Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Net Derivatives (2)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	$ (122)	$ (279)
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	(9)	5
Total realized/unrealized gains (losses) included in AOCI	(4)	0
Purchases (7)	0	1
Sales (7)	0	0
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	0	0
Transfers out of Level 3 (8)	(1)	0
Balance, end of period	(136)	(273)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2019 (9)	(8)	5
Net Embedded Derivatives (3)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(2,288)	(2,007)
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	(234)	551
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases (7)	0	0
Sales (7)	0	0
Issuances (7)	0	0
Settlements (7)	(205)	(131)
Transfers into Level 3 (8)	0	0
Transfers out of Level 3 (8)	0	0
Balance, end of period	(2,727)	(1,587)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2019 (9)	(291)	569
Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	711	1,937
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	3
Total realized/unrealized gains (losses) included in AOCI	7	(8)
Purchases (7)	16	66
Sales (7)	(2)	(102)
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	36	82
Transfers out of Level 3 (8)	(89)	(133)
Balance, end of period	679	1,845
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2019 (9)	0	1
Structured Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	174	1,222
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	(1)	6
Total realized/unrealized gains (losses) included in AOCI	2	(11)
Purchases (7)	29	94
Sales (7)	(13)	(65)
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	45	0
Transfers out of Level 3 (8)	(8)	(51)
Balance, end of period	228	1,195
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2019 (9)	(1)	6
State and political subdivision
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	74	0
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases (7)	0	0
Sales (7)	0	0
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	0	0
Transfers out of Level 3 (8)	0	0
Balance, end of period	74	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2019 (9)	0	0
Foreign government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	5
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases (7)	0	0
Sales (7)	0	(5)
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	0	0
Transfers out of Level 3 (8)	0	0
Balance, end of period	0	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2019 (9)	0	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	3	124
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	(1)
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases (7)	0	0
Sales (7)	0	0
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	1	0
Transfers out of Level 3 (8)	0	0
Balance, end of period	4	123
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2019 (9)	0	0
Short Term Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	14
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases (7)	0	0
Sales (7)	0	0
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	0	0
Transfers out of Level 3 (8)	0	(14)
Balance, end of period	0	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2019 (9)	0	0
Separate Account Assets (4)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1	5
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases (7)	0	3
Sales (7)	(1)	(1)
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	0	0
Transfers out of Level 3 (8)	0	0
Balance, end of period	0	7
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2019 (9)	$ 0	$ 0

Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

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