XML 37 R22.htm IDEA: XBRL DOCUMENT
v3.8.0.1

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Additional Information) (Details) | Mar. 31, 2018 $ / Units
--- | ---
Significant Accounting Policies [Line Items] |
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
Prior to July 1, 2011 |
Significant Accounting Policies [Line Items] |
Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets | 350

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 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: | usl_PeriodAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |