Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2010	Dec. 31, 2009
Balance Sheets [Abstract]
Silver bullion inventory, fair value	$ 10,755,319	$ 5,185,449
Redeemable capital shares, par value	$ 0	$ 0
Redeemable capital shares, issued	359,200,000	310,700,000
Redeemable capital shares, outstanding	359,200,000	310,700,000