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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Valuation of long-lived assets (Details)
$ in Millions
12 Months Ended
Sep. 30, 2017
USD ($)
Sep. 30, 2016
USD ($)
item
Sep. 30, 2015
USD ($)
item
U.S. Land      
VALUATION OF LONG-LIVED ASSETS      
Impairment charge for asset held for sale   $ 6.3  
Land Rigs      
VALUATION OF LONG-LIVED ASSETS      
Depreciation catch-up adjustment $ 2.2    
Land Rigs | International Land      
VALUATION OF LONG-LIVED ASSETS      
Impairment charge for asset held for use     $ 39.2
Number of impaired land rigs | item     7
Land Rigs | International Land | Assets held for sale      
VALUATION OF LONG-LIVED ASSETS      
Number of impaired land rigs | item   6  
Land Rigs | International Land | Discounted cash flow      
VALUATION OF LONG-LIVED ASSETS      
Fair value of land rigs     $ 20.6