Investments (Securities Lending and Repurchase Agreements) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	$ 11,757	$ 11,404
Reinvestment portfolio - estimated fair value	11,642	11,202
Estimated fair value
Securities Financing Transaction [Line Items]
Securities loaned	11,534	11,119
Securities Sold under Agreements to Repurchase	3,041	3,019
Repurchase Agreements
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	2,975	2,975
Reinvestment portfolio - estimated fair value	$ 2,934	$ 2,925

Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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+ Details