Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 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	$ 94	$ 163	$ 102	$ 207
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(1,287)	(338)	(1,516)	(411)
Total realized/unrealized gains (losses) included in net income (loss)	110	165	126	228
Total realized/unrealized gains (losses) included in AOCI	96	41	135	51
Purchases	4	4	4	12
Sales	0	0	0	0
Issuances	0	(1)	(7)	(1)
Settlements	9	2	190	(9)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(5)	0	(2)
Balance, end of period	(1,068)	(132)	(1,068)	(132)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	94	163	102	207
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	95	(4,520)	693	(5,634)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(3,411)	(1,939)	(3,725)	(544)
Total realized/unrealized gains (losses) included in net income (loss)	116	(4,505)	704	(5,616)
Total realized/unrealized gains (losses) included in AOCI	13	(135)	(47)	(210)
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	(219)	(225)	(433)	(434)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	(3,501)	(6,804)	(3,501)	(6,804)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	95	(4,520)	693	(5,634)
Residential mortgage loans — FVO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	639	392	566	314
Total realized/unrealized gains (losses) included in net income (loss)	6	1	3	11
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	42	71	174	149
Sales	(47)	(4)	(79)	(8)
Issuances	0	0	0	0
Settlements	(25)	(11)	(49)	(17)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	615	449	615	449
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	6	1	3	11
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	6	1	3	11
Corporate fixed maturity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	13,371	12,792	13,927	12,796
Total realized/unrealized gains (losses) included in net income (loss)	10	(5)	2	(44)
Total realized/unrealized gains (losses) included in AOCI	239	339	588	929
Purchases	1,694	852	2,612	1,316
Sales	(1,334)	(306)	(1,656)	(602)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	257	490	138	639
Transfers out of Level 3	(249)	(452)	(1,623)	(1,324)
Balance, end of period	13,988	13,710	13,988	13,710
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	7	(5)	3	(44)
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	7	(5)	3	(44)
U.S. government and agency
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	211	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	7	0	18
Purchases	0	105	0	105
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	200
Transfers out of Level 3	0	0	0	0
Balance, end of period	0	323	0	323
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	289	712	290	856
Total realized/unrealized gains (losses) included in net income (loss)	1	4	2	8
Total realized/unrealized gains (losses) included in AOCI	(1)	2	5	(3)
Purchases	5	65	12	79
Sales	(5)	(19)	(87)	(23)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	103	4	41
Transfers out of Level 3	(81)	(491)	(18)	(582)
Balance, end of period	208	376	208	376
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	1	4	2	7
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	4	2	7
Structured Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	7,293	6,652	6,865	7,116
Total realized/unrealized gains (losses) included in net income (loss)	41	30	75	60
Total realized/unrealized gains (losses) included in AOCI	55	5	117	(9)
Purchases	567	940	803	1,546
Sales	(726)	(478)	(1,140)	(903)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	65	12	78	30
Transfers out of Level 3	(878)	(461)	(381)	(1,140)
Balance, end of period	6,417	6,700	6,417	6,700
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	39	35	67	63
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	39	35	67	63
State and political subdivision
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	7	36	27	46
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	17	0	17
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	(7)	0	(27)	(10)
Balance, end of period	0	53	0	53
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	622	669	604	432
Total realized/unrealized gains (losses) included in net income (loss)	(4)	0	(14)	(24)
Total realized/unrealized gains (losses) included in AOCI	14	11	38	41
Purchases	5	19	9	23
Sales	(36)	(17)	(36)	(62)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	2	0	457
Transfers out of Level 3	0	(2)	0	(185)
Balance, end of period	601	682	601	682
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(4)	0	(10)	(26)
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	(4)	0	(10)	(26)
FVO Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	335	249	287	270
Total realized/unrealized gains (losses) included in net income (loss)	9	(3)	16	5
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	150	11	207	26
Sales	(109)	(19)	(109)	(26)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	3	6	8	23
Transfers out of Level 3	(76)	(13)	(97)	(67)
Balance, end of period	312	231	312	231
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	9	(3)	14	5
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	9	(3)	14	5
Short-term Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	780	170	47	291
Total realized/unrealized gains (losses) included in net income (loss)	1	0	1	0
Total realized/unrealized gains (losses) included in AOCI	(1)	5	(1)	8
Purchases	190	115	913	126
Sales	(1)	(6)	(17)	(247)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	2	0	0
Transfers out of Level 3	(56)	(111)	(30)	(3)
Balance, end of period	913	175	913	175
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	1	0	1	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	1	0	1	0
Separate Accounts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,199	1,466	1,152	1,704
Total realized/unrealized gains (losses) included in net income (loss)	2	33	(16)	62
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	134	209	171	226
Sales	(86)	(49)	(58)	(234)
Issuances	0	(2)	1	2
Settlements	(16)	5	(50)	(4)
Transfers into Level 3	16	2	14	4
Transfers out of Level 3	(284)	(37)	(249)	(133)
Balance, end of period	965	1,627	965	1,627
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