Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Derivatives
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at January 1,	$ (122)	$ (279)
Total realized/unrealized gains (losses) included in net income (loss)	(12)	152	$ 92
Total realized/unrealized gains (losses) included in AOCI	(1)	9	0
Purchases	0	3
Sales	0	(7)
Issuances	0	0
Settlements	155	0
Transfers into Level 3	0	0
Transfers out of Level 3	(4)	0
Balance at December 31,	16	(122)	(279)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(10)	148	(52)
Net Embedded Derivatives
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at January 1,	(2,288)	(2,007)
Total realized/unrealized gains (losses) included in net income (loss)	(1,249)	571	1,233
Total realized/unrealized gains (losses) included in AOCI	0	0	0
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	(828)	(852)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at December 31,	(4,365)	(2,288)	(2,007)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(1,504)	268	1,300
U.S. corporate and foreign corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	711	1,937
Total realized/unrealized gains (losses) included in net income (loss)	0	1	(3)
Total realized/unrealized gains (losses) included in AOCI	15	(32)	127
Purchases	342	71
Sales	(150)	(197)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	24	414
Transfers out of Level 3	(485)	(1,483)
Balance at December 31,	457	711	1,937
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	(2)	1
Structured securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	174	1,222
Total realized/unrealized gains (losses) included in net income (loss)	1	2	28
Total realized/unrealized gains (losses) included in AOCI	2	(6)	52
Purchases	68	42
Sales	(25)	(91)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	42	9
Transfers out of Level 3	(145)	(1,004)
Balance at December 31,	117	174	1,222
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	(1)	23
State and political subdivision
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	74	0
Total realized/unrealized gains (losses) included in net income (loss)	1	1	0
Total realized/unrealized gains (losses) included in AOCI	(1)	(1)	0
Purchases	0	0
Sales	(1)	(1)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	75
Transfers out of Level 3	0	0
Balance at December 31,	73	74	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	1	1	0
Foreign government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	0	5
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	0
Sales	0	(5)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at December 31,	0	0	5
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	3	124
Total realized/unrealized gains (losses) included in net income (loss)	0	0	(3)
Total realized/unrealized gains (losses) included in AOCI	0	0	0
Purchases	5	1
Sales	0	(3)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	(119)
Balance at December 31,	8	3	124
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	1	0
Short-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	0	14
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	5	0
Sales	0	(14)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at December 31,	5	0	14
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0
Separate account assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1,	1	5
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	3	1
Sales	0	(1)
Issuances	0	0
Settlements	0	(1)
Transfers into Level 3	0	0
Transfers out of Level 3	(1)	(3)
Balance at December 31,	3	1	5
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	$ 0	$ 0	$ 0