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Geographic Information and Concentrations of Risk - Additional Information (Detail) (Net Revenues, Customer Concentration, Customer One)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Net Revenues | Customer Concentration | Customer One
   
Segment Reporting Information [Line Items]    
Concentration percentage 47.50%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= nvtl_CustomerOneMember
39.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= nvtl_CustomerOneMember