Consolidated Balance Sheets (Parentheticals) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Acquisition Fees, Accumulated Amortization	$ 34,844	$ 39,866
Property Purchase Costs, Accumulated Amortization	$ 67,421	$ 67,924

Accumulated Amortization of Deferred Reimbursement Acquisition Costs

No definition available.

Name:	crpiv_AccumulatedAmortizationOfDeferredReimbursementAcquisitionCosts
Namespace Prefix:	crpiv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant