Revenue Recognition (Disaggregation) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Gathering and transportation lease revenues	$ 15,969	$ 13,168	$ 32,226	$ 25,486
Total revenues	21,855	17,039	39,345	35,575
Natural gas sales
Disaggregation of Revenue [Line Items]
Revenues	256	226	366	699
Oil sales
Disaggregation of Revenue [Line Items]
Revenues	3,811	1,584	3,072	5,046
Natural gas liquid product
Disaggregation of Revenue [Line Items]
Revenues	117	400	296	995
Gathering and transportation
Disaggregation of Revenue [Line Items]
Revenues	1,702	1,661	3,385	3,349
Production
Disaggregation of Revenue [Line Items]
Total revenues	4,184	2,210	3,734	6,740
Production | Natural gas sales
Disaggregation of Revenue [Line Items]
Revenues	256	226	366	699
Production | Oil sales
Disaggregation of Revenue [Line Items]
Revenues	3,811	1,584	3,072	5,046
Production | Natural gas liquid product
Disaggregation of Revenue [Line Items]
Revenues	117	400	296	995
Midstream
Disaggregation of Revenue [Line Items]
Gathering and transportation lease revenues	15,969	13,168	32,226	25,486
Total revenues	17,671	14,829	35,611	28,835
Midstream | Gathering and transportation
Disaggregation of Revenue [Line Items]
Revenues	$ 1,702	$ 1,661	$ 3,385	$ 3,349