Securities - Amortized Costs, Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale Debt Securities:
Amortized cost	$ 248,775	$ 288,466
Gross unrealized gains	5,962	8,143
Gross unrealized losses	851	387
Fair value	253,886	296,222
Available-for-sale Equity Securities:
Amortized cost	2,587	2,513
Gross unrealized gains	18	17
Gross unrealized losses	0	0
Fair value	2,605	2,530
Available-for-sale Securities:
Amortized cost	251,362	290,979
Gross unrealized gains	5,980	8,160
Gross unrealized losses	851	387
Fair value	256,491	298,752
Held-to-maturity Securities:
Amortized cost	50,169	49,252
Gross unrealized gains	1,724	1,902
Gross unrealized losses	48	0
Fair value	51,845	51,154
Total mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	111,516	133,598
Gross unrealized gains	2,778	3,842
Gross unrealized losses	218	118
Fair value	114,076	137,322
U.S. government agencies
Available-for-sale Debt Securities:
Amortized cost	52,800	63,089
Gross unrealized gains	1,811	2,302
Gross unrealized losses	33	72
Fair value	54,578	65,319
Commercial and other
Available-for-sale Debt Securities:
Amortized cost	22,763	20,687
Gross unrealized gains	287	438
Gross unrealized losses	157	17
Fair value	22,893	21,108
U.S. Treasury and government agencies
Available-for-sale Debt Securities:
Amortized cost	11,482	13,603
Gross unrealized gains	1	56
Gross unrealized losses	136	14
Fair value	11,347	13,645
Obligations of U.S. states and municipalities
Available-for-sale Debt Securities:
Amortized cost	30,923	27,841
Gross unrealized gains	1,872	2,243
Gross unrealized losses	86	16
Fair value	32,709	30,068
Held-to-maturity Securities:
Amortized cost	12,700	10,200
Certificates of deposit
Available-for-sale Debt Securities:
Amortized cost	415	1,103
Gross unrealized gains	3	1
Gross unrealized losses	0	1
Fair value	418	1,103
Non-U.S. government debt securities
Available-for-sale Debt Securities:
Amortized cost	38,197	51,492
Gross unrealized gains	960	1,272
Gross unrealized losses	37	21
Fair value	39,120	52,743
Corporate debt securities
Available-for-sale Debt Securities:
Amortized cost	14,747	18,158
Gross unrealized gains	185	398
Gross unrealized losses	151	24
Fair value	14,781	18,532
Asset-backed securities, Collateralized loan obligations
Available-for-sale Debt Securities:
Amortized cost	31,381	30,229
Gross unrealized gains	69	147
Gross unrealized losses	146	182
Fair value	31,304	30,194
Asset-backed securities, Other
Available-for-sale Debt Securities:
Amortized cost	10,114	12,442
Gross unrealized gains	94	184
Gross unrealized losses	77	11
Fair value	10,131	12,615
US government-sponsored and enterprises obligations
Available-for-sale Securities:
Fair value	41,600	59,300
Held-to-maturity Securities:
Amortized cost	31,900	35,300
US Government Corporations and Agencies
Held-to-maturity Securities:
Amortized cost	5,600	3,700
Residential mortgage-backed securities | Residential, Prime and Alt-A
Available-for-sale Debt Securities:
Amortized cost	6,811	5,595
Gross unrealized gains	66	78
Gross unrealized losses	19	29
Fair value	6,858	5,644
Residential mortgage-backed securities | Residential, Subprime
Available-for-sale Debt Securities:
Amortized cost	301	677
Gross unrealized gains	8	14
Gross unrealized losses	0	0
Fair value	309	691
Residential mortgage-backed securities | Residential, Non-U.S.
Available-for-sale Debt Securities:
Amortized cost	28,841	43,550
Gross unrealized gains	606	1,010
Gross unrealized losses	9	0
Fair value	$ 29,438	$ 44,560