Defined benefit plan effect on pension expense.

No definition available.

Name:	grc_DefinedBenefitPlanEffectOnPensionExpense
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Unrecognized Actuarial Gain (Loss) in Excess of Benefit Obligation, Percentage.

+ References

No definition available.

+ Details

Name:	grc_UnrecognizedActuarialGainLossInExcessOfBenefitObligationPercentage
Namespace Prefix:	grc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 18
-URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4587-114921

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

+ Details

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

- Definition

Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(7)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 3A
-URI https://asc.fasb.org/extlink&oid=123453770&loc=SL108413299-114919

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)(7)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

+ References

No definition available.

+ Details

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

- Details

Name:	srt_StatementScenarioAxis=grc_OnePercentagePointChangeInAssumedRateOfReturnMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=grc_OnePercentagePointIncreaseInDiscountRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=grc_OnePercentagePointDecreaseInDiscountRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=grc_AlternativeInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=grc_FillRitePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_DefinedBenefitPostretirementHealthCoverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 10 - Pensions and Other Postretirement Benefits (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	$ 6,400	$ 2,300	$ 4,600
Unrecognized Actuarial Gain (Loss) in Excess of Benefit Obligation, Percentage	10.00%
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	$ 2,300
One Percentage Point Change in Assumed Rate of Return [Member]
Defined Benefit Plan Effect On Pension Expense	$ 600
One Percentage Point Increase in Discount Rate [Member]
Defined Benefit Plan Effect On Pension Expense		$ 1,700
One Percentage Point Decrease in Discount Rate [Member]
Defined Benefit Plan Effect On Pension Expense			2,000
Defined Benefit Plan, Equity Securities [Member] \| Minimum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	22.00%
Defined Benefit Plan, Equity Securities [Member] \| Maximum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	42.00%
Fixed Income Securities [Member] \| Minimum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	50.00%
Fixed Income Securities [Member] \| Maximum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	70.00%
Alternative Investments [Member] \| Minimum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		3.00%
Alternative Investments [Member] \| Maximum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	13.00%
Defined Benefit Plan, Cash and Cash Equivalents [Member] \| Minimum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Defined Benefit Plan, Cash and Cash Equivalents [Member] \| Maximum [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	10.00%
Pension Plan [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 3,000	$ 2,300	2,300
Defined Benefit Plan, Plan Assets, Contributions by Employer	2,250	2,000
Defined Benefit Plan, Benefit Obligation, Ending Balance	55,952	82,000	86,299
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	(6,427)	$ (2,304)	$ (4,583)
Fill-Rite Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	300
Defined Benefit Plan, Benefit Obligation, Ending Balance	$ 200
Postretirement Health Coverage [Member]
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	5.00%