Consolidated Statements of Equity (Unaudited) (Parentheticals) - $ / shares	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Class A
Statements of Equity
Distributions declared per share (in dollars per share)	$ 0.1563	$ 0.1562
Class C
Statements of Equity
Distributions declared per share (in dollars per share)	$ 0.1337	$ 0.1329

Distribution of earnings in the form of cash, property or capital stock declared by the board of directors to be distributed to shareholders.

No definition available.

Name:	cpa18_DistributionsDeclaredPerShare
Namespace Prefix:	cpa18_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration