Income (Loss) Per Common Share - Basic and Diluted (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
Income (Loss) Per Common Share
Net income (loss)	$ (8,953)	$ (23,740)	$ (262,414)	$ (42,918)
Net income (loss) per common share:
Basic (in dollars per share)	$ (0.19)	$ (0.51)	$ (5.55)	$ (1.00)
Diluted (in dollars per share)	$ (0.19)	$ (0.51)	$ (5.55)	$ (1.00)
Weighted average shares reconciliation
Basic weighted average shares outstanding	46,982	46,941	47,283	43,100
Diluted weighted average shares outstanding	46,982	46,941	47,283	43,100