Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	$ 888,228	$ 920,897
Unrealized Gains	24,571	20,347
Unrealized Losses	(12,689)	(26,684)
Fair Value	900,110	914,560
U.S. Government agencies
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	1,413	1,623
Unrealized Gains	48	10
Unrealized Losses	0	0
Fair Value	1,461	1,633
Mortgage Backed Securities - Residential
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	177,774	191,995
Unrealized Gains	7,338	7,761
Unrealized Losses	(942)	(1,992)
Fair Value	184,170	197,764
Mortgage Backed Securities - Commercial
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	19	4,642
Unrealized Gains	1	1
Unrealized Losses	0	(252)
Fair Value	20	4,391
Collateralized Mortgage Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	502,297	521,148
Unrealized Gains	2,073	1,492
Unrealized Losses	(11,458)	(15,899)
Fair Value	492,912	506,741
State and Municipal Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	196,431	190,521
Unrealized Gains	9,303	6,388
Unrealized Losses	(261)	(1,922)
Fair Value	205,473	194,987
Collateralized Debt Obligations
Amortized cost and fair value of investments classified as available for sale
Amortized Cost	10,294	10,968
Unrealized Gains	5,808	4,695
Unrealized Losses	(28)	(6,619)
Fair Value	$ 16,074	$ 9,044