Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets [Abstract]
Debt Securities, Available-for-sale	$ 308,410	$ 298,265
Equity securities	1,432	1,440
Debt Securities, Trading, and Equity Securities, FV-NI	13,245	12,616
Short-term investments	4,524	3,937
Residential mortgage loans - FVO	78,601	75,752
Derivative assets	8,822	8,969
Separate account assets	185,765	175,556
Liabilities [Abstract]
Derivative liabilities	3,816	3,930
Embedded derivatives within liability host contracts	674	810
Separate account liabilities	185,765	175,556
Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	276	299
Recurring
Assets [Abstract]
Debt Securities, Available-for-sale	308,410	298,265
Equity securities	1,432	1,440
Debt Securities, Trading, and Equity Securities, FV-NI	13,245	12,616
Short-term investments	3,820	3,249
Other investments	383	237
Derivative assets	8,822	8,969
Embedded derivatives within asset host contracts	69	71
Separate account assets	185,765	175,556
Total assets (6)	522,222	500,702
Liabilities [Abstract]
Derivative liabilities	3,816	3,930
Embedded derivatives within liability host contracts	674	810
Total liabilities	4,521	4,768
Recurring | Interest rate contracts
Assets [Abstract]
Derivative assets	5,429	4,843
Liabilities [Abstract]
Derivative liabilities	285	415
Recurring | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	2,468	2,978
Liabilities [Abstract]
Derivative liabilities	2,654	2,749
Recurring | Credit contracts
Assets [Abstract]
Derivative assets	215	120
Liabilities [Abstract]
Derivative liabilities	66	52
Recurring | Equity market contracts
Assets [Abstract]
Derivative assets	710	1,028
Liabilities [Abstract]
Derivative liabilities	811	714
Recurring | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	31	28
Recurring | Residential mortgage loans - FVO
Assets [Abstract]
Residential mortgage loans - FVO	276	299
Recurring | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	80,146	78,948
Recurring | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	64,955	62,288
Recurring | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	59,945	56,703
Recurring | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	41,008	39,322
Recurring | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	28,360	27,961
Recurring | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	12,631	12,472
Recurring | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	11,898	11,533
Recurring | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	9,467	9,038
Recurring | Level 1
Assets [Abstract]
Debt Securities, Available-for-sale	21,042	19,656
Equity securities	901	916
Debt Securities, Trading, and Equity Securities, FV-NI	10,780	10,216
Short-term investments	1,487	1,470
Other investments	81	80
Derivative assets	3	18
Embedded derivatives within asset host contracts	0	0
Separate account assets	84,812	79,726
Total assets (6)	119,106	112,082
Liabilities [Abstract]
Derivative liabilities	25	80
Embedded derivatives within liability host contracts	0	0
Total liabilities	26	81
Recurring | Level 1 | Interest rate contracts
Assets [Abstract]
Derivative assets	0	1
Liabilities [Abstract]
Derivative liabilities	4	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	3	13
Liabilities [Abstract]
Derivative liabilities	18	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	21,022	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	272,180	263,738
Equity securities	97	105
Debt Securities, Trading, and Equity Securities, FV-NI	2,008	1,995
Short-term investments	2,195	1,746
Other investments	134	118
Derivative assets	8,622	8,778
Embedded derivatives within asset host contracts	0	0
Separate account assets	100,049	94,886
Total assets (6)	385,285	371,366
Liabilities [Abstract]
Derivative liabilities	3,525	3,452
Embedded derivatives within liability host contracts	0	0
Total liabilities	3,548	3,472
Recurring | Level 2 | Interest rate contracts
Assets [Abstract]
Derivative assets	5,385	4,809
Liabilities [Abstract]
Derivative liabilities	164	194
Recurring | Level 2 | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	2,400	2,922
Liabilities [Abstract]
Derivative liabilities	2,595	2,660
Recurring | Level 2 | Credit contracts
Assets [Abstract]
Derivative assets	185	91
Liabilities [Abstract]
Derivative liabilities	65	48
Recurring | Level 2 | Equity market contracts
Assets [Abstract]
Derivative assets	652	956
Liabilities [Abstract]
Derivative liabilities	701	550
Recurring | Level 2 | Derivative Liabilities Within Separate Accounts
Liabilities [Abstract]
Separate account liabilities	23	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	75,935	74,874
Recurring | Level 2 | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	64,798	62,150
Recurring | Level 2 | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	53,194	50,310
Recurring | Level 2 | U.S. government and agency
Assets [Abstract]
Debt Securities, Available-for-sale	19,986	19,666
Recurring | Level 2 | RMBS
Assets [Abstract]
Debt Securities, Available-for-sale	25,102	24,734
Recurring | Level 2 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	12,167	11,775
Recurring | Level 2 | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	11,898	11,533
Recurring | Level 2 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	9,100	8,696
Recurring | Level 3
Assets [Abstract]
Debt Securities, Available-for-sale	15,188	14,871
Equity securities	434	419
Debt Securities, Trading, and Equity Securities, FV-NI	457	405
Short-term investments	138	33
Other investments	168	39
Derivative assets	197	173
Embedded derivatives within asset host contracts	69	71
Separate account assets	904	944
Total assets (6)	17,831	17,254
Liabilities [Abstract]
Derivative liabilities	266	398
Embedded derivatives within liability host contracts	674	810
Total liabilities	947	1,215
Recurring | Level 3 | Interest rate contracts
Assets [Abstract]
Derivative assets	44	33
Liabilities [Abstract]
Derivative liabilities	117	218
Recurring | Level 3 | Foreign currency exchange rate contracts
Assets [Abstract]
Derivative assets	68	52
Liabilities [Abstract]
Derivative liabilities	56	89
Recurring | Level 3 | Credit contracts
Assets [Abstract]
Derivative assets	30	29
Liabilities [Abstract]
Derivative liabilities	1	4
Recurring | Level 3 | Equity market contracts
Assets [Abstract]
Derivative assets	55	59
Liabilities [Abstract]
Derivative liabilities	92	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	276	299
Recurring | Level 3 | U.S. corporate
Assets [Abstract]
Debt Securities, Available-for-sale	4,211	4,074
Recurring | Level 3 | Foreign government
Assets [Abstract]
Debt Securities, Available-for-sale	157	138
Recurring | Level 3 | Foreign corporate
Assets [Abstract]
Debt Securities, Available-for-sale	6,751	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	3,238	3,227
Recurring | Level 3 | ABS
Assets [Abstract]
Debt Securities, Available-for-sale	464	697
Recurring | Level 3 | Municipals
Assets [Abstract]
Debt Securities, Available-for-sale	0	0
Recurring | Level 3 | CMBS
Assets [Abstract]
Debt Securities, Available-for-sale	367	342
Partnership Interest [Member] | Recurring
Assets [Abstract]
Investments, Fair Value Disclosure	$ 113	$ 145