Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Residential mortgage loans - FVO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 405	$ 615	$ 520	$ 566
Total realized/unrealized gains (losses) included in net income (loss)	4	32	7	38
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	0	10	0	184
Sales	(70)	(72)	(151)	(155)
Issuances	0	0	0	0
Settlements	(16)	(21)	(53)	(69)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	323	564	323	564
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(5)	32	(13)	38
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	(5)	32	(13)	38
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	(38)	27	(66)	27
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(267)	(288)	(132)	(562)
Total realized/unrealized gains (losses) included in net income (loss)	(70)	33	(151)	47
Total realized/unrealized gains (losses) included in AOCI	(107)	4	(228)	144
Purchases	0	0	4	0
Sales	0	0	0	0
Issuances	0	0	0	(7)
Settlements	37	(12)	100	115
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	(407)	(263)	(407)	(263)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(38)	27	(66)	27
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	168	271	352	550
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(240)	(646)	(274)	(729)
Total realized/unrealized gains (losses) included in net income (loss)	167	291	355	573
Total realized/unrealized gains (losses) included in AOCI	9	4	6	(42)
Purchases	0	0	0	0
Sales	0	0	0	0
Issuances	0	0	0	0
Settlements	(75)	(92)	(226)	(245)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, end of period	(139)	(443)	(139)	(443)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	168	271	352	550
Corporate fixed maturity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	10,621	11,632	11,219	11,537
Total realized/unrealized gains (losses) included in net income (loss)	2	(3)	13	6
Total realized/unrealized gains (losses) included in AOCI	(176)	164	(621)	612
Purchases	594	713	1,606	2,802
Sales	(497)	(285)	(1,366)	(1,487)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	84	123	88	83
Transfers out of Level 3	(295)	(226)	(606)	(1,435)
Balance, end of period	10,333	12,118	10,333	12,118
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	2	(2)	3	6
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	2	(2)	3	6
Foreign government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	156	208	209	289
Total realized/unrealized gains (losses) included in net income (loss)	0	1	1	3
Total realized/unrealized gains (losses) included in AOCI	(4)	(2)	(16)	4
Purchases	4	0	5	7
Sales	(6)	0	(21)	(97)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	5	0	0	0
Transfers out of Level 3	(15)	(9)	(38)	(8)
Balance, end of period	140	198	140	198
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	1	1	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	0	1	1	3
Structured Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	4,677	4,939	4,841	5,215
Total realized/unrealized gains (losses) included in net income (loss)	30	13	73	80
Total realized/unrealized gains (losses) included in AOCI	(15)	31	1	118
Purchases	746	468	919	867
Sales	(281)	(478)	(788)	(1,329)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	36	0	50	10
Transfers out of Level 3	(977)	(440)	(880)	(428)
Balance, end of period	4,216	4,533	4,216	4,533
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	27	22	66	68
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	27	22	66	68
State and political subdivision
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	8	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	2
Purchases	0	0	0	0
Sales	0	(1)	0	0
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	62	0	59
Transfers out of Level 3	(8)	0	0	(10)
Balance, end of period	0	61	0	61
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	408	468	428	468
Total realized/unrealized gains (losses) included in net income (loss)	(1)	(1)	(11)	(14)
Total realized/unrealized gains (losses) included in AOCI	0	(4)	0	30
Purchases	6	13	11	18
Sales	(7)	(52)	(20)	(74)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	45	0	45	0
Transfers out of Level 3	(8)	0	(10)	(4)
Balance, end of period	443	424	443	424
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	0	(2)	0	(12)
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	(2)	0	(12)
Unit-linked and FVO Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	269	312	362	287
Total realized/unrealized gains (losses) included in net income (loss)	(2)	7	(7)	20
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	48	73	77	209
Sales	(32)	(70)	(162)	(115)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	12	3	10	3
Transfers out of Level 3	(69)	(21)	(54)	(100)
Balance, end of period	226	304	226	304
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(2)	7	(8)	16
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	(2)	7	(8)	16
Other limited partnership interests
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	168	0	0	0
Total realized/unrealized gains (losses) included in net income (loss)	11	0	6	0
Total realized/unrealized gains (losses) included in AOCI	(4)	0	0	0
Purchases	1	0	1	0
Sales	(21)	0	(68)	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	155	0	155	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	11	0	6	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	11	0	6	0
Short-term Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	559	822	33	46
Total realized/unrealized gains (losses) included in net income (loss)	0	0	0	0
Total realized/unrealized gains (losses) included in AOCI	(3)	0	(7)	0
Purchases	102	1	659	401
Sales	(2)	(247)	(11)	(2)
Issuances	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	2	0	2
Transfers out of Level 3	(2)	(175)	(20)	(44)
Balance, end of period	654	403	654	403
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 Accounts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,138	959	959	1,141
Total realized/unrealized gains (losses) included in net income (loss)	2	7	2	(22)
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases	148	136	200	271
Sales	(215)	(18)	(162)	(78)
Issuances	0	1	(3)	1
Settlements	0	(1)	0	(62)
Transfers into Level 3	5	56	81	21
Transfers out of Level 3	(77)	(101)	(76)	(233)
Balance, end of period	1,001	1,039	1,001	1,039
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