Investments (Securities Lending and Repurchase Agreements Remaining Tenor ) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	$ 21,055	$ 18,628
Open (1)
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	5,901	2,949
1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	7,337	10,844
Over 1 Month to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	7,817	4,835
Over 6 Months to 1 Year
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	3,325	3,210
U.S. government and agency
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	20,007	17,508
U.S. government and agency | Open (1)
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	5,900	2,946
U.S. government and agency | 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	7,052	10,553
U.S. government and agency | Over 1 Month to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	7,055	4,009
U.S. government and agency | Over 6 Months to 1 Year
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
U.S. government and agency | Repurchase Agreements
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,325	3,210
U.S. government and agency | Repurchase Agreements | Open (1)
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
U.S. government and agency | Repurchase Agreements | 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	3,325	3,210
U.S. government and agency | Repurchase Agreements | Over 1 Month to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
U.S. government and agency | Repurchase Agreements | Over 6 Months to 1 Year
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
Foreign government
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	1,047	1,117
Foreign government | Open (1)
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
Foreign government | 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	285	291
Foreign government | Over 1 Month to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	762	826
Foreign government | Over 6 Months to 1 Year
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
U.S. corporate
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	1	3
U.S. corporate | Open (1)
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	1	3
U.S. corporate | 1 Month or Less
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
U.S. corporate | Over 1 Month to 6 Months
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	0	0
U.S. corporate | Over 6 Months to 1 Year
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	$ 0	$ 0