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v3.20.2

Concentrations of Credit Risk and Major Customers (Details) - Accounts Receivable [Member] | 12 Months Ended
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Mar. 31, 2020 | Mar. 31, 2019
Three largest receivable balances | 72.50% |  | 78.20% |
Customer A [Member] |  |  |  |
Three largest receivable balances | 47.40% |  | 61.10% |
Customer B [Member] |  |  |  |
Three largest receivable balances |  | [1] | 10.20% |
Customer C [Member] |  |  |  |
Three largest receivable balances | 18.40% |  | 6.90% |
Customer D [Member] |  |  |  |
Three largest receivable balances | 6.70% |  |  | [1]
[1] | not among the top three receivable balances as of respective year end.

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- Definition Percentage of loans receivable during the period. + References No definition available. + Details
Name: | hiho_LoansReceivablePercentage
Namespace Prefix: | hiho_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_AccountsReceivableMember
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Data Type: | na
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- Details
Name: | srt_MajorCustomersAxis=hiho_CustomerAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_MajorCustomersAxis=hiho_CustomerBMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_MajorCustomersAxis=hiho_CustomerCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_MajorCustomersAxis=hiho_CustomerDMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |