Stillwater Mining (SWC) 10-Q 30 Oct 15 2015 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Oct. 29, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
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		120,996,146

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive (Loss) Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
REVENUES
Mine Production	$ 86,359	$ 137,067	$ 331,065	$ 409,967
PGM Recycling	81,982	109,509	222,980	305,760
Other	100	5,490	300	5,725
Total revenues	168,441	252,066	554,345	721,452
Costs of metals sold
Mine Production	69,004	85,240	229,676	252,730
PGM Recycling	78,928	106,801	216,074	297,773
Other	0	5,278	0	5,357
Total costs of metals sold (excludes depletion, depreciation and amortization)	147,932	197,319	445,750	555,860
Depletion, depreciation and amortization
Mine Production	15,132	16,923	48,943	49,373
PGM Recycling	230	258	738	761
Total depletion, depreciation and amortization	15,362	17,181	49,681	50,134
Total costs of revenues	163,294	214,500	495,431	605,994
Exploration	827	659	2,667	2,379
Reorganization	1,658	0	1,658	6,045
General and administrative	8,911	10,051	27,652	28,017
Loss on long-term investments	151	59	204	59
Impairment of non-producing mineral properties	0	0	46,772	0
(Gain) loss on disposal of property, plant and equipment	(219)	39	(216)	(262)
Total costs and expenses	174,622	225,308	574,168	642,232
OPERATING (LOSS) INCOME	(6,181)	26,758	(19,823)	79,220
OTHER INCOME (EXPENSE)
Other	17	785	918	849
Loss on extinguishment of debt, net	(4,010)	0	(4,010)	0
Interest income	766	931	2,192	2,750
Interest expense	(5,097)	(6,018)	(15,713)	(17,737)
Foreign currency transaction gain, net	12	998	149	5,359
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)	(14,493)	23,454	(36,287)	70,441
Income tax benefit (provision)	2,464	(5,619)	8,127	(15,909)
NET (LOSS) INCOME	(12,029)	17,835	(28,160)	54,532
Net loss attributable to noncontrolling interest	(151)	(313)	(11,808)	(1,083)
NET (LOSS) INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS	(11,878)	18,148	(16,352)	55,615
Other comprehensive (loss) income, net of tax
Net unrealized (loss) / gain on investments available-for-sale	(34)	(183)	149	(42)
COMPREHENSIVE (LOSS) INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS	(11,912)	17,965	(16,203)	55,573
Comprehensive loss attributable to noncontrolling interest	(151)	(313)	(11,808)	(1,083)
TOTAL COMPREHENSIVE (LOSS) INCOME	$ (12,063)	$ 17,652	$ (28,011)	$ 54,490
Weighted average common shares outstanding
Basic (in shares)	120,960	120,067	120,746	119,849
Diluted (in shares)	120,960	156,391	120,746	156,045
Basic (loss) earnings per share attributable to common stockholders (in usd per share)	$ (0.10)	$ 0.15	$ (0.14)	$ 0.46
Diluted (loss) earnings per share attributable to common stockholders (in usd per share)	$ (0.10)	$ 0.14	$ (0.14)	$ 0.43

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 133,956	$ 280,286
Investments, at fair value	326,344	251,254
Inventories	126,963	130,307
Trade receivables	723	1,277
Deferred income taxes	16,642	21,055
Prepaid expenses	4,220	2,546
Other current assets	21,744	14,671
Total current assets	630,592	701,396
Mineral properties	112,480	159,252
Mine development, net	452,110	409,754
Property, plant and equipment, net	112,827	118,881
Deferred debt issuance costs	4,367	6,032
Other noncurrent assets	4,811	4,012
Total assets	1,317,187	1,399,327
Current liabilities
Accounts payable	25,850	26,806
Accrued compensation and benefits	29,911	29,973
Property, production and franchise taxes payable	13,890	15,828
Current portion of long-term debt and capital lease obligations	1,185	2,144
Other current liabilities	6,625	7,288
Total current liabilities	77,461	82,039
Long-term debt and capital lease obligations	254,684	294,023
Deferred income taxes	48,907	68,896
Accrued workers compensation	6,092	6,060
Asset retirement obligation	10,805	9,401
Other noncurrent liabilities	9,307	7,200
Total liabilities	407,256	467,619
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; issued and outstanding 120,995,912 and 120,381,746 at September 30, 2015 and December 31, 2014, respectively	1,210	1,204
Paid-in capital	1,097,374	1,091,146
Accumulated deficit	(195,491)	(179,139)
Accumulated other comprehensive income	166	17
Total stockholders’ equity	903,259	913,228
Noncontrolling interest	6,672	18,480
Total equity	909,931	931,708
Total liabilities and equity	$ 1,317,187	$ 1,399,327

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2015	Dec. 31, 2014
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)	120,995,912	120,381,746
Common stock, shares outstanding (in shares)	120,995,912	120,381,746

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net (loss) income	$ (28,160)	$ 54,532
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depletion, depreciation and amortization	49,681	50,134
Loss on long-term investments	204	59
Loss on extinguishment of debt, net	4,010	0
Impairment of non-producing mineral properties	46,772	0
Amortization/accretion on investment premium/discount	1,688	1,441
Gain on disposal of property, plant and equipment	(216)	(262)
Foreign currency transaction gain, net	(149)	(5,359)
Deferred income taxes	(12,192)	(3,229)
Accretion of asset retirement obligation	589	554
Amortization of deferred debt issuance costs	1,665	1,929
Accretion of convertible debenture debt discount	12,985	12,746
Share based compensation and other benefits	9,489	10,238
Non-cash capitalized interest	(2,809)	(2,381)
Changes in operating assets and liabilities:
Inventories	2,280	2,657
Trade receivables	554	7,744
Prepaid expenses	(1,674)	(564)
Accrued compensation and benefits	(62)	(986)
Accounts payable	413	(7,088)
Property, production and franchise taxes payable	170	3,102
Income taxes payable	0	788
Accrued workers compensation	32	136
Other operating assets	(7,607)	559
Other operating liabilities	(1,982)	4,943
NET CASH PROVIDED BY OPERATING ACTIVITIES	75,681	131,693
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(83,386)	(87,038)
Proceeds from disposal of property, plant and equipment	387	323
Purchases of investments	(230,392)	(174,941)
Proceeds from maturities of investments	153,902	131,441
NET CASH USED IN INVESTING ACTIVITIES	(159,489)	(130,215)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments on debt and capital lease obligations	(62,582)	(31,536)
Proceeds from issuance of common stock	60	988
NET CASH USED IN FINANCING ACTIVITIES	(62,522)	(30,548)
CASH AND CASH EQUIVALENTS
Net decrease	(146,330)	(29,070)
Balance at beginning of period	280,286	286,687
BALANCE AT END OF PERIOD	$ 133,956	$ 257,617

General

General	9 Months Ended
	Sep. 30, 2015
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 present fairly the financial position of Stillwater Mining Company (the “Company”) at September 30, 2015 , and the results of its operations and cash flows for the nine -month periods ended September 30, 2015 and 2014 , respectively. The results of operations for the first nine months of 2015 are not necessarily indicative of the results to be expected for the 2015 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 2014 Annual Report on Form 10-K (Form 10-K). All intercompany 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 (U. S. 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. The Company reclassified Marketing expenses into General and administrative for the period ended September 30, 2014, to be consistent with the current presentation in the Company's Consolidated Statements of Comprehensive (Loss) Income .

Sales

Sales	9 Months Ended
	Sep. 30, 2015
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 several 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. Sales of copper and nickel by-products typically reflect a discount from market prices. By-product sales (gold, nickel, mined rhodium, copper and silver) are included in revenues from Mine Production. During each of the three-month periods ended September 30, 2015 and 2014 , total by-product sales were $5.0 million and $6.9 million , respectively. For the nine-month periods ended September 30, 2015 and 2014 , by-product sales totaled $18.7 million and $22.2 million , respectively. In July 2014, the Company executed five -year supply and refining agreements with Johnson Matthey. Under the terms of these agreements, Johnson Matthey has an exclusive five -year right to refine all of the PGM filter cake the Company produces at its Columbus, Montana facilities. Johnson Matthey 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 Johnson Matthey 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 Johnson Matthey 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 Johnson Matthey 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 four years . In accordance with the terms of the Johnson Matthey PGM supply agreement, for the nine-month period ended September 30, 2015 , all Company sales of mined PGMs, other than the platinum sales under the Company's sales agreement with Tiffany & Co., were to Johnson Matthey. In the first half of 2014, all Company sales of mined PGMs were either in the spot market or under mutually agreed short-term (one year or less) supply agreements. 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 as currently structured, 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 facility in Columbus, Montana. These advances are included in Other current assets on the Company’s Consolidated Balance Sheets until such time as the material has 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, processes it for a fee and returns the recovered metals to the supplier. OTHER Periodically, the Company acquires PGMs in the open market for resale to third parties. The Company recognized no revenues from PGMs acquired in the open market and simultaneously resold to third parties during the quarter ended September 30, 2015. However, the Company recognized $5.3 million of revenues from PGMs during the same period in 2014. This revenue is shown as Other revenues and the associated acquisition cost is shown as Other costs of metals sold in the Consolidated Statements of Comprehensive (Loss) Income . TOTAL SALES Total sales to significant customers as a percentage of total revenues for the three- and nine -month periods ended September 30, 2015 and 2014 were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2015 (1) 2014 2015 (1) 2014 (1) Customer A 70 % 67 % 75 % 45 % Customer B — 10 % — 16 % 70 % 77 % 75 % 61 % (1) The “—” symbol represents less than 10% of total revenues.

Asset Impairment

Asset Impairment	9 Months Ended
	Sep. 30, 2015
Asset Impairment Charges [Abstract]
Asset Impairment	ASSET IMPAIRMENT In accordance with the Financial Accounting Standards Board (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. In the third quarter of 2015, the Company recorded an increase of $1.1 million in estimated reclamation costs at the Stillwater Mine, related to the Benbow portal. As a result of inquiries relating to the Marathon project received 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. During the second quarter of 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 . The Company determined at December 31, 2014, that certain real estate properties owned by the Company in the town of Marathon that previously were associated with the Marathon project should be segregated and considered separately for impairment. The Company obtained an estimate of fair value from a real estate firm in the Marathon area and impaired those properties by approximately $0.5 million at December 31, 2014.

Noncontrolling Interest

Noncontrolling Interest	9 Months Ended
	Sep. 30, 2015
Noncontrolling Interest [Abstract]
Noncontrolling Interest	NONCONTROLLING INTEREST In 2012, the Company entered into an agreement with Mitsubishi Corporation (Mitsubishi) in which a Mitsubishi subsidiary acquired a 25% interest in the Company's then wholly-owned subsidiary, Stillwater Canada Inc (SCI) which held the Marathon PGM-copper project and related properties, for $81.25 million in cash. Mitsubishi also contributed an additional $13.6 million to satisfy its portion of the venture's initial cash call. The agreement provides that Mitsubishi is responsible for funding 25% of the operating, capital and exploration expenditures on the Marathon properties and will cooperate and support efforts to secure financing for Marathon. Under a related supply agreement, Mitsubishi also will have an option to purchase up to 100% of any future Marathon PGM production at a discount to market. The change in the Company's equity as a result of the sale of the noncontrolling interest in SCI was an increase to Paid-in capital of $42.5 million , offset in part by expenses incurred of $1.1 million . Mitsubishi's 25% interest in the SCI net loss in each period is shown as Net loss attributable to noncontrolling interest in the Company's Consolidated Statements of Comprehensive (Loss) Income . The amount of this loss is 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-months ended September 30, 2015 and 2014 was $0.2 million and $0.3 million , respectively, and $11.8 million and $1.1 million , for the nine-months ended September 30, 2015 and 2014, respectively. Mitsubishi's share of the equity in SCI is reflected as Noncontrolling interest in the Company's Consolidated Balance Sheets and totaled $6.7 million and $18.5 million at September 30, 2015 and December 31, 2014, respectively. The noncontrolling interest balance at September 30, 2015 reflects Mitsubishi's share of the impairment loss taken during the second quarter of 2015 on the carrying value of the Marathon mineral properties. The noncontrolling interest portion of the impairment loss was $11.7 million (net of tax). In the third quarter of 2015, the Company entered into an agreement with Mitsubishi to purchase Mitsubishi's 25% interest in SCI and related properties for a total cash consideration of $5.2 million . The total cash consideration is comprised of $1.0 million in cash and the equivalent of 25% of the total cash and cash equivalents held by SCI at October 16, 2015. The transaction closed subsequent to the end of the third quarter on October 26, 2015.

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2015
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 relating to PGM recycling of catalyst 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 derivative accounting treatment and so has elected to account for these transactions as normal purchases and normal sales. All of the Company's fixed forward sales contracts open at September 30, 2015 , will settle at various periods through March 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 prices by a predetermined margin limit. At September 30, 2015 , and December 31, 2014, 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 September 30, 2015 : PGM Recycling: Fixed Forward Contracts Platinum Palladium Rhodium Settlement Period Ounces Average Price/Ounce Ounces Average Price/Ounce Ounces Average Price/Ounce Fourth Quarter 2015 34,967 $ 1,003 49,347 $ 630 6,194 $ 841 First Quarter 2016 3,247 $ 968 4,632 $ 607 1,195 $ 764

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION 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's current practice is to issue cash awards and / or restricted stock units as incentive compensation to employees and non-employee directors. The Company continues to have previously issued stock options that remain outstanding under the General Employee Plan and the 2004 Equity Incentive Plan. In April 2012, stockholders approved the 2012 Equity Incentive Plan. Approximately 11.6 million shares of common stock were originally authorized under the Plans, including approximately 5.0 million , 5.2 million , and 1.4 million shares authorized under the 2012 Equity Incentive Plan, 2004 Equity Incentive Plan and the General Employee Plan, respectively. Approximately 4.4 million shares were available and reserved for issuance under the 2012 Equity Incentive Plan at September 30, 2015 . 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. Employees’ restricted stock units typically vest in equal annual installments over a three -year period after date of grant. Stock options expire ten years after the date of grant. NONVESTED SHARES Time-Based Restricted Stock Unit (RSU) Awards Time-based RSU 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 RSUs unless otherwise determined by the Board, nor any dividends on stock that may be delivered in settlement of the RSUs unless and until the stock is issued in settlement of the RSUs. Nonvested time-based RSU activity during the first nine months of 2015 , is detailed in the following table: Nonvested Shares Weighted-Average Grant-Date Fair Value Nonvested time-based RSUs at January 1, 2015 184,747 $ 13.80 Granted 120,715 14.29 Vested (35,030 ) 13.75 Forfeited (4,480 ) 13.91 Nonvested time-based RSUs at March 31, 2015 265,952 $ 14.03 Granted 3,668 13.88 Vested (1,586 ) 14.63 Forfeited (66 ) 13.11 Nonvested time-based shares at June 30, 2015 267,968 $ 14.02 Granted 1,480 10.02 Vested (1,509 ) 14.15 Forfeited (6,624 ) 14.35 Nonvested time-based shares at September 30, 2015 261,315 $ 13.99 Total compensation expense related to grants of nonvested time-based RSUs was $0.4 million in each of the three-month periods ended September 30, 2015 and 2014 , and $1.2 million and $1.4 million , for the nine-month periods ended September 30, 2015 and 2014 , respectively. Compensation expense is recorded in General and administrative in the Company's Consolidated Statements of Comprehensive (Loss) Income . Performance-Based Restricted Stock Unit Awards A performance-based RSU 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 that 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. The Company has granted performance-based RSU awards under the Plans. The payouts of the awards are dependent upon three distinct components with five separate sub-targets. Two of the sub-targets are market-based and equity classified; one sub-target is market-based and liability classified; and two sub-targets are performance-based and equity classified. 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-target is remeasured each reporting period. The existence of a market condition requires recognition of compensation cost for the performance RSU 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 (Loss) Income , related to grants of performance-based RSUs for the three-month periods ended September 30, 2015 and 2014 was $0.3 million and $0.2 million , respectively, and for the nine-month periods ended September 30, 2015 and 2014 , was $1.0 million and $0.8 million , respectively. Performance-based RSU awards are not entitled to any dividend equivalents with respect to the RSUs unless otherwise determined by the Board, nor any dividends on stock that may be delivered in settlement of the RSUs unless and until the stock is issued in settlement of the RSUs. Nonvested performance-based RSU activity during the first nine months of 2015 is detailed in the following table: Nonvested Shares Weighted-Average Grant-Date Fair Value Nonvested performance-based RSUs at January 1, 2015 214,236 $ 15.69 Granted * 170,078 14.92 Vested — Forfeited * (2,071 ) 15.34 Nonvested performance-based RSUs at March 31, 2015 382,243 $ 15.35 No activity — Nonvested performance-based RSUs at June 30, 2015 382,243 $ 15.35 Forfeited (2,966 ) $ 15.34 Nonvested performance-based RSUs at September 30, 2015 379,277 $ 12.28 * The number of performance-based RSUs granted and forfeited is based on the target award amounts in the related performance-based RSU grant agreements. The following table presents the compensation expense of the nonvested RSUs outstanding at September 30, 2015 , to be recognized over the remaining vesting periods: (In thousands) Time-based shares Performance -based shares Remaining 2015 $ 426 $ 384 2016 1,516 1,536 2017 628 824 2018 8 — Total $ 2,578 $ 2,744

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2015
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. At September 30, 2015 , the Company has approximately $104.8 million of regular federal tax net operating loss carryforwards in the U.S. expiring from 2020 through 2028. Usage of $80.9 million of these net operating losses is limited to approximately $10.2 million annually as a result of the change in control of the Company that occurred in connection with the Norilsk Nickel transaction in 2003. The Company has $31.6 million of alternative minimum tax credit carryforwards which will not expire and $1.6 million in general business credits expiring during 2029 to 2034. The Company has approximately $3.3 million of state tax net operating loss carryforwards expiring during 2020 through 2029. The Company also has $51.6 million of foreign net operating loss carryforwards. The foreign net operating losses expire as follows: $18.1 million during 2016 to 2019 and $25.4 million during 2024 to 2035. Currently, $8.1 million of foreign net operating losses have an indefinite life. 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 2015 and 2014 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 provision for income taxes for the three- and nine-month periods ended September 30, 2015 consists of U.S. Federal income tax, state tax, as well as deferred tax benefits from certain foreign jurisdictions. 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 / (provision) for the three-month periods ended September 30, 2015 and 2014, of $2.5 million and $(5.6) million , respectively. The Company recognized an income tax benefit / (provision) for the nine-month periods ended September 30, 2015 and 2014, of $8.1 million and $(15.9) million , respectively. The partial restructure of internal operations and the creation of a separate metal sales and trading subsidiary is primarily responsible for a discrete income tax benefit of $10.6 million recognized for the nine-month period ending September 30, 2015 . Of this discrete income tax benefit, $8.3 million is associated with the partial restructure results from a re-measuring of the Company’s deferred state tax associated with deferred tax assets and liabilities from a blended deferred rate of 10.6% at December 31, 2014 to 4.0% at September 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 (Loss) Income . The Company does not have any uncertain benefits at September 30, 2015 . There were no interest or penalties accrued at September 30, 2015 and for the comparable period in 2014, interest and penalties accrued were $0.8 million . The Company made income tax payments of $13.1 million and $14.2 million in the nine-month periods ended September 30, 2015 and 2014 , respectively. Tax years still open for examination by the taxing authorities are the years ended December 31, 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	9 Months Ended
	Sep. 30, 2015
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 U.S. 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 . Net proceeds of $384.3 million from the offering were used in part to retire $164.3 million of the Company's 1.875% convertible debentures upon their redemption in March 2013 with the remainder being used for general corporate purposes. In the third quarter of 2015, the Company repurchased $61.6 million of the outstanding principal of the 1.75% debentures, due 2032, paying cash of $59.4 million . The Company reduced the debt component by $50.7 million , which includes 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, recorded in Loss on extinguishment of debt, net in the Company's Consolidated Statements of Comprehensive (Loss) Income . 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 September 30, 2015 and December 31, 2014 , was approximately $254.2 million and $291.1 million , respectively, which is net of unamortized discount of $81.0 million and $105.6 million , respectively. 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. The outstanding balance at September 30, 2015 and December 31, 2014 , of $0.5 million aggregate principal amount, is reported as a long-term debt obligation. In the third quarter of 2015, the Company repurchased $1.7 million of the outstanding principal of the 1.875% debentures, due 2028, paying cash of $1.6 million and recording a gain of approximately $0.1 million , recorded in Loss on extinguishment of debt, net the Company's Consolidated Statements of Comprehensive (Loss) Income . 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 . Borrowings under this working capital credit facility are limited to a borrowing base equal to the sum of 85% of eligible accounts receivable and 70% of eligible inventories. Terms of the credit agreement state that the borrowings will be secured by the Company's accounts receivable, metals inventories and other accounts. The asset-backed revolving credit facility includes a single fixed-charge coverage covenant that only takes effect when less than 30% of the total borrowing capacity under the facility remains available. The facility includes a $60.0 million letter of credit sub-facility. Outstanding borrowings under the facility accrue interest at a spread over the London Interbank Offer Rate that varies from 2.25% to 2.75% , decreasing progressively as the percentage drawn under the facility increases. The Company also pays a commitment fee on committed but un-utilized borrowing capacity available under the facility at a rate per annum of 0.375% or 0.5% , depending on the amount of the facility drawn. At September 30, 2015 and 2014 , there were no outstanding borrowings under this revolving credit facility, and approximately $17.5 million in undrawn irrevocable letters of credit had been issued under this facility as collateral for sureties, which reduce the amount available for borrowing under the facility on a dollar-for-dollar basis. 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 nine -month periods ended September 30, 2015 and 2014: Three months ended Nine months ended September 30, September 30, (In thousands) 2015 2014 2015 2014 1.75% Convertible Debentures Amortization of debt issuance costs $ 240 $ 287 $ 714 $ 852 Interest expense $ 6,262 $ 6,074 $ 18,860 $ 17,931 Cash payments for interest $ 423 $ — $ 3,894 $ 3,472 1.875% Convertible Debentures Interest expense $ 9 $ 11 $ 30 $ 32 Cash payments for interest $ 21 $ 21 $ 42 $ 42 Asset-Backed Revolving Credit Facility Amortization of debt issuance costs $ 69 $ 69 $ 204 $ 204 Fees $ 253 $ 260 $ 839 $ 765 The Company's total current and long-term debt balances at September 30, 2015 and December 31, 2014 were as follows: September 30, 2015 December 31, 2014 (In thousands) Current Long-Term Current Long-Term 1.75% Convertible Debentures Aggregate principal $ — $ 335,150 $ — $ 396,750 Debt discount — (80,990 ) — (105,634 ) Debt balance — 254,160 — 291,116 1.875% Convertible Debentures — 524 — 2,245 Capital Lease Obligation 1,107 — 2,067 580 Small Land Purchase 78 — 77 82 Total debt balances $ 1,185 $ 254,684 $ 2,144 $ 294,023 EXEMPT FACILITY REVENUE BONDS During 2000, the Company completed a $30.0 million offering of 8.0% Exempt Facility Revenue Bonds, Series 2000. These bonds were issued by the State of Montana Board of Investments to finance a portion of the costs of constructing and equipping certain sewage and solid waste disposal facilities at both the Stillwater Mine and the East Boulder Mine. The bonds were scheduled to mature on July 1, 2020, and had a stated interest rate of 8.0% per annum with interest paid semi-annually. Net discounted proceeds from the offering were $28.7 million , yielding an effective rate of 8.57% . In July 2014, the Company redeemed the entire $30.0 million of 8.0% Exempt Facility Revenue Bonds, Series 2000, which included the payment of accrued and unpaid interest of $40,000 . CAPITAL LEASE OBLIGATIONS The Company is party to a lease agreement with General Electric Capital Corporation covering the acquisition of a tunnel-boring machine (TBM) for use on the Blitz development adjacent to the Stillwater Mine. The transaction is structured as a capital lease with a four -year term maturing in 2016; lease payments are due quarterly in advance. The Company made cash payments of $0.5 million on its capital lease obligations in each of the three-month periods ended September 30, 2015 and 2014 , respectively, and cash payments of $1.6 million on its capital lease obligations in each of the nine -month periods ended September 30, 2015 and 2014 , respectively. The cash payments in each of the three- and nine -month periods ended September 30, 2015 and 2014 , included interest of less than $0.1 million . At September 30, 2015 , and December 31, 2014 , the outstanding balance under the capital lease was $1.1 million and $2.6 million , respectively. The following is a schedule by year of the future minimum lease payments for the capital lease together with the present value of the net minimum lease payments: (In thousands) 2015 $ 542 2016 589 Total minimum lease payments 1,131 Interest at rates ranging from 5.21% to 5.46% (before-tax) (24 ) Net minimum lease payments $ 1,107 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-month periods ended September 30, 2015 and 2014 , the Company capitalized interest of $1.5 million and $1.4 million , respectively. For the nine -month periods ended September 30, 2015 and 2014 , the Company capitalized interest of $4.2 million and $3.6 million , respectively. Capitalized interest is recorded as a reduction to Interest expense in the Company's Consolidated Statements of Comprehensive (Loss) Income .

Mineral Properties and Mine Dev

Mineral Properties and Mine Development	9 Months Ended
	Sep. 30, 2015
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: September 30, December 31, (In thousands) 2015 2014 Mineral Properties: Montana, United States of America Stillwater Mine $ 1,950 $ 1,950 Ontario, Canada Marathon properties 8,560 55,332 San Juan, Argentina Altar property 101,970 101,970 Mine Development: Montana, United States of America Stillwater Mine 681,443 616,872 East Boulder Mine 216,232 204,483 1,010,155 980,607 Accumulated depletion and amortization (445,565 ) (411,601 ) Total mineral properties and mine development, net $ 564,590 $ 569,006

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2015
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: September 30, December 31, (In thousands) 2015 2014 Machinery and equipment $ 159,792 $ 152,421 Buildings and structural components 173,265 169,609 Land 11,740 9,488 Construction-in-progress: Stillwater Mine 953 2,633 East Boulder Mine 569 1,539 Marathon 148 148 Processing facilities and other 1,918 1,994 348,385 337,832 Accumulated depreciation (235,558 ) (218,951 ) Total property, plant, and equipment, net $ 112,827 $ 118,881 The Company's total capital expenditures for mine development and property, plant and equipment for the nine -month periods ended September 30, 2015 and 2014 were as follows: September 30, September 30, (In thousands) 2015 2014 Stillwater Mine $ 70,172 $ 69,513 East Boulder Mine 13,548 21,189 Other 4,599 2,993 Total U.S. capital expenditures 88,319 93,695 Foreign capital expenditures 46 2 Non-cash capitalized interest / depreciation (6,756 ) (6,228 ) Change in accounts payables for capital expenditures 1,777 (431 ) Cash capital spend for the period $ 83,386 $ 87,038

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2015
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 sells PGMs from mine production under short-term and long-term sales agreements. The financial results for the Stillwater Mine and the East Boulder Mine have been consolidated, 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 the majority of 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 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 September 30, 2015 Mine Production PGM Recycling Canadian Properties * All Other Total Revenues $ 86,359 $ 81,982 $ — $ — $ 100 $ 168,441 Depletion, depreciation and amortization $ 15,132 $ 230 $ — $ — $ — $ 15,362 General and administrative expenses $ — $ — $ 275 $ 100 $ 8,536 $ 8,911 Interest income $ — $ 437 $ 1 $ 4 $ 324 $ 766 Interest expense $ — $ — $ — $ — $ 5,097 $ 5,097 Income (loss) before income taxes $ 2,224 $ 3,261 $ (577 ) $ (339 ) $ (19,062 ) $ (14,493 ) Capital expenditures $ 24,661 $ 57 $ — $ — $ 450 $ 25,168 Total assets $ 608,198 $ 3,390 $ 27,078 $ 104,265 $ 574,256 $ 1,317,187 * Total assets includes cash and cash equivalents of $17.1 million . (In thousands) South American Properties Three Months Ended September 30, 2014 Mine Production PGM Recycling Canadian Properties All Other Total Revenues $ 137,067 $ 109,509 $ — $ — $ 5,490 $ 252,066 Depletion, depreciation and amortization $ 16,923 $ 258 $ — $ — $ — $ 17,181 General and administrative expenses * $ — $ — $ 794 $ 17 $ 9,240 $ 10,051 Interest income $ — $ 681 $ 1 $ 13 $ 236 $ 931 Interest expense $ — $ — $ — $ — $ 6,018 $ 6,018 Income (loss) before income taxes $ 34,904 $ 3,131 $ (1,205 ) $ 748 $ (14,124 ) $ 23,454 Capital expenditures $ 32,604 $ 28 $ — $ 2 $ 624 $ 33,258 Total assets $ 584,538 $ 88,411 $ 76,678 $ 107,909 $ 526,923 $ 1,384,459 * The Company reclassified Marketing expenses into General and administrative for All Other for the three-month period ended September 30, 2014, for presentation purposes. (In thousands) South American Nine Months Ended September 30, 2015 Mine Production PGM Recycling Canadian Properties * All Other Total Revenues $ 331,065 $ 222,980 $ — $ — $ 300 $ 554,345 Depletion, depreciation and amortization $ 48,943 $ 738 $ — $ — $ — $ 49,681 General and administrative expenses $ — $ — $ 790 $ 454 $ 26,408 $ 27,652 Interest income $ — $ 1,256 $ 7 $ 23 $ 906 $ 2,192 Interest expense $ — $ — $ — $ — $ 15,713 $ 15,713 Income (loss) before impairment charge and income taxes $ 52,446 $ 7,424 $ (1,364 ) $ (1,216 ) $ (46,805 ) $ 10,485 Impairment charge $ — $ — $ 46,772 $ — $ — $ 46,772 Income (loss) after impairment charge, before income taxes $ 52,446 $ 7,424 $ (48,136 ) $ (1,216 ) $ (46,805 ) $ (36,287 ) Capital expenditures $ 77,370 $ 221 $ — $ 46 $ 5,749 $ 83,386 Total assets $ 608,198 $ 3,390 $ 27,078 $ 104,265 $ 574,256 $ 1,317,187 * Total assets includes cash and cash equivalents of $17.1 million . (In thousands) South American Nine Months Ended September 30, 2014 Mine Production PGM Recycling Canadian Properties All Other Total Revenues $ 409,967 $ 305,760 $ — $ — $ 5,725 $ 721,452 Depletion, depreciation and amortization $ 49,373 $ 761 $ — $ — $ — $ 50,134 General and administrative expenses * $ — $ — $ 2,783 $ 339 $ 24,895 $ 28,017 Interest income $ — $ 1,998 $ 3 $ 44 $ 705 $ 2,750 Interest expense $ — $ — $ — $ — $ 17,737 $ 17,737 Income (loss) before income taxes $ 107,864 $ 9,225 $ (3,843 ) $ 2,841 $ (45,646 ) $ 70,441 Capital expenditures $ 84,335 $ 155 $ — $ 2 $ 2,546 $ 87,038 Total assets $ 584,538 $ 88,411 $ 76,678 $ 107,909 $ 526,923 $ 1,384,459 * The Company reclassified Research and development and Marketing expenses into General and administrative for All Other for the nine-month period ended September 30, 2014, for presentation purposes.

Investments

Investments	9 Months Ended
	Sep. 30, 2015
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 (Loss) Income . At the time the securities are sold or otherwise disposed of, gross realized gains and losses are included in Net (loss) income . 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 nine -month periods ended September 30, 2015 and 2014 , were insignificant. All of the marketable securities amounts are available to satisfy current obligations. 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 September 30, 2015 , and December 31, 2014 were as follows: Investments (In thousands) Amortized cost Gross unrealized gains Gross unrealized losses Fair value 2015 Federal agency notes $ 286,220 $ 106 $ (34 ) $ 286,292 Commercial paper 40,097 — (45 ) 40,052 Mutual funds 419 205 — 624 Total $ 326,736 $ 311 $ (79 ) $ 326,968 2014 Federal agency notes $ 143,132 $ 40 $ (33 ) $ 143,139 Commercial paper 108,371 1 (257 ) 108,115 Mutual funds 344 279 — 623 Total $ 251,847 $ 320 $ (290 ) $ 251,877 The mutual funds included in the investment table above are included in Other noncurrent assets on the Company's Consolidated Balance Sheets . The maturities of available-for-sale securities at September 30, 2015 were as follows: (In thousands) Amortized cost Fair value Federal agency notes Due in one year or less $ 237,658 $ 237,764 Due after one year through two years 48,562 48,528 Total $ 286,220 $ 286,292 Commercial paper Due in one year or less $ 26,612 $ 26,567 Due after one year through two years 13,485 13,485 Total $ 40,097 $ 40,052 The Company has long-term investments in several Canadian junior exploration companies, recorded on the Company's Consolidated Balance Sheets at cost. The Company determined that certain of its long-term investments were other than temporarily impaired and recorded a loss of approximately $0.2 million for the three- and nine-month periods ended September 30, 2015 and 2014. These long-term investments totaled approximately $0.7 million at September 30, 2015 and $0.9 million at December 31, 2014, and are recorded in Other noncurrent assets on the Company's Consolidated Balance Sheets .

Inventories

Inventories	9 Months Ended
	Sep. 30, 2015
Inventory Disclosure [Abstract]
Inventories	INVENTORIES The Company carries items in its inventories at the lower of cost or market value. If 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 nine months of 2015 or 2014 . The costs of mined PGM 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: September 30, December 31, (In thousands) 2015 2014 Metals inventory Raw ore $ 4,215 $ 4,984 Concentrate and in-process 59,803 48,712 Finished goods 40,493 49,885 Total metals inventory 104,511 103,581 Materials and supplies 22,452 26,726 Total inventory $ 126,963 $ 130,307

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2015
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 during the three- and nine-month periods ended September 30, 2015, because the effect would have been anti-dilutive. There was no effect of outstanding nonvested shares on diluted weighted average shares outstanding for the three- and nine-month periods ended September 30, 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 shares that were excluded from the computation of diluted earnings per share, for the three- and nine-month periods ended September 30, 2015 and 2014: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2015 2014 2015 2014 Stock options 6 — 6 — Nonvested shares 44 — 50 — Contingently issuable 218 111 218 125 1.875% Convertible debentures, net of tax 22 — 22 — 1.75% Convertible debentures, net of tax 30,413 — 30,413 — In calculating earnings per share attributable to common stockholders for the three- and nine-month periods ended September 30, 2014 , reported consolidated net income attributable to common stockholders was adjusted for interest expense, net of capitalized interest (including amortization expense of deferred debt fees), a related income tax effect and the loss attributable to the noncontrolling interest in computing basic and diluted earnings per share attributable to common stockholders. Reconciliations showing the computation of basic and diluted shares and the related impact on income for the three - and nine-month periods ended September 30, 2014, are provided in the following table: Three Months Ended Nine Months Ended September 30, 2014 September 30, 2014 (In thousands, except per share amounts) Income (Numerator) Weighted Average Shares (Denominator) Per Share Amount Income (Numerator) Weighted Average Shares (Denominator) Per Share Amount Basic EPS Net income attributable to common stockholders $ 18,148 120,067 $ 0.15 $ 55,615 119,849 $ 0.46 Effect of Dilutive Securities Stock options — 6 — 31 Nonvested shares — 113 — 22 Contingently issuable shares — 107 — 45 1.875% Convertible debentures, net of tax — 95 — 95 1.75% Convertible debentures, net of tax 4,060 36,003 12,229 36,003 Diluted EPS Net income attributable to common stockholders and assumed conversions $ 22,208 156,391 $ 0.14 $ 67,844 156,045 $ 0.43

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2015
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 September 30, 2015 , and December 31, 2014 , consisted of the following: (In thousands) Fair Value Measurements At September 30, 2015 Total Level 1 Level 2 Level 3 Mutual funds $ 624 $ 624 $ — $ — Investments Federal agency notes $ 286,292 $ — $ 286,292 $ — Commercial paper $ 40,052 $ — $ 40,052 $ — (In thousands) Fair Value Measurements At December 31, 2014 Total Level 1 Level 2 Level 3 Mutual funds $ 623 $ 623 $ — $ — Investments Federal agency notes $ 143,139 $ — $ 143,139 $ — Commercial paper $ 108,115 $ — $ 108,115 $ — 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 balance of the money market funds at September 30, 2015 and December 31, 2014 , was $45.9 million and $120.0 million , respectively, and is classified as Level 1. The money market funds are recorded in Cash and cash equivalents 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 on the Company's Consolidated Balance Sheets . Assets and liabilities measured at fair value on a nonrecurring basis at September 30, 2015 , and December 31, 2014 , consisted of the following: (In thousands) Fair Value Measurements At September 30, 2015 Total Level 1 Level 2 Level 3 Marathon mineral properties $ 8,560 $ — $ — $ 8,560 1.875% Convertible debentures $ 524 $ — $ 524 $ — 1.75% Convertible debentures $ 302,684 $ — $ 302,684 $ — Long-term investments $ 692 $ — $ 692 $ — (In thousands) Fair Value Measurements At December 31, 2014 Total Level 1 Level 2 Level 3 Certain Marathon real estate properties $ 754 $ — $ — $ 754 1.875% Convertible debentures $ 2,245 $ — $ 2,245 $ — 1.75% Convertible debentures $ 303,108 $ — $ 303,108 $ — Long-term investments $ 896 $ — $ 896 $ — The Company determined in the second quarter of 2015, that the Marathon mineral properties owned by the Company in northern Ontario, Canada should be considered for impairment. The Company prepared an estimate of fair value and impaired those properties in the second quarter of 2015. An impairment charge of $46.8 million (before-tax) was taken on the Marathon mineral properties, reflecting an estimated fair value of $8.6 million . The Company used its current trading data to determine the fair value of its $0.5 million of outstanding 1.875% debentures. The Company determined the fair value of the liability component of its $335.15 million and $396.75 million of outstanding 1.75% debentures at September 30, 2015 and December 31, 2014 , respectively, by using observable market based information for debt instruments of similar amounts and duration. The Company determined at December 31, 2014, that certain real estate properties owned by the Company in the town of Marathon should be considered for impairment. The Company obtained an estimate of fair value and impaired those properties. The fair value of the Company's long-term investments in certain Canadian junior exploration companies at September 30, 2015 and December 31, 2014 , was based on market prices for similar assets.

Related Parties

Related Parties	9 Months Ended
	Sep. 30, 2015
Related Party Transactions [Abstract]
Related Parties	RELATED PARTIES At September 30, 2015, Mitsubishi Corporation owned a 25% interest in SCI, which owns Marathon and its related properties located in northern Ontario, Canada. The Company made PGM sales of $15.2 million and $24.9 million to Mitsubishi in the three-month periods ended September 30, 2015 and 2014 , respectively, and $38.7 million and $118.7 million , respectively, for the nine -month periods ended September 30, 2015 and 2014 , respectively.

General (Policies)

General (Policies)	9 Months Ended
	Sep. 30, 2015
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 (U. S. 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.
Reclassifications	The Company reclassified Marketing expenses into General and administrative for the period ended September 30, 2014, to be consistent with the current presentation in the Company's Consolidated Statements of Comprehensive (Loss) Income .

Sales (Tables)

Sales (Tables)	9 Months Ended
	Sep. 30, 2015
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 nine -month periods ended September 30, 2015 and 2014 were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2015 (1) 2014 2015 (1) 2014 (1) Customer A 70 % 67 % 75 % 45 % Customer B — 10 % — 16 % 70 % 77 % 75 % 61 % (1) The “—” symbol represents less than 10% of total revenues.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2015
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 September 30, 2015 : PGM Recycling: Fixed Forward Contracts Platinum Palladium Rhodium Settlement Period Ounces Average Price/Ounce Ounces Average Price/Ounce Ounces Average Price/Ounce Fourth Quarter 2015 34,967 $ 1,003 49,347 $ 630 6,194 $ 841 First Quarter 2016 3,247 $ 968 4,632 $ 607 1,195 $ 764

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Changes In The Company's Nonvested Shares	Nonvested time-based RSU activity during the first nine months of 2015 , is detailed in the following table: Nonvested Shares Weighted-Average Grant-Date Fair Value Nonvested time-based RSUs at January 1, 2015 184,747 $ 13.80 Granted 120,715 14.29 Vested (35,030 ) 13.75 Forfeited (4,480 ) 13.91 Nonvested time-based RSUs at March 31, 2015 265,952 $ 14.03 Granted 3,668 13.88 Vested (1,586 ) 14.63 Forfeited (66 ) 13.11 Nonvested time-based shares at June 30, 2015 267,968 $ 14.02 Granted 1,480 10.02 Vested (1,509 ) 14.15 Forfeited (6,624 ) 14.35 Nonvested time-based shares at September 30, 2015 261,315 $ 13.99 Nonvested performance-based RSU activity during the first nine months of 2015 is detailed in the following table: Nonvested Shares Weighted-Average Grant-Date Fair Value Nonvested performance-based RSUs at January 1, 2015 214,236 $ 15.69 Granted * 170,078 14.92 Vested — Forfeited * (2,071 ) 15.34 Nonvested performance-based RSUs at March 31, 2015 382,243 $ 15.35 No activity — Nonvested performance-based RSUs at June 30, 2015 382,243 $ 15.35 Forfeited (2,966 ) $ 15.34 Nonvested performance-based RSUs at September 30, 2015 379,277 $ 12.28 * The number of performance-based RSUs granted and forfeited is based on the target award amounts in the related performance-based RSU grant agreements.
Compensation Expense of Nonvested Shares	The following table presents the compensation expense of the nonvested RSUs outstanding at September 30, 2015 , to be recognized over the remaining vesting periods: (In thousands) Time-based shares Performance -based shares Remaining 2015 $ 426 $ 384 2016 1,516 1,536 2017 628 824 2018 8 — Total $ 2,578 $ 2,744

Debt and Capital Lease Obliga26

Debt and Capital Lease Obligations (Tables)	9 Months Ended
	Sep. 30, 2015
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 nine -month periods ended September 30, 2015 and 2014: Three months ended Nine months ended September 30, September 30, (In thousands) 2015 2014 2015 2014 1.75% Convertible Debentures Amortization of debt issuance costs $ 240 $ 287 $ 714 $ 852 Interest expense $ 6,262 $ 6,074 $ 18,860 $ 17,931 Cash payments for interest $ 423 $ — $ 3,894 $ 3,472 1.875% Convertible Debentures Interest expense $ 9 $ 11 $ 30 $ 32 Cash payments for interest $ 21 $ 21 $ 42 $ 42 Asset-Backed Revolving Credit Facility Amortization of debt issuance costs $ 69 $ 69 $ 204 $ 204 Fees $ 253 $ 260 $ 839 $ 765
Schedule of Current and Long-term Debt	The Company's total current and long-term debt balances at September 30, 2015 and December 31, 2014 were as follows: September 30, 2015 December 31, 2014 (In thousands) Current Long-Term Current Long-Term 1.75% Convertible Debentures Aggregate principal $ — $ 335,150 $ — $ 396,750 Debt discount — (80,990 ) — (105,634 ) Debt balance — 254,160 — 291,116 1.875% Convertible Debentures — 524 — 2,245 Capital Lease Obligation 1,107 — 2,067 580 Small Land Purchase 78 — 77 82 Total debt balances $ 1,185 $ 254,684 $ 2,144 $ 294,023
Schedule of Future Minimum Lease Payments for Capital Leases	The following is a schedule by year of the future minimum lease payments for the capital lease together with the present value of the net minimum lease payments: (In thousands) 2015 $ 542 2016 589 Total minimum lease payments 1,131 Interest at rates ranging from 5.21% to 5.46% (before-tax) (24 ) Net minimum lease payments $ 1,107

Mineral Properties and Mine D27

Mineral Properties and Mine Development (Tables)	9 Months Ended
	Sep. 30, 2015
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: September 30, December 31, (In thousands) 2015 2014 Mineral Properties: Montana, United States of America Stillwater Mine $ 1,950 $ 1,950 Ontario, Canada Marathon properties 8,560 55,332 San Juan, Argentina Altar property 101,970 101,970 Mine Development: Montana, United States of America Stillwater Mine 681,443 616,872 East Boulder Mine 216,232 204,483 1,010,155 980,607 Accumulated depletion and amortization (445,565 ) (411,601 ) Total mineral properties and mine development, net $ 564,590 $ 569,006

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	9 Months Ended
	Sep. 30, 2015
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: September 30, December 31, (In thousands) 2015 2014 Machinery and equipment $ 159,792 $ 152,421 Buildings and structural components 173,265 169,609 Land 11,740 9,488 Construction-in-progress: Stillwater Mine 953 2,633 East Boulder Mine 569 1,539 Marathon 148 148 Processing facilities and other 1,918 1,994 348,385 337,832 Accumulated depreciation (235,558 ) (218,951 ) Total property, plant, and equipment, net $ 112,827 $ 118,881
Schedule Capital Expenditures	The Company's total capital expenditures for mine development and property, plant and equipment for the nine -month periods ended September 30, 2015 and 2014 were as follows: September 30, September 30, (In thousands) 2015 2014 Stillwater Mine $ 70,172 $ 69,513 East Boulder Mine 13,548 21,189 Other 4,599 2,993 Total U.S. capital expenditures 88,319 93,695 Foreign capital expenditures 46 2 Non-cash capitalized interest / depreciation (6,756 ) (6,228 ) Change in accounts payables for capital expenditures 1,777 (431 ) Cash capital spend for the period $ 83,386 $ 87,038

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2015
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 September 30, 2015 Mine Production PGM Recycling Canadian Properties * All Other Total Revenues $ 86,359 $ 81,982 $ — $ — $ 100 $ 168,441 Depletion, depreciation and amortization $ 15,132 $ 230 $ — $ — $ — $ 15,362 General and administrative expenses $ — $ — $ 275 $ 100 $ 8,536 $ 8,911 Interest income $ — $ 437 $ 1 $ 4 $ 324 $ 766 Interest expense $ — $ — $ — $ — $ 5,097 $ 5,097 Income (loss) before income taxes $ 2,224 $ 3,261 $ (577 ) $ (339 ) $ (19,062 ) $ (14,493 ) Capital expenditures $ 24,661 $ 57 $ — $ — $ 450 $ 25,168 Total assets $ 608,198 $ 3,390 $ 27,078 $ 104,265 $ 574,256 $ 1,317,187 * Total assets includes cash and cash equivalents of $17.1 million . (In thousands) South American Properties Three Months Ended September 30, 2014 Mine Production PGM Recycling Canadian Properties All Other Total Revenues $ 137,067 $ 109,509 $ — $ — $ 5,490 $ 252,066 Depletion, depreciation and amortization $ 16,923 $ 258 $ — $ — $ — $ 17,181 General and administrative expenses * $ — $ — $ 794 $ 17 $ 9,240 $ 10,051 Interest income $ — $ 681 $ 1 $ 13 $ 236 $ 931 Interest expense $ — $ — $ — $ — $ 6,018 $ 6,018 Income (loss) before income taxes $ 34,904 $ 3,131 $ (1,205 ) $ 748 $ (14,124 ) $ 23,454 Capital expenditures $ 32,604 $ 28 $ — $ 2 $ 624 $ 33,258 Total assets $ 584,538 $ 88,411 $ 76,678 $ 107,909 $ 526,923 $ 1,384,459 * The Company reclassified Marketing expenses into General and administrative for All Other for the three-month period ended September 30, 2014, for presentation purposes. (In thousands) South American Nine Months Ended September 30, 2015 Mine Production PGM Recycling Canadian Properties * All Other Total Revenues $ 331,065 $ 222,980 $ — $ — $ 300 $ 554,345 Depletion, depreciation and amortization $ 48,943 $ 738 $ — $ — $ — $ 49,681 General and administrative expenses $ — $ — $ 790 $ 454 $ 26,408 $ 27,652 Interest income $ — $ 1,256 $ 7 $ 23 $ 906 $ 2,192 Interest expense $ — $ — $ — $ — $ 15,713 $ 15,713 Income (loss) before impairment charge and income taxes $ 52,446 $ 7,424 $ (1,364 ) $ (1,216 ) $ (46,805 ) $ 10,485 Impairment charge $ — $ — $ 46,772 $ — $ — $ 46,772 Income (loss) after impairment charge, before income taxes $ 52,446 $ 7,424 $ (48,136 ) $ (1,216 ) $ (46,805 ) $ (36,287 ) Capital expenditures $ 77,370 $ 221 $ — $ 46 $ 5,749 $ 83,386 Total assets $ 608,198 $ 3,390 $ 27,078 $ 104,265 $ 574,256 $ 1,317,187 * Total assets includes cash and cash equivalents of $17.1 million . (In thousands) South American Nine Months Ended September 30, 2014 Mine Production PGM Recycling Canadian Properties All Other Total Revenues $ 409,967 $ 305,760 $ — $ — $ 5,725 $ 721,452 Depletion, depreciation and amortization $ 49,373 $ 761 $ — $ — $ — $ 50,134 General and administrative expenses * $ — $ — $ 2,783 $ 339 $ 24,895 $ 28,017 Interest income $ — $ 1,998 $ 3 $ 44 $ 705 $ 2,750 Interest expense $ — $ — $ — $ — $ 17,737 $ 17,737 Income (loss) before income taxes $ 107,864 $ 9,225 $ (3,843 ) $ 2,841 $ (45,646 ) $ 70,441 Capital expenditures $ 84,335 $ 155 $ — $ 2 $ 2,546 $ 87,038 Total assets $ 584,538 $ 88,411 $ 76,678 $ 107,909 $ 526,923 $ 1,384,459 * The Company reclassified Research and development and Marketing expenses into General and administrative for All Other for the nine-month period ended September 30, 2014, for presentation purposes.

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2015
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 September 30, 2015 , and December 31, 2014 were as follows: Investments (In thousands) Amortized cost Gross unrealized gains Gross unrealized losses Fair value 2015 Federal agency notes $ 286,220 $ 106 $ (34 ) $ 286,292 Commercial paper 40,097 — (45 ) 40,052 Mutual funds 419 205 — 624 Total $ 326,736 $ 311 $ (79 ) $ 326,968 2014 Federal agency notes $ 143,132 $ 40 $ (33 ) $ 143,139 Commercial paper 108,371 1 (257 ) 108,115 Mutual funds 344 279 — 623 Total $ 251,847 $ 320 $ (290 ) $ 251,877
Schedule of Maturities of Available-for-sale Securities	The maturities of available-for-sale securities at September 30, 2015 were as follows: (In thousands) Amortized cost Fair value Federal agency notes Due in one year or less $ 237,658 $ 237,764 Due after one year through two years 48,562 48,528 Total $ 286,220 $ 286,292 Commercial paper Due in one year or less $ 26,612 $ 26,567 Due after one year through two years 13,485 13,485 Total $ 40,097 $ 40,052

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2015
Inventory Disclosure [Abstract]
Components Of Inventories	Inventories reflected in the accompanying balance sheets consisted of the following: September 30, December 31, (In thousands) 2015 2014 Metals inventory Raw ore $ 4,215 $ 4,984 Concentrate and in-process 59,803 48,712 Finished goods 40,493 49,885 Total metals inventory 104,511 103,581 Materials and supplies 22,452 26,726 Total inventory $ 126,963 $ 130,307

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
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 nine-month periods ended September 30, 2015 and 2014: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2015 2014 2015 2014 Stock options 6 — 6 — Nonvested shares 44 — 50 — Contingently issuable 218 111 218 125 1.875% Convertible debentures, net of tax 22 — 22 — 1.75% Convertible debentures, net of tax 30,413 — 30,413 —
Reconciliation of Basic and Diluted Earnings Per Share	Reconciliations showing the computation of basic and diluted shares and the related impact on income for the three - and nine-month periods ended September 30, 2014, are provided in the following table: Three Months Ended Nine Months Ended September 30, 2014 September 30, 2014 (In thousands, except per share amounts) Income (Numerator) Weighted Average Shares (Denominator) Per Share Amount Income (Numerator) Weighted Average Shares (Denominator) Per Share Amount Basic EPS Net income attributable to common stockholders $ 18,148 120,067 $ 0.15 $ 55,615 119,849 $ 0.46 Effect of Dilutive Securities Stock options — 6 — 31 Nonvested shares — 113 — 22 Contingently issuable shares — 107 — 45 1.875% Convertible debentures, net of tax — 95 — 95 1.75% Convertible debentures, net of tax 4,060 36,003 12,229 36,003 Diluted EPS Net income attributable to common stockholders and assumed conversions $ 22,208 156,391 $ 0.14 $ 67,844 156,045 $ 0.43

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2015
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 September 30, 2015 , and December 31, 2014 , consisted of the following: (In thousands) Fair Value Measurements At September 30, 2015 Total Level 1 Level 2 Level 3 Mutual funds $ 624 $ 624 $ — $ — Investments Federal agency notes $ 286,292 $ — $ 286,292 $ — Commercial paper $ 40,052 $ — $ 40,052 $ — (In thousands) Fair Value Measurements At December 31, 2014 Total Level 1 Level 2 Level 3 Mutual funds $ 623 $ 623 $ — $ — Investments Federal agency notes $ 143,139 $ — $ 143,139 $ — Commercial paper $ 108,115 $ — $ 108,115 $ —
Financial Assets And Liabilities Measured At Fair Value On A Nonrecurring Basis	Assets and liabilities measured at fair value on a nonrecurring basis at September 30, 2015 , and December 31, 2014 , consisted of the following: (In thousands) Fair Value Measurements At September 30, 2015 Total Level 1 Level 2 Level 3 Marathon mineral properties $ 8,560 $ — $ — $ 8,560 1.875% Convertible debentures $ 524 $ — $ 524 $ — 1.75% Convertible debentures $ 302,684 $ — $ 302,684 $ — Long-term investments $ 692 $ — $ 692 $ — (In thousands) Fair Value Measurements At December 31, 2014 Total Level 1 Level 2 Level 3 Certain Marathon real estate properties $ 754 $ — $ — $ 754 1.875% Convertible debentures $ 2,245 $ — $ 2,245 $ — 1.75% Convertible debentures $ 303,108 $ — $ 303,108 $ — Long-term investments $ 896 $ — $ 896 $ —

Sales (Narrative) (Details)

Sales (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Product Information [Line Items]
Revenues from by-product sales		$ 5,000,000	$ 6,900,000	$ 18,700,000	$ 22,200,000
Term of refining agreement	5 years
Period after which refining agreement may be terminated	4 years
Other revenue		100,000	5,490,000	$ 300,000	$ 5,725,000
Metal Acquired in Open Market and Resold to Third Parties [Member]
Product Information [Line Items]
Other revenue		$ 0	$ 5,300,000

Sales (Percentage Of Total Reve

Sales (Percentage Of Total Revenues From Significant Customers) (Details) - Sales Revenue, Goods, Net [Member] - Customer Concentration Risk [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenue, Major Customer [Line Items]
Major customer, percentage of total revenues	70.00%	77.00%	75.00%	61.00%
Customer A [Member]
Revenue, Major Customer [Line Items]
Major customer, percentage of total revenues	70.00%	67.00%	75.00%	45.00%
Customer B [Member]
Revenue, Major Customer [Line Items]
Major customer, percentage of total revenues	0.00%	10.00%	0.00%	16.00%

Asset Impairment (Details)

Asset Impairment (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Impaired Long-Lived Assets Held and Used [Line Items]
Estimated reclamation costs	$ 1,100
Impairment charge	$ 0			$ 0	$ 46,772	$ 0
Marathon Property [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge		$ 46,800	$ 500
Estimated fair value		$ 8,600

Noncontrolling Interest (Detail

Noncontrolling Interest (Details) - USD ($) $ in Thousands	Oct. 26, 2015	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2012	Dec. 31, 2014
Noncontrolling Interest [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners		25.00%			25.00%		25.00%
Cost of acquired entity, cash paid by third party							$ 81,250
Contribution, initial cash call, amount paid by third party							$ 13,600
Maximum PGM production purchase percentage							100.00%
Net income (loss) attributable to noncontrolling interest		$ (151)		$ (313)	$ (11,808)	$ (1,083)
Noncontrolling interest		6,672			6,672			$ 18,480
Impairment charge		0		$ 0	46,772	$ 0
Subsequent Event [Member]
Noncontrolling Interest [Line Items]
Purchase of noncontrolling interest, percent	25.00%
Purchase of noncontrolling interest, total consideration	$ 5,200
Purchase of noncontrolling interest, net of cash acquired	$ 1,000
Additional Paid-in Capital [Member]
Noncontrolling Interest [Line Items]
Issuance of noncontrolling interest							$ 42,500
Expenses incurred for issuance of noncontrolling interest							$ 1,100
Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Impairment charge			$ 11,700
Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest		$ 6,700			$ 6,700			$ 18,500

Derivative Instruments (Company

Derivative Instruments (Company's Outstanding Commodity Derivatives) (Details)	9 Months Ended
	Sep. 30, 2015oz$ / oz
Fourth Quarter 2015 [Member] | Platinum [Member]
Derivative [Line Items]
Ounces	34,967
Average Price/Ounce | $ / oz	1,003
Fourth Quarter 2015 [Member] | Palladium [Member]
Derivative [Line Items]
Ounces	49,347
Average Price/Ounce | $ / oz	630
Fourth Quarter 2015 [Member] | Rhodium [Member]
Derivative [Line Items]
Ounces	6,194
Average Price/Ounce | $ / oz	841
First Quarter 2016 [Member] | Platinum [Member]
Derivative [Line Items]
Ounces	3,247
Average Price/Ounce | $ / oz	968
First Quarter 2016 [Member] | Palladium [Member]
Derivative [Line Items]
Ounces	4,632
Average Price/Ounce | $ / oz	607
First Quarter 2016 [Member] | Rhodium [Member]
Derivative [Line Items]
Ounces	1,195
Average Price/Ounce | $ / oz	764

Stock-Based Compensation (Narra

Stock-Based Compensation (Narrative) (Details) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015USD ($)shares	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)targetshares	Sep. 30, 2014USD ($)	Apr. 30, 2012shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance | shares					11.6
Restricted stock units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Nonvested time-based shares [Member] | General and administrative expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense | $	$ 0.4	$ 0.4	$ 1.2	$ 1.4
Nonvested performance-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Number of distinct components			3
Number of sub-targets			5
Number of sub-targets, market-based and equity classified			2
Number of sub-targets, market-based and liability classified			1
Number of sub-targets, performance-based and equity classified			2
Nonvested performance-based shares [Member] | General and administrative expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense | $	$ 0.3	$ 0.2	$ 1	$ 0.8
Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period			10 years
2004 and 2012 Plans Combined [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available and reserved for grant | shares	4.4		4.4
2012 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance | shares					5
2004 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance | shares					5.2
General Employee Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance | shares					1.4

Stock-Based Compensation (Chang

Stock-Based Compensation (Changes In The Company's Nonvested Shares) (Details) - $ / shares	3 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
Nonvested time-based shares [Member]
Nonvested Shares
Nonvested Shares, Beginning Balance	267,968	265,952	184,747
Nonvested Shares, Granted	1,480	3,668	120,715
Nonvested Shares, Vested	(1,509)	(1,586)	(35,030)
Nonvested Shares, Forfeited	(6,624)	(66)	(4,480)
Nonvested Shares, Ending Balance	261,315	267,968	265,952
Weighted-Average Grant-Date Fair Value
Nonvested shares, Weighted-Average Grant-Date Fair Value, Beginning Balance (in usd per share)	$ 14.02	$ 14.03	$ 13.80
Nonvested shares, Weighted-Average Grant-Date Fair Value, Granted (in usd per share)	10.02	13.88	14.29
Nonvested shares, Weighted-Average Grant-Date Fair Value, Vested (in usd per share)	14.15	14.63	13.75
Nonvested shares, Weighted-Average Grant-Date Fair Value, Forfeited (in usd per share)	14.35	13.11	13.91
Nonvested shares, Weighted-Average Grant-Date Fair Value, Ending Balance (in usd per share)	$ 13.99	$ 14.02	$ 14.03
Nonvested performance-based shares [Member]
Nonvested Shares
Nonvested Shares, Beginning Balance	382,243	382,243	214,236
Nonvested Shares, Granted			170,078
Nonvested Shares, Vested			0
Nonvested Shares, Forfeited	(2,966)		(2,071)
Nonvested Shares, Ending Balance	379,277	382,243	382,243
Weighted-Average Grant-Date Fair Value
Nonvested shares, Weighted-Average Grant-Date Fair Value, Beginning Balance (in usd per share)	$ 15.35	$ 15.35	$ 15.69
Nonvested shares, Weighted-Average Grant-Date Fair Value, Granted (in usd per share)			$ 14.92
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)	15.34		$ 15.34
Nonvested shares, Weighted-Average Grant-Date Fair Value, Ending Balance (in usd per share)	$ 12.28	$ 15.35	$ 15.35

Stock-Based Compensation (Compe

Stock-Based Compensation (Compensation Expense of Nonvested Shares) (Details) $ in Thousands	Sep. 30, 2015USD ($)
Nonvested time-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining 2,015	$ 426
2,016	1,516
2,017	628
2,018	8
Total	2,578
Nonvested performance-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining 2,015	384
2,016	1,536
2,017	824
2,018	0
Total	$ 2,744

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Tax Contingency [Line Items]
Alternative minimum tax credit carryforwards	$ 31,600,000		$ 31,600,000
General business credits	1,600,000		1,600,000
State tax net operating loss carryforwards	3,300,000		3,300,000
Foreign net operating loss carryforward	51,600,000		51,600,000
Income tax benefit (provision)	2,464,000	$ (5,619,000)	8,127,000	$ (15,909,000)
Discrete income tax benefit, restructuring			10,600,000
Discrete income tax benefit, remeasurement of deferred state tax			$ 8,300,000
Deferred state tax rate			4.00%		10.60%
Interest and penalties accrued	0	$ 800,000	$ 0	800,000
Cash paid for income taxes			13,100,000	$ 14,200,000
Year 2016 to 2019 [Member]
Income Tax Contingency [Line Items]
Foreign net operating loss carryforward	18,100,000		18,100,000
Year 2024 to 2035 [Member]
Income Tax Contingency [Line Items]
Foreign net operating loss carryforward	25,400,000		25,400,000
Federal [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	104,800,000		104,800,000
Federal [Member] | Norilsk Nickel Change in Control [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	80,900,000		80,900,000
Annual limit on usage of net operating loss carryforwards	10,200,000		10,200,000
Foreign Tax Authority [Member]
Income Tax Contingency [Line Items]
Foreign net operating loss carryforward, not subject to expiration	$ 8,100,000		$ 8,100,000

Debt and Capital Lease Obliga43

Debt and Capital Lease Obligations (Narrative) (Details)	1 Months Ended					3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2014USD ($)	Mar. 31, 2013USD ($)	Oct. 31, 2012USD ($)$ / sharesshares	Jan. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Dec. 31, 2000USD ($)	Dec. 31, 2014USD ($)
Debt Instruments [Abstract]
Gain (loss) on extinguishment of debt, net						$ (4,010,000)	$ 0	$ (4,010,000)	$ 0
Capital Lease Obligation
Payments on capital lease obligations						500,000	500,000	1,600,000	1,600,000
Capital lease obligations						1,100,000		1,100,000			$ 2,600,000
Capitalized Interest
Capitalized interest						1,500,000	1,400,000	4,200,000	3,600,000
Capital Lease Obligations [Member]
Debt Instruments [Abstract]
Interest paid						100,000	100,000	$ 100,000	100,000
Capital Lease Obligation
Debt instrument term								4 years
Interest paid (less than for capital lease obligations)						$ 100,000	$ 100,000	$ 100,000	$ 100,000
1.75% Convertible Debentures [Member]
Debt Instruments [Abstract]
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 and equity issuance costs			$ 12,400,000
Debt and equity issuance costs amortization period			7 years
Net discounted proceeds of the offering			$ 384,300,000
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
Effective interest rate			8.50%
Convertible debentures						254,200,000		$ 254,200,000			$ 291,100,000
Unamortized discount						80,990,000		80,990,000			$ 105,634,000
Interest paid						423,000	$ 0	3,894,000	$ 3,472,000
Capital Lease Obligation
Interest paid (less than for capital lease obligations)						423,000	$ 0	$ 3,894,000	$ 3,472,000
1.75% Convertible Debentures [Member] | Loss on debt extinguishment, net [Member]
Debt Instruments [Abstract]
Gain (loss) on extinguishment of debt, net						$ (4,200,000)
1.875% Convertible Debentures [Member]
Debt Instruments [Abstract]
Stated interest rate		1.875%				1.875%	1.875%	1.875%	1.875%		1.875%
Repayments of convertible debt		$ 164,300,000
Principal amount of debt repurchased						$ 1,700,000
Cash paid to repurchase debt						1,600,000
Convertible debentures						500,000		$ 500,000			$ 500,000
Interest paid						21,000	$ 21,000	42,000	$ 42,000
Capital Lease Obligation
Interest paid (less than for capital lease obligations)						21,000	21,000	42,000	42,000
1.875% Convertible Debentures [Member] | Loss on debt extinguishment, net [Member]
Debt Instruments [Abstract]
Gain (loss) on extinguishment of debt, net						100,000
Credit Agreement [Member]
Debt Instruments [Abstract]
Credit agreement				$ 125,000,000	$ 100,000,000
Debt issuance costs				$ 200,000	$ 1,100,000
Borrowing base comprised eligible accounts receivable					85.00%
Borrowing base comprised eligible accounts inventories					70.00%
Letter of credit sub-facility					$ 60,000,000
Outstanding borrowings						0	0	0	0
Undrawn letters of credit issued as collateral for sureties						$ 17,500,000	$ 17,500,000	$ 17,500,000	$ 17,500,000
Credit Agreement [Member] | Minimum [Member]
Debt Instruments [Abstract]
Basis spread over LIBOR					2.25%
Commitment fee on unutilized borrowing capacity					0.375%
Credit Agreement [Member] | Maximum [Member]
Debt Instruments [Abstract]
Percentage of total borrowing capacity remaining when covenant takes effect (less than)					30.00%
Basis spread over LIBOR					2.75%
Commitment fee on unutilized borrowing capacity					0.50%
8% Series 2000 [Member]
Debt Instruments [Abstract]
Debt, principal amount										$ 30,000,000
Stated interest rate										8.00%
Net discounted proceeds of the offering										$ 28,700,000
Effective interest rate										8.57%
Repayment of debt	$ 30,000,000
Interest paid	40,000
Capital Lease Obligation
Interest paid (less than for capital lease obligations)	$ 40,000

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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Mar. 31, 2013	Oct. 31, 2012
Debt Instrument [Line Items]
Amortization of debt issuance costs			$ 1,665	$ 1,929
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	$ 240	$ 287	$ 714	$ 852
Interest expense	6,262	6,074	18,860	17,931
Cash payments for interest	$ 423	$ 0	$ 3,894	$ 3,472
1.875% Convertible Debentures [Member]
Debt Instrument [Line Items]
Stated interest rate	1.875%	1.875%	1.875%	1.875%	1.875%	1.875%
Interest expense	$ 9	$ 11	$ 30	$ 32
Cash payments for interest	21	21	42	42
Credit Agreement [Member]
Debt Instrument [Line Items]
Amortization of debt issuance costs	69	69	204	204
Fees	$ 253	$ 260	$ 839	$ 765

Debt and Capital Lease Obliga45

Debt and Capital Lease Obligations (Current and Long-Term Debt Balances) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Mar. 31, 2013	Oct. 31, 2012
Current
Capital Lease Obligation	$ 1,107	$ 2,067
Small Land Purchase	78	77
Total debt balances, Current	1,185	2,144
Long-Term
Capital Lease Obligation	0	580
Small Land Purchase	0	82
Total debt balances, Long-Term	$ 254,684	$ 294,023
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	396,750
Debt discount	(80,990)	(105,634)
Debt balance	$ 254,160	$ 291,116
1.875% Convertible Debentures [Member]
Debt Instrument [Line Items]
Stated interest rate	1.875%	1.875%	1.875%	1.875%
Current
Debt, Current	$ 0	$ 0
Long-Term
Aggregate principal	$ 524	$ 2,245

Debt and Capital Lease Obliga46

Debt and Capital Lease Obligations (Schedule of Future Minimum Lease Payments for Capital Leases) (Details) $ in Thousands	Sep. 30, 2015USD ($)
Capital Leased Assets [Line Items]
2,015	$ 542
2,016	589
Total minimum lease payments	1,131
Interest at rates ranging from 5.21% to 5.46% (before-tax)	(24)
Net minimum lease payments	$ 1,107
Minimum [Member]
Capital Leased Assets [Line Items]
Capital lease, interest rate	5.21%
Maximum [Member]
Capital Leased Assets [Line Items]
Capital lease, interest rate	5.46%

Mineral Properties and Mine D47

Mineral Properties and Mine Development (Schedule of Mineral Properties) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Mining Properties, Mineral Rights and Mine Development [Member]
Property, Plant and Equipment [Line Items]
Mineral properties and mine development, gross	$ 1,010,155	$ 980,607
Accumulated depletion and amortization	(445,565)	(411,601)
Total mineral properties and mine development, net	564,590	569,006
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	681,443	616,872
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	216,232	204,483
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	55,332
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 Equipment48

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	$ 348,385		$ 348,385		$ 337,832
Accumulated depreciation	(235,558)		(235,558)		(218,951)
Total property, plant, and equipment, net	112,827		112,827		118,881
Payments to Acquire Productive Assets [Abstract]
Non-cash capitalized interest / depreciation			(6,756)	$ (6,228)
Change in accounts payables for capital expenditures			1,777	(431)
Cash capital spend for the period	25,168	$ 33,258	83,386	87,038
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	159,792		159,792		152,421
Buildings and structural components [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	173,265		173,265		169,609
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	11,740		11,740		9,488
Construction-in progress [Member] | Stillwater Mine [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	953		953		2,633
Construction-in progress [Member] | East Boulder Mine [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	569		569		1,539
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	$ 1,918		1,918		$ 1,994
United States [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			88,319	93,695
United States [Member] | Stillwater Mine [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			70,172	69,513
United States [Member] | East Boulder Mine [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			13,548	21,189
United States [Member] | Other Mine [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			4,599	2,993
Foreign [Member]
Payments to Acquire Productive Assets [Abstract]
Capital expenditures			$ 46	$ 2

Segment Information (Narrative)

Segment Information (Narrative) (Details)	9 Months Ended
	Sep. 30, 2015SegmentBusiness_Component
Segment Reporting Information [Line Items]
Number of business segments	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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 168,441	$ 252,066	$ 554,345	$ 721,452
Depletion, depreciation and amortization	15,362	17,181	49,681	50,134
General and administrative expenses	8,911	10,051	27,652	28,017
Interest income	766	931	2,192	2,750
Interest expense	5,097	6,018	15,713	17,737
Income (loss) before impairment charge and income taxes			10,485
Impairment charge	0	0	46,772	0
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)	(14,493)	23,454	(36,287)	70,441
Capital expenditures	25,168	33,258	83,386	87,038
Total assets	1,317,187	1,384,459	1,317,187	1,384,459	$ 1,399,327
Cash and cash equivalents	133,956	257,617	133,956	257,617	$ 280,286	$ 286,687
Mine Production [Member] | Business Segments [Member]
Segment Reporting Information [Line Items]
Revenues	86,359	137,067	331,065	409,967
Depletion, depreciation and amortization	15,132	16,923	48,943	49,373
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 taxes			52,446
Impairment charge			0
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)	2,224	34,904	52,446	107,864
Capital expenditures	24,661	32,604	77,370	84,335
Total assets	608,198	584,538	608,198	584,538
PGM Recycling [Member] | Business Segments [Member]
Segment Reporting Information [Line Items]
Revenues	81,982	109,509	222,980	305,760
Depletion, depreciation and amortization	230	258	738	761
General and administrative expenses	0	0	0	0
Interest income	437	681	1,256	1,998
Interest expense	0	0	0	0
Income (loss) before impairment charge and income taxes			7,424
Impairment charge			0
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)	3,261	3,131	7,424	9,225
Capital expenditures	57	28	221	155
Total assets	3,390	88,411	3,390	88,411
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	275	794	790	2,783
Interest income	1	1	7	3
Interest expense	0	0	0	0
Income (loss) before impairment charge and income taxes			(1,364)
Impairment charge			46,772
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)	(577)	(1,205)	(48,136)	(3,843)
Capital expenditures	0	0	0	0
Total assets	27,078	76,678	27,078	76,678
Cash and cash equivalents	17,100		17,100
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	100	17	454	339
Interest income	4	13	23	44
Interest expense	0	0	0	0
Income (loss) before impairment charge and income taxes			(1,216)
Impairment charge			0
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)	(339)	748	(1,216)	2,841
Capital expenditures	0	2	46	2
Total assets	104,265	107,909	104,265	107,909
All Other [Member] | Business Segments [Member]
Segment Reporting Information [Line Items]
Revenues	100	5,490	300	5,725
Depletion, depreciation and amortization	0	0	0	0
General and administrative expenses	8,536	9,240	26,408	24,895
Interest income	324	236	906	705
Interest expense	5,097	6,018	15,713	17,737
Income (loss) before impairment charge and income taxes			(46,805)
Impairment charge			0
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)	(19,062)	(14,124)	(46,805)	(45,646)
Capital expenditures	450	624	5,749	2,546
Total assets	$ 574,256	$ 526,923	$ 574,256	$ 526,923

Investments (Narrative) (Detail

Investments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Other than temporary impairment of investments	$ 0.2	$ 0.2	$ 0.2	$ 0.2
Other Noncurrent Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Long-term investments	$ 0.7		$ 0.7		$ 0.9

Investments (Schedule of Availa

Investments (Schedule of Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 326,736	$ 251,847
Gross unrealized gains	311	320
Gross unrealized losses	(79)	(290)
Fair value	326,968	251,877
Federal agency notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	286,220	143,132
Gross unrealized gains	106	40
Gross unrealized losses	(34)	(33)
Fair value	286,292	143,139
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	40,097	108,371
Gross unrealized gains	0	1
Gross unrealized losses	(45)	(257)
Fair value	40,052	108,115
Mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	419	344
Gross unrealized gains	205	279
Gross unrealized losses	0	0
Fair value	$ 624	$ 623

Investments (Schedule of Maturi

Investments (Schedule of Maturities of Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 326,736	$ 251,847
Fair value	326,968	251,877
Federal agency notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost, due in one year or less	237,658
Fair value, due in one year or less	237,764
Amortized cost, due after year one through two years	48,562
Fair value, due after year one through two years	48,528
Amortized cost	286,220	143,132
Fair value	286,292	143,139
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost, due in one year or less	26,612
Fair value, due in one year or less	26,567
Amortized cost, due after year one through two years	13,485
Fair value, due after year one through two years	13,485
Amortized cost	40,097	108,371
Fair value	$ 40,052	$ 108,115

Inventories (Components Of Inve

Inventories (Components Of Inventories) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Metals inventory
Raw ore	$ 4,215	$ 4,984
Concentrate and in-process	59,803	48,712
Finished goods	40,493	49,885
Total metals inventory	104,511	103,581
Materials and supplies	22,452	26,726
Total inventory	$ 126,963	$ 130,307

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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Mar. 31, 2013	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	6	0	6	0
Nonvested shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings per share	44	0	50	0
Contingently issuable [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings per share	218	111	218	125
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%
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	0	22	0
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	0	30,413	0

Earnings Per Share (Reconciliat

Earnings Per Share (Reconciliation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Mar. 31, 2013	Oct. 31, 2012
Basic EPS
Net income attributable to common stockholders	$ (11,878)	$ 18,148	$ (16,352)	$ 55,615
Weighted Average Shares (Denominator) (in shares)	120,960	120,067	120,746	119,849
Net income attributable to common stockholders (in usd per share)	$ (0.10)	$ 0.15	$ (0.14)	$ 0.46
Effect of Dilutive Securities
Convertible debentures, net of tax		$ 4,060		$ 12,229
Stock options (in shares)		6		31
Nonvested shares (in shares)		113		22
Contingently issuable shares (in shares)		107		45
Diluted EPS
Net income attributable to common stockholders and assumed conversions		$ 22,208		$ 67,844
Weighted Average Shares (Denominator) (in shares)	120,960	156,391	120,746	156,045
Net income attributable to common stockholders and assumed conversions (in usd per share)	$ (0.10)	$ 0.14	$ (0.14)	$ 0.43
1.875% Convertible Debentures [Member]
Effect of Dilutive Securities
Convertible debentures, net of tax (in shares)		95		95
Diluted EPS
Stated interest rate	1.875%	1.875%	1.875%	1.875%	1.875%	1.875%
1.75% Convertible Debentures [Member]
Effect of Dilutive Securities
Convertible debentures, net of tax (in shares)		36,003		36,003
Diluted EPS
Stated interest rate	1.75%	1.75%	1.75%	1.75%	1.75%		1.75%

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2013	Oct. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impairment charge	$ 0			$ 0	$ 46,772	$ 0
1.875% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	$ 500		$ 500		$ 500
Stated interest rate	1.875%		1.875%	1.875%	1.875%	1.875%	1.875%
1.75% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	$ 254,200		$ 291,100		$ 254,200
Stated interest rate	1.75%		1.75%	1.75%	1.75%	1.75%		1.75%
Long-term debt, balance outstanding	$ 335,150		$ 396,750		$ 335,150
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund	$ 45,900		120,000		$ 45,900
Marathon Property [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impairment charge		$ 46,800	$ 500
Estimated fair value		$ 8,600

Fair Value Measurements (Financ

Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 326,344	$ 251,254
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mutual funds	624	623
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mutual funds	624	623
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mutual funds	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mutual funds	0	0
Fair Value, Measurements, Recurring [Member] | Federal Agency Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	286,292	143,139
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	286,292	143,139
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	40,052	108,115
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	40,052	108,115
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 (Fina59

Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Nonrecurring Basis) (Details) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marathon mineral properties	$ 8,560
Certain Marathon real estate properties		$ 754
Long-term investments	692	896
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marathon mineral properties	0
Certain Marathon real estate properties		0
Long-term investments	0	0
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marathon mineral properties	0
Certain Marathon real estate properties		0
Long-term investments	692	896
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marathon mineral properties	8,560
Certain Marathon real estate properties		754
Long-term investments	0	0
1.875% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	524	2,245
1.875% Convertible Debentures [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	0	0
1.875% Convertible Debentures [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	524	2,245
1.875% Convertible Debentures [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	0	0
1.75% Convertible Debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	302,684	303,108
1.75% Convertible Debentures [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	0	0
1.75% Convertible Debentures [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures, fair value	302,684	303,108
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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2012
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	25.00%		25.00%		25.00%
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Revenue from related parties	$ 15.2	$ 24.9	$ 38.7	$ 118.7