Note 9 - Business Segments - Reconciling Information Between Reportable Segments and Consolidated Totals (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues	$ 170,499	$ 166,480	$ 553,602	$ 528,802
Operating income (loss)	38,719	25,902	139,324	117,128
Interest income	482	214	1,195	516
Interest expense, net	(20,076)	(18,700)	(62,816)	(48,890)
Derivatives and foreign currency transaction gains (losses)	205	(383)	696	(2,511)
Income attributable to sale of tax benefits	4,056	4,066	16,457	14,983
Other non-operating income (expense), net	244	309	1,362	7,662
Total consolidated income before income taxes and equity in income of investees	23,630	11,408	96,218	88,888
Segment Reconciling Items [Member]
Revenues	20,831	9,236	58,259	45,516
Consolidation, Eliminations [Member]
Revenues	$ (20,831)	$ (9,236)	$ (58,259)	$ (45,516)