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Geographic Information and Concentrations of Risk - Schedule of Geographic Concentration of Net Revenues (Detail) (Net Revenues, Geographic Concentration)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]    
Concentration percentage 100.00%us-gaap_ConcentrationRiskPercentage1 100.00%us-gaap_ConcentrationRiskPercentage1
United States and Canada
    
Revenues from External Customers and Long-Lived Assets [Line Items]    
Concentration percentage 96.10%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= nvtl_UnitedStatesAndCanadaMember		 91.20%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= nvtl_UnitedStatesAndCanadaMember
Latin America
    
Revenues from External Customers and Long-Lived Assets [Line Items]    
Concentration percentage 3.20%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= us-gaap_LatinAmericaMember		 1.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= us-gaap_LatinAmericaMember
Europe, Middle East, Africa and other
    
Revenues from External Customers and Long-Lived Assets [Line Items]    
Concentration percentage 0.70%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= us-gaap_EMEAMember		 6.60%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= us-gaap_EMEAMember
Asia and Australia
    
Revenues from External Customers and Long-Lived Assets [Line Items]    
Concentration percentage 0.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= nvtl_AsiaAndAustraliaMember		 1.20%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= nvtl_AsiaAndAustraliaMember