Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - USD ($)				3 Months Ended			9 Months Ended
	Nov. 01, 2019	Oct. 21, 2019	Apr. 18, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2019	Dec. 31, 2018	May 08, 2018
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Loss on asset disposals					$ 1,000,000		$ 103,000,000	$ 2,000,000
Cost of operations				$ 2,180,000,000	2,016,000,000		6,167,000,000	3,990,000,000
Selling, general and administrative expenses				40,000,000	64,000,000		189,000,000	188,000,000
Operating lease right-of-use assets				361,000,000			361,000,000
Current portion of long-term lease obligations				161,000,000			161,000,000			$ 8,000,000
Long-term lease obligations				301,000,000			301,000,000			$ 66,000,000
Senior secured long-term borrowing											$ 2,260,000,000
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Interest rate derivatives											$ 1,940,000,000
ASU 2016-02 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Operating lease right-of-use assets									$ 424,000,000
Current portion of long-term lease obligations									101,000,000
Long-term lease obligations									$ 342,000,000
Other Operating Expense [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Loss on asset disposals					$ (1,000,000)			$ (2,000,000)
Pre-Combination Bid and Proposal Costs [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Selling, general and administrative expenses						$ 10,000,000
Senior Notes [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Debt instrument interest rate			10.625%
Senior Notes [Member] | Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Scheduled interest payment due	$ 69,000,000
Debt instrument interest rate	10.625%
Debt Instrument maturity year	2024
Minimum percentage of aggregate principle amount called up for immediate repayment upon default of scheduled interest payment	25.00%
Minimum percentage of outstanding aggregate principal amount to be refinanced		95.00%
Superpriority Credit Agreement [Member] | Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Available capacity under credit facility		$ 1,700,000,000
Line of credit facility, expiration date		Oct. 21, 2021
Superpriority Credit Agreement [Member] | Subsequent Event [Member] | Tranche A [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		$ 650,000,000
Superpriority Credit Agreement [Member] | Subsequent Event [Member] | Tranche B [Member] | Available to Borrowers between November 30, 2019 and December 31, 2019 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		350,000,000
Superpriority Credit Agreement [Member] | Subsequent Event [Member] | Tranche C [Member] | Available to Borrowers between December 30, 2019 and March 31, 2020 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		150,000,000
Superpriority Credit Agreement [Member] | Subsequent Event [Member] | Tranche D [Member] | Available to Borrowers between January 31, 2020 and March 31, 2020 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		550,000,000
Superpriority Credit Agreement [Member] | Subsequent Event [Member] | New LC Facility [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Available capacity under credit facility		400,000,000
Superpriority Credit Agreement [Member] | Subsequent Event [Member] | New LC Facility [Member] | Tranche A [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		100,000,000
Superpriority Credit Agreement [Member] | Subsequent Event [Member] | New LC Facility [Member] | Tranche B [Member] | Available to Borrowers between November 30, 2019 and December 31, 2019 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		100,000,000
Superpriority Credit Agreement [Member] | Subsequent Event [Member] | New LC Facility [Member] | Tranche D [Member] | Available to Borrowers between January 31, 2020 and March 31, 2020 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		200,000,000
Superpriority Credit Agreement [Member] | New Term Facility [Member] | Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Available capacity under credit facility		1,300,000,000
Superpriority Credit Agreement [Member] | New Term Facility [Member] | Subsequent Event [Member] | Tranche A [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		550,000,000
Superpriority Credit Agreement [Member] | New Term Facility [Member] | Subsequent Event [Member] | Tranche B [Member] | Available to Borrowers between November 30, 2019 and December 31, 2019 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		250,000,000
Superpriority Credit Agreement [Member] | New Term Facility [Member] | Subsequent Event [Member] | Tranche D [Member] | Available to Borrowers between January 31, 2020 and March 31, 2020 [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Line of credit facility available for capital		$ 350,000,000
Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
New contracts backlog				$ 20,000,000,000			$ 20,000,000,000