Loans - Wholesale Loan Portfolio - Impaired Loans (Details) - Wholesale - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Impaired loans
With an allowance	$ 1,070	$ 1,509
Without an allowance	180	358
Total impaired loans	1,250	1,867
Allowance for loan losses related to impaired loans	297	461
Unpaid principal balance of impaired loans	1,723	2,154
Average impaired loans	1,416	1,710	$ 1,923
Troubled debt restructurings	576	614
Commercial and industrial
Impaired loans
With an allowance	807	1,170
Without an allowance	140	228
Total impaired loans	947	1,398
Allowance for loan losses related to impaired loans	252	404
Unpaid principal balance of impaired loans	1,043	1,604
Average impaired loans	1,027	1,256	1,480
Real estate
Impaired loans
With an allowance	107	78
Without an allowance	27	60
Total impaired loans	134	138
Allowance for loan losses related to impaired loans	25	11
Unpaid principal balance of impaired loans	203	201
Average impaired loans	133	165	217
Financial institutions
Impaired loans
With an allowance	4	93
Without an allowance	0	0
Total impaired loans	4	93
Allowance for loan losses related to impaired loans	1	4
Unpaid principal balance of impaired loans	4	94
Average impaired loans	57	48	13
Governments & Agencies
Impaired loans
With an allowance	0	0
Without an allowance	0	0
Total impaired loans	0	0
Allowance for loan losses related to impaired loans	0	0
Unpaid principal balance of impaired loans	0	0
Average impaired loans	0	0	0
Other
Impaired loans
With an allowance	152	168
Without an allowance	13	70
Total impaired loans	165	238
Allowance for loan losses related to impaired loans	19	42
Unpaid principal balance of impaired loans	473	255
Average impaired loans	$ 199	$ 241	$ 213