Loans (Credit Quality Indicators - Residential, Consumer) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Current	$ 3,368,048	$ 3,353,996
Total past due	19,358	20,075
Self-originated Mortgages
Financing Receivable, Recorded Investment [Line Items]
Current	1,112,533	1,091,291
Total past due	10,347	6,413
Purchased Mortgages
Financing Receivable, Recorded Investment [Line Items]
Current	125,551	128,102
Total past due	1,459	1,442
Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	1,238,084	1,219,393
Total past due	11,806	7,855
Home Equity
Financing Receivable, Recorded Investment [Line Items]
Current	281,488	289,326
Total past due	4,235	3,141
Other
Financing Receivable, Recorded Investment [Line Items]
Current	30,663	31,484
Total past due	22	43
Total Consumer
Financing Receivable, Recorded Investment [Line Items]
Current	312,151	320,810
Total past due	$ 4,257	$ 3,184