Derivative Instruments and Hedging Activities (Schedule of Gain or Loss on Derivative Contracts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
(Gain) loss on derivative contracts	$ 27,773	$ 62,109	$ (48,544)
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
(Gain) loss on derivative contracts	27,773	62,109	(48,544)
Not Designated as Hedging Instrument | Contingent consideration arrangements
Derivative Instruments, Gain (Loss) [Line Items]
(Gain) loss on derivative contracts	2,976	(2,315)	0
Not Designated as Hedging Instrument | Warrant liability
Derivative Instruments, Gain (Loss) [Line Items]
(Gain) loss on derivative contracts	55,519	0	0
Not Designated as Hedging Instrument | Commodity - Oil
Derivative Instruments, Gain (Loss) [Line Items]
(Gain) loss on derivative contracts	(48,031)	73,313	(45,463)
Not Designated as Hedging Instrument | Commodity - Natural gas
Derivative Instruments, Gain (Loss) [Line Items]
(Gain) loss on derivative contracts	14,883	(8,889)	(3,081)
Not Designated as Hedging Instrument | Natural gas liquids
Derivative Instruments, Gain (Loss) [Line Items]
(Gain) loss on derivative contracts	$ 2,426	$ 0	$ 0