Commitments and Contingencies (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Long-term Purchase Commitment [Line Items]
Percentage of repurchase of limited units outstanding	20.00%
Repurchase Of Limited Units Outstanding Amount	$ 0	$ 0
Drilling Equipment [Member]
Long-term Purchase Commitment [Line Items]
Other Commitment, Due in Next Twelve Months	$ 4,000,000.0
Capital Addition Purchase Commitments [Member] | Oil and Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Long-term Purchase Commitment, Description	as part of the Superior transaction, we entered into a contractual obligation that commits us to spend $150.0 million to drill wells in the Granite Wash/Buffalo Wallow area over three years starting January 1, 2019. This amount is included in our future drilling plans. For each dollar of the $150.0 million that we do not spend (over the three year period), we would forgo receiving $0.58 of future distributions from our 50% ownership interest in our consolidated mid-stream subsidiary. If we elected not to drill or spend any money in the designated area over the three year period, the maximum amount we could forgo from distributions would be $87.0 million.
Long-term Purchase Commitment, Amount	$ 150,000,000.0
Long-term Purchase Commitment, Period	3 years
Long-term purchase commitment, purchases made	$ 8,300,000