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EMPLOYEE BENEFIT PLANS (Details 3) (USD $)
12 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2010
Change in plan assets      
Fair value of plan assets at beginning of year $ 67,284,000 $ 61,388,000  
Fair value of plan assets at end of year 86,718,000 67,284,000 61,388,000
DEFINED CONTRIBUTION PLAN      
Percentage of employer's contribution under 401(k)/ Thrift Plan matching the first 5 percent of participant's compensation subject to certain limitations 100.00%    
Percentage of participant's compensation eligible for employer's matching contribution 5.00%    
Annual expense incurred for defined contribution plan 26,700,000 21,000,000 14,200,000
Oil and Gas Properties
     
Change in plan assets      
Fair value of plan assets at beginning of year 275,000    
Unrealized gains relating to property still held at the reporting date 24,000    
Fair value of plan assets at end of year $ 299,000   $ 275,000