CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues:
Earned insurance premiums	$ 506.8	$ 353.2	$ 1,070.6	$ 783.8
Net investment income	48.1	33.9	130.1	79.6
Net realized and unrealized investment gains (losses)	(58.3)	(48.0)	151.2	(255.2)
Commission revenues	3.5	3.2	10.0	8.7
Other revenues	19.5	40.9	68.0	103.4
Total revenues	519.6	383.2	1,429.9	720.3
Expenses:
Loss and loss adjustment expenses	265.8	213.7	581.1	456.2
Acquisition expenses	92.4	76.5	217.8	184.4
Cost of sales	8.0	25.0	33.5	68.8
General and administrative expenses	99.6	85.8	298.2	256.9
Change in fair value of contingent consideration	17.0	2.7	16.8	4.9
Interest expense	15.7	10.5	44.9	27.5
Total expenses	498.5	414.2	1,192.3	998.7
Pre-tax income (loss) from continuing operations	21.1	(31.0)	237.6	(278.4)
Income tax (expense) benefit	(7.3)	7.4	(19.4)	26.1
Net income (loss) from continuing operations	13.8	(23.6)	218.2	(252.3)
Net income (loss) from discontinued operations, net of tax - NSM Group	0.0	6.3	0.0	16.4
Net gain (loss) from sale of discontinued operations, net of tax - NSM Group	0.0	886.8	0.0	886.8
Net income (loss)	13.8	869.5	218.2	650.9
Net (income) loss attributable to noncontrolling interests	9.8	18.7	4.5	101.5
Net income (loss) attributable to White Mountains’s common shareholders	23.6	888.2	222.7	752.4
Other Operations
Revenues:
Earned insurance premiums	0.0	0.0	0.0	0.0
Net investment income	8.0	8.5	22.0	13.6
Commission revenues	3.5	3.2	10.0	8.7
Other revenues	15.2	33.0	67.1	89.6
Total revenues	(12.1)	8.8	186.0	1.4
Expenses:
Loss and loss adjustment expenses	0.0	0.0	0.0	0.0
Acquisition expenses	0.0	0.0	0.0	0.0
Cost of sales	8.0	25.0	33.5	68.8
General and administrative expenses	42.2	41.3	130.7	122.1
Change in fair value of contingent consideration	0.0	0.0	0.0	0.0
Interest expense	0.9	0.6	2.9	1.2
Total expenses	51.1	66.9	167.1	192.1
Pre-tax income (loss) from continuing operations	(63.2)	(58.1)	18.9	(190.7)
Investments, Excluding MediaAlpha
Revenues:
Net realized and unrealized investment gains (losses)	(11.5)	(29.4)	190.1	(141.9)
Investments, Excluding MediaAlpha | Other Operations
Revenues:
Net realized and unrealized investment gains (losses)	8.0	(17.3)	125.8	2.8
MediaAlpha
Revenues:
Net realized and unrealized investment gains (losses)	(46.8)	(18.6)	(38.9)	(113.3)
MediaAlpha | Other Operations
Revenues:
Net realized and unrealized investment gains (losses)	(46.8)	(18.6)	(38.9)	(113.3)
HG Global/BAM | Operating Segments
Revenues:
Earned insurance premiums	7.9	7.1	23.3	26.0
Net investment income	8.1	5.7	22.9	15.1
Net realized and unrealized investment gains (losses)	(24.1)	(38.8)	(17.0)	(114.0)
Other revenues	0.7	1.3	2.0	3.7
Total revenues	(7.4)	(24.7)	31.2	(69.2)
Expenses:
Acquisition expenses	2.1	1.7	6.3	9.5
General and administrative expenses	17.5	15.8	49.7	49.5
Interest expense	3.8	2.0	10.8	5.4
Total expenses	23.4	19.5	66.8	64.4
P&C Insurance and Reinsurance (Ark/WM Outrigger)
Expenses:
Loss and loss adjustment expenses	265.8	213.7	581.1	456.2
P&C Insurance and Reinsurance (Ark/WM Outrigger) | Operating Segments
Revenues:
Earned insurance premiums	498.9	346.1	1,047.3	757.8
Net investment income	16.9	4.9	41.2	9.7
Net realized and unrealized investment gains (losses)	(6.6)	(14.4)	35.9	(76.5)
Other revenues	3.6	6.6	(1.1)	10.1
Total revenues	512.8	343.2	1,123.3	701.1
Expenses:
Loss and loss adjustment expenses	265.8	213.7	581.1	456.2
Acquisition expenses	90.3	74.8	211.5	174.9
General and administrative expenses	35.4	24.2	105.5	74.9
Change in fair value of contingent consideration	17.0	2.7	16.8	4.9
Interest expense	5.5	3.7	15.7	10.6
Total expenses	414.0	319.1	930.6	721.5
Kudu | Operating Segments
Revenues:
Earned insurance premiums	0.0	0.0	0.0	0.0
Net investment income	15.1	14.8	44.0	41.2
Net realized and unrealized investment gains (losses)	11.2	41.1	45.4	45.8
Commission revenues	0.0	0.0	0.0	0.0
Other revenues	0.0	0.0	0.0	0.0
Total revenues	26.3	55.9	89.4	87.0
Expenses:
Loss and loss adjustment expenses	0.0	0.0	0.0	0.0
Acquisition expenses	0.0	0.0	0.0	0.0
Cost of sales	0.0	0.0	0.0	0.0
General and administrative expenses	4.5	4.5	12.3	10.4
Change in fair value of contingent consideration	0.0	0.0	0.0	0.0
Interest expense	5.5	4.2	15.5	10.3
Total expenses	10.0	8.7	27.8	20.7
Pre-tax income (loss) from continuing operations	16.3	47.2	61.6	66.3
Kudu | Investments, Excluding MediaAlpha | Operating Segments
Revenues:
Net realized and unrealized investment gains (losses)	11.2	41.1	45.4	45.8
Kudu | MediaAlpha | Operating Segments
Revenues:
Net realized and unrealized investment gains (losses)	$ 0.0	$ 0.0	$ 0.0	$ 0.0