Stockholders' Equity - Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Equity [Abstract]
Net income	$ 7,177	$ 13,195	$ 18,307	$ 23,048
Weighted average number of common shares outstanding (in shares)	30,547	30,219	30,530	30,219
Dilutive effect of restricted stock grants after application of the treasury stock method (in shares)	277	294	201	324
Dilutive shares outstanding (in shares)	30,824	30,513	30,731	30,543
Basic earnings per share (in dollars per share)	$ 0.23	$ 0.44	$ 0.60	$ 0.76
Diluted earnings per share (in dollars per share)	$ 0.23	$ 0.43	$ 0.60	$ 0.75