Debt - Schedule of Minimum Adjusted EBITDA (Detail) - USD ($) $ in Millions		12 Months Ended
	Oct. 21, 2019	Dec. 31, 2019
December 31, 2019 [Member] | Superpriority Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA	$ 430
March 31, 2020 [Member] | Superpriority Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA	470
June 30, 2020 [Member] | Superpriority Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA	530
June 30, 2020 [Member] | DIP Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA		$ 230
September 30, 2020 [Member] | Superpriority Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA	880
September 30, 2020 [Member] | DIP Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA		410
December 31, 2020 [Member] | Superpriority Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA	960
December 31, 2020 [Member] | DIP Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA		$ 640
March 31, 2021 [Member] | Superpriority Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA	1,090
June 30, 2021 [Member] | Superpriority Credit Agreement [Member]
Debt Instrument [Line Items]
Minimum Adjusted EBITDA	$ 1,210