Loans - Consumer, Excluding Credit Card Loans, Loan Modifications, Nature and Extent of Modifications (Details) - Consumer, excluding credit card - loan	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Percentage, sum of items by type, may exceed	100.00%
Total residential real estate – excluding PCI | Trial Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	5,705	6,644	4,673
Total residential real estate – excluding PCI | Permanent Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	8,162	7,441	9,632
Total residential real estate – excluding PCI | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Concession granted	76.00%	68.00%	58.00%
Total residential real estate – excluding PCI | Term or payment extension
Financing Receivable, Impaired [Line Items]
Concession granted	86.00%	86.00%	63.00%
Total residential real estate – excluding PCI | Principal and/or interest deferred
Financing Receivable, Impaired [Line Items]
Concession granted	18.00%	24.00%	18.00%
Total residential real estate – excluding PCI | Principal forgiveness
Financing Receivable, Impaired [Line Items]
Concession granted	16.00%	16.00%	41.00%
Total residential real estate – excluding PCI | Other
Financing Receivable, Impaired [Line Items]
Concession granted	14.00%	5.00%	6.00%
Home equity | Trial Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	3,760	3,933	1,565
Home equity | Permanent Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	4,824	4,296	3,984
Home equity | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Concession granted	75.00%	66.00%	75.00%
Home equity | Term or payment extension
Financing Receivable, Impaired [Line Items]
Concession granted	83.00%	89.00%	78.00%
Home equity | Principal and/or interest deferred
Financing Receivable, Impaired [Line Items]
Concession granted	19.00%	23.00%	21.00%
Home equity | Principal forgiveness
Financing Receivable, Impaired [Line Items]
Concession granted	9.00%	7.00%	26.00%
Home equity | Other
Financing Receivable, Impaired [Line Items]
Concession granted	6.00%	0.00%	0.00%
Residential mortgage | Trial Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	1,945	2,711	3,108
Residential mortgage | Permanent Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	3,338	3,145	5,648
Residential mortgage | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Concession granted	76.00%	71.00%	45.00%
Residential mortgage | Term or payment extension
Financing Receivable, Impaired [Line Items]
Concession granted	90.00%	81.00%	52.00%
Residential mortgage | Principal and/or interest deferred
Financing Receivable, Impaired [Line Items]
Concession granted	16.00%	27.00%	15.00%
Residential mortgage | Principal forgiveness
Financing Receivable, Impaired [Line Items]
Concession granted	26.00%	28.00%	52.00%
Residential mortgage | Other
Financing Receivable, Impaired [Line Items]
Concession granted	25.00%	11.00%	10.00%