Note 19 - Business Segments - Reconciling Information Between Reportable Segments and Consolidated Totals (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	[1]									$ 746,044	$ 719,267	$ 692,812
Operating income (loss)		$ 54,472	$ 38,719	$ 46,880	$ 53,725	$ 67,982	$ 25,902	$ 36,633	$ 54,593	193,796	185,110	205,018
Interest income		320	482	420	293	458	214	189	113	1,515	974	988
Interest expense, net		(17,568)	(20,076)	(21,517)	(21,223)	(22,034)	(18,700)	(15,846)	(14,344)	(80,384)	(70,924)	(54,142)
Derivatives and foreign currency transaction gains (losses)		(72)	205	19	472	(2,250)	(383)	(529)	(1,599)	624	(4,761)	2,654
Income attributable to sale of tax benefits		4,415	4,056	4,637	7,764	4,020	4,066	3,556	7,361	20,872	19,003	17,878
Other non-operating income (expense), net		(482)	244	1,027	91	117	309	7,373	(20)	880	7,779	(1,666)
Income from operations before income tax and equity in earnings (losses) of investees		$ 41,085	$ 23,630	$ 31,466	$ 41,122	$ 48,293	$ 11,408	$ 31,376	$ 46,104	137,303	137,181	170,730
Intersegment Eliminations [Member]
Revenue										84,614	48,817	109,040
Consolidation, Eliminations [Member]
Revenue										$ (84,614)	$ (48,817)	$ (109,040)

[1] Revenues as reported in the geographic area in which they originate.