Note 13 - Guarantor Subsidiaries - Unaudited Interim Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities	$ 45,821	$ 86,138
Additions to properties, plants, and equipment	(45,964)	(76,960)
Other investing activities, net	(7,680)	(18,831)
Dividends paid to stockholders	(2,257)	(2,190)
Payments on debt	(3,715)	(5,695)
Other financing activity	7,045	4,654
Effect of exchange rate changes on cash	1,086	1,288
Changes in cash and cash equivalents	(5,664)	(11,596)
Cash and cash equivalents at beginning of period	169,777	155,209
Cash and cash equivalents at end of period	164,113	143,613
Consolidation, Eliminations [Member]
Cash flows from operating activities	12,141	31,772
Additions to properties, plants, and equipment
Other investing activities, net	(424)
Dividends paid to stockholders
Payments on debt
Other financing activity	(11,717)	(31,772)
Effect of exchange rate changes on cash
Changes in cash and cash equivalents
Cash and cash equivalents at beginning of period
Cash and cash equivalents at end of period
Parent Company [Member] | Reportable Legal Entities [Member]
Cash flows from operating activities	9,131	22,190
Additions to properties, plants, and equipment		(40)
Other investing activities, net	(8,500)	(15,248)
Dividends paid to stockholders	(2,257)	(2,190)
Payments on debt		(1,339)
Other financing activity	(11,169)	4,948
Effect of exchange rate changes on cash
Changes in cash and cash equivalents	(12,795)	8,321
Cash and cash equivalents at beginning of period	113,275	94,167
Cash and cash equivalents at end of period	100,480	102,488
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Cash flows from operating activities	13,792	(8,639)
Additions to properties, plants, and equipment	(19,132)	(43,677)
Other investing activities, net	1,266	317
Dividends paid to stockholders
Payments on debt	(3,044)	(3,836)
Other financing activity	9,501	36,863
Effect of exchange rate changes on cash
Changes in cash and cash equivalents	2,383	(18,972)
Cash and cash equivalents at beginning of period	24,387	42,692
Cash and cash equivalents at end of period	26,770	23,720
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Cash flows from operating activities	10,757	40,815
Additions to properties, plants, and equipment	(26,832)	(33,243)
Other investing activities, net	(22)	(3,900)
Dividends paid to stockholders
Payments on debt	(671)	(520)
Other financing activity	20,430	(5,385)
Effect of exchange rate changes on cash	1,086	1,288
Changes in cash and cash equivalents	4,748	(945)
Cash and cash equivalents at beginning of period	32,115	18,350
Cash and cash equivalents at end of period	$ 36,863	$ 17,405