Note 6 - Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
2022	$ 607	$ 752
2023	422	547
2024	123	348
2025	25	86
2026	1	11
Thereafter	9	6
Total lease payments	1,187	1,750
Less: Interest	(47)	(80)
Present value of lease liabilities	$ 1,140	$ 1,670

Present value of lessee's discounted obligation for lease payments from finance lease and operating lease.

No definition available.

Name:	grc_LeaseLiabilityTotal
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation.

+ References

No definition available.

+ Details

Name:	grc_LesseeLeaseLiabilityPaymentsDue
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments, due after fifth fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	grc_LesseeLeaseLiabilityPaymentsDueAfterYearFive
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments due in the next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

No definition available.

+ Details

Name:	grc_LesseeLeaseLiabilityPaymentsDueNextTwelveMonths
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments, due in fifth fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	grc_LesseeLeaseLiabilityPaymentsDueYearFive
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments, due in fourth fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	grc_LesseeLeaseLiabilityPaymentsDueYearFour
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments, due in third fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	grc_LesseeLeaseLiabilityPaymentsDueYearThree
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments, due in second fiscal year following latest fiscal year.

+ References

No definition available.

+ Details

Name:	grc_LesseeLeaseLiabilityPaymentsDueYearTwo
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments.

+ References

No definition available.

+ Details

Name:	grc_LesseeLeaseLiabilityUndiscountedExcessAmount
Namespace Prefix:	grc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant