Derivative Instruments - Effect of Derivative Instruments on Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Cash received (paid) on settlement of derivative instruments	$ 138,450	$ (41,631)	$ 8,056
Non-cash gain (loss) on derivative instruments	(57,642)	86,063	8,870
Gain (loss) on derivative instruments not designated as hedges	$ 80,808	$ 44,432	$ 16,926