Note 2 - Significant Accounting Policies - Activity in Silver Bullion (Details)	3 Months Ended
	Mar. 31, 2022 USD ($) oz		Mar. 31, 2021 USD ($) oz
Beginning balance (Ounce) | oz	530,838,100		558,715,882
Beginning balance, average cost	$ 11,330,688,133		$ 10,472,474,303
Beginning balance, fair value	$ 12,254,397,545	[1]	$ 14,797,590,146
Silver bullion contributed (Ounce) | oz	51,197,066		164,157,109
Silver bullion contributed, average cost	$ 1,235,098,722		$ 4,468,670,836
Silver bullion contributed, fair value	$ 1,235,098,722		$ 4,468,670,836
Silver bullion distributed (Ounce) | oz	(22,736,381)		(147,079,936)
Silver bullion distributed, average cost	$ (487,088,251)		$ (2,990,074,263)
Silver bullion distributed, fair value	(556,974,232)		(3,878,623,508)
Silver bullion distributed, realized gain (loss)	$ 69,885,981		$ 888,549,245
Silver bullion sold to pay expenses (Ounce) | oz	(651,282)		(668,843)
Silver bullion sold to pay expenses, average cost	$ (13,948,233)		$ (13,426,100)
Silver bullion sold to pay expenses, fair value	(15,252,515)		(18,635,427)
Silver bullion sold to pay expenses, realized gain (loss)	1,304,282		5,209,327
Net realized gain	71,190,263		893,758,572
Net change in unrealized appreciation/depreciation, fair value	$ 874,378,036		$ (2,459,779,533)
Ending balance (Ounce) | oz	558,647,503		575,124,212
Ending balance, average cost	$ 12,064,750,371		$ 11,937,644,776
Ending balance, fair value	13,862,837,819	[1]	13,802,981,086
Ending balance, realized gain (loss)	$ 71,190,263		$ 893,758,572

[1] Cost of investment in silver bullion: $12,064,750,371 and $11,330,688,133, respectively.