Loans - Wholesale Loan Portfolio - Impaired Loans (Details) - Wholesale - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Total retained loans
Impaired loans:
With an allowance	$ 1,868		$ 726
Without an allowance	362		298
Total impaired loans	2,230		1,024
Allowance for loan losses related to impaired loans	565		274
Unpaid principal balance of impaired loans	2,522		1,209
Average impaired loans	1,548	$ 642
Troubled debt restructuring	296		208
Commercial and industrial
Impaired loans:
With an allowance	1,555		522
Without an allowance	179		98
Total impaired loans	1,734		620
Allowance for loan losses related to impaired loans	491		220
Unpaid principal balance of impaired loans	1,863		669
Average impaired loans	1,123	251
Real estate
Impaired loans:
With an allowance	177		148
Without an allowance	88		106
Total impaired loans	265		254
Allowance for loan losses related to impaired loans	20		27
Unpaid principal balance of impaired loans	412		363
Average impaired loans	233	268
Financial institutions
Impaired loans:
With an allowance	11		10
Without an allowance	0		0
Total impaired loans	11		10
Allowance for loan losses related to impaired loans	3		3
Unpaid principal balance of impaired loans	12		13
Average impaired loans	11	16
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
Other
Impaired loans:
With an allowance	125		46
Without an allowance	95		94
Total impaired loans	220		140
Allowance for loan losses related to impaired loans	51		24
Unpaid principal balance of impaired loans	235		$ 164
Average impaired loans	$ 181	$ 107