Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	$ 781,073	$ 793,084
Unrealized Gains	(11,614)	(7,046)
Unrealized Losses	(6,476)	(15,214)
Securities available-for-sale	786,211	784,916
US Government Agencies Debt Securities [Member]
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	28,916	25,617
Unrealized Gains	(725)	(218)
Unrealized Losses	(191)	(471)
Securities available-for-sale	29,450	25,364
Mortgage Backed Securities - Residential
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	182,280	182,050
Unrealized Gains	(1,127)	(723)
Unrealized Losses	(1,554)	(4,030)
Securities available-for-sale	181,853	178,743
Mortgage Backed Securities - Commercial
Amortized cost and fair value of investments classified as available for sale
Amortized Cost		0
Unrealized Gains		0
Unrealized Losses		0
Securities available-for-sale		0
Collateralized Mortgage Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	339,477	352,823
Unrealized Gains	(858)	(217)
Unrealized Losses	(4,468)	(9,424)
Securities available-for-sale	335,867	343,616
State and Municipal Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	230,304	232,457
Unrealized Gains	(5,706)	(2,767)
Unrealized Losses	(263)	(1,289)
Securities available-for-sale	235,747	233,935
Collateralized Debt Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	96	137
Unrealized Gains	(3,198)	(3,121)
Unrealized Losses	0	0
Securities available-for-sale	$ 3,294	$ 3,258