Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Other Assets, Total	$ 214,028		$ 214,028	$ 214,028		$ 345,012
Marketable Securities, Total	633,551		633,551	633,551		9,353
Marketable Securities, Gain (Loss), Total	526,243	$ 71		$ 521,577	$ 1,574
Revision of Prior Period, Reclassification, Adjustment [Member]
Other Assets, Total						$ (9,400)
Other Income	$ (100)		$ (1,600)