ORGANIZATION AND BUSINESS (Additional Information) (Details) (USD $)	1 Months Ended
	Nov. 30, 2009	Nov. 18, 2009	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements Disclosure [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			350unl_FeePaidPerOrder
Number of initially registered units on Form S-1 with the U.S. Securities and Exchange Commission	30,000,000unl_NumberOfUnitsRegisteredInPeriod
Net asset value per share		$ 50.00unl_NetAssetValuePerUnit	$ 12.60unl_NetAssetValuePerUnit	$ 13.69unl_NetAssetValuePerUnit	$ 19.63unl_NetAssetValuePerUnit	$ 18.32unl_NetAssetValuePerUnit
Number of units issued		200,000
Value of unit issued		$ 10,000,000
Commenced investment operations date	Nov. 18, 2009
Number of registered units			30,000,000unl_NumberOfRegisteredUnits
Creation Baskets [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of units per basket			50,000