Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Commitments And Contingencies Disclosure [Line Items]
Transportation commitments future minimum transportation fees due three months change	$ 628.4
Period of transportation commitments future minimum transportation fees due three months change	25 years
Minimum
Commitments And Contingencies Disclosure [Line Items]
Terms of Contingent Transportation and Gathering Contracts	5 years
Transportation and gathering commitments contingent upon construction and modification	25,000
Maximum
Commitments And Contingencies Disclosure [Line Items]
Terms of Contingent Transportation and Gathering Contracts	15 years
Transportation and gathering commitments contingent upon construction and modification	300,000