Stillwater Mining (SWC) 10-Q 29 Jul 16 2016 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2016	Jul. 28, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q2
Entity Registrant Name	STILLWATER MINING CO /DE/
Entity Central Index Key	931,948
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		121,075,861

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
REVENUES
Mine Production	$ 106,395	$ 118,968	$ 192,197	$ 244,706
PGM Recycling	59,188	66,316	106,924	140,998
Other	100	100	200	200
Total revenues	165,683	185,384	299,321	385,904
Costs of metals sold
Mine Production	75,589	80,631	143,032	160,672
PGM Recycling	56,490	64,441	102,534	137,146
Total costs of metals sold (excludes depletion, depreciation and amortization)	132,079	145,072	245,566	297,818
Depletion, depreciation and amortization
Mine Production	20,517	16,942	37,586	33,811
PGM Recycling	194	256	385	508
Total depletion, depreciation and amortization	20,711	17,198	37,971	34,319
Total costs of revenues	152,790	162,270	283,537	332,137
Exploration	1,587	760	4,435	1,840
General and administrative	8,311	10,396	16,608	18,741
Gain on sale of long-term investment	(482)	0	(482)	0
(Gain) loss on long-term investments	0	(2)	0	53
Impairment of non-producing mineral properties	0	46,772	0	46,772
(Gain) loss on disposal of property, plant and equipment	(153)	0	(154)	3
Total costs and expenses	162,053	220,196	303,944	399,546
OPERATING INCOME (LOSS)	3,630	(34,812)	(4,623)	(13,642)
OTHER (EXPENSE) INCOME
Other	44	17	86	901
Interest income	960	724	1,670	1,426
Interest expense	(4,067)	(5,312)	(8,249)	(10,616)
Net foreign currency transaction gain	2	745	1,194	137
INCOME (LOSS) BEFORE INCOME TAX BENEFIT (PROVISION)	569	(38,638)	(9,922)	(21,794)
Income tax benefit (provision)	215	(380)	776	5,663
NET INCOME (LOSS)	784	(39,018)	(9,146)	(16,131)
Net loss attributable to noncontrolling interest	0	(11,542)	0	(11,657)
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS	784	(27,476)	(9,146)	(4,474)
Other comprehensive income, net of tax
Net unrealized gain on investments available-for-sale and deferred compensation	183	47	530	183
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS	967	(27,429)	(8,616)	(4,291)
Comprehensive loss attributable to noncontrolling interest	0	(11,542)	0	(11,657)
TOTAL COMPREHENSIVE INCOME (LOSS)	$ 967	$ (38,971)	$ (8,616)	$ (15,948)
Weighted average shares of common stock outstanding
Basic (in shares)	121,074	120,751	121,065	120,637
Diluted (in shares)	121,380	120,751	121,065	120,637
Basic income (loss) per share attributable to common stockholders (in usd per share)	$ 0.01	$ (0.23)	$ (0.08)	$ (0.04)
Diluted income (loss) per share attributable to common stockholders (in usd per share)	$ 0.01	$ (0.23)	$ (0.08)	$ (0.04)

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets
Cash and cash equivalents	$ 130,115	$ 147,336
Investments	312,037	316,429
Inventories	113,892	102,072
Trade receivables	890	800
Prepaid expenses	5,660	2,821
Other current assets	25,505	21,628
Total current assets	588,099	591,086
Mineral properties	112,480	112,480
Mine development, net	473,383	460,751
Property, plant and equipment, net	102,337	109,957
Other noncurrent assets	4,932	4,115
Total assets	1,281,231	1,278,389
Current liabilities
Accounts payable	22,304	18,205
Accrued compensation and benefits	28,195	30,046
Property, production and franchise taxes payable	13,617	13,907
Current portion of long-term debt and capital lease obligations	0	657
Income taxes payable	373	0
Other current liabilities	4,369	5,286
Total current liabilities	68,858	68,101
Long-term debt	264,301	255,099
Deferred income taxes	20,310	22,761
Accrued workers compensation	6,479	6,070
Asset retirement obligation	11,159	11,027
Other noncurrent liabilities	7,845	6,102
Total liabilities	378,952	369,160
Stockholders’ equity
Preferred stock, $0.01 par value, 1,000,000 shares authorized; none issued	0	0
Common stock, $0.01 par value, 200,000,000 shares authorized; 121,074,473 and 121,049,471 issued and outstanding at June 30, 2016 and December 31, 2015, respectively	1,211	1,210
Paid-in capital	1,100,949	1,099,283
Accumulated deficit	(200,213)	(191,067)
Accumulated other comprehensive income (loss)	332	(197)
Total stockholders’ equity	902,279	909,229
Total liabilities and equity	$ 1,281,231	$ 1,278,389

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value (in usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	121,074,473	121,049,471
Common stock, shares outstanding (in shares)	121,074,473	121,049,471

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (9,146)	$ (16,131)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depletion, depreciation and amortization	37,971	34,319
Gain on sale of long-term investment	(482)	0
Loss on long-term investments	0	53
Impairment of non-producing mineral properties	0	46,772
Amortization / accretion on investment premium / discount	1,218	975
(Gain) loss on disposal of property, plant and equipment	(154)	3
Net foreign currency transaction gain	(1,194)	(137)
Deferred income taxes	(1,526)	(12,592)
Accretion of asset retirement obligation	421	387
Amortization of deferred debt issuance costs	437	610
Accretion of convertible debenture debt discount	8,765	9,127
Share based compensation and other benefits	1,741	6,913
Non-cash capitalized interest	(2,728)	(1,784)
Changes in operating assets and liabilities:
Inventories	(12,435)	630
Trade receivables	(90)	48
Prepaid expenses	(2,839)	(3,285)
Accounts payable	2,121	(117)
Accrued compensation and benefits	(1,850)	(411)
Property, production and franchise taxes payable	1,454	(6)
Income taxes payable	373	0
Accrued workers compensation	409	(352)
Other operating assets	(4,605)	(3,516)
Other operating liabilities	(1,007)	(1,907)
NET CASH PROVIDED BY OPERATING ACTIVITIES	16,854	59,599
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(38,426)	(58,218)
Proceeds from sale of long-term investment	851	0
Proceeds from disposal of property, plant and equipment	154	0
Purchases of investments	(165,742)	(184,660)
Proceeds from maturities and sales of investments	169,745	126,849
NET CASH USED IN INVESTING ACTIVITIES	(33,418)	(116,029)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments on debt and capital lease obligations	(658)	(1,097)
Proceeds from issuance of common stock	1	49
NET CASH USED IN FINANCING ACTIVITIES	(657)	(1,048)
CASH AND CASH EQUIVALENTS
Net decrease	(17,221)	(57,478)
Balance at beginning of period	147,336	280,286
BALANCE AT END OF PERIOD	$ 130,115	$ 222,808

General

General	6 Months Ended
	Jun. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General	GENERAL In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments (consisting only of normal recurring adjustments) necessary to fairly present the financial position of Stillwater Mining Company (the “Company”) at June 30, 2016 , and the results of its operations for the three and six months ended June 30, 2016 and 2015, respectively and cash flows for the six months ended June 30, 2016 and 2015 , respectively. The results of operations for the first six months of 2016 are not necessarily indicative of the results to be expected for the 2016 year. The accompanying consolidated financial statements in this Quarterly Report on Form 10-Q should be read in conjunction with the consolidated financial statements and notes thereto included in the Company's 2015 Annual Report on Form 10-K filed with the Securities and Exchange Commission on February 22, 2016 (Form 10-K). All inter-company transactions and balances have been eliminated in consolidation. The preparation of the Company’s consolidated financial statements in conformity with United States generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the amounts reported in these consolidated financial statements and accompanying notes. The more significant areas requiring the use of management’s estimates relate to mineral reserves, reclamation and environmental obligations, valuation allowance for deferred tax assets, useful lives utilized for depreciation, amortization and accretion calculations, future cash flows from long-lived assets, and fair value of derivatives and other financial instruments. Actual results could differ from these estimates. On May 28, 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers , which requires an entity to recognize the amount of revenue it expects to be entitled to for the transfer of promised goods or services to customers. In August 2015, the FASB issued ASU 2015-14, Deferral of the Effective Date , which defers the effective date of ASU 2014-09 by one year to January 1, 2018. ASU 2014-09 will replace most existing revenue recognition guidance in GAAP. The standard permits the use of either the retrospective or cumulative effect transition method. The Company continues to evaluate the effect that ASU 2014-09 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early adoption is not permitted. On April 7, 2015, as part of its initiative to simplify and reduce complexity in financial statements, the FASB issued ASU 2015-03, Interest - Imputation, (Subtopic 835-30): Simplifying the Presentation of Debt Issuance. This ASU requires the debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the debt liability. Also, it requires retrospective application for all prior periods presented in the financial statements and a disclosure of the nature of and reason for the change in accounting principle, the transition method, a description of the prior-period information that has been retrospectively adjusted and the effect of the change on the financial statement line items. ASU 2015-03 is effective for financial statements issued for fiscal years beginning after December 31, 2015, and interim periods within those fiscal years. Early adoption was permitted for financial statements that had not been previously issued. The Company elected early adoption of ASU 2015-03 and reclassified Deferred debt issue costs against the related liability for all periods presented. Prior to the adoption of ASU 2015-03, the balance reported at December 31, 2015 for total Long-term debt and capital lease obligations was $258.9 million , and after adoption and reclassification of Deferred debt issue costs of $3.8 million , the total balance reported at December 31, 2015 became $255.1 million . On July 22, 2015, as part of its initiative to simplify and reduce complexity in financial statements, the FASB issued ASU 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory. ASU 2015-11, which will change the measurement principle for inventory from the lower of cost or market to the lower of cost and net realizable value. ASU 2015-11 is effective for financial statements issued for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. The Company is evaluating the effect that ASU 2015-11 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. The ASU requires prospective adoption and permits early adoption. On February 25, 2016, the FASB issued ASU 2016-02, Leases, (Topic 840) , which requires an entity that leases assets, with terms of more than 12 months, to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. ASU 2016-02 is effective for financial statements issued for fiscal years beginning after December 31, 2018, and interim periods within those fiscal years. The Company is evaluating the effect that ASU 2016-02 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early adoption is permitted. On March 30, 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employees Shared-Based Payment Accounting. The ASU will change several aspects within share based payments: (1) accounting for income taxes, (2) classification of excess tax benefits, (3) forfeitures, (4) minimum statutory tax withholding requirements, (5) classification of employee taxes paid when an employer withholds shares for tax-withholding purposes, (6) practical expedient - expected term, (7) intrinsic value, and (8) eliminating the indefinite deferral. ASU 2016-09 is effective for financial statements issued for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. The Company is evaluating the effect that ASU 2016-09 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early adoption is permitted in any interim or annual period provided that the entire ASU is adopted.

Sales

Sales	6 Months Ended
	Jun. 30, 2016
Sales Revenue, Goods, Net [Abstract]
Sales	SALES MINE PRODUCTION The Company mines and processes ores containing palladium, platinum, rhodium, gold, silver, copper and nickel into intermediate and final products for sale to customers. Palladium, platinum, rhodium, gold and silver are sent to a third-party refiner for final processing from which they are sold to customers with whom the Company has established trading relationships. Refined platinum group metals (PGMs) in sponge form are transferred upon sale from the Company’s account at the third-party refiner to the account of the purchaser. By-product metals are normally sold at market price to customers, brokers or outside refiners. Copper and nickel by-products are typically sold at a discount to the quoted market prices. By-product sales (gold, nickel, mined rhodium, copper and silver) are included in revenues from Mine Production. During each of the three months ended June 30, 2016 and 2015 , total by-product sales totaled $6.1 million and $6.9 million , respectively. For the six months ended June 30, 2016 and 2015 , by-product sales totaled $11.3 million and $13.7 million , respectively. In July 2014, the Company executed five -year supply and refining agreements with Johnson Matthey (JM). Under the terms of these agreements, JM has an exclusive five -year right to refine all of the PGM filter cake the Company produces at its Columbus, Montana facilities. JM also has the right to purchase all of the Company's mine production of palladium and platinum at competitive market prices (except for platinum sales under the Company's sales agreement with Tiffany & Co., which are specifically excluded from the JM agreements) and has the right to bid for any recycling volumes the Company has available. Other provisions of the agreements include a good-faith effort by JM to assist in growing the Company's recycling volumes and the sharing of market intelligence to the extent permitted by law. The Company has the right to exit the JM PGM supply arrangement in return for the payment of a nominal fee. In addition, the Company, in its sole discretion, may elect to terminate the refining arrangement after July 2018. In accordance with the terms of the JM PGM supply agreement, all Company sales of mined PGMs, other than the platinum sales under the Company's sales agreement with Tiffany & Co., were to JM for the six months ended June 30, 2016 and 2015. PGM RECYCLING The Company purchases spent catalyst materials from third-parties for recycling and processes these materials within its facilities in Columbus, Montana to recover palladium, platinum and rhodium for sale. The Company has entered into sourcing arrangements for catalyst materials with various suppliers. Under these sourcing arrangements the Company may advance cash as general working capital or against a shipment of material shortly before actually receiving the physical shipment at the Company's processing facilities. These advances are included in Other current assets on the Company’s Consolidated Balance Sheets until such time as the materials have been physically received and title has transferred to the Company, at which time the advance is reclassified into Inventories . Finance charges collected on advances and inventories prior to being earned are included in Other current liabilities on the Company’s Consolidated Balance Sheets . Finance charges are reclassified from Other current liabilities to Interest income ratably from the time the cash advance was made until the out-turn date of the inventory from the final refiner. The Company also accepts material supplied from third-parties on a tolling basis, processing it for a fee and returning the recovered metals to the supplier. TOTAL SALES Total sales to significant customers as a percentage of total revenues for the three and six months ended June 30, 2016 and 2015 were as follows: Three Months Ended Six Months Ended June 30, June 30, 2016 2015 (1) 2016 (1) 2015 (1) Customer A 72 % 80 % 76 % 77 % Customer B 10 % — — — (1) The “—” symbol represents less than 10% of total revenues.

Asset Impairment

Asset Impairment	6 Months Ended
	Jun. 30, 2016
Property, Plant and Equipment [Abstract]
Asset Impairment	ASSET IMPAIRMENT In accordance with the FASB Accounting Standards Codification 360, Property Plant and Equipment, (ASC 360-10), the Company reviews and evaluates its long-lived assets for impairment when events and changes in circumstances indicate that the related carrying amounts of such assets may not be recoverable and may exceed their fair value. For purposes of determining impairment, assets are grouped at the lowest level for which identifiable cash flows (including estimated future cash flows from non-operating properties) are largely independent of the cash flows of other groups of assets and liabilities. The Company determined there were no material events or circumstances requiring the Company to test long-lived assets for impairment at June 30, 2016. However, during the second quarter of 2015, the Company concluded that there was evidence to suggest that there had been a significant decrease in the fair value of the Marathon mineral properties. Accordingly, the Company performed an analysis that indicated the carrying value of the Marathon mineral properties exceeded its recoverable amount at June 30, 2015. The Company undertook an assessment of the fair value of its Marathon mineral properties, which included the examination of recent comparable transactions. At June 30, 2015, the Company recorded an impairment charge of $46.8 million (before-tax) against the carrying value of the Marathon mineral properties in Canada, reducing its carrying value to an estimated fair value of $8.6 million .

Noncontrolling Interest

Noncontrolling Interest	6 Months Ended
	Jun. 30, 2016
Noncontrolling Interest [Abstract]
Noncontrolling Interest	NONCONTROLLING INTEREST In the fourth quarter of 2015, the Company purchased a 25% interest held by Mitsubishi Corporation (Mitsubishi) in Stillwater Canada Inc (SCI), the Company's subsidiary, which holds the Marathon PGM-copper assets. The Company paid total cash consideration of $5.2 million which equaled $1.0 million in cash and 25% of the total cash and cash equivalents held by SCI. Prior to the repurchase, Mitsubishi's 25% interest in SCI's net loss for each period was shown as Net loss attributable to noncontrolling interest in the Company's Consolidated Statements of Comprehensive Income (Loss) . The amount of the loss was added back to the Company's reported Net (loss) income in each period in arriving at Net (loss) income attributable to common stockholders . The reported Net loss attributable to noncontrolling interest for the three and six months ended June 30, 2015 was $11.5 million and $11.7 million , respectively.

Derivative Instruments

Derivative Instruments	6 Months Ended
	Jun. 30, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS The Company uses various derivative financial instruments to manage its exposure to changes in PGM market commodity prices. COMMODITY DERIVATIVES PGM Recycling The Company customarily enters into fixed forward sales contracts relating to PGM recycling of catalyst and other industrial sourced materials. Under these fixed forward transactions, the Company agrees to deliver a stated quantity of metal on a specific future date at a price stipulated in advance. The Company uses fixed forward transactions to set in advance the pricing for metals acquired and processed in its recycling segment. The metals from PGM recycled materials are sold forward at the time of purchase and delivered against the fixed forward contracts when the ounces are recovered. Because this forward price is also used to set the acquisition price the Company pays for recycling materials, this arrangement significantly reduces exposure to PGM price volatility. The Company believes such transactions qualify for the exception to hedge accounting treatment and has elected to account for these transactions as normal purchases and normal sales. All of the Company's fixed forward sales contracts open at June 30, 2016 , will settle at various periods through December 2016 . The Company has credit agreements with its major trading partners that provide for margin deposits in the event that forward prices for metals exceed the Company’s hedged prices by a predetermined margin limit. At June 30, 2016 , and December 31, 2015 , no margin deposits were outstanding or due. The following is a summary of the Company's outstanding commodity derivatives in its Recycling Business Segment at June 30, 2016 : PGM Recycling: Fixed Forward Contracts Platinum Palladium Rhodium Settlement Period Ounces Average Price/Ounce Ounces Average Price/Ounce Ounces Average Price/Ounce Third Quarter 2016 34,034 $ 1,005 54,508 $ 571 7,344 $ 675 Fourth Quarter 2016 4,356 $ 993 4,587 $ 564 1,952 $ 652

Share Compensation Plans

Share Compensation Plans	6 Months Ended
	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share Compensation Plans	SHARE COMPENSATION PLANS EQUITY PLANS The Company sponsors equity plans (the Plans) that enable the Company to grant equity-based compensation to employees and non-employee directors. The Company currently issues restricted stock units as incentive compensation under the Plans. In total, approximately 11.6 million shares of common stock have been authorized for issuance under the Plans, including approximately 5.0 million , 5.2 million , and 1.4 million authorized shares under the 2012 Equity Incentive Plan, 2004 Equity Incentive Plan and the General Employee Plan, respectively. Approximately 4.1 million shares were available and reserved for issuance under the 2012 Equity Incentive Plan at June 30, 2016 . The Compensation Committee of the Company's Board of Directors administers the Plans and determines the type of equity awards to be issued, the exercise period, vesting period and all other terms of instruments issued under the Plans. NONVESTED SHARES Time-Based Restricted Stock Unit Awards Time-based restricted stock unit awards provide the participant with the right to receive a number of shares of the Company's common stock upon vesting of the awards provided the participant is employed by the Company on the vesting date. Time-based awards are valued using the Company's common stock price on the date of grant. Time-based awards are not entitled to any dividend equivalents with respect to the restricted stock units unless otherwise determined by the Board, nor any dividends on stock that may be delivered in settlement of the restricted stock units unless and until the stock is issued in settlement of the restricted stock units. Nonvested time-based share activity during the six months ended June 30, 2016 , is detailed in the following table: Nonvested Shares Weighted-Average Grant-Date Fair Value Nonvested time-based shares at January 1, 2016 186,655 $ 13.97 Granted 206,974 8.03 Vested (33,080 ) 13.88 Forfeited — — Nonvested time-based shares at March 31, 2016 360,549 $ 10.68 Granted 2,652 10.13 Vested (2,747 ) 14.24 Forfeited (565 ) 13.02 Nonvested time-based shares at June 30, 2016 359,889 $ 10.63 Total compensation expense, included within General and administrative in the Company's Consolidated Statements of Comprehensive Income (Loss) related to grants of time-based nonvested shares was $0.6 million and $0.4 million , in the three months ended June 30, 2016 and 2015 respectively, and $1.0 million and $0.8 million , respectively, for the six months ended June 30, 2016 and 2015 . Performance-Based Restricted Stock Unit Awards The Company grants performance-based restricted stock unit awards under its Long Term Incentive Plan (LTIP). The payout of the awards is dependent upon distinct components with separate sub-targets. The sub-targets are either market-based or performance-based and classified as either equity or liability. The market-based sub-targets are valued using a Monte Carlo simulation valuation model on the date of grant. The fair value of the liability-classified sub-targets are re-measured each reporting period. The existence of a market condition requires recognition of compensation cost for the performance restricted stock unit awards over the requisite period regardless of whether the market condition is satisfied. Total compensation expense, included within General and administrative in the Company's Consolidated Statements of Comprehensive Income (Loss) , related to grants of performance-based restricted stock unit awards for the three months ended June 30, 2016 and 2015 was $0.5 million and $0.4 million , respectively and $0.9 million and $0.6 million , respectively, for each of the six months ended June 30, 2016 and 2015 . A performance-based restricted stock unit award provides the participant with the right to receive a number of shares of the Company's common stock depending on achievement of specific measurable performance criteria. The number of shares earned is determined at the end of each performance period, generally three years , based on the actual performance criteria predetermined by the Compensation Committee at the time of grant. In the period when it becomes probable that the performance criteria will be achieved, the Company recognizes expense for the proportionate share of the total fair value of the grant related to the vesting period that has already lapsed. The remaining cost of the grant is expensed over the balance of the vesting period. For awards that contain performance-based conditions, and for which the Company determines it is no longer probable that it will achieve the minimum performance criteria specified in the Plan, the Company reverses all of the previously recognized compensation expense in the period when such a determination is made. Performance-based restricted stock unit awards are not entitled to any dividend equivalents with respect to the restricted stock units unless otherwise determined by the Board, nor any dividends on stock that may be delivered in settlement of the restricted stock units unless and until the stock is issued in settlement of the restricted stock units. Share activity under nonvested performance-based restricted stock unit awards activity during the first six months of 2016 is detailed in the following table: Nonvested Shares Weighted-Average Grant-Date Fair Value Nonvested performance-based shares at January 1, 2016 379,277 $ 15.34 Granted * 186,285 11.45 Vested — Forfeited — — Nonvested performance-based shares at March 31, 2016 565,562 $ 14.06 No activity — Nonvested performance-based shares at June 30, 2016 565,562 $ 14.06 * The number of performance-based shares granted is based on the target award amounts in the performance restricted stock unit award agreements. The following table presents the compensation expense of the nonvested shares outstanding at June 30, 2016 , to be recognized over the remaining vesting periods: (In thousands) Time-based shares Performance -based shares Remaining 2016 $ 1,106 $ 1,158 2017 1,203 1,611 2018 583 757 2019 3 — Total $ 2,895 $ 3,526

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The Company determines income taxes using the asset and liability method, which results in the recognition of deferred tax assets and liabilities. These assets and liabilities reflect the expected future tax consequences of temporary differences between the carrying amount and the tax basis of those assets and liabilities, as well as operating loss and tax credit carryforwards, using enacted tax rates in effect in the years in which the differences are expected to reverse. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Deferred tax assets and liabilities are recorded on a jurisdictional basis. In assessing the realizability of deferred tax assets, the Company considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company considers the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment. The Company has a valuation allowance in 2016 and 2015 to reflect the estimated amount of deferred tax assets which may not be realized, which principally relate to foreign and state net operating losses, capital losses, and certain tax credits. The benefit for income taxes for the three and six months ended June 30, 2016 is related to the carryback of the current year losses and the deferred tax benefits from certain foreign jurisdictions, offset by an increase in the provision for uncertain tax positions in the U.S. Changes in the Company’s net deferred tax assets and liabilities have been partially offset by a corresponding change in the valuation allowance. The Company recognized an income tax benefit for the three months ended June 30, 2016 of $0.2 million and an income tax provision of $0.4 million , for the three months ended June 30, 2015. The Company recognized an income tax benefit for the six months ended June 30, 2016 and 2015, of $0.8 million and $5.7 million , respectively. The current year losses, partially offset by the discrete charge of $3.4 million for an increase in the provision for uncertain tax positions, are primarily responsible for the tax benefit for the six months ended June 30, 2016 . The partial restructure of internal operations and the creation of a separate metal sales and trading subsidiary was responsible for $8.6 million of the total $9.7 million discrete income tax benefit recognized for the six months ended June 30, 2015. The Company’s policy is to recognize interest and penalties on unrecognized tax benefits in Income tax benefit (provision) in the Company's Consolidated Statements of Comprehensive Income (Loss) . The Company had uncertain benefits of $3.4 million at June 30, 2016 . Interest and penalties of $0.1 million have been accrued at June 30, 2016 . The Company anticipates there could be a change in uncertain tax positions during the next twelve months. The Company made income tax payments of $0.3 million and $11.1 million in the six months ended June 30, 2016 and 2015 , respectively. Tax years still open for examination by the taxing authorities are the years ended December 31, 2015, 2014, 2013, 2012 and 2011, although net operating loss and credit carryforwards from all years are subject to examination and adjustment for the three years following the year in which the carryforwards are utilized.

Debt and Capital Lease Obligati

Debt and Capital Lease Obligations	6 Months Ended
	Jun. 30, 2016
Debt Disclosure [Abstract]
Debt and Capital Lease Obligations	DEBT AND CAPITAL LEASE OBLIGATIONS 1.75% CONVERTIBLE DEBENTURES In October 2012, the Company issued $396.75 million aggregate principal amount of 1.75% senior unsecured convertible debentures due October 15, 2032 ( 1.75% debentures). Each $1,000 principal amount of these 1.75% debentures is initially convertible, under certain circumstances and during certain periods, into 60.4961 shares (subject to customary anti-dilution adjustments) of the Company's common stock, which represents an initial conversion price of $16.53 per share. The 1.75% debentures also include an embedded conversion enhancement feature that is equivalent to including each debenture with a warrant initially exercisable for 30.2481 shares at an exercise price of $16.53 per share (also subject to customary anti-dilution adjustments). The Company, at its election, may settle conversions of the 1.75% debentures in cash, shares of its common stock or any combination of cash and shares of its common stock. Holders have the right to redeem their 1.75% debentures at face value, plus accrued and unpaid interest, on October 15th, of each of 2019, 2024, 2029, and upon the occurrence of certain corporate events. The Company will have the right to call the 1.75% debentures at any time on or after October 20, 2019. The 1.75% debentures were bifurcated under GAAP into separate debt and equity components, and reflect an effective maturity (to the first optional redemption date) of seven years . The residual amount of $141.6 million recorded in equity is treated for accounting purposes as additional debt discount and accreted as an additional non-cash interest charge to earnings over the expected life. Debt and equity issuance costs totaling approximately $12.4 million were deducted from the gross proceeds of the offering of the 1.75% debentures, and the debt portion is being amortized ratably over seven years . In the third quarter of 2015, the Company repurchased $61.6 million of outstanding principal under the 1.75% debentures, paying cash of $59.4 million . The Company reduced the debt component by $50.7 million , which included a reduction of the debt discount by $10.9 million . The difference between the book value and the fair value (including $0.7 million of debt and equity issuance costs) of the debt component resulted in a $4.2 million loss. The 1.75% debentures have an effective interest rate of 8.50% and a stated interest rate of 1.75% , with interest paid semi-annually. The balance outstanding at June 30, 2016 was approximately $263.8 million , which is net of unamortized discount of $68.0 million and $3.4 million deferred debt issue costs. The balance outstanding at December 31, 2015 was $254.6 million , which was net of unamortized discount of $76.8 million and $3.8 million of deferred debt issue costs. 1.875% CONVERTIBLE DEBENTURES Holders of the remaining $0.5 million of outstanding 1.875% debentures may require the Company to redeem their 1.875% debentures at face value on March 15, 2018 or March 15, 2023, or at any time before March 15, 2028 upon the occurrence of certain events including a change in control. Effective March 22, 2013, the Company has the right at its discretion to redeem the remaining $0.5 million of outstanding 1.875% debentures for cash at any time prior to maturity. In the third quarter of 2015, the Company repurchased $1.7 million of the outstanding principal of the 1.875% debentures, paying cash of $1.6 million and recording a gain of approximately $0.1 million . The outstanding balance at June 30, 2016 and December 31, 2015 , of $0.5 million aggregate principal amount, is reported as a long-term debt obligation. ASSET-BACKED REVOLVING CREDIT FACILITY In December 2011, the Company signed a $100.0 million asset-backed revolving credit agreement incurring debt issuance costs of $1.1 million . In January 2012, the Company completed the syndication of this facility and simultaneously expanded its maximum line of credit to $125.0 million , incurring additional debt issuance costs of $0.2 million . The Company also paid an unused line fee on the committed but unutilized balance under the facility at a rate per annum of 0.375% or 0.5% , depending on utilization of the facility. The Company terminated this credit facility on December 31, 2015, incurring expenses and fees of approximately $0.2 million . The following table reflects the amortization of debt issuance costs, interest expense and cash payments on the Company's outstanding debt for the three and six months ended June 30, 2016 and 2015: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 1.75% Convertible Debentures Amortization of debt issuance costs $ 221 $ 239 $ 437 $ 475 Interest expense, net of capitalized interest $ 3,877 $ 5,013 $ 7,869 $ 10,013 Cash payments for interest $ 2,933 $ — $ 2,933 $ 3,472 1.875% Convertible Debentures Interest expense, net of capitalized interest $ 2 $ — $ — $ — Cash payments for interest $ — $ — $ 5 $ 21 Asset-Backed Revolving Credit Facility Amortization of debt issuance costs $ — $ 68 $ — $ 135 Fees $ — $ 335 $ — $ 586 The Company's total current and long-term debt balances at June 30, 2016 and December 31, 2015 were as follows: June 30, 2016 December 31, 2015 (In thousands) Current Long-Term Current Long-Term 1.75% Convertible Debentures Aggregate principal $ — $ 335,150 $ — $ 335,150 Debt discount — (67,989 ) — (76,754 ) Deferred debt issue costs — (3,384 ) — (3,821 ) Debt balance — 263,777 — 254,575 1.875% Convertible Debentures — 524 — 524 Capital lease obligation — — 580 — Small land purchase — — 77 — Total debt balances $ — $ 264,301 $ 657 $ 255,099 CAPITALIZED INTEREST The Company capitalizes interest incurred on its various debt instruments as a cost of specific and identified areas under development. For the three months ended June 30, 2016 and 2015 , the Company capitalized interest of $2.0 million and $1.4 million , respectively. For the six months ended June 30, 2016 and 2015 , the Company capitalized interest of $3.9 million and $2.7 million , respectively. Capitalized interest is recorded as a reduction to Interest expense in the Company's Consolidated Statements of Comprehensive Income (Loss) .

Mineral Properties and Mine Dev

Mineral Properties and Mine Development	6 Months Ended
	Jun. 30, 2016
Extractive Industries [Abstract]
Mineral Properties and Mine Development	MINERAL PROPERTIES AND MINE DEVELOPMENT Mineral properties and mine development reflected in the accompanying balance sheets consisted of the following: June 30, December 31, (In thousands) 2016 2015 Mineral Properties: Montana, United States of America Stillwater Mine $ 1,950 $ 1,950 Ontario, Canada Marathon properties 8,560 8,560 San Juan, Argentina Altar property 101,970 101,970 Mine Development: Montana, United States of America Stillwater Mine 735,009 697,781 East Boulder Mine 227,564 220,281 1,075,053 1,030,542 Accumulated depletion and amortization (489,190 ) (457,311 ) Total mineral properties and mine development, net $ 585,863 $ 573,231

Property, Plant and Equipment

Property, Plant and Equipment	6 Months Ended
	Jun. 30, 2016
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment reflected in the accompanying consolidated balance sheets consisted of the following: June 30, December 31, (In thousands) 2016 2015 Machinery and equipment $ 161,906 $ 161,292 Buildings and structural components 174,278 173,580 Land 11,740 11,740 Construction-in-progress: Stillwater Mine 2,094 2,615 East Boulder Mine 266 435 Marathon 148 148 Processing facilities and other 1,469 1,982 351,901 351,792 Accumulated depreciation (249,564 ) (241,835 ) Total property, plant, and equipment, net $ 102,337 $ 109,957 The Company's total capital outlay for mine development and property, plant and equipment for the six months ended June 30, 2016 and 2015 were as follows: June 30, (In thousands) 2016 2015 Stillwater Mine $ 38,867 $ 47,171 East Boulder Mine 7,286 9,953 Other 480 4,054 Total U.S. capital expenditures 46,633 61,178 Foreign capital expenditures — 46 Non-cash capitalized interest and depreciation (5,321 ) (4,397 ) Change in accounts payables for capital expenditures (2,886 ) 1,391 Cash capital spend for the period $ 38,426 $ 58,218

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2016
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION The Company operates five reportable business segments: Mine Production, PGM Recycling, Canadian Properties, South American Properties and All Other. These segments are managed separately based on fundamental differences in their operations and geographic separation. The Mine Production segment consists of two business components: the Stillwater Mine and the East Boulder Mine. The Mine Production segment is engaged in the development, extraction, processing and refining of PGMs. The Company has agreements in place to sell its PGMs from mine production. The financial results for the Stillwater Mine and the East Boulder Mine have been aggregated, as both have similar products, processes, customers, distribution methods and economic characteristics. The PGM Recycling segment is engaged in the recycling of spent catalyst materials to recover the PGMs contained in the materials. The Company purchases catalyst materials processed by the PGM Recycling segment from third-party suppliers for its own account and sells the recovered metals directly, and it also accepts catalyst materials from third-parties on a tolling basis, processing it for a fee and returning the recovered metals to the supplier. The Company allocates costs of the Company's smelting and base metal refining facilities to both the Mine Production segment and to the PGM Recycling segment for internal and segment reporting purposes because these facilities support the PGM extraction requirements of both business segments. The Canadian Properties segment consists of the Marathon mineral property assets. The exploration-stage Marathon mineral properties include a large PGM and copper deposit located near the town of Marathon, Ontario, Canada as well as additional mineral properties located adjacent to the Marathon properties. The South American Properties segment consists of the Peregrine Metals Ltd. assets. The principal Peregrine property is the Altar property, an exploration-stage copper-gold resource located in the San Juan province of Argentina. The All Other group primarily consists of assets, including cash and cash equivalents, investments, revenues, and expenses of various corporate and support functions. The Company evaluates performance and allocates resources based on income or loss before income taxes. The following financial information relates to the Company’s business segments: (In thousands) South American Properties Three Months Ended June 30, 2016 Mine Production PGM Recycling Canadian Properties All Other Total Revenues $ 106,395 $ 59,188 $ — $ — $ 100 $ 165,683 Depletion, depreciation and amortization $ 20,517 $ 194 $ — $ — $ — $ 20,711 General and administrative expenses $ — $ — $ 203 $ 375 $ 7,733 $ 8,311 Interest income $ — $ 466 $ 1 $ — $ 493 $ 960 Interest expense $ — $ — $ — $ — $ 4,067 $ 4,067 Income (loss) before income taxes $ 10,288 $ 2,971 $ (219 ) $ (1,385 ) $ (11,086 ) $ 569 Capital expenditures $ 19,418 $ — $ — $ — $ 166 $ 19,584 Total assets $ 626,078 $ 66,013 $ 25,953 $ 103,586 $ 459,601 $ 1,281,231 (In thousands) South American Properties Three Months Ended June 30, 2015 Mine Production PGM Recycling Canadian Properties * All Other Total Revenues $ 118,968 $ 66,316 $ — $ — $ 100 $ 185,384 Depletion, depreciation and amortization $ 16,942 $ 256 $ — $ — $ — $ 17,198 General and administrative expenses $ — $ — $ 280 $ 172 $ 9,944 $ 10,396 Interest income $ — $ 416 $ 2 $ 5 $ 301 $ 724 Interest expense $ — $ — $ — $ — $ 5,312 $ 5,312 Income (loss) before impairment charge and income taxes $ 21,394 $ 2,036 $ (354 ) $ (104 ) $ (14,838 ) $ 8,134 Impairment charge $ — $ — $ 46,772 $ — $ — $ 46,772 Income (loss) after impairment charge and before income tax provision $ 21,394 $ 2,036 $ (47,126 ) $ (104 ) $ (14,838 ) $ (38,638 ) Capital expenditures $ 27,161 $ 104 $ — $ 46 $ 3,005 $ 30,316 Total assets $ 612,486 $ 68,927 $ 27,735 $ 105,058 $ 564,466 $ 1,378,672 * Total assets includes cash and cash equivalents of $17.8 million . (In thousands) South American Six Months Ended June 30, 2016 Mine Production PGM Recycling Canadian Properties All Other Total Revenues $ 192,197 $ 106,924 $ — $ — $ 200 $ 299,321 Depletion, depreciation and amortization $ 37,586 $ 385 $ — $ — $ — $ 37,971 General and administrative expenses $ — $ — $ 339 $ 683 $ 15,586 $ 16,608 Interest income $ — $ 759 $ 1 $ 1 $ 909 $ 1,670 Interest expense $ — $ — $ — $ — $ 8,249 $ 8,249 Income (loss) before income taxes $ 11,579 $ 4,764 $ (387 ) $ (2,628 ) $ (23,250 ) $ (9,922 ) Capital expenditures $ 37,895 $ 10 $ — $ — $ 521 $ 38,426 Total assets $ 626,078 $ 66,013 $ 25,953 $ 103,586 $ 459,601 $ 1,281,231 (In thousands) South American Six Months Ended June 30, 2015 Mine Production PGM Recycling Canadian Properties * All Other Total Revenues $ 244,706 $ 140,998 $ — $ — $ 200 $ 385,904 Depletion, depreciation and amortization $ 33,811 $ 508 $ — $ — $ — $ 34,319 General and administrative expenses $ — $ — $ 515 $ 354 $ 17,872 $ 18,741 Interest income $ — $ 818 $ 6 $ 19 $ 583 $ 1,426 Interest expense $ — $ — $ — $ — $ 10,616 $ 10,616 Income (loss) before impairment charge and income tax provision $ 50,222 $ 4,163 $ (787 ) $ (877 ) $ (27,743 ) $ 24,978 Impairment charge $ — $ — $ 46,772 $ — $ — $ 46,772 Income (loss) before income taxes $ 50,222 $ 4,163 $ (47,559 ) $ (877 ) $ (27,743 ) $ (21,794 ) Capital expenditures $ 52,709 $ 164 $ — $ 46 $ 5,299 $ 58,218 Total assets $ 612,486 $ 68,927 $ 27,735 $ 105,058 $ 564,466 $ 1,378,672 * Total assets includes cash and cash equivalents of $17.8 million .

Investments

Investments	6 Months Ended
	Jun. 30, 2016
Investments, Debt and Equity Securities [Abstract]
Investments	INVESTMENTS The Company classifies the marketable securities in which it invests as available-for-sale securities. These securities are measured at fair value in the financial statements with unrealized gains or losses recorded in Other comprehensive income in the Company's Consolidated Statements of Comprehensive Income (Loss) . At the time the securities are sold or otherwise disposed of, gross realized gains and losses are included in Net income (loss) Gross realized gains and losses are based on the carrying value (cost, net of discounts or premiums) of the sold investment. The amounts reclassified out of Other comprehensive income during the three and six months ended June 30, 2016 and 2015 were insignificant. The amortized cost, gross unrealized gains, gross unrealized losses, and fair value of available-for-sale investment securities by major security type and class of security at June 30, 2016 and December 31, 2015 were as follows: Investments (In thousands) Amortized cost Gross unrealized gains Gross unrealized losses Fair value 2016 Federal agency notes $ 279,850 $ 259 $ (46 ) $ 280,063 Commercial paper 31,935 39 — 31,974 Subtotal 311,785 298 (46 ) 312,037 Mutual funds 704 274 — 978 Total $ 312,489 $ 572 $ (46 ) $ 313,015 2015 Federal agency notes $ 285,276 $ — $ (519 ) $ 284,757 Commercial paper 31,730 — (58 ) 31,672 Subtotal 317,006 — (577 ) 316,429 Mutual funds 482 261 — 743 Total $ 317,488 $ 261 $ (577 ) $ 317,172 The mutual funds included in the investment table above are included in Other noncurrent assets on the Company's Consolidated Balance Sheets . Included in the investments balance at June 30, 2016 and December 31, 2015 is $18.5 million which has been reserved as collateral on the Company's undrawn letters of credit of approximately $17.5 million . The maturities of available-for-sale securities at June 30, 2016 were as follows: (In thousands) Amortized cost Fair value Federal agency notes Due in one year or less $ 214,745 $ 214,821 Due after one year through two years 65,105 65,242 Total $ 279,850 $ 280,063 Commercial paper Due in one year or less $ 16,485 $ 16,488 Due after one year through two years 15,450 15,486 Total $ 31,935 $ 31,974 The Company has long-term investments in various Canadian junior exploration companies, recorded on the Company's Consolidated Balance Sheets at cost. The Company sold its investment in Marathon Gold in the second quarter of 2016 and recorded a gain of $0.5 million . The Company determined there was no impairment for the remaining long-term investments for the three and six months ended June 30, 2016. For the three and six months ended June 30, 2015, the Company determined that certain of its remaining long-term investments were other than temporarily impaired and recorded a loss of less than $0.1 million . These long-term investments totaled approximately $0.1 million at June 30, 2016 and $0.5 million at December 31, 2015 , and are recorded in Other noncurrent assets on the Company's Consolidated Balance Sheets .

Inventories

Inventories	6 Months Ended
	Jun. 30, 2016
Inventory Disclosure [Abstract]
Inventories	INVENTORIES The Company carries items in its inventories at the lower of cost or market value. If the market value in any period falls below the carrying value, the carrying value of the inventory item is reduced to its market value. For purposes of inventory accounting, the market value of inventory is generally deemed equal to the Company’s current cost of replacing the inventory, provided that: (1) the market value of the inventory may not exceed the estimated selling price of such inventory in the ordinary course of business less reasonably predictable costs of completion and disposal, and (2) the market value may not be less than net realizable value reduced by an allowance for a normal profit margin. No reduction to inventory value was necessary in the first six months of 2016 or 2015 . The costs of PGM mined inventories as of any date are determined based on combined production costs per ounce and include all inventoriable production costs, including direct labor, direct materials, depletion, depreciation and amortization and other overhead costs relating to mining and processing activities incurred as of such date. Costs are aggregated and averaged for mined material carried in inventory. The costs of PGM recycling inventories as of any date are determined based on the acquisition cost of the recycled material and include all inventoriable processing costs, including direct labor, direct materials, depreciation and third-party refining costs which relate to the processing activities incurred as of such date. Costs incurred are allocated and tracked separately for each specific lot of recycling material (including material tolled on behalf of others). Inventories reflected in the accompanying balance sheets consisted of the following: June 30, December 31, (In thousands) 2016 2015 Metals inventory Raw ore $ 4,123 $ 4,234 Concentrate and in-process 58,176 43,727 Finished goods 32,177 32,618 Total metals inventory 94,476 80,579 Materials and supplies 19,416 21,493 Total inventories $ 113,892 $ 102,072

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2016
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE Basic earnings per share attributable to common stockholders is computed by dividing net earnings available to common stockholders by the weighted average number of shares of common stock outstanding during the period. Diluted earnings per share attributable to common stockholders reflects the potential dilution that could occur if the Company’s dilutive outstanding stock options or nonvested shares were exercised or vested, the contingently issuable shares were issued and the Company’s convertible debt was converted. The Company currently has only one class of shares of capital stock outstanding. No adjustment was made to reported net loss attributable to common stockholders when calculating diluted loss per share attributable to common stockholders for the three months ended June 30, 2015 and for the six months ended June 30, 2016 and 2015 because the Company reported a consolidated net loss attributable to common stockholders and inclusion of these shares would have been anti-dilutive. Potential dilutive common shares include those associated with outstanding stock options, restricted stock units, performance shares and convertible debentures. The following table shows the reconciliation of the computation of basic and diluted shares and the related impact on income for the three months ended June 30, 2016: Three Months Ended June 30, 2016 (In thousands, except per share amounts) Income (Numerator) Weighted Average Shares (Denominator) Per Share Amount Basic EPS Net income attributable to common stockholders $ 784 121,074 $ 0.01 Effect of Dilutive Securities Stock options — 1 Nonvested shares — 72 Contingently issuable shares — 233 Diluted EPS Net income attributable to common stockholders $ 784 121,380 $ 0.01 The following table shows the shares that were excluded from the computation of diluted earnings per share for the three and six months ended June 30, 2016 and 2015: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Stock options — 6 1 7 Restricted stock units 8 26 136 61 Performance shares 159 143 328 136 1.875% Convertible debentures, net of tax 22 95 22 95 1.75% Convertible debentures, net of tax 30,413 36,003 30,413 36,003

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants. A three-level fair value hierarchy prioritizes the inputs used to measure fair value. This hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The classification of each financial asset or liability within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement. The three levels of inputs used to measure fair value are as follows: • Level 1 - Quoted prices in active markets for identical assets or liabilities. • Level 2 - Observable inputs other than quoted prices included in Level 1 such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or inputs that are observable or can be corroborated by observable market data. • Level 3 - Unobservable inputs supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Financial assets and liabilities measured at fair value on a recurring basis at June 30, 2016 and December 31, 2015 , consisted of the following: (In thousands) Fair Value Measurements At June 30, 2016 Total Level 1 Level 2 Level 3 Money market fund $ 60,754 $ 60,754 $ — $ — Mutual funds $ 978 $ 978 $ — $ — Investments Federal agency notes $ 280,063 $ — $ 280,063 $ — Commercial paper $ 31,974 $ — $ 31,974 $ — (In thousands) Fair Value Measurements At December 31, 2015 Total Level 1 Level 2 Level 3 Money market fund $ 54,761 $ 54,761 $ — $ — Mutual funds $ 743 $ 743 $ — $ — Investments Federal agency notes $ 284,757 $ — $ 284,757 $ — Commercial paper $ 31,672 $ — $ 31,672 $ — The money market funds are recorded in Cash and cash equivalents on the Company's Consolidated Balance Sheets . The fair value of the mutual funds is based on market prices that are readily available and are recorded in Other noncurrent assets on the Company's Consolidated Balance Sheets . The fair value of the investments is valued indirectly using observable data, quoted prices for similar assets or liabilities in active markets. Unrealized gains or losses on mutual funds and investments are recorded in Accumulated other comprehensive income (loss) on the Company's Consolidated Balance Sheets . Assets and liabilities measured at fair value on a nonrecurring basis at June 30, 2016 and December 31, 2015 , consisted of the following: (In thousands) Fair Value Measurements At June 30, 2016 Total Level 1 Level 2 Level 3 1.875% Convertible debentures $ 524 $ — $ 524 $ — 1.75% Convertible debentures $ 307,369 $ — $ 307,369 $ — (In thousands) Fair Value Measurements At December 31, 2015 Total Level 1 Level 2 Level 3 1.875% Convertible Debentures $ 524 $ — $ 524 $ — 1.75% Convertible Debentures $ 285,446 $ — $ 285,446 $ — Long-term investments $ 524 $ 524 $ — $ — The Company determined the fair value of the liability component of its outstanding 1.75% convertible debentures at June 30, 2016 and December 31, 2015 by using observable market based information for debt instruments of similar amounts and duration. The Company used the book value of its outstanding 1.875% convertible debentures to represent the fair value at June 30, 2016 and December 31, 2015 . The fair value of the Company's long-term investments in certain Canadian junior exploration companies at December 31, 2015 is based on quoted market prices which are readily available.

Related Parties

Related Parties	6 Months Ended
	Jun. 30, 2016
Related Party Transactions [Abstract]
Related Parties	RELATED PARTIES The Company purchased Mitsubishi's 25% ownership interest in SCI, the Company's subsidiary, in the fourth quarter of 2015. The Company made PGM sales of $7.6 million to Mitsubishi in the three months ended June 30, 2015 , and $23.5 million , for the six months ended June 30, 2015 .

General (Policies)

General (Policies)	6 Months Ended
	Jun. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Use of Estimates	The preparation of the Company’s consolidated financial statements in conformity with United States generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the amounts reported in these consolidated financial statements and accompanying notes. The more significant areas requiring the use of management’s estimates relate to mineral reserves, reclamation and environmental obligations, valuation allowance for deferred tax assets, useful lives utilized for depreciation, amortization and accretion calculations, future cash flows from long-lived assets, and fair value of derivatives and other financial instruments. Actual results could differ from these estimates.
New Accounting Pronouncements	On May 28, 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers , which requires an entity to recognize the amount of revenue it expects to be entitled to for the transfer of promised goods or services to customers. In August 2015, the FASB issued ASU 2015-14, Deferral of the Effective Date , which defers the effective date of ASU 2014-09 by one year to January 1, 2018. ASU 2014-09 will replace most existing revenue recognition guidance in GAAP. The standard permits the use of either the retrospective or cumulative effect transition method. The Company continues to evaluate the effect that ASU 2014-09 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early adoption is not permitted. On April 7, 2015, as part of its initiative to simplify and reduce complexity in financial statements, the FASB issued ASU 2015-03, Interest - Imputation, (Subtopic 835-30): Simplifying the Presentation of Debt Issuance. This ASU requires the debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the debt liability. Also, it requires retrospective application for all prior periods presented in the financial statements and a disclosure of the nature of and reason for the change in accounting principle, the transition method, a description of the prior-period information that has been retrospectively adjusted and the effect of the change on the financial statement line items. ASU 2015-03 is effective for financial statements issued for fiscal years beginning after December 31, 2015, and interim periods within those fiscal years. Early adoption was permitted for financial statements that had not been previously issued. The Company elected early adoption of ASU 2015-03 and reclassified Deferred debt issue costs against the related liability for all periods presented. Prior to the adoption of ASU 2015-03, the balance reported at December 31, 2015 for total Long-term debt and capital lease obligations was $258.9 million , and after adoption and reclassification of Deferred debt issue costs of $3.8 million , the total balance reported at December 31, 2015 became $255.1 million . On July 22, 2015, as part of its initiative to simplify and reduce complexity in financial statements, the FASB issued ASU 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory. ASU 2015-11, which will change the measurement principle for inventory from the lower of cost or market to the lower of cost and net realizable value. ASU 2015-11 is effective for financial statements issued for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. The Company is evaluating the effect that ASU 2015-11 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. The ASU requires prospective adoption and permits early adoption. On February 25, 2016, the FASB issued ASU 2016-02, Leases, (Topic 840) , which requires an entity that leases assets, with terms of more than 12 months, to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. ASU 2016-02 is effective for financial statements issued for fiscal years beginning after December 31, 2018, and interim periods within those fiscal years. The Company is evaluating the effect that ASU 2016-02 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early adoption is permitted. On March 30, 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employees Shared-Based Payment Accounting. The ASU will change several aspects within share based payments: (1) accounting for income taxes, (2) classification of excess tax benefits, (3) forfeitures, (4) minimum statutory tax withholding requirements, (5) classification of employee taxes paid when an employer withholds shares for tax-withholding purposes, (6) practical expedient - expected term, (7) intrinsic value, and (8) eliminating the indefinite deferral. ASU 2016-09 is effective for financial statements issued for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. The Company is evaluating the effect that ASU 2016-09 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early adoption is permitted in any interim or annual period provided that the entire ASU is adopted.

Sales (Tables)

Sales (Tables)	6 Months Ended
	Jun. 30, 2016
Sales Revenue, Goods, Net [Abstract]
Percentage of Total Revenues From Significant Customers	Total sales to significant customers as a percentage of total revenues for the three and six months ended June 30, 2016 and 2015 were as follows: Three Months Ended Six Months Ended June 30, June 30, 2016 2015 (1) 2016 (1) 2015 (1) Customer A 72 % 80 % 76 % 77 % Customer B 10 % — — — (1) The “—” symbol represents less than 10% of total revenues.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Company's outstanding commodity derivatives	The following is a summary of the Company's outstanding commodity derivatives in its Recycling Business Segment at June 30, 2016 : PGM Recycling: Fixed Forward Contracts Platinum Palladium Rhodium Settlement Period Ounces Average Price/Ounce Ounces Average Price/Ounce Ounces Average Price/Ounce Third Quarter 2016 34,034 $ 1,005 54,508 $ 571 7,344 $ 675 Fourth Quarter 2016 4,356 $ 993 4,587 $ 564 1,952 $ 652

Share Compensation Plans (Table

Share Compensation Plans (Tables)	6 Months Ended
	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Changes In The Company's Nonvested Shares	Share activity under nonvested performance-based restricted stock unit awards activity during the first six months of 2016 is detailed in the following table: Nonvested Shares Weighted-Average Grant-Date Fair Value Nonvested performance-based shares at January 1, 2016 379,277 $ 15.34 Granted * 186,285 11.45 Vested — Forfeited — — Nonvested performance-based shares at March 31, 2016 565,562 $ 14.06 No activity — Nonvested performance-based shares at June 30, 2016 565,562 $ 14.06 * The number of performance-based shares granted is based on the target award amounts in the performance restricted stock unit award agreements. Nonvested time-based share activity during the six months ended June 30, 2016 , is detailed in the following table: Nonvested Shares Weighted-Average Grant-Date Fair Value Nonvested time-based shares at January 1, 2016 186,655 $ 13.97 Granted 206,974 8.03 Vested (33,080 ) 13.88 Forfeited — — Nonvested time-based shares at March 31, 2016 360,549 $ 10.68 Granted 2,652 10.13 Vested (2,747 ) 14.24 Forfeited (565 ) 13.02 Nonvested time-based shares at June 30, 2016 359,889 $ 10.63
Compensation Expense of Nonvested Shares	The following table presents the compensation expense of the nonvested shares outstanding at June 30, 2016 , to be recognized over the remaining vesting periods: (In thousands) Time-based shares Performance -based shares Remaining 2016 $ 1,106 $ 1,158 2017 1,203 1,611 2018 583 757 2019 3 — Total $ 2,895 $ 3,526

Debt and Capital Lease Obliga26

Debt and Capital Lease Obligations (Tables)	6 Months Ended
	Jun. 30, 2016
Debt Disclosure [Abstract]
Schedule of Debt Issuance Costs, Interest Expense and Cash Paid For Interest	The following table reflects the amortization of debt issuance costs, interest expense and cash payments on the Company's outstanding debt for the three and six months ended June 30, 2016 and 2015: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 1.75% Convertible Debentures Amortization of debt issuance costs $ 221 $ 239 $ 437 $ 475 Interest expense, net of capitalized interest $ 3,877 $ 5,013 $ 7,869 $ 10,013 Cash payments for interest $ 2,933 $ — $ 2,933 $ 3,472 1.875% Convertible Debentures Interest expense, net of capitalized interest $ 2 $ — $ — $ — Cash payments for interest $ — $ — $ 5 $ 21 Asset-Backed Revolving Credit Facility Amortization of debt issuance costs $ — $ 68 $ — $ 135 Fees $ — $ 335 $ — $ 586
Schedule of Current and Long-term Debt	The Company's total current and long-term debt balances at June 30, 2016 and December 31, 2015 were as follows: June 30, 2016 December 31, 2015 (In thousands) Current Long-Term Current Long-Term 1.75% Convertible Debentures Aggregate principal $ — $ 335,150 $ — $ 335,150 Debt discount — (67,989 ) — (76,754 ) Deferred debt issue costs — (3,384 ) — (3,821 ) Debt balance — 263,777 — 254,575 1.875% Convertible Debentures — 524 — 524 Capital lease obligation — — 580 — Small land purchase — — 77 — Total debt balances $ — $ 264,301 $ 657 $ 255,099

Mineral Properties and Mine D27

Mineral Properties and Mine Development (Tables)	6 Months Ended
	Jun. 30, 2016
Extractive Industries [Abstract]
Schedule of Mineral Properties and Mine Development	Mineral properties and mine development reflected in the accompanying balance sheets consisted of the following: June 30, December 31, (In thousands) 2016 2015 Mineral Properties: Montana, United States of America Stillwater Mine $ 1,950 $ 1,950 Ontario, Canada Marathon properties 8,560 8,560 San Juan, Argentina Altar property 101,970 101,970 Mine Development: Montana, United States of America Stillwater Mine 735,009 697,781 East Boulder Mine 227,564 220,281 1,075,053 1,030,542 Accumulated depletion and amortization (489,190 ) (457,311 ) Total mineral properties and mine development, net $ 585,863 $ 573,231

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	6 Months Ended
	Jun. 30, 2016
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	Property, plant and equipment reflected in the accompanying consolidated balance sheets consisted of the following: June 30, December 31, (In thousands) 2016 2015 Machinery and equipment $ 161,906 $ 161,292 Buildings and structural components 174,278 173,580 Land 11,740 11,740 Construction-in-progress: Stillwater Mine 2,094 2,615 East Boulder Mine 266 435 Marathon 148 148 Processing facilities and other 1,469 1,982 351,901 351,792 Accumulated depreciation (249,564 ) (241,835 ) Total property, plant, and equipment, net $ 102,337 $ 109,957
Schedule Capital Expenditures	The Company's total capital outlay for mine development and property, plant and equipment for the six months ended June 30, 2016 and 2015 were as follows: June 30, (In thousands) 2016 2015 Stillwater Mine $ 38,867 $ 47,171 East Boulder Mine 7,286 9,953 Other 480 4,054 Total U.S. capital expenditures 46,633 61,178 Foreign capital expenditures — 46 Non-cash capitalized interest and depreciation (5,321 ) (4,397 ) Change in accounts payables for capital expenditures (2,886 ) 1,391 Cash capital spend for the period $ 38,426 $ 58,218

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2016
Segment Reporting [Abstract]
Financial Information Related To The Company's Business Segments	The following financial information relates to the Company’s business segments: (In thousands) South American Properties Three Months Ended June 30, 2016 Mine Production PGM Recycling Canadian Properties All Other Total Revenues $ 106,395 $ 59,188 $ — $ — $ 100 $ 165,683 Depletion, depreciation and amortization $ 20,517 $ 194 $ — $ — $ — $ 20,711 General and administrative expenses $ — $ — $ 203 $ 375 $ 7,733 $ 8,311 Interest income $ — $ 466 $ 1 $ — $ 493 $ 960 Interest expense $ — $ — $ — $ — $ 4,067 $ 4,067 Income (loss) before income taxes $ 10,288 $ 2,971 $ (219 ) $ (1,385 ) $ (11,086 ) $ 569 Capital expenditures $ 19,418 $ — $ — $ — $ 166 $ 19,584 Total assets $ 626,078 $ 66,013 $ 25,953 $ 103,586 $ 459,601 $ 1,281,231 (In thousands) South American Properties Three Months Ended June 30, 2015 Mine Production PGM Recycling Canadian Properties * All Other Total Revenues $ 118,968 $ 66,316 $ — $ — $ 100 $ 185,384 Depletion, depreciation and amortization $ 16,942 $ 256 $ — $ — $ — $ 17,198 General and administrative expenses $ — $ — $ 280 $ 172 $ 9,944 $ 10,396 Interest income $ — $ 416 $ 2 $ 5 $ 301 $ 724 Interest expense $ — $ — $ — $ — $ 5,312 $ 5,312 Income (loss) before impairment charge and income taxes $ 21,394 $ 2,036 $ (354 ) $ (104 ) $ (14,838 ) $ 8,134 Impairment charge $ — $ — $ 46,772 $ — $ — $ 46,772 Income (loss) after impairment charge and before income tax provision $ 21,394 $ 2,036 $ (47,126 ) $ (104 ) $ (14,838 ) $ (38,638 ) Capital expenditures $ 27,161 $ 104 $ — $ 46 $ 3,005 $ 30,316 Total assets $ 612,486 $ 68,927 $ 27,735 $ 105,058 $ 564,466 $ 1,378,672 * Total assets includes cash and cash equivalents of $17.8 million . (In thousands) South American Six Months Ended June 30, 2016 Mine Production PGM Recycling Canadian Properties All Other Total Revenues $ 192,197 $ 106,924 $ — $ — $ 200 $ 299,321 Depletion, depreciation and amortization $ 37,586 $ 385 $ — $ — $ — $ 37,971 General and administrative expenses $ — $ — $ 339 $ 683 $ 15,586 $ 16,608 Interest income $ — $ 759 $ 1 $ 1 $ 909 $ 1,670 Interest expense $ — $ — $ — $ — $ 8,249 $ 8,249 Income (loss) before income taxes $ 11,579 $ 4,764 $ (387 ) $ (2,628 ) $ (23,250 ) $ (9,922 ) Capital expenditures $ 37,895 $ 10 $ — $ — $ 521 $ 38,426 Total assets $ 626,078 $ 66,013 $ 25,953 $ 103,586 $ 459,601 $ 1,281,231 (In thousands) South American Six Months Ended June 30, 2015 Mine Production PGM Recycling Canadian Properties * All Other Total Revenues $ 244,706 $ 140,998 $ — $ — $ 200 $ 385,904 Depletion, depreciation and amortization $ 33,811 $ 508 $ — $ — $ — $ 34,319 General and administrative expenses $ — $ — $ 515 $ 354 $ 17,872 $ 18,741 Interest income $ — $ 818 $ 6 $ 19 $ 583 $ 1,426 Interest expense $ — $ — $ — $ — $ 10,616 $ 10,616 Income (loss) before impairment charge and income tax provision $ 50,222 $ 4,163 $ (787 ) $ (877 ) $ (27,743 ) $ 24,978 Impairment charge $ — $ — $ 46,772 $ — $ — $ 46,772 Income (loss) before income taxes $ 50,222 $ 4,163 $ (47,559 ) $ (877 ) $ (27,743 ) $ (21,794 ) Capital expenditures $ 52,709 $ 164 $ — $ 46 $ 5,299 $ 58,218 Total assets $ 612,486 $ 68,927 $ 27,735 $ 105,058 $ 564,466 $ 1,378,672 * Total assets includes cash and cash equivalents of $17.8 million .

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2016
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities	The amortized cost, gross unrealized gains, gross unrealized losses, and fair value of available-for-sale investment securities by major security type and class of security at June 30, 2016 and December 31, 2015 were as follows: Investments (In thousands) Amortized cost Gross unrealized gains Gross unrealized losses Fair value 2016 Federal agency notes $ 279,850 $ 259 $ (46 ) $ 280,063 Commercial paper 31,935 39 — 31,974 Subtotal 311,785 298 (46 ) 312,037 Mutual funds 704 274 — 978 Total $ 312,489 $ 572 $ (46 ) $ 313,015 2015 Federal agency notes $ 285,276 $ — $ (519 ) $ 284,757 Commercial paper 31,730 — (58 ) 31,672 Subtotal 317,006 — (577 ) 316,429 Mutual funds 482 261 — 743 Total $ 317,488 $ 261 $ (577 ) $ 317,172
Schedule of Maturities of Available-for-sale Securities	The maturities of available-for-sale securities at June 30, 2016 were as follows: (In thousands) Amortized cost Fair value Federal agency notes Due in one year or less $ 214,745 $ 214,821 Due after one year through two years 65,105 65,242 Total $ 279,850 $ 280,063 Commercial paper Due in one year or less $ 16,485 $ 16,488 Due after one year through two years 15,450 15,486 Total $ 31,935 $ 31,974

Inventories (Tables)

Inventories (Tables)	6 Months Ended
	Jun. 30, 2016
Inventory Disclosure [Abstract]
Components of Inventories	Inventories reflected in the accompanying balance sheets consisted of the following: June 30, December 31, (In thousands) 2016 2015 Metals inventory Raw ore $ 4,123 $ 4,234 Concentrate and in-process 58,176 43,727 Finished goods 32,177 32,618 Total metals inventory 94,476 80,579 Materials and supplies 19,416 21,493 Total inventories $ 113,892 $ 102,072

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2016
Earnings Per Share [Abstract]
Reconciliation of Computation of Basic and Diluted Shares and the Related Impact on Income	The following table shows the reconciliation of the computation of basic and diluted shares and the related impact on income for the three months ended June 30, 2016: Three Months Ended June 30, 2016 (In thousands, except per share amounts) Income (Numerator) Weighted Average Shares (Denominator) Per Share Amount Basic EPS Net income attributable to common stockholders $ 784 121,074 $ 0.01 Effect of Dilutive Securities Stock options — 1 Nonvested shares — 72 Contingently issuable shares — 233 Diluted EPS Net income attributable to common stockholders $ 784 121,380 $ 0.01
Anti-dilutive Shares Excluded From Computation of Diluted Earnings Per Share	The following table shows the shares that were excluded from the computation of diluted earnings per share for the three and six months ended June 30, 2016 and 2015: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2016 2015 2016 2015 Stock options — 6 1 7 Restricted stock units 8 26 136 61 Performance shares 159 143 328 136 1.875% Convertible debentures, net of tax 22 95 22 95 1.75% Convertible debentures, net of tax 30,413 36,003 30,413 36,003

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2016
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	Financial assets and liabilities measured at fair value on a recurring basis at June 30, 2016 and December 31, 2015 , consisted of the following: (In thousands) Fair Value Measurements At June 30, 2016 Total Level 1 Level 2 Level 3 Money market fund $ 60,754 $ 60,754 $ — $ — Mutual funds $ 978 $ 978 $ — $ — Investments Federal agency notes $ 280,063 $ — $ 280,063 $ — Commercial paper $ 31,974 $ — $ 31,974 $ — (In thousands) Fair Value Measurements At December 31, 2015 Total Level 1 Level 2 Level 3 Money market fund $ 54,761 $ 54,761 $ — $ — Mutual funds $ 743 $ 743 $ — $ — Investments Federal agency notes $ 284,757 $ — $ 284,757 $ — Commercial paper $ 31,672 $ — $ 31,672 $ —
Financial Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis	Assets and liabilities measured at fair value on a nonrecurring basis at June 30, 2016 and December 31, 2015 , consisted of the following: (In thousands) Fair Value Measurements At June 30, 2016 Total Level 1 Level 2 Level 3 1.875% Convertible debentures $ 524 $ — $ 524 $ — 1.75% Convertible debentures $ 307,369 $ — $ 307,369 $ — (In thousands) Fair Value Measurements At December 31, 2015 Total Level 1 Level 2 Level 3 1.875% Convertible Debentures $ 524 $ — $ 524 $ — 1.75% Convertible Debentures $ 285,446 $ — $ 285,446 $ — Long-term investments $ 524 $ 524 $ — $ —

General (Details)

General (Details) - Accounting Standards Update 2015-03 [Member] $ in Millions	Dec. 31, 2015USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt	$ 255.1
Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt	258.9
Scenario, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt	$ 3.8

Sales (Details)

Sales (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2014	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Sales Revenue, Goods, Net [Abstract]
Revenues from by-product sales		$ 6.1	$ 6.9	$ 11.3	$ 13.7
Term of refining agreement	5 years
Customer Concentration Risk [Member] | Total revenues [Member] | Customer A [Member]
Revenue, Major Customer [Line Items]
Sales to significant customers (10% or more), percentage of total revenues		72.00%	80.00%	76.00%	77.00%
Customer Concentration Risk [Member] | Total revenues [Member] | Customer B [Member]
Revenue, Major Customer [Line Items]
Sales to significant customers (10% or more), percentage of total revenues		10.00%

Asset Impairment (Details)

Asset Impairment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge	$ 0	$ 46,772	$ 0	$ 46,772
Marathon Property [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge		46,800
Mineral properties, fair value		$ 8,600		$ 8,600

Noncontrolling Interest (Detail

Noncontrolling Interest (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Noncontrolling Interest [Abstract]
Noncontrolling interest, ownership percentage by noncontrolling owners		25.00%
Purchase of noncontrolling interest, total consideration		$ 5,200
Purchase of noncontrolling interest, net of cash acquired		$ 1,000
Net income (loss) attributable to noncontrolling interest	$ 0		$ (11,542)	$ 0	$ (11,657)

Derivative Instruments (Company

Derivative Instruments (Company's Outstanding Commodity Derivatives) (Details)	6 Months Ended
	Jun. 30, 2016oz$ / oz
Third Quarter 2016 [Member] | Platinum [Member]
Derivative [Line Items]
Ounces | oz	34,034
Average Price/Ounce | $ / oz	1,005
Third Quarter 2016 [Member] | Palladium [Member]
Derivative [Line Items]
Ounces | oz	54,508
Average Price/Ounce | $ / oz	571
Third Quarter 2016 [Member] | Rhodium [Member]
Derivative [Line Items]
Ounces | oz	7,344
Average Price/Ounce | $ / oz	675
Fourth Quarter 2016 [Member] | Platinum [Member]
Derivative [Line Items]
Ounces | oz	4,356
Average Price/Ounce | $ / oz	993
Fourth Quarter 2016 [Member] | Palladium [Member]
Derivative [Line Items]
Ounces | oz	4,587
Average Price/Ounce | $ / oz	564
Fourth Quarter 2016 [Member] | Rhodium [Member]
Derivative [Line Items]
Ounces | oz	1,952
Average Price/Ounce | $ / oz	652

Share Compensation Plans (Narra

Share Compensation Plans (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance	11.6		11.6
Nonvested time-based shares [Member] | General and administrative expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 0.6	$ 0.4	$ 1	$ 0.8
Nonvested performance-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Nonvested performance-based shares [Member] | General and administrative expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 0.5	$ 0.4	$ 0.9	$ 0.6
2004 and 2012 Plans Combined [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available and reserved for grant	4.1		4.1
2012 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance	5		5
2004 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance	5.2		5.2
General Employee Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance	1.4		1.4

Share Compensation Plans (Chang

Share Compensation Plans (Changes In The Company's Nonvested Shares) (Details) - $ / shares	3 Months Ended
	Jun. 30, 2016	Mar. 31, 2016
Nonvested time-based shares [Member]
Nonvested Shares
Nonvested Shares, Beginning Balance	360,549	186,655
Nonvested Shares, Granted	2,652	206,974
Nonvested Shares, Vested	(2,747)	(33,080)
Nonvested Shares, Forfeited	(565)	0
Nonvested Shares, Ending Balance	359,889	360,549
Weighted-Average Grant-Date Fair Value
Nonvested shares, Weighted-Average Grant-Date Fair Value, Beginning Balance (in usd per share)	$ 10.68	$ 13.97
Nonvested shares, Weighted-Average Grant-Date Fair Value, Granted (in usd per share)	10.13	8.03
Nonvested shares, Weighted-Average Grant-Date Fair Value, Vested (in usd per share)	14.24	13.88
Nonvested shares, Weighted-Average Grant-Date Fair Value, Forfeited (in usd per share)	13.02	0
Nonvested shares, Weighted-Average Grant-Date Fair Value, Ending Balance (in usd per share)	$ 10.63	$ 10.68
Nonvested performance-based shares [Member]
Nonvested Shares
Nonvested Shares, Beginning Balance	565,562	379,277
Nonvested Shares, Granted		186,285
Nonvested Shares, Vested		0
Nonvested Shares, Forfeited		0
Nonvested Shares, Ending Balance	565,562	565,562
Weighted-Average Grant-Date Fair Value
Nonvested shares, Weighted-Average Grant-Date Fair Value, Beginning Balance (in usd per share)	$ 14.06	$ 15.34
Nonvested shares, Weighted-Average Grant-Date Fair Value, Granted (in usd per share)		11.45
Nonvested shares, Weighted-Average Grant-Date Fair Value, Vested (in usd per share)
Nonvested shares, Weighted-Average Grant-Date Fair Value, Forfeited (in usd per share)		0
Nonvested shares, Weighted-Average Grant-Date Fair Value, Ending Balance (in usd per share)	$ 14.06	$ 14.06

Share Compensation Plans (Compe

Share Compensation Plans (Compensation Expense of Nonvested Shares) (Details) $ in Thousands	Jun. 30, 2016USD ($)
Nonvested time-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining 2,016	$ 1,106
2,017	1,203
2,018	583
2,019	3
Total	2,895
Nonvested performance-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining 2,016	1,158
2,017	1,611
2,018	757
2,019	0
Total	$ 3,526

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Income tax benefit (provision)	$ 215	$ (380)	$ 776	$ 5,663
Discrete income tax benefit (provision)			(3,400)	9,700
Discrete income tax benefit, restructure of internal operations and creation of subsidiary				8,600
Uncertain tax benefits	3,400		3,400
Interest and penalties accrued	$ 100		100
Cash paid for income taxes			$ 300	$ 11,100

Debt and Capital Lease Obliga43

Debt and Capital Lease Obligations (Narrative) (Details)	Dec. 31, 2015USD ($)	Oct. 31, 2012USD ($)$ / sharesshares	Jan. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Jun. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2015USD ($)
Debt Instruments
Credit facility termination fees	$ 200,000
Capitalized Interest
Capitalized interest					$ 2,000,000		$ 1,400,000	$ 3,900,000	$ 2,700,000
1.75% Convertible Debentures [Member]
Debt Instruments
Debt, principal amount		$ 396,750,000
Stated interest rate	1.75%	1.75%			1.75%		1.75%	1.75%	1.75%
Convertible debt ratio		0.0604961
Debt conversion price (in usd per share) | $ / shares		$ 16.53
Embedded conversion feature, warrant, conversion ratio | shares		30.2481
Embedded conversion feature, warrant, conversion price (in usd per share) | $ / shares		$ 16.53
Effective term of debt instrument		7 years
Adjustments to equity, component of convertible debt treated as additional debt discount		$ 141,600,000
Debt issuance costs		$ 12,400,000
Debt and equity issuance costs amortization period		7 years
Principal amount of debt repurchased						$ 61,600,000
Cash paid to repurchase debt						59,400,000
Reduction of debt component						50,700,000
Reduction of debt discount						10,900,000
Write off of debt and equity issuance costs						700,000
Gain (loss) on extinguishment of debt, net						(4,200,000)
Effective interest rate		8.50%
Convertible debentures	$ 254,600,000				$ 263,800,000			$ 263,800,000
Unamortized discount	76,754,000				67,989,000			67,989,000
Deferred debt issue costs	$ 3,821,000				$ 3,384,000			$ 3,384,000
1.875% Convertible Debentures [Member]
Debt Instruments
Stated interest rate	1.875%				1.875%		1.875%	1.875%	1.875%
Principal amount of debt repurchased						1,700,000
Cash paid to repurchase debt						1,600,000
Gain (loss) on extinguishment of debt, net						$ 100,000
Convertible debentures	$ 500,000				$ 500,000			$ 500,000
Credit Agreement [Member]
Debt Instruments
Debt issuance costs			$ 200,000	$ 1,100,000
Credit agreement			$ 125,000,000	$ 100,000,000
Credit Agreement [Member] | Minimum [Member]
Debt Instruments
Commitment fee on unutilized borrowing capacity			0.375%
Credit Agreement [Member] | Maximum [Member]
Debt Instruments
Commitment fee on unutilized borrowing capacity			0.50%

Debt and Capital Lease Obliga44

Debt and Capital Lease Obligations (Amortization of Debt Issuance Costs, Interest Expense and Cash Payments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Oct. 31, 2012
Debt Instrument [Line Items]
Amortization of debt issuance costs			$ 437	$ 610
1.75% Convertible Debentures [Member]
Debt Instrument [Line Items]
Stated interest rate	1.75%	1.75%	1.75%	1.75%	1.75%	1.75%
Amortization of debt issuance costs	$ 221	$ 239	$ 437	$ 475
Interest expense, net of capitalized interest	3,877	5,013	7,869	10,013
Cash payments for interest	$ 2,933	$ 0	$ 2,933	$ 3,472
1.875% Convertible Debentures [Member]
Debt Instrument [Line Items]
Stated interest rate	1.875%	1.875%	1.875%	1.875%	1.875%
Interest expense, net of capitalized interest	$ 2	$ 0	$ 0	$ 0
Cash payments for interest	0	0	5	21
Credit Agreement [Member]
Debt Instrument [Line Items]
Amortization of debt issuance costs	0	68	0	135
Fees	$ 0	$ 335	$ 0	$ 586

Debt and Capital Lease Obliga45

Debt and Capital Lease Obligations (Current and Long-Term Debt Balances) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Oct. 31, 2012
Current
Capital lease obligation	$ 0	$ 580
Small land purchase	0	77
Total debt balances, Current	0	657
Long-Term
Debt balance	264,301	255,099
Capital lease obligation	0	0
Small land purchase	$ 0	$ 0
1.75% Convertible Debentures [Member]
Debt Instrument [Line Items]
Stated interest rate	1.75%	1.75%	1.75%	1.75%
Current
Debt, Current	$ 0	$ 0
Long-Term
Aggregate principal	335,150	335,150
Debt discount	(67,989)	(76,754)
Deferred debt issue costs	(3,384)	(3,821)
Debt balance	$ 263,777	$ 254,575
1.875% Convertible Debentures [Member]
Debt Instrument [Line Items]
Stated interest rate	1.875%	1.875%	1.875%
Current
Debt, Current	$ 0	$ 0
Long-Term
Aggregate principal	$ 524	$ 524

Mineral Properties and Mine D46

Mineral Properties and Mine Development (Schedule of Mineral Properties) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Mining Properties, Mineral Rights and Mine Development [Member]
Property, Plant and Equipment [Line Items]
Mineral properties and mine development, gross	$ 1,075,053	$ 1,030,542
Accumulated depletion and amortization	(489,190)	(457,311)
Total mineral properties and mine development, net	585,863	573,231
Montana, United States of America [Member] | Mining Properties and Mineral Rights [Member] | Stillwater Mine [Member]
Property, Plant and Equipment [Line Items]
Mineral properties and mine development, gross	1,950	1,950
Montana, United States of America [Member] | Mine Development [Member] | Stillwater Mine [Member]
Property, Plant and Equipment [Line Items]
Mineral properties and mine development, gross	735,009	697,781
Montana, United States of America [Member] | Mine Development [Member] | East Boulder Mine [Member]
Property, Plant and Equipment [Line Items]
Mineral properties and mine development, gross	227,564	220,281
Ontario, Canada [Member] | Mining Properties and Mineral Rights [Member] | Marathon Property [Member]
Property, Plant and Equipment [Line Items]
Mineral properties and mine development, gross	8,560	8,560
San Juan, Argentina [Member] | Mining Properties and Mineral Rights [Member] | Altar Property [Member]
Property, Plant and Equipment [Line Items]
Mineral properties and mine development, gross	$ 101,970	$ 101,970

Property, Plant and Equipment47

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 351,901		$ 351,901		$ 351,792
Accumulated depreciation	(249,564)		(249,564)		(241,835)
Total property, plant, and equipment, net	102,337		102,337		109,957
Payments to Acquire Productive Assets [Abstract]
Non-cash capitalized interest and depreciation			(5,321)	$ (4,397)
Change in accounts payables for capital expenditures			(2,886)	1,391
Cash capital spend for the period	19,584	$ 30,316	38,426	58,218
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	161,906		161,906		161,292
Buildings and structural components [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	174,278		174,278		173,580
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	11,740		11,740		11,740
Construction-in progress [Member] | Stillwater Mine [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	2,094		2,094		2,615
Construction-in progress [Member] | East Boulder Mine [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	266		266		435
Construction-in progress [Member] | Marathon Property [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	148		148		148
Construction-in progress [Member] | Processing Facilities and Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 1,469		1,469		$ 1,982
United States [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			46,633	61,178
United States [Member] | Stillwater Mine [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			38,867	47,171
United States [Member] | East Boulder Mine [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			7,286	9,953
United States [Member] | Other Mine [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			480	4,054
Non-US [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			$ 0	$ 46

Segment Information (Narrative)

Segment Information (Narrative) (Details)	6 Months Ended
	Jun. 30, 2016SegmentBusiness_Component
Segment Reporting Information [Line Items]
Number of business segments | Segment	5
Mine Production [Member]
Segment Reporting Information [Line Items]
Number of business components | Business_Component	2

Segment Information (Financial

Segment Information (Financial Information Related To The Company's Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 165,683	$ 185,384	$ 299,321	$ 385,904
Depletion, depreciation and amortization	20,711	17,198	37,971	34,319
General and administrative expenses	8,311	10,396	16,608	18,741
Interest income	960	724	1,670	1,426
Interest expense	4,067	5,312	8,249	10,616
Income (loss) before impairment charge and income tax provision		8,134		24,978
Impairment charge	0	46,772	0	46,772
INCOME (LOSS) BEFORE INCOME TAX BENEFIT (PROVISION)	569	(38,638)	(9,922)	(21,794)
Capital expenditures	19,584	30,316	38,426	58,218
Total assets	1,281,231	1,378,672	1,281,231	1,378,672	$ 1,278,389
Cash and cash equivalents	130,115	222,808	130,115	222,808	$ 147,336	$ 280,286
Mine Production [Member] | Business Segments [Member]
Segment Reporting Information [Line Items]
Revenues	106,395	118,968	192,197	244,706
Depletion, depreciation and amortization	20,517	16,942	37,586	33,811
General and administrative expenses	0	0	0	0
Interest income	0	0	0	0
Interest expense	0	0	0	0
Income (loss) before impairment charge and income tax provision		21,394		50,222
Impairment charge		0		0
INCOME (LOSS) BEFORE INCOME TAX BENEFIT (PROVISION)	10,288	21,394	11,579	50,222
Capital expenditures	19,418	27,161	37,895	52,709
Total assets	626,078	612,486	626,078	612,486
PGM Recycling [Member] | Business Segments [Member]
Segment Reporting Information [Line Items]
Revenues	59,188	66,316	106,924	140,998
Depletion, depreciation and amortization	194	256	385	508
General and administrative expenses	0	0	0	0
Interest income	466	416	759	818
Interest expense	0	0	0	0
Income (loss) before impairment charge and income tax provision		2,036		4,163
Impairment charge		0		0
INCOME (LOSS) BEFORE INCOME TAX BENEFIT (PROVISION)	2,971	2,036	4,764	4,163
Capital expenditures	0	104	10	164
Total assets	66,013	68,927	66,013	68,927
Canadian Properties [Member] | Business Segments [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Depletion, depreciation and amortization	0	0	0	0
General and administrative expenses	203	280	339	515
Interest income	1	2	1	6
Interest expense	0	0	0	0
Income (loss) before impairment charge and income tax provision		(354)		(787)
Impairment charge		46,772		46,772
INCOME (LOSS) BEFORE INCOME TAX BENEFIT (PROVISION)	(219)	(47,126)	(387)	(47,559)
Capital expenditures	0	0	0	0
Total assets	25,953	27,735	25,953	27,735
Cash and cash equivalents		17,800		17,800
South American Properties [Member] | Business Segments [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Depletion, depreciation and amortization	0	0	0	0
General and administrative expenses	375	172	683	354
Interest income	0	5	1	19
Interest expense	0	0	0	0
Income (loss) before impairment charge and income tax provision		(104)		(877)
Impairment charge		0		0
INCOME (LOSS) BEFORE INCOME TAX BENEFIT (PROVISION)	(1,385)	(104)	(2,628)	(877)
Capital expenditures	0	46	0	46
Total assets	103,586	105,058	103,586	105,058
All Other [Member] | Business Segments [Member]
Segment Reporting Information [Line Items]
Revenues	100	100	200	200
Depletion, depreciation and amortization	0	0	0	0
General and administrative expenses	7,733	9,944	15,586	17,872
Interest income	493	301	909	583
Interest expense	4,067	5,312	8,249	10,616
Income (loss) before impairment charge and income tax provision		(14,838)		(27,743)
Impairment charge		0		0
INCOME (LOSS) BEFORE INCOME TAX BENEFIT (PROVISION)	(11,086)	(14,838)	(23,250)	(27,743)
Capital expenditures	166	3,005	521	5,299
Total assets	$ 459,601	$ 564,466	$ 459,601	$ 564,466

Investments (Narrative) (Detail

Investments (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Investments reserved as collateral on undrawn letters of credit	$ 18,500,000		$ 18,500,000		$ 18,500,000
Gain on sale of long term investment	482,000	$ 0	482,000	$ 0
Impairment of investments (less than for 2015)	0	$ 100,000	0	$ 100,000
Other Noncurrent Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Long-term investments	100,000		100,000		500,000
Letter of Credit [Member]
Schedule of Available-for-sale Securities [Line Items]
Undrawn letters of credit	$ 17,500,000		$ 17,500,000		$ 17,500,000

Investments (Schedule of Availa

Investments (Schedule of Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 312,489	$ 317,488
Gross unrealized gains	572	261
Gross unrealized losses	(46)	(577)
Fair value	313,015	317,172
Subtotal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	311,785	317,006
Gross unrealized gains	298	0
Gross unrealized losses	(46)	(577)
Fair value	312,037	316,429
Federal agency notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	279,850	285,276
Gross unrealized gains	259	0
Gross unrealized losses	(46)	(519)
Fair value	280,063	284,757
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	31,935	31,730
Gross unrealized gains	39	0
Gross unrealized losses	0	(58)
Fair value	31,974	31,672
Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	704	482
Gross unrealized gains	274	261
Gross unrealized losses	0	0
Fair value	$ 978	$ 743

Investments (Schedule of Maturi

Investments (Schedule of Maturities of Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 312,489	$ 317,488
Fair value	313,015	317,172
Federal agency notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost, due in one year or less	214,745
Fair value, due in one year or less	214,821
Amortized cost, due after year one through two years	65,105
Fair value, due after year one through two years	65,242
Amortized cost	279,850	285,276
Fair value	280,063	284,757
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost, due in one year or less	16,485
Fair value, due in one year or less	16,488
Amortized cost, due after year one through two years	15,450
Fair value, due after year one through two years	15,486
Amortized cost	31,935	31,730
Fair value	$ 31,974	$ 31,672

Inventories (Components Of Inve

Inventories (Components Of Inventories) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Metals inventory
Raw ore	$ 4,123	$ 4,234
Concentrate and in-process	58,176	43,727
Finished goods	32,177	32,618
Total metals inventory	94,476	80,579
Materials and supplies	19,416	21,493
Total inventories	$ 113,892	$ 102,072

Earnings Per Share (Reconciliat

Earnings Per Share (Reconciliation of Computation of Basic and Diluted Shares and the Related Impact on Income) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Basic EPS
Net income attributable to common stockholders	$ 784	$ (27,476)	$ (9,146)	$ (4,474)
Basic EPS, Weighted Average Shares (Denominator) (in shares)	121,074	120,751	121,065	120,637
Basic EPS, Per Share Amount (in usd per share)	$ 0.01	$ (0.23)	$ (0.08)	$ (0.04)
Effect of Dilutive Securities
Stock options (in shares)	1
Nonvested shares (in shares)	72
Contingently issuable shares (in shares)	233
Diluted EPS
Net income attributable to common stockholders	$ 784
Diluted EPS, Weighted Average Shares (Denominator) (in shares)	121,380	120,751	121,065	120,637
Diluted EPS, Per Share Amount (in usd per share)	$ 0.01	$ (0.23)	$ (0.08)	$ (0.04)

Earnings Per Share (Anti-diluti

Earnings Per Share (Anti-dilutive Shares Excluded From Calculation of Diluted Earnings Per Share) (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Oct. 31, 2012
Stock options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings per share	0	6	1	7
Nonvested shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings per share	8	26	136	61
Contingently issuable [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings per share	159	143	328	136
1.875% Convertible Debentures [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate	1.875%	1.875%	1.875%	1.875%	1.875%
1.875% Convertible Debentures [Member] | Convertible debentures [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings per share	22	95	22	95
1.75% Convertible Debentures [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate	1.75%	1.75%	1.75%	1.75%	1.75%	1.75%
1.75% Convertible Debentures [Member] | Convertible debentures [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings per share	30,413	36,003	30,413	36,003

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details)	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Oct. 31, 2012
1.875% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	1.875%	1.875%	1.875%
1.75% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	1.75%	1.75%	1.75%	1.75%

Fair Value Measurements (Financ

Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 312,037	$ 316,429
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund	60,754	54,761
Mutual funds	978	743
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund	60,754	54,761
Mutual funds	978	743
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund	0	0
Mutual funds	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund	0	0
Mutual funds	0	0
Fair Value, Measurements, Recurring [Member] | Federal Agency Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	280,063	284,757
Fair Value, Measurements, Recurring [Member] | Federal Agency Notes [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Federal Agency Notes [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	280,063	284,757
Fair Value, Measurements, Recurring [Member] | Federal Agency Notes [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Commercial paper [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	31,974	31,672
Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	31,974	31,672
Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 0	$ 0

Fair Value Measurements (Fina58

Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Nonrecurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Oct. 31, 2012
1.875% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	1.875%	1.875%	1.875%
1.75% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Stated interest rate	1.75%	1.75%	1.75%	1.75%
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term investments		$ 524
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term investments		524
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term investments		0
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term investments		0
Fair Value, Measurements, Nonrecurring [Member] | 1.875% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	$ 524	524
Fair Value, Measurements, Nonrecurring [Member] | 1.875% Convertible Debentures [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | 1.875% Convertible Debentures [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	524	524
Fair Value, Measurements, Nonrecurring [Member] | 1.875% Convertible Debentures [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | 1.75% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	307,369	285,446
Fair Value, Measurements, Nonrecurring [Member] | 1.75% Convertible Debentures [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | 1.75% Convertible Debentures [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	307,369	285,446
Fair Value, Measurements, Nonrecurring [Member] | 1.75% Convertible Debentures [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	$ 0	$ 0

Related Parties (Narrative) (De

Related Parties (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners			25.00%
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Revenue from related parties	$ 7.6	$ 23.5