Loans - Wholesale Loan Portfolio - Impaired Loans (Details) - Wholesale - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Commercial and industrial
Impaired loans:
With an allowance	$ 578		$ 578		$ 174
Without an allowance	94		94		24
Total impaired loans	672		672		198
Allowance for loan losses related to impaired loans	216		216		34
Unpaid principal balance of impaired loans	721		721		266
Average impaired loans	559	$ 245	388	$ 262
Real estate
Impaired loans:
With an allowance	167		167		193
Without an allowance	124		124		87
Total impaired loans	291		291		280
Allowance for loan losses related to impaired loans	20		20		36
Unpaid principal balance of impaired loans	356		356		345
Average impaired loans	261	287	257	316
Financial institutions
Impaired loans:
With an allowance	10		10		15
Without an allowance	1		1		3
Total impaired loans	11		11		18
Allowance for loan losses related to impaired loans	2		2		4
Unpaid principal balance of impaired loans	14		14		22
Average impaired loans	12	17	14	19
Government agencies
Impaired loans:
With an allowance	0		0		0
Without an allowance	0		0		0
Total impaired loans	0		0		0
Allowance for loan losses related to impaired loans	0		0		0
Unpaid principal balance of impaired loans	0		0		0
Average impaired loans	0	0	1	0
Other
Impaired loans:
With an allowance	86		86		89
Without an allowance	61		61		52
Total impaired loans	147		147		141
Allowance for loan losses related to impaired loans	43		43		13
Unpaid principal balance of impaired loans	151		151		202
Average impaired loans	122	162	114	163
Commercial mortgage
Impaired loans:
With an allowance	841		841		471
Without an allowance	280		280		166
Total impaired loans	1,121		1,121		637
Allowance for loan losses related to impaired loans	281		281		87
Unpaid principal balance of impaired loans	1,242		1,242		$ 835
Average impaired loans	$ 954	$ 711	$ 774	$ 760