Annual report pursuant to Section 13 and 15(d)

Note 4 - Stockholders' Equity (Details Textual)

v2.4.1.9
Note 4 - Stockholders' Equity (Details Textual) (USD $)
1 Months Ended 12 Months Ended 0 Months Ended 1 Months Ended
Apr. 21, 2013
Apr. 21, 2009
Dec. 17, 2014
Dec. 31, 2014
Dec. 31, 2013
May 04, 2007
Oct. 19, 2007
Nov. 04, 2014
Aug. 13, 2012
Equity [Abstract]                  
Preferred Stock, Shares Authorized       5,000,000us-gaap_PreferredStockSharesAuthorized 5,000,000us-gaap_PreferredStockSharesAuthorized        
Preferred Stock, Par or Stated Value Per Share       $ 0.001us-gaap_PreferredStockParOrStatedValuePerShare $ 0.001us-gaap_PreferredStockParOrStatedValuePerShare        
Common Stock, Shares Authorized       50,000,000us-gaap_CommonStockSharesAuthorized 50,000,000us-gaap_CommonStockSharesAuthorized        
Common Stock, Par or Stated Value Per Share       $ 0.001us-gaap_CommonStockParOrStatedValuePerShare $ 0.001us-gaap_CommonStockParOrStatedValuePerShare        
Class of Warrant or Right, Number of Securities Called by Warrants or Rights       88,097us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights     3,141,499us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights    
Term Of Warrant 5 years 1 year   7 years          
Class of Warrant or Right, Exercise Price of Warrants or Rights       $ 3.5082us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1     3.52us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1    
Proceeds from Warrant Exercises       $ 4,948,000us-gaap_ProceedsFromWarrantExercises          
Stock Repurchase Program, Number of Shares Authorized to be Repurchased                 100,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Stock Repurchase Program, Authorized Amount               5,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1  
Treasury Stock, Value, Acquired, Cost Method     4,500,000us-gaap_TreasuryStockValueAcquiredCostMethod 4,661,000us-gaap_TreasuryStockValueAcquiredCostMethod 52,000us-gaap_TreasuryStockValueAcquiredCostMethod        
Treasury Stock, Value, Acquired, Cost Method, Excluding Related Party     3,000,000nhtc_TreasuryStockValueAcquiredCostMethodExcludingRelatedParty            
Treasury Stock, Shares, Acquired     359,840us-gaap_TreasuryStockSharesAcquired            
George K. Broady [Member]                  
Equity [Abstract]                  
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners               5.00%us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
/ us-gaap_TitleOfIndividualAxis
= nhtc_GeorgeKBroadyMember
 
Treasury Stock, Value, Acquired, Cost Method     1,500,000us-gaap_TreasuryStockValueAcquiredCostMethod
/ us-gaap_TitleOfIndividualAxis
= nhtc_GeorgeKBroadyMember
           
Series A Preferred Stock [Member]                  
Equity [Abstract]                  
Preferred Stock, Shares Outstanding           1,761,900us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesAPreferredStockMember
     
Preferred Stock, Dividends Per Share, Declared           $ 0.119us-gaap_PreferredStockDividendsPerShareDeclared
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesAPreferredStockMember
     
Share Price           $ 1.70us-gaap_SharePrice
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesAPreferredStockMember
     
Preferred Stock, Voting Rights           0.729      
Minimum [Member] | Series A Preferred Stock [Member]                  
Equity [Abstract]                  
Share Price           $ 10us-gaap_SharePrice
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesAPreferredStockMember
     
Initially Be Equal To [Member] | Series A Preferred Stock [Member]                  
Equity [Abstract]                  
Share Price           $ 1.70us-gaap_SharePrice
/ us-gaap_RangeAxis
= nhtc_InitiallyBeEqualToMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesAPreferredStockMember
     
Five Year Warrants [Member]                  
Equity [Abstract]                  
Class of Warrant or Right, Number of Securities Called by Warrants or Rights             149,595us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_ClassOfWarrantOrRightAxis
= nhtc_FiveYearWarrantsMember
   
Term Of Warrant             5 years    
One Year Warrants [Member]                  
Equity [Abstract]                  
Class of Warrant or Right, Number of Securities Called by Warrants or Rights             1,495,952us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_ClassOfWarrantOrRightAxis
= nhtc_OneYearWarrantsMember
   
Term Of Warrant             1 year    
Seven Year Warrants [Member]                  
Equity [Abstract]                  
Class of Warrant or Right, Number of Securities Called by Warrants or Rights       1,407,855us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_ClassOfWarrantOrRightAxis
= nhtc_SevenYearWarrantsMember
    1,495,952us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
/ us-gaap_ClassOfWarrantOrRightAxis
= nhtc_SevenYearWarrantsMember
   
Term Of Warrant             7 years    
Proceeds from Warrant Exercises       $ 4,900,000us-gaap_ProceedsFromWarrantExercises
/ us-gaap_ClassOfWarrantOrRightAxis
= nhtc_SevenYearWarrantsMember
         
Seven Year Warrants [Member] | Maximum [Member]                  
Equity [Abstract]                  
Class of Warrant or Right, Exercise Price of Warrants or Rights       $ 3.52us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= nhtc_SevenYearWarrantsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
         
Seven Year Warrants [Member] | Minimum [Member]                  
Equity [Abstract]                  
Class of Warrant or Right, Exercise Price of Warrants or Rights       $ 3.5108us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
/ us-gaap_ClassOfWarrantOrRightAxis
= nhtc_SevenYearWarrantsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember