XML 28 R22.htm IDEA: XBRL DOCUMENT
v3.2.0.727

Summary of Significant Accounting Policies (Additional Information) (Details) - Jun. 30, 2015 - $ / Units | Total
--- | ---
Significant Accounting Policies [Line Items] |
Minimum likelihood of tax benefits being recognized upon ultimate settlement | 50.00%
Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets | 350
Creation Baskets |
Significant Accounting Policies [Line Items] |
Number of Shares per basket | 50,000
Maximum |
Significant Accounting Policies [Line Items] |
Cash equivalents maturity period | 6 months

X
- Definition Cash Equivalents, Maturity Period + References No definition available. + Details
Name: | usl_CashEquivalentsMaturityPeriod
Namespace Prefix: | usl_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fee Paid Per Order + References No definition available. + Details
Name: | usl_FeePaidPerOrder
Namespace Prefix: | usl_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Shares per Basket. + References No definition available. + Details
Name: | usl_NumberOfSharesPerBasket
Namespace Prefix: | usl_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage Of Income Tax Examination Minimum Likelihood of Tax Benefits Being Realized Upon Settlement + References No definition available. + Details
Name: | usl_PercentageOfIncomeTaxExaminationMinimumLikelihoodOfTaxBenefitsBeingRealizedUponSettlement
Namespace Prefix: | usl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Significant Accounting Policies [Line Items] + References No definition available. + Details
Name: | usl_SignificantAccountingPoliciesLineItems
Namespace Prefix: | usl_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | invest_InvestmentSecuritiesClassAxis=usl_CreationBasketsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |