Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Residential mortgage loans - FVO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 438	$ 639	$ 520	$ 566
Total realized/unrealized gains (losses) included in net income (loss)	1	6	3	3
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	0	42	0	174
Sales	(17)	(47)	(81)	(79)
Issuances	0	0	0	0
Settlements	(17)	(25)	(37)	(49)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	405	615	405	615
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(1)	6	(8)	3
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)	6	(8)	3
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	(86)	(12)	(18)	9
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(182)	(397)	(132)	(562)
Total realized/unrealized gains (losses) included in net income (loss)	(106)	4	(94)	30
Total realized/unrealized gains (losses) included in AOCI	(19)	96	(123)	135
Purchases	4	0	4	0
Sales	0	0	0	0
Issuances	0	0	0	(7)
Settlements	36	9	78	116
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	(267)	(288)	(267)	(288)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(86)	(12)	(18)	9
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	153	112	184	279
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(328)	(695)	(274)	(729)
Total realized/unrealized gains (losses) included in net income (loss)	152	114	188	283
Total realized/unrealized gains (losses) included in AOCI	13	13	(3)	(46)
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	(77)	(78)	(151)	(154)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	(240)	(646)	(240)	(646)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	153	112	184	279
Corporate fixed maturity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	10,810	10,968	11,219	11,537
Total realized/unrealized gains (losses) included in net income (loss)	1	9	9	4
Total realized/unrealized gains (losses) included in AOCI	(369)	216	(433)	458
Purchases	806	1,523	1,321	2,320
Sales	(512)	(1,086)	(1,221)	(1,357)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	1	227	140	135
Transfers out of Level 3	(116)	(225)	(414)	(1,465)
Balance, end of period	10,621	11,632	10,621	11,632
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	1	7	2	3
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	7	2	3
Foreign government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	179	289	209	289
Total realized/unrealized gains (losses) included in net income (loss)	1	1	2	3
Total realized/unrealized gains (losses) included in AOCI	(9)	(1)	(12)	5
Purchases	0	5	1	12
Sales	(14)	(5)	(16)	(87)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	4
Transfers out of Level 3	(1)	(81)	(28)	(18)
Balance, end of period	156	208	156	208
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	1	1	1
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	1	1	1
Structured Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	4,582	5,705	4,841	5,215
Total realized/unrealized gains (losses) included in net income (loss)	21	35	43	66
Total realized/unrealized gains (losses) included in AOCI	(12)	33	12	80
Purchases	998	543	1,022	735
Sales	(275)	(589)	(539)	(918)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	2	65	51	78
Transfers out of Level 3	(639)	(853)	(753)	(317)
Balance, end of period	4,677	4,939	4,677	4,939
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	19	33	39	57
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	19	33	39	57
State and political subdivision
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	0	0	10
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	8	0	8	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	0	0	(10)
Balance, end of period	8	0	8	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	422	480	428	468
Total realized/unrealized gains (losses) included in net income (loss)	(5)	(4)	(10)	(14)
Total realized/unrealized gains (losses) included in AOCI	0	13	0	35
Purchases	7	5	5	6
Sales	(16)	(26)	(15)	(27)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	408	468	408	468
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	(4)	0	(10)
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	(4)	0	(10)
Unit-linked and FVO Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	286	335	362	287
Total realized/unrealized gains (losses) included in net income (loss)	(11)	9	(6)	16
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	84	150	104	207
Sales	(81)	(109)	(141)	(109)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	3	0	8
Transfers out of Level 3	(9)	(76)	(50)	(97)
Balance, end of period	269	312	269	312
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(10)	9	(7)	14
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)	9	(7)	14
Other limited partnership interests
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	194	0	0	0
Total realized/unrealized gains (losses) included in net income (loss)	0	0	(5)	0
Total realized/unrealized gains (losses) included in AOCI	2	0	4	0
Purchases	0	0	0	0
Sales	(28)	0	(47)	0
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	216	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	168	0	168	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	0	(5)	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	(5)	0
Short-term Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	615	779	33	46
Total realized/unrealized gains (losses) included in net income (loss)	0	1	0	1
Total realized/unrealized gains (losses) included in AOCI	(3)	(1)	(3)	(1)
Purchases	4	99	560	822
Sales	(33)	(1)	(11)	(17)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	(24)	(55)	(20)	(29)
Balance, end of period	559	822	559	822
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	1	0	1
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	1	0	1
Separate Accounts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,224	1,184	959	1,141
Total realized/unrealized gains (losses) included in net income (loss)	(1)	2	1	(17)
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	270	131	307	171
Sales	(323)	(81)	(147)	(54)
Issuances	(2)	0	(3)	1
Settlements	2	(16)	1	(50)
Transfers into Level 3	71	16	99	12
Transfers out of Level 3	(103)	(277)	(79)	(245)
Balance, end of period	1,138	959	1,138	959
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