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Note L - Stockholders' Equity (Details Textual) (USD $)
9 Months Ended 159 Months Ended
Dec. 28, 2014
Dec. 28, 2014
Sep. 11, 2014
Mar. 30, 2014
Jun. 05, 2013
Stockholders' Equity Note [Abstract]          
Treasury Stock, Shares, Acquired 37,661us-gaap_TreasuryStockSharesAcquired 4,647,687us-gaap_TreasuryStockSharesAcquired      
Treasury Stock, Value, Acquired, Cost Method $ 1,916,000us-gaap_TreasuryStockValueAcquiredCostMethod $ 56,800,000us-gaap_TreasuryStockValueAcquiredCostMethod      
Common Stock, Par or Stated Value Per Share $ 0.01us-gaap_CommonStockParOrStatedValuePerShare $ 0.01us-gaap_CommonStockParOrStatedValuePerShare $ 0.01us-gaap_CommonStockParOrStatedValuePerShare $ 0.01us-gaap_CommonStockParOrStatedValuePerShare  
Stock Repurchase Program, Authorized Amount     $ 6,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1    
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased 251,272us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased 251,272us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased      
Minimum Percentage of Common Stock Acquired by a Person or Group which Triggers Exercise of New Rights         15.00%nath_MinimumPercentageOfCommonStockAcquiredByAPersonOrGroupWhichTriggersExerciseOfNewRights
New Right Purchase Price         $ 100nath_NewRightPurchasePrice
Common Stock, Capital Shares Reserved for Future Issuance 6,515,345us-gaap_CommonStockCapitalSharesReservedForFutureIssuance 6,515,345us-gaap_CommonStockCapitalSharesReservedForFutureIssuance     10,188,600us-gaap_CommonStockCapitalSharesReservedForFutureIssuance