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

The percentage required per the debt agreement of priority debt to the net worth of the entity.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

Name:	hp_LettersOfCreditOutstandingNumber
Namespace Prefix:	hp_
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

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

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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

Name:	us-gaap_LettersOfCreditOutstandingAmount
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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LineOfCredit
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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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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

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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Period Type:	duration

- Details

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Balance Type:
Period Type:

- Details

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- Details

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Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=hp_LetterOfCreditOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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Balance Type:
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- Details

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SUBSEQUENT EVENTS (Details)		1 Months Ended	12 Months Ended
SUBSEQUENT EVENTS (Details)	Jul. 13, 2016 USD ($)	Nov. 13, 2018 USD ($)	Sep. 30, 2018 USD ($) letter
2016 Credit Facility
Subsequent Event
Maximum borrowing capacity	$ 300,000,000
Commitment fee (as a percent)			0.15%
Borrowing amount outstanding			$ 0
Available borrowing capacity			$ 260,700,000
2016 Credit Facility \| Minimum
Subsequent Event
Commitment fee (as a percent)	0.15%
2016 Credit Facility \| Maximum
Subsequent Event
Commitment fee (as a percent)	0.30%
Total debt to total capitalization (as a percent)	50.00%
2016 Credit Facility \| London Interbank Offered Rate (LIBOR)
Subsequent Event
Interest spread on borrowings (as a percent)			1.125%
2016 Credit Facility \| London Interbank Offered Rate (LIBOR) \| Minimum
Subsequent Event
Interest spread on borrowings (as a percent)	1.125%
2016 Credit Facility \| London Interbank Offered Rate (LIBOR) \| Maximum
Subsequent Event
Interest spread on borrowings (as a percent)	1.75%
2016 Credit Facility \| Letters of credit
Subsequent Event
Maximum borrowing capacity	$ 75,000,000
Number of letters of credit outstanding \| letter			3
Letters of credit outstanding/issued			$ 39,300,000
Subsequent Event \| 2018 Credit Facility
Subsequent Event
Maximum borrowing capacity		$ 750,000,000
Contingent increase		300,000,000
Borrowing amount outstanding		0
Letters of credit outstanding/issued		3
Available borrowing capacity		$ 712,000,000
Subsequent Event \| 2018 Credit Facility \| Forecast
Subsequent Event
Commitment fee (as a percent)		0.125%
Subsequent Event \| 2018 Credit Facility \| Minimum
Subsequent Event
Commitment fee (as a percent)		0.075%
Subsequent Event \| 2018 Credit Facility \| Maximum
Subsequent Event
Commitment fee (as a percent)		0.20%
Total debt to total capitalization (as a percent)		50.00%
Priority debt to net worth of entity (as a percent)		17.50%
Subsequent Event \| 2018 Credit Facility \| London Interbank Offered Rate (LIBOR) \| Forecast
Subsequent Event
Interest spread on borrowings (as a percent)		1.125%
Subsequent Event \| 2018 Credit Facility \| London Interbank Offered Rate (LIBOR) \| Minimum
Subsequent Event
Interest spread on borrowings (as a percent)		0.875%
Subsequent Event \| 2018 Credit Facility \| London Interbank Offered Rate (LIBOR) \| Maximum
Subsequent Event
Interest spread on borrowings (as a percent)		1.50%
Subsequent Event \| 2018 Credit Facility \| Letters of credit
Subsequent Event
Maximum borrowing capacity		$ 75,000,000
Letters of credit outstanding/issued		38,000,000
Subsequent Event \| 2016 Credit Facility
Subsequent Event
Available borrowing capacity		262,000,000
Decrease in credit facility		300,000,000
Subsequent Event \| 2016 Credit Facility \| Letters of credit
Subsequent Event
Decrease in credit facility		$ 1,300,000