Accumulated Other Comprehensive Income (''AOCI'') - Amount Reclassified from AOCI (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Amount Reclassified from AOCI
Gain on sales of securities								$ 270
Interest income on taxable securities	$ 2,320			$ 2,481			$ 5,992	9,584
Income tax expense	(5,555)			(4,198)			(12,828)	(9,340)
Net income	13,718	$ 8,813	$ 11,204	11,197	$ 10,618	$ 1,861	33,735	23,676
Unrealized Gains (Losses) on Available-for-Sale Securities and I/O Strips
Amount Reclassified from AOCI
Net of tax								191
Unrealized Gains (Losses) on Available-for-Sale Securities and I/O Strips | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Gain on sales of securities								270
Income tax expense								(79)
Net income								191
Unamortized Unrealized Gain on Available-for-Sale Securities Reclassified to Held-to-Maturity
Amount Reclassified from AOCI
Net of tax	9			9			27	27
Unamortized Unrealized Gain on Available-for-Sale Securities Reclassified to Held-to-Maturity | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Interest income on taxable securities	13			13			39	39
Income tax expense	(4)			(4)			(12)	(12)
Net income	9			9			27	27
Defined Benefit Pension Plan Items
Amount Reclassified from AOCI
Net of tax	(95)			(201)			(356)	(313)
Defined Benefit Pension Plan Items | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Other noninterest expense	(135)			(285)			(505)	(445)
Income tax benefit	40			84			149	132
Net of tax	(95)			(201)			(356)	(313)
Prior transition obligation | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Other noninterest expense	1			15			3	45
Prior service cost | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Other noninterest expense	(136)			(300)			(508)	(490)
Accumulated Other Comprehensive Loss
Amount Reclassified from AOCI
Net of tax	(86)			(192)			(329)	(95)
Accumulated Other Comprehensive Loss | Amount Reclassified from AOCI
Amount Reclassified from AOCI
Net of tax	$ (86)			$ (192)			$ (329)	$ (95)