Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net Derivatives (2)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	$ (134)	$ (284)	$ (122)	$ (279)
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	(2)	(4)	(10)	(12)
Total realized/unrealized gains (losses) included in AOCI	3	0	5	0
Purchases (7)	0	0	0	3
Sales (7)	0	0	0	0
Issuances (7)	0	0	0	0
Settlements (7)	0	0	0	0
Transfers into Level 3 (8)	0	0	0	0
Transfers out of Level 3 (8)	2	0	(4)	0
Balance, end of period	(131)	(288)	(131)	(288)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at September 30, 2019 (9)	(2)	(4)	(11)	(12)
Net Embedded Derivatives (3)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(3,450)	(1,498)	(2,288)	(2,007)
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	(703)	(15)	(1,436)	767
Total realized/unrealized gains (losses) included in AOCI	0	0		0
Purchases (7)	0	0	0	0
Sales (7)	0	0	0	0
Issuances (7)	0	0	0	0
Settlements (7)	(217)	(152)	(646)	(425)
Transfers into Level 3 (8)	0	0	0	0
Transfers out of Level 3 (8)	0	0	0	0
Balance, end of period	(4,370)	(1,665)	(4,370)	(1,665)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at September 30, 2019 (9)	(778)	(13)	(1,647)	739
Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	748	1,815	711	1,937
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	0	0	2
Total realized/unrealized gains (losses) included in AOCI	0	(44)	11	(118)
Purchases (7)	117	56	178	164
Sales (7)	(22)	(50)	(78)	(183)
Issuances (7)	0	0	0	0
Settlements (7)	0	0	0	0
Transfers into Level 3 (8)	49	20	147	20
Transfers out of Level 3 (8)	(84)	(208)	(161)	(233)
Balance, end of period	808	1,589	808	1,589
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at September 30, 2019 (9)	0	0	0	(1)
Structured Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	108	1,261	174	1,222
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	10	1	21
Total realized/unrealized gains (losses) included in AOCI	1	(8)	3	(10)
Purchases (7)	61	287	74	339
Sales (7)	(6)	(114)	(24)	(227)
Issuances (7)	0	0	0	0
Settlements (7)	0	0	0	0
Transfers into Level 3 (8)	29	3	92	0
Transfers out of Level 3 (8)	(18)	(170)	(145)	(76)
Balance, end of period	175	1,269	175	1,269
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at September 30, 2019 (9)	0	4	1	14
State and political subdivision
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	74	8	74	0
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	2	0	0
Total realized/unrealized gains (losses) included in AOCI	0	(2)	0	0
Purchases (7)	0	0	0	0
Sales (7)	(1)	(6)	(1)	0
Issuances (7)	0	0	0	0
Settlements (7)	0	0	0	0
Transfers into Level 3 (8)	0	0	0	0
Transfers out of Level 3 (8)	0	(2)	0	0
Balance, end of period	73	0	73	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at September 30, 2019 (9)	0	0	0	0
Foreign government
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	0	0	5
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases (7)	0	0	0	0
Sales (7)	0	0	0	0
Issuances (7)	0	0	0	0
Settlements (7)	0	0	0	0
Transfers into Level 3 (8)	0	0	0	0
Transfers out of Level 3 (8)	0	0	0	(5)
Balance, end of period	0	0	0	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at September 30, 2019 (9)	0	0	0	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	4	120	3	124
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	(2)	0	(4)
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases (7)	0	0	0	0
Sales (7)	0	0	0	(3)
Issuances (7)	0	0	0	0
Settlements (7)	0	0	0	0
Transfers into Level 3 (8)	0	9	1	10
Transfers out of Level 3 (8)	0	(5)	0	(5)
Balance, end of period	4	122	4	122
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at September 30, 2019 (9)	0	0	0	(4)
Short-term Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	0	0	14
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases (7)	0	0	0	0
Sales (7)	0	0	0	(14)
Issuances (7)	0	0	0	0
Settlements (7)	0	0	0	0
Transfers into Level 3 (8)	0	0	0	0
Transfers out of Level 3 (8)	0	0	0	0
Balance, end of period	0	0	0	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at September 30, 2019 (9)	0	0	0	0
Separate Account Assets (4)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	4	1	5
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	0	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0	0	0
Purchases (7)	0	1	0	1
Sales (7)	0	0	(1)	(1)
Issuances (7)	0	0	0	0
Settlements (7)	0	0	0	(1)
Transfers into Level 3 (8)	0	0	0	0
Transfers out of Level 3 (8)	0	(1)	0	0
Balance, end of period	0	4	0	4
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at September 30, 2019 (9)	$ 0	$ 0	$ 0	$ 0

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Amount of unrealized gain (loss) recognized in income for derivative asset (liability) after deduction of derivative liability (asset), measured at fair value using unobservable input (level 3) and still held.

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Amount of gain (loss) recognized in income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

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Amount of gain (loss) recognized in other comprehensive income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

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Amount of issuances of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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