Stockholders' Equity - Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Equity [Abstract]
Net income	$ 11,130	$ 9,853
Weighted average number of common shares outstanding (in shares)	30,513	30,219
Dilutive effect of restricted stock grants after application of the treasury stock method (in shares)	181	355
Dilutive shares outstanding (in shares)	30,694	30,574
Basic earnings per share (in dollars per share)	$ 0.36	$ 0.33
Diluted earnings per share (in dollars per share)	$ 0.36	$ 0.32