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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Property, plant and equipment (Details) $ in Millions | 12 Months Ended
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Sep. 30, 2017 USD ($) | Sep. 30, 2016 USD ($) | Sep. 30, 2015 USD ($) item
PROPERTY, PLANT AND EQUIPMENT |  |  |
Abandonments | $ | $ 42.6 | $ 39.3 | $ 43.6
Number of idle conventional rigs decommissioned | item |  |  | 23
Contract drilling equipment | Minimum |  |  |
PROPERTY, PLANT AND EQUIPMENT |  |  |
Estimated useful lives | 4 years |  |
Contract drilling equipment | Maximum |  |  |
PROPERTY, PLANT AND EQUIPMENT |  |  |
Estimated useful lives | 15 years |  |
Real estate buildings and equipment | Minimum |  |  |
PROPERTY, PLANT AND EQUIPMENT |  |  |
Estimated useful lives | 10 years |  |
Real estate buildings and equipment | Maximum |  |  |
PROPERTY, PLANT AND EQUIPMENT |  |  |
Estimated useful lives | 45 years |  |
Other assets | Minimum |  |  |
PROPERTY, PLANT AND EQUIPMENT |  |  |
Estimated useful lives | 2 years |  |
Other assets | Maximum |  |  |
PROPERTY, PLANT AND EQUIPMENT |  |  |
Estimated useful lives | 23 years |  |

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- Definition Represents the number of idle conventional rigs that are decommissioned during the reporting period. + References No definition available. + Details
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- Definition Loss recognized as a result of the initial and subsequent write-down of a long-lived asset's carrying amount to fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84176398&loc=d3e2921-110230 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
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- Details
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- Details
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- Details
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