Summary of Significant Accounting Policies - Additional Information 3 (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended							12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion ratio of oil to natural gas in units of production									One barrel of oil for six thousand cubic feet of natural gas
Impairment of unproved oil and natural gas properties						$ 76,391		$ 7,753		$ 84,144	$ 68,900
Impairment of oil and gas properties		$ 43,990			$ 2,561	113	$ 1,742	22,718	$ 43,990	27,134	$ 801,347
Proceeds from sale of oil and gas properties									1,500	2,100
Loss on sale of oil and gas properties			$ (1,036)	$ (24)	$ (212)	$ (13,196)	$ (1,647)	740	$ (1,060)	(14,315)
Minimum
Operations And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives									3 years
Maximum
Operations And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives									31 years 6 months
Other Properties
Operations And Summary Of Significant Accounting Policies [Line Items]
Impaired oil and gas properties fair value										21,100
South Texas Asset Held for Sale
Operations And Summary Of Significant Accounting Policies [Line Items]
Impairment of oil and gas properties		43,800
Assets held for sale, fair value		$ 198,600							$ 198,600
South Texas Sold Properties
Operations And Summary Of Significant Accounting Policies [Line Items]
Impairment of oil and gas properties								20,800		$ 20,800
Assets held for sale, fair value								$ 42,500
Proceeds from sale of oil and gas properties	$ 25,800