Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 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	$ 14	$ 50
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(1,516)	(411)
Total realized/unrealized gains (losses) included in net income (loss)	23	67
Total realized/unrealized gains (losses) included in AOCI	44	9
Purchases	0	8
Sales	0	0
Issuances	(7)	(1)
Settlements	169	(10)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, end of period	(1,287)	(338)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	14	50
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	598	(1,114)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(3,725)	(544)
Total realized/unrealized gains (losses) included in net income (loss)	588	(1,111)
Total realized/unrealized gains (losses) included in AOCI	(60)	(75)
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	(214)	(209)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, end of period	(3,411)	(1,939)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	598	(1,114)
Residential mortgage loans — FVO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	566	314
Total realized/unrealized gains (losses) included in net income (loss)	(3)	10
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases	135	80
Sales	(33)	(5)
Issuances	0	0
Settlements	(26)	(7)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, end of period	639	392
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(3)	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	(3)	10
Corporate fixed maturity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	13,927	12,796
Total realized/unrealized gains (losses) included in net income (loss)	0	(33)
Total realized/unrealized gains (losses) included in AOCI	345	510
Purchases	1,063	668
Sales	(476)	(272)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	80	461
Transfers out of Level 3	(1,568)	(1,338)
Balance, end of period	13,371	12,792
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	6	(31)
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	(31)
U.S. government and agency
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	0
Total realized/unrealized gains (losses) included in net income (loss)	0	0
Total realized/unrealized gains (losses) included in AOCI	0	11
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	200
Transfers out of Level 3	0	0
Balance, end of period	0	211
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	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
Foreign government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	290	856
Total realized/unrealized gains (losses) included in net income (loss)	3	8
Total realized/unrealized gains (losses) included in AOCI	6	(22)
Purchases	12	19
Sales	(18)	(17)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	4	47
Transfers out of Level 3	(8)	(179)
Balance, end of period	289	712
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	2	8
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	8
Structured Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	6,865	7,116
Total realized/unrealized gains (losses) included in net income (loss)	35	31
Total realized/unrealized gains (losses) included in AOCI	63	(46)
Purchases	1,071	937
Sales	(499)	(373)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	34	11
Transfers out of Level 3	(276)	(1,024)
Balance, end of period	7,293	6,652
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	28	30
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	28	30
State and political subdivision
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	27	46
Total realized/unrealized gains (losses) included in net income (loss)	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases	0	0
Sales	0	0
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	(20)	(10)
Balance, end of period	7	36
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	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
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	604	432
Total realized/unrealized gains (losses) included in net income (loss)	(11)	(26)
Total realized/unrealized gains (losses) included in AOCI	24	43
Purchases	5	5
Sales	0	(1)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	464
Transfers out of Level 3	0	(248)
Balance, end of period	622	669
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	(11)	(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	(11)	(26)
FVO Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	287	270
Total realized/unrealized gains (losses) included in net income (loss)	7	8
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases	69	19
Sales	(17)	(11)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	2	25
Transfers out of Level 3	(13)	(62)
Balance, end of period	335	249
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	7	8
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	8
Actively Traded Securities At Estimated Fair Value And Fvo General Account Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		4
Balance, end of period		3
Short-term Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	47	291
Total realized/unrealized gains (losses) included in net income (loss)	0	1
Total realized/unrealized gains (losses) included in AOCI	0	2
Purchases	777	108
Sales	(3)	(248)
Issuances	0	0
Settlements	0	0
Transfers into Level 3	0	18
Transfers out of Level 3	(41)	(2)
Balance, end of period	780	170
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	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
Separate Accounts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,152	1,704
Total realized/unrealized gains (losses) included in net income (loss)	(24)	32
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases	136	55
Sales	(43)	(201)
Issuances	39	0
Settlements	(33)	0
Transfers into Level 3	74	0
Transfers out of Level 3	(102)	(124)
Balance, end of period	1,199	1,466
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at end of period	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