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v3.19.3.a.u2

Note 6 - Leases (Details Textual) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Jan. 01, 2019
Operating Lease, Right-of-Use Asset | $ 1,260 |
Lessee, Operating Lease, Renewal Term | 5 years |
Minimum [Member] |  |
Lessee, Remaining Lease Term | 1 year |
Maximum [Member] |  |
Lessee, Remaining Lease Term | 5 years |
Accrued Expenses and Other Noncurrent Liabilities [Member] |  |
Operating Lease, Liability, Total | $ 1,250 | $ 1,600
Other Assets [Member] |  |
Operating Lease, Right-of-Use Asset |  | $ 1,600

X
- Definition Remaining term for lessee's leases. + References No definition available. + Details
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Namespace Prefix: | grc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

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- Definition Present value of lessee's discounted obligation for lease payments from operating lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of lessee's right to use underlying asset under operating lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
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- Details
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Period Type: |