Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash - Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Continuous Unrealized Loss Position, Less than 12 Months	$ 474,947	$ 118,391
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(214)	(114)
Continuous Unrealized Loss Position, 12 Months or Longer	39,974	71,373
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(597)	(1,527)
Unrealized Loss Position, Total	514,921	189,764
Unrealized Loss Position, Accumulated Loss, Total	(811)	(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	22,278	70,806
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(557)	(1,520)
Unrealized Loss Position, Total	22,278	91,598
Unrealized Loss Position, Accumulated Loss, Total	(557)	(1,539)
US Treasury and Government Short-Term Debt Securities [Member]
Continuous Unrealized Loss Position, Less than 12 Months	474,947
Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(214)
Continuous Unrealized Loss Position, 12 Months or Longer	17,351
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(35)
Unrealized Loss Position, Total	492,298
Unrealized Loss Position, Accumulated Loss, Total	(249)
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	345	567
Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(5)	(7)
Unrealized Loss Position, Total	345	567
Unrealized Loss Position, Accumulated Loss, Total	$ (5)	$ (7)