Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator [Abstract]
Net income	$ 46,432	$ 43,251	$ 45,172
Basic earnings per share [Abstract]
Weighted average shares (in shares)	17,431,000	17,326,000	17,158,000
Diluted earnings per share [Abstract]
Dilutive effect of equity grants (in shares)	52,000	71,000	82,000
Adjusted weighted average shares (in shares)	17,483,000	17,397,000	17,240,000
Earnings per share [Abstract]
Basic earnings per share (in dollars per share)	$ 2.66	$ 2.50	$ 2.63
Diluted earnings per share (in dollars per share)	$ 2.66	$ 2.49	$ 2.62
Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options excluded from diluted calculations (in shares)	58,063	0	65,519
Weighted average price of outstanding options (in dollars per share)	$ 35.409	$ 0	$ 35.409