Note 5 - Stockholders' Equity and Dilutive Equity Instruments - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Balance	$ 759,738	$ 890,000	$ 823,272	$ 1,016,410
Balance	734,612	853,577	734,612	853,577
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(1,082)	581	(804)	(236)
Pension benefits recognized in OCI	(207)	525	(485)	1,342
Balance	$ (1,289)	$ 1,106	$ (1,289)	$ 1,106