Securities - Amortized Costs, Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Fair value of securities transferred from available-for-sale to held-to-maturity	$ 7,500
Net pre-tax unrealized gains in AOCI on securities on the date of transfer	78
Available-for-sale Debt Securities:
Amortized cost	235,516	$ 235,391
Gross unrealized gains	4,096	5,386
Gross unrealized losses	1,647	1,110
Fair value	237,965	239,667
Available-for-sale Equity Securities:
Amortized cost	914	2,067
Gross unrealized gains	12	20
Gross unrealized losses	0	0
Fair value	926	2,087
Available-for-sale Securities:
Amortized cost	236,430	237,458
Gross unrealized gains	4,108	5,406
Gross unrealized losses	1,647	1,110
Fair value	238,891	241,754
Held-to-maturity Securities:
Amortized cost	50,168	49,073
Gross unrealized gains	1,012	1,560
Gross unrealized losses	291	46
Fair value	50,889	50,587
Total Securities:
Amortized cost	286,598	286,531
Gross unrealized gains	5,120	6,966
Gross unrealized losses	1,938	1,156
Fair value	289,780	292,341
Total mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	86,589	103,980
Gross unrealized gains	1,492	2,021
Gross unrealized losses	529	419
Fair value	87,552	105,582
Held-to-maturity Securities:
Amortized cost	35,693	36,271
Gross unrealized gains	638	852
Gross unrealized losses	166	42
Fair value	36,165	37,081
U.S. government agencies
Available-for-sale Debt Securities:
Amortized cost	63,367	53,689
Gross unrealized gains	1,112	1,483
Gross unrealized losses	474	106
Fair value	64,005	55,066
Held-to-maturity Securities:
Amortized cost	29,910	36,271
Gross unrealized gains	638	852
Gross unrealized losses	37	42
Fair value	30,511	37,081
Residential: Prime and Alt-A | Residential mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	4,256	6,594
Gross unrealized gains	38	38
Gross unrealized losses	22	49
Fair value	4,272	6,583
Residential: Subprime | Residential mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	3,915	1,078
Gross unrealized gains	62	9
Gross unrealized losses	6	8
Fair value	3,971	1,079
Residential: Non-U.S. | Residential mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	6,049	19,629
Gross unrealized gains	158	341
Gross unrealized losses	7	13
Fair value	6,200	19,957
Commercial
Available-for-sale Debt Securities:
Amortized cost	9,002	22,990
Gross unrealized gains	122	150
Gross unrealized losses	20	243
Fair value	9,104	22,897
Held-to-maturity Securities:
Amortized cost	5,783	0
Gross unrealized gains	0	0
Gross unrealized losses	129	0
Fair value	5,654	0
U.S. Treasury and government agencies
Available-for-sale Debt Securities:
Amortized cost	44,822	11,202
Gross unrealized gains	75	0
Gross unrealized losses	796	166
Fair value	44,101	11,036
Obligations of U.S. states and municipalities
Available-for-sale Debt Securities:
Amortized cost	30,284	31,328
Gross unrealized gains	1,492	2,245
Gross unrealized losses	184	23
Fair value	31,592	33,550
Held-to-maturity Securities:
Amortized cost	14,475	12,802
Gross unrealized gains	374	708
Gross unrealized losses	125	4
Fair value	14,724	13,506
Certificates of deposit
Available-for-sale Debt Securities:
Amortized cost	106	282
Gross unrealized gains	0	1
Gross unrealized losses	0	0
Fair value	106	283
Non-U.S. government debt securities
Available-for-sale Debt Securities:
Amortized cost	34,497	35,864
Gross unrealized gains	836	853
Gross unrealized losses	45	41
Fair value	35,288	36,676
Corporate debt securities
Available-for-sale Debt Securities:
Amortized cost	4,916	12,464
Gross unrealized gains	64	142
Gross unrealized losses	22	170
Fair value	4,958	12,436
Asset-backed securities: Collateralized loan obligations
Available-for-sale Debt Securities:
Amortized cost	27,352	31,146
Gross unrealized gains	75	52
Gross unrealized losses	26	191
Fair value	27,401	31,007
Asset-backed securities: Other
Available-for-sale Debt Securities:
Amortized cost	6,950	9,125
Gross unrealized gains	62	72
Gross unrealized losses	45	100
Fair value	6,967	9,097
US government-sponsored and enterprises obligations
Available-for-sale Securities:
Fair value	45,800	42,300
Held-to-maturity Securities:
Amortized cost	$ 25,600	$ 30,800