Derivative Instruments - Effect of Derivative Instruments on the Condensed Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash received (paid) on settlement of derivative instruments, gain (loss) on derivative instruments	$ 46,555	$ (41)	$ 114,931	$ (20,354)
Non-cash gain (loss) on derivative instruments, gain (loss) on derivative instruments	(35,495)	(3,496)	(31,965)	18,726
Gain (loss) on derivative instruments	$ 11,060	$ (3,537)	$ 82,966	$ (1,628)