Note 13 - Guarantor Subsidiaries (Details) - Condensed Consolidating Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Assets
Cash and cash equivalents	$ 222,360	$ 212,175	$ 237,836	$ 190,984
Other current assets	7,516	8,324
Properties, plants, and equipment - net	1,829,500	1,791,601
Other non-current assets	3,440	5,867
Total assets	2,252,453	2,232,119
Liabilities and Shareholders' Equity
Current liabilities	101,042	151,479
Long-term debt	498,183	490,726
Non-current deferred tax liability	156,712	164,861
Other non-current liabilities	42,466	37,536
Stockholders' equity	1,386,367	1,326,419
Total liabilities and stockholders' equity	2,252,453	2,232,119
Consolidation, Eliminations [Member]
Assets
Other current assets	12,109	18,453
Intercompany receivable (payable)	50,059	49,159
Investments in subsidiaries	(1,275,038)	(1,195,076)
Other non-current assets	(87,853)	(84,044)
Total assets	(1,300,723)	(1,211,508)
Liabilities and Shareholders' Equity
Current liabilities	(11,785)
Non-current deferred tax liability	(13,900)	(16,430)
Stockholders' equity	(1,275,038)	(1,195,078)
Total liabilities and stockholders' equity	(1,300,723)	(1,211,508)
Consolidated [Member]
Assets
Cash and cash equivalents	222,360	212,175
Other current assets	96,079	131,460
Properties, plants, and equipment - net	1,829,500	1,791,601
Other non-current assets	104,514	96,883
Total assets	2,252,453	2,232,119
Liabilities and Shareholders' Equity
Current liabilities	101,042	151,479
Long-term debt	509,073	505,058
Non-current portion of accrued reclamation	56,793	46,766
Non-current deferred tax liability	156,712	164,861
Other non-current liabilities	42,466	37,536
Stockholders' equity	1,386,367	1,326,419
Total liabilities and stockholders' equity	2,252,453	2,232,119
Parent Company [Member]
Assets
Cash and cash equivalents	151,739	126,271	116,255	132,266
Other current assets	3,032	4,795
Properties, plants, and equipment - net	1,446	803
Intercompany receivable (payable)	510,942	528,290
Investments in subsidiaries	1,275,038	1,195,076
Other non-current assets	2,726	5,249
Total assets	1,944,923	1,860,484
Liabilities and Shareholders' Equity
Current liabilities	26,620	10,058
Long-term debt	498,183	490,726
Other non-current liabilities	33,753	33,281
Stockholders' equity	1,386,367	1,326,419
Total liabilities and stockholders' equity	1,944,923	1,860,484
Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	48,205	40,009	29,864	57,970
Other current assets	55,060	75,083
Properties, plants, and equipment - net	1,076,560	1,052,102
Intercompany receivable (payable)	(116,857)	(112,815)
Other non-current assets	183,249	164,563
Total assets	1,246,217	1,218,942
Liabilities and Shareholders' Equity
Current liabilities	63,603	117,421
Long-term debt	10,864	14,292
Non-current portion of accrued reclamation	48,224	38,426
Non-current deferred tax liability	13,100	16,430
Other non-current liabilities	9,764	4,043
Stockholders' equity	1,100,662	1,028,330
Total liabilities and stockholders' equity	1,246,217	1,218,942
Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	22,416	45,895	91,717	748
Other current assets	25,878	33,129
Properties, plants, and equipment - net	751,494	738,696
Intercompany receivable (payable)	(444,144)	(464,634)
Other non-current assets	6,392	11,115
Total assets	362,036	364,201
Liabilities and Shareholders' Equity
Current liabilities	22,604	24,000
Long-term debt	26	40
Non-current portion of accrued reclamation	8,569	8,340
Non-current deferred tax liability	157,512	164,861
Other non-current liabilities	(1,051)	212
Stockholders' equity	174,376	166,748
Total liabilities and stockholders' equity	$ 362,036	$ 364,201