Revenue from Contracts with Customers (Revenue, Remaining Performance Obligation) (Details) - Mid-Stream - Demand fee contracts [Member] $ in Thousands	Dec. 31, 2020 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining impact to revenue	$ (2,085)
2021
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining impact to revenue	(3,501)
2022
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining impact to revenue	1,380
2023 and beyond
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining impact to revenue	$ 36
Minimum | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining term of contract	2 years
Maximum | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining term of contract	8 years