Investments (Securities Lending and Repurchase Agreements Remaining Tenor) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	$ 10,617	$ 12,092
U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	9,311	10,494
Foreign government
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	1,034	1,344
Agency RMBS
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	272	254
Open (1)
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	1,934	1,945
Open (1) | U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	1,934	1,945
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	4,655	5,933
1 Month or Less | U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	4,288	5,448
1 Month or Less | Foreign government
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	194	422
1 Month or Less | Agency RMBS
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	173	63
Over 1 Month to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	4,028	4,214
Over 1 Month to 6 Months | U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,089	3,101
Over 1 Month to 6 Months | Foreign government
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	840	922
Over 1 Month to 6 Months | Agency RMBS
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	99	191
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	3,125
Repurchase Agreements | U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	2,975	3,125
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	3,125
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