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v3.19.2

Concentrations of Credit Risk and Major Customers (Details) - Accounts Receivable [Member] | 12 Months Ended
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Mar. 31, 2019 | Mar. 31, 2018
Three largest receivable balances | 78.20% | 72.90%
Customer A [Member] |  |
Three largest receivable balances | 61.10% | 54.90%
Customer B [Member] |  |
Three largest receivable balances | 10.20% | 9.00%
Customer C [Member] |  |
Three largest receivable balances | 6.90% | 9.00%

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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
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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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: |