SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - LOAN RECEIVABLE (Details) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable in other current assets	$ 8,900,000	$ 7,800,000
Loans receivable in other noncurrent assets	$ 40,400,000	39,500,000
Establishment of allowance for doubtful accounts, customer account balances, days outstanding (more than)	60 days
Allowance for doubtful accounts	$ 0	$ 0
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable term	3 years
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable term	10 years