Loans - Aging of Recorded Investment in Past Due Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 17,618	$ 20,029
Loans Not Past Due	2,513,143	2,459,319
Total ending loans balance	2,530,761	2,479,348
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4,059	7,834
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,096	4,691
Greater Than 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	8,463	7,504
Commercial, Industrial, and Agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,061	4,736
Loans Not Past Due	945,804	911,561
Total ending loans balance	950,865	916,297
Commercial, Industrial, and Agricultural | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,917	2,379
Commercial, Industrial, and Agricultural | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	310	16
Commercial, Industrial, and Agricultural | Greater Than 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,834	2,341
Commercial mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,621	4,213
Loans Not Past Due	704,105	693,563
Total ending loans balance	709,726	697,776
Commercial mortgages | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	387	858
Commercial mortgages | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,532	3,058
Commercial mortgages | Greater Than 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,702	297
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	6,038	9,877
Loans Not Past Due	769,561	761,432
Total ending loans balance	775,599	771,309
Residential real estate | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,453	4,064
Residential real estate | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,039	1,319
Residential real estate | Greater Than 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,546	4,494
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	821	1,124
Loans Not Past Due	85,959	84,911
Total ending loans balance	86,780	86,035
Consumer | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	286	474
Consumer | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	182	283
Consumer | Greater Than 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	353	367
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	77	79
Loans Not Past Due	7,264	7,544
Total ending loans balance	7,341	7,623
Credit cards | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	16	59
Credit cards | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	33	15
Credit cards | Greater Than 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	28	5
Overdrafts
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Loans Not Past Due	450	308
Total ending loans balance	450	308
Overdrafts | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Overdrafts | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Overdrafts | Greater Than 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 0	$ 0