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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, RISKS AND UNCERTAINTIES - International Drilling Operations (Details) | 12 Months Ended
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Sep. 30, 2018
Risk or uncertainty |
Period for which cumulative inflation rates used for considering country as highly inflationary | 3 years
Minimum |
Risk or uncertainty |
Cumulative inflation rate before a country is considered highly inflationary (as a percent) | 100.00%

X
- Definition Represents the cumulative inflation rate before a country is considered highly inflationary. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

X
- Definition Represents the period over which cumulative inflation rates are used in considering whether a country is highly inflationary. + References No definition available. + Details
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Namespace Prefix: | hp_
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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
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Namespace Prefix: |
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Balance Type: |
Period Type: |