Reorganization and Fresh Start Accounting - Reorganization Value and Valuation of Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Feb. 05, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Reorganization, Chapter 11 [Line Items]
Enterprise Value			$ 1,300,300
Plus: Cash and cash equivalents	$ 112,225		111,968	$ 343,332
Less: Fair value of debt	(406,000)		(393,500)	0
Fair Value of Successor Equity	1,366,668	$ 1,385,724	1,018,768	(311,388)	$ 2,509,034	$ 2,556,970	$ 3,658,972
Enterprise value			1,300,300
Plus: Cash and cash equivalents	$ 112,225		111,968	$ 343,332
Plus: Non-interest bearing current liabilities			185,410
Plus: Non-interest bearing non-current liabilities			108,268
Reorganization value of Successor assets			1,705,946
Minimum
Reorganization, Chapter 11 [Line Items]
Enterprise Value			1,100,000
Enterprise value			1,100,000
Maximum
Reorganization, Chapter 11 [Line Items]
Enterprise Value			1,600,000
Enterprise value			$ 1,600,000