Investment Securities

12 Months Ended

Dec. 31, 2025

Investments, Debt and Equity Securities [Abstract]

Investment Securities

Investment Securities

White Mountains’s portfolio of investment securities held for general investment purposes consists of fixed maturity investments, short-term investments, common equity securities, its investment in MediaAlpha and other long-term investments. White Mountains’s portfolio of fixed maturity investments, including those within short-term investments, is classified as trading securities. Trading securities are reported at fair value as of the balance sheet date. Short-term investments also include interest-bearing money market funds and certificates of deposit that are carried at fair value. White Mountains’s portfolio of common equity securities, its investment in MediaAlpha and other long-term investments are measured at fair value. Other long-term investments consist primarily of unconsolidated entities, including Kudu’s Participation Contracts, the Bamboo SPV, PassportCard/DavidShield and the BroadStreet SPV, as well as private equity funds and hedge funds, a bank loan fund and Lloyd’s trust deposits. White Mountains has generally taken the fair value option for its equity method eligible investments. See Note 17 — “Equity Method Eligible Investments.” Net realized and unrealized investment gains (losses) are reported in pre-tax revenues.

Effective December 5, 2025, White Mountains no longer consolidates Bamboo. Through December 5, 2025, White Mountains’s consolidated financial statements included Bamboo’s investment results. Effective July 1, 2024, White Mountains no longer consolidates BAM. Through June 30, 2024, White Mountains’s consolidated financial statements included BAM’s investment results. See Note 2 — “Significant Transactions.”

White Mountains’s portfolio of investment securities includes investments classified as assets held for sale. See Note 20 — “Held for Sale.”

Net Investment Income

White Mountains’s net investment income is comprised primarily of interest income associated with White Mountains’s fixed maturity investments and short-term investments, dividend income from common equity securities and distributions from other long-term investments.

The following table presents pre-tax net investment income for the years ended December 31, 2025, 2024 and 2023:

	Year Ended December 31,
Millions	2025		2024		2023
Fixed maturity investments	$	111.8	$	93.2	$	64.4
Short-term investments	47.8		56.6		52.0
Common equity securities	.6		2.5		4.1
Other long-term investments	90.4		77.9		76.1
Total investment income	250.6		230.2		196.6
Third-party investment expenses	(2.6)		(2.8)		(2.4)
Net investment income, pre-tax	$	248.0	$	227.4	$	194.2

Net Realized and Unrealized Investment Gains (Losses)

The following table presents net realized and unrealized investment gains (losses) for the years ended December 31, 2025, 2024 and 2023:

	Year Ended December 31,
Millions	2025		2024		2023
Realized investment gains (losses)
Fixed maturity investments	$	.8	$	(10.1)	$	(4.7)
Short-term investments	.5		(1.2)		(.2)
Common equity securities	67.7		3.5		29.5
Investment in MediaAlpha	—		91.2		—
Other long-term investments	42.5		34.6		72.2
Net realized investment gains (losses)	111.5		118.0		96.8
Unrealized investment gains (losses)
Fixed maturity investments	53.9		3.9		66.1
Short-term investments	.5		(.8)		1.9
Common equity securities	(14.2)		58.1		47.1
Investment in MediaAlpha	29.6		(53.2)		27.1
Other long-term investments	180.2		58.9		195.2
Net unrealized investment gains (losses)	250.0		66.9		337.4
Net realized and unrealized investment gains (losses) (1)	$	361.5	$	184.9	$	434.2
Fixed maturity and short-term investments
Net realized and unrealized investment gains (losses)	$	55.7	$	(8.2)	$	63.1
Less: net realized and unrealized gains (losses) on investment    securities sold during the period	5.7		.9		4.7
Net unrealized investment gains (losses) recognized during the    period on investment securities held at the end of the period	$	50.0	$	(9.1)	$	58.4
Common equity securities and investment in MediaAlpha
Net realized and unrealized investment gains (losses) on    common equity securities	$	53.5	$	61.6	$	76.6
Net realized and unrealized investment gains (losses) from    investment in MediaAlpha	29.6		38.0		27.1
Total net realized and unrealized investment gains (losses)	83.1		99.6		103.7
Less: net realized and unrealized gains (losses) on investment    securities sold during the period	6.4		35.4		28.4
Net unrealized investment gains (losses) recognized during the    period on investment securities held at the end of the period	$	76.7	$	64.2	$	75.3

(1) For 2025, 2024 and 2023, includes $37.1, $(31.5) and $13.6 of net realized and unrealized investment gains (losses) related to foreign currency exchange.

For the years ended December 31, 2025, 2024 and 2023, all of White Mountains’s net realized and unrealized investment gains (losses) were recorded in the consolidated statements of operations. There were no investment gains (losses) recorded in other comprehensive income.

White Mountains recognized gross realized investment gains of $117.1 million, $139.1 million and $113.7 million and gross realized investment losses of $5.6 million, $21.1 million and $16.9 million on sales of investment securities for the years ending December 31, 2025, 2024 and 2023.

The following table presents total net unrealized gains (losses) attributable to Level 3 investments for the years ended December 31, 2025, 2024 and 2023 for investments still held at the end of the period:

	Year Ended December 31,
Millions	2025		2024		2023
Total net unrealized investment gains recognized during the period on    Level 3 investments held at the end of period	$	127.7	$	57.2	$	133.9

Proceeds from the sales and maturities of investments, excluding short-term investments, totaled $1.4 billion, $1.2 billion and $0.8 billion for the years ended December 31, 2025, 2024 and 2023.

Investment Holdings

The following tables present the cost or amortized cost, gross unrealized investment gains (losses), net foreign currency gains (losses) and carrying value of White Mountains’s fixed maturity investments as of December 31, 2025 and 2024:

	December 31, 2025
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
U.S. Government and agency obligations	$	459.7	$	1.3	$	(.7)	$	—	$	460.3
Debt securities issued by corporations	1,534.9		13.5		(11.5)		.8		1,537.7
Mortgage and asset-backed securities	405.1		4.2		(16.3)		—		393.0
Collateralized loan obligations	343.9		.8		(.1)		2.4		347.0
Foreign government and agency obligations	31.2		—		(.1)		1.4		32.5
Total fixed maturity investments	$	2,774.8	$	19.8	$	(28.7)	$	4.6	$	2,770.5

	December 31, 2024
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
U.S. Government and agency obligations	$	461.8	$	1.1	$	(.8)	$	—	$	462.1
Debt securities issued by corporations	1,444.5		4.6		(31.4)		(3.5)		1,414.2
Municipal obligations	3.2		—		—		—		3.2
Mortgage and asset-backed securities	400.2		.2		(26.5)		—		373.9
Collateralized loan obligations	237.3		1.2		(.2)		(1.6)		236.7
Foreign government and agency obligations	22.2		—		(.1)		(.6)		21.5
Total fixed maturity investments	$	2,569.2	$	7.1	$	(59.0)	$	(5.7)	$	2,511.6

The weighted average duration of White Mountains’s fixed income portfolio, including short-term investments, was 1.5 years and 1.9 years as of December 31, 2025 and 2024. Excluding short-term investments, the weighted average duration of White Mountains’s fixed income portfolio was 2.5 years and 2.6 years as of December 31, 2025 and 2024.

The following table presents the cost or amortized cost and carrying value of White Mountains’s fixed maturity investments by contractual maturity as of December 31, 2025 and 2024. Actual maturities could differ from contractual maturities because borrowers may have the right to call or prepay certain obligations with or without penalties.

	December 31, 2025				December 31, 2024
Millions	Cost or Amortized Cost		Carrying Value		Cost or Amortized Cost		Carrying Value
Due in one year or less	$	455.3	$	455.2	$	205.8	$	203.9
Due after one year through five years	1,349.8		1,354.1		1,494.5		1,478.7
Due after five years through ten years	199.0		199.3		206.1		193.2
Due after ten years	21.7		21.9		25.3		25.2
Mortgage and asset-backed securities and    collateralized loan obligations	749.0		740.0		637.5		610.6
Total fixed maturity investments	$	2,774.8	$	2,770.5	$	2,569.2	$	2,511.6

The following tables present the cost or amortized cost, gross unrealized investment gains (losses), net foreign currency gains (losses) and carrying value of common equity securities, White Mountains’s investment in MediaAlpha and other long-term investments as of December 31, 2025 and 2024:

	December 31, 2025
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
Common equity securities	$	384.3	$	99.9	$	—	$	(1.2)	$	483.0
Investment in MediaAlpha	$	59.2	$	172.0	$	—	$	—	$	231.2
Other long-term investments	$	2,378.8	$	712.6	$	(123.1)	$	(9.8)	$	2,958.5

	December 31, 2024
Millions	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Net Foreign Currency Gains (Losses)		Carrying Value
Common equity securities	$	537.0	$	120.4	$	—	$	(7.4)	$	650.0
Investment in MediaAlpha	$	59.2	$	142.4	$	—	$	—	$	201.6
Other long-term investments	$	1,748.7	$	546.4	$	(116.7)	$	(28.2)	$	2,150.2

Fair Value Measurements by Level

The following tables present White Mountains’s fair value measurements for investments as of December 31, 2025 and 2024 by level. See Note 1 — “Basis of Presentation and Significant Accounting Policies.” The major security types were based on the legal form of the securities. White Mountains has disaggregated its fixed maturity investments based on the issuing entity type, which impacts credit quality, with debt securities issued by U.S. government entities carrying minimal credit risk, while the credit and other risks associated with other issuers, such as corporations, foreign governments and agencies, municipalities, entities issuing mortgage and asset-backed securities or entities issuing collateralized loan obligations vary depending on the nature of the issuing entity type. White Mountains further disaggregates debt securities issued by corporations by industry sector because investors often reference commonly used benchmarks and their subsectors to monitor risk and performance. Accordingly, White Mountains has further disaggregated this asset class into subclasses based on the similar sectors and industry classifications it uses to evaluate investment risk and performance against commonly used benchmarks, such as the Bloomberg U.S. Intermediate Aggregate Index.

	December 31, 2025
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	460.3	$	460.3	$	—	$	—
Debt securities issued by corporations:
Financials	531.5		—		531.5		—
Consumer	306.2		—		306.2		—
Industrial	150.0		—		150.0		—
Healthcare	146.1		—		146.1		—
Technology	98.4		—		98.4		—
Utilities	90.4		—		90.4		—
Materials	78.7		—		78.7		—
Communications	76.3		—		76.3		—
Energy	60.1		—		60.1		—
Total debt securities issued by corporations	1,537.7		—		1,537.7		—
Mortgage and asset-backed securities	393.0		—		393.0		—
Collateralized loan obligations	347.0		—		347.0		—
Foreign government and agency obligations	32.5		—		32.5		—
Total fixed maturity investments	2,770.5		460.3		2,310.2		—
Short-term investments	1,881.7		1,871.7		10.0		—
Common equity securities:
Exchange-traded funds	30.7		30.7		—		—
Other (1)	452.3		—		452.3		—
Total common equity securities	483.0		30.7		452.3		—
Investment in MediaAlpha	231.2		231.2		—		—
Other long-term investments	1,848.1		—		33.7		1,814.4
Other long-term investments — NAV (2)	1,110.4		—		—		—
Total other long-term investments	2,958.5		—		33.7		1,814.4
Total investments	$	8,324.9	$	2,593.9	$	2,806.2	$	1,814.4

(1) Consists of investments in listed funds that predominantly invest in international equities.

(2) Consists of investments in the BroadStreet SPV, private equity funds and hedge funds, a bank loan fund, Lloyd’s trust deposits and ILS funds for which fair value is measured using NAV as a practical expedient. Investments for which fair value is measured at NAV are not classified within the fair value hierarchy.

	December 31, 2024
Millions	Fair Value		Level 1		Level 2		Level 3
Fixed maturity investments:
U.S. Government and agency obligations	$	462.1	$	461.3	$	.8	$	—
Debt securities issued by corporations:
Financials	466.7		—		466.7		—
Consumer	255.2		—		255.2		—
Industrial	164.4		—		164.4		—
Healthcare	153.1		—		153.1		—
Technology	113.8		—		113.8		—
Utilities	60.9		—		60.9		—
Materials	65.7		—		65.7		—
Communications	71.6		—		71.6		—
Energy	62.8		—		62.8		—
Total debt securities issued by corporations	1,414.2		—		1,414.2		—
Municipal obligations	3.2		—		3.2		—
Mortgage and asset-backed securities	373.9		—		373.9		—
Collateralized loan obligations	236.7		—		236.7		—
Foreign government and agency obligations	21.5		—		21.5		—
Total fixed maturity investments	2,511.6		461.3		2,050.3		—
Short-term investments	964.2		951.1		13.1		—
Common equity securities:
Exchange-traded funds	224.6		224.6		—		—
Other (1)	425.4		—		425.4		—
Total common equity securities	650.0		224.6		425.4		—
Investment in MediaAlpha	201.6		201.6		—		—
Other long-term investments	1,286.2		—		23.5		1,262.7
Other long-term investments — NAV (2)	864.0		—		—		—
Total other long-term investments	2,150.2		—		23.5		1,262.7
Total investments	$	6,477.6	$	1,838.6	$	2,512.3	$	1,262.7

(1) Consists of investments in listed funds that predominantly invest in international equities.

(2) Consists of investments in private equity funds and hedge funds, a bank loan fund, Lloyd’s trust deposits and ILS funds for which fair value is measured using NAV as a practical expedient. Investments for which fair value is measured at NAV are not classified within the fair value hierarchy.

Investments Held on Deposit or as Collateral

Lloyd’s trust deposits are generally required of Lloyd's syndicates to protect policyholders in non-U.K. markets and are pledged into Lloyd’s trust accounts to provide a portion of the capital needed to support obligations at Lloyd’s. As of December 31, 2025 and 2024, Ark held Lloyd’s trust deposits with a fair value of $180.4 million and $149.9 million.

The underwriting capacity of a member of Lloyd’s must be supported by providing a deposit (“Funds at Lloyd’s”) in the form of cash, securities or letters of credit in an amount determined by Lloyd’s. The amount of such deposit is calculated for each member through an annual capital adequacy determination by Lloyd’s. As of December 31, 2025 and 2024, the fair value of Ark’s Funds at Lloyd’s cash and investment deposits totaled $361.6 million and $361.5 million.

As of December 31, 2025 and 2024, Ark held additional investments on deposit or as collateral for insurance regulators and reinsurance counterparties of $257.2 million and $226.5 million.

As of December 31, 2025 and 2024, investments of $245.7 million and $203.7 million were held in a collateral trust account required to be maintained in relation to WM Outrigger Re’s reinsurance agreement with GAIL.

Ark is required to pledge collateral under its standby letters of credit. See Note 7 — “Debt.”

HG Re is required to maintain assets, including investments, in collateral trusts under the FLRT with BAM. See Note 10 — “Municipal Bond Guarantee Reinsurance - Collateral Trusts.”

HG Global is required to maintain an interest reserve account in connection with its senior notes issued in 2022. See Note 7 — “Debt.”

Kudu is required to maintain an interest reserve account in connection with its credit facility. See Note 7 - “Debt.”

As of December 31, 2024, investments of $32.2 million were held as collateral required to be maintained in relation to the Bamboo Captive’s reinsurance agreements.

As of December 31, 2025 and 2024, investments of $25.7 million and $46.7 million were held as collateral required to be maintained in relation to the Bamboo CRVs’ reinsurance agreements.

As of December 31, 2025, investments of $56.8 million were held on deposit, primarily related to amounts held on behalf of Distinguished’s insurance carrier partners and certain insureds.

Debt Securities Issued by Corporations

The following table presents the fair values for credit ratings of debt securities issued by corporations held in White Mountains’s investment portfolio as of December 31, 2025 and 2024:

	December 31,
Millions	2025		2024
AAA	$	7.8	$	14.6
AA	89.9		91.2
A	711.7		607.2
BBB	716.9		688.7
BB	3.2		5.4
Other	8.2		7.1
Debt securities issued by corporations (1)	$	1,537.7	$	1,414.2

(1) Credit ratings are based upon issuer credit ratings provided by Standard & Poor’s Financial Services LLC (“Standard & Poor’s”), or if unrated by Standard & Poor’s, long-term obligation ratings provided by Moody’s Investor Service, Inc.

Mortgage and Asset-backed Securities and Collateralized Loan Obligations

The following table presents the fair value of White Mountains’s mortgage and asset-backed securities and collateralized loan obligations as of December 31, 2025 and 2024:

	December 31, 2025						December 31, 2024
Millions	Fair Value		Level 2		Level 3		Fair Value		Level 2		Level 3
Mortgage-backed securities:
Agency:
FNMA	$	192.1	$	192.1	$	—	$	198.3	$	198.3	$	—
FHLMC	141.3		141.3		—		147.1		147.1		—
GNMA	20.6		20.6		—		24.2		24.2		—
Total agency (1)	354.0		354.0		—		369.6		369.6		—
Non-agency: Commercial	—		—		—		.4		.4		—
Total non-agency	—		—		—		.4		.4		—
Total mortgage-backed securities	354.0		354.0		—		370.0		370.0		—
Other asset-backed securities:
Vehicle receivables	21.9		21.9		—		1.7		1.7		—
Credit card receivables	14.0		14.0		—		.2		.2		—
Other	3.1		3.1		—		2.0		2.0		—
Total other asset-backed securities	39.0		39.0		—		3.9		3.9		—
Total mortgage and asset-backed securities	393.0		393.0		—		373.9		373.9		—
Collateralized loan obligations	347.0		347.0		—		236.7		236.7		—
Total mortgage and asset-backed securities and    collateralized loan obligations	$	740.0	$	740.0	$	—	$	610.6	$	610.6	$	—

(1) Represents publicly traded mortgage-backed securities which carry the full faith and credit guarantee of the U.S. Government (i.e., GNMA) or are guaranteed by a government sponsored entity (i.e., FNMA, FHLMC).

As of December 31, 2025 and 2024, White Mountains’s investment portfolio included $347.0 million and $236.7 million of collateralized loan obligations that are within the senior tranches of their respective fund securitization structures. All of White Mountains’s collateral loan obligations were rated AAA or AA as of December 31, 2025 and 2024.

Investment in MediaAlpha

White Mountains’s investment in MediaAlpha is accounted for at fair value based on the publicly traded share price of MediaAlpha’s common stock and is presented as a separate line item on the balance sheet.

During the second quarter of 2024, MediaAlpha completed a secondary offering of 7.6 million shares at $19.00 per share ($18.24 per share net of underwriting fees). In the secondary offering, White Mountains sold 5.0 million shares for net proceeds of $91.2 million. During the second quarter of 2023, White Mountains completed a tender offer to purchase 5.9 million additional shares of MediaAlpha at a purchase price of $10.00 per share.

As of December 31, 2025, White Mountains owned 17.9 million shares of MediaAlpha, representing a 27.4% basic ownership interest based on the total class A and class B common shares outstanding in MediaAlpha’s Report on Form 10-Q dated October 29, 2025. At White Mountains’s December 31, 2025 level of ownership, each $1.00 per share increase or decrease in the share price of MediaAlpha will result in an approximate $7.00 per share increase or decrease in White Mountains’s book value per share. At the December 31, 2025 share price of $12.95, the fair value of White Mountains’s investment in MediaAlpha was $231.2 million. As of December 31, 2024, White Mountains owned 17.9 million shares of MediaAlpha, representing a 26.6% basic ownership interest. At the December 31, 2024 share price of $11.29, the fair value of White Mountains’s investment in MediaAlpha was $201.6 million.

Other Long-Term Investments

The following tables present the carrying values of White Mountains’s other long-term investments by reportable segment as of December 31, 2025 and 2024:

	Fair Value as of December 31, 2025
Millions	Ark/WM Outrigger		Kudu		Other		Total
Kudu’s Participation Contracts	$	—	$	1,285.0	$	—	$	1,285.0
Bamboo SPV	—		—		250.0		250.0
PassportCard/DavidShield	—		—		170.0		170.0
BroadStreet SPV	—		—		160.0		160.0
Elementum	—		—		35.0		35.0
Other unconsolidated entities (1)	—		—		73.7		73.7
Total unconsolidated entities	—		1,285.0		688.7		1,973.7
Private equity funds and hedge funds	167.1		—		228.1		395.2
Bank loan fund	308.5		—		—		308.5
Lloyd’s trust deposits	180.4		—		—		180.4
ILS funds	—		—		50.1		50.1
Private debt instruments	—		6.4		10.5		16.9
Other	33.7		—		—		33.7
Total other long-term investments	$	689.7	$	1,291.4	$	977.4	$	2,958.5

(1) Includes White Mountains’s noncontrolling equity interests in certain preferred securities, private equity securities and limited liability company units.

	Fair Value as of December 31, 2024
Millions	Ark/WM Outrigger		Kudu		Other		Total
Kudu’s Participation Contracts	$	—	$	1,008.4	$	—	$	1,008.4
PassportCard/DavidShield	—		—		150.0		150.0
Elementum	—		—		35.0		35.0
Other unconsolidated entities (1)	—		—		63.6		63.6
Total unconsolidated entities	—		1,008.4		248.6		1,257.0
Private equity funds and hedge funds	104.1		—		256.5		360.6
Bank loan fund	264.7		—		—		264.7
Lloyd’s trust deposits	149.9		—		—		149.9
ILS funds	—		—		74.0		74.0
Private debt instruments	—		5.6		9.3		14.9
Other	29.1		—		—		29.1
Total other long-term investments	$	547.8	$	1,014.0	$	588.4	$	2,150.2

(1) Includes White Mountains’s noncontrolling equity interests in certain preferred securities, limited liability company units, limited partnership units and Simple Agreement for Future Equity (“SAFE”) investments.

Private Equity Funds and Hedge Funds

White Mountains invests in private equity funds and hedge funds, which are included in other long-term investments. The fair value of these investments is generally estimated using the NAV of the funds. As of December 31, 2025, White Mountains held investments in seventeen private equity funds and two hedge funds.  The largest investment in a single private equity fund or hedge fund was $110.6 million and $59.2 million as of December 31, 2025 and 2024.

The following table presents the fair value of investments and unfunded commitments in private equity funds and hedge funds by investment objective and sector as of December 31, 2025 and 2024:

	December 31, 2025				December 31, 2024
Millions	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments
Private equity funds
Aerospace/Defense/Government	$	144.0	$	39.9	$	152.4	$	49.3
Financial services	104.2		23.7		93.4		32.0
Real estate	3.0		2.2		3.7		2.4
Total private equity funds	251.2		65.8		249.5		83.7
Hedge funds
Long/short all cap global	110.6		—		51.9		—
Long/short equity financials and business services	33.4		—		59.2		—
Total hedge funds	144.0		—		111.1		—
Total private equity funds and hedge funds	$	395.2	$	65.8	$	360.6	$	83.7

Investments in private equity funds are generally subject to a lock-up period during which investors may not request a redemption. Distributions prior to the expected termination date of the fund may be limited to dividends or proceeds arising from the liquidation of the fund’s underlying investments. In addition, certain private equity funds have the option to extend the lock-up period.

The following table presents investments in private equity funds that were subject to lock-up periods as of December 31, 2025:

Millions	1 – 3 years		3 – 5 years		5 – 10 years		>10 years		Total
Private equity funds — expected lock-up period remaining	$	57.2	$	8.0	$	161.7	$	24.3	$	251.2

Investors in private equity funds are generally subject to indemnification obligations outside of the capital commitment period and prior to the winding up of the fund. As of December 31, 2025 and 2024, White Mountains is not aware of any indemnification claims relating to its investments in private equity funds. 

Redemption of investments in most hedge funds is subject to restrictions, including lock-up periods where no redemptions or withdrawals are allowed, restrictions on redemption frequency and advance notice periods for redemptions. Amounts requested for redemptions remain subject to market fluctuations until the redemption effective date, which generally falls at the end of the defined redemption period. White Mountains’s hedge fund investments are subject to monthly and quarterly restrictions on redemptions and advance written redemption notice period requirements that range between 45 and 90 calendar days.

Bank Loan Fund

White Mountains’s other long-term investments include a bank loan fund with a fair value of $308.5 million and $264.7 million as of December 31, 2025 and 2024. The fair value of this investment is estimated using the NAV of the fund. The bank loan fund’s investment objective is to provide, on an unleveraged basis, high current income consistent with preservation of capital and low duration. The bank loan fund primarily invests in a broad portfolio of U.S. dollar-denominated, non-investment grade, floating-rate senior secured loans and may invest in other financial instruments, such as secured and unsecured corporate debt, credit default swaps, reverse repurchase agreements, synthetic indices and cash and cash equivalents.

The investment in the bank loan fund is subject to restrictions on redemption frequency and advance notice periods for redemptions. Amounts requested for redemptions remain subject to market fluctuations until the redemption effective date, which generally falls at the end of the defined redemption period. White Mountains may redeem all or a portion of its bank loan fund investment as of any calendar month-end upon 15 calendar days advanced written notice.

Lloyd’s Trust Deposits

White Mountains’s other long-term investments include Lloyd’s trust deposits, which consist of non-U.K. deposits and Canadian comingled pooled funds. The Lloyd’s trust deposits invest primarily in short-term government securities, agency securities and corporate bonds held in trusts that are managed by Lloyd's of London. These investments are generally required of Lloyd's syndicates to protect policyholders in non-U.K. markets and are pledged into Lloyd’s trust accounts to provide a portion of the capital needed to support obligations at Lloyd’s. The fair value of the Lloyd’s trust deposits is generally estimated using the NAV of the funds. As of December 31, 2025 and 2024, White Mountains held Lloyd’s trust deposits with a fair value of $180.4 million and $149.9 million.

ILS Funds

White Mountains’s other long-term investments include ILS fund investments. The fair value of these investments is generally estimated using the NAV of the funds. As of December 31, 2025 and 2024, White Mountains held investments in ILS funds with a fair value of $50.1 million and $74.0 million.

Investments in ILS funds are generally subject to restrictions, including lock-up periods where no redemptions or withdrawals are allowed, non-renewal clauses, restrictions on redemption frequency and advance notice periods for redemptions. From time to time, natural catastrophe, liquidity, market or other events will occur that make the determination of fair value for underlying investments in ILS funds less certain due to the potential for loss development. In such circumstances, the impacted investments may be subject to additional lock-up provisions.

ILS funds are typically subject to monthly and annual restrictions on redemptions and advance redemption notice period requirements that range between 30 and 90 calendar days. Amounts requested for redemption remain subject to market fluctuations until the redemption effective date, which is generally at the end of the defined redemption period or when the underlying investment has fully matured or been commuted.

Infrastructure Fund

In 2025, Ark made a $100.0 million commitment to invest in an open-ended pooled investment fund focused on making equity investments in essential service infrastructure assets. The fund has a 4-year lock-up period, subject to the discretion of the manager. Redemptions of all or a portion of the fund are allowable semi-annually with a 90-day written notice. Ark anticipates that the initial capital call will occur in the second quarter of 2026.

Rollforward of Level 3 Investments

Level 3 measurements as of December 31, 2025 and 2024 consist of securities for which the estimated fair value has not been determined based upon quoted market price inputs for identical or similar securities. The following table presents the changes in White Mountains’s fair value measurements for Level 3 investments for the years ended December 31, 2025 and 2024:

Level 3 Investments
Other Long-term Investments
Millions	December 31, 2025		December 31, 2024
Beginning balance	$	1,262.7	$	1,138.2
Net realized and unrealized gains	141.0		54.4
Purchases and contributions	202.2		111.5
Effect of Bamboo Sale Transaction (1)	250.0		—
Effect of Distinguished Transaction (1)	(7.1)		—
Sales and distributions	(34.4)		(41.4)
Transfers in	—		—
Transfers out	—		—
Ending balance	$	1,814.4	$	1,262.7

(1) See Note 2 — “Significant Transactions.”

Significant Unobservable Inputs

The following tables present significant unobservable inputs used in estimating the fair value of White Mountains’s other long-term investments, classified within Level 3 as of December 31, 2025 and 2024. The tables below exclude $250.4 million and $23.4 million of Level 3 other long-term investments generally valued based on recent or expected transaction prices. As of December 31, 2025, the Bamboo SPV was measured at fair value based on the value implied in the Bamboo Sale Transaction. See Note 2 — “Significant Transactions.” The fair value of investments in the BroadStreet SPV, private equity funds and hedge funds, bank loan funds, Lloyd’s trust deposits and ILS funds are generally estimated using NAV. Investments for which fair value is measured at NAV are not classified within the fair value hierarchy.

$ in Millions	December 31, 2025
Description	Valuation Technique(s) (1)	Fair Value (2)	Unobservable Inputs
			Discount Rate (5)	Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (5)
Kudu’s Participation Contracts (3) (4)	Discounted cash flow	$1,285.0	16% - 25%	7x - 22x
PassportCard/DavidShield	Discounted cash flow	$170.0	24%	4%
Elementum	Discounted cash flow	$35.0	22%	3%
Preferred securities	Discounted cash flow	$35.6	8%	N/A
Private equity securities	Discounted cash flow	$21.9	35%	4%
Private debt instruments	Discounted cash flow	$16.5	11% - 12%	N/A

(1) Key inputs to the discounted cash flow analysis generally include projections of future revenue and earnings, discount rates and terminal exit multiples or growth rates.

(2) Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.

(3) Since Kudu’s Participation Contracts are not subject to corporate taxes within Kudu Investment Management, LLC, pre-tax discount rates are applied to pre-tax cash flows in determining fair values. The weighted average discount rate and weighted average terminal cash flow exit multiple applied to Kudu’s Participation Contracts was 19% and 14x.

(4) In 2025, Kudu contributed $201.7 into new and existing Participation Contracts.

(5) Increases (decreases) to the discount rates in isolation would result in lower (higher) fair value measurements, while increases (decreases) to the terminal cash flow exit multiples or terminal revenue growth rates in isolation would result in higher (lower) fair value measurements.

$ in Millions	December 31, 2024
Description	Valuation Technique(s) (1)	Fair Value (2)	Unobservable Inputs
			Discount Rate (5)	Terminal Cash Flow Exit Multiple (x) or Terminal Revenue Growth Rate (%) (5)
Kudu’s Participation Contracts (3) (4)	Discounted cash flow	$1,008.4	17% - 25%	7x - 22x
PassportCard/DavidShield	Discounted cash flow	$150.0	24%	4%
Elementum	Discounted cash flow	$35.0	22%	4%
Preferred securities	Discounted cash flow	$31.4	9%	N/A
Private debt instruments	Discounted cash flow	$14.5	11% - 12%	N/A

(1) Key inputs to the discounted cash flow analysis generally include projections of future revenue and earnings, discount rates and terminal exit multiples or growth rates.

(2) Includes the net unrealized investment gains (losses) associated with foreign currency; foreign currency effects based on observable inputs.

(3) Since Kudu’s Participation Contracts are not subject to corporate taxes within Kudu Investment Management, LLC, pre-tax discount rates are applied to pre-tax cash flows in determining fair values. The weighted average discount rate and weighted average terminal cash flow exit multiple applied to Kudu’s Participation Contracts was 19% and 14x.

(4) In 2024, Kudu contributed $103.5 into new and existing Participation Contracts.

(5) Increases (decreases) to the discount rates in isolation would result in lower (higher) fair value measurements, while increases (decreases) to the terminal cash flow exit multiples or terminal revenue growth rates in isolation would result in higher (lower) fair value measurements.