Partners' Equity - Additional Information (Detail)	12 Months Ended
Dec. 31, 2012
Partnership Equity And Distribution [Line Items]
Percentage of net income attributable General Partner	1.00%
Percentage of net income attributable limited partners	99.00%
Percentage of gain on sale and refinancing allocated to General Partner	1.00%
Percentage of gain on sale and refinancing allocated to limited partners	99.00%
Priority return	10.00%
Percentage of additional gain on sale and refinancing allocated to General Partner	15.00%
Percentage of additional gain on sale and refinancing allocated to limited partners	85.00%

Name:	dtrpiii_PartnershipEquityAndDistributionLineItems
Namespace Prefix:	dtrpiii_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Percentage of additional gain on sale and refinancing allocated to general partner.

No definition available.

Name:	dtrpiii_PercentageOfAdditionalGainOnSaleAndRefinancingAllocatedToGeneralPartner
Namespace Prefix:	dtrpiii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of additional gain on sale and refinancing allocated to limited partners.

No definition available.

Name:	dtrpiii_PercentageOfAdditionalGainOnSaleAndRefinancingAllocatedToLimitedPartners
Namespace Prefix:	dtrpiii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of gain on sale and refinancing allocated to general partner.

No definition available.

Name:	dtrpiii_PercentageOfGainOnSaleAndRefinancingAllocatedToGeneralPartner
Namespace Prefix:	dtrpiii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of gain on sale and refinancing allocated to limited partners.

No definition available.

Name:	dtrpiii_PercentageOfGainOnSaleAndRefinancingAllocatedToLimitedPartners
Namespace Prefix:	dtrpiii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of net income attributable general partner.

No definition available.

Name:	dtrpiii_PercentageOfNetIncomeAttributableGeneralPartner
Namespace Prefix:	dtrpiii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of net income attributable limited partners.

No definition available.

Name:	dtrpiii_PercentageOfNetIncomeAttributableLimitedPartners
Namespace Prefix:	dtrpiii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage Of Priority Interest To Be Received On Invested Capital

No definition available.

Name:	dtrpiii_PercentageOfPriorityInterestToBeReceivedOnInvestedCapital
Namespace Prefix:	dtrpiii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration