Loans and Allowance for Loan Losses (Details 5) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Aging of loans
Current		$ 78,047	$ 77,188
30 to 89 Days Past Due		220	228
Total loans 90 days or more past due and still accruing		121	135
Total Past Due		341	363
Loans held for investment	[1]	78,388	77,551
Commercial portfolio
Aging of loans
Current		42,374	43,939
30 to 89 Days Past Due		70	91
Total loans 90 days or more past due and still accruing		66	76
Total Past Due		136	167
Loans held for investment		42,510	44,106
Commercial portfolio | Commercial and industrial
Aging of loans
Current		26,202	27,085
30 to 89 Days Past Due		34	54
Total loans 90 days or more past due and still accruing		56	59
Total Past Due		90	113
Loans held for investment		26,292	27,198
Commercial portfolio | Commercial mortgage
Aging of loans
Current		14,251	14,571
30 to 89 Days Past Due		36	37
Total loans 90 days or more past due and still accruing		10	17
Total Past Due		46	54
Loans held for investment		14,297	14,625
Commercial portfolio | Construction
Aging of loans
Current		1,921	2,283
30 to 89 Days Past Due		0	0
Total loans 90 days or more past due and still accruing		0	0
Total Past Due		0	0
Loans held for investment		1,921	2,283
Consumer portfolio
Aging of loans
Current		35,673	33,249
30 to 89 Days Past Due		150	137
Total loans 90 days or more past due and still accruing		55	59
Total Past Due		205	196
Loans held for investment		35,878	33,445
Consumer portfolio | Residential mortgage
Aging of loans
Current		32,355	29,770
30 to 89 Days Past Due		125	110
Total loans 90 days or more past due and still accruing		43	42
Total Past Due		168	152
Loans held for investment		32,523	29,922
Consumer portfolio | Home equity and other consumer loans
Aging of loans
Current		3,318	3,479
30 to 89 Days Past Due		25	27
Total loans 90 days or more past due and still accruing		12	17
Total Past Due		37	44
Loans held for investment		$ 3,355	$ 3,523

[1] Includes $232 million and $180 million at June 30, 2017 and December 31, 2016, respectively, for net unamortized (discounts) and premiums and deferred (fees) and costs.