Loans - Consumer, Excluding Credit Card Loans, Loan Modifications, Nature and Extent of Modifications (Details) - Consumer, excluding credit card - loan	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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	4,886	3,604	5,705
Total residential real estate – excluding PCI | Permanent Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	7,853	8,252	8,162
Total residential real estate – excluding PCI | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Concession granted	54.00%	60.00%	76.00%
Total residential real estate – excluding PCI | Term or payment extension
Financing Receivable, Impaired [Line Items]
Concession granted	62.00%	70.00%	86.00%
Total residential real estate – excluding PCI | Principal and/or interest deferred
Financing Receivable, Impaired [Line Items]
Concession granted	29.00%	12.00%	18.00%
Total residential real estate – excluding PCI | Principal forgiveness
Financing Receivable, Impaired [Line Items]
Concession granted	7.00%	14.00%	16.00%
Total residential real estate – excluding PCI | Other
Financing Receivable, Impaired [Line Items]
Concession granted	51.00%	32.00%	14.00%
Residential mortgage | Trial Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	2,570	1,283	1,945
Residential mortgage | Permanent Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	2,907	2,628	3,338
Residential mortgage | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Concession granted	40.00%	63.00%	76.00%
Residential mortgage | Term or payment extension
Financing Receivable, Impaired [Line Items]
Concession granted	55.00%	72.00%	90.00%
Residential mortgage | Principal and/or interest deferred
Financing Receivable, Impaired [Line Items]
Concession granted	44.00%	15.00%	16.00%
Residential mortgage | Principal forgiveness
Financing Receivable, Impaired [Line Items]
Concession granted	8.00%	16.00%	26.00%
Residential mortgage | Other
Financing Receivable, Impaired [Line Items]
Concession granted	38.00%	33.00%	25.00%
Home equity | Trial Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	2,316	2,321	3,760
Home equity | Permanent Modification
Financing Receivable, Impaired [Line Items]
Number of loans modified	4,946	5,624	4,824
Home equity | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Concession granted	62.00%	59.00%	75.00%
Home equity | Term or payment extension
Financing Receivable, Impaired [Line Items]
Concession granted	66.00%	69.00%	83.00%
Home equity | Principal and/or interest deferred
Financing Receivable, Impaired [Line Items]
Concession granted	20.00%	10.00%	19.00%
Home equity | Principal forgiveness
Financing Receivable, Impaired [Line Items]
Concession granted	7.00%	13.00%	9.00%
Home equity | Other
Financing Receivable, Impaired [Line Items]
Concession granted	58.00%	31.00%	6.00%