Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	$ 882,463	$ 880,946
Unrealized Gains	(27,566)	(24,296)
Unrealized Losses	(3,688)	(8,189)
Fair Value	906,341us-gaap_AvailableForSaleSecurities	897,053us-gaap_AvailableForSaleSecurities
U.S. Government agencies
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	1,300	1,411
Unrealized Gains	(65)	(56)
Unrealized Losses	0	0
Fair Value	1,365	1,467
Mortgage Backed Securities - Residential
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	174,682	180,673
Unrealized Gains	(7,817)	(7,593)
Unrealized Losses	(214)	(330)
Fair Value	182,285	187,936
Mortgage Backed Securities - Commercial
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	16	17
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	16	17
Collateralized Mortgage Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	496,720	489,765
Unrealized Gains	(4,686)	(2,513)
Unrealized Losses	(3,345)	(7,623)
Fair Value	498,061	484,655
State and Municipal Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	199,789	198,875
Unrealized Gains	(9,645)	(9,019)
Unrealized Losses	(128)	(219)
Fair Value	209,306	207,675
Collateralized Debt Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	9,956	10,205
Unrealized Gains	(5,353)	(5,115)
Unrealized Losses	(1)	(17)
Fair Value	$ 15,308	$ 15,303

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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