Note 13 - Guarantor Subsidiaries (Details) - Condensed Consolidating Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Assets
Cash and cash equivalents	$ 222,083	$ 212,175	$ 296,375	$ 190,984
Other current assets	5,934	8,324
Properties, plants, and equipment - net	1,818,632	1,791,601
Other non-current assets	3,577	5,867
Total assets	2,255,127	2,232,119
Liabilities and Stockholders' Equity
Current liabilities	147,046	151,479
Long-term debt	496,354	490,726
Non-current deferred tax liability	165,442	164,861
Other non-current liabilities	35,873	37,536
Stockholders' equity	1,341,383	1,326,419
Total liabilities and stockholders' equity	2,255,127	2,232,119
Consolidation, Eliminations [Member]
Assets
Other current assets	1,907	18,453
Intercompany receivable (payable)	(12,746)	49,159
Investments in subsidiaries	(1,243,429)	(1,195,076)
Other non-current assets	(87,612)	(84,044)
Total assets	(1,341,880)	(1,211,508)
Liabilities and Stockholders' Equity
Current liabilities	(15,155)
Non-current deferred tax liability	(83,296)	(16,430)
Stockholders' equity	(1,243,429)	(1,195,078)
Total liabilities and stockholders' equity	(1,341,880)	(1,211,508)
Consolidated [Member]
Assets
Cash and cash equivalents	222,083	212,175
Other current assets	124,797	131,460
Properties, plants, and equipment - net	1,818,632	1,791,601
Other non-current assets	89,615	96,883
Total assets	2,255,127	2,232,119
Liabilities and Stockholders' Equity
Current liabilities	147,046	151,479
Long-term debt	508,415	505,058
Non-current portion of accrued reclamation	56,968	46,766
Non-current deferred tax liability	165,442	164,861
Other non-current liabilities	35,873	37,536
Stockholders' equity	1,341,383	1,326,419
Total liabilities and stockholders' equity	2,255,127	2,232,119
Parent Company [Member]
Assets
Cash and cash equivalents	160,374	126,271
Other current assets	2,911	4,795
Properties, plants, and equipment - net	1,280	803
Intercompany receivable (payable)	475,113	528,290
Investments in subsidiaries	1,243,429	1,195,076
Other non-current assets	9,744	5,249
Total assets	1,892,851	1,860,484
Liabilities and Stockholders' Equity
Current liabilities	22,502	10,058
Long-term debt	496,354	490,726
Other non-current liabilities	32,612	33,281
Stockholders' equity	1,341,383	1,326,419
Total liabilities and stockholders' equity	1,892,851	1,860,484
Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	38,639	40,009
Other current assets	84,491	75,083
Properties, plants, and equipment - net	1,070,673	1,052,102
Intercompany receivable (payable)	(75,243)	(112,815)
Other non-current assets	160,560	164,563
Total assets	1,279,120	1,218,942
Liabilities and Stockholders' Equity
Current liabilities	117,510	117,421
Long-term debt	12,030	14,292
Non-current portion of accrued reclamation	48,169	38,426
Non-current deferred tax liability	11,901	16,430
Other non-current liabilities	4,386	4,043
Stockholders' equity	1,085,124	1,028,330
Total liabilities and stockholders' equity	1,279,120	1,218,942
Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	23,070	45,895
Other current assets	35,488	33,129
Properties, plants, and equipment - net	746,679	738,696
Intercompany receivable (payable)	(387,124)	(464,634)
Other non-current assets	6,923	11,115
Total assets	425,036	364,201
Liabilities and Stockholders' Equity
Current liabilities	22,189	24,000
Long-term debt	31	40
Non-current portion of accrued reclamation	8,799	8,340
Non-current deferred tax liability	236,837	164,861
Other non-current liabilities	(1,125)	212
Stockholders' equity	158,305	166,748
Total liabilities and stockholders' equity	$ 425,036	$ 364,201