Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net Derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	$ 4	$ (110)	$ 98	$ (67)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(780)	(182)	(954)	(232)
Total realized/unrealized gains (losses) included in net income (loss)	4	(113)	100	(76)
Total realized/unrealized gains (losses) included in AOCI	0	1	0	9
Purchases	0	0	4	7
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	370	(12)	444	(14)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	(406)	(306)	(406)	(306)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	4	(110)	98	(67)
Net Embedded Derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	341	503	862	(3,392)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(2,477)	(4,602)	(2,761)	(442)
Total realized/unrealized gains (losses) included in net income (loss)	561	512	1,029	(3,382)
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	(153)	(155)	(337)	(421)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	(2,069)	(4,245)	(2,069)	(4,245)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	341	503	862	(3,392)
U.S. corporate and foreign corporate securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	2,295	2,694	2,310	2,410
Total realized/unrealized gains (losses) included in net income (loss)	1	8	(2)	1
Total realized/unrealized gains (losses) included in AOCI	34	2	176	179
Purchases	92	111	235	293
Sales	(56)	(193)	(230)	(268)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	191	51	180	165
Transfers out of Level 3	(19)	(271)	(131)	(378)
Balance, end of period	2,538	2,402	2,538	2,402
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	1	1	1	2
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	1	1	1	2
U.S. Government and Agency
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	25	0	0
Total realized/unrealized gains (losses) included in net income (loss)	0	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0	3
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	19
Transfers out of Level 3	0	(3)	0	0
Balance, end of period	0	22	0	22
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Structured Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,481	1,859	1,695	1,996
Total realized/unrealized gains (losses) included in net income (loss)	13	8	22	21
Total realized/unrealized gains (losses) included in AOCI	6	14	43	(4)
Purchases	147	112	186	505
Sales	(230)	(142)	(460)	(380)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	37	0	17
Transfers out of Level 3	(14)	(77)	(83)	(344)
Balance, end of period	1,403	1,811	1,403	1,811
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	10	8	19	21
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	10	8	19	21
State and political subdivision
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	8	17	13
Total realized/unrealized gains (losses) included in net income (loss)	0	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	0	0	0	0
Sales	(1)	0	(1)	0
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	10	0	3	0
Transfers out of Level 3	0	0	(10)	(5)
Balance, end of period	9	8	9	8
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Foreign government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	9	0	27
Total realized/unrealized gains (losses) included in net income (loss)	0	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(9)	0	(27)
Balance, end of period	0	0	0	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	134	173	137	97
Total realized/unrealized gains (losses) included in net income (loss)	0	1	0	0
Total realized/unrealized gains (losses) included in AOCI	(1)	3	2	3
Purchases	0	0	4	0
Sales	(3)	(9)	(13)	(9)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	129
Transfers out of Level 3	0	(2)	0	(54)
Balance, end of period	130	166	130	166
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Short-term Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	91	111	2	47
Total realized/unrealized gains (losses) included in net income (loss)	0	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	0	442	1	442
Sales	0	0	(1)	(47)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	(90)	(111)	(1)	0
Balance, end of period	1	442	1	442
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Separate Account Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	6	142	10	146
Total realized/unrealized gains (losses) included in net income (loss)	0	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	2	0	2	1
Sales	0	(129)	(3)	(130)
Issuances	0	0	0	0
Settlements	0	0	0	(1)
Transfers into Level 3	0	0	1	0
Transfers out of Level 3	(2)	(3)	(4)	(6)
Balance, end of period	6	10	6	10
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	$ 0	$ 0	$ 0	$ 0