Investment Securities - Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value
Less Than 12 Months	$ 527,519	$ 38,116
12 Months or Greater	16,313	3,949
Total	543,832	42,065
Gross Unrealized Losses
Less Than 12 Months	(8,946)	(143)
12 Months or Greater	(304)	(271)
Total	(9,250)	(414)
U.S. treasury securities
Fair Value
Less Than 12 Months	42,382
12 Months or Greater	0
Total	42,382
Gross Unrealized Losses
Less Than 12 Months	(652)
12 Months or Greater	0
Total	(652)
U.S. agency
Fair Value
Less Than 12 Months	8,473
12 Months or Greater	0
Total	8,473
Gross Unrealized Losses
Less Than 12 Months	(165)
12 Months or Greater	0
Total	(165)
State, county & municipal securities
Fair Value
Less Than 12 Months	158,260	8,282
12 Months or Greater	2,476	0
Total	160,736	8,282
Gross Unrealized Losses
Less Than 12 Months	(3,446)	(65)
12 Months or Greater	(74)	0
Total	(3,520)	(65)
Corporate debt securities
Fair Value
Less Than 12 Months	18,711	999
12 Months or Greater	0	0
Total	18,711	999
Gross Unrealized Losses
Less Than 12 Months	(163)	(1)
12 Months or Greater	0	0
Total	(163)	(1)
Mortgage-backed securities
Fair Value
Less Than 12 Months	299,693	28,835
12 Months or Greater	13,837	3,949
Total	313,530	32,784
Gross Unrealized Losses
Less Than 12 Months	(4,520)	(77)
12 Months or Greater	(230)	(271)
Total	$ (4,750)	$ (348)