Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	$ 840,352	$ 855,521
Unrealized Gains	(16,225)	(12,618)
Unrealized Losses	(5,000)	(14,414)
Securities available-for-sale	851,577	853,725
US Government Agencies Debt Securities [Member]
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	14,898	13,594
Unrealized Gains	(50)	(32)
Unrealized Losses	(141)	(377)
Securities available-for-sale	14,807	13,249
Mortgage Backed Securities - Residential
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	239,368	261,878
Unrealized Gains	(4,011)	(3,200)
Unrealized Losses	(819)	(4,073)
Securities available-for-sale	242,560	261,005
Mortgage Backed Securities - Commercial
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	2	4
Unrealized Gains	0	0
Unrealized Losses	0	0
Securities available-for-sale	2	4
Collateralized Mortgage Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	353,334	353,499
Unrealized Gains	(1,811)	(1,021)
Unrealized Losses	(3,596)	(6,344)
Securities available-for-sale	351,549	348,176
State and Municipal Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	223,797	217,365
Unrealized Gains	(7,023)	(3,954)
Unrealized Losses	(444)	(2,396)
Securities available-for-sale	230,376	218,923
Collateralized Debt Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	8,953	9,181
Unrealized Gains	(3,330)	(4,411)
Unrealized Losses	0	(1,224)
Securities available-for-sale	$ 12,283	$ 12,368