Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator [Abstract]
Net income	$ 11,541	$ 11,566	$ 22,818	$ 23,168
Basic earnings per share [Abstract]
Weighted average shares (in shares)	17,626,000	17,530,000	17,621,000	17,521,000
Diluted earnings per share [Abstract]
Effect of dilutive stock options and restricted stock grants (in shares)	19,000	12,000	20,000	17,000
Adjusted weighted average shares (in shares)	17,645,000	17,542,000	17,641,000	17,538,000
Earnings per share [Abstract]
Basic earnings per share (in dollars per share)	$ 0.65	$ 0.66	$ 1.29	$ 1.32
Diluted earnings per share (in dollars per share)	$ 0.65	$ 0.66	$ 1.29	$ 1.32
Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options excluded from diluted calculations (in shares)	0	0	0	67,953
Weighted average price for anti dilutive securities (in dollars per share)		$ 35.31		$ 35.31