Note 14 - Guarantor Subsidiaries - Unaudited Interim Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities	$ 20,030	$ 16,383
Additions to properties, plants, and equipment	(33,071)	(17,635)
Other investing activities, net	1	(530)
Dividends paid to stockholders	(1,348)	(1,136)
Borrowings on debt	58,000	31,024
Payments on debt	(59,261)	(1,322)
Other financing activity	(38)	(1,225)
Effect of exchange rate changes on cash	95	876
Changes in cash, cash equivalents and restricted cash and cash equivalents	(15,592)	26,435
Cash, cash equivalents and restricted cash and cash equivalents at beginning of period	28,414	187,139
Cash, cash equivalents and restricted cash and cash equivalents at end of period	12,822	213,574
Reportable Legal Entities [Member] | Parent Company [Member]
Cash flows from operating activities	(38,879)	21,183
Additions to properties, plants, and equipment
Other investing activities, net	23,116	(16,260)
Dividends paid to stockholders	(1,348)	(1,136)
Borrowings on debt	58,000
Payments on debt	(58,000)
Other financing activity	14,247	(1,186)
Effect of exchange rate changes on cash
Changes in cash, cash equivalents and restricted cash and cash equivalents	(2,864)	33,625
Cash, cash equivalents and restricted cash and cash equivalents at beginning of period	6,265	103,878
Cash, cash equivalents and restricted cash and cash equivalents at end of period	3,401	137,503
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Cash flows from operating activities	36,481	18,747
Additions to properties, plants, and equipment	(25,401)	(8,082)
Other investing activities, net	(1)	151
Dividends paid to stockholders
Borrowings on debt
Payments on debt	(746)	(644)
Other financing activity	(15,725)	(20,118)
Effect of exchange rate changes on cash
Changes in cash, cash equivalents and restricted cash and cash equivalents	(5,392)	(9,946)
Cash, cash equivalents and restricted cash and cash equivalents at beginning of period	9,686	32,048
Cash, cash equivalents and restricted cash and cash equivalents at end of period	4,294	22,102
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities	(17,553)	13,396
Additions to properties, plants, and equipment	(7,670)	(9,553)
Other investing activities, net	2
Dividends paid to stockholders
Borrowings on debt
Payments on debt	(515)	(678)
Other financing activity	18,305	(1,285)
Effect of exchange rate changes on cash	95	876
Changes in cash, cash equivalents and restricted cash and cash equivalents	(7,336)	2,756
Cash, cash equivalents and restricted cash and cash equivalents at beginning of period	12,463	51,213
Cash, cash equivalents and restricted cash and cash equivalents at end of period	5,127	53,969
Consolidation, Eliminations [Member]
Cash flows from operating activities	39,981	(36,943)
Additions to properties, plants, and equipment
Other investing activities, net	(23,116)	15,579
Dividends paid to stockholders
Borrowings on debt
Payments on debt
Other financing activity	(16,865)	21,364
Effect of exchange rate changes on cash
Changes in cash, cash equivalents and restricted cash and cash equivalents
Cash, cash equivalents and restricted cash and cash equivalents at beginning of period
Cash, cash equivalents and restricted cash and cash equivalents at end of period