Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair value measurement
Securities available-for-sale	$ 851,577	$ 853,725
US Government Agencies Debt Securities [Member]
Fair value measurement
Securities available-for-sale	14,807	13,249
Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	242,560	261,005
Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	2	4
Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	351,549	348,176
State and Municipal Obligations
Fair value measurement
Securities available-for-sale	230,376	218,923
Collateralized Debt Obligations
Fair value measurement
Securities available-for-sale	12,283	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	835,614	837,147
Derivative Assets	526	653
Derivative Liability	(526)	(653)
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Fair value measurement
Securities available-for-sale	14,807	13,249
Fair Value, Inputs, Level 2 [Member] | Mortgage Backed Securities - Residential
Fair value measurement
Securities available-for-sale	242,560	261,005
Fair Value, Inputs, Level 2 [Member] | Mortgage Backed Securities - Commercial
Fair value measurement
Securities available-for-sale	2	4
Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Obligations
Fair value measurement
Securities available-for-sale	351,549	348,176
Fair Value, Inputs, Level 2 [Member] | State and Municipal Obligations
Fair value measurement
Securities available-for-sale	226,696	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	15,963	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	$ 12,283	$ 12,368