Loans - Aging of Recorded Investment in Past Due Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 16,825	$ 19,129
Loans Not Past Due	2,737,744	2,460,219
Total ending loans balance	2,754,569	2,479,348
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	5,022	7,608
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3,078	4,618
Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	8,725	6,903
Commercial, Industrial, and Agricultural
Financing Receivable, Past Due [Line Items]
Total Past Due	7,629	4,612
Loans Not Past Due	1,026,002	911,685
Total ending loans balance	1,033,631	916,297
Commercial, Industrial, and Agricultural | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,508	2,339
Commercial, Industrial, and Agricultural | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,041	9
Commercial, Industrial, and Agricultural | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	4,080	2,264
Commercial mortgages
Financing Receivable, Past Due [Line Items]
Total Past Due	2,098	4,096
Loans Not Past Due	786,876	693,680
Total ending loans balance	788,974	697,776
Commercial mortgages | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	230	758
Commercial mortgages | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	3,055
Commercial mortgages | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	1,868	283
Residential real estate
Financing Receivable, Past Due [Line Items]
Total Past Due	5,933	9,227
Loans Not Past Due	796,398	762,082
Total ending loans balance	802,331	771,309
Residential real estate | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,759	3,982
Residential real estate | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	759	1,257
Residential real estate | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,415	3,988
Consumer
Financing Receivable, Past Due [Line Items]
Total Past Due	1,019	1,115
Loans Not Past Due	120,579	84,920
Total ending loans balance	121,598	86,035
Consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	472	470
Consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	230	282
Consumer | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	317	363
Credit cards
Financing Receivable, Past Due [Line Items]
Total Past Due	146	79
Loans Not Past Due	7,247	7,544
Total ending loans balance	7,393	7,623
Credit cards | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	53	59
Credit cards | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	48	15
Credit cards | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	45	5
Overdrafts
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Loans Not Past Due	642	308
Total ending loans balance	642	308
Overdrafts | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Overdrafts | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Overdrafts | Greater Than 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 0	$ 0