Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets [Abstract]
Debt Securities, Available-for-sale	$ 70,202	$ 69,977
Equity securities	122	147
Short-term Investments	3,729	1,482
Derivative assets: (1)	9,776	3,222
Embedded derivatives within asset host contracts	316	217
Separate account assets	83,049	99,668
Liabilities [Abstract]
Derivative liabilities: (1)	7,706	7,119
Embedded derivatives within liability host contracts	5,063	4,582
Recurring
Assets [Abstract]
Debt Securities, Available-for-sale	70,202	69,977
Equity securities	122	147
Short-term Investments	3,729	1,482
Derivative assets: (1)	9,460	3,005
Embedded derivatives within asset host contracts	316	217
Separate account assets	83,049	99,668
Total assets	166,878	174,496
Liabilities [Abstract]
Derivative liabilities: (1)	2,643	2,537
Embedded derivatives within liability host contracts	5,063	4,582
Total liabilities	7,706	7,119
Recurring | Interest rate derivatives
Assets [Abstract]
Derivative assets: (1)	5,950	1,778
Liabilities [Abstract]
Derivative liabilities: (1)	840	330
Recurring | Foreign currency exchange rate
Assets [Abstract]
Derivative assets: (1)	826	270
Liabilities [Abstract]
Derivative liabilities: (1)	16	43
Recurring | Credit
Assets [Abstract]
Derivative assets: (1)	7	36
Liabilities [Abstract]
Derivative liabilities: (1)	13
Recurring | Equity market
Assets [Abstract]
Derivative assets: (1)	2,677	921
Liabilities [Abstract]
Derivative liabilities: (1)	1,774	2,164
Recurring | U.S. Corporate
Assets [Abstract]
Debt Securities, Available-for-sale	30,124	30,591
Recurring | Foreign Corporate
Assets [Abstract]
Debt Securities, Available-for-sale	9,101	9,686
Recurring | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	8,813	9,030
Recurring | U.S. Government and Agency
Assets [Abstract]
Debt Securities, Available-for-sale	8,744	7,244
Recurring | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	5,678	5,714
Recurring | State and Political Subdivision
Assets [Abstract]
Debt Securities, Available-for-sale	4,073	4,011
Recurring | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	2,022	1,950
Recurring | Foreign Government
Assets [Abstract]
Debt Securities, Available-for-sale	1,647	1,751
Recurring | Level 1
Assets [Abstract]
Debt Securities, Available-for-sale	1,779	1,542
Equity securities	11	14
Short-term Investments	2,219	1,004
Derivative assets: (1)	0	0
Embedded derivatives within asset host contracts	0	0
Separate account assets	198	180
Total assets	4,207	2,740
Liabilities [Abstract]
Derivative liabilities: (1)	0	0
Embedded derivatives within liability host contracts	0	0
Total liabilities	0	0
Recurring | Level 1 | Interest rate derivatives
Assets [Abstract]
Derivative assets: (1)	0	0
Liabilities [Abstract]
Derivative liabilities: (1)	0	0
Recurring | Level 1 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets: (1)	0	0
Liabilities [Abstract]
Derivative liabilities: (1)	0	0
Recurring | Level 1 | Credit
Assets [Abstract]
Derivative assets: (1)	0	0
Liabilities [Abstract]
Derivative liabilities: (1)	0
Recurring | Level 1 | Equity market
Assets [Abstract]
Derivative assets: (1)	0	0
Liabilities [Abstract]
Derivative liabilities: (1)	0	0
Recurring | Level 1 | U.S. Corporate
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 1 | Foreign Corporate
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 1 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 1 | U.S. Government and Agency
Assets [Abstract]
Debt Securities, Available-for-sale	1,779	1,542
Recurring | Level 1 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 1 | State and Political Subdivision
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 1 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 1 | Foreign Government
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 2
Assets [Abstract]
Debt Securities, Available-for-sale	67,288	67,788
Equity securities	107	125
Short-term Investments	1,508	473
Derivative assets: (1)	9,369	2,918
Embedded derivatives within asset host contracts	0	0
Separate account assets	82,847	99,485
Total assets	161,119	170,789
Liabilities [Abstract]
Derivative liabilities: (1)	2,602	2,466
Embedded derivatives within liability host contracts	0	0
Total liabilities	2,602	2,466
Recurring | Level 2 | Interest rate derivatives
Assets [Abstract]
Derivative assets: (1)	5,950	1,778
Liabilities [Abstract]
Derivative liabilities: (1)	840	330
Recurring | Level 2 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets: (1)	786	265
Liabilities [Abstract]
Derivative liabilities: (1)	16	43
Recurring | Level 2 | Credit
Assets [Abstract]
Derivative assets: (1)	0	25
Liabilities [Abstract]
Derivative liabilities: (1)	9
Recurring | Level 2 | Equity market
Assets [Abstract]
Derivative assets: (1)	2,633	850
Liabilities [Abstract]
Derivative liabilities: (1)	1,737	2,093
Recurring | Level 2 | U.S. Corporate
Assets [Abstract]
Debt Securities, Available-for-sale	29,495	30,266
Recurring | Level 2 | Foreign Corporate
Assets [Abstract]
Debt Securities, Available-for-sale	8,892	9,554
Recurring | Level 2 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	8,730	8,986
Recurring | Level 2 | U.S. Government and Agency
Assets [Abstract]
Debt Securities, Available-for-sale	6,965	5,702
Recurring | Level 2 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	5,659	5,714
Recurring | Level 2 | State and Political Subdivision
Assets [Abstract]
Debt Securities, Available-for-sale	4,001	3,938
Recurring | Level 2 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	1,906	1,877
Recurring | Level 2 | Foreign Government
Assets [Abstract]
Debt Securities, Available-for-sale	1,640	1,751
Recurring | Level 3
Assets [Abstract]
Debt Securities, Available-for-sale	1,135	647
Equity securities	4	8
Short-term Investments	2	5
Derivative assets: (1)	91	87
Embedded derivatives within asset host contracts	316	217
Separate account assets	4	3
Total assets	1,552	967
Liabilities [Abstract]
Derivative liabilities: (1)	41	71
Embedded derivatives within liability host contracts	5,063	4,582
Total liabilities	5,104	4,653
Recurring | Level 3 | Interest rate derivatives
Assets [Abstract]
Derivative assets: (1)	0	0
Liabilities [Abstract]
Derivative liabilities: (1)	0	0
Recurring | Level 3 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets: (1)	40	5
Liabilities [Abstract]
Derivative liabilities: (1)	0	0
Recurring | Level 3 | Credit
Assets [Abstract]
Derivative assets: (1)	7	11
Liabilities [Abstract]
Derivative liabilities: (1)	4
Recurring | Level 3 | Equity market
Assets [Abstract]
Derivative assets: (1)	44	71
Liabilities [Abstract]
Derivative liabilities: (1)	37	71
Recurring | Level 3 | U.S. Corporate
Assets [Abstract]
Debt Securities, Available-for-sale	629	325
Recurring | Level 3 | Foreign Corporate
Assets [Abstract]
Debt Securities, Available-for-sale	209	132
Recurring | Level 3 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	83	44
Recurring | Level 3 | U.S. Government and Agency
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 3 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	19	0
Recurring | Level 3 | State and Political Subdivision
Assets [Abstract]
Debt Securities, Available-for-sale	72	73
Recurring | Level 3 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	116	73
Recurring | Level 3 | Foreign Government
Assets [Abstract]
Debt Securities, Available-for-sale	$ 7	$ 0