Securities, AFS Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2018 USD ($) Position	Dec. 31, 2017 USD ($) Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 32,295	$ 633,766
12 months or longer	835,966	386,818
Total	868,261	1,020,584
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(137)	(5,481)
12 months or longer	(20,209)	(10,652)
Total	$ (20,346)	$ (16,133)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	20	134
12 months or longer | Position	204	79
Total | Position	224	213
Federal Agency [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 0	$ 64,653
12 months or longer	64,294	44,246
Total	64,294	108,899
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	0	(242)
12 months or longer	(693)	(721)
Total	$ (693)	$ (963)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	0	5
12 months or longer | Position	6	4
Total | Position	6	9
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 1,715	$ 23,566
12 months or longer	22,324	5,994
Total	24,039	29,560
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(3)	(200)
12 months or longer	(234)	(77)
Total	$ (237)	$ (277)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	3	39
12 months or longer | Position	35	8
Total | Position	38	47
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 18,462	$ 317,630
12 months or longer	428,440	58,316
Total	446,902	375,946
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(65)	(2,381)
12 months or longer	(10,764)	(1,187)
Total	$ (10,829)	$ (3,568)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	12	55
12 months or longer | Position	101	24
Total | Position	113	79
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 12,118	$ 227,917
12 months or longer	320,908	275,303
Total	333,026	503,220
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(69)	(2,658)
12 months or longer	(8,518)	(8,521)
Total	$ (8,587)	$ (11,179)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	5	35
12 months or longer | Position	62	42
Total | Position	67	77
Equity Securities [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months		$ 0
12 months or longer		2,959
Total		2,959
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months		0
12 months or longer		(146)
Total		$ (146)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position		0
12 months or longer | Position		1
Total | Position		1