Securities - Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Held-to-maturity Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	$ 7,447	$ 0
Less than 12 months, Gross unrealized losses	138	0
12 months or more, Fair value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	7,447	0
Total gross unrealized losses	138	0
Investment Securities, Continuous Unrealized Loss Position:
Less than 12 months, Fair value	59,783	41,720
Less than 12 months, Gross unrealized losses	669	173
12 months or more, Fair value	10,410	15,614
12 months or more, Gross unrealized losses	109	214
Total fair value	70,193	57,334
Total gross unrealized losses	778	387
Debt securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	52,336	41,720
Less than 12 months, Gross unrealized losses	531	173
12 months or more, Fair Value	10,410	15,614
12 months or more, Gross unrealized losses	109	214
Total fair value	62,746	57,334
Total gross unrealized losses	640	387
Mortgage-backed securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	19,450	7,761
Less than 12 months, Gross unrealized losses	262	30
12 months or more, Fair Value	1,228	5,486
12 months or more, Gross unrealized losses	25	88
Total fair value	20,678	13,247
Total gross unrealized losses	287	118
Mortgage-backed securities, U.S. government agencies
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	6,755	1,118
Less than 12 months, Gross unrealized losses	186	5
12 months or more, Fair Value	913	4,989
12 months or more, Gross unrealized losses	20	67
Total fair value	7,668	6,107
Total gross unrealized losses	206	72
Mortgage-backed securities, Commercial
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	8,607	4,803
Less than 12 months, Gross unrealized losses	55	15
12 months or more, Fair Value	0	92
12 months or more, Gross unrealized losses	0	2
Total fair value	8,607	4,895
Total gross unrealized losses	55	17
U.S. Treasury and government agencies
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	8,778	8,412
Less than 12 months, Gross unrealized losses	26	14
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	8,778	8,412
Total gross unrealized losses	26	14
Obligations of U.S. states and municipalities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	7,284	1,405
Less than 12 months, Gross unrealized losses	162	15
12 months or more, Fair Value	181	130
12 months or more, Gross unrealized losses	9	1
Total fair value	7,465	1,535
Total gross unrealized losses	171	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	3,527	4,433
Less than 12 months, Gross unrealized losses	35	4
12 months or more, Fair Value	240	906
12 months or more, Gross unrealized losses	9	17
Total fair value	3,767	5,339
Total gross unrealized losses	44	21
Corporate debt securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	1,963	2,492
Less than 12 months, Gross unrealized losses	23	22
12 months or more, Fair Value	549	80
12 months or more, Gross unrealized losses	5	2
Total fair value	2,512	2,572
Total gross unrealized losses	28	24
Asset-backed securities, Collateralized loan obligations
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	8,933	13,909
Less than 12 months, Gross unrealized losses	13	76
12 months or more, Fair Value	8,132	9,012
12 months or more, Gross unrealized losses	60	106
Total fair value	17,065	22,921
Total gross unrealized losses	73	182
Asset-backed securities, Other
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	2,401	2,258
Less than 12 months, Gross unrealized losses	10	11
12 months or more, Fair Value	80	0
12 months or more, Gross unrealized losses	1	0
Total fair value	2,481	2,258
Total gross unrealized losses	11	11
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
Residential mortgage-backed securities | Residential mortgage-backed securities, Prime and Alt-A
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	2,801	1,840
Less than 12 months, Gross unrealized losses	16	10
12 months or more, Fair Value	315	405
12 months or more, Gross unrealized losses	5	19
Total fair value	3,116	2,245
Total gross unrealized losses	21	29
Residential mortgage-backed securities | Residential mortgage-backed securities, Subprime
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 mortgage-backed securities | Residential mortgage-backed securities, Non-U.S.
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	1,287	0
Less than 12 months, Gross unrealized losses	5	0
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	1,287	0
Total gross unrealized losses	$ 5	$ 0