Earnings Per Share - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Basic EPS calculation
Net income (loss)	$ (18,864)	$ (64,901)	$ (115,300)	$ 52,649	$ 31,972	$ (34,098)	$ (199,065)	$ 50,523
Weighted-average shares of common stock outstanding (in shares)	79,879,000			80,982,000			79,776,000	81,703,000
Basic (loss) earnings per share (in dollars per share)	$ (0.24)			$ 0.65			$ (2.50)	$ 0.62
Diluted EPS calculation
Net income (loss)	$ (18,864)	$ (64,901)	$ (115,300)	$ 52,649	$ 31,972	$ (34,098)	$ (199,065)	$ 50,523
Weighted-average shares of common stock outstanding (in shares)	79,879,000			80,982,000			79,776,000	81,703,000
Dilutive effect of potentially dilutive securities (in shares)	0			69,000			0	145,000
Weighted-average common shares outstanding - diluted (in shares)	79,879,000			81,051,000			79,776,000	81,848,000
Diluted (loss) earnings per share (in dollars per share)	$ (0.24)			$ 0.65			$ (2.50)	$ 0.62
Potentially dilutive securities (in shares)	0						0