Securities, AFS Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2019 USD ($) Position	Dec. 31, 2018 USD ($) Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 198,501	$ 32,295
12 months or longer	97,243	835,966
Total	295,744	868,261
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(718)	(137)
12 months or longer	(815)	(20,209)
Total	$ (1,533)	$ (20,346)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	48	20
12 months or longer | Position	34	204
Total | Position	82	224
Federal Agency [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 14,891	$ 0
12 months or longer	9,866	64,294
Total	24,757	64,294
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(109)	0
12 months or longer	(134)	(693)
Total	$ (243)	$ (693)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	2	0
12 months or longer | Position	1	6
Total | Position	3	6
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 2,503	$ 1,715
12 months or longer	0	22,324
Total	2,503	24,039
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(20)	(3)
12 months or longer	0	(234)
Total	$ (20)	$ (237)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	1	3
12 months or longer | Position	0	35
Total | Position	1	38
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 67,986	$ 18,462
12 months or longer	37,745	428,440
Total	105,731	446,902
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(273)	(65)
12 months or longer	(122)	(10,764)
Total	$ (395)	$ (10,829)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	21	12
12 months or longer | Position	16	101
Total | Position	37	113
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 113,121	$ 12,118
12 months or longer	49,632	320,908
Total	162,753	333,026
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(316)	(69)
12 months or longer	(559)	(8,518)
Total	$ (875)	$ (8,587)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	24	5
12 months or longer | Position	17	62
Total | Position	41	67