Additional Letter Of Credit Outstanding, Amount

No definition available.

Name:	gnl_AdditionalLetterOfCreditOutstandingAmount
Namespace Prefix:	gnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Amount Outstanding, Cash Sweep Event

+ References

No definition available.

+ Details

Name:	gnl_DebtInstrumentAmountOutstandingCashSweepEvent
Namespace Prefix:	gnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Amount Outstanding Increased, Cash Sweep Event

+ References

No definition available.

+ Details

Name:	gnl_DebtInstrumentAmountOutstandingIncreasedCashSweepEvent
Namespace Prefix:	gnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Cash Sweep Event, Rollover Reserve Maximum Amount

+ References

No definition available.

+ Details

Name:	gnl_DebtInstrumentCashSweepEventRolloverReserveMaximumAmount
Namespace Prefix:	gnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of Real Estate Properties, Encumbered

+ References

No definition available.

+ Details

Name:	gnl_NumberOfRealEstatePropertiesEncumbered
Namespace Prefix:	gnl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Real Estate and Accumulated Depreciation, Unencumbered Assets

+ References

No definition available.

+ Details

Name:	gnl_RealEstateandAccumulatedDepreciationUnencumberedAssets
Namespace Prefix:	gnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_MortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=gnl_U.S.MultiTenantMortgageLoanIIIMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=gnl_MultiTenantMortgageLoanIVMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_USD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Mortgage Notes Payable, Net - Narrative (Details) $ in Millions	Mar. 31, 2023 USD ($) property	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)
Debt Instrument [Line Items]
Carrying value of encumbered assets	$ 2,200.0
Mortgage Notes Payable
Debt Instrument [Line Items]
Encumbered Properties \| property	111
Multi-Tenant Mortgage Loan III \| Letter of Credit
Debt Instrument [Line Items]
Balance outstanding with cash sweep event trigger			$ 0.9
Outstanding balance increased with cash sweep event trigger	$ 1.2	$ 1.3
Multi-Tenant Mortgage Loan III \| Mortgage Notes Payable
Debt Instrument [Line Items]
Balance outstanding with cash sweep event trigger	98.5
Letters of credit outstanding					$ 3.2
Multi-Tenant Mortgage Loan IV \| Mortgage Notes Payable
Debt Instrument [Line Items]
Balance outstanding with cash sweep event trigger	97.5
Rollover reserve aggregate cap	$ 0.8
USD \| Mortgage Notes Payable
Debt Instrument [Line Items]
Encumbered Properties \| property	54
USD \| Multi-Tenant Mortgage Loan III \| Mortgage Notes Payable
Debt Instrument [Line Items]
Encumbered Properties \| property	7
USD \| Multi-Tenant Mortgage Loan IV \| Mortgage Notes Payable
Debt Instrument [Line Items]
Encumbered Properties \| property	16
Line of Credit
Debt Instrument [Line Items]
Carrying value of encumbered assets	$ 1,300.0
Line of Credit \| Multi-Tenant Mortgage Loan III \| Mortgage Notes Payable
Debt Instrument [Line Items]
Letters of credit outstanding				$ 7.4	$ 7.4
Additional letters of credit outstanding				$ 4.2