Segment Information (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2015
Earned insurance and reinsurance premiums	$	286.6		$	205.0		$	.5	$	.2		$	2.0		$	494.3
Net investment income	10.5			8.0			.4		1.0			3.4			23.3
Net investment income (loss) - surplus note    interest	—			—			4.0		(4.0		)	—			—
Net realized and unrealized investment gains	14.2			79.9			1.1		3.0			5.2			103.4
Other (loss) revenue	(3.1		)	(27.4		)	—		.1			66.2			35.8
Total revenues	308.2			265.5			6.0		.3			76.8			656.8
Losses and LAE	165.9			97.5			—		—			2.0			265.4
Insurance and reinsurance acquisition expenses	51.0			42.6			.1		.8			1.1			95.6
Other underwriting expenses	55.9			25.5			—		.1			—			81.5
General and administrative expenses	4.1			6.2			.4		8.2			97.5			116.4
Interest expense	3.2			6.8			—		—			1.1			11.1
Total expenses	280.1			178.6			.5		9.1			101.7			570.0
Pre-tax income (loss)	$	28.1		$	86.9		$	5.5	$	(8.8	)	$	(24.9	)	$	86.8

						HG Global/BAM
Millions	OneBeacon		Sirius Group			HG		BAM			Other Operations			Total
Three Months Ended March 31, 2014
Earned insurance and reinsurance premiums	$	276.5	$	215.5		$	.2	$	.1		$	1.3		$	493.6
Net investment income	10.4		8.7			.3		1.4			3.9			24.7
Net investment income (loss) - surplus note    interest	—		—			3.9		(3.9		)	—			—
Net realized and unrealized investment gains	18.9		28.1			.7		3.0			13.1			63.8
Other revenue (loss)	1.0		(5.3		)	—		.2			.7			(3.4		)
Total revenues	306.8		247.0			5.1		.8			19.0			578.7
Losses and LAE	149.4		78.8			—		—			1.1			229.3
Insurance and reinsurance acquisition expenses	46.7		47.4			.1		.4			.5			95.1
Other underwriting expenses	49.4		31.8			—		.1			.1			81.4
General and administrative expenses	3.3		8.4			.4		8.9			29.3			50.3
Interest expense	3.2		6.6			—		—			.3			10.1
Total expenses	252.0		173.0			.5		9.4			31.3			466.2
Pre-tax income (loss)	$	54.8	$	74.0		$	4.6	$	(8.6	)	$	(12.3	)	$	112.5