Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash - Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Amortized Cost	$ 503,260	$ 553,902
Unrealized Gains	0	570
Unrealized Losses	(10,181)	(1,926)
Total Fair Value	493,079	552,546
Money Market Funds [Member]
Amortized Cost	71,159	14,328
Unrealized Gains	0	0
Unrealized Losses	0	0
Total Fair Value	71,159	14,328
Certificates of Deposit [Member]
Amortized Cost	126,532	141,478
Unrealized Gains	0	0
Unrealized Losses	0	0
Total Fair Value	126,532	141,478
Corporate Debt Securities [Member]
Amortized Cost	295,877	388,081
Unrealized Gains	0	570
Unrealized Losses	(9,812)	(1,768)
Total Fair Value	286,065	386,883
US Government Agencies Short-Term Debt Securities [Member]
Amortized Cost	7,497	7,495
Unrealized Gains	0	0
Unrealized Losses	(257)	(39)
Total Fair Value	7,240	7,456
Auction Rate Securities [Member]
Amortized Cost	2,195	2,520
Unrealized Gains	0	0
Unrealized Losses	(112)	(119)
Total Fair Value	$ 2,083	$ 2,401