Payable to Limited Partners - Additional Information (Detail)	6 Months Ended
Jun. 30, 2013
Payables And Accruals [Abstract]
Period of payable outstanding to limited partners	Six months or longer

Period of payable outstanding to limited partners.

No definition available.

Name:	dtipiv_PeriodOfPayableOutstandingToLimitedPartners
Namespace Prefix:	dtipiv_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration