Debt and Other Long-Term Obligations - Ultra Resources, Inc. - Credit Agreement - Additional Information (Details) - USD ($)		3 Months Ended
	Apr. 20, 2018	Mar. 31, 2018	Apr. 25, 2018	Apr. 19, 2018	Dec. 31, 2017	Sep. 30, 2017	Apr. 30, 2017
Debt Instrument [Line Items]
Long-term debt, gross		$ 2,175,000,000			$ 2,175,000,000
Second Amendment | Subsequent Event
Debt Instrument [Line Items]
Credit facility, current borrowing capacity			$ 425,000,000
Second Amendment | Bank Of Montreal | Subsequent Event
Debt Instrument [Line Items]
Borrowing Base				$ 1,400,000,000
Ultra Resources, Inc. | Credit Agreement
Debt Instrument [Line Items]
Credit facility, current borrowing capacity		425,000,000				$ 425,000,000	$ 400,000,000
Long-term debt, gross		0
Ultra Resources, Inc. | Credit Agreement | Bank Of Montreal
Debt Instrument [Line Items]
Borrowing Base		1,400,000,000				$ 1,400,000,000	$ 1,200,000,000
Ultra Resources, Inc. | Credit Agreement | Bank Of Montreal | Letters of Credit
Debt Instrument [Line Items]
Amount of commitments available for the issuance of letters of credit		50,000,000
Amount of commitments utilized		$ 34,500,000
Ultra Resources, Inc. | Credit Agreement | Bank Of Montreal | Revolving Credit Facility
Debt Instrument [Line Items]
Minimum required interest coverage ratio, as percentage		250.00%
Minimum required current ratio, as percentage		100.00%
Minimum required consolidated net leverage ratio, as percentage		400.00%
Minimum required asset coverage ratio, as percentage on achievement of investment grade		150.00%
Line of credit facility, covenant compliance		Ultra Resources was in compliance with all of its debt covenants under the Revolving Credit Facility.
Ultra Resources, Inc. | Credit Agreement | Bank Of Montreal | Revolving Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Variable rate		2.50%
Ultra Resources, Inc. | Credit Agreement | Bank Of Montreal | Revolving Credit Facility | LIBOR | Maximum
Debt Instrument [Line Items]
Variable rate		3.50%
Ultra Resources, Inc. | Credit Agreement | Bank Of Montreal | Revolving Credit Facility | Base Rate | Minimum
Debt Instrument [Line Items]
Variable rate		1.50%
Ultra Resources, Inc. | Credit Agreement | Bank Of Montreal | Revolving Credit Facility | Base Rate | Maximum
Debt Instrument [Line Items]
Variable rate		2.50%
Ultra Resources, Inc. | Second Amendment | Bank Of Montreal | Subsequent Event
Debt Instrument [Line Items]
Borrowing Base				$ 1,400,000,000
Ultra Resources, Inc. | Second Amendment | Bank Of Montreal | Subsequent Event | Revolving Credit Facility
Debt Instrument [Line Items]
Minimum required consolidated net leverage ratio, as percentage beginning on last day of June 30, 2018 and ending on last day of June 30, 2019	450.00%
Maximum required consolidated net leverage ratio, as percentage beginning on last day of September 30, 2019 and ending on last day of December 31, 2019	425.00%
Maximum required consolidated net leverage ratio, as percentage beginning on last day of March 31, 2020	400.00%
Net leverage ratio beginning on June 30, 2018 and ending on September 29, 2019, minimum required hedging percentage	65.00%
Net leverage ratio beginning on September 30, 2019 and ending on March 30, 2020, minimum required hedging percentage	50.00%
Interest rate on minimum required consolidated net leverage ratio exceeds 4.00 to 1.00	0.25%