Derivative Commodity Instruments - Additional Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) counterparty	Jun. 30, 2015 USD ($)
Derivative [Line Items]
Gain on fair value of derivatives	$ (65,872)	$ (50,964)	$ (60,417)	$ (16,928)
Commodity contracts
Derivative [Line Items]
Number of counterparties, net loss position | counterparty			13
Number of counterparties, net gain position | counterparty			2
Commodity contracts | Morgan Stanley Capital Group Inc
Derivative [Line Items]
Gain on fair value of derivatives			$ 1,400
Commodity contracts | BP Corporation North America, Inc.
Derivative [Line Items]
Gain on fair value of derivatives			$ 900