Investments (Securities Lending Remaining Tenor) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	$ 3,210	$ 3,277
Remaining Tenor of Securities Lending Agreements: Open
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	490	647
Remaining Tenor of Securities Lending Agreements: 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	1,834	1,046
Remaining Tenor of Securities Lending Agreements: 1 to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	886	1,584
U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	2,843	2,886
U.S. government and agency | Remaining Tenor of Securities Lending Agreements: Open
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	490	647
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	1,467	655
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	886	1,584
U.S. corporate
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	248	252
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	248	252
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	105	130
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	105	130
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	14	9
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	14	9
Foreign government | Remaining Tenor of Securities Lending Agreements: 1 to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	$ 0	$ 0