Securities - Amortized Costs, Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Available-for-sale Debt Securities:
Amortized cost	$ 257,916	$ 288,466
Gross unrealized gains	6,204	8,143
Gross unrealized losses	640	387
Fair value	263,480	296,222
Available-for-sale Equity Securities:
Amortized cost	2,704	2,513
Gross unrealized gains	17	17
Gross unrealized losses	0	0
Fair value	2,721	2,530
Available-for-sale Securities:
Amortized cost	260,620	290,979
Gross unrealized gains	6,221	8,160
Gross unrealized losses	640	387
Fair value	266,201	298,752
Held-to-maturity Securities:
Amortized cost	51,594	49,252
Gross unrealized gains	1,241	1,902
Gross unrealized losses	138	0
Fair value	52,697	51,154
Mortgage-backed securities
Available-for-sale Debt Securities:
Amortized cost	116,358	133,598
Gross unrealized gains	3,024	3,842
Gross unrealized losses	287	118
Fair value	119,095	137,322
Mortgage-backed securities, U.S. government agencies
Available-for-sale Debt Securities:
Amortized cost	55,634	63,089
Gross unrealized gains	1,887	2,302
Gross unrealized losses	206	72
Fair value	57,315	65,319
Mortgage-backed securities, Commercial
Available-for-sale Debt Securities:
Amortized cost	21,954	20,687
Gross unrealized gains	308	438
Gross unrealized losses	55	17
Fair value	22,207	21,108
U.S. Treasury and government agencies
Available-for-sale Debt Securities:
Amortized cost	11,600	13,603
Gross unrealized gains	16	56
Gross unrealized losses	26	14
Fair value	11,590	13,645
Obligations of U.S. states and municipalities
Available-for-sale Debt Securities:
Amortized cost	29,986	27,841
Gross unrealized gains	1,609	2,243
Gross unrealized losses	171	16
Fair value	31,424	30,068
Held-to-maturity Securities:
Amortized cost	12,400	10,200
Certificates of deposit
Available-for-sale Debt Securities:
Amortized cost	427	1,103
Gross unrealized gains	2	1
Gross unrealized losses	0	1
Fair value	429	1,103
Non-U.S. government debt securities
Available-for-sale Debt Securities:
Amortized cost	41,837	51,492
Gross unrealized gains	999	1,272
Gross unrealized losses	44	21
Fair value	42,792	52,743
Corporate debt securities
Available-for-sale Debt Securities:
Amortized cost	15,540	18,158
Gross unrealized gains	310	398
Gross unrealized losses	28	24
Fair value	15,822	18,532
Asset-backed securities, Collateralized loan obligations
Available-for-sale Debt Securities:
Amortized cost	31,337	30,229
Gross unrealized gains	108	147
Gross unrealized losses	73	182
Fair value	31,372	30,194
Asset-backed securities, Other
Available-for-sale Debt Securities:
Amortized cost	10,831	12,442
Gross unrealized gains	136	184
Gross unrealized losses	11	11
Fair value	10,956	12,615
US government-sponsored and enterprises obligations
Available-for-sale Securities:
Fair value	45,500	59,300
Held-to-maturity Securities:
Amortized cost	33,300	35,300
US Government Corporations and Agencies
Held-to-maturity Securities:
Amortized cost	5,900	3,700
Residential mortgage-backed securities | Residential mortgage-backed securities, Prime and Alt-A
Available-for-sale Debt Securities:
Amortized cost	6,499	5,595
Gross unrealized gains	55	78
Gross unrealized losses	21	29
Fair value	6,533	5,644
Residential mortgage-backed securities | Residential mortgage-backed securities, Subprime
Available-for-sale Debt Securities:
Amortized cost	494	677
Gross unrealized gains	11	14
Gross unrealized losses	0	0
Fair value	505	691
Residential mortgage-backed securities | Residential mortgage-backed securities, Non-U.S.
Available-for-sale Debt Securities:
Amortized cost	31,777	43,550
Gross unrealized gains	763	1,010
Gross unrealized losses	5	0
Fair value	$ 32,535	$ 44,560