Commitments and Contingencies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($) MMBTU / d
Commitments And Contingencies Disclosure [Line Items]
Transportation commitments future minimum transportation fees due three months change | $	$ 476.3
Period of transportation commitments future minimum transportation fees due three months change	14 years
Natural Gas | Minimum
Commitments And Contingencies Disclosure [Line Items]
Transportation and gathering commitments contingent upon pipeline construction or modification, term of contract	2 years
Oil and Gas Delivery Commitments and Contracts, Daily Production	1,000
Natural Gas | Maximum
Commitments And Contingencies Disclosure [Line Items]
Transportation and gathering commitments contingent upon pipeline construction or modification, term of contract	5 years
Oil and Gas Delivery Commitments and Contracts, Daily Production	40,000