Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings​ Per ​Share​ Basic ​Line ​Items
Anti-dilutive securities excluded from earnings per share	8,106	1,219
Earnings Per Share Reconciliation [Abstract]
Net loss	$ (251,269)	$ (411,895)
Basic weighted-average common shares outstanding	114,759	113,009
Dilutive effect of non-vested RSUs and contingent PSUs	0	0
Dilutive effect of warrants	0	0
Diluted weighted-average common shares outstanding	114,759	113,009
Basic net loss per common share	$ (2.19)	$ (3.64)
Diluted net loss per common share	(2.19)	$ (3.64)
1.50% Senior Secured Convertible Notes Due 2021 [Member]
Earnings​ Per ​Share​ Basic ​Line ​Items
Senior Convertible Notes, conversion price	$ 40.50