Note 17 - Stock-based Compensation - Options and SARS Outstanding (Details) shares in Thousands	Dec. 31, 2020 $ / shares shares
Number of SARs outstanding (in shares)	593
SARs exercisable (in shares)	412
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 27.47
Stock Options and Stock Appreciation Rights SARs Expiring in 2021 [Member]
Number of SARs outstanding (in shares)	8
SARs exercisable (in shares)	8
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 15.84
Stock Options and Stock Appreciation Rights SARs Expiring in 2022 [Member]
Number of SARs outstanding (in shares)	42
SARs exercisable (in shares)	42
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 15.26
Stock Options and Stock Appreciation Rights SARs Expiring in 2023 [Member]
Number of SARs outstanding (in shares)	80
SARs exercisable (in shares)	80
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 15.26
Stock Options and Stock Appreciation Rights SARs Expiring in 2024 [Member]
Number of SARs outstanding (in shares)	73
SARs exercisable (in shares)	73
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 19.37
Stock Options and Stock Appreciation Rights SARs Expiring in 2025 [Member]
Number of SARs outstanding (in shares)	63
SARs exercisable (in shares)	63
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 23.00
Stock Options and Stock Appreciation Rights SARs Expiring in 2026 [Member]
Number of SARs outstanding (in shares)	79
SARs exercisable (in shares)	63
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 25.84
Stock Appreciation Rights SARs Expiring in 2027 [Member]
Number of SARs outstanding (in shares)	46
SARs exercisable (in shares)	29
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 40.00
Stock Appreciation Rights SARs Expiring in 2028 [Member]
Number of SARs outstanding (in shares)	100
SARs exercisable (in shares)	42
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 37.75
Stock Appreciation Rights SARs Expiring in 2029 [Member]
Number of SARs outstanding (in shares)	53
SARs exercisable (in shares)	12
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 37.01
Stock Appreciation Rights SARs Expiring In 2030 [Member]
Number of SARs outstanding (in shares)	49
SARs exercisable (in shares)	0
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 37.30