CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	10 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues:
Earned insurance premiums		$ 664.2	$ 22.8	$ 16.3
Net investment income		82.5	131.0	79.7
Net realized and unrealized investment gains (losses)		134.2	30.8	253.2
Realized gain (loss) from the 2019 MediaAlpha Transaction				67.5
Commission revenues		267.6	240.8	249.1
Other revenues		176.6	69.3	47.6
Total revenues		944.8	1,180.7	893.4
Expenses:
Insurance acquisition expenses		186.3	7.0	5.7
Loss and loss adjustment expenses		314.8
Cost of sales		69.3	11.3	48.1
General and administrative expenses		482.9	387.4	328.2
Broker commission expense		80.2	75.3	64.8
Change in fair value of contingent consideration		1.0	(3.3)	2.1
Amortization of other intangible assets		39.8	28.3	21.8
Loss on assets held for sale		28.7
Interest expense		43.8	29.5	17.6
Total expenses		1,246.8	535.5	488.3
Pre-tax income (loss) from continuing operations		(302.0)	645.2	405.1
Income tax (expense) benefit		(38.6)	20.5	(29.3)
Net income (loss) from continuing operations		(340.6)	665.7	375.8
Net gain (loss) from sale of discontinued operations, net of tax		18.7	(2.3)	0.8
Net income (loss)		(321.9)	663.4	376.6
Net income (loss) attributable to non-controlling interests		46.5	45.3	37.9
Net income (loss) attributable to White Mountains’s common shareholders		(275.4)	708.7	414.5
MediaAlpha
Revenues:
Net realized and unrealized investment gains (losses) from investment in MediaAlpha		(380.3)	686.0	180.0
Total revenues	$ 359.2
Expenses:
Total expenses	336.3
Net income (loss)	$ 22.9
HG Global-BAM
Revenues:
Earned insurance premiums		26.9	22.8	16.3
Net investment income		17.5	19.5	21.6
Net realized and unrealized investment gains (losses)		(22.9)	23.7	27.1
Realized gain (loss) from the 2019 MediaAlpha Transaction				0.0
Commission revenues		0.0	0.0	0.0
Other revenues		1.5	2.5	1.6
Total revenues		23.0	68.5	66.6
Expenses:
Insurance acquisition expenses		8.3	7.0	5.7
Loss and loss adjustment expenses		0.0
Cost of sales		0.0	0.0	0.0
General and administrative expenses		57.1	56.8	50.9
Broker commission expense		0.0	0.0	0.0
Change in fair value of contingent consideration		0.0	0.0	0.0
Amortization of other intangible assets		0.0	0.0	0.0
Loss on assets held for sale		0.0
Interest expense		0.0	0.0	0.0
Total expenses		65.4	63.8	56.6
Pre-tax income (loss) from continuing operations		(42.4)	4.7	10.0
HG Global-BAM | MediaAlpha
Revenues:
Net realized and unrealized investment gains (losses) from investment in MediaAlpha		0.0	0.0	0.0
Ark
Revenues:
Earned insurance premiums		637.3	0.0	0.0
Net investment income		2.9	0.0	0.0
Net realized and unrealized investment gains (losses)		16.5	0.0	0.0
Commission revenues		0.0
Other revenues		11.8	0.0	0.0
Total revenues		668.5	0.0	0.0
Expenses:
Insurance acquisition expenses		178.0	0.0	0.0
Loss and loss adjustment expenses		314.8	0.0	0.0
Cost of sales		0.0
General and administrative expenses		115.5	0.0	0.0
Broker commission expense		0.0
Change in fair value of contingent consideration		0.0
Amortization of other intangible assets		0.0
Loss on assets held for sale		0.0
Interest expense		7.3	0.0	0.0
Total expenses		615.6	0.0	0.0
Pre-tax income (loss) from continuing operations		52.9
Ark | MediaAlpha
Revenues:
Net realized and unrealized investment gains (losses) from investment in MediaAlpha		0.0
NSM
Revenues:
Earned insurance premiums		0.0	0.0	0.0
Net investment income		0.0	0.0	0.0
Net realized and unrealized investment gains (losses)		0.0	0.0	0.0
Realized gain (loss) from the 2019 MediaAlpha Transaction				0.0
Commission revenues		258.0	232.5	193.4
Other revenues		72.4	52.6	39.7
Total revenues		330.4	285.1	233.1
Expenses:
Insurance acquisition expenses		0.0	0.0	0.0
Loss and loss adjustment expenses		0.0
Cost of sales		0.0	0.0	0.0
General and administrative expenses		190.1	176.9	132.2
Broker commission expense		80.2	75.3	64.8
Change in fair value of contingent consideration		1.0	(3.3)	2.1
Amortization of other intangible assets		35.2	26.7	19.4
Loss on assets held for sale		28.7	0.0	0.0
Interest expense		23.3	22.1	16.7
Total expenses		358.5	297.7	235.2
Pre-tax income (loss) from continuing operations		(28.1)	(12.6)	(2.1)
NSM | MediaAlpha
Revenues:
Net realized and unrealized investment gains (losses) from investment in MediaAlpha		0.0	0.0	0.0
Kudu
Revenues:
Earned insurance premiums		0.0	0.0	0.0
Net investment income		43.9	29.5	14.7
Net realized and unrealized investment gains (losses)		89.9	15.9	6.3
Realized gain (loss) from the 2019 MediaAlpha Transaction				0.0
Commission revenues		0.0	0.0	0.0
Other revenues		0.2	0.3	0.2
Total revenues		134.0	45.7	21.2
Expenses:
Insurance acquisition expenses		0.0	0.0	0.0
Loss and loss adjustment expenses		0.0
Cost of sales		0.0	0.0	0.0
General and administrative expenses		14.5	11.8	10.1
Broker commission expense		0.0	0.0	0.0
Change in fair value of contingent consideration		0.0	0.0	0.0
Amortization of other intangible assets		0.3	0.3	0.2
Loss on assets held for sale		0.0
Interest expense		11.7	6.0	0.1
Total expenses		26.5	18.1	10.4
Pre-tax income (loss) from continuing operations		107.5	27.6	10.8
Kudu | MediaAlpha
Revenues:
Net realized and unrealized investment gains (losses) from investment in MediaAlpha		0.0	0.0	0.0
MediaAlpha
Revenues:
Earned insurance premiums				0.0
Net investment income				0.0
Net realized and unrealized investment gains (losses)				0.0
Realized gain (loss) from the 2019 MediaAlpha Transaction				0.0
Commission revenues		0.0	0.0	48.8
Other revenues				0.0
Total revenues		0.0	0.0	48.8
Expenses:
Insurance acquisition expenses				0.0
Cost of sales		0.0	0.0	40.6
General and administrative expenses		0.0		12.5
Broker commission expense				0.0
Change in fair value of contingent consideration				0.0
Amortization of other intangible assets		0.0	0.0	1.6
Interest expense		0.0	0.0	0.2
Total expenses		0.0	0.0	54.9
Pre-tax income (loss) from continuing operations				(6.1)
MediaAlpha | MediaAlpha
Revenues:
Net realized and unrealized investment gains (losses) from investment in MediaAlpha				0.0
Other Operations
Revenues:
Earned insurance premiums		0.0	0.0	0.0
Net investment income		18.2	82.0	43.4
Net realized and unrealized investment gains (losses)		50.7	(8.8)	219.8
Net realized and unrealized investment gains (losses) from investment in MediaAlpha		(380.3)	686.0	180.0
Realized gain (loss) from the 2019 MediaAlpha Transaction		0.0	0.0	67.5
Commission revenues		9.6	8.3	6.9
Other revenues		90.7	13.9	6.1
Total revenues		(211.1)	781.4	523.7
Expenses:
Insurance acquisition expenses		0.0	0.0	0.0
Loss and loss adjustment expenses		0.0
Cost of sales		69.3	11.3	7.5
General and administrative expenses		105.7	141.9	122.5
Broker commission expense		0.0	0.0	0.0
Change in fair value of contingent consideration		0.0	0.0	0.0
Amortization of other intangible assets		4.3	1.3	0.6
Loss on assets held for sale		0.0
Interest expense		1.5	1.4	0.6
Total expenses		180.8	155.9	131.2
Pre-tax income (loss) from continuing operations		$ (391.9)	$ 625.5	$ 392.5