Consolidated Statements of Income (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Available Cash Distributions	$ 7,345	$ 7,225	$ 8,132

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