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Note 12 - Fair Value Measurements (Details Textual) Pure in Thousands	Dec. 31, 2021	Sep. 30, 2021
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Number of Major Customers	0	0

X

- Definition

Represents the number of major customers accounting for 5% or more of the specified concentration risk benchmark, which includes, but not limited to, sales revenue, accounts receivable, etc.

+ References

No definition available.

+ Details

Name:	rgco_NumberOfMajorCustomers
Namespace Prefix:	rgco_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_AccountsReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: