Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $)	6 Months Ended												3 Months Ended	5 Months Ended	12 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2014 Cash Flow Hedges [Member]	Mar. 31, 2014 Cash Flow Hedges [Member]	Dec. 31, 2013 Cash Flow Hedges [Member]	Jun. 30, 2013 Cash Flow Hedges [Member]	Mar. 31, 2013 Cash Flow Hedges [Member]	Dec. 31, 2012 Cash Flow Hedges [Member]	Jun. 30, 2014 Accumulated other comprehensive loss [Member]	Dec. 31, 2014 Scenario, Forecast [Member] Natural Gas [Member] Contract	Dec. 31, 2015 Scenario, Forecast [Member] Natural Gas [Member] Contract
Derivative Instruments, Gain (Loss) [Line Items]
Maximum correlation between price of oil & natural gas in market and underlying price basis indicative in the derivative contract	100.00%
Number of Contracts no longer qualifying as cash flow hedges														3,000,000	2,000,000
Derivative expense													$ 1,500,000
Accumulated other comprehensive loss	(18,161,000)	(9,200,000)	(2,062,000)	24,500,000	10,500,000	28,800,000	(17,800,000)	(8,000,000)	(1,400,000)	25,000,000	10,500,000	28,800,000
Accumulated other comprehensive loss, to be reclassified into earnings in the next twelve months	$ 14,800,000