Percentage of total debt to total capitalization of the entity.

No definition available.

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- 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

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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

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Namespace Prefix:	hp_
Data Type:	xbrli:integerItemType
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- 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_
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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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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_
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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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Balance Type:	na
Period Type:	duration

- Definition

Fair value amount of debt instrument that was repurchased.

+ References

No definition available.

+ Details

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

- 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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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.

+ References

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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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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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

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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

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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

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DEBT - Narrative (Details)			12 Months Ended
DEBT - Narrative (Details)	Feb. 15, 2019	Nov. 13, 2018 USD ($)	Sep. 30, 2019 USD ($) number_of_letters_of_credit	Oct. 31, 2019 USD ($)	Sep. 27, 2019 USD ($)	Dec. 20, 2018 USD ($)	Nov. 19, 2018 USD ($)	Sep. 30, 2018 USD ($)	Mar. 19, 2015 USD ($)
Debt Instrument [Line Items]
Aggregate principal amount			$ 479,356,000					$ 493,968,000
Line of Credit
Debt Instrument [Line Items]
Number of letters of credit outstanding \| number_of_letters_of_credit			2
Line of Credit \| Subsequent Event
Debt Instrument [Line Items]
Letters of credit outstanding				$ 24,800,000
HPIDC 2025 Notes
Debt Instrument [Line Items]
Interest rate									4.65%
Aggregate principal amount					$ 12,900,000	$ 12,900,000
Debt redemption amount					$ 14,600,000
HPIDC 2025 Notes \| Maximum
Debt Instrument [Line Items]
Face amount of debt									$ 500,000,000
Company 2025 Notes
Debt Instrument [Line Items]
Face amount of debt						$ 487,100,000
Interest rate							4.65%
Percent of notes exchanged	99.99%
Company 2025 Notes \| Maximum
Debt Instrument [Line Items]
Face amount of debt							$ 500,000,000
2018 Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 750,000,000
Increase in aggregate commitments subject to satisfaction of certain commitments from new or existing lenders		$ 300,000,000
Commitment fee rate			0.125%
Maximum limit of priority debt on net worth		17.50%
Borrowings outstanding			$ 0
Available borrowing capacity			$ 750,000,000.0
2018 Credit Facility \| Minimum
Debt Instrument [Line Items]
Commitment fee rate		0.075%
2018 Credit Facility \| Maximum
Debt Instrument [Line Items]
Commitment fee rate		0.20%
Total debt to total capitalization ratio		50.00%
2018 Credit Facility \| LIBOR
Debt Instrument [Line Items]
Interest rate spread			1.125%
2018 Credit Facility \| LIBOR \| Minimum
Debt Instrument [Line Items]
Interest rate spread		0.875%
2018 Credit Facility \| LIBOR \| Maximum
Debt Instrument [Line Items]
Interest rate spread		1.50%
2018 Credit Facility \| Letters of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 75,000,000
Unsecured Credit Facility Dated as of July 13, 2016
Debt Instrument [Line Items]
Amount of credit facility terminated		$ 300,000,000.0
Letter of Credit - Instrument 1 \| Line of Credit
Debt Instrument [Line Items]
Letters of credit outstanding			$ 25,500,000
Letter of Credit - Instrument 2 \| Line of Credit
Debt Instrument [Line Items]
Letters of credit outstanding			2,100,000
Unsecured Standalone Line of Credit Facility
Debt Instrument [Line Items]
Aggregate principal amount			11,500,000
Maximum borrowing capacity			$ 20,000,000.0