Debt Instrument, Extension Period

No definition available.

Name:	cpa18_DebtInstrumentExtensionPeriod
Namespace Prefix:	cpa18_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtPercentageBearingFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtPercentageBearingVariableInterestRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow from amounts received from issuance of long-term debt that is wholly or partially secured by collateral. Excludes proceeds from tax exempt secured debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfSecuredDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=cpa18_StudentHousingPropertyInMalagaSpainMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=cpa18_StudentHousingDevelopmentSwanseaUnitedKingdomMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=cpa18_StudentHousingPropertyInPortoPortugalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=cpa18_EuroInterbankOfferingRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=cpa18_StudentHousingInPamplonaSpainMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=cpa18_StudentHousingInBilbaoSpainMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Non-Recourse Secured Debt, Net - Financing Activity (Details) - USD ($)						12 Months Ended
	Nov. 11, 2021	Sep. 30, 2021	Apr. 30, 2021	Apr. 06, 2021	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument
Proceeds from mortgage financing						$ 147,737,000	$ 96,525,000	$ 123,641,000
Construction Loans
Debt Instrument
Maximum borrowing capacity						$ 153,733,000
Malaga, Spain (b) \| Construction Loans
Debt Instrument
Interest rate (percent)					2.50%
Proceeds from mortgage financing					$ 27,261,000
Maximum borrowing capacity					27,261,000
Swansea, United Kingdom (c) \| Construction Loans
Debt Instrument
Interest rate (percent)				6.40%
Proceeds from mortgage financing					$ 28,162,000
Maximum borrowing capacity				$ 56,577,000
Debt instrument, extension period				1 year
Porto, Portugal (b) (d) \| Construction Loans
Debt Instrument
Interest rate (percent)			2.80%
Proceeds from mortgage financing		$ 1,700,000	$ 16,432,000
Maximum borrowing capacity			$ 18,123,000
Porto, Portugal (b) (d) \| Construction Loans \| Euro Interbank Offering Rate
Debt Instrument
Interest rate (percent)		2.50%
Pamplona, Spain \| Construction Loans
Debt Instrument
Interest rate (percent)		2.50%
Proceeds from mortgage financing		$ 19,684,000
Maximum borrowing capacity		$ 19,684,000
Bilbao, Spain \| Construction Loans
Debt Instrument
Interest rate (percent)	2.50%
Proceeds from mortgage financing	$ 32,088,000
Maximum borrowing capacity	$ 32,088,000