Note 2 - Significant Accounting Policies (Details) - Share Activity - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Activity [Abstract]
Shares issued	57,150	74,950	85,750
Shares issued	$ 859,468	$ 1,361,917	$ 2,096,484
Shares redeemed	(67,600)	(63,450)	(88,250)
Shares redeemed	$ (1,029,094)	$ (1,108,223)	$ (2,031,644)
Net decrease	(10,450)	11,500
Net decrease	$ (169,626)	$ 253,694	$ 3,530,747