Note 20 - Fair Value Measurements and Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2021

Notes Tables

Fair Value Measurements, Recurring and Nonrecurring [Table Text Block]

			Fair Value Measurements at December 31, 2021
	Fair Value at December 31, 2021		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Recurring
Marketable securities
U.S. Treasury notes	$	225,792	$	225,792	$	—	$	—
U.S. Government sponsored enterprise securities		113,944		113,944		—		—
Other
Liability-classified restricted stock awards		702		702		—		—
Total recurring	$	340,438	$	340,438	$	—	$	—
Nonrecurring
Corn and palladium inventory	$	566	$	566	$	—	$	—

			Fair Value Measurements at December 31, 2020
	Fair Value at December 31, 2020		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Nonrecurring
Finished goods inventory	$	866	$	235	$	631	$	—

Schedule of Available-for-sale Securities Reconciliation [Table Text Block]

	Maturity	Amortized Cost Basis		Gross Unrealized Losses			Fair Value
Short-term marketable securities
U.S. Treasury notes	Within one year	$	226,136	$	(344	)	$	225,792
U.S. Government-sponsored enterprise securities	Within one year		49,618		(70	)		49,548
Total		$	275,754	$	(414	)	$	275,340
Long-term marketable securities
U.S. Government-sponsored enterprise securities	Within two years	$	64,596	$	(200	)	$	64,396

Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]

	Carrying Value		Estimated Fair Value
2021 Bonds	$	68,155	$	68,380