Note 2 - Summary of Significant Accounting Policies (Details) - Activity in Redeemable Capital Shares (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Activity in Redeemable Capital Shares [Abstract]
Beginning balance (in Shares)	332,500,000	[1]	335,000,000		317,500,000
Beginning balance	$ 6,240,747		$ 9,706,654		$ 8,698,880
Shares issued (in Shares)	74,950,000		85,750,000		82,150,000
Shares issued	1,361,917		2,096,484		2,496,406
Shares redeemed (in Shares)	(63,450,000)		(88,250,000)		(64,650,000)
Shares redeemed	(1,108,223)		(2,031,644)		(1,943,269)
Redemption value adjustment			(3,530,747)		454,637
Ending balance (in Shares)	344,000,000	[1]	332,500,000	[1]	335,000,000
Ending balance			$ 6,240,747		$ 9,706,654

[1] No par value, unlimited amount authorized.