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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic and diluted net loss per common share calculation:
Net income (loss)									$ (84,547)	$ (58,859)	$ 63,087
Weighted average common shares outstanding - basic (in shares)									74,185	42,224	37,061
Plus: net effect of dilutive stock options and unvested restricted stock units (in shares)									0	0	27
Weighted average common shares outstanding - dilutive (in shares)									74,185	42,224	37,088
Net income (loss) per common share - basic (USD per share)	$ (0.27)	$ (0.27)	$ (0.32)	$ (0.28)	$ (0.39)	$ (0.35)	$ (0.35)	$ (0.30)	$ (1.14)	$ (1.39)	$ 1.70
Net income (loss) per common share - diluted (USD per share)	$ (0.27)	$ (0.27)	$ (0.32)	$ (0.28)	$ (0.39)	$ (0.35)	$ (0.35)	$ (0.30)	$ (1.14)	$ (1.39)	$ 1.70