Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Assets [Abstract]
Debt Securities, Available-for-sale	$ 318,689	$ 298,265
Equity securities	1,476	1,440
Debt Securities, Trading, and Equity Securities, FV-NI	13,000	12,616
Short-term investments	2,811	3,937
Residential mortgage loans - FVO	77,997	75,752
Derivative assets	10,631	8,969
Separate account assets	191,264	175,556
Liabilities [Abstract]
Derivative liabilities	3,323	3,930
Embedded derivatives within liability host contracts	910	810
Separate account liabilities	191,264	175,556
Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	262	299
Recurring
Assets [Abstract]
Debt Securities, Available-for-sale	318,689	298,265
Equity securities	1,476	1,440
Debt Securities, Trading, and Equity Securities, FV-NI	13,000	12,616
Short-term investments	2,139	3,249
Other investments	453	237
Derivative assets	10,631	8,969
Embedded derivatives within asset host contracts	75	71
Separate account assets	191,264	175,556
Total assets (6)	537,989	500,702
Liabilities [Abstract]
Derivative liabilities	3,323	3,930
Embedded derivatives within liability host contracts	910	810
Total liabilities	4,275	4,768
Recurring | Interest rate contracts
Assets [Abstract]
Derivative assets	6,649	4,843
Liabilities [Abstract]
Derivative liabilities	201	415
Recurring | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	2,971	2,978
Liabilities [Abstract]
Derivative liabilities	2,252	2,749
Recurring | Credit contracts
Assets [Abstract]
Derivative assets	274	120
Liabilities [Abstract]
Derivative liabilities	75	52
Recurring | Equity market contracts
Assets [Abstract]
Derivative assets	737	1,028
Liabilities [Abstract]
Derivative liabilities	795	714
Recurring | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	42	28
Recurring | Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	262	299
Recurring | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	83,712	78,948
Recurring | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	67,554	62,288
Recurring | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	62,398	56,703
Recurring | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	40,003	39,322
Recurring | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	29,049	27,961
Recurring | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	13,712	12,472
Recurring | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	12,255	11,533
Recurring | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	10,006	9,038
Recurring | Level 1
Assets [Abstract]
Debt Securities, Available-for-sale	20,467	19,656
Equity securities	917	916
Debt Securities, Trading, and Equity Securities, FV-NI	10,513	10,216
Short-term investments	783	1,470
Other investments	76	80
Derivative assets	4	18
Embedded derivatives within asset host contracts	0	0
Separate account assets	88,675	79,726
Total assets (6)	121,435	112,082
Liabilities [Abstract]
Derivative liabilities	28	80
Embedded derivatives within liability host contracts	0	0
Total liabilities	30	81
Recurring | Level 1 | Interest rate contracts
Assets [Abstract]
Derivative assets	0	1
Liabilities [Abstract]
Derivative liabilities	0	3
Recurring | Level 1 | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	0	4
Liabilities [Abstract]
Derivative liabilities	6	0
Recurring | Level 1 | Credit contracts
Assets [Abstract]
Derivative assets	0	0
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 1 | Equity market contracts
Assets [Abstract]
Derivative assets	4	13
Liabilities [Abstract]
Derivative liabilities	22	77
Recurring | Level 1 | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	2	1
Recurring | Level 1 | Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	0	0
Recurring | Level 1 | U.S. corporate
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 1 | Foreign 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	20,447	19,656
Recurring | Level 1 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	20	0
Recurring | Level 1 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 1 | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 1 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 2
Assets [Abstract]
Debt Securities, Available-for-sale	282,310	263,738
Equity securities	102	105
Debt Securities, Trading, and Equity Securities, FV-NI	1,993	1,995
Short-term investments	1,233	1,746
Other investments	145	118
Derivative assets	10,359	8,778
Embedded derivatives within asset host contracts	0	0
Separate account assets	101,657	94,886
Total assets (6)	397,799	371,366
Liabilities [Abstract]
Derivative liabilities	3,132	3,452
Embedded derivatives within liability host contracts	0	0
Total liabilities	3,165	3,472
Recurring | Level 2 | Interest rate contracts
Assets [Abstract]
Derivative assets	6,546	4,809
Liabilities [Abstract]
Derivative liabilities	182	194
Recurring | Level 2 | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	2,892	2,922
Liabilities [Abstract]
Derivative liabilities	2,196	2,660
Recurring | Level 2 | Credit contracts
Assets [Abstract]
Derivative assets	238	91
Liabilities [Abstract]
Derivative liabilities	75	48
Recurring | Level 2 | Equity market contracts
Assets [Abstract]
Derivative assets	683	956
Liabilities [Abstract]
Derivative liabilities	679	550
Recurring | Level 2 | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	33	20
Recurring | Level 2 | Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	0	0
Recurring | Level 2 | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	79,372	74,874
Recurring | Level 2 | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	67,411	62,150
Recurring | Level 2 | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	55,131	50,310
Recurring | Level 2 | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	19,556	19,666
Recurring | Level 2 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	25,846	24,734
Recurring | Level 2 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	13,130	11,775
Recurring | Level 2 | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	12,248	11,533
Recurring | Level 2 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	9,616	8,696
Recurring | Level 3
Assets [Abstract]
Debt Securities, Available-for-sale	15,912	14,871
Equity securities	457	419
Debt Securities, Trading, and Equity Securities, FV-NI	494	405
Short-term investments	123	33
Other investments	232	39
Derivative assets	268	173
Embedded derivatives within asset host contracts	75	71
Separate account assets	932	944
Total assets (6)	18,755	17,254
Liabilities [Abstract]
Derivative liabilities	163	398
Embedded derivatives within liability host contracts	910	810
Total liabilities	1,080	1,215
Recurring | Level 3 | Interest rate contracts
Assets [Abstract]
Derivative assets	103	33
Liabilities [Abstract]
Derivative liabilities	19	218
Recurring | Level 3 | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	79	52
Liabilities [Abstract]
Derivative liabilities	50	89
Recurring | Level 3 | Credit contracts
Assets [Abstract]
Derivative assets	36	29
Liabilities [Abstract]
Derivative liabilities	0	4
Recurring | Level 3 | Equity market contracts
Assets [Abstract]
Derivative assets	50	59
Liabilities [Abstract]
Derivative liabilities	94	87
Recurring | Level 3 | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	7	7
Recurring | Level 3 | Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	262	299
Recurring | Level 3 | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	4,340	4,074
Recurring | Level 3 | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	143	138
Recurring | Level 3 | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	7,267	6,393
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	3,183	3,227
Recurring | Level 3 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	582	697
Recurring | Level 3 | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	7	0
Recurring | Level 3 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	390	342
Partnership Interest [Member] | Recurring
Assets [Abstract]
Investments, Fair Value Disclosure	$ 110	$ 145