Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair value measurement
Securities available-for-sale	$ 855,681	$ 853,725
US Government Agencies Debt Securities [Member]
Fair value measurement
Securities available-for-sale	13,226	13,249
Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	251,554	261,005
Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	3	4
Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	355,050	348,176
State and Municipal Obligations
Fair value measurement
Securities available-for-sale	223,855	218,923
Collateralized Debt Obligations
Fair value measurement
Securities available-for-sale	11,993	12,368
Fair Value, Inputs, Level 1 [Member]
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member]
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] | Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] | Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] | Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] | State and Municipal Obligations
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] | Collateralized Debt Obligations
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 2 [Member]
Fair value measurement
Securities available-for-sale	840,008	837,147
Derivative Assets	540	653
Derivative Liability	(540)	(653)
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Fair value measurement
Securities available-for-sale	13,226	13,249
Fair Value, Inputs, Level 2 [Member] | Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	251,554	261,005
Fair Value, Inputs, Level 2 [Member] | Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	3	4
Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	355,050	348,176
Fair Value, Inputs, Level 2 [Member] | State and Municipal Obligations
Fair value measurement
Securities available-for-sale	220,175	214,713
Fair Value, Inputs, Level 2 [Member] | Collateralized Debt Obligations
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 3 [Member]
Fair value measurement
Securities available-for-sale	15,673	16,578
Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member]
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 3 [Member] | Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 3 [Member] | Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 3 [Member] | Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	0	0
Fair Value, Inputs, Level 3 [Member] | State and Municipal Obligations
Fair value measurement
Securities available-for-sale	3,680	4,210
Fair Value, Inputs, Level 3 [Member] | Collateralized Debt Obligations
Fair value measurement
Securities available-for-sale	$ 11,993	$ 12,368