Note 17 - Stock-based Compensation - Options and SARS Outstanding (Details) shares in Thousands	Dec. 31, 2017 $ / shares shares
Number of SARs outstanding (in shares)	704
SARs exercisable (in shares)	490
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 19.51
Stock Options and Stock Appreciation Rights SARs Expiring in 2018 [Member]
Number of SARs outstanding (in shares)	17
SARs exercisable (in shares)	17
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 15.58
Stock Options and Stock Appreciation Rights SARs Expiriing in 2019 [Member]
Number of SARs outstanding (in shares)	40
SARs exercisable (in shares)	40
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 14.76
Stock Options and Stock Appreciation Rights SARs Expiring in 2020 [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	$ 14.02
Stock Options and Stock Appreciation Rights SARs Expiring in 2021 [Member]
Number of SARs outstanding (in shares)	74
SARs exercisable (in shares)	74
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 15.86
Stock Options and Stock Appreciation Rights SARs Expiring in 2022 [Member]
Number of SARs outstanding (in shares)	117
SARs exercisable (in shares)	117
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 15.25
Stock Options and Stock Appreciation Rights SARs Expiring in 2023 [Member]
Number of SARs outstanding (in shares)	80
SARs exercisable (in shares)	66
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)	94
SARs exercisable (in shares)	56
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)	76
SARs exercisable (in shares)	30
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 22.99
Stock Options and Stock Appreciation Rights SARs Expiring in 2026 [Member]
Number of SARs outstanding (in shares)	88
SARs exercisable (in shares)	17
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)	45
SARs exercisable (in shares)
Weighted average exercise price of SARs outstanding (in dollars per share) | $ / shares	$ 40