Securities - Gross Unrealized Losses and Fair Value of Company's Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	$ 111,815	$ 224,138
Unrealized losses less than 12 months	(745)	(2,788)
Fair value more than 12 months	1,307	67,402
Unrealized losses more than 12 months	(42)	(574)
Total fair value	113,122	291,540
Total unrealized losses	(787)	(3,362)
U.S. Treasury and federal agencies
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	5,239	1,413
Unrealized losses less than 12 months	(11)	(2)
Fair value more than 12 months	0	0
Unrealized losses more than 12 months	0	0
Total fair value	5,239	1,413
Total unrealized losses	(11)	(2)
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	105,976	129,942
Unrealized losses less than 12 months	(733)	(2,374)
Fair value more than 12 months	1,307	6,279
Unrealized losses more than 12 months	(42)	(131)
Total fair value	107,283	136,221
Total unrealized losses	(775)	(2,505)
Federal agency collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	600	68,043
Unrealized losses less than 12 months	(1)	(308)
Fair value more than 12 months	0	23,301
Unrealized losses more than 12 months	0	(260)
Total fair value	600	91,344
Total unrealized losses	$ (1)	(568)
Federal agency mortgage-backed pools
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months		24,740
Unrealized losses less than 12 months		(104)
Fair value more than 12 months		37,822
Unrealized losses more than 12 months		(183)
Total fair value		62,562
Total unrealized losses		$ (287)