Derivative Financial Instruments - Narrative (Details)	9 Months Ended
Sep. 30, 2026 USD ($) counterparty contract	Dec. 31, 2025 USD ($) contract
Derivative [Line Items]
Fair value hedging adjustments for hedged assets	$ 0	$ 0
Fair value hedging adjustments for hedged liabilities	$ 0	0
Counterparty, threshold not set to zero \| counterparty	1
All Counterparties Except Merrill Lynch
Derivative [Line Items]
Counterparties, collateral required threshold	0.00%
Call Option \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Collateral	$ 851,000,000	1,185,000,000
Net credit risk	37,000,000	34,000,000
Call Option \| Derivatives not designated as hedging instruments \| Location, Statement of Financial Position, Balance [Axis]: us-gaap:CashAndCashEquivalentsAtCarryingValue
Derivative [Line Items]
Collateral	586,000,000	928,000,000
Call Option \| Derivatives not designated as hedging instruments \| Location, Statement of Financial Position, Balance [Axis]: us-gaap:PrepaidExpenseAndOtherAssets
Derivative [Line Items]
Collateral	$ 27,000,000	$ 0
Futures contracts
Derivative [Line Items]
Number of instruments held \| contract	320	172
Collateral held	$ 7,000,000	$ 4,000,000

Derivatives, Collateral, Net Exposure Threshold for Which Collateral Required

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- Definition

Number Of Counterparties, Derivatives, Collateral, Net Exposure Threshold Not Set to Zero

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- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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- Definition

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

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- Definition

Fair value, after effect of master netting arrangement and deduction of obligation to return financial collateral not offset and financial instrument subject to master netting arrangement not offset, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and contract can be net settled by means outside contract or delivery of asset. Includes derivative not subject to master netting arrangement or similar agreement.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The number of derivative instruments of a particular group held by the entity.

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, remaining after discontinued hedge. Excludes cumulative basis adjustment related to foreign exchange risk.

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Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk, remaining after discontinued hedge. Excludes cumulative basis adjustment related to foreign exchange risk.

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