CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Earned insurance premiums	$ 10.4	$ 13.4	$ 12.0
Net investment income	56.0	32.1	10.9
Net realized and unrealized investment gains	133.3	(27.4)	260.5
Advertising & commission revenues	167.0	118.3	107.4
Other revenues	7.1	21.3	49.2
Total revenues	373.8	157.7	440.0
Expenses:
Loss and loss adjustment expenses	1.1	8.0	8.2
Insurance acquisition expenses	4.1	5.6	6.3
Cost of Sales	139.4	102.0	93.6
Other underwriting expenses	0.4	0.4	0.4
General and administrative expenses	218.7	186.0	200.7
Amortization of other intangible assets	10.7	10.5	8.4
Interest expense	2.3	3.0	1.6
Total expenses	366.0	305.0	310.8
Pre-tax (loss) income from continuing operations	7.8	(147.3)	129.2
Gain (loss) from sale of other discontinued operations, net of tax	557.0	415.1	18.2
Income tax benefit (expense)	7.8	32.9	(12.7)
Net income (loss) from continuing operations	15.6	(114.4)	116.5
Net (loss) income from discontinued operations, net of tax	20.5	108.3	116.9
Income before equity in earnings of unconsolidated affiliates	593.1	409.0	251.6
Equity in earnings of unconsolidated affiliates	0.0	0.0	25.1
Net income	593.1	409.0	276.7
Net (income) loss attributable to non-controlling interests	34.1	(7.2)	18.5
Net income attributable to White Mountains’s common shareholders	627.2	401.8	295.2
OneBeacon
Expenses:
Gain (loss) from sale of other discontinued operations, net of tax	554.5	0.0	0.0
Net (loss) income from discontinued operations, net of tax	20.5	108.6	38.2
Sale of Sirius Group
Expenses:
Gain (loss) from sale of other discontinued operations, net of tax	(0.7)	363.2	0.0
Tranzact
Expenses:
Gain (loss) from sale of other discontinued operations, net of tax	3.2	51.9	0.0
Esurance
Expenses:
Gain (loss) from sale of other discontinued operations, net of tax	0.0	0.0	17.9
Other Discontinued Operations
Expenses:
Gain (loss) from sale of other discontinued operations, net of tax	0.0	0.0	0.3
HG Global BAM
Revenues:
Earned insurance premiums	9.4	5.9	3.3
Net investment income	12.3	9.0	6.1
Net realized and unrealized investment gains	0.6	0.7	0.6
Other revenues	1.0	1.1	0.7
Total revenues	23.3	16.7	10.7
Expenses:
Insurance acquisition expenses	4.0	3.4	2.9
Other underwriting expenses	0.4	0.4	0.4
General and administrative expenses	42.9	39.6	36.8
Total expenses	47.3	43.4	40.1
MediaAlpha
Revenues:
Advertising & commission revenues	163.2	116.5	105.5
Total revenues	163.2	116.5	105.5
Expenses:
Cost of Sales	135.9	97.8	90.7
General and administrative expenses	16.2	11.8	8.3
Amortization of other intangible assets	10.5	10.1	8.1
Interest expense	1.0	0.9	0.4
Total expenses	163.6	120.6	107.5
Other
Revenues:
Earned insurance premiums	1.0	7.5	8.7
Net investment income	43.7	23.1	4.8
Net realized and unrealized investment gains	132.7	(28.1)	259.9
Advertising & commission revenues	3.8	1.8	1.9
Other revenues	6.1	20.2	48.5
Total revenues	187.3	24.5	323.8
Expenses:
Loss and loss adjustment expenses	1.1	8.0	8.2
Insurance acquisition expenses	0.1	2.2	3.4
Cost of Sales	3.5	4.2	2.9
General and administrative expenses	148.9	124.1	147.0
Amortization of other intangible assets	0.2	0.4	0.5
Interest expense	1.3	2.1	1.2
Total expenses	$ 155.1	$ 141.0	$ 163.2