Costs Incurred for Property Acquisition, Exploration and Development (Detail) - USD ($) $ in Thousands		9 Months Ended			12 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Dec. 31, 2014
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]
Acquisitions	[1]	$ 0			$ 404,252	[2]
Acreage purchases	[1]	45,416			226,475
Development	[1]	634,347			1,119,896
Gas gathering facilities:
Development	[1]	10,914			13,137
Subtotal	[1]	785,882			2,008,233
Asset retirement obligations		19,862	[1]	$ 7,815	56,822	[1]
Total costs incurred	[1]	805,744			2,065,055
Drilling
Exploration:
Exploration costs incurred	[1]	78,059			180,925
Expense
Exploration:
Exploration costs incurred	[1]	14,975			58,979
Stock-based compensation expense
Exploration:
Exploration costs incurred	[1]	$ 2,171			$ 4,569

[1] Includes costs incurred whether capitalized or expensed.

[2] The year ended December 31, 2014 represents the EQT assets in Virginia we received as part of the Conger Exchange transaction. The transaction was recorded at fair value and we also received $145.0 million in cash, before closing adjustments.