Investments (Securities Lending and Repurchase Agreements Remaining Tenor) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	$ 7,421	$ 7,043
U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	7,421	7,043
Open (1) \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	995	971
1 Month or Less \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,399	2,445
Over 1 Month to 6 Months \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,027	3,627
Over 6 Months to 1 Year \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
Repurchase Agreements
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,075	2,975
Repurchase Agreements \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,075	2,975
Repurchase Agreements \| Open (1) \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
Repurchase Agreements \| 1 Month or Less \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,075	2,975
Repurchase Agreements \| Over 1 Month to 6 Months \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
Repurchase Agreements \| Over 6 Months to 1 Year \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	$ 0	$ 0