Investments (Securities Lending Remaining Tenor) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	$ 3,254	$ 3,210
Remaining Tenor of Securities Lending Agreements: Open
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	529	490
Remaining Tenor of Securities Lending Agreements: 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	1,533	1,834
Remaining Tenor of Securities Lending Agreements: 1 to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	1,192	886
U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	2,879	2,843
U.S. government and agency | Remaining Tenor of Securities Lending Agreements: Open
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	529	490
U.S. government and agency | Remaining Tenor of Securities Lending Agreements: 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	1,158	1,467
U.S. government and agency | Remaining Tenor of Securities Lending Agreements: 1 to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	1,192	886
U.S. corporate
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	217	248
U.S. corporate | Remaining Tenor of Securities Lending Agreements: Open
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	0	0
U.S. corporate | Remaining Tenor of Securities Lending Agreements: 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	217	248
U.S. corporate | Remaining Tenor of Securities Lending Agreements: 1 to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	0	0
Foreign corporate
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	142	105
Foreign corporate | Remaining Tenor of Securities Lending Agreements: Open
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	0	0
Foreign corporate | Remaining Tenor of Securities Lending Agreements: 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	142	105
Foreign corporate | Remaining Tenor of Securities Lending Agreements: 1 to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	0	0
Foreign government
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	16	14
Foreign government | Remaining Tenor of Securities Lending Agreements: Open
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	0	0
Foreign government | Remaining Tenor of Securities Lending Agreements: 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	16	14
Foreign government | Remaining Tenor of Securities Lending Agreements: 1 to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	$ 0	$ 0