Securities Available for Sale - Gross unrealized losses and the related fair value of securities available for sale (Details) $ in Thousands	Sep. 30, 2019 USD ($) Security	Dec. 31, 2018 USD ($) Security
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	$ 84,571	$ 88,296
Less than 12 months, unrealized losses	275	907
12 months or more, fair value	65,643	251,570
12 months or more, unrealized losses	792	7,290
Total, fair value	150,214	339,866
Total, unrealized losses	$ 1,067	$ 8,197
Total, number of securities | Security	293	680
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	$ 0	$ 0
Less than 12 months, unrealized losses	0	0
12 months or more, fair value	16,490	21,649
12 months or more, unrealized losses	207	818
Total, fair value	16,490	21,649
Total, unrealized losses	$ 207	$ 818
Total, number of securities | Security	3	3
State, county and municipals
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	$ 44,012	$ 16,136
Less than 12 months, unrealized losses	138	98
12 months or more, fair value	8,370	130,975
12 months or more, unrealized losses	60	3,154
Total, fair value	52,382	147,111
Total, unrealized losses	$ 198	$ 3,252
Total, number of securities | Security	139	440
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	$ 38,515	$ 20,568
Less than 12 months, unrealized losses	127	132
12 months or more, fair value	40,783	89,189
12 months or more, unrealized losses	525	2,902
Total, fair value	79,298	109,757
Total, unrealized losses	$ 652	$ 3,034
Total, number of securities | Security	150	204
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	$ 2,044	$ 51,592
Less than 12 months, unrealized losses	10	677
12 months or more, fair value	0	9,757
12 months or more, unrealized losses	0	416
Total, fair value	2,044	61,349
Total, unrealized losses	$ 10	$ 1,093
Total, number of securities | Security	1	33