Stockholders' Equity - Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity [Abstract]
Net income	$ 12,583	$ 4,763	$ 35,631	$ 5,523
Weighted average number of common shares outstanding (in shares)	30,219	29,875	30,219	29,874
Dilutive effect of restricted stock grants after application of the treasury stock method (in shares)	419	612	356	505
Dilutive shares outstanding (in shares)	30,638	30,487	30,575	30,379
Basic earnings per share (in dollars per share)	$ 0.42	$ 0.16	$ 1.18	$ 0.18
Diluted earnings per share (in dollars per share)	$ 0.41	$ 0.16	$ 1.17	$ 0.18