Note 7 - Fair Value Measurements - Reconciles Net Loss to Unrealized Loss on Equity Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net gain (loss) recognized during the period on equity securities	$ 11,797	$ (3,745)	$ (0)
Less: Net gain (loss) recognized during the period on equity securities sold during the period	647	(534)
Unrealized gain (loss) recognized during the reporting period on equity securities still held at the reporting date	$ 11,150	$ (3,211)