INVESTMENTS IN EQUITY INVESTEES (Details) $ in Thousands		6 Months Ended
		Mar. 31, 2016 USD ($) mi	Sep. 30, 2015 USD ($)
Schedule of Equity Method Investments [Line Items]
Investments in equity investees		$ 136,974	$ 132,002
Steckman Ridge [Member]
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	[1]	124,446	125,649
Steckman Ridge [Member] | Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Total outstanding principal balance of loans		70,400	70,400
PennEast [Member]
Schedule of Equity Method Investments [Line Items]
Investments in equity investees		$ 12,528	$ 6,353
Construction plan, project area (in miles) | mi		118

[1] Includes loans with a total outstanding principal balance of $70.4 million for both March 31, 2016 and September 30, 2015. The loans accrue interest at a variable rate that resets quarterly and are due October 1, 2023.