Securities - Amortized Costs, Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Available-for-sale Debt Securities:
Amortized cost	$ 230,518	$ 235,391
Gross unrealized gains	6,061	5,386
Gross unrealized losses	1,100	1,110
Fair value	235,479	239,667
Available-for-sale Equity Securities:
Amortized cost	1,893	2,067
Gross unrealized gains	19	20
Gross unrealized losses	0	0
Fair value	1,912	2,087
Available-for-sale Securities:
Amortized cost	232,411	237,458
Gross unrealized gains	6,080	5,406
Gross unrealized losses	1,100	1,110
Fair value	237,391	241,754
Held-to-maturity Securities:
Amortized cost	47,932	49,073
Gross unrealized gains	2,236	1,560
Gross unrealized losses	0	46
Fair value	50,168	50,587
Total mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	102,418	103,980
Gross unrealized gains	2,392	2,021
Gross unrealized losses	334	419
Fair value	104,476	105,582
U.S. government agencies
Available-for-sale Debt Securities:
Amortized cost	54,099	53,689
Gross unrealized gains	1,811	1,483
Gross unrealized losses	26	106
Fair value	55,884	55,066
Residential: Prime and Alt-A | Residential mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	7,197	7,462
Gross unrealized gains	59	40
Gross unrealized losses	40	57
Fair value	7,216	7,445
Residential: Subprime | Residential mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	216	210
Gross unrealized gains	7	7
Gross unrealized losses	0	0
Fair value	223	217
Residential: Non-U.S. | Residential mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	18,228	19,629
Gross unrealized gains	297	341
Gross unrealized losses	21	13
Fair value	18,504	19,957
Commercial
Available-for-sale Debt Securities:
Amortized cost	22,678	22,990
Gross unrealized gains	218	150
Gross unrealized losses	247	243
Fair value	22,649	22,897
Held-to-maturity Securities:
Amortized cost	121
U.S. Treasury and government agencies
Available-for-sale Debt Securities:
Amortized cost	12,278	11,202
Gross unrealized gains	10	0
Gross unrealized losses	199	166
Fair value	12,089	11,036
Obligations of U.S. states and municipalities
Available-for-sale Debt Securities:
Amortized cost	30,871	31,328
Gross unrealized gains	2,498	2,245
Gross unrealized losses	19	23
Fair value	33,350	33,550
Held-to-maturity Securities:
Amortized cost	12,800	12,800
Certificates of deposit
Available-for-sale Debt Securities:
Amortized cost	52	282
Gross unrealized gains	1	1
Gross unrealized losses	0	0
Fair value	53	283
Non-U.S. government debt securities
Available-for-sale Debt Securities:
Amortized cost	36,850	35,864
Gross unrealized gains	980	853
Gross unrealized losses	39	41
Fair value	37,791	36,676
Corporate debt securities
Available-for-sale Debt Securities:
Amortized cost	8,091	12,464
Gross unrealized gains	81	142
Gross unrealized losses	121	170
Fair value	8,051	12,436
Asset-backed securities: Collateralized loan obligations
Available-for-sale Debt Securities:
Amortized cost	31,374	31,146
Gross unrealized gains	42	52
Gross unrealized losses	272	191
Fair value	31,144	31,007
Asset-backed securities: Other
Available-for-sale Debt Securities:
Amortized cost	8,584	9,125
Gross unrealized gains	57	72
Gross unrealized losses	116	100
Fair value	8,525	9,097
U.S. government-sponsored enterprise obligations
Available-for-sale Securities:
Fair value	38,500	42,300
Held-to-maturity Securities:
Amortized cost	29,800	30,800
U.S. government agencies
Held-to-maturity Securities:
Amortized cost	$ 5,300	$ 5,500