Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator [Abstract]
Net income	$ 15,814	$ 11,277
Basic earnings per share [Abstract]
Weighted average shares (in shares)	17,671,000	17,615,000
Diluted earnings per share [Abstract]
Effect of dilutive stock options and restricted stock grants (in shares)	16,000	23,000
Adjusted weighted average shares (in shares)	17,687,000	17,638,000
Earnings per share [Abstract]
Basic earnings per share (in dollars per share)	$ 0.89	$ 0.64
Diluted earnings per share (in dollars per share)	$ 0.89	$ 0.64
Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options excluded from diluted calculations (in shares)	0	0