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Note 9 - Business Segment Information (Details)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Note 9 - Business Segment Information (Details) [Line Items]    
Number of Reportable Segments 1us-gaap_NumberOfReportableSegments  
Number of Countries in which Entity Operates 150us-gaap_NumberOfCountriesInWhichEntityOperates  
UNITED STATES    
Note 9 - Business Segment Information (Details) [Line Items]    
Long Lived Assets, Percent 95.00%grc_LongLivedAssetsPercent
/ us-gaap_StatementGeographicalAxis
= country_US
96.00%grc_LongLivedAssetsPercent
/ us-gaap_StatementGeographicalAxis
= country_US