Supplemental Information on Natural Gas and Oil Exploration, Development and Production Activities (Unaudited) - Costs Incurred for Property Acquisition, Exploration and Development (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Acquisitions
Acreage purchases	[1]	$ 62,075		$ 33,142	$ 73,025
Oil and gas properties	[1]	18,269		3,098,772	0
Asset retirement obligations and other	[1]	0		21,908	0
Development	[1]	1,177,526		497,795	708,268
Exploration:
Exploration drilling costs incurred	[1]	2,030		37,680	87,505
Stock-based compensation expense		82,776	[2]	55,618	57,801
Gas gathering facilities:
Development	[1]	15,097		3,595	13,337
Subtotal	[1]	1,328,659		3,725,217	903,541
Asset retirement obligations	[1],[3]	20,245		(24,064)	22,184
Total costs incurred	[1]	1,348,904		3,701,153	925,725
Expense
Exploration:
Exploration costs incurred	[1]	50,920		30,027	18,421
Stock-based compensation expense	[1]	$ 2,742	[2]	$ 2,298	$ 2,985

[1] Includes cost incurred whether capitalized or expensed.

[2] Includes $30.8 million accelerated vesting of equity grants.

[3] For additional information on non-cash investing activities associated with the MRD Merger, see Note 3