Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	$ 889,786	$ 880,946
Unrealized Gains	(20,667)	(24,296)
Unrealized Losses	(8,903)	(8,189)
Fair Value	901,550	897,053
US Government Agencies Debt Securities [Member]
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	1,298	1,411
Unrealized Gains	(61)	(56)
Unrealized Losses	0	0
Fair Value	1,359	1,467
Mortgage Backed Securities - Residential
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	183,601	180,673
Unrealized Gains	(6,060)	(7,593)
Unrealized Losses	(914)	(330)
Fair Value	188,747	187,936
Mortgage Backed Securities - Commercial
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	13	17
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	13	17
Collateralized Mortgage Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	489,361	489,765
Unrealized Gains	(2,548)	(2,513)
Unrealized Losses	(7,114)	(7,623)
Fair Value	484,795	484,655
State and Municipal Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	205,649	198,875
Unrealized Gains	(6,994)	(9,019)
Unrealized Losses	(873)	(219)
Fair Value	211,770	207,675
Collateralized Debt Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	9,864	10,205
Unrealized Gains	(5,004)	(5,115)
Unrealized Losses	(2)	(17)
Fair Value	$ 14,866	$ 15,303