Securities - Amortized Costs, Fair Value (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale Debt Securities:
Amortized cost	$ 288,466	$ 322,253
Gross unrealized gains	8,143	7,198
Gross unrealized losses	387	2,616
Fair value	296,222	326,835
Available-for-sale Equity Securities:
Amortized cost	2,513	3,125
Gross unrealized gains	17	17
Gross unrealized losses	0	0
Fair value	2,530	3,142
Available-for-sale Securities:
Amortized cost	290,979	325,378
Gross unrealized gains	8,160	7,215
Gross unrealized losses	387	2,616
Fair value	298,752	329,977
Held-to-maturity Securities:
Amortized cost	49,252	24,026
Gross unrealized gains	1,902	22
Gross unrealized losses	0	317
Fair value	51,154	23,731
Debt securities
Available-for-sale Debt Securities:
Amortized cost	288,466
Fair value	296,222
Mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	133,598	153,419
Gross unrealized gains	3,842	4,322
Gross unrealized losses	118	1,032
Fair value	137,322	156,709
Mortgage-backed securities, U.S. government agencies
Available-for-sale Debt Securities:
Amortized cost	63,089	76,428
Gross unrealized gains	2,302	2,364
Gross unrealized losses	72	977
Fair value	65,319	77,815
Mortgage-backed securities, Commercial
Available-for-sale Debt Securities:
Amortized cost	20,687	15,891
Gross unrealized gains	438	560
Gross unrealized losses	17	26
Fair value	21,108	16,425
U.S. Treasury and government agencies
Available-for-sale Debt Securities:
Amortized cost	13,603	21,310
Gross unrealized gains	56	385
Gross unrealized losses	14	306
Fair value	13,645	21,389
Obligations of U.S. states and municipalities
Available-for-sale Debt Securities:
Amortized cost	27,841	29,741
Gross unrealized gains	2,243	707
Gross unrealized losses	16	987
Fair value	30,068	29,461
Held-to-maturity Securities:
Amortized cost	10,200	920
Certificates of deposit
Available-for-sale Debt Securities:
Amortized cost	1,103	1,041
Gross unrealized gains	1	1
Gross unrealized losses	1	1
Fair value	1,103	1,041
Non-U.S. government debt securities
Available-for-sale Debt Securities:
Amortized cost	51,492	55,507
Gross unrealized gains	1,272	863
Gross unrealized losses	21	122
Fair value	52,743	56,248
Corporate debt securities
Available-for-sale Debt Securities:
Amortized cost	18,158	21,043
Gross unrealized gains	398	498
Gross unrealized losses	24	29
Fair value	18,532	21,512
Asset-backed securities, Collateralized loan obligations
Available-for-sale Debt Securities:
Amortized cost	30,229	28,130
Gross unrealized gains	147	236
Gross unrealized losses	182	136
Fair value	30,194	28,230
Asset-backed securities, Other
Available-for-sale Debt Securities:
Amortized cost	12,442	12,062
Gross unrealized gains	184	186
Gross unrealized losses	11	3
Fair value	12,615	12,245
US government-sponsored and enterprises obligations
Available-for-sale Securities:
Fair value	59,300	67,000
Held-to-maturity Securities:
Amortized cost	35,300	23,100
US Government Corporations and Agencies
Held-to-maturity Securities:
Amortized cost	3,700
Residential mortgage-backed securities | Residential mortgage-backed securities, Prime and Alt-A
Available-for-sale Debt Securities:
Amortized cost	5,595	2,744
Gross unrealized gains	78	61
Gross unrealized losses	29	27
Fair value	5,644	2,778
Residential mortgage-backed securities | Residential mortgage-backed securities, Subprime
Available-for-sale Debt Securities:
Amortized cost	677	908
Gross unrealized gains	14	23
Gross unrealized losses	0	1
Fair value	691	930
Residential mortgage-backed securities | Residential mortgage-backed securities, Non-U.S.
Available-for-sale Debt Securities:
Amortized cost	43,550	57,448
Gross unrealized gains	1,010	1,314
Gross unrealized losses	0	1
Fair value	$ 44,560	$ 58,761