Net Income (Loss) Per 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
Numerator for Basic and Diluted Earnings per Share - [Abstract]
Net Income (Loss)	$ 337,466		$ (42,467)		$ (909,384)		$ 9,813		$ 636,521		$ 615,122		$ 847,841		$ 635,426		$ (604,572)	$ 2,734,910	$ 3,419,040
Denominator for Basic Earnings per Share - [Abstract]
Weighted Average Shares	579,624		579,055		578,719		578,462		578,219		577,839		577,460		577,207		578,949	577,670	576,578
Denominator for Diluted Earnings per Share - [Abstract]
Adjusted Diluted Weighted Average Shares	580,885		579,055		578,719		580,283		580,849		581,271		580,247		580,222		578,949	580,777	580,441
Antidilutive Securities Excluded from Computation of Earnings Per Share [Abstract]
Anti-dilutive Securities excluded from Diluted Earnings Per Share Calculation																	9,600	6,100	600
Net Income (Loss) Per Share [Abstract]
Basic	$ 0.58	[1]	$ (0.07)	[1]	$ (1.57)	[1]	$ 0.02	[1]	$ 1.10	[1]	$ 1.06	[1]	$ 1.47	[1]	$ 1.10	[1]	$ (1.04)	$ 4.73	$ 5.93
Diluted	$ 0.58	[1]	$ (0.07)	[1]	$ (1.57)	[1]	$ 0.02	[1]	$ 1.10	[1]	$ 1.06	[1]	$ 1.46	[1]	$ 1.10	[1]	$ (1.04)	$ 4.71	$ 5.89
Stock Options and Sars [Member]
Potential Dilutive Common Shares -[Abstract]
Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangments																	0	258	1,137
Restricted Stock/Units and Performance Units/Stock [Member]
Potential Dilutive Common Shares -[Abstract]
Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangments																	0	2,849	2,726
Antidilutive Securities Excluded from Computation of Earnings Per Share [Abstract]
Anti-dilutive Securities excluded from Diluted Earnings Per Share Calculation																	5,000

[1] The sum of quarterly net income (loss) per share may not agree with total year net income (loss) per share as each quarterly computation is based on the weighted average of common shares outstanding.