Securities, HTM Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) Position	Sep. 30, 2021 USD ($) Position	Dec. 31, 2020 USD ($) Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 156,611	$ 156,611	$ 103,147
12 months or longer	99,632	99,632	0
Total	256,243	256,243	103,147
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(2,290)	(2,290)	(1,675)
12 months or longer	(3,944)	(3,944)	0
Total	$ (6,234)	$ (6,234)	$ (1,675)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	60	60	9
12 months or longer | Position	8	8	0
Total | Position	68	68	9
HTM debt securities	$ 683,103	$ 683,103	$ 616,560
Accrued interest reversed against interest income	0	0	0
Collateral-dependent HTM debt securities	0	0	0
AIR on HTM debt securities	2,600	2,600	2,700
Past Due [Member]
Unrealized Loss Position, Number of Positions [Abstract]
HTM debt securities	0	0	0
Federal Agency [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	0	0	98,342
12 months or longer	96,179	96,179	0
Total	96,179	96,179	98,342
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	0	0	(1,658)
12 months or longer	(3,821)	(3,821)	0
Total	$ (3,821)	$ (3,821)	$ (1,658)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	0	0	4
12 months or longer | Position	4	4	0
Total | Position	4	4	4
HTM debt securities	$ 100,000	$ 100,000	$ 100,000
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	56,996	56,996
12 months or longer	0	0
Total	56,996	56,996
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(568)	(568)
12 months or longer	0	0
Total	$ (568)	$ (568)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	5	5
12 months or longer | Position	0	0
Total | Position	5	5
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 31,809	$ 31,809
12 months or longer	0	0
Total	31,809	31,809
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(341)	(341)
12 months or longer	0	0
Total	$ (341)	$ (341)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	5	5
12 months or longer | Position	0	0
Total | Position	5	5
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 67,806	$ 67,806	4,805
12 months or longer	3,453	3,453	0
Total	71,259	71,259	4,805
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(1,381)	(1,381)	(17)
12 months or longer	(123)	(123)	0
Total	$ (1,504)	$ (1,504)	$ (17)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	50	50	5
12 months or longer | Position	4	4	0
Total | Position	54	54	5
HTM debt securities	$ 322,503	$ 322,503	$ 214,863
US Government Agencies Debt Securities and US Government-sponsored Enterprises Debt Securities [Member]
Unrealized Loss Position, Number of Positions [Abstract]
Held-to-maturity debt securities, percentage		53.00%	65.00%