Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	$ 69,977	$ 61,348
Available-for-sale Securities, Equity Securities	147	140
Short-term investments, principally at estimated fair value	1,482	0
Derivative assets	3,222	2,993
Net embedded derivatives within asset host contracts	217	228
Separate account assets	99,668	91,511
Liabilities [Abstract]
Derivative liabilities	7,119	4,628
Net embedded derivatives within liability host contracts	4,582	2,516
Recurring
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	69,977	61,348
Available-for-sale Securities, Equity Securities	147	140
Short-term investments, principally at estimated fair value	1,482
Derivative assets	3,005	2,765
Net embedded derivatives within asset host contracts	217	228
Separate account assets	99,668	91,511
Total assets	174,496	155,992
Liabilities [Abstract]
Derivative liabilities	2,537	2,112
Net embedded derivatives within liability host contracts	4,582	2,516
Total liabilities	7,119	4,628
Recurring | Interest rate
Assets [Abstract]
Derivative assets	1,778	717
Liabilities [Abstract]
Derivative liabilities	330	619
Recurring | Foreign currency exchange rate
Assets [Abstract]
Derivative assets	270	299
Liabilities [Abstract]
Derivative liabilities	43	48
Recurring | Credit
Assets [Abstract]
Derivative assets	36	17
Liabilities [Abstract]
Derivative liabilities		3
Recurring | Equity market
Assets [Abstract]
Derivative assets	921	1,732
Liabilities [Abstract]
Derivative liabilities	2,164	1,442
Recurring | U.S. corporate
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	30,591	24,059
Recurring | Foreign corporate
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	9,686	7,895
Recurring | RMBS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	9,030	8,435
Recurring | U.S. government and agency
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	7,244	8,644
Recurring | CMBS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	5,714	5,133
Recurring | State and political subdivision
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	4,011	3,586
Recurring | ABS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	1,950	2,111
Recurring | Foreign government
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	1,751	1,485
Recurring | Level 1
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	1,542	2,334
Available-for-sale Securities, Equity Securities	14	13
Short-term investments, principally at estimated fair value	1,004
Derivative assets	0	0
Net embedded derivatives within asset host contracts	0	0
Separate account assets	180	217
Total assets	2,740	2,564
Liabilities [Abstract]
Derivative liabilities	0	0
Net embedded derivatives within liability host contracts	0	0
Total liabilities	0	0
Recurring | Level 1 | Interest rate
Assets [Abstract]
Derivative assets	0	0
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 1 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets	0	0
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 1 | Credit
Assets [Abstract]
Derivative assets	0	0
Liabilities [Abstract]
Derivative liabilities		0
Recurring | Level 1 | Equity market
Assets [Abstract]
Derivative assets	0	0
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 1 | U.S. corporate
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	0	0
Recurring | Level 1 | Foreign corporate
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	0	0
Recurring | Level 1 | RMBS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	0	0
Recurring | Level 1 | U.S. government and agency
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	1,542	2,334
Recurring | Level 1 | CMBS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	0	0
Recurring | Level 1 | State and political subdivision
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	0	0
Recurring | Level 1 | ABS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	0	0
Recurring | Level 1 | Foreign government
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	0	0
Recurring | Level 2
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	67,788	58,055
Available-for-sale Securities, Equity Securities	125	124
Short-term investments, principally at estimated fair value	473
Derivative assets	2,918	2,649
Net embedded derivatives within asset host contracts	0	0
Separate account assets	99,485	91,293
Total assets	170,789	152,121
Liabilities [Abstract]
Derivative liabilities	2,466	1,874
Net embedded derivatives within liability host contracts	0	0
Total liabilities	2,466	1,874
Recurring | Level 2 | Interest rate
Assets [Abstract]
Derivative assets	1,778	717
Liabilities [Abstract]
Derivative liabilities	330	619
Recurring | Level 2 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets	265	288
Liabilities [Abstract]
Derivative liabilities	43	48
Recurring | Level 2 | Credit
Assets [Abstract]
Derivative assets	25	10
Liabilities [Abstract]
Derivative liabilities		2
Recurring | Level 2 | Equity market
Assets [Abstract]
Derivative assets	850	1,634
Liabilities [Abstract]
Derivative liabilities	2,093	1,205
Recurring | Level 2 | U.S. corporate
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	30,266	23,740
Recurring | Level 2 | Foreign corporate
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	9,554	7,503
Recurring | Level 2 | RMBS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	8,986	8,429
Recurring | Level 2 | U.S. government and agency
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	5,702	6,310
Recurring | Level 2 | CMBS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	5,714	5,004
Recurring | Level 2 | State and political subdivision
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	3,938	3,512
Recurring | Level 2 | ABS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	1,877	2,072
Recurring | Level 2 | Foreign government
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	1,751	1,485
Recurring | Level 3
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	647	959
Available-for-sale Securities, Equity Securities	8	3
Short-term investments, principally at estimated fair value	5
Derivative assets	87	116
Net embedded derivatives within asset host contracts	217	228
Separate account assets	3	1
Total assets	967	1,307
Liabilities [Abstract]
Derivative liabilities	71	238
Net embedded derivatives within liability host contracts	4,582	2,516
Total liabilities	4,653	2,754
Recurring | Level 3 | Interest rate
Assets [Abstract]
Derivative assets	0	0
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 3 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets	5	11
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 3 | Credit
Assets [Abstract]
Derivative assets	11	7
Liabilities [Abstract]
Derivative liabilities		1
Recurring | Level 3 | Equity market
Assets [Abstract]
Derivative assets	71	98
Liabilities [Abstract]
Derivative liabilities	71	237
Recurring | Level 3 | U.S. corporate
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	325	319
Recurring | Level 3 | Foreign corporate
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	132	392
Recurring | Level 3 | RMBS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	44	6
Recurring | Level 3 | U.S. government and agency
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	0	0
Recurring | Level 3 | CMBS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	0	129
Recurring | Level 3 | State and political subdivision
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	73	74
Recurring | Level 3 | ABS
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	73	39
Recurring | Level 3 | Foreign government
Assets [Abstract]
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $63,083 and $59,672, respectively)	$ 0	$ 0