Allowance for Loan Losses - Recorded Investment in Consumer Loan Classes by Performing and Nonperforming Status (Details) - Consumer - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 1,274,203	$ 1,257,855
% of Total	100.00%	100.00%
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 1,263,335	$ 1,246,904
% of Total	99.10%	99.10%
Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 10,868	$ 10,951
% of Total	0.90%	0.90%
Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 726,679	$ 698,774
% of Total	100.00%	100.00%
Residential mortgage | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 719,551	$ 691,609
% of Total	99.00%	99.00%
Residential mortgage | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 7,128	$ 7,165
% of Total	1.00%	1.00%
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 471,562	$ 487,326
% of Total	100.00%	100.00%
Home equity | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 467,864	$ 483,611
% of Total	99.20%	99.20%
Home equity | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 3,698	$ 3,715
% of Total	0.80%	0.80%
Installment and other consumer
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 67,546	$ 67,204
% of Total	100.00%	100.00%
Installment and other consumer | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 67,504	$ 67,133
% of Total	99.90%	99.90%
Installment and other consumer | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 42	$ 71
% of Total	0.10%	0.10%
Consumer construction
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 8,416	$ 4,551
% of Total	100.00%	100.00%
Consumer construction | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 8,416	$ 4,551
% of Total	100.00%	100.00%
Consumer construction | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 0	$ 0
% of Total	0.00%	0.00%