Derivative Instruments and Hedging Activities (Schedule of Gain or Loss on Derivative Contracts) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative contracts	$ 251,969	$ (67,260)
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative contracts	251,969	(67,260)
Not Designated as Hedging Instrument | Gain on contingent consideration arrangements
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative contracts	1,475	0
Not Designated as Hedging Instrument | Commodity - Oil
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative contracts	257,323	(68,369)
Not Designated as Hedging Instrument | Commodity - Natural gas
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative contracts	$ (6,829)	$ 1,109