Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Numerator
Net income (loss)	$ (99,140)	$ (144,428)	$ (27,828)	$ 83,464	$ 114,501	$ 56,076	$ (271,396)	$ 254,041
Denominator
Weighted-average shares outstanding, basic (in shares)	92,731			68,442			80,330	68,421
Effect of dilutive stock awards (in shares)	0			103			0	140
Adjusted weighted-average shares outstanding, diluted (in shares)	92,731			68,545			80,330	68,561
Earnings (loss) per share
Basic earnings (loss) per common share (in dollars per share)	$ (1.07)			$ 1.22			$ (3.38)	$ 3.71
Diluted earnings (loss) per common share (in dollars per share)	$ (1.07)			$ 1.22			$ (3.38)	$ 3.71
Anti-dilutive weighted average shares (in shares)	3,711			136			1,748	141