Note 9 - Business Segments - Reconciling Information Between Reportable Segments and Consolidated Totals (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Total consolidated revenues	$ 178,299	$ 179,364	$ 362,322	$ 369,262
Operating income	36,633	53,152	91,226	112,648
Interest income	189	362	302	606
Interest expense, net	(15,846)	(14,540)	(30,190)	(29,463)
Derivatives and foreign currency transaction gains (losses)	(529)	1,703	(2,128)	3,041
Income attributable to sale of tax benefits	3,556	4,356	10,917	10,513
Other non-operating income (expense), net	7,373	6	7,353	(86)
Total consolidated income before income taxes and equity in income of investees	31,376	45,039	77,480	97,259
Intersegment Eliminations [Member]
Total consolidated revenues	11,453	16,565	36,280	32,778
Consolidation, Eliminations [Member]
Total consolidated revenues	$ (11,453)	$ (16,565)	$ (36,280)	$ (32,778)