Fair Value (Unobservable Input Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net Derivatives (2)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	$ 16	$ (122)
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	(1)	9
Total realized/unrealized gains (losses) included in AOCI	(31)	4
Purchases (7)	0	0
Sales (7)	2	0
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	0	0
Transfers out of Level 3 (8)	0	(1)
Balance, end of period	50	(136)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2020 (9)	1	(8)
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	30
Net Embedded Derivatives (3)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance, beginning of period	(4,365)	(2,288)
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	233	234
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases (7)	0	0
Sales (7)	0	0
Issuances (7)	0	0
Settlements (7)	(149)	(205)
Transfers into Level 3 (8)	0	0
Transfers out of Level 3 (8)	0	0
Balance, end of period	(4,747)	(2,727)
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2020 (9)	(242)	(291)
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	457	711
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	2	0
Total realized/unrealized gains (losses) included in AOCI	44	(7)
Purchases (7)	249	16
Sales (7)	(11)	(2)
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	220	36
Transfers out of Level 3 (8)	(31)	(89)
Balance, end of period	838	679
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2020 (9)	(1)	0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	(44)
Structured Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	117	174
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	1
Total realized/unrealized gains (losses) included in AOCI	8	(2)
Purchases (7)	65	29
Sales (7)	(6)	(13)
Issuances (7)	0	0
Settlements (7)	0	0
Transfers into Level 3 (8)	68	45
Transfers out of Level 3 (8)	(18)	(8)
Balance, end of period	218	228
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2020 (9)	0	(1)
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	(8)
State and Political Subdivision
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	73	74
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)	(1)	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	72	74
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2020 (9)	0	0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
Foreign Government
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) (5) (6)	0	0
Total realized/unrealized gains (losses) included in AOCI	0	0
Purchases (7)	7	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	7	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2020 (9)	0	0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	8	3
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	1
Transfers out of Level 3 (8)	(4)	0
Balance, end of period	4	4
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2020 (9)	0	0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
Short-term Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	5	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)	(3)	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	2	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2020 (9)	0	0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
Separate Account Assets (4)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	3	1
Total realized/unrealized gains (losses) included in net income (loss) (5) (6)	0	0
Total realized/unrealized gains (losses) included in AOCI	1	0
Purchases (7)	1	0
Sales (7)	0	(1)
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	0
Changes in unrealized gains (losses) included in net income (loss) for the instruments still held at March 31, 2020 (9)	0	$ 0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	$ 0