Securities - Continuous Unrealized Loss Position (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Held-to-maturity Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	$ 3,763	$ 0
Less than 12 months, Gross unrealized losses	46	0
12 months or more, Fair value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	3,763	0
Total gross unrealized losses	46	0
Investment Securities, Continuous Unrealized Loss Position:
Less than 12 months, Fair value	76,475	41,720
Less than 12 months, Gross unrealized losses	905	173
12 months or more, Fair value	14,877	15,614
12 months or more, Gross unrealized losses	251	214
Total fair value	91,352	57,334
Total gross unrealized losses	1,156	387
Debt securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	72,712	41,720
Less than 12 months, Gross unrealized losses	859	173
12 months or more, Fair Value	14,877	15,614
12 months or more, Gross unrealized losses	251	214
Total fair value	87,589	57,334
Total gross unrealized losses	1,110	387
Total mortgage-backed securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	33,949	7,761
Less than 12 months, Gross unrealized losses	397	30
12 months or more, Fair Value	1,760	5,486
12 months or more, Gross unrealized losses	22	88
Total fair value	35,709	13,247
Total gross unrealized losses	419	118
U.S. government agencies
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	13,002	1,118
Less than 12 months, Gross unrealized losses	95	5
12 months or more, Fair Value	697	4,989
12 months or more, Gross unrealized losses	11	67
Total fair value	13,699	6,107
Total gross unrealized losses	106	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	5,147	1,840
Less than 12 months, Gross unrealized losses	51	10
12 months or more, Fair Value	238	405
12 months or more, Gross unrealized losses	6	19
Total fair value	5,385	2,245
Total gross unrealized losses	57	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	2,021	0
Less than 12 months, Gross unrealized losses	12	0
12 months or more, Fair Value	167	0
12 months or more, Gross unrealized losses	1	0
Total fair value	2,188	0
Total gross unrealized losses	13	0
Commercial
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	13,779	4,803
Less than 12 months, Gross unrealized losses	239	15
12 months or more, Fair Value	658	92
12 months or more, Gross unrealized losses	4	2
Total fair value	14,437	4,895
Total gross unrealized losses	243	17
U.S. Treasury and government agencies
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	10,998	8,412
Less than 12 months, Gross unrealized losses	166	14
12 months or more, Fair Value	0	0
12 months or more, Gross unrealized losses	0	0
Total fair value	10,998	8,412
Total gross unrealized losses	166	14
Obligations of U.S. states and municipalities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	1,676	1,405
Less than 12 months, Gross unrealized losses	18	15
12 months or more, Fair Value	205	130
12 months or more, Gross unrealized losses	5	1
Total fair value	1,881	1,535
Total gross unrealized losses	23	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	3,267	4,433
Less than 12 months, Gross unrealized losses	26	4
12 months or more, Fair Value	367	906
12 months or more, Gross unrealized losses	15	17
Total fair value	3,634	5,339
Total gross unrealized losses	41	21
Corporate debt securities
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	3,198	2,492
Less than 12 months, Gross unrealized losses	125	22
12 months or more, Fair Value	848	80
12 months or more, Gross unrealized losses	45	2
Total fair value	4,046	2,572
Total gross unrealized losses	170	24
Asset-backed securities: Collateralized loan obligations
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	15,340	13,909
Less than 12 months, Gross unrealized losses	67	76
12 months or more, Fair Value	10,692	9,012
12 months or more, Gross unrealized losses	124	106
Total fair value	26,032	22,921
Total gross unrealized losses	191	182
Asset-backed securities: Other
Available-for-sale Securities, Securities with Gross Unrealized Losses:
Less than 12 months, Fair value	4,284	2,258
Less than 12 months, Gross unrealized losses	60	11
12 months or more, Fair Value	1,005	0
12 months or more, Gross unrealized losses	40	0
Total fair value	5,289	2,258
Total gross unrealized losses	100	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