Loans (Credit Quality Indicators - Residential, Consumer) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Current	$ 4,271,653	$ 3,877,310
Total past due	10,394	15,689
Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,498,645	1,437,661
Total past due	8,081	11,429
Home Equity
Financing Receivable, Credit Quality Indicator [Line Items]
Current	266,798	288,178
Total past due	1,753	2,696
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current	18,648	20,044
Total past due	108	130
Total Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Current	285,446	308,222
Total past due	$ 1,861	$ 2,826