Investments (Securities Lending Remaining Tenor) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	$ 3,270	$ 3,277
Remaining Tenor of Securities Lending Agreements: Open
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	641	647
Remaining Tenor of Securities Lending Agreements: 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	2,423	1,046
Remaining Tenor of Securities Lending Agreements: 1 to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	206	1,584
U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	2,907	2,886
U.S. government and agency | Remaining Tenor of Securities Lending Agreements: Open
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	641	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	2,060	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	206	1,584
U.S. corporate
Securities Financing Transaction [Line Items]
Cash collateral received from counterparties	254	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	254	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	106	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	106	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	3	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	3	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