Derivative Instruments and Hedging Activities (Schedule of Cash Paid (Received) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities
Cash received (paid) for commodity derivative settlements	$ 2,613	$ (290)
Not Designated as Hedging Instrument | Gain on contingent consideration arrangements
Cash flows from investing activities
Net cash paid for settlements of contingent consideration arrangements	(40,000)	0
Crude Oil [Member] | Not Designated as Hedging Instrument
Cash flows from operating activities
Cash received (paid) for commodity derivative settlements	(1,777)	(1,542)
Commodity - Natural gas | Not Designated as Hedging Instrument
Cash flows from operating activities
Cash received (paid) for commodity derivative settlements	$ 4,390	$ 1,252