Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash - Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Continuous Unrealized Loss Position, Less than 12 Months	$ 515,395	$ 118,391
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(259)	(114)
Continuous Unrealized Loss Position, 12 Months or Longer	52,461	71,373
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(972)	(1,527)
Unrealized Loss Position, Total	567,856	189,764
Unrealized Loss Position, Accumulated Loss, Total	(1,231)	(1,641)
Corporate Debt Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months	5,436	20,792
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(9)	(19)
Continuous Unrealized Loss Position, 12 Months or Longer	51,943	70,806
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(965)	(1,520)
Unrealized Loss Position, Total	57,379	91,598
Unrealized Loss Position, Accumulated Loss, Total	(974)	(1,539)
US Treasury and Government Short-Term Debt Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months	509,959
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(250)
Continuous Unrealized Loss Position, 12 Months or Longer	0
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Unrealized Loss Position, Total	509,959
Unrealized Loss Position, Accumulated Loss, Total	(250)
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	518	567
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(7)	(7)
Unrealized Loss Position, Total	518	567
Unrealized Loss Position, Accumulated Loss, Total	$ (7)	$ (7)