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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, RISKS AND UNCERTAINTIES - Self-Insurance (Details) $ in Millions | 12 Months Ended
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Sep. 30, 2018 USD ($)
Minimum |
Risk or uncertainty |
Insurance coverage deductibles range for claims which occur outside or inside the United States | $ 1
Maximum |
Risk or uncertainty |
Insurance coverage deductibles range for claims which occur outside or inside the United States | $ 5

X
- Definition Represents the deductible amounts of claims that are covered by insurance. + References No definition available. + Details
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Namespace Prefix: | hp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- 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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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |