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Significant Customers - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2014
Customer
Dec. 31, 2013
Customer
Dec. 31, 2012
Customer
Revenue, Major Customer [Line Items]      
Number of significant customer 2rbcn_NumberOfSignificantCustomers 2rbcn_NumberOfSignificantCustomers 2rbcn_NumberOfSignificantCustomers
Trade receivables 10.00%rbcn_EntityWideTradeReceivableMajorCustomerPercentageMinimum    
Accounts receivable 50.00%rbcn_EntityWideAccountsReceivableMajorCustomerPercentage 47.00%rbcn_EntityWideAccountsReceivableMajorCustomerPercentage  
Customer One [Member]      
Revenue, Major Customer [Line Items]      
Revenue 24.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerOneMember		 27.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerOneMember		 38.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerOneMember
Customer Two [Member]      
Revenue, Major Customer [Line Items]      
Revenue 12.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerTwoMember		 17.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerTwoMember		 29.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerTwoMember