Securities, AFS Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2021 USD ($) Position	Dec. 31, 2020 USD ($) Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 613,836	$ 213,643
12 months or longer	787	800
Total	614,623	214,443
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(17,273)	(2,170)
12 months or longer	(9)	(9)
Total	$ (17,282)	$ (2,179)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	79	19
12 months or longer | Position	4	4
Total | Position	83	23
AIR on AFS debt securities	$ 3,200	$ 3,300
Federal Agency [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	238,885	148,537
12 months or longer	0	0
Total	238,885	148,537
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(9,594)	(2,052)
12 months or longer	0	0
Total	$ (9,594)	$ (2,052)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	16	10
12 months or longer | Position	0	0
Total | Position	16	10
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 45,370
12 months or longer	0
Total	45,370
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(1,151)
12 months or longer	0
Total	$ (1,151)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	28
12 months or longer | Position	0
Total | Position	28
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 289,888	$ 47,269
12 months or longer	787	800
Total	290,675	48,069
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(5,549)	(60)
12 months or longer	(9)	(9)
Total	$ (5,558)	$ (69)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	21	3
12 months or longer | Position	4	4
Total | Position	25	7
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 32,238	$ 17,837
12 months or longer	0	0
Total	32,238	17,837
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(934)	(58)
12 months or longer	0	0
Total	$ (934)	$ (58)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	11	6
12 months or longer | Position	0	0
Total | Position	11	6
Corporate [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 7,455
12 months or longer	0
Total	7,455
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(45)
12 months or longer	0
Total	$ (45)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	3
12 months or longer | Position	0
Total | Position	3