Net operating losses carryback beginning year.

No definition available.

Name:	phx_NetOperatingLossesCarrybackBeginningYear
Namespace Prefix:	phx_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Net operating losses carryback end year.

+ References

No definition available.

+ Details

Name:	phx_NetOperatingLossesCarrybackEndYear
Namespace Prefix:	phx_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Net operating losses carryback percentage.

+ References

No definition available.

+ Details

Name:	phx_NetOperatingLossesCarrybackPercentage
Namespace Prefix:	phx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Net operating losses carryback percentage of adjusted taxable income.

+ References

No definition available.

+ Details

Name:	phx_NetOperatingLossesCarrybackPercentageOfAdjustedTaxableIncome
Namespace Prefix:	phx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Net operating losses carryback term.

+ References

No definition available.

+ Details

Name:	phx_NetOperatingLossesCarrybackTerm
Namespace Prefix:	phx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Net operating losses percentage of increase limitation on interest expense deductibility.

+ References

No definition available.

+ Details

Name:	phx_NetOperatingLossesPercentageOfIncreaseLimitationOnInterestExpenseDeductibility
Namespace Prefix:	phx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Refundable alternative minimum tax credits.

+ References

No definition available.

+ Details

Name:	phx_RefundableAlternativeMinimumTaxCredits
Namespace Prefix:	phx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ 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.(h)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

+ Details

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

- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I)
-URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

+ Details

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

- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the income tax rates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I)
-URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

+ Details

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

- 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

Name:	us-gaap_IncomeTaxContingencyLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e38679-109324

+ Details

Name:	us-gaap_IncomeTaxExpenseBenefit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_EnvironmentalRemediationContingencyAxis=phx_CoronavirusAidReliefAndEconomicSecurityActMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Income Taxes (Narrative) (Details) - USD ($)		3 Months Ended		6 Months Ended
Income Taxes (Narrative) (Details) - USD ($)	Mar. 27, 2020	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Income Tax Contingency [Line Items]
Effective tax rate		(25.00%)	(6.00%)	(27.00%)	24.00%
Income tax (benefit) provision		$ (6,987,000)	$ (130,000)	$ (6,733,000)	$ 3,441,000
Current tax rate				21.00%
CARES Act [Member]
Income Tax Contingency [Line Items]
Net operating losses carryback term	5 years
Net operating losses carryback term start year	2018
Net operating losses carryback term end year	2020
Net operating losses carryback percentage.	80.00%
Net operating losses percentage of increase limitation on interest expense deductibility	30.00%
Net operating losses carryback percentage of adjusted taxable income	50.00%
Refundable tax credit due to AMT credits		1,400,000
Income tax (benefit) provision		$ (295,544)
Previously enacted tax rate	34.00%