XML 40 R4.htm IDEA: XBRL DOCUMENT v2.4.0.6
Schedule of Investments [Parenthetical] (United States)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Cash Equivalents [Member] | Us Treasury Bill Securities [Member]
   
Interest rate 0.10% 0.03%
Expiration date 17 January 2013 21 June 2012
Open Futures Contracts - Long | ICE Brent Crude Oil Futures CO February 2013 contracts and February 2012 contracts, expiring January 2013 and expiring January 2012
   
Expiration date January 2013 January 2012