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Significant Customers - Additional Information (Detail)
 3 Months Ended
Mar. 31, 2015
Customer
Mar. 31, 2014
Customer
Dec. 31, 2014
Revenue, Major Customer [Line Items]      
Number of significant customer 1rbcn_NumberOfSignificantCustomers 4rbcn_NumberOfSignificantCustomers  
Trade receivables 10.00%rbcn_EntityWideTradeReceivableMajorCustomerPercentageMinimum    
Accounts receivable 57.00%rbcn_EntityWideAccountsReceivableMajorCustomerPercentage   50.00%rbcn_EntityWideAccountsReceivableMajorCustomerPercentage
Customer One [Member] | Customer Concentration Risk [Member]      
Revenue, Major Customer [Line Items]      
Revenue 29.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerOneMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		 21.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerOneMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		  
Customer Two [Member] | Customer Concentration Risk [Member]      
Revenue, Major Customer [Line Items]      
Revenue   14.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerTwoMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		  
Customer Three [Member] | Customer Concentration Risk [Member]      
Revenue, Major Customer [Line Items]      
Revenue   11.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerThreeMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember		  
Customer Four [Member] | Customer Concentration Risk [Member]      
Revenue, Major Customer [Line Items]      
Revenue   11.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= rbcn_CustomerFourMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember