Percentage of total debt to total capitalization of the entity.

No definition available.

Name:	hp_DebtInstrumentPercentageTotalDebtToTotalCapitalization
Namespace Prefix:	hp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of letters of credit outstanding as of balance sheet date.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The contingent increase above the maximum borrowing capacity under the credit facility, if any one or more of the existing banks or new banks agree to provide such increased commitment amount.

+ References

No definition available.

+ Details

Name:	hp_LineOfCreditFacilityContingentIncreaseAdditionalBorrowingCapacity
Namespace Prefix:	hp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the maximum percentage of priority debt that can be allowed on the net worth of the entity.

+ References

No definition available.

+ Details

Name:	hp_MaximumLimitOfPriorityDebtOnNetWorth
Namespace Prefix:	hp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Letters Of Credit Outstanding

+ References

No definition available.

+ Details

Name:	hp_NumberOfLettersOfCreditOutstanding
Namespace Prefix:	hp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of notes exchanged per registered exchange offer.

+ References

No definition available.

+ Details

Name:	hp_PercentageOfNotesExchanged
Namespace Prefix:	hp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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-Paragraph 1
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase (decrease) of the credit facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Name:	us-gaap_DebtInstrumentAxis=hp_UnsecuredRevolvingCreditFacilityMatureNovember2023Member
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DEBT - Narrative (Details)					9 Months Ended
DEBT - Narrative (Details)	Feb. 15, 2019	Nov. 19, 2018 USD ($)	Nov. 13, 2018 USD ($)	Mar. 19, 2015 USD ($)	Jun. 30, 2019 USD ($) debt_instrument number_of_letters_of_credit	Dec. 31, 2018 USD ($)	Dec. 20, 2018 USD ($)	Sep. 30, 2018 USD ($)
Debt
Debt issued (up to)					$ 500,000,000
Debt outstanding					$ 491,651,000			$ 493,968,000
Number of letters of credit outstanding \| number_of_letters_of_credit					2
HPIDC 2025 Notes
Debt
Debt issued (up to)				$ 500,000,000
Long-term debt stated interest rate percentage				4.65%
Term of debt				10 years
Debt outstanding					$ 491,651,000	$ 12,900,000	$ 12,900,000	$ 493,968,000
2018 Credit Facility
Debt
Maximum borrowing capacity			$ 750,000,000
Contingent increase			$ 300,000,000
Commitment fee (as a percent)					0.125%
Maximum limit of priority debt on net worth			17.50%
Borrowing amount outstanding					$ 0
Available borrowing capacity					$ 740,000,000.0
2018 Credit Facility \| Minimum
Debt
Commitment fee (as a percent)			0.075%
2018 Credit Facility \| Maximum
Debt
Commitment fee (as a percent)			0.20%
Total debt to total capitalization (as a percent)			50.00%
2018 Credit Facility \| London Interbank Offered Rate (LIBOR)
Debt
Interest spread on borrowings (as a percent)					1.125%
2018 Credit Facility \| London Interbank Offered Rate (LIBOR) \| Minimum
Debt
Interest spread on borrowings (as a percent)			0.875%
2018 Credit Facility \| London Interbank Offered Rate (LIBOR) \| Maximum
Debt
Interest spread on borrowings (as a percent)			1.50%
2018 Credit Facility \| Letter of Credit
Debt
Maximum borrowing capacity			$ 75,000,000
Number of letters of credit outstanding \| debt_instrument					1
Letters of credit outstanding/issued					$ 10,000,000.0
2016 Credit Facility
Debt
Decrease in credit facility			$ 300,000,000
Unsecured Standalone Line of Credit Facility
Debt
Maximum borrowing capacity					12,000,000.0
Company 2025 Notes
Debt
Debt issued (up to)						$ 487,100,000	$ 487,100,000
Long-term debt stated interest rate percentage		4.65%
Term of debt		10 years
Percentage of notes exchanged	99.99%
Company 2025 Notes \| Maximum
Debt
Debt issued (up to)		$ 500,000,000.0
Bilateral Line of Credit with Bank, One
Debt
Letters of credit outstanding/issued					25,500,000
Bilateral Line of Credit with Bank, Two
Debt
Letters of credit outstanding/issued					$ 2,100,000