Net Income (Loss) Per Common Share - Schedule of Basic and Diluted Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic and diluted net loss per common share calculation:
Net income (loss)									$ (58,859)	$ 63,087	$ 114,205
Weighted average common shares outstanding - basic (in shares)									42,224	37,061	35,919
Plus: net effect of dilutive stock options and unvested restricted stock units (in shares)									0	27	88
Weighted average common shares outstanding - dilutive (in shares)									42,224	37,088	36,007
Net income (loss) per common share - basic (USD per share)	$ (0.39)	$ (0.35)	$ (0.35)	$ (0.30)	$ 2.62	$ (0.41)	$ (0.37)	$ (0.36)	$ (1.39)	$ 1.70	$ 3.18
Net income (loss) per common share - diluted (USD per share)	$ (0.39)	$ (0.35)	$ (0.35)	$ (0.30)	$ 2.62	$ (0.41)	$ (0.37)	$ (0.36)	$ (1.39)	$ 1.70	$ 3.17