Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash - Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Amortized Cost	$ 486,814	$ 474,643
Unrealized Gains	12	18
Unrealized Losses	(4,836)	(8,222)
Total Fair Value	481,990	466,439
Money Market Funds [Member]
Amortized Cost	47,814	15,462
Unrealized Gains	0	0
Unrealized Losses	0	0
Total Fair Value	47,814	15,462
Certificates of Deposit [Member]
Amortized Cost	124,043	130,467
Unrealized Gains	0	0
Unrealized Losses	0	0
Total Fair Value	124,043	130,467
Corporate Debt Securities [Member]
Amortized Cost	187,961	300,529
Unrealized Gains	1	18
Unrealized Losses	(4,267)	(7,961)
Total Fair Value	183,695	292,586
Commercial Paper [Member]
Amortized Cost	11,376	17,928
Unrealized Gains	0	0
Unrealized Losses	0	0
Total Fair Value	11,376	17,928
US Government Agencies Short-Term Debt Securities [Member]
Amortized Cost	114,970	8,487
Unrealized Gains	11	0
Unrealized Losses	(568)	(202)
Total Fair Value	114,413	8,285
Auction Rate Securities [Member]
Amortized Cost	650	1,770
Unrealized Gains	0	0
Unrealized Losses	(1)	(59)
Total Fair Value	$ 649	$ 1,711