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Significant Accounting Policies (Detail) - Schedule of unrealized gains or losses on the Trust's silver holdings (USD $)
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Dec. 31, 2011
Dec. 31, 2010
Investment in silver - average cost $ 477,903,615 [1]   $ 477,903,615 [1]   $ 524,562,808 [1],[2] $ 329,357,195
Unrealized gain / (loss) on investment in silver (5,273,871) 0 (5,273,871) 0 18,274,489  
Investment in silver - market value $ 483,177,486   $ 483,177,486   $ 542,837,297 [2]  
[1] The cost of investment in silver at June 30, 2012 was $483,177,486 and at December 31, 2011 the market value was $542,837,297.
[2] Derived from audited Statement of Financial Condition as of December 31, 2011.