Segment Information (Tables)

12 Months Ended

Dec. 31, 2024

Segment Reporting [Abstract]

Schedule of financial information for segments

The following tables present White Mountains’s pre-tax financial results by segment for the years ended December 31, 2024, 2023 and 2022:

	Ark/WM Outrigger					HG Global
Millions	Ark			WM Outrigger Re		HG Global		BAM (1)(2)		Kudu		Bamboo		Other Operations		Total
Year Ended December 31, 2024
Earned insurance premiums	$	1,499.8		$	88.0	$	28.9	$	2.8	$	—	$	39.4	$	32.7	$	1,691.6
Net investment income (3)	79.4			11.3		23.4		8.8		66.7		2.2		35.6		227.4
Net realized and unrealized investment gains (losses) (3)	50.1			—		(6.4)		(5.1)		51.3		—		57.0		146.9
Net realized and unrealized investment gains    (losses) from investment in MediaAlpha	—			—		—		—		—		—		38.0		38.0
Interest income (expense) from BAM Surplus Notes	—			—		29.0		(13.2)		—		—		—		15.8
Change in fair value of BAM Surplus Notes	—			—		.5		—		—		—		—		.5
Unrealized loss on deconsolidation of BAM	—			—		(114.5)		—		—		—		—		(114.5)
Commission and fee revenues	—			—		—		—		—		134.6		14.8		149.4
Other revenues	22.3			—		.1		1.1		.8		3.6		56.8		84.7
Total revenues	1,651.6			99.3		(39.0)		(5.6)		118.8		179.8		234.9		2,239.8
Loss and loss adjustment expenses	825.9			29.9		—		—		—		20.6		12.1		888.5
Acquisition expenses	283.9			23.2		7.8		.4		—		14.1		12.1		341.5
Cost of sales	—			—		—		—		—		—		29.6		29.6
Broker commission expenses	—		—	—		—		—		—		51.3		—		51.3
General and administrative expenses (4) (5)	208.3			.1		2.2		33.5		15.4		61.1		169.5		490.1
Change in fair value of contingent consideration	61.3			—		—		—		—		—		—		61.3
Interest expense	19.5			—		16.7		—		22.1		—		2.5		60.8
Total expenses	1,398.9			53.2		26.7		33.9		37.5		147.1		225.8		1,923.1
Pre-tax income (loss)	$	252.7		$	46.1	$	(65.7)	$	(39.5)	$	81.3	$	32.7	$	9.1	$	316.7

(1) Effective July 1, 2024, White Mountains no longer consolidates BAM. For the period from January 1, 2024 through June 30, 2024, BAM’s results of operations are presented within the HG Global segment.

(2) BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.

(3) Bamboo’s net investment income and net realized and unrealized investment gains (losses) are included in other revenues in the consolidated statement of operations.

(4) Ark’s general and administrative expenses include $136.1 of other underwriting expenses.

(5) Bamboo’s general and administrative expenses include $16.4 of amortization of other intangible assets.

	Ark/WM Outrigger				HG Global						Other Operations
Millions	Ark		WM Outrigger Re		HG Global		BAM (1)		Kudu				Total
Year Ended December 31, 2023
Earned insurance premiums	$	1,305.4	$	104.3	$	26.0	$	5.2	$	—	$	—	$	1,440.9
Net investment income	50.4		11.0		17.1		14.6		71.0		30.1		194.2
Net realized and unrealized investment gains (losses)	85.9		—		13.6		13.0		106.1		188.5		407.1
Net realized and unrealized investment gains    (losses) from investment in MediaAlpha	—		—		—		—		—		27.1		27.1
Interest income (expense) from BAM Surplus Notes	—		—		26.2		(26.2)		—		—		—
Commission and fee revenues	—		—		—		—		—		13.2		13.2
Other revenues	.8		—		—		2.9		—		80.5		84.2
Total revenues	1,442.5		115.3		82.9		9.5		177.1		339.4		2,166.7
Losses and loss adjustment expenses	711.2		15.6		—		—		—		—		726.8
Acquisition expenses	251.0		30.5		7.4		1.2		—		—		290.1
Cost of sales	—		—		—		—		—		40.4		40.4
General and administrative expenses (2)	161.7		.3		2.8		66.1		19.4		182.3		432.6
Change in fair value of contingent consideration	48.7		—		—		—		—		—		48.7
Interest expense	21.3		—		16.5		—		21.2		3.7		62.7
Total expenses	1,193.9		46.4		26.7		67.3		40.6		226.4		1,601.3
Pre-tax income (loss)	$	248.6	$	68.9	$	56.2	$	(57.8)	$	136.5	$	113.0	$	565.4

(1) BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.

(2) Ark’s general and administrative expenses include $113.6 of other underwriting expenses.

	Ark/WM Outrigger		HG Global						Other Operations
Millions	Ark		HG Global		BAM (1)		Kudu				Total
Year Ended December 31, 2022
Earned insurance premiums	$	1,043.4	$	27.5	$	5.8	$	—	$	—	$	1,076.7
Net investment income	16.3		10.3		11.2		54.4		32.2		124.4
Net realized and unrealized investment gains (losses)	(55.2)		(52.5)		(53.3)		64.1		(1.6)		(98.5)
Net realized and unrealized investment gains    (losses) from investment in MediaAlpha	—		—		—		—		(93.0)		(93.0)
Interest income (expense) from BAM Surplus Notes	—		11.7		(11.7)		—		—		—
Commission and fee revenues	—		—		—		—		11.5		11.5
Other revenues	5.0		.5		4.1		—		127.2		136.8
Total revenues	1,009.5		(2.5)		(43.9)		118.5		76.3		1,157.9
Loss and loss adjustment expenses	536.4		—		—		—		—		536.4
Acquisition expenses	239.4		9.3		1.9		—		—		250.6
Cost of sales	—		—		—		—		98.6		98.6
General and administrative expenses (2)	106.2		2.8		66.3		14.7		174.1		364.1
Change in fair value of contingent consideration	17.3		—		—		—		—		17.3
Interest expense	15.1		8.3		—		15.0		1.9		40.3
Total expenses	914.4		20.4		68.2		29.7		274.6		1,307.3
Pre-tax income (loss)	$	95.1	$	(22.9)	$	(112.1)	$	88.8	$	(198.3)	$	(149.4)

(1)    BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.

(2)    Ark’s general and administrative expenses includes $78.7 of other underwriting expenses.

The following tables present White Mountains’s revenues from external customers by country for the years ended December 31, 2024, 2023 and 2022:

	December 31, 2024
Millions	United States		United Kingdom		Bermuda		Other		Total
Earned insurance premiums	$	2.8	$	956.8	$	732.0	$	—	$	1,691.6
Commission and fee revenues	134.6		—		—		14.8		149.4
Other revenues (1)	55.8		—		—		—		55.8
Total	$	193.2	$	956.8	$	732.0	$	14.8	$	1,896.8

(1)    Amounts include revenues from external customers related to certain consolidated Other Operating Businesses.

	December 31, 2023
Millions	United States		United Kingdom		Bermuda		Other		Total
Earned insurance premiums	$	5.2	$	791.7	$	644.0	$	—	$	1,440.9
Commission and fee revenues	—		—		—		13.2		13.2
Other revenues (1)	69.0		—		—		—		69.0
Total	$	74.2	$	791.7	$	644.0	$	13.2	$	1,523.1

(1)    Amounts include revenues from external customers related to certain consolidated Other Operating Businesses.

	December 31, 2022
Millions	United States		United Kingdom		Bermuda		Other		Total
Earned insurance premiums	$	5.8	$	638.5	$	432.4	$	—	$	1,076.7
Commission and fee revenues	—		—		—		11.5		11.5
Other revenues (1)	124.0		—		—		—		124.0
Total	$	129.8	$	638.5	$	432.4	$	11.5	$	1,212.2

(1)    Amounts include revenues from external customers related to certain consolidated Other Operating Businesses.

The following table presents White Mountains’s balance sheet information by segment as of December 31, 2024 and 2023:

Millions Selected Balance Sheet Data	Ark/WM Outrigger		HG Global			Kudu		Bamboo		Other Operations			Total
December 31, 2024:
Total investments	$	3,139.7	$	667.6		$	1,041.9	$	58.0	$	1,570.4		$	6,477.6
Total assets	$	5,299.0	$	1,179.4		$	1,108.4	$	584.6	$	1,754.2	(1)	$	9,925.6
Total liabilities	$	3,664.8	$	464.1	(1)	$	316.7	$	167.7	$	181.3		$	4,794.6
Total White Mountains’s common    shareholders’ equity	$	1,223.8	$	728.7	(1)	$	664.1	$	303.3	$	1,563.8	(1)	$	4,483.7
Noncontrolling interests	$	410.4	$	(13.4)		$	127.6	$	113.6	$	9.1		$	647.3
December 31, 2023:
Total investments	$	2,671.1	$	1,082.9		$	925.6	$	—	$	1,709.1		$	6,388.7
Total assets	$	4,378.6	$	1,172.0	(2)	$	959.4	$	—	$	1,875.9	(1)	$	8,385.9
Total liabilities	$	2,876.1	$	531.7	(1)	$	275.4	$	—	$	141.1		$	3,824.3
Total White Mountains’s common    shareholders’ equity	$	1,165.6	$	779.3	(1)	$	570.2	$	—	$	1,725.4	(1)	$	4,240.5
Noncontrolling interests	$	336.9	$	(139.0)		$	113.8	$	—	$	9.4		$	321.1

(1) HG Global preferred dividends payable to White Mountains’s subsidiaries is eliminated in White Mountains’s consolidated financial statements. For segment reporting, the HG Global preferred dividends payable to White Mountains’s subsidiaries included within the HG Global segment are eliminated against the offsetting receivable included within Other Operations and therefore added back to White Mountains’s common shareholders’ equity within the HG Global segment. As of December 31, 2024 and 2023, the HG Global preferred dividends payable to White Mountains’s subsidiaries was $462.1 and $399.8.

(2) As of December 31, 2023, total assets in the HG Global segment reflected the elimination of $322.2 of BAM Surplus Notes issued to HG Global and its subsidiaries and $174.5 in accrued interest related to the BAM Surplus Notes.