Supplemental Guarantor Information Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 159,643	$ 192,032
Receivables	35,864	19,069
Ore on leach pads	75,584	73,752
Inventory, Net	61,723	58,230
Prepaid expenses and other	18,203	15,053
Disposal Group, Including Discontinued Operation, Assets, Current	0	91,421
Current assets	351,017	449,557
Property, plant and equipment, net	266,157	254,737
Mining properties, net	843,821	829,569
Ore on leach pads	67,430	65,393
Restricted assets	22,116	20,847
Equity and debt securities	37,317	34,837
Receivables	55,428	28,750
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other Assets, Noncurrent	18,649	17,485
TOTAL ASSETS	1,661,935	1,701,175
Accounts payable	44,864	48,592
Accrued liabilities and other	105,149	94,930
Debt	17,040	30,753
Reclamation	3,777	3,777
Disposal Group, Including Discontinued Operation, Liabilities, Current	0	50,677
Liabilities, Current	170,830	228,729
Debt	396,984	380,569
Reclamation	119,154	117,055
Deferred tax liabilities	105,224	105,148
Other long-term liabilities	55,432	54,697
Intercompany Payable Receivable	0	0
Non-current liabilities	676,794	657,469
Common stock, par value $0.01 per share; authorized 300,000,000 shares, 186,176,237 issued and outstanding at March 31, 2018 and 185,637,724 at December 31, 2017	1,862	1,856
Additional paid-in capital	3,355,710	3,357,345
Accumulated deficit	(2,542,898)	(2,546,743)
Accumulated other comprehensive income (loss)	(363)	2,519
Stockholders' equity	814,311	814,977
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	1,661,935	1,701,175
Accrued Income Taxes, Current	36,642	25,788
Interest Payable, Current	5,594	1,513
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	22,111	44,662
Receivables	15,895	137
Ore on leach pads	0	0
Inventory, Net	0	0
Prepaid expenses and other	8,892	7,824
Disposal Group, Including Discontinued Operation, Assets, Current		0
Current assets	46,898	52,623
Property, plant and equipment, net	3,141	4,007
Mining properties, net	6,980	0
Ore on leach pads	0	0
Restricted assets	14,352	13,251
Equity and debt securities	36,772	33,569
Receivables	24,047	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	423,448	422,074
Other Assets, Noncurrent	317,146	320,335
TOTAL ASSETS	872,784	845,859
Accounts payable	3,419	3,607
Accrued liabilities and other	16,643	13,205
Debt	0	0
Reclamation	0	0
Disposal Group, Including Discontinued Operation, Liabilities, Current		0
Liabilities, Current	20,062	16,812
Debt	360,280	345,088
Reclamation	0	0
Deferred tax liabilities	2,641	4,110
Other long-term liabilities	2,602	2,311
Intercompany Payable Receivable	(327,111)	(337,439)
Non-current liabilities	38,412	14,070
Common stock, par value $0.01 per share; authorized 300,000,000 shares, 186,176,237 issued and outstanding at March 31, 2018 and 185,637,724 at December 31, 2017	1,862	1,856
Additional paid-in capital	3,355,710	3,357,345
Accumulated deficit	(2,542,899)	(2,546,743)
Accumulated other comprehensive income (loss)	(363)	2,519
Stockholders' equity	814,310	814,977
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	872,784	845,859
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	30,603	52,239
Receivables	5,084	7,922
Ore on leach pads	75,584	73,752
Inventory, Net	31,512	29,769
Prepaid expenses and other	3,193	2,816
Disposal Group, Including Discontinued Operation, Assets, Current		0
Current assets	145,976	166,498
Property, plant and equipment, net	165,578	161,487
Mining properties, net	219,000	216,281
Ore on leach pads	67,430	65,393
Restricted assets	227	227
Equity and debt securities	545	1,268
Receivables	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	332	223
Other Assets, Noncurrent	11,820	11,040
TOTAL ASSETS	610,908	622,417
Accounts payable	21,634	24,534
Accrued liabilities and other	12,059	19,262
Debt	9,977	9,215
Reclamation	2,313	2,313
Disposal Group, Including Discontinued Operation, Liabilities, Current		0
Liabilities, Current	45,983	55,324
Debt	31,116	28,313
Reclamation	83,392	82,021
Deferred tax liabilities	4,978	5,127
Other long-term liabilities	2,751	3,063
Intercompany Payable Receivable	307,016	317,759
Non-current liabilities	429,253	436,283
Common stock, par value $0.01 per share; authorized 300,000,000 shares, 186,176,237 issued and outstanding at March 31, 2018 and 185,637,724 at December 31, 2017	19,630	19,630
Additional paid-in capital	145,024	149,194
Accumulated deficit	(28,982)	(34,551)
Accumulated other comprehensive income (loss)	0	(3,463)
Stockholders' equity	135,672	130,810
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	610,908	622,417
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	106,929	95,131
Receivables	14,885	11,010
Ore on leach pads	0	0
Inventory, Net	30,211	28,461
Prepaid expenses and other	6,118	4,413
Disposal Group, Including Discontinued Operation, Assets, Current		91,421
Current assets	158,143	230,436
Property, plant and equipment, net	97,438	89,243
Mining properties, net	617,841	613,288
Ore on leach pads	0	0
Restricted assets	7,537	7,369
Equity and debt securities	0	0
Receivables	31,381	28,750
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	694	(18)
Other Assets, Noncurrent	3,431	2,854
TOTAL ASSETS	916,465	971,922
Accounts payable	19,811	20,451
Accrued liabilities and other	76,447	62,463
Debt	7,063	21,538
Reclamation	1,464	1,464
Disposal Group, Including Discontinued Operation, Liabilities, Current		50,677
Liabilities, Current	104,785	156,593
Debt	319,336	323,912
Reclamation	35,762	35,034
Deferred tax liabilities	97,605	95,911
Other long-term liabilities	50,079	49,323
Intercompany Payable Receivable	20,095	19,680
Non-current liabilities	522,877	523,860
Common stock, par value $0.01 per share; authorized 300,000,000 shares, 186,176,237 issued and outstanding at March 31, 2018 and 185,637,724 at December 31, 2017	195,020	195,020
Additional paid-in capital	1,882,610	1,885,046
Accumulated deficit	(1,788,827)	(1,788,597)
Accumulated other comprehensive income (loss)	0	0
Stockholders' equity	288,803	291,469
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	916,465	971,922
Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0
Receivables	0	0
Ore on leach pads	0	0
Inventory, Net	0	0
Prepaid expenses and other	0	0
Disposal Group, Including Discontinued Operation, Assets, Current		0
Current assets	0	0
Property, plant and equipment, net	0	0
Mining properties, net	0	0
Ore on leach pads	0	0
Restricted assets	0	0
Equity and debt securities	0	0
Receivables	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(424,474)	(422,279)
Other Assets, Noncurrent	(313,748)	(316,744)
TOTAL ASSETS	(738,222)	(739,023)
Accounts payable	0	0
Accrued liabilities and other	0	0
Debt	0	0
Reclamation	0	0
Disposal Group, Including Discontinued Operation, Liabilities, Current		0
Liabilities, Current	0	0
Debt	(313,748)	(316,744)
Reclamation	0	0
Deferred tax liabilities	0	0
Other long-term liabilities	0	0
Intercompany Payable Receivable	0	0
Non-current liabilities	(313,748)	(316,744)
Common stock, par value $0.01 per share; authorized 300,000,000 shares, 186,176,237 issued and outstanding at March 31, 2018 and 185,637,724 at December 31, 2017	(214,650)	(214,650)
Additional paid-in capital	(2,027,634)	(2,034,240)
Accumulated deficit	1,817,810	1,823,148
Accumulated other comprehensive income (loss)	0	3,463
Stockholders' equity	(424,474)	(422,279)
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ (738,222)	$ (739,023)