Trust Expenses	12 Months Ended
Dec. 31, 2011
Trust Expenses [Abstract]
Trust Expenses	3 - Trust Expenses The Trust pays to the Sponsor a Sponsor's fee that accrues daily at an annualized rate equal to 0.25% of the adjusted net asset value of the Trust, paid monthly in arrears. Prior to July 1, 2010, the Sponsor's fee was accrued daily at an annualized rate equal to 0.40% of the adjusted net asset value of the Trust. The Sponsor has agreed to assume the following administrative and marketing expenses incurred by the Trust: the Trustee's fee, the Custodian's fee, NYSE Arca listing fees, Securities Exchange Commission registration fees, printing and mailing costs, audit fees and expenses, and up to $100,000 per annum in legal fees and expenses.

3 - Trust Expenses

The Trust pays to the Sponsor a Sponsor's fee that accrues daily at an annualized rate equal to 0.25% of the adjusted net asset value of the Trust, paid monthly in arrears. Prior to July 1, 2010, the Sponsor's fee was accrued daily at an annualized rate equal to 0.40% of the adjusted net asset value of the Trust. The Sponsor has agreed to assume the following administrative and marketing expenses incurred by the Trust: the Trustee's fee, the Custodian's fee, NYSE Arca listing fees, Securities Exchange Commission registration fees, printing and mailing costs, audit fees and expenses, and up to $100,000 per annum in legal fees and expenses.