Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator for Basic and Diluted Earnings per Share - [Abstract]
Net Income (Loss)	$ 892,768		$ 1,190,952		$ 696,731		$ 638,589		$ 2,430,468		$ 100,541		$ 23,053		$ 28,517		$ 3,419,040	$ 2,582,579	$ (1,096,686)
Denominator for Basic Earnings per Share - [Abstract]
Weighted Average Shares	577,035		577,254		576,135		575,775		575,394		574,783		574,439		573,935		576,578	574,620	553,384
Denominator for Diluted Earnings per Share - [Abstract]
Adjusted Diluted Weighted Average Shares	580,288		581,559		580,375		579,726		579,203		578,736		578,483		578,593		580,441	578,693	553,384
Net Income (Loss) Per Share [Abstract]
Basic	$ 1.55	[1]	$ 2.06	[1]	$ 1.21	[1]	$ 1.11	[1]	$ 4.22	[1]	$ 0.17	[1]	$ 0.04	[1]	$ 0.05	[1]	$ 5.93	$ 4.49	$ (1.98)
Diluted	$ 1.54	[1]	$ 2.05	[1]	$ 1.20	[1]	$ 1.10	[1]	$ 4.20	[1]	$ 0.17	[1]	$ 0.04	[1]	$ 0.05	[1]	$ 5.89	$ 4.46	$ (1.98)
Stock Options and Sars [Member]
Potential Dilutive Common Shares -[Abstract]
Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangments																	1,137	1,466	0
Antidilutive Securities Excluded from Computation of Earnings Per Share [Abstract]
Anti-dilutive Securities excluded from Diluted Earnings Per Share Calculation																	600	2,600	10,300
Restricted Stock/Units and Performance Units/Stock [Member]
Potential Dilutive Common Shares -[Abstract]
Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangments																	2,726	2,607	0
Antidilutive Securities Excluded from Computation of Earnings Per Share [Abstract]
Anti-dilutive Securities excluded from Diluted Earnings Per Share Calculation																		4,500

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