RELINQUISHMENT AGREEMENT (Details) (USD $)	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Sep. 30, 2012	Sep. 30, 1998
RELINQUISHMENT AGREEMENT [Abstract]
Term of relinquishment agreement			15 years
Period following the end of the first three-month period after the relinquishment date upon which senior relinquishment payments start			25 days
Period following the end of the first six-month period after the relinquishment date upon which junior relinquishment payments start			25 days
Relinquishment payment rate as a percent of revenues			2.50%
Relinquishment liability	$ 97,500,000		$ 97,500,000		$ 120,800,000	$ 549,100,000
Accretion of discount to the relinquishment liability	1,244,000	2,062,000	2,487,000	4,124,000
Relinquishment Payments [Abstract]
Principal			22,429,000	23,136,000
Accretion of discount			3,306,000	4,904,000
Total relinquishment payments			25,700,000	28,100,000
Accrued relinquishment payments	$ 12,300,000		$ 12,300,000		$ 13,300,000