Condensed Consolidated Statements of Income (Unaudited) (Parentheticals) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Distributions of available cash	$ 1,848	$ 1,905

Amount of cash generated from operations, excluding capital proceeds, as reduced by operating expenses and debt service, excluding prepayments and lump-sum or "balloon" payments, that is available to distribute to the advisor.

No definition available.

Name:	cpa18_DistributionsofAvailableCash
Namespace Prefix:	cpa18_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration