White Mountains accounts for business combinations using the acquisition method. Under the acquisition method, White Mountains recognizes and measures the assets acquired, including other intangible assets, and liabilities assumed, including contingent consideration liabilities, at their estimated fair values as of the acquisition date. Goodwill represents the excess of the amount paid to acquire a business over the fair value of identifiable net assets at the acquisition date. The estimated acquisition date fair values, generally consisting of other intangible assets and contingent consideration liabilities, may be recorded at provisional amounts in circumstances where the information necessary to complete the acquisition accounting is not available at the reporting date. Any such provisional amounts are finalized as measurement period adjustments within one year of the acquisition date.

The following tables present the economic life, acquisition date fair value, accumulated amortization, impairments and net carrying value for goodwill and other intangible assets as of September 30, 2026 and December 31, 2025:


$ in Millions	Weighted Average Economic Life (in years)	September 30, 2026
		Acquisition Date Fair Value		Accumulated Amortization		Impairments (1)		Net Carrying Value
Goodwill:
Ark	N/A	$	116.8	$	—	$	—	$	116.8
Kudu	N/A	7.6		—		—		7.6
Distinguished	N/A	397.9		—		—		397.9
WTM Partners (2)	N/A	163.1		—		—		163.1
Other Operations	N/A	44.4		—		9.1		35.3
Total goodwill		729.8		—		9.1		720.7
Other intangible assets:
Ark
Underwriting capacity	N/A	175.7		—		—		175.7
Kudu
Trade names	7.0	2.2		2.2		—		—
Distinguished
Trade names	10.0	24.3		2.6		—		21.7
Agency relationships	8.0	127.9		17.5		—		110.4
Developed technology	5.0	36.6		7.9		—		28.7
Subtotal		188.8		28.0		—		160.8
WTM Partners (2)
Trade names	10.0	19.0		1.8		—		17.2
Customer relationships	8.4	92.0		9.6		—		82.4
Subtotal		111.0		11.4		—		99.6
Other Operations
Trade names	13.0	13.3		7.9		.2		5.2
Customer relationships	11.0	24.8		18.1		.3		6.4
Other	11.7	3.1		2.1		—		1.0
Subtotal		41.2		28.1		.5		12.6
Total other intangible assets		518.9		69.7		.5		448.7
Total goodwill and other intangible assets		$	1,248.7	$	69.7	$	9.6	$	1,169.4

(2) The relative fair values of goodwill and other intangible assets recognized in connection with the acquisitions of Basesix and Hawkeye Electric had not yet been finalized. See Note 2 — “Significant Transactions.”


$ in Millions	Weighted Average Economic Life (in years)	December 31, 2025
		Acquisition Date Fair Value		Accumulated Amortization		Impairments (1)		Net Carrying Value
Goodwill:
Ark	N/A	$	116.8	$	—	$	—	$	116.8
Kudu	N/A	7.6		—		—		7.6
Distinguished (2)	N/A	396.7		—		—		396.7
WTM Partners (2)	N/A	57.7		—		—		57.7
Other Operations	N/A	44.4		—		9.1		35.3
Total goodwill		623.2		—		9.1		614.1
Other intangible assets:
Ark
Underwriting capacity	N/A	175.7		—		—		175.7








Kudu
Trade names	7.0	2.2		2.1		—		.1
Distinguished (2)
Trade names	10.0	24.3		.8		—		23.5
Agency relationships	8.0	127.9		5.0		—		122.9
Developed technology	5.0	36.6		2.0		—		34.6
Subtotal		188.8		7.8		—		181.0
WTM Partners (2)
Trade names	10.0	9.1		.7		—		8.4
Customer relationships	7.0	28.5		3.1		—		25.4
Subtotal		37.6		3.8		—		33.8
Other Operations
Trade names	13.0	13.3		7.1		.2		6.0
Customer relationships	11.0	24.8		16.2		.3		8.3


Other	11.8	3.1		1.9		—		1.2
Subtotal		41.2		25.2		.5		15.5
Total other intangible assets		445.5		38.9		.5		406.1
Total goodwill and other intangible assets		$	1,068.7	$	38.9	$	9.6	$	1,020.2

(2) The relative fair values of goodwill and other intangible assets recognized in connection with the acquisitions of Distinguished and Enterprise Solutions had not yet been finalized. See Note 2 — “Significant Transactions.”


	Three Months Ended September 30,
	2026						2025
Millions	Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets		Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets
Beginning balance	$	795.9	$	387.8	$	1,183.7	$	534.6	$	270.8	$	805.4
Acquisition of businesses (1)	—		—		—		595.4		—		595.4
Attribution of acquisition date fair value estimates between goodwill and other intangible assets (2)	(73.4)		73.4		—		(37.7)		37.6		(.1)
Measurement period adjustments (3)	(1.8)		—		(1.8)		—		—		—

Amortization	—		(12.5)		(12.5)		—		(7.8)		(7.8)
Ending balance	$	720.7	$	448.7	$	1,169.4	$	1,092.3	$	300.6	$	1,392.9

(1) During the three months ended September 30, 2025, amounts relate to the acquisitions of Distinguished and Enterprise Solutions. All amounts related to Distinguished were reflected as goodwill as of September 30, 2025. See Note 2 — “Significant Transactions.”

(2) During the three months ended September 30, 2026, amounts relate to the acquisitions of Basesix and Hawkeye Electric. During the three months ended September 30, 2025, amounts relate to the acquisition of Enterprise Solutions. See Note 2 — “Significant Transactions.”

(3) Measurement period adjustments relate to updated information about acquisition date fair values of assets acquired and liabilities assumed. During the three months ended September 30, 2026, adjustments relate to the acquisitions of Basesix and Hawkeye Electric. See Note 2 — “Significant Transactions.”


	Nine Months Ended September 30,
	2026						2025
Millions	Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets		Goodwill		Other Intangible Assets		Total Goodwill and Other Intangible Assets
Beginning balance	$	614.1	$	406.1	$	1,020.2	$	439.2	$	281.1	$	720.3
Acquisitions of businesses (1)	180.6		—		180.6		690.8		—		690.8


Attribution of acquisition date fair value estimates between goodwill and other intangible assets (2)	(73.4)		73.4		—		(37.7)		37.6		(.1)
Measurement period adjustments (3)	(.6)		—		(.6)		—		—		—
Amortization	—		(30.8)		(30.8)		—		(18.1)		(18.1)
Ending balance	$	720.7	$	448.7	$	1,169.4	$	1,092.3	$	300.6	$	1,392.9

(1) During the nine months ended September 30, 2026, amounts relate to the acquisitions of Basesix and Hawkeye Electric. During the nine months ended September 30, 2025, amounts relate to the acquisitions of Distinguished and Enterprise Solutions. All amounts related to Distinguished were reflected as goodwill as of September 30, 2025. See Note 2 — “Significant Transactions.”

(2) During the nine months ended September 30, 2026, amounts relate to the acquisitions of Basesix and Hawkeye Electric. During the nine months ended September 30, 2025, amounts relate to the acquisition of Enterprise Solutions. See Note 2 — “Significant Transactions.”

(3) Measurement period adjustments relate to updated information about acquisition date fair values of assets acquired and liabilities assumed. During the nine months ended September 30, 2026, adjustments relate to the acquisitions of Distinguished, Basesix and Hawkeye Electric. See Note 2 — “Significant Transactions.”