Securities, AFS Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	Jun. 30, 2019 USD ($) Position	Dec. 31, 2018 USD ($) Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 4,342	$ 32,295
12 months or longer	314,696	835,966
Total	319,038	868,261
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(10)	(137)
12 months or longer	(2,145)	(20,209)
Total	$ (2,155)	$ (20,346)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	2	20
12 months or longer | Position	84	204
Total | Position	86	224
Federal Agency [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 0	$ 0
12 months or longer	9,822	64,294
Total	9,822	64,294
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	0	0
12 months or longer	(178)	(693)
Total	$ (178)	$ (693)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	0	0
12 months or longer | Position	1	6
Total | Position	1	6
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months		$ 1,715
12 months or longer		22,324
Total		24,039
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months		(3)
12 months or longer		(234)
Total		$ (237)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position		3
12 months or longer | Position		35
Total | Position		38
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 0	$ 18,462
12 months or longer	137,139	428,440
Total	137,139	446,902
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	0	(65)
12 months or longer	(677)	(10,764)
Total	$ (677)	$ (10,829)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	0	12
12 months or longer | Position	44	101
Total | Position	44	113
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 4,342	$ 12,118
12 months or longer	167,735	320,908
Total	172,077	333,026
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(10)	(69)
12 months or longer	(1,290)	(8,518)
Total	$ (1,300)	$ (8,587)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	2	5
12 months or longer | Position	39	62
Total | Position	41	67