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Business and Credit Concentrations (Narrative) (Detail)
9 Months Ended
Mar. 31, 2015
Jun. 30, 2014
Concentration Risk [Line Items]    
Percentage that a major customer's balance is to total accounts receivable 21.00%nssc_PercentageOfSingleSignificantCustomerBalanceToTotalAccountsReceivables 12.00%nssc_PercentageOfSingleSignificantCustomerBalanceToTotalAccountsReceivables
Concentration Risk, Percentage 12.00%us-gaap_ConcentrationRiskPercentage1