Note 16 - Guarantor Subsidiaries - Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities	$ 225,328	$ 106,445	$ 83,124
Cash flows from investing activities:
Additions to properties, plants, and equipment	(164,788)	(137,443)	(122,537)
Purchase of other companies, net of cash acquired	(3,931)	(809)
Other investing activities, net	(29,946)	(1,163)	4,182
Cash flows from financing activities:
Dividends paid to stockholders	(4,419)	(4,291)	(4,099)
Payments on debt	(11,156)	(10,851)	(9,137)
Other financing activity	3,554	(2,001)	49,740
Effect of exchange rate changes on cash	(74)	(5,152)	(3,783)
Changes in cash and cash equivalents	14,568	(54,456)	(2,510)
Cash and cash equivalents at beginning of year	155,209	209,665	212,175
Cash and cash equivalents at end of year	169,777	155,209	209,665
Cash flows from operating activities	225,328	106,445	83,124
Consolidation, Eliminations [Member]
Cash flows from operating activities	(19,606)	(2,629)	(75,323)
Cash flows from investing activities:
Additions to properties, plants, and equipment
Purchase of other companies, net of cash acquired
Other investing activities, net
Cash flows from financing activities:
Dividends paid to stockholders
Payments on debt
Other financing activity	19,606	2,629	75,323
Effect of exchange rate changes on cash
Changes in cash and cash equivalents
Cash and cash equivalents at beginning of year
Cash and cash equivalents at end of year
Cash flows from operating activities	(19,606)	(2,629)	(75,323)
Parent Company [Member] | Reportable Legal Entities [Member]
Cash flows from operating activities	85,665	(56,036)	38,270
Cash flows from investing activities:
Additions to properties, plants, and equipment	(348)	(1,355)	(1,336)
Purchase of other companies, net of cash acquired	(3,931)
Other investing activities, net	(29,383)	(748)
Cash flows from financing activities:
Dividends paid to stockholders	(4,419)	(4,291)	(4,099)
Payments on debt
Other financing activity	(28,476)	9,712	(12,221)
Effect of exchange rate changes on cash
Changes in cash and cash equivalents	19,108	(52,718)	20,614
Cash and cash equivalents at beginning of year	94,167	146,885	126,271
Cash and cash equivalents at end of year	113,275	94,167	146,885
Cash flows from operating activities	85,665	(56,036)	38,270
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Cash flows from operating activities	82,778	101,254	61,900
Cash flows from investing activities:
Additions to properties, plants, and equipment	(93,541)	(97,684)	(68,859)
Purchase of other companies, net of cash acquired
Other investing activities, net	(896)	637	417
Cash flows from financing activities:
Dividends paid to stockholders
Payments on debt	(10,174)	(12,405)	(9,137)
Other financing activity	3,529	17,066	9,494
Effect of exchange rate changes on cash
Changes in cash and cash equivalents	(18,304)	8,868	(6,185)
Cash and cash equivalents at beginning of year	42,692	33,824	40,009
Cash and cash equivalents at end of year	24,388	42,692	33,824
Cash flows from operating activities	82,778	101,254	61,900
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Cash flows from operating activities	76,491	63,856	58,277
Cash flows from investing activities:
Additions to properties, plants, and equipment	(70,899)	(38,404)	(52,342)
Purchase of other companies, net of cash acquired
Other investing activities, net	333	(1,052)	3,765
Cash flows from financing activities:
Dividends paid to stockholders
Payments on debt	(982)	1,554
Other financing activity	8,895	(31,408)	(22,856)
Effect of exchange rate changes on cash	(74)	(5,152)	(3,783)
Changes in cash and cash equivalents	13,764	(10,606)	(16,939)
Cash and cash equivalents at beginning of year	18,350	28,956	45,895
Cash and cash equivalents at end of year	32,114	18,350	28,956
Cash flows from operating activities	$ 76,491	$ 63,856	$ 58,277