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	72,050	48,100	63,250
Shares issued	$ 830,131	$ 590,757	$ 928,370
Shares redeemed	(99,350)	(50,700)	(244,800)
Shares redeemed	$ (1,071,599)	$ (605,982)	$ (3,341,845)
Net decrease	(27,300)	(2,600)
Net decrease	$ (241,468)	$ (15,225)	$ 2,960,794