Derivative Financial Instruments - Derivative Instruments, Gain (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Gain (loss) on derivatives	$ 545,692	$ (119,687)
Not Designated as Hedging Instrument
Derivative [Line Items]
Changes in fair value of derivative instruments	498,147	(101,832)
Net derivative settlements(1)	60,549	(8,339)
Net premiums on options that settled during the period	(13,004)	(9,516)
Gain (loss) on derivatives	545,692	$ (119,687)
Not Designated as Hedging Instrument | Derivative Portfolio
Derivative [Line Items]
Net derivative settlements(1)	3,700
Not Designated as Hedging Instrument | Derivatives Settled
Derivative [Line Items]
Net derivative settlements(1)	$ 56,900