Loans (Credit Quality Indicators - Residential, Consumer) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Current	$ 3,542,684	$ 3,353,996
Total past due	13,519	20,075
Self-originated Mortgages
Financing Receivable, Recorded Investment [Line Items]
Current	1,224,575	1,091,291
Total past due	8,172	6,413
Purchased Mortgages
Financing Receivable, Recorded Investment [Line Items]
Current	115,367	128,102
Total past due	1,226	1,442
Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	1,339,942	1,219,393
Total past due	9,398	7,855
Home Equity
Financing Receivable, Recorded Investment [Line Items]
Current	279,392	289,326
Total past due	2,939	3,141
Other
Financing Receivable, Recorded Investment [Line Items]
Current	27,191	31,484
Total past due	109	43
Total Consumer
Financing Receivable, Recorded Investment [Line Items]
Current	306,583	320,810
Total past due	$ 3,048	$ 3,184