Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	$ 918,913	$ 920,897
Unrealized Gains	21,755	20,347
Unrealized Losses	(19,503)	(26,684)
Fair Value	921,165	914,560
U.S. Government agencies
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	1,531	1,623
Unrealized Gains	28	10
Unrealized Losses	0	0
Fair Value	1,559	1,633
Mortgage Backed Securities - Residential
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	188,755	191,995
Unrealized Gains	7,580	7,761
Unrealized Losses	(1,613)	(1,992)
Fair Value	194,722	197,764
Mortgage Backed Securities - Commercial
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	26	4,642
Unrealized Gains	1	1
Unrealized Losses	0	(252)
Fair Value	27	4,391
Collateralized Mortgage Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	528,654	521,148
Unrealized Gains	1,648	1,492
Unrealized Losses	(13,364)	(15,899)
Fair Value	516,938	506,741
State and Municipal Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	189,302	190,521
Unrealized Gains	7,189	6,388
Unrealized Losses	(1,080)	(1,922)
Fair Value	195,411	194,987
Collateralized Debt Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	10,645	10,968
Unrealized Gains	5,309	4,695
Unrealized Losses	(3,446)	(6,619)
Fair Value	$ 12,508	$ 9,044