Securities - Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Held-to-maturity Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	$ 4,824	$ 0
Less than 12 months, Gross unrealized losses	48	0
12 months or more, Fair value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	4,824	0
Total gross unrealized losses	48	0
Investment Securities, Continuous Unrealized Loss Position:
Less than 12 months, Fair value	63,225	41,720
Less than 12 months, Gross unrealized losses	753	173
12 months or more, Fair value	12,708	15,614
12 months or more, Gross unrealized losses	146	214
Total fair value	75,933	57,334
Total gross unrealized losses	899	387
Debt securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	58,401	41,720
Less than 12 months, Gross unrealized losses	705	173
12 months or more, Fair Value	12,708	15,614
12 months or more, Gross unrealized losses	146	214
Total fair value	71,109	57,334
Total gross unrealized losses	851	387
Total mortgage-backed securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	18,824	7,761
Less than 12 months, Gross unrealized losses	197	30
12 months or more, Fair Value	1,237	5,486
12 months or more, Gross unrealized losses	21	88
Total fair value	20,061	13,247
Total gross unrealized losses	218	118
U.S. government agencies
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	4,797	1,118
Less than 12 months, Gross unrealized losses	19	5
12 months or more, Fair Value	717	4,989
12 months or more, Gross unrealized losses	14	67
Total fair value	5,514	6,107
Total gross unrealized losses	33	72
Residential, Prime and Alt-A | Residential mortgage-backed securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	2,294	1,840
Less than 12 months, Gross unrealized losses	14	10
12 months or more, Fair Value	251	405
12 months or more, Gross unrealized losses	5	19
Total fair value	2,545	2,245
Total gross unrealized losses	19	29
Residential, Subprime | Residential mortgage-backed securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	0	0
Less than 12 months, Gross unrealized losses	0	0
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	0	0
Total gross unrealized losses	0	0
Residential, Non-U.S. | Residential mortgage-backed securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	1,477	0
Less than 12 months, Gross unrealized losses	9	0
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	1,477	0
Total gross unrealized losses	9	0
Commercial and other
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	10,256	4,803
Less than 12 months, Gross unrealized losses	155	15
12 months or more, Fair Value	269	92
12 months or more, Gross unrealized losses	2	2
Total fair value	10,525	4,895
Total gross unrealized losses	157	17
U.S. Treasury and government agencies
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	11,205	8,412
Less than 12 months, Gross unrealized losses	136	14
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	11,205	8,412
Total gross unrealized losses	136	14
Obligations of U.S. states and municipalities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	4,681	1,405
Less than 12 months, Gross unrealized losses	79	15
12 months or more, Fair Value	218	130
12 months or more, Gross unrealized losses	7	1
Total fair value	4,899	1,535
Total gross unrealized losses	86	16
Certificates of deposit
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	0	1,050
Less than 12 months, Gross unrealized losses	0	1
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	0	1,050
Total gross unrealized losses	0	1
Non-U.S. government debt securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	2,941	4,433
Less than 12 months, Gross unrealized losses	30	4
12 months or more, Fair Value	205	906
12 months or more, Gross unrealized losses	7	17
Total fair value	3,146	5,339
Total gross unrealized losses	37	21
Corporate debt securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	4,107	2,492
Less than 12 months, Gross unrealized losses	142	22
12 months or more, Fair Value	634	80
12 months or more, Gross unrealized losses	9	2
Total fair value	4,741	2,572
Total gross unrealized losses	151	24
Asset-backed securities, Collateralized loan obligations
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	11,843	13,909
Less than 12 months, Gross unrealized losses	44	76
12 months or more, Fair Value	10,414	9,012
12 months or more, Gross unrealized losses	102	106
Total fair value	22,257	22,921
Total gross unrealized losses	146	182
Asset-backed securities, Other
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	4,800	2,258
Less than 12 months, Gross unrealized losses	77	11
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	4,800	2,258
Total gross unrealized losses	77	11
Available-for-sale equity securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	0	0
Less than 12 months, Gross unrealized losses	0	0
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	0	0
Total gross unrealized losses	$ 0	$ 0