Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic:
Net Income (Loss)	$ 795,076	$ (5,537)	$ (112,385)	$ 311,338	$ (111,109)	$ (205,702)	$ 677,154	$ (5,473)
Weighted average number of common shares (in shares)	350,424			347,628			349,642	347,206
Basic net loss per common share (USD per share)	$ 2.27			$ 0.90			$ 1.94	$ (0.02)
Diluted:
Net Income (Loss)	$ 795,076	$ (5,537)	$ (112,385)	$ 311,338	$ (111,109)	$ (205,702)	$ 677,154	$ (5,473)
Weighted average number of common shares (in shares)	350,424			347,628			349,642	347,206
Dilutive share-based awards (in shares)	3,754			1,086			4,671	0
Weighted average number of common and potential common shares (in shares)	354,178			348,714			354,313	347,206
Diluted net loss per common share (USD per share)	$ 2.24			$ 0.89			$ 1.91	$ (0.02)
Antidilutive securities excluded from calculation of earnings per share (in shares)	12,600			22,300			11,700