Loans - Wholesale Loan Portfolio - Impaired Loans (Details) - Wholesale - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Commercial and industrial
Impaired loans:
With an allowance	$ 401		$ 401		$ 174
Without an allowance	102		102		24
Total impaired loans	503		503		198
Allowance for loan losses related to impaired loans	85		85		34
Unpaid principal balance of impaired loans	541		541		266
Average impaired loans	355	$ 249	303	$ 270
Real estate
Impaired loans:
With an allowance	154		154		193
Without an allowance	116		116		87
Total impaired loans	270		270		280
Allowance for loan losses related to impaired loans	17		17		36
Unpaid principal balance of impaired loans	354		354		345
Average impaired loans	242	306	255	330
Financial institutions
Impaired loans:
With an allowance	10		10		15
Without an allowance	2		2		3
Total impaired loans	12		12		18
Allowance for loan losses related to impaired loans	2		2		4
Unpaid principal balance of impaired loans	14		14		22
Average impaired loans	15	19	15	21
Government agencies
Impaired loans:
With an allowance	5		5		0
Without an allowance	0		0		0
Total impaired loans	5		5		0
Allowance for loan losses related to impaired loans	2		2		0
Unpaid principal balance of impaired loans	5		5		0
Average impaired loans	1	0	1	0
Other
Impaired loans:
With an allowance	59		59		89
Without an allowance	59		59		52
Total impaired loans	118		118		141
Allowance for loan losses related to impaired loans	41		41		13
Unpaid principal balance of impaired loans	122		122		202
Average impaired loans	114	159	111	164
Commercial loan
Impaired loans:
With an allowance	629		629		471
Without an allowance	279		279		166
Total impaired loans	908		908		637
Allowance for loan losses related to impaired loans	147		147		87
Unpaid principal balance of impaired loans	1,036		1,036		$ 835
Average impaired loans	$ 727	$ 733	$ 685	$ 785