Condensed Statements of Cash Flows (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash Flows from Operating Activities:
Net income (loss)	$ (276,690,243)us-gaap_NetIncomeLoss	$ 29,579,359us-gaap_NetIncomeLoss
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
(Increase) decrease in commodity futures trading account - cash and cash equivalents	(94,332,573)	(18,261,838)
Unrealized (gain) loss on open futures contracts	(51,633,790)	(3,654,730)
(Increase) decrease in dividends receivable	(849)	2,710
(Increase) decrease in interest receivable	0	52
(Increase) decrease in directors' fees and insurance receivable	(35,835)	(44,390)
(Increase) decrease in prepaid registration fees	(970,741)	0
(Increase) decrease in ETF transaction fees receivable	(1,000)	1,000
Increase (decrease) in General Partner management fees payable	651,175	(14,171)
Increase (decrease) in professional fees payable	(510,645)	(403,073)
Increase (decrease) in license fees payable	14,290	(4,423)
Increase (decrease) in directors' fees and insurance payable	(21,780)	(20,881)
Increase (decrease) in brokerage commissions payable	137,822	1,000
Net cash provided by (used in) operating activities	(423,394,169)	7,180,615
Cash Flows from Financing Activities:
Addition of partnership shares	3,130,059,912	1,722,954,545
Redemption of partnership shares	(1,245,416,310)uso_PaymentsToPartnershipRedemption	(1,752,315,729)uso_PaymentsToPartnershipRedemption
Net cash provided by (used in) financing activities	1,884,643,602	(29,361,184)
Net Increase (Decrease) in Cash and Cash Equivalents	1,461,249,433	(22,180,569)
Cash and Cash Equivalents, beginning of period	1,139,071,536	570,875,786
Cash and Cash Equivalents, end of period	$ 2,600,320,969	$ 548,695,217

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.