9	)	$	(29.4	)	$	81.0

						HG Global/BAM
Millions	OneBeacon		Sirius Group			HG		BAM			Other Operations			Total
Three Months Ended June 30, 2014
Earned insurance and reinsurance premiums	$	290.9	$	209.6		$	.3	$	.1		$	2.5		$	503.4
Net investment income	12.2		11.8			.3		1.4			3.9			29.6
Net investment income (loss) - surplus note    interest	—		—			4.0		(4.0		)	—			—
Net realized and unrealized investment gains	21.9		58.4			.9		3.8			28.9			113.9
Other revenue (loss)	1.0		(19.2		)	—		.1			24.5			6.4
Total revenues	326.0		260.6			5.5		1.4			59.8			653.3
Losses and LAE	186.1		91.4			—		—			5.2			282.7
Insurance and reinsurance acquisition expenses	49.6		48.8			.1		.5			(.1		)	98.9
Other underwriting expenses	51.7		30.2			—		.1			(.1		)	81.9
General and administrative expenses	3.6		6.9			.4		8.8			50.6			70.3
Interest expense	3.3		6.6			—		—			.1			10.0
Total expenses	294.3		183.9			.5		9.4			55.7			543.8
Pre-tax income (loss)	$	31.7	$	76.7		$	5.0	$	(8.0	)	$	4.1		$	109.5

						HG Global/BAM
Millions	OneBeacon		Sirius Group			HG		BAM			Other Operations			Total
Six Months Ended June 30, 2014
Earned insurance and reinsurance premiums	$	567.4	$	425.1		$	.5	$	.2		$	3.8		$	997.0
Net investment income	22.6		20.5			.6		2.8			7.8			54.3
Net investment income (loss) - surplus note    interest	—		—			7.9		(7.9		)	—			—
Net realized and unrealized investment gains	40.8		86.5			1.6		6.8			42.0			177.7
Other revenue (loss)	2.0		(24.5		)	—		.3			25.2			3.0
Total revenues	632.8		507.6			10.6		2.2			78.8			1,232.0
Losses and LAE	335.5		170.2			—		—			6.3			512.0
Insurance and reinsurance acquisition expenses	96.3		96.2			.2		.9			.4			194.0
Other underwriting expenses	101.1		62.0			—		.2			—			163.3
General and administrative expenses	6.9		15.3			.8		17.7			79.9			120.6
Interest expense	6.5		13.2			—		—			.4			20.1
Total expenses	546.3		356.9			1.0		18.8			87.0			1,010.0
Pre-tax income (loss)	$	86.5	$	150.7		$	9.6	$	(16.6	)	$	(8.2	)	$	222.0