Note 3 - Cash, Cash Equivalents, Investments and Restricted Cash - Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Amortized Cost	$ 718,024	$ 474,643
Total Fair Value	716,714	466,439
Unrealized Gains	331	18
Unrealized Losses	(1,641)	(8,222)
Money Market Funds [Member]
Amortized Cost	135,514	15,462
Total Fair Value	135,514	15,462
Unrealized Gains		0
Unrealized Losses		0
Certificates of Deposit [Member]
Amortized Cost	127,123	130,467
Total Fair Value	127,123	130,467
Unrealized Gains		0
Unrealized Losses		0
Corporate Debt Securities [Member]
Amortized Cost	96,636	300,529
Total Fair Value	95,101	292,586
Unrealized Gains	4	18
Unrealized Losses	(1,539)	(7,961)
US Government Agencies Short-Term Debt Securities [Member]
Amortized Cost	358,177	8,487
Total Fair Value	358,409	8,285
Unrealized Gains	327	0
Unrealized Losses	(95)	(202)
Commercial Paper [Member]
Amortized Cost		17,928
Total Fair Value		17,928
Unrealized Gains		0
Unrealized Losses		0
Auction Rate Securities [Member]
Amortized Cost	574	1,770
Total Fair Value	$ 567	1,711
Unrealized Gains		0
Unrealized Losses		$ (59)