Commitments (Details)	6 Months Ended
	Jun. 30, 2018 USD_Bbl Partnership
July 2018 - March 2020 [Member]
Other Commitments [Line Items]
Capacity levels (Dekatherms per day) | Partnership	3,230
July 2018 - March 2020 [Member] | Minimum [Member]
Other Commitments [Line Items]
Demand charges (in dollars per dekatherm)	0.20
July 2018 - March 2020 [Member] | Maximum [Member]
Other Commitments [Line Items]
Demand charges (in dollars per dekatherm)	0.62
April 2020 - May 2020 [Member]
Other Commitments [Line Items]
Capacity levels (Dekatherms per day) | Partnership	2,150
Demand charges (in dollars per dekatherm)	0.20
June 2020 - May 2036 [Member]
Other Commitments [Line Items]
Capacity levels (Dekatherms per day) | Partnership	1,000
Demand charges (in dollars per dekatherm)	0.20