Basis of Presentation (Reconciliation of Net Income (Loss) and Weighted Average Shares Table) (Details) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator
Net income (loss) - basic		$ (697,474)	$ 74,016	$ 146,692	$ (25,674)	$ (623,458)	$ 121,018
Interest on convertible senior notes including amortization of discount, net of tax		0		548		0	548
Net income (loss) - diluted		$ (697,474)		$ 147,240		$ (623,458)	$ 121,566
Denominator
Weighted average common shares outstanding - basic		495,245		452,612		494,752	452,169
Restricted stock and performance-based equity awards		0		2,835		0	3,301
Convertible senior notes	[1]	0		11,980		0	5,990
Weighted average common shares outstanding - diluted		495,245		467,427		494,752	461,460
Debt Instrument, Convertible, Number of Equity Instruments		90,900

[1] hares shown under “convertible senior notes” represent the impact over the periods of the approximately 90.9 million shares of the Company’s common stock issuable upon full conversion of our convertible senior notes which were issued on June 19, 2019.