Loans (Credit Quality Indicators - Residential, Consumer) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Current	$ 4,073,921	$ 3,877,310
Total past due	16,475	15,689
Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,498,179	1,437,661
Total past due	12,293	11,429
Home Equity
Financing Receivable, Credit Quality Indicator [Line Items]
Current	284,652	288,178
Total past due	2,482	2,696
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current	19,498	20,044
Total past due	115	130
Total Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Current	304,150	308,222
Total past due	$ 2,597	$ 2,826