Investments (Securities Lending and Repurchase Agreements Remaining Tenor) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	$ 7,868	$ 7,043
U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	7,868	7,043
Open (1) \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	1,283	971
1 Month or Less \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,170	2,445
Over 1 Month to 6 Months \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,415	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	3,275	2,975
Repurchase Agreements \| U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,275	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	3,275	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