Note 2 - Significant Accounting Policies - Activity in Gold Bullion (Details) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2016 USD ($) oz		Mar. 31, 2015 USD ($) oz	Dec. 31, 2015 USD ($) oz
Beginning balance (in Ounces) | oz	4,905,600		5,182,200	5,182,200
Beginning balance, average cost	$ 5,910,176		$ 6,254,868	$ 6,254,868
Beginning balance, fair value	$ 5,210,940	[1]	$ 6,214,710	6,214,710
Gold bullion contributed (in Ounces) | oz	1,360,200		331,900
Gold bullion contributed, average cost	$ 1,593,830		$ 412,281
Gold bullion contributed, fair value	$ 1,593,830		$ 412,281
Gold bullion distributed (in Ounces) | oz	(272,100)		(208,500)
Gold bullion distributed, average cost	$ (325,745)		$ (252,031)
Gold bullion distributed, fair value	(332,910)		(251,695)
Gold bullion distributed, realized gain (loss)	$ 7,165		$ (336)
Gold bullion sold to pay expenses (in Ounces) | oz	(3,200)		(3,300)
Gold bullion sold to pay expenses, average cost	$ (3,854)		$ (3,954)
Gold bullion sold to pay expenses, fair value	(3,696)		(3,987)
Gold bullion sold to pay expenses, realized gain (loss)	(158)		33
Net realized gain	7,007		(303)	(87,792)
Net change in unrealized appreciation/depreciation	$ 935,096		$ (77,196)	$ (659,078)
Ending balance (in Ounces) | oz	5,990,500		5,302,300	4,905,600
Ending balance, average cost	$ 7,174,407		$ 6,411,164	$ 5,910,176
Ending balance, fair value	7,410,267	[1]	6,293,810	5,210,940	[1]
Ending balance, realized gain (loss)	$ 7,007		$ (303)	$ (87,792)

[1] Cost of investment in gold bullion: $7,174,407 and $5,910,176, respectively.