Derivative Instruments and Hedging Activities - Derivative Gain (Loss) Reclassified from AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 01, 2014
Effect of derivative instruments on the Consolidated Statement of Operations
Gain (loss) related to amounts previously frozen in accumulated OCI, reclassified into income				$ (73,400)
Derivatives Designated as Hedges
Effect of derivative instruments on the Consolidated Statement of Operations
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)	$ 0	$ 0	$ (144,203)
Derivatives Designated as Hedges | Natural gas
Effect of derivative instruments on the Consolidated Statement of Operations
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)	0	0	(143,577)
Derivatives Designated as Hedges | Crude oil and condensate
Effect of derivative instruments on the Consolidated Statement of Operations
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)	$ 0	$ 0	$ (626)