Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair value of asset retirement obligation liabilities incurred and acquired	$ 0.1	$ 1.2

Asset Retirement Obligation, Liabilities Incurred And Acquired, Fair Value Disclosure

No definition available.

Name:	rep_AssetRetirementObligationLiabilitiesIncurredAndAcquiredFairValueDisclosure
Namespace Prefix:	rep_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration