Stockholders' Equity - Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Equity [Abstract]
Net income	$ 13,195	$ 131	$ 23,048	$ 760
Weighted average number of common shares outstanding (in shares)	30,219	29,874	30,219	29,873
Dilutive effect of restricted stock grants after application of the treasury stock method (in shares)	294	581	324	452
Dilutive shares outstanding (in shares)	30,513	30,455	30,543	30,325
Basic earnings per share (in dollars per share)	$ 0.44	$ 0.00	$ 0.76	$ 0.03
Diluted earnings per share (in dollars per share)	$ 0.43	$ 0.00	$ 0.75	$ 0.03