The per share daily distribution rate declared during the period.

No definition available.

Name:	cpa18_DailyDistributionDeclaredPerShare
Namespace Prefix:	cpa18_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	cpa18_EquityDistributionsAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of shareholder servicing fees incurred for Class C shares.

+ References

No definition available.

+ Details

Name:	cpa18_ShareholderServicingFeeIncurred
Namespace Prefix:	cpa18_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The non-cash amount of shares sold but not yet settled net of costs.

+ References

No definition available.

+ Details

Name:	cpa18_UnsettledSharesNet
Namespace Prefix:	cpa18_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the declared dividend will be paid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(5))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph a

-Article 7

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph 5

-Article 9

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(5))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Details

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

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

+ Details

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

- Details

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

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassCMember
Namespace Prefix:
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Loss Per Share and Equity (Narratives) (Details) (USD $)	0 Months Ended		12 Months Ended		3 Months Ended
	Dec. 15, 2014	Sep. 19, 2014	Dec. 31, 2014	Dec. 31, 2013	Mar. 23, 2015
Stock-based Compensation
Shareholder servicing fee incurred			$ 814,000cpa18_ShareholderServicingFeeIncurred	$ 46,000cpa18_ShareholderServicingFeeIncurred
Distributions Declared
Dividend payable, date	Apr. 15, 2015	Jan. 15, 2015
Distributions payable			17,629,000	1,821,000
Class A
Stock-based Compensation
Unsettled shares, value			$ 1,500,000
Distributions Declared
Daily distribution rate	0.0016983	0.0016983
Class A \| Subsequent Event
Stock-based Compensation
Common stock, shares issued					870,829
Class C
Distributions Declared
Daily distribution rate	0.0014442	0.0014442
Class C \| Subsequent Event
Stock-based Compensation
Common stock, shares issued					9,240,744