Securities, HTM Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	Sep. 30, 2018 USD ($) Position	Dec. 31, 2017 USD ($) Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 303,687	$ 156,340
12 months or longer	167,677	87,037
Total	471,364	243,377
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(5,195)	(1,336)
12 months or longer	(9,183)	(2,671)
Total	$ (14,378)	$ (4,007)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	163	59
12 months or longer | Position	61	32
Total | Position	224	91
Federal Agency [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 9,949
12 months or longer	0
Total	9,949
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(46)
12 months or longer	0
Total	$ (46)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	2
12 months or longer | Position	0
Total | Position	2
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 55,712	$ 15,477
12 months or longer	42,778	33,703
Total	98,490	49,180
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(1,678)	(140)
12 months or longer	(2,466)	(670)
Total	$ (4,144)	$ (810)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	5	2
12 months or longer | Position	4	2
Total | Position	9	4
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 153,768	$ 118,476
12 months or longer	97,515	37,614
Total	251,283	156,090
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(2,195)	(1,064)
12 months or longer	(4,952)	(1,513)
Total	$ (7,147)	$ (2,577)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	22	17
12 months or longer | Position	16	6
Total | Position	38	23
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 84,258	$ 22,387
12 months or longer	27,384	15,720
Total	111,642	38,107
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(1,276)	(132)
12 months or longer	(1,765)	(488)
Total	$ (3,041)	$ (620)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	134	40
12 months or longer | Position	41	24
Total | Position	175	64