Variable Interest Entity Arrangements (Details) - USD ($)	9 Months Ended
	Sep. 30, 2020	Apr. 03, 2018
Variable Interest Entity [Line Items]
Methodology for Determining Whether Entity is Primary Beneficiary	The two variable interests applicable to Unit include the 50% equity investment in Superior and the MSA. The MSA gives us the power to direct the activities that most significantly affect Superior's operating performance. The MSA is a separate variable interest. Under the MSA, Unit has the power to direct Superior’s most significant activities; reciprocally the equity investors lack the power to direct the activities that most affect the entity’s economic performance. Because of this, Unit is considered the primary beneficiary.
Liquidation IRR Hurdle	7.00%
Variable Interest Investment		$ 300,000,000.0
Superior Pipeline Company, L.L.C. [Member]
Variable Interest Entity [Line Items]
Date Involvement Began	Apr. 03, 2018
Lack of Recourse	Superior's creditors have no recourse to our general credit.
SP Investor Holdings, LLC [Member] | Superior Pipeline Company, L.L.C. [Member]
Variable Interest Entity [Line Items]
Ownership Percentage	50.00%
SPC Midstream Operating, L.L.C. [Member] | Superior Pipeline Company, L.L.C. [Member]
Variable Interest Entity [Line Items]
Monthly service fee	$ 260,560