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Summary of Significant Accounting Policies - Advance to operators (Details)	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
Advance payments to operators, term	90 days

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- Definition

Term in which the Company expects advance payments to be applied by oil and gas operators against joint interest billings for its share of drilling operations

+ References

No definition available.

+ Details

Name:	grnt_AdvancePaymentsToOperatorsTerm
Namespace Prefix:	grnt_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

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- References

No definition available.

+ Details

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