Earnings Per Share - Summary (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Basic:
Net Loss	$ (107,987)	$ (183,718)	$ (240,931)	$ (311,253)	$ (291,705)	$ (552,184)
Less: net loss allocable to participating RSUs	0		0		0	0
Net loss available for basic common shares	$ (107,987)		$ (240,931)		$ (291,705)	$ (552,184)
Weighted average number of common shares outstanding (shares)	345,941		344,584		345,946	344,507
Basic net loss per common share (USD per share)	$ (0.31)		$ (0.70)		$ (0.84)	$ (1.60)
Diluted:
Net Loss	$ (107,987)	$ (183,718)	$ (240,931)	$ (311,253)	$ (291,705)	$ (552,184)
Less: net loss allocable to participating RSUs	0		0		0	0
Net loss available for diluted common shares	$ (107,987)		$ (240,931)		$ (291,705)	$ (552,184)
Weighted average number of common shares outstanding (shares)	345,941		344,584		345,946	344,507
Weighted average common equivalent shares arising from:
Dilutive stock options and non-participating RSUs (shares)	0		0		0	0
Weighted average number of common and potential common shares (shares)	345,941		344,584		345,946	344,507
Diluted net loss per common share (USD per share)	$ (0.31)		$ (0.70)		$ (0.84)	$ (1.60)