Derivative Instruments and Hedging Activities - Additional Information (Detail) $ in Thousands		3 Months Ended
	May. 04, 2016 counterparty	Mar. 31, 2016 USD ($)	Apr. 13, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Current portion of long-term debt		$ 459,201		$ 0
Long-term debt		$ 1,522,300		1,061,000
Maximum correlation between price of oil & natural gas in market and underlying price basis indicative in the derivative contract		100.00%
Accumulated other comprehensive income (loss)		$ 18,741		17,952	$ 70,800	$ 83,300
Accumulated other comprehensive income, to be reclassified into earnings in the next twelve months		18,700
Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income (loss)		18,700		24,000	$ 77,900	$ 86,800
Revolving credit facility
Derivative Instruments, Gain (Loss) [Line Items]
Current portion of long-term debt		175,300
Long-term debt		457,000		0
1 3⁄4% Senior Convertible Notes due 2017
Derivative Instruments, Gain (Loss) [Line Items]
Current portion of long-term debt		283,500
Long-term debt		$ 283,500		$ 279,300
Subsequent Event
Derivative Instruments, Gain (Loss) [Line Items]
Percentage of counterparty contract volume	86.00%
Subsequent Event | Fixed-Price Swaps And Costless Collars
Derivative Instruments, Gain (Loss) [Line Items]
Number of counterparties | counterparty	2
Subsequent Event | Revolving credit facility
Derivative Instruments, Gain (Loss) [Line Items]
Current portion of long-term debt			$ 175,300