Debt - Schedule of Maximum Project Charges (Detail) - DIP Credit Agreement [Member] $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
December 31, 2019 [Member]
Debt Instrument [Line Items]
Maximum Project Charges	$ 260
March 31, 2020 [Member]
Debt Instrument [Line Items]
Maximum Project Charges	50
June 30, 2020 [Member]
Debt Instrument [Line Items]
Maximum Project Charges	50
September 30, 2020 [Member]
Debt Instrument [Line Items]
Maximum Project Charges	40
December 31, 2020 [Member]
Debt Instrument [Line Items]
Maximum Project Charges	$ 30