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Condensed Statement of Changes in Partners' Capital (USD $)
Total
General Partner [Member]
Limited Partners [Member]
Beginning Balance at Dec. 31, 2014 $ 1,277,679,873us-gaap_PartnersCapital $ 0us-gaap_PartnersCapital
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_GeneralPartnerMember		 $ 1,277,679,873us-gaap_PartnersCapital
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_LimitedPartnerMember
Net asset value, beginning of year at Dec. 31, 2014 $ 20.15uso_NetAssetValuePerUnit    
Addition of partnership shares 3,113,839,910us-gaap_PartnersCapitalAccountContributions 0us-gaap_PartnersCapitalAccountContributions
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_GeneralPartnerMember		 3,113,839,910us-gaap_PartnersCapitalAccountContributions
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_LimitedPartnerMember
Redemption of partnership shares (1,322,555,352)us-gaap_PartnersCapitalAccountRedemptions 0us-gaap_PartnersCapitalAccountRedemptions
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_GeneralPartnerMember		 (1,322,555,352)us-gaap_PartnersCapitalAccountRedemptions
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_LimitedPartnerMember
Net income (276,690,243)us-gaap_NetIncomeLoss 0us-gaap_NetIncomeLoss
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_GeneralPartnerMember		 (276,690,243)us-gaap_NetIncomeLoss
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_LimitedPartnerMember
Ending Balance at Mar. 31, 2015 $ 2,792,274,188us-gaap_PartnersCapital $ 0us-gaap_PartnersCapital
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_GeneralPartnerMember		 $ 2,792,274,188us-gaap_PartnersCapital
/ us-gaap_PartnerCapitalComponentsAxis
= us-gaap_LimitedPartnerMember
Net asset value, end of year at Mar. 31, 2015 $ 16.87uso_NetAssetValuePerUnit