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Fair Value of Financial Instruments - Additional Information (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2023
Sandoval Flats [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Unrealized gains (losses) from property loan held for sale | $ 0 |
Governmental Issuer Loans [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Available for Sale Security and Property Loan Receivable, Maximum Exposure | 226,700,000 | $ 225,700,000
Taxable Governmental Issuer Loan [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Available for Sale Security and Property Loan Receivable, Maximum Exposure | $ 13,900,000 | $ 12,100,000

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- Definition Available for Sale Security and Property Loan Receivable, Maximum Exposure - This represents the maximum exposure to loss related to the Available for Sale Securities and Property Loan Receivables. + References No definition available. + Details
Name: | ghi_AvailableForSaleSecurityAndPropertyLoanReceivableMaximumExposure
Namespace Prefix: | ghi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Unrealized gains (losses) from property loan held for sale. + References No definition available. + Details
Name: | ghi_UnrealizedGainsLossesFromPropertyLoanHeldForSale
Namespace Prefix: | ghi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=ghi_SandovalFlatsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_DebtInstrumentAxis=ghi_GovernmentalIssuerLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_DebtInstrumentAxis=ghi_TaxableGovernmentalIssuerLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |