Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 17, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights									5,900,000
Exercise Price of Warrants									$ 0.01
Warrants Percent of Outstanding Stock									5.00%
Incremental Common Shares Attributable to Dilutive Effect of Warrants	0						0
Anti-dilutive securities excluded from earnings per share	158,000			0			450,000	707,000
Calculation of basic and diluted earnings per share
Net income (loss)	$ (98,292)	$ (89,252)	$ (411,895)	$ 42,234	$ 50,388	$ (177,568)	$ (599,439)	$ (84,946)
Basic weighted-average common shares outstanding	114,371,000			112,804,000			113,462,000	112,441,000
Dilutive effect of non-vested RSUs and contingent PSUs	0			530,000			0	0
Diluted weighted-average common shares outstanding	114,371,000			113,334,000			113,462,000	112,441,000
Basic net income (loss) per common share	$ (0.86)			$ 0.37			$ (5.28)	$ (0.76)
Diluted net income (loss) per common share	$ (0.86)			0.37			$ (5.28)	(0.76)
1.50% Senior Unsecured Convertible Notes Due 2021 [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Senior Convertible Notes, conversion price				$ 40.50				$ 40.50