Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Assets [Abstract]
Debt Securities, Available-for-sale	$ 66,011	$ 61,348
Equity securities	153	140
Short-term Investments	386	0
Derivative assets: (1)	3,093	2,993
Embedded derivatives within asset host contracts	253	228
Separate account assets	98,857	91,511
Liabilities [Abstract]
Derivative liabilities: (1)	5,871	4,628
Embedded derivatives within liability host contracts	3,703	2,516
Recurring
Assets [Abstract]
Debt Securities, Available-for-sale	66,011	61,348
Equity securities	153	140
Short-term Investments	386
Derivative assets: (1)	2,840	2,765
Embedded derivatives within asset host contracts	253	228
Separate account assets	98,857	91,511
Total assets	168,500	155,992
Liabilities [Abstract]
Derivative liabilities: (1)	2,168	2,112
Embedded derivatives within liability host contracts	3,703	2,516
Total liabilities	5,871	4,628
Recurring | Interest rate derivatives
Assets [Abstract]
Derivative assets: (1)	1,646	717
Liabilities [Abstract]
Derivative liabilities: (1)	148	619
Recurring | Foreign currency exchange rate
Assets [Abstract]
Derivative assets: (1)	332	299
Liabilities [Abstract]
Derivative liabilities: (1)	54	48
Recurring | Credit
Assets [Abstract]
Derivative assets: (1)	32	17
Liabilities [Abstract]
Derivative liabilities: (1)		3
Recurring | Equity market
Assets [Abstract]
Derivative assets: (1)	830	1,732
Liabilities [Abstract]
Derivative liabilities: (1)	1,966	1,442
Recurring | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	27,738	24,059
Recurring | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	7,060	8,644
Recurring | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	9,294	8,435
Recurring | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	9,416	7,895
Recurring | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	5,177	5,133
Recurring | State and political subdivision
Assets [Abstract]
Debt Securities, Available-for-sale	3,825	3,586
Recurring | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	1,842	2,111
Recurring | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	1,659	1,485
Recurring | Level 1
Assets [Abstract]
Debt Securities, Available-for-sale	1,413	2,334
Equity securities	16	13
Short-term Investments	274
Derivative assets: (1)	0	0
Embedded derivatives within asset host contracts	0	0
Separate account assets	322	217
Total assets	2,025	2,564
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 | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	1,413	2,334
Recurring | Level 1 | RMBS
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 | 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	63,668	58,055
Equity securities	133	124
Short-term Investments	112
Derivative assets: (1)	2,720	2,649
Embedded derivatives within asset host contracts	0	0
Separate account assets	98,535	91,293
Total assets	165,168	152,121
Liabilities [Abstract]
Derivative liabilities: (1)	1,914	1,874
Embedded derivatives within liability host contracts	0	0
Total liabilities	1,914	1,874
Recurring | Level 2 | Interest rate derivatives
Assets [Abstract]
Derivative assets: (1)	1,646	717
Liabilities [Abstract]
Derivative liabilities: (1)	148	619
Recurring | Level 2 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets: (1)	321	288
Liabilities [Abstract]
Derivative liabilities: (1)	50	48
Recurring | Level 2 | Credit
Assets [Abstract]
Derivative assets: (1)	22	10
Liabilities [Abstract]
Derivative liabilities: (1)		2
Recurring | Level 2 | Equity market
Assets [Abstract]
Derivative assets: (1)	731	1,634
Liabilities [Abstract]
Derivative liabilities: (1)	1,716	1,205
Recurring | Level 2 | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	27,367	23,740
Recurring | Level 2 | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	5,647	6,310
Recurring | Level 2 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	9,240	8,429
Recurring | Level 2 | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	9,039	7,503
Recurring | Level 2 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	5,163	5,004
Recurring | Level 2 | State and political subdivision
Assets [Abstract]
Debt Securities, Available-for-sale	3,751	3,512
Recurring | Level 2 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	1,802	2,072
Recurring | Level 2 | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	1,659	1,485
Recurring | Level 3
Assets [Abstract]
Debt Securities, Available-for-sale	930	959
Equity securities	4	3
Short-term Investments	0
Derivative assets: (1)	120	116
Embedded derivatives within asset host contracts	253	228
Separate account assets	0	1
Total assets	1,307	1,307
Liabilities [Abstract]
Derivative liabilities: (1)	254	238
Embedded derivatives within liability host contracts	3,703	2,516
Total liabilities	3,957	2,754
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)	11	11
Liabilities [Abstract]
Derivative liabilities: (1)	4	0
Recurring | Level 3 | Credit
Assets [Abstract]
Derivative assets: (1)	10	7
Liabilities [Abstract]
Derivative liabilities: (1)		1
Recurring | Level 3 | Equity market
Assets [Abstract]
Derivative assets: (1)	99	98
Liabilities [Abstract]
Derivative liabilities: (1)	250	237
Recurring | Level 3 | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	371	319
Recurring | Level 3 | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 3 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	54	6
Recurring | Level 3 | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	377	392
Recurring | Level 3 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	14	129
Recurring | Level 3 | State and political subdivision
Assets [Abstract]
Debt Securities, Available-for-sale	74	74
Recurring | Level 3 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	40	39
Recurring | Level 3 | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	$ 0	$ 0