Note 2 - Significant Accounting Policies - Activity in Silver Bullion (Details)	3 Months Ended						6 Months Ended
	Jun. 30, 2022 USD ($) oz		Mar. 31, 2022 USD ($) oz		Jun. 30, 2021 USD ($) oz	Mar. 31, 2021 USD ($) oz	Jun. 30, 2022 USD ($) oz		Jun. 30, 2021 USD ($) oz
Beginning balance (Ounce) | oz	558,647,503		530,838,100		575,124,212	558,715,882	530,838,100		558,715,882
Beginning balance, average cost	$ 12,064,750,371		$ 11,330,688,133		$ 11,937,644,776	$ 10,472,474,303	$ 11,330,688,133		$ 10,472,474,303
Beginning balance, fair value	$ 13,862,837,819		12,254,397,545	[1]	$ 13,802,981,086	14,797,590,146	$ 12,254,397,545	[1]	$ 14,797,590,146
Silver bullion contributed (Ounce) | oz	36,747,878				28,106,701		87,944,944		192,263,810
Silver bullion contributed, average cost	$ 902,397,850				$ 765,794,167		$ 2,137,496,572		$ 5,234,465,003
Silver bullion contributed, fair value	$ 902,397,850				$ 765,794,167		$ 2,137,496,572		$ 5,234,465,003
Silver bullion distributed (Ounce) | oz	(53,945,960)				(44,335,250)		(76,682,341)		(191,415,186)
Silver bullion distributed, average cost	$ (1,174,380,285)				$ (928,983,617)		$ (1,661,468,536)		$ (3,919,057,880)
Silver bullion distributed, fair value	(1,202,027,440)				(1,177,999,610)		(1,759,001,672)		(5,056,623,118)
Silver bullion distributed, realized gain (loss)	$ 27,647,155				$ 249,015,993		$ 97,533,136		$ 1,137,565,238
Silver bullion sold to pay expenses (Ounce) | oz	(740,033)				(722,380)		(1,391,315)		(1,391,223)
Silver bullion sold to pay expenses, average cost	$ (16,082,996)				$ (15,051,815)		$ (30,031,229)		$ (28,477,915)
Silver bullion sold to pay expenses, fair value	(16,986,434)				(19,036,249)		(32,238,949)		(37,671,676)
Silver bullion sold to pay expenses, realized gain (loss)	903,438				3,984,434		2,207,720		9,193,761
Net realized gain	28,550,593		71,190,263		253,000,427	893,758,572	99,740,856		1,146,758,999
Net change in unrealized appreciation/depreciation, fair value	$ (2,536,190,240)		$ 874,378,036		$ 756,594,817	$ (2,459,779,533)	$ (1,661,812,204)		$ (1,703,184,716)
Ending balance (Ounce) | oz	540,709,388		558,647,503		558,173,283	575,124,212	540,709,388		558,173,283
Ending balance, average cost	$ 11,776,684,940		$ 12,064,750,371		$ 11,759,403,511	$ 11,937,644,776	$ 11,776,684,940		$ 11,759,403,511
Ending balance, fair value	11,038,582,148	[1]	13,862,837,819		14,381,334,638	13,802,981,086	11,038,582,148	[1]	14,381,334,638
Ending balance, realized gain (loss)	$ 28,550,593		$ 71,190,263		$ 253,000,427	$ 893,758,572	$ 99,740,856		$ 1,146,758,999

[1] Cost of investment in silver bullion: $11,776,684,940 and $11,330,688,133, respectively.