Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Basic Net Income (Loss) Per Share
Basic net income (loss) per share	$ 53,535	$ (720,642)
Weighted average common shares outstanding	219,801,000	216,721,000
Basic net income (loss) per share	$ 0.24	$ (3.33)
Diluted Net Income (Loss) Per Share
Diluted net income (loss)	$ 53,535	$ (720,642)
Weighted average common shares outstanding	219,801,000	216,721,000
Dilutive stock options and awards	2,066,000
Weighted average shares used to compute diluted net income (loss) per share	221,867,000	216,721,000
Diluted net income (loss) per share	$ 0.24	$ (3.33)
Anti-dilutive securities
Potential common shares excluded from diluted net income (loss) per share computation	8,871,744	15,913,287
Stock Options
Anti-dilutive securities
Potential common shares excluded from diluted net income (loss) per share computation	8,871,744	15,544,348
Convertible Senior Notes 1.25 Percent Due 2020
Anti-dilutive securities
Potential common shares excluded from diluted net income (loss) per share computation		368,939