Investments (Securities Lending and Repurchase Agreements Remaining Tenor) (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
U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	10,401	10,062
Foreign government
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	1,193	1,170
Agency RMBS
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	163	172
Open (1)
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,434	2,987
Open (1) | U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,434	2,987
Open (1) | Foreign government
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
Open (1) | Agency RMBS
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	4,650	5,771
1 Month or Less | U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,495	4,986
1 Month or Less | Foreign government
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	1,054	677
1 Month or Less | Agency RMBS
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	101	108
Over 1 Month to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,673	2,646
Over 1 Month to 6 Months | U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,472	2,089
Over 1 Month to 6 Months | Foreign government
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	139	493
Over 1 Month to 6 Months | Agency RMBS
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	62	64
Over 6 Months to 1 Year
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
Over 6 Months to 1 Year | U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
Over 6 Months to 1 Year | Foreign government
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
Over 6 Months to 1 Year | Agency RMBS
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	2,975	2,975
Repurchase Agreements | U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	2,975	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	2,975	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