Reporting Segments (Assets by Segment) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 458,725	$ 486,685
Capital expenditures	858	4,867
Production
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	48,418	53,556
Capital expenditures	130	11
Midstream
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	404,967	429,523
Capital expenditures	728	4,856
Corporate
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 5,340	$ 3,606