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v3.20.2

Note 2 - Revenue (Details Textual) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2020 USD ($) | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Revenue from Contract with Customers, Sales Returns, Percent |  |  | 2.00% | 2.00%
Contract with Customer, Liability, Revenue Recognized | $ 1,900,000 |  |  |
Contract with Customer Liability, Increase from Cash Receipts | $ 565,000 |  |  |
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] |  |  |  |
Number of Major Markets | 0 | 0 | 0 | 0
Customer Concentration Risk [Member] | Revenue Benchmark [Member] |  |  |  |
Number of Major Customers | 0 | 0 | 0 | 0
Minimum [Member] |  |  |  |
Revenue from Contract with Customer, Sales Returns Policy Term (Day) |  |  | 14 days |
Revenue from Contract with Customers, Historical Sales Returns, Percent |  |  | 1.00% |
Maximum [Member] |  |  |  |
Revenue from Contract with Customer, Sales Returns Policy Term (Day) |  |  | 1 year |
Revenue from Contract with Customers, Historical Sales Returns, Percent |  |  | 10.00% |

X
- Definition Amount of increase (decrease) in obligation to transfer good or service to customer for which consideration from customer has been received or is due, from cash receipts. + References No definition available. + Details
Name: | nhtc_ContractWithCustomerLiabilityIncreaseFromCashReceipts
Namespace Prefix: | nhtc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Represents the number of major customers accounting for 10% or more of the specified concentration risk benchmark, which includes, but not limited to, sales revenue, accounts receivable, etc. + References No definition available. + Details
Name: | nhtc_NumberOfMajorCustomers
Namespace Prefix: | nhtc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of major markets accounting for 10% or more of the specified concentration risk benchmark, which includes, but not limited to, sales revenue, accounts receivable, etc. + References No definition available. + Details
Name: | nhtc_NumberOfMajorMarkets
Namespace Prefix: | nhtc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the sales returns policy term. + References No definition available. + Details
Name: | nhtc_RevenueFromContractWithCustomerSalesReturnsPolicyTerm
Namespace Prefix: | nhtc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the percentage of historical sales returns. + References No definition available. + Details
Name: | nhtc_RevenueFromContractWithCustomersHistoricalSalesReturnsPercent
Namespace Prefix: | nhtc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the percentage of sales returns. + References No definition available. + Details
Name: | nhtc_RevenueFromContractWithCustomersSalesReturnsPercent
Namespace Prefix: | nhtc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130549-203045 + Details
Name: | us-gaap_ContractWithCustomerLiabilityRevenueRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_GeographicConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_SalesRevenueNetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |