Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	$ 918,591	$ 793,084
Unrealized Gains	(22,684)	(7,046)
Unrealized Losses	(1,331)	(15,214)
Securities available-for-sale	939,944	784,916
US Government Agencies Debt Securities [Member]
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	105,115	25,617
Unrealized Gains	(2,205)	(218)
Unrealized Losses	(44)	(471)
Securities available-for-sale	107,276	25,364
Mortgage Backed Securities - Residential
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	214,486	182,050
Unrealized Gains	(2,558)	(723)
Unrealized Losses	(308)	(4,030)
Securities available-for-sale	216,736	178,743
Mortgage Backed Securities - Commercial
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	24,193
Unrealized Gains	(231)
Unrealized Losses	0
Securities available-for-sale	24,424	0
Collateralized Mortgage Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	306,699	352,823
Unrealized Gains	(2,243)	(217)
Unrealized Losses	(904)	(9,424)
Securities available-for-sale	308,038	343,616
State and Municipal Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	257,889	232,457
Unrealized Gains	(11,842)	(2,767)
Unrealized Losses	(75)	(1,289)
Securities available-for-sale	269,656	233,935
Collateralized Debt Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	7	137
Unrealized Gains	(3,597)	(3,121)
Unrealized Losses	0	0
Securities available-for-sale	$ 3,604	$ 3,258