Note 1 - Basis of Presentation - Stock Option Activity (Details) - Share-based Payment Arrangement, Option [Member] shares in Thousands	6 Months Ended
	Jun. 30, 2021 $ / shares shares
Outstanding (in shares) | shares	196
Outstanding, weighted average option exercise price (in dollars per share)	$ 49.69
Outstanding, weighted average grant date fair value (in dollars per share)	$ 35.03
Cancelled/Forfeited (in shares) | shares	(121)
Cancelled/Forfeited, weighted average option exercise price (in dollars per share)	$ 43.63
Cancelled/Forfeited, weighted average grant date fair value (in dollars per share)	$ 30.90
Expired (in shares) | shares	(15)
Expired, weighted average option exercise price (in dollars per share)	$ 84.34
Expired, weighted average grant date fair value (in dollars per share)	$ 62.02
Balance, June 30, 2021 (in shares) | shares	60
Balance, June 30, 2021 (in dollars per share)	$ 53.50
Balance, June 30, 2021 (in dollars per share)	$ 36.81