CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Assets
Common equity securities, at fair value	$ 630.8	$ 538.4
Other long-term investments	2,022.4	1,998.2
Goodwill and other intangible assets	731.0	370.6
Total assets	10,166.9	8,385.9
Liabilities
Debt	530.2	564.6
Total liabilities	5,294.7	3,824.3
White Mountains’s common shareholders’ equity
White Mountains’s common shares at $1 par value per share—authorized 50,000,000 shares; issued and outstanding 2,568,283 and 2,560,452 shares	2.6	2.6
Paid-in surplus	558.7	548.7
Retained earnings	3,863.1	3,690.8
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	(1.8)	(1.6)
Accumulated other comprehensive income (loss), after-tax:
Total White Mountains’s common shareholders’ equity	4,422.6	4,240.5
Noncontrolling interests	449.6	321.1
Total equity	4,872.2	4,561.6
Total liabilities and equity	10,166.9	8,385.9
Other Operations
Assets
Fixed maturity investments, at fair value	266.7	230.2
Common equity securities, at fair value	208.5	137.8
Investment in MediaAlpha, at fair value	235.2	254.9
Short-term investments, at fair value	192.3	425.2
Other long-term investments	624.0	661.0
Total investments	1,526.7	1,709.1
Cash	23.9	23.8
Insurance premiums receivable	21.7	0.0
Goodwill and other intangible assets	67.4	69.8
Other assets	77.1	73.2
Total assets	1,716.8	1,875.9
Liabilities
Loss and loss adjustment expense reserves	3.9	0.0
Unearned insurance premiums	22.6	0.0
Debt	24.7	28.4
Accrued incentive compensation	58.5	87.7
Other liabilities	31.1	25.0
Total liabilities	140.8	141.1
P&C Insurance and Reinsurance (Ark/WM Outrigger)
Liabilities
Loss and loss adjustment expense reserves	1,890.1	1,605.1
P&C Insurance and Reinsurance (Ark/WM Outrigger) | Operating Segments
Assets
Fixed maturity investments, at fair value	1,005.5	866.8
Common equity securities, at fair value	422.3	400.6
Short-term investments, at fair value	904.5	962.8
Other long-term investments	491.3	440.9
Total investments	2,823.6	2,671.1
Cash	156.3	90.5
Reinsurance recoverables	863.8	442.0
Insurance premiums receivable	1,175.4	612.2
Deferred acquisition costs	245.3	145.3
Goodwill and other intangible assets	292.5	292.5
Other assets	147.0	125.0
Total assets	5,703.9	4,378.6
Liabilities
Loss and loss adjustment expense reserves	1,890.1	1,605.1
Unearned insurance premiums	1,526.1	743.6
Debt	155.0	185.5
Reinsurance payable	367.3	81.1
Contingent consideration	107.3	94.0
Other liabilities	157.2	166.8
Total liabilities	4,203.0	2,876.1
Financial Guarantee (HG Global/BAM) | Operating Segments
Assets
Fixed maturity investments, at fair value	1,039.4	1,012.3
Short-term investments, at fair value	51.3	70.6
Total investments	1,090.7	1,082.9
Cash	5.0	6.7
Insurance premiums receivable	6.4	5.5
Deferred acquisition costs	41.7	40.1
Other assets	36.3	36.8
Total assets	1,180.1	1,172.0
Liabilities
Unearned insurance premiums	333.2	325.8
Debt	147.2	146.9
Accrued incentive compensation	17.3	27.2
Other liabilities	34.8	31.8
Total liabilities	532.5	531.7
Asset Management (Kudu) | Operating Segments
Assets
Short-term investments, at fair value	37.6	29.3
Other long-term investments	907.1	896.3
Total investments	944.7	925.6
Cash	1.1	1.4
Accrued investment income	15.1	17.6
Goodwill and other intangible assets	8.1	8.3
Other assets	35.4	6.5
Total assets	1,004.4	959.4
Liabilities
Debt	203.3	203.8
Other liabilities	67.9	71.6
Total liabilities	271.2	275.4
P&C Insurance Distribution (Bamboo) | Operating Segments
Assets
Fixed maturity investments, at fair value	33.2	0.0
Short-term investments, at fair value	19.8	0.0
Total investments	53.0	0.0
Cash	68.9	0.0
Premiums, commissions and fees receivable	58.0	0.0
Goodwill and other intangible assets	363.0	0.0
Other assets	18.8	0.0
Total assets	561.7	0.0
Liabilities
Loss and loss adjustment expense reserves	16.6	0.0
Unearned insurance premiums	23.6	0.0
Premiums and commissions payable	78.8	0.0
Other liabilities	28.2	0.0
Total liabilities	$ 147.2	$ 0.0