Note 4 - Fair Value Measurements - Financial Assets and Liabilities, Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Total Fair Value	$ 716,714	$ 466,439
Assets, fair value	771,550	510,372
Fair Value, Inputs, Level 1 [Member]
Assets, fair value	190,350	59,395
Fair Value, Inputs, Level 2 [Member]
Assets, fair value	580,633	449,266
Fair Value, Inputs, Level 3 [Member]
Assets, fair value	567	1,711
Money Market Funds [Member]
Total Fair Value	135,514	15,462
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	135,514	15,462
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	0	0
Certificates of Deposit [Member]
Total Fair Value	127,123	130,467
Certificates of Deposit [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	0	0
Certificates of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	127,123	130,467
Certificates of Deposit [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	0	0
Corporate Debt Securities [Member]
Total Fair Value	95,101	292,586
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	95,101	292,586
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	0	0
US Government Agencies Short-Term Debt Securities [Member]
Total Fair Value	358,409	8,285
US Government Agencies Short-Term Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	0	0
US Government Agencies Short-Term Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	358,409	8,285
US Government Agencies Short-Term Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	0	0
Commercial Paper [Member]
Total Fair Value		17,928
Commercial Paper [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value		0
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value		17,928
Commercial Paper [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value		0
Auction Rate Securities [Member]
Total Fair Value	567	1,711
Auction Rate Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	0	0
Auction Rate Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	0	0
Auction Rate Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	567	1,711
Mutual Fund [Member]
Total Fair Value	54,836	43,933
Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	54,836	43,933
Mutual Fund [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	0	0
Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	$ 0	$ 0