Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Derivatives
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at January 1,	$ 16	$ (122)
Total realized/unrealized gains (losses) included in net income (loss)	9	(12)	$ 152
Total realized/unrealized gains (losses) included in AOCI	(9)	(1)	9
Purchases	0	0
Sales	(14)	0
Issuances	0	0
Settlements	0	155
Transfers into Level 3	0	0
Transfers out of Level 3	0	(4)
Balance at December 31,	2	16	(122)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(4)	(10)	148
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	(9)
Net Embedded Derivatives
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at January 1,	(4,365)	(2,288)
Total realized/unrealized gains (losses) included in net income (loss)	(2,325)	(1,249)	571
Total realized/unrealized gains (losses) included in AOCI	0	0	0
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	(611)	(828)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at December 31,	(7,301)	(4,365)	(2,288)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(2,398)	(1,504)	268
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
U.S. corporate and foreign corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	457	711
Total realized/unrealized gains (losses) included in net income (loss)	(6)	0	1
Total realized/unrealized gains (losses) included in AOCI	(3)	15	(32)
Purchases	409	342
Sales	(117)	(150)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	186	24
Transfers out of Level 3	(242)	(485)
Balance at December 31,	684	457	711
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(5)	0	(2)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	(3)
Structured securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	117	174
Total realized/unrealized gains (losses) included in net income (loss)	0	1	2
Total realized/unrealized gains (losses) included in AOCI	1	2	(6)
Purchases	58	68
Sales	(5)	(25)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	11	42
Transfers out of Level 3	(115)	(145)
Balance at December 31,	67	117	174
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	(1)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	1
State and Political Subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	73	74
Total realized/unrealized gains (losses) included in net income (loss)	0	1	1
Total realized/unrealized gains (losses) included in AOCI	0	(1)	(1)
Purchases	0	0
Sales	0	(1)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	(73)	0
Balance at December 31,	0	73	74
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	1	1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	8	3
Total realized/unrealized gains (losses) included in net income (loss)	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0
Purchases	0	5
Sales	0	0
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	(5)	0
Balance at December 31,	3	8	3
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
Short-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	5	0
Total realized/unrealized gains (losses) included in net income (loss)	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0
Purchases	0	5
Sales	(5)	0
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at December 31,	0	5	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
Separate account assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	3	1
Total realized/unrealized gains (losses) included in net income (loss)	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0
Purchases	0	3
Sales	0	0
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	(1)
Balance at December 31,	3	3	1
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	$ 0