Deferred Compensation Plan For Non-Employee Directors (Details)	6 Months Ended
Mar. 31, 2019
Maximum [Member]
Deferred Compensation Plan For Directors [Line Items]
Period outside directors may elect to receive shares	10 years

Period outside directors may Elect to receive shares.

No definition available.

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