SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Drilling revenues (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
DRILLING REVENUES
Reimbursements received	$ 179.9	$ 125.9	$ 302.2
Early termination revenue	$ 29.4	$ 219.0	$ 222.3

Repayment received or receivable for expenses incurred on behalf of a client or customer, other than those reimbursements received by landlords from tenants.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 45
-Section 45
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=68075638&loc=d3e60722-111653

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Balance Type:	credit
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