SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (Statement of Operations and Comprehensive Income) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (loss) (including realized gains and losses)		$ 87.5	$ 83.5	$ 88.8	$ (5.5)	$ 56.8	$ 48.4	$ 58.0	$ 373.8	$ 157.7	$ 440.0
Expenses		79.1	85.7	92.4	69.0	70.6	74.1	91.3	366.0	305.0	310.8
Pre-tax loss	$ 5.2	8.4	(2.2)	(3.6)	(74.5)	(13.8)	(25.7)	(33.3)	7.8	(147.3)	129.2
Income Tax (expense) benefit	2.5	4.0	1.0	0.3	10.2	17.1	4.0	1.6	7.8	32.9	(12.7)
Net income (loss) from continuing operations	7.7	12.4	(1.2)	(3.3)	(64.3)	3.3	(21.7)	(31.7)	15.6	(114.4)	116.5
Net gain from discontinued operations, net of tax	4.3	539.1	2.8	31.3	8.0	84.4	383.6	47.4	20.5	108.3	116.9
Net income attributable to White Mountains’s common shareholders	22.5	562.1	13.6	29.0	(38.9)	90.8	340.4	9.5	627.2	401.8	295.2
Other comprehensive income (loss), net of tax									0.3	(0.7)	(42.8)
Comprehensive income attributable to White Mountains’ common shareholders									630.5	547.1	187.4
Computation of net income (loss) available to common shareholders:
Net income attributable to White Mountains’s common shareholders	$ 22.5	$ 562.1	$ 13.6	$ 29.0	$ (38.9)	$ 90.8	$ 340.4	$ 9.5	627.2	401.8	295.2
White Mountains Insurance Group Ltd.
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Revenues (loss) (including realized gains and losses)									27.3	(1.0)	5.0
Expenses									99.7	68.2	59.9
Pre-tax loss									(72.4)	(69.2)	(54.9)
Income Tax (expense) benefit									(1.4)	(0.5)	0.0
Net income (loss) from continuing operations									(73.8)	(69.7)	(54.9)
Equity in earnings from consolidated and unconsolidated subsidiaries (2)									701.0	471.5	350.1
Net income attributable to White Mountains’s common shareholders									627.2	401.8	295.2
Other comprehensive income (loss), net of tax									3.3	145.3	(100.4)
Comprehensive income attributable to White Mountains’ common shareholders									630.5	547.1	194.8
Computation of net income (loss) available to common shareholders:
Net income attributable to White Mountains’s common shareholders									$ 627.2	401.8	295.2
WOBI
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT
Equity in earnings from consolidated and unconsolidated subsidiaries (2)										$ (10.7)	$ (2.4)