Loans - Narrative and Balances By Portfolio Segment (Details)	12 Months Ended
	Dec. 31, 2016 loan_payment loan_segment
Loans and Leases Receivable Disclosure [Line Items]
Number of portfolio segments | loan_segment	3
Consumer, excluding credit card | Minimum
Loans and Leases Receivable Disclosure [Line Items]
Number of payments under modified terms to recognize interest on cash basis | loan_payment	6
Consumer, excluding credit card | 90 or more days past due
Loans and Leases Receivable Disclosure [Line Items]
Period past due, credit analysis factors, charge off criteria	90 days
Consumer, excluding credit card | 30 or more days past due
Loans and Leases Receivable Disclosure [Line Items]
Period past due, credit analysis factors, charge off criteria	30 days
Residential real estate loans, non-modified credit card loans and scored business ranking loans | Days Past Due, 180 or More
Loans and Leases Receivable Disclosure [Line Items]
Loans, charge-off criteria, period past due	180 days
Auto, student, and modified credit card loans | Days Past Due, 120 or More
Loans and Leases Receivable Disclosure [Line Items]
Loans, charge-off criteria, period past due	120 days
Residential real estate and auto loans | Days Past Due, 60 or More, or Sooner with Determination of Collateral Dependence
Loans and Leases Receivable Disclosure [Line Items]
Period past due, credit analysis factors, charge off criteria	60 days
Credit card and scored business loans | Days Until Charge-Off, Less Than 60, with Notification of Bankruptcy Filing or Other Event
Loans and Leases Receivable Disclosure [Line Items]
Period past due, credit analysis factors, charge off criteria	60 days
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Number of months the borrower has performed under modified terms	6 months
Residential mortgage | Maximum
Loans and Leases Receivable Disclosure [Line Items]
Number of months before updating exterior opinion on home valuation	6 months
Real estate | Minimum
Loans and Leases Receivable Disclosure [Line Items]
Number of months before updating collateral values on commercial real estate loans	6 months
Real estate | Maximum
Loans and Leases Receivable Disclosure [Line Items]
Number of months before updating collateral values on commercial real estate loans	12 months