Summary of Significant Accounting Policies (Activity in Silver Bullion) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2011 oz	Jun. 30, 2011 oz
Summary of Significant Accounting Policies
Beginning balance, Ounces	358,143.9	351,136.8
Silver contributed, Ounces	43,658.9	86,720.9
Silver distributed, Ounces	(94,768.1)	(130,420.6)
Silver sold, Ounces	(424.3)	(826.7)
Ending balance, Ounces	306,610.4	306,610.4
Beginning balance, Average Cost	$ 6,464,223	$ 5,650,138
Silver contributed, Average Cost	1,769,807	3,174,587
Silver distributed, Average Cost	(1,884,272)	(2,468,315)
Silver sold, Average Cost	(8,263)	(14,915)
Ending balance, Average Cost	6,341,495	6,341,495
Beginning balance, Fair Value	13,562,906	10,755,319
Silver contributed, Fair Value	1,769,807	3,174,587
Silver distributed, Fair Value	(3,846,750)	(4,903,925)
Silver sold, Fair Value	(16,864)	(29,286)
Adjustment for realized gain, Fair Value	1,971,079	2,449,981
Adjustment for unrealized gain on silver bullion, Fair Value	(2,702,684)	(709,182)
Ending balance, Fair Value	10,737,494	10,737,494
Silver distributed, Realized Gain (Loss)	1,962,478	2,435,610
Silver sold, Realized Gain (Loss)	8,601	14,371
Ending balance, Realized Gain (Loss)	$ 1,971,079	$ 2,449,981