Supplemental Guarantor Information Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 192,032	$ 118,312
Receivables	19,069	53,415
Ore on leach pads	73,752	64,167
Inventory, Net	58,230	93,436
Prepaid expenses and other	15,053	10,015
Disposal Group, Including Discontinued Operation, Assets, Current	91,421	71,442
Current assets	449,557	410,787
Property, plant and equipment, net	254,737	193,423
Mining properties, net	829,569	550,290
Ore on leach pads	65,393	67,231
Restricted assets	20,847	17,597
Equity and debt securities	34,837	4,488
Receivables	28,750	13,745
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other Assets, Noncurrent	17,485	12,585
Disposal Group, Including Discontinued Operation, Assets, Noncurrent	0	48,763
TOTAL ASSETS	1,701,175	1,318,909
Accounts payable	48,592	44,660
Accrued liabilities and other	94,930	36,445
Debt	30,753	11,955
Royalty obligations	0	4,995
Reclamation	3,777	3,109
Disposal Group, Including Discontinued Operation, Liabilities, Current	50,677	15,470
Liabilities, Current	228,729	116,634
Debt	380,569	198,682
Royalty obligations	0	4,292
Reclamation	117,055	85,592
Deferred tax liabilities	105,148	69,811
Other long-term liabilities	54,697	41,654
Intercompany Payable Receivable	0	0
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent	0	33,757
Non-current liabilities	657,469	433,788
Common stock, par value $0.01 per share; authorized 300,000,000 shares, issued and outstanding 185,637,724 at December 31, 2017 and 180,933,287 at December 31, 2016	1,856	1,809
Additional paid-in capital	3,357,345	3,314,590
Accumulated deficit	(2,546,743)	(2,545,424)
Accumulated other comprehensive income (loss)	2,519	(2,488)
Stockholders' equity	814,977	768,487	$ 421,476	$ 554,328
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	1,701,175	1,318,909
Accrued Income Taxes, Current	25,788	3,721
Interest Payable, Current	1,513	5,892
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	44,662	58,048
Receivables	137	12
Ore on leach pads	0	0
Inventory, Net	0	0
Prepaid expenses and other	7,824	3,803
Disposal Group, Including Discontinued Operation, Assets, Current	0	0
Current assets	52,623	61,863
Property, plant and equipment, net	4,007	3,222
Mining properties, net	0	0
Ore on leach pads	0	0
Restricted assets	13,251	10,170
Equity and debt securities	33,569	0
Receivables	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	422,074	273,056
Other Assets, Noncurrent	320,335	221,381
Disposal Group, Including Discontinued Operation, Assets, Noncurrent		0
TOTAL ASSETS	845,859	569,692
Accounts payable	3,607	2,153
Accrued liabilities and other	13,205	12,881
Debt	0	0
Royalty obligations	0	0
Reclamation	0	0
Disposal Group, Including Discontinued Operation, Liabilities, Current	0	0
Liabilities, Current	16,812	15,034
Debt	345,088	175,991
Royalty obligations		0
Reclamation	0	0
Deferred tax liabilities	4,110	13,810
Other long-term liabilities	2,311	1,993
Intercompany Payable Receivable	(337,439)	(405,623)
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent		0
Non-current liabilities	14,070	(213,829)
Common stock, par value $0.01 per share; authorized 300,000,000 shares, issued and outstanding 185,637,724 at December 31, 2017 and 180,933,287 at December 31, 2016	1,856	1,809
Additional paid-in capital	3,357,345	3,314,590
Accumulated deficit	(2,546,743)	(2,545,424)
Accumulated other comprehensive income (loss)	2,519	(2,488)
Stockholders' equity	814,977	768,487
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	845,859	569,692
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	52,239	50,023
Receivables	7,922	6,865
Ore on leach pads	73,752	64,167
Inventory, Net	29,769	49,393
Prepaid expenses and other	2,816	1,459
Disposal Group, Including Discontinued Operation, Assets, Current	0	0
Current assets	166,498	171,907
Property, plant and equipment, net	161,487	139,885
Mining properties, net	216,281	195,791
Ore on leach pads	65,393	67,231
Restricted assets	227	226
Equity and debt securities	1,268	4,488
Receivables	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	223	11,650
Other Assets, Noncurrent	11,040	9,263
Disposal Group, Including Discontinued Operation, Assets, Noncurrent		0
TOTAL ASSETS	622,417	600,441
Accounts payable	24,534	24,921
Accrued liabilities and other	19,262	13,664
Debt	9,215	6,516
Royalty obligations	0	4,995
Reclamation	2,313	2,672
Disposal Group, Including Discontinued Operation, Liabilities, Current	0	0
Liabilities, Current	55,324	52,768
Debt	28,313	15,214
Royalty obligations		4,292
Reclamation	82,021	75,183
Deferred tax liabilities	5,127	6,179
Other long-term liabilities	3,063	4,750
Intercompany Payable Receivable	317,759	336,813
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent		0
Non-current liabilities	436,283	442,431
Common stock, par value $0.01 per share; authorized 300,000,000 shares, issued and outstanding 185,637,724 at December 31, 2017 and 180,933,287 at December 31, 2016	19,630	250
Additional paid-in capital	149,194	181,009
Accumulated deficit	(34,551)	(73,529)
Accumulated other comprehensive income (loss)	(3,463)	(2,488)
Stockholders' equity	130,810	105,242
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	622,417	600,441
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	95,131	10,241
Receivables	11,010	46,538
Ore on leach pads	0	0
Inventory, Net	28,461	44,043
Prepaid expenses and other	4,413	4,753
Disposal Group, Including Discontinued Operation, Assets, Current	91,421	71,442
Current assets	230,436	177,017
Property, plant and equipment, net	89,243	50,316
Mining properties, net	613,288	354,499
Ore on leach pads	0	0
Restricted assets	7,369	7,201
Equity and debt securities	0	0
Receivables	28,750	13,745
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(18)	0
Other Assets, Noncurrent	2,854	3,500
Disposal Group, Including Discontinued Operation, Assets, Noncurrent		48,763
TOTAL ASSETS	971,922	655,041
Accounts payable	20,451	17,586
Accrued liabilities and other	62,463	9,900
Debt	21,538	5,439
Royalty obligations	0	0
Reclamation	1,464	437
Disposal Group, Including Discontinued Operation, Liabilities, Current	50,677	15,470
Liabilities, Current	156,593	48,832
Debt	323,912	229,036
Royalty obligations		0
Reclamation	35,034	10,409
Deferred tax liabilities	95,911	49,822
Other long-term liabilities	49,323	34,911
Intercompany Payable Receivable	19,680	68,810
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent		33,757
Non-current liabilities	523,860	426,745
Common stock, par value $0.01 per share; authorized 300,000,000 shares, issued and outstanding 185,637,724 at December 31, 2017 and 180,933,287 at December 31, 2016	195,020	197,913
Additional paid-in capital	1,885,046	1,864,261
Accumulated deficit	(1,788,597)	(1,882,710)
Accumulated other comprehensive income (loss)	0	0
Stockholders' equity	291,469	179,464
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	971,922	655,041
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	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	(422,279)	(284,706)
Other Assets, Noncurrent	(316,744)	(221,559)
Disposal Group, Including Discontinued Operation, Assets, Noncurrent		0
TOTAL ASSETS	(739,023)	(506,265)
Accounts payable	0	0
Accrued liabilities and other	0	0
Debt	0	0
Royalty obligations	0	0
Reclamation	0	0
Disposal Group, Including Discontinued Operation, Liabilities, Current	0	0
Liabilities, Current	0	0
Debt	(316,744)	(221,559)
Royalty obligations		0
Reclamation	0	0
Deferred tax liabilities	0	0
Other long-term liabilities	0	0
Intercompany Payable Receivable	0	0
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent		0
Non-current liabilities	(316,744)	(221,559)
Common stock, par value $0.01 per share; authorized 300,000,000 shares, issued and outstanding 185,637,724 at December 31, 2017 and 180,933,287 at December 31, 2016	(214,650)	(198,163)
Additional paid-in capital	(2,034,240)	(2,045,270)
Accumulated deficit	1,823,148	1,956,239
Accumulated other comprehensive income (loss)	3,463	2,488
Stockholders' equity	(422,279)	(284,706)
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ (739,023)	$ (506,265)