Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Assets [Abstract]
Debt Securities, Available-for-sale	$ 326,049	$ 298,265
Equity securities	1,341	1,440
Debt Securities, Trading, and Equity Securities, FV-NI	12,671	12,616
Short-term investments	3,536	3,937
Residential mortgage loans - FVO	78,959	75,752
Derivative assets	12,945	8,969
Separate account assets	190,357	175,556
Liabilities [Abstract]
Derivative liabilities	3,680	3,930
Embedded derivatives within liability host contracts	1,188	810
Separate account liabilities	190,357	175,556
Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	218	299
Recurring
Assets [Abstract]
Debt Securities, Available-for-sale	326,049	298,265
Equity securities	1,341	1,440
Debt Securities, Trading, and Equity Securities, FV-NI	12,671	12,616
Short-term investments	2,859	3,249
Other investments	547	237
Derivative assets	12,945	8,969
Embedded derivatives within asset host contracts	64	71
Separate account assets	190,357	175,556
Total assets (6)	547,051	500,702
Liabilities [Abstract]
Derivative liabilities	3,680	3,930
Embedded derivatives within liability host contracts	1,188	810
Total liabilities	4,908	4,768
Recurring | Interest rate contracts
Assets [Abstract]
Derivative assets	8,284	4,843
Liabilities [Abstract]
Derivative liabilities	228	415
Recurring | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	3,611	2,978
Liabilities [Abstract]
Derivative liabilities	2,570	2,749
Recurring | Credit contracts
Assets [Abstract]
Derivative assets	240	120
Liabilities [Abstract]
Derivative liabilities	86	52
Recurring | Equity market contracts
Assets [Abstract]
Derivative assets	810	1,028
Liabilities [Abstract]
Derivative liabilities	796	714
Recurring | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	40	28
Recurring | Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	218	299
Recurring | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	87,114	78,948
Recurring | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	67,547	62,288
Recurring | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	63,100	56,703
Recurring | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	40,802	39,322
Recurring | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	29,591	27,961
Recurring | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	14,345	12,472
Recurring | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	12,942	11,533
Recurring | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	10,608	9,038
Recurring | Level 1
Assets [Abstract]
Debt Securities, Available-for-sale	20,153	19,656
Equity securities	795	916
Debt Securities, Trading, and Equity Securities, FV-NI	10,270	10,216
Short-term investments	929	1,470
Other investments	73	80
Derivative assets	11	18
Embedded derivatives within asset host contracts	0	0
Separate account assets	88,435	79,726
Total assets (6)	120,666	112,082
Liabilities [Abstract]
Derivative liabilities	20	80
Embedded derivatives within liability host contracts	0	0
Total liabilities	21	81
Recurring | Level 1 | Interest rate contracts
Assets [Abstract]
Derivative assets	4	1
Liabilities [Abstract]
Derivative liabilities	1	3
Recurring | Level 1 | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	0	4
Liabilities [Abstract]
Derivative liabilities	3	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	7	13
Liabilities [Abstract]
Derivative liabilities	16	77
Recurring | Level 1 | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	1	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	20,145	19,656
Recurring | Level 1 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	8	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	288,510	263,738
Equity securities	109	105
Debt Securities, Trading, and Equity Securities, FV-NI	1,902	1,995
Short-term investments	1,556	1,746
Other investments	151	118
Derivative assets	12,493	8,778
Embedded derivatives within asset host contracts	0	0
Separate account assets	100,966	94,886
Total assets (6)	405,687	371,366
Liabilities [Abstract]
Derivative liabilities	3,460	3,452
Embedded derivatives within liability host contracts	0	0
Total liabilities	3,490	3,472
Recurring | Level 2 | Interest rate contracts
Assets [Abstract]
Derivative assets	7,989	4,809
Liabilities [Abstract]
Derivative liabilities	203	194
Recurring | Level 2 | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	3,542	2,922
Liabilities [Abstract]
Derivative liabilities	2,485	2,660
Recurring | Level 2 | Credit contracts
Assets [Abstract]
Derivative assets	208	91
Liabilities [Abstract]
Derivative liabilities	86	48
Recurring | Level 2 | Equity market contracts
Assets [Abstract]
Derivative assets	754	956
Liabilities [Abstract]
Derivative liabilities	686	550
Recurring | Level 2 | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	30	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	81,740	74,874
Recurring | Level 2 | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	67,410	62,150
Recurring | Level 2 | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	55,580	50,310
Recurring | Level 2 | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	20,657	19,666
Recurring | Level 2 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	26,406	24,734
Recurring | Level 2 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	13,521	11,775
Recurring | Level 2 | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	12,934	11,533
Recurring | Level 2 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	10,262	8,696
Recurring | Level 3
Assets [Abstract]
Debt Securities, Available-for-sale	17,386	14,871
Equity securities	437	419
Debt Securities, Trading, and Equity Securities, FV-NI	499	405
Short-term investments	374	33
Other investments	323	39
Derivative assets	441	173
Embedded derivatives within asset host contracts	64	71
Separate account assets	956	944
Total assets (6)	20,698	17,254
Liabilities [Abstract]
Derivative liabilities	200	398
Embedded derivatives within liability host contracts	1,188	810
Total liabilities	1,397	1,215
Recurring | Level 3 | Interest rate contracts
Assets [Abstract]
Derivative assets	291	33
Liabilities [Abstract]
Derivative liabilities	24	218
Recurring | Level 3 | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	69	52
Liabilities [Abstract]
Derivative liabilities	82	89
Recurring | Level 3 | Credit contracts
Assets [Abstract]
Derivative assets	32	29
Liabilities [Abstract]
Derivative liabilities	0	4
Recurring | Level 3 | Equity market contracts
Assets [Abstract]
Derivative assets	49	59
Liabilities [Abstract]
Derivative liabilities	94	87
Recurring | Level 3 | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	9	7
Recurring | Level 3 | Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	218	299
Recurring | Level 3 | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	5,374	4,074
Recurring | Level 3 | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	137	138
Recurring | Level 3 | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	7,520	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	3,177	3,227
Recurring | Level 3 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	824	697
Recurring | Level 3 | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	8	0
Recurring | Level 3 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	346	342
Partnership Interest [Member] | Recurring
Assets [Abstract]
Investments, Fair Value Disclosure	$ 103	$ 145