INVESTMENTS IN EQUITY METHOD INVESTEES (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2016 USD ($) Investor mi	Sep. 30, 2016 USD ($)
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	$ 145,169	$ 141,148
Steckman Ridge
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	122,431	123,155
Steckman Ridge | Equity Method Investee
Schedule of Equity Method Investments [Line Items]
Total outstanding principal balance of loans	70,400	70,400
PennEast
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	$ 22,738	$ 17,993
Number of investors in pipeline construction and operation | Investor	5
Construction plan, project area (in miles) | mi	120