DERIVATIVE INSTRUMENTS, CREDIT RISK EXPOSURE (Details) (USD $)	3 Months Ended		3 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2011 External Credit Rating, Investment Grade [Member]	Dec. 31, 2011 External Credit Rating, Non Investment Grade [Member]	Dec. 31, 2011 Internally Rated Investment Grade [Member]	Dec. 31, 2011 Internally Rated Noninvestment Grade [Member]	Dec. 31, 2011 NJRES [Member]	Nov. 03, 2011 NJRES [Member]	Dec. 31, 2011 NJRES [Member] CHICAGO MERCANTILE EXCHANGE [Member]	Dec. 31, 2011 NJRES [Member] INTERCONTINENTAL EXCHANGE [Member]	Dec. 15, 2011 NJRES [Member] Long Position [Member] CHICAGO MERCANTILE EXCHANGE [Member]	Nov. 23, 2011 NJRES [Member] Long Position [Member] CHICAGO MERCANTILE EXCHANGE [Member]	Jan. 12, 2012 MF Global Potential Segregation and Compliance Shortfalls [Member]
Credit Risk Exposure [Line Items]
Gross credit exposure	$ 257,506,000		$ 188,510,000	$ 23,824,000	$ 40,072,000	$ 5,100,000
Derivative, Net Liability Position, Aggregate Fair Value	2,200,000	4,100,000
Additional Collateral, Aggregate Fair Value	600,000	1,700,000
MF Global Potential Segregation and Compliance Shortfalls													1,200,000,000
Margin Deposit Assets, Estimated Percent Lost							16.50%
Margin Deposit Assets							$ 20,200,000	$ 27,800,000	$ 10,600,000	$ 17,200,000	$ 4,000,000	$ 3,600,000