Note 9 - Cash, Cash Equivalents, Investments and Restricted Cash - Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Amortized Cost	$ 669,084	$ 474,643
Total Fair Value	665,577	466,439
Unrealized Gains	20	18
Unrealized Losses	(3,527)	(8,222)
Money Market Funds [Member]
Amortized Cost	43,854	15,462
Total Fair Value	43,854	15,462
Unrealized Gains		0
Unrealized Losses		0
Certificates of Deposit [Member]
Amortized Cost	123,368	130,467
Total Fair Value	123,368	130,467
Unrealized Gains		0
Unrealized Losses		0
Corporate Debt Securities [Member]
Amortized Cost	133,442	300,529
Total Fair Value	130,614	292,586
Unrealized Gains	3	18
Unrealized Losses	(2,831)	(7,961)
Commercial Paper [Member]
Amortized Cost	4,976	17,928
Total Fair Value	4,976	17,928
Unrealized Gains		0
Unrealized Losses		0
US Government Agencies Short-Term Debt Securities [Member]
Amortized Cost	362,844	8,487
Total Fair Value	362,165	8,285
Unrealized Gains	17	0
Unrealized Losses	(696)	(202)
Auction Rate Securities [Member]
Amortized Cost	600	1,770
Total Fair Value	$ 600	1,711
Unrealized Gains		0
Unrealized Losses		$ (59)