CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Net investment income	$ 16.0	$ 19.7
Net realized and unrealized investment gains (losses)	245.6	(53.7)
Total revenues	433.6	42.1
Expenses:
Amortization of other intangible assets	6.6
Total expenses	151.9	108.1
Pre-tax income (loss) from continuing operations	281.7	(66.0)
Income tax expense	(10.2)	(0.7)
Net income (loss) from continuing operations	271.5	(66.7)
Net gain from sale of discontinued operations, net of tax	0.7	0.1
Net income (loss)	272.2	(66.6)
Net loss attributable to non-controlling interests	12.2	18.6
Net income (loss) attributable to White Mountains’s common shareholders	284.4	(48.0)
HG Global-BAM
Revenues:
Earned insurance premiums	4.2	3.0
Net investment income	5.3	3.7
Net realized and unrealized investment gains (losses)	11.8	(7.9)
Other revenue	0.6	0.2
Expenses:
Insurance acquisition expenses	1.3	1.4
General and administrative expenses	14.4	11.9
NSM Holding Co LLC
Revenues:
Commission revenues	43.3	0.0
Other revenue	6.0	0.0
Total revenues	49.3	0.0
Expenses:
General and administrative expenses	25.1	0.0
Broker commission expense	15.7	0.0
Change in fair value of contingent consideration earnout liabilities	1.3	0.0
Amortization of other intangible assets	5.0	0.0
Interest expense	3.7	0.0
Total expenses	50.8	0.0
MediaAlpha
Revenues:
Commission revenues	48.8	70.1
Other revenue	0.0	1.6
Expenses:
Cost of sales	40.6	57.4
General and administrative expenses	12.5	11.2
Amortization of other intangible assets	1.6	2.9
Interest expense	0.2	0.4
Other Segment
Revenues:
Earned insurance premiums	0.0	0.0
Net investment income	10.7	16.0
Net realized and unrealized investment gains (losses)	119.1	(45.8)
Realized and unrealized gains from the MediaAlpha Transaction		0.0
Commission revenues	1.3	0.9
Other revenue	0.3	0.3
Expenses:
Insurance acquisition expenses	0.0	0.0
Cost of sales	1.1	0.7
General and administrative expenses	29.4	22.0
Amortization of other intangible assets	0.0	0.0
Interest expense	0.0	0.2
HG Global-BAM | HG Global-BAM
Revenues:
Commission revenues	0.0	0.0
Total revenues	21.9	(1.0)
Expenses:
Cost of sales	0.0	0.0
Broker commission expense	0.0
Change in fair value of contingent consideration earnout liabilities	0.0
Amortization of other intangible assets	0.0
Interest expense	0.0	0.0
Total expenses	15.7	13.3
Pre-tax income (loss) from continuing operations	6.2	(14.3)
NSM Holding Co LLC | NSM Holding Co LLC
Revenues:
Earned insurance premiums	0.0
Net investment income	0.0
Net realized and unrealized investment gains (losses)	0.0
Total revenues	49.3
Expenses:
Insurance acquisition expenses	0.0
Cost of sales	0.0
Pre-tax income (loss) from continuing operations	(1.5)
MediaAlpha | MediaAlpha
Revenues:
Earned insurance premiums		0.0
Net investment income		0.0
Net realized and unrealized investment gains (losses)		0.0
Total revenues	48.8	71.7
Expenses:
Broker commission expense	0.0
Change in fair value of contingent consideration earnout liabilities	0.0
Total expenses	54.9	71.9
Pre-tax income (loss) from continuing operations	(6.1)	(0.2)
Other Operations | Other Segment
Revenues:
Total revenues	313.6	(28.6)
Expenses:
Broker commission expense	0.0
Change in fair value of contingent consideration earnout liabilities	0.0
Total expenses	30.5	22.9
Pre-tax income (loss) from continuing operations	283.1	(51.5)
Discontinued Operations
Expenses:
Net income (loss) attributable to White Mountains’s common shareholders	284.4	(48.0)
Swedish Tax Authority | Discontinued Operations | Sirius Group
Expenses:
Net gain from sale of discontinued operations, net of tax		$ 0.1
MediaAlpha | HG Global-BAM
Revenues:
Net realized and unrealized investment gains (losses)	0.0
MediaAlpha | Other Segment
Revenues:
Realized and unrealized gains from the MediaAlpha Transaction	182.2
MediaAlpha | NSM Holding Co LLC | NSM Holding Co LLC
Revenues:
Net realized and unrealized investment gains (losses)	$ 0.0