Note 12 - Quarterly Financial Information (Unaudited) - Schedule of Quarterly Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues	$ 4,016	$ 6,102	$ 2,871	$ 4,823	$ 39,725	$ 1,775	$ 1,448	$ 5,887	$ 17,812	$ 48,835	$ 20,653
Net Loss	$ (60,493)	$ (46,115)	$ (38,607)	$ (37,599)	$ (2,622)	$ (37,592)	$ (37,629)	$ (31,054)	$ (182,814)	$ (108,897)	$ (101,252)
Basic and diluted net loss per share (in dollars per share)	$ (0.34)	$ (0.26)	$ (0.24)	$ (0.24)	$ (0.02)	$ (0.34)	$ (0.34)	$ (0.28)	$ (1.09)	$ (0.94)	$ (0.98)