Note 2 - Significant Accounting Policies (Details) - An Adjustment to Reclassify the Balance of Redeemable Capital Shares - USD ($) $ in Thousands	Dec. 31, 2015	[1]	Dec. 31, 2014	[1]	Jan. 01, 2014	Dec. 31, 2013		Dec. 31, 2012
Note 2 - Significant Accounting Policies (Details) - An Adjustment to Reclassify the Balance of Redeemable Capital Shares [Line Items]
Redeemable capital Shares						$ 6,271,029		$ 11,645,298
Redeemable capital Shares						(6,271,029)
Shareholders’ equity	$ 5,209,803		$ 6,213,387					$ (2,332,728)	[2]
Shareholders’ equity						6,271,029
Scenario, Previously Reported [Member]
Note 2 - Significant Accounting Policies (Details) - An Adjustment to Reclassify the Balance of Redeemable Capital Shares [Line Items]
Redeemable capital Shares						6,271,029
Scenario After Application of ASU 2013-08 [Member]
Note 2 - Significant Accounting Policies (Details) - An Adjustment to Reclassify the Balance of Redeemable Capital Shares [Line Items]
Shareholders’ equity	$ 5,209,803		$ 6,213,387	[2]	$ 6,271,029	$ 6,271,029	[2]

[1] Represents net asset value. Please refer to Note 2D.

[2] The Trust reclassified redeemable capital shares as of December 31, 2013 into shareholders' equity as part of its transition to investment company accounting effective January 1, 2014. Please refer to Note 2B.