Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash - Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Continuous Unrealized Loss Position, Less than 12 Months	$ 45,331	$ 118,391
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(15)	(114)
Continuous Unrealized Loss Position, 12 Months or Longer	19,292	71,373
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(290)	(1,527)
Unrealized Loss Position, Total	64,623	189,764
Unrealized Loss Position, Accumulated Loss, Total	(305)	(1,641)
Corporate Debt Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months	0	20,792
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(19)
Continuous Unrealized Loss Position, 12 Months or Longer	14,236	70,806
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(286)	(1,520)
Unrealized Loss Position, Total	14,236	91,598
Unrealized Loss Position, Accumulated Loss, Total	(286)	(1,539)
US Treasury and Government Short-Term Debt Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months	45,331
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(15)
Continuous Unrealized Loss Position, 12 Months or Longer	4,883
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(2)
Unrealized Loss Position, Total	50,214
Unrealized Loss Position, Accumulated Loss, Total	(17)
US Government Agencies Short-Term Debt Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months		97,599
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(95)
Continuous Unrealized Loss Position, 12 Months or Longer		0
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Unrealized Loss Position, Total		97,599
Unrealized Loss Position, Accumulated Loss, Total		(95)
Auction Rate Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months	0	0
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Continuous Unrealized Loss Position, 12 Months or Longer	173	567
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(2)	(7)
Unrealized Loss Position, Total	173	567
Unrealized Loss Position, Accumulated Loss, Total	$ (2)	$ (7)