Payable to Limited Partners - Additional Information (Detail)	6 Months Ended
Jun. 30, 2015
Payables and Accruals [Abstract]
Period of payable outstanding to limited partners	Six months or longer

The time period that distributions made to limited partners has remained outstanding.

No definition available.

Name:	dtrpi_PeriodOfPayableOutstandingToLimitedPartners
Namespace Prefix:	dtrpi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration