Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair value measurement
Securities available-for-sale	$ 912,495	$ 914,560
U.S. Government agencies
Fair value measurement
Securities available-for-sale	1,551	1,633
Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	185,719	197,764
Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	23	4,391
Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	508,750	506,741
State and Municipal Obligations
Fair value measurement
Securities available-for-sale	201,831	194,987
Collateralized Debt Obligations
Fair value measurement
Securities available-for-sale	14,621	9,044
Level 1
Fair value measurement
Securities available-for-sale	0	0
Level 1 | U.S. Government agencies
Fair value measurement
Securities available-for-sale	0	0
Level 1 | Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	0	0
Level 1 | Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	0	0
Level 1 | Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	0	0
Level 1 | State and Municipal Obligations
Fair value measurement
Securities available-for-sale	0	0
Level 1 | Collateralized Debt Obligations
Fair value measurement
Securities available-for-sale	0	0
Level 2
Fair value measurement
Securities available-for-sale	893,839	900,991
Derivative Assets	1,206	1,195
Derivative Liability	(1,206)	(1,195)
Level 2 | U.S. Government agencies
Fair value measurement
Securities available-for-sale	1,551	1,633
Level 2 | Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	185,719	197,764
Level 2 | Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	23	4,391
Level 2 | Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	508,750	506,741
Level 2 | State and Municipal Obligations
Fair value measurement
Securities available-for-sale	197,796	190,462
Level 2 | Collateralized Debt Obligations
Fair value measurement
Securities available-for-sale	0	0
Level 3
Fair value measurement
Securities available-for-sale	18,656	13,569
Level 3 | U.S. Government agencies
Fair value measurement
Securities available-for-sale	0	0
Level 3 | Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	0	0
Level 3 | Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	0	0
Level 3 | Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	0	0
Level 3 | State and Municipal Obligations
Fair value measurement
Securities available-for-sale	4,035	4,525
Level 3 | Collateralized Debt Obligations
Fair value measurement
Securities available-for-sale	$ 14,621	$ 9,044