Note 16 - Guarantor Subsidiaries (Details) - Condensed Consolidating Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Cash Flow Statements, Captions [Line Items]
Cash flows from operating activities	$ 83,124	$ 26,644	$ 69,016
Cash flows from investing activities:
Additions to properties, plants, and equipment	(122,537)	(150,736)	(113,096)
Acquisition of Aurizon Mines Ltd.		(321,117)
Cash flows from financing activities:
Borrowings on debt		490,000
Effect of exchange rates on cash	(3,783)	(4,905)
Changes in cash and cash equivalents	(2,510)	21,191	(75,479)
Cash and cash equivalents at beginning of year	212,175	190,984	266,463
Cash and cash equivalents at end of year	209,665	212,175	190,984
Consolidation, Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash flows from operating activities	(75,323)	38,791	(8,940)
Cash flows from investing activities:
Other investing activities			48,817
Cash flows from financing activities:
Other financing activity	75,323	(38,791)	(39,877)
Consolidated [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash flows from operating activities	83,124	26,644	69,016
Cash flows from investing activities:
Additions to properties, plants, and equipment	(122,537)	(150,736)	(113,096)
Acquisition of Aurizon Mines Ltd.		(321,117)
Other investing activities	4,182	(3,644)	(4,942)
Cash flows from financing activities:
Dividends paid to stockholders	(4,099)	(6,543)	(17,673)
Borrowings on debt		490,000
Payments on debt	(9,137)	(7,039)	(5,890)
Other financing activity	49,740	(1,469)	(2,894)
Effect of exchange rates on cash	(3,783)	(4,905)
Changes in cash and cash equivalents	(2,510)	21,191	(75,479)
Cash and cash equivalents at beginning of year	212,175	190,984	266,463
Cash and cash equivalents at end of year	209,665	212,175	190,984
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash flows from operating activities	38,270	(9,958)	49,295
Cash flows from investing activities:
Additions to properties, plants, and equipment	(1,336)	(1,535)	(618)
Acquisition of Aurizon Mines Ltd.		(498,705)
Other investing activities			(48,815)
Cash flows from financing activities:
Dividends paid to stockholders	(4,099)	(6,543)	(17,673)
Borrowings on debt		490,000
Other financing activity	(12,221)	20,746	52,227
Changes in cash and cash equivalents	20,614	(5,995)	34,416
Cash and cash equivalents at beginning of year	126,271	132,266	97,850
Cash and cash equivalents at end of year	146,885	126,271	132,266
Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash flows from operating activities	61,900	17,940	42,957
Cash flows from investing activities:
Additions to properties, plants, and equipment	(68,859)	(107,893)	(107,425)
Other investing activities	417	(11)	891
Cash flows from financing activities:
Payments on debt	(9,137)	(7,039)	(5,878)
Other financing activity	9,494	79,937	(41,903)
Changes in cash and cash equivalents	(6,185)	(17,066)	(111,358)
Cash and cash equivalents at beginning of year	40,009	57,075	168,433
Cash and cash equivalents at end of year	33,824	40,009	57,075
Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash flows from operating activities	58,277	(20,129)	(14,296)
Cash flows from investing activities:
Additions to properties, plants, and equipment	(52,342)	(41,308)	(5,053)
Acquisition of Aurizon Mines Ltd.		177,588
Other investing activities	3,765	(3,633)	(5,835)
Cash flows from financing activities:
Payments on debt			(12)
Other financing activity	(22,856)	(63,361)	26,659
Effect of exchange rates on cash	(3,783)	(4,905)
Changes in cash and cash equivalents	(16,939)	44,252	1,463
Cash and cash equivalents at beginning of year	45,895	1,643	180
Cash and cash equivalents at end of year	$ 28,956	$ 45,895	$ 1,643