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TREASURY STOCK - Narrative (Details) (USD $)
9 Months Ended 153 Months Ended 0 Months Ended 9 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Jun. 30, 2014
Dec. 31, 2014
Apr. 22, 2014
Dec. 31, 2014
Jul. 26, 2006
Sep. 17, 2001
Equity, Class of Treasury Stock [Line Items]                
Stock authorized to repurchase under stock repurchase program (in shares)             4,000,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased 1,000,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Additional stock authorized to repurchase under stock repurchase program (in shares)             3,000,000ntct_StockRepurchaseProgramNumberOfAdditionalSharesAuthorizedToBeRepurchased  
Shares repurchased during the period, value $ 31,543,000us-gaap_PaymentsForRepurchaseOfCommonStock $ 25,033,000us-gaap_PaymentsForRepurchaseOfCommonStock            
Open market stock repurchase program                
Equity, Class of Treasury Stock [Line Items]                
Shares repurchased during the period (in shares) 243,300us-gaap_TreasuryStockSharesAcquired
/ ntct_StockRepurchaseProgramByProgramAxis
= ntct_OpenMarketStockRepurchaseProgramMember
  4,000,000us-gaap_TreasuryStockSharesAcquired
/ ntct_StockRepurchaseProgramByProgramAxis
= ntct_OpenMarketStockRepurchaseProgramMember
         
Shares repurchased during the period, value 9,400,000us-gaap_PaymentsForRepurchaseOfCommonStock
/ ntct_StockRepurchaseProgramByProgramAxis
= ntct_OpenMarketStockRepurchaseProgramMember
             
Share Repurchase Program, April 2014                
Equity, Class of Treasury Stock [Line Items]                
Shares repurchased during the period (in shares)           256,700us-gaap_TreasuryStockSharesAcquired
/ ntct_StockRepurchaseProgramByProgramAxis
= ntct_ShareRepurchaseProgramApril2014Member
   
Shares repurchased during the period, value           11,500,000us-gaap_PaymentsForRepurchaseOfCommonStock
/ ntct_StockRepurchaseProgramByProgramAxis
= ntct_ShareRepurchaseProgramApril2014Member
   
Stock repurchase program, authorized amount         100,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount
/ ntct_StockRepurchaseProgramByProgramAxis
= ntct_ShareRepurchaseProgramApril2014Member
     
Remaining stock authorized to repurchase under stock repurchase program       88,500,000us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount
/ ntct_StockRepurchaseProgramByProgramAxis
= ntct_ShareRepurchaseProgramApril2014Member
       
Restricted stock units                
Equity, Class of Treasury Stock [Line Items]                
Shares repurchased during the period (in shares) 243,063us-gaap_TreasuryStockSharesAcquired
/ ntct_StockRepurchaseProgramByProgramAxis
= us-gaap_RestrictedStockUnitsRSUMember
             
Shares repurchased during the period, value $ 10,600,000us-gaap_PaymentsForRepurchaseOfCommonStock
/ ntct_StockRepurchaseProgramByProgramAxis
= us-gaap_RestrictedStockUnitsRSUMember