INVESTMENTS IN EQUITY INVESTEES (Details) (USD $) In Thousands	Jun. 30, 2011	Sep. 30, 2010
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	$ 172,977	$ 169,234
Steckman Ridge [Member]
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	136,029	134,359
Iroquois [Member]
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	25,652	24,585
Other Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Investments in equity investees	$ 11,296	$ 10,290