Transactions with Related Parties - Loan from USDG (Details) - CAD	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Related Party Transactions [Abstract]
Limited partner interest (as a percent)	100.00%	100.00%
USDG Loan [Member] \| USDTC [Member] \| Subsidiary of Common Parent [Member]
Related Party Transaction [Line Items]
Initial loan amount of unsecured loan facility	CAD 45,200,000.0
Capacity to increase unsecured loan facility	CAD 70,000,000.0

The number of units or percentage investment held by one or more members or limited partners of the LLC or LP.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

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Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- References

No definition available.

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- Definition

Line Of Credit Maximum Borrowing Capacity Including Accordion Option

+ References

No definition available.

+ Details

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Namespace Prefix:	usdp_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Details

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- Details

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- Details

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