Loans - Wholesale Loan Portfolio - Impaired Loans (Details) - Wholesale - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Impaired loans:
With an allowance	$ 1,440	$ 726
Without an allowance	577	298
Total impaired loans	2,017	1,024
Allowance for loan losses related to impaired loans	342	274
Unpaid principal balance of impaired loans	2,345	1,209
Average impaired loans	1,923	845	$ 715
Troubled debt restructurings	733	208
Commercial and industrial
Impaired loans:
With an allowance	1,119	522
Without an allowance	414	98
Total impaired loans	1,533	620
Allowance for loan losses related to impaired loans	258	220
Unpaid principal balance of impaired loans	1,754	669
Average impaired loans	1,480	453	243
Real estate
Impaired loans:
With an allowance	125	148
Without an allowance	87	106
Total impaired loans	212	254
Allowance for loan losses related to impaired loans	18	27
Unpaid principal balance of impaired loans	295	363
Average impaired loans	217	250	297
Financial institutions
Impaired loans:
With an allowance	9	10
Without an allowance	0	0
Total impaired loans	9	10
Allowance for loan losses related to impaired loans	3	3
Unpaid principal balance of impaired loans	12	13
Average impaired loans	13	13	20
Government 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	187	46
Without an allowance	76	94
Total impaired loans	263	140
Allowance for loan losses related to impaired loans	63	24
Unpaid principal balance of impaired loans	284	164
Average impaired loans	$ 213	$ 129	$ 155