Note 2 - Significant Accounting Policies - Activity in Gold Bullion (Details)	3 Months Ended			12 Months Ended
	Mar. 31, 2019 USD ($) oz		Mar. 31, 2018 USD ($) oz	Dec. 31, 2018 USD ($) oz
Beginning balance (Ounce) | oz	9,009,541		7,828,465	7,828,465
Gold bullion contributed (Ounce) | oz	818,971		930,477
Gold bullion distributed (Ounce) | oz	(127,849)		(28,802)
Gold bullion sold to pay expenses (Ounce) | oz	(5,584)		(4,950)
Ending balance (Ounce) | oz	9,695,079		8,725,190	9,009,541
Beginning balance, average cost	$ 11,255,129,376		$ 9,663,574,842	$ 9,663,574,842
Gold bullion contributed, average cost	1,064,902,289		1,237,667,439
Gold bullion distributed, average cost	(160,163,947)		(35,797,403)
Gold bullion sold to pay expenses, average cost	(6,987,537)		(6,136,226)
Ending balance, average cost	12,152,880,181		10,859,308,652	11,255,129,376
Beginning balance, fair value	11,547,078,166	[1]	10,149,604,427	10,149,604,427
Gold bullion contributed, fair value	1,064,902,289		1,237,667,439
Gold bullion distributed, fair value	(165,713,340)		(37,957,322)
Gold bullion sold to pay expenses, fair value	(7,285,576)		(6,537,373)
Net realized gain (loss), fair value	5,847,432		2,561,066	23,491,426
Net change in unrealized appreciation/depreciation, fair value	114,176,495		205,503,998	(194,080,795)
Ending balance, fair value	12,559,005,466	[1]	11,550,842,235	11,547,078,166	[1]
Gold bullion distributed, realized gain (loss)	5,549,393		2,159,919
Gold bullion sold to pay expenses, realized gain (loss)	298,039		401,147
Ending balance, realized gain (loss)	$ 5,847,432		$ 2,561,066	$ 23,491,426

[1] Cost of investment in gold bullion: $12,152,880,181 and $11,255,129,376, respectively.