Debt and Other Long-Term Obligations - Ultra Resources, Inc. - Credit Agreement - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Apr. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Apr. 30, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,170,125,000		$ 2,175,000,000
Ultra Resources, Inc. | Credit Agreement
Debt Instrument [Line Items]
Credit facility, current borrowing capacity	325,000,000			$ 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	$ 1,300,000,000	$ 1,400,000,000		$ 1,400,000,000	$ 1,200,000,000
Borrowing base frequency of redetermination	semi-annual
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
Ultra Resources, Inc. | Credit Agreement | Bank Of Montreal | Revolving Credit Facility
Debt Instrument [Line Items]
Interest rate description	The Revolving Credit Facility bears interest either at a rate equal to (a) a customary London interbank offered rate plus an applicable margin that varies from 250 to 350 basis points or (b) the base rate plus an applicable margin that varies from 150 to 250 basis points. If borrowings are outstanding during a period that the Company’s consolidated net leverage ratio exceeds 4.00 to 1.00 at the end of any fiscal quarter as described below, the interest rate on such borrowings shall be at a per annum rate that is 0.25% higher than the rate that would otherwise apply until the Company has provided financial statements indicating that the consolidated net leverage ratio no longer exceeds 4.00 to 1.00.
Minimum required consolidated net leverage ratio, as percentage	400.00%
Interest rate on minimum required consolidated net leverage ratio exceeds 4.00 to 1.00	0.25%
Maximum required consolidated net leverage ratio, as percentage	400.00%
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, during the period ending on the last day of the fiscal quarter ending June 30, 2019	450.00%
Minimum required consolidated net leverage ratio, as percentage, during the period beginning on the last day of the fiscal quarter ending September 30, 2019 and ending on the last day of the fiscal quarter ending December 31, 2019	425.00%
Minimum required consolidated net leverage ratio, as percentage, beginning on the last day of the fiscal quarter ending on March 31, 2020	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 | Revolving Credit Facility
Debt Instrument [Line Items]
Net leverage ratio through 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%