Stillwater Mining (SWC) 10-K 22 Feb 16 2015 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2015	Feb. 19, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Entity Registrant Name	STILLWATER MINING CO /DE/
Entity Central Index Key	931,948
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		121,049,984
Entity Public Float			$ 1.2
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

Consolidated Statements of Comp

Consolidated Statements of Comprehensive (Loss) Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
REVENUES
Mine Production	$ 415,774	$ 536,010	$ 478,918
PGM Recycling	310,156	401,684	560,588
Other	400	5,925	0
Total revenues	726,330	943,619	1,039,506
Costs of metals sold
Mine Production	293,955	332,632	313,963
PGM Recycling	300,710	391,481	527,384
Other	0	5,357	0
Total costs of metals sold (excludes depletion, depreciation and amortization)	594,665	729,470	841,347
Depletion, depreciation and amortization
Mine Production	64,200	66,387	58,201
PGM Recycling	949	1,019	1,116
Total depletion, depreciation and amortization	65,149	67,406	59,317
Total costs of revenues	659,814	796,876	900,664
Losses on trade receivable and inventory purchases	0	0	632
(Gain) loss on disposal of property, plant and equipment	(216)	(337)	68
Loss on long-term investments	372	125	1,894
Impairment of property, plant and equipment and non-producing mineral properties	46,772	550	461,755
Exploration	3,591	2,768	11,169
Proxy contest	0	0	4,307
Accelerated equity based compensation for change in control	0	0	9,063
Reorganization	1,658	10,402	0
General and administrative	34,033	35,067	46,577
Total costs and expenses	746,024	845,451	1,436,129
OPERATING (LOSS) INCOME	(19,694)	98,168	(396,623)
OTHER INCOME (EXPENSE)
Other	920	904	1,173
Loss on extinguishment of debt, net	(4,010)	0	0
Interest income	2,955	3,551	4,481
Interest expense	(20,187)	(22,719)	(22,957)
Foreign currency transaction gain, net	3,947	5,237	18,200
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)	(36,069)	85,141	(395,726)
Income tax benefit (provision)	12,333	(16,258)	93,653
NET (LOSS) INCOME	(23,736)	68,883	(302,073)
Net loss attributable to noncontrolling interest	(11,808)	(1,414)	(31,867)
NET (LOSS) INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS	(11,928)	70,297	(270,206)
Other comprehensive (loss) income, net of tax
Net unrealized (loss) gain on investments available-for-sale and deferred compensation	(214)	11	105
COMPREHENSIVE (LOSS) INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS	(12,142)	70,308	(270,101)
Comprehensive loss attributable to noncontrolling interest	(11,808)	(1,414)	(31,867)
TOTAL COMPREHENSIVE (LOSS) INCOME	$ (23,950)	$ 68,894	$ (301,968)
Weighted average common shares outstanding
Basic (in shares)	120,809	119,953	118,607
Diluted (in shares)	120,809	156,233	118,607
Basic (loss) earnings per share attributable to common stockholders (in usd per share)	$ (0.10)	$ 0.59	$ (2.28)
Diluted (loss) earnings per share attributable to common stockholders (in usd per share)	$ (0.10)	$ 0.56	$ (2.28)

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 147,336	$ 280,286
Investments, at fair value (Note 11)	316,429	251,254
Inventories	102,072	130,307
Trade receivables	800	1,277
Deferred income taxes	0	21,055
Prepaid expenses	2,821	2,546
Other current assets	21,628	14,671
Total current assets	591,086	701,396
Mineral properties	112,480	159,252
Mine development, net	460,751	409,754
Property, plant and equipment, net	109,957	118,881
Deferred debt issuance costs	3,821	6,032
Other noncurrent assets	4,115	4,012
Total assets	1,282,210	1,399,327
Current liabilities
Accounts payable	18,205	26,806
Accrued compensation and benefits	30,046	29,973
Property, production and franchise taxes payable	13,907	15,828
Current portion of long-term debt and capital lease obligations	657	2,144
Other current liabilities	5,286	7,288
Total current liabilities	68,101	82,039
Long-term debt and capital lease obligations	258,920	294,023
Deferred income taxes	22,761	68,896
Accrued workers compensation	6,070	6,060
Asset retirement obligation	11,027	9,401
Other noncurrent liabilities	6,102	7,200
Total liabilities	372,981	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; 121,049,471 and 120,381,746 issued and outstanding at December 31, 2015 and 2014, respectively	1,210	1,204
Paid-in capital	1,099,283	1,091,146
Accumulated deficit	(191,067)	(179,139)
Accumulated other comprehensive (loss) income	(197)	17
Total stockholders’ equity	909,229	913,228
Noncontrolling interest	0	18,480
Total equity	909,229	931,708
Total liabilities and equity	$ 1,282,210	$ 1,399,327

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Preferred stock
Preferred stock, par value (in usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	121,049,471	120,381,746
Common stock, shares outstanding	121,049,471	120,381,746

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net (loss) income	$ (23,736)	$ 68,883	$ (302,073)
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depletion, depreciation and amortization	65,149	67,406	59,317
Losses on trade receivable and inventory purchases	0	0	632
(Gain) loss on disposal of property, plant and equipment	(216)	(337)	68
Impairment of property, plant and equipment and non-producing mineral properties	46,772	550	461,755
Loss on long-term investments	372	125	1,894
Loss on extinguishment of debt, net	4,010	0	0
Amortization/accretion of premiums/discounts for investments	2,414	1,810	3,079
Deferred income taxes	(17,711)	(4,590)	(108,543)
Foreign currency transaction gain, net	(3,947)	(5,237)	(18,200)
Accretion of asset retirement obligation	812	747	689
Amortization of deferred debt issuance costs	2,211	2,265	1,664
Accretion of convertible debenture debt discount	17,222	17,156	15,783
Accelerated equity based compensation for change in control	0	0	9,063
Share based compensation and other benefits	10,080	14,001	15,242
Non-cash capitalized interest	(4,068)	(3,278)	(2,878)
Excess tax shortfall (benefit) from stock-based compensation	154	(46)	(2,756)
Changes in operating assets and liabilities:
Inventories	28,440	27,062	(4,252)
Trade receivables	477	7,711	333
Prepaid expenses	(275)	1,366	1,108
Accounts payable	(4,611)	(7,952)	3,187
Accrued compensation and benefits	73	(673)	(723)
Property, production and franchise taxes payable	(3,019)	1,271	2,006
Income taxes payable	0	(4,416)	4,416
Accrued workers compensation	10	29	216
Other operating assets	(6,792)	1,206	6,790
Other operating liabilities	(3,400)	2,493	1,616
NET CASH PROVIDED BY OPERATING ACTIVITIES	110,421	187,552	149,433
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures	(107,434)	(119,682)	(129,029)
Proceeds from disposal of property, plant and equipment	387	465	218
Purchases of investments	(286,380)	(229,462)	(151,567)
Proceeds from maturities and sales of investments	218,475	185,722	201,255
NET CASH USED IN INVESTING ACTIVITIES	(174,952)	(162,957)	(79,123)
CASH FLOWS FROM FINANCING ACTIVITIES
Purchase of noncontrolling interest	(5,216)	0	0
Excess tax (shortfall) benefit from stock-based compensation	(154)	46	2,756
Payments on debt and capital lease obligations	(63,109)	(32,035)	(166,187)
Proceeds from issuance of common stock	60	993	128
NET CASH USED IN FINANCING ACTIVITIES	(68,419)	(30,996)	(163,303)
CASH AND CASH EQUIVALENTS
Net decrease	(132,950)	(6,401)	(92,993)
Balance at beginning of period	280,286	286,687	379,680
BALANCE AT END OF PERIOD	$ 147,336	$ 280,286	$ 286,687

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Paid-in Capital [Member]	Accumulated Earnings (Deficit) [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Noncontrolling Interest [Member]
BALANCE, beginning of year (in shares) at Dec. 31, 2012		116,951,000
BALANCE, beginning of year at Dec. 31, 2012	$ 1,132,580	$ 1,170	$ 1,058,978	$ 20,770	$ (99)	$ 51,761
Increase (Decrease) in Equity [Roll Forward]
Net (loss) income	(302,073)			(270,206)		(31,867)
Change in fair market value of investments available-for-sale, net of tax	105				105
Common stock issued under employee benefit plans (in shares)		2,515,000
Common stock issued under share-based plans	10,707	$ 25	10,682
Income tax benefit (shortfall) on share-based plans	2,756		2,756
Compensation expense under share-based plans	13,685		13,685
Stock option expense	41		41
Valuation allowance/Deferred taxes	(9,942)		(9,942)
BALANCE, end of year (in shares) at Dec. 31, 2013		119,466,000
BALANCE, end of year at Dec. 31, 2013	847,859	$ 1,195	1,076,200	(249,436)	6	19,894
Increase (Decrease) in Equity [Roll Forward]
Net (loss) income	68,883			70,297		(1,414)
Change in fair market value of investments available-for-sale, net of tax	11				11
Common stock issued under employee benefit plans (in shares)		916,000
Common stock issued under share-based plans	10,851	$ 9	10,842
Income tax benefit (shortfall) on share-based plans	46		46
Compensation expense under share-based plans	4,141		4,141
Valuation allowance/Deferred taxes	$ (83)		(83)
BALANCE, end of year (in shares) at Dec. 31, 2014	120,381,746	120,382,000
BALANCE, end of year at Dec. 31, 2014	$ 931,708	$ 1,204	1,091,146	(179,139)	17	18,480
Increase (Decrease) in Equity [Roll Forward]
Net (loss) income	(23,736)			(11,928)		(11,808)
Change in fair market value of investments available-for-sale, net of tax	(384)				(384)
Change in fair value of deferred compensation, net of tax	170				170
Common stock issued under employee benefit plans (in shares)		667,000
Common stock issued under share-based plans	7,234	$ 6	7,228
Income tax benefit (shortfall) on share-based plans	(154)		(154)
Compensation expense under share-based plans	2,905		2,905
Extinguishment of debt, net of tax	(3,298)		(3,298)
Purchase of noncontrolling interest	$ (5,216)		1,456			(6,672)
BALANCE, end of year (in shares) at Dec. 31, 2015	121,049,471	121,049,000
BALANCE, end of year at Dec. 31, 2015	$ 909,229	$ 1,210	$ 1,099,283	$ (191,067)	$ (197)	$ 0

Nature of Operations

Nature of Operations	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations	NATURE OF OPERATIONS Stillwater Mining Company (the Company) is engaged in the development, extraction, processing, smelting, and refining of palladium, platinum and associated metals (platinum group metals or PGMs) from a geological formation in south-central Montana known as the J-M Reef and from the recycling of spent catalytic converters and other industrial sources. The Company is also engaged in expanding its mining development along the J-M Reef, and holds exploration-stage properties at the Marathon PGM-copper property adjacent to Lake Superior in northern Ontario, Canada (Marathon) and at the Altar copper-gold property in San Juan province, Argentina.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES PRINCIPLES OF CONSOLIDATION The accompanying consolidated financial statements include the accounts of Stillwater Mining Company, its wholly-owned subsidiaries and entities in which it holds a controlling interest (collectively referred to as the “Company”). All inter-company transactions and balances have been eliminated upon consolidation. CASH AND CASH EQUIVALENTS Cash and cash equivalents consist of all cash balances and all highly liquid investments purchased with an original maturity of three months or less. INVESTMENTS Investment securities at December 31, 2015 , and 2014 , consist of mutual funds, federal agency notes and commercial paper with stated maturities less than two years . All securities are reported at fair value. Unrealized holding gains and losses on available-for-sale securities are excluded from earnings and are reported as a separate component of other comprehensive income (loss) until realized. Realized gains and losses are based on the carrying value (cost, net of discounts or premiums) of the sold investment and recorded as a component of other income. A decline in the market value of any available-for-sale security below cost that is deemed to be other-than-temporary results in a reduction of the carrying amount of the security to fair value. The impairment is charged to earnings and a new cost basis for the security is established. The Company’s long-term investments in several junior exploration companies were originally recorded at cost due to less than 20% equity ownership interest and no significant Company control over the investees. A decline in the market value of these long-term investments that is deemed to be other-than-temporary will result in a reduction of the carrying amount of the investment to fair value. The impairment is charged to earnings and a new cost basis for the investment is established. RESTRICTED INVESTMENTS Restricted investments are amounts that have been pledged as collateral on outstanding undrawn letters of credit (associated with reclamation obligations). The Company reviews the letters of credit and the nature of the collateral annually and therefore restricted investments is classified as current. The restrictions on the balances lapse upon expiration of the letters of credit which currently have terms of one year or less. INVENTORIES Mined inventories are carried at the lower of current realizable value or average cost. Production costs include the cost of direct labor and materials, depletion, depreciation and amortization, and overhead costs relating to mining and processing activities. The value of recycled inventories is determined based on the acquisition cost of the recycled material and includes all inventoriable processing costs, including direct labor, direct materials, depreciation, transportation and third-party refining costs which relate to the processing activities. Materials and supplies inventories are valued at the lower of average cost or fair market value. RECEIVABLES Trade receivables and other receivable balances recorded in other current assets are reported at outstanding principal amounts, net of an allowance for doubtful accounts, if deemed necessary. Management evaluates the collectability of receivable account balances to determine the allowance, if any. Management considers the other party’s credit risk and financial condition, as well as current and projected economic and market conditions, in determining the amount of the allowance. Receivable balances are written off when management determines that the balance is uncollectable. The Company determined that no allowance against its receivable balances at December 31, 2015 and 2014 was necessary. MINERAL PROPERTIES AND MINE DEVELOPMENT Costs of acquiring mineral properties and mineral rights are capitalized as incurred. Prior to acquiring such mineral properties or mineral rights, the Company makes a preliminary evaluation to determine that the mineral property has significant potential to develop an economic ore body. The time between initial acquisition and full evaluation of a mineral property’s potential is variable and is determined by many factors including its location relative to existing infrastructure, stage of development, geological controls and relevant metal prices. When it has been determined that proven and probable ore reserves have been established in compliance with the SEC's Industry Guide 7, and a determination has been made to proceed toward commercial development, mining development costs incurred to develop the mineral property are capitalized. Mining exploration costs are expensed as incurred. If a mineable ore body is discovered, such costs are amortized when production begins using the units-of-production method based on the estimated quantities of recoverable metal. If no mineable ore body is discovered, such costs are expensed in the period in which it is determined the mineral property has no future economic value. Costs incurred to maintain assets on a standby basis are charged to operations. Costs of abandoned projects are charged to operations upon abandonment. Capitalized mine development costs are expenditures incurred to increase existing production, develop new ore bodies or develop mineral property substantially in advance of production. Capitalized mine development costs include a vertical shaft, multiple surface adits and underground infrastructure development including footwall laterals, ramps, rail and transportation, electrical and ventilation systems, shop facilities, material handling areas, ore handling facilities, dewatering and pumping facilities. These expenditures are capitalized and amortized over the life of the mine or over a shorter mining period, depending on the period benefited by those expenditures, using the units-of-production method. The Company utilizes Industry Guide 7 compliant total proven and probable ore reserves, measured in tons, as the basis for determining the life of mine and uses the ore reserves in the immediate and relevant vicinity as the basis for determining the shorter mining period. The Company calculates amortization of capitalized mine development costs in any vicinity by applying an amortization rate to the relevant current production. The amortization rates are each based upon a ratio of unamortized capitalized mine development costs to the related ore reserves. Capital development expenditures are added to the unamortized capitalized mine development costs and amortization rates are updated as the related assets are placed into service. In calculating the amortization rate, changes in ore reserves are accounted for as a prospective change in estimate. Ore reserves and the further benefit of capitalized mine development costs are determined based on management assumptions. Any significant changes in these assumptions, such as a change in the mine plan or a change in estimated proven and probable ore reserves could have a material effect on the expected period of benefit resulting in a potentially significant change in the amortization rate and / or the valuations of related assets. The Company’s proven ore reserves are generally expected to be extracted utilizing its existing mine development infrastructure. Additional capital expenditures will be required to access the Company’s estimated probable ore reserves. These anticipated capital expenditures are not included in the current calculation of depletion, depreciation and amortization. Expenditures incurred to sustain existing production and directly access specific ore reserve blocks or stopes provide benefit to ore reserve production over limited periods of time (secondary development) and are charged to operations as incurred. These costs include ramp and stope access excavations from the primary haulage levels (footwall laterals), stope material re-handling / laydown excavations, stope ore and waste pass excavations and chute installations, stope ventilation raise excavations and stope utility and pipe raise excavations. PROPERTY, PLANT AND EQUIPMENT Plant facilities and equipment are recorded at cost and depreciated using the straight-line method over estimated useful lives ranging from one to fifteen years. Interest is capitalized on expenditures related to major construction or development projects and is amortized using the same method as the related asset. Interest capitalization is discontinued when the asset is placed into operation or when development and construction cease. Maintenance and repairs are charged to cost of revenues as incurred. LEASES The Company classifies a lease as either capital or operating. All capital leases are depreciated over the shorter of the useful life of the asset or the lease term. ASSET IMPAIRMENT The Company reviews and evaluates its long-lived assets, including mineral properties and mine development, for impairment when events or changes in circumstances indicate that the related carrying amounts for such an asset may not be recoverable. For purposes of determining impairment, assets are grouped at the lowest level for which identifiable cash flows are largely independent of the cash flows of other groups of assets and liabilities. Impairment is considered to exist if the carrying amount of any long-lived asset or asset group is not recoverable and exceeds its fair value; the carrying value of a long-lived asset is considered not recoverable if it exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset or asset group. If impairment exists, the associated impairment loss to be recognized is the amount by which the carrying amount of the long-lived asset or asset group exceeds the fair value. In the Company’s case, the estimation of future cash flows takes into account estimates of recoverable ounces, prices for PGMs and other relevant metals (using twelve-quarter historical trailing prices and third-party projections of future prices, rather than prices at a single point in time, as indicators of longer-term future prices), any structural shifts in supply and demand or in competitive position, anticipated production levels, and future capital and reclamation expenditures, all based on life-of-mine plans and projections and measured as of the reporting date. The Company assesses, at least quarterly, whether there has been any event or change in circumstances that might indicate that the carrying value of capitalized mining costs and related property, plant and equipment, if any, may not be recoverable out of expected undiscounted future cash flows plus any estimated salvage value. In estimating the fair value of an asset or asset group, the Company takes into account various measurement alternatives, often engaging third-party advisors to assist in the process. Such alternatives will vary depending on the circumstances but could include information from recent sales of comparable assets, third-party professional appraisals, bona fide purchase offers, and valuations derived from discounted future cash flow models. Assumptions underlying future cash flows are subject to risks and uncertainties. Any differences between significant assumptions and market conditions such as PGM prices, lower than expected recoverable ounces, and / or the Company’s operating performance could have a material effect on the Company’s determination of ore reserves, or its ability to recover the carrying amounts of its long-lived assets resulting in potential additional impairment charges. FAIR VALUE OF FINANCIAL INSTRUMENTS The Company’s non-derivative financial instruments consist primarily of cash equivalents, trade receivables, payables, investments, convertible debentures and capital lease obligations. The carrying amounts of cash equivalents, trade receivables and payables approximate fair value due to their short maturities. The carrying amounts of investments approximate fair value based on market quotes. 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 fair value hierarchy was established which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The fair value hierarchy distinguishes among three levels of inputs that may be utilized when measuring fair value: Level 1 inputs (using quoted prices in active markets for identical assets or liabilities), Level 2 inputs (using external inputs other than Level 1 prices such as quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability) and Level 3 inputs (unobservable inputs supported by little or no market activity and based on internal assumptions used to measure assets and liabilities). The classification of each financial asset or liability within the above hierarchy is determined based on the lowest level input that is significant to the fair value measurement. REVENUE RECOGNITION Revenue is comprised of Mine Production revenue, PGM Recycling revenue and other sales revenue. Mine Production revenue consists of the sales of palladium and platinum extracted by the Company’s mining operations, including any realized hedging gains or losses. Mine Production revenue also consists of the sales of by-products (rhodium, gold, silver, copper and nickel) extracted by mining operations. PGM Recycling revenue consists of the sales of recycled palladium, platinum and rhodium derived from spent catalytic materials, including any unrealized and realized hedging gains or losses. PGM recycling revenue also includes revenue from toll processing. Other sales revenue consists of sales of PGMs that are acquired periodically in the open market and simultaneously resold to third parties. Revenue is recognized when persuasive evidence of an arrangement exists, delivery has occurred either physically or through an irrevocable transfer of metals to customers’ accounts, the price is fixed or determinable, no related obligations remain and collectability is probable. Under the terms of sales contracts and purchase orders received from customers, the Company recognizes revenue when the product is in a refined and saleable form and title passes, which is typically when the product is transferred from the account of the Company to the account of the customer. Under certain of its sales agreements, the Company instructs a third-party refiner to transfer metal from the Company’s account to the customer’s account; at this point, the Company’s account at the third-party refinery is reduced and the purchaser’s account is increased by the number of ounces of metal sold. These transfers are irrevocable and the Company has no further responsibility for the delivery of the metals. Under other sales agreements, physical conveyance occurs by the Company arranging for shipment of metal from the third-party refinery to the purchaser. In these cases, revenue is recognized at the point when title passes contractually to the purchaser. Sales discounts are recognized when the related revenue is recorded. The Company classifies any sales discounts as a reduction in revenue. The Company recognizes revenue from its toll processing services at the time the contained metals are returned to the supplier at the third-party refinery. NONCONTROLLING INTEREST Noncontrolling interest relates to the sale of a 25% ownership interest in Stillwater Canada Inc during 2012. Noncontrolling interest is classified in the Company's Consolidated Statements of Comprehensive (Loss) Income as part of consolidated net (loss) income and the accumulated amount of noncontrolling interest in the Company's Consolidated Balance Sheets as a component of equity. In the fourth quarter of 2015, the Company repurchased the 25% ownership interest. RECLAMATION AND ENVIRONMENTAL COSTS The fair value of a liability for an asset retirement obligation is recognized in the period in which it is incurred if a reasonable estimate of fair value can be made. The fair value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the life of the asset. The liability is accreted at the end of each period through charges to operating expense. If the obligation is settled for other than the carrying amount of the liability, the Company will recognize a gain or loss on settlement. Accounting for reclamation obligations requires management to make estimates for each mining operation of the future costs the Company will incur to complete final reclamation work required to comply with existing laws and regulations. Actual costs incurred in future periods could differ from amounts estimated. Additionally, future changes to environmental laws and regulations could increase the extent of reclamation and remediation work that the Company is required to perform. Any such increases in future costs could materially impact the amounts charged in future periods to operations for reclamation and remediation. INCOME TAXES The Company determines income taxes using the asset and liability method which results in the recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the carrying amounts and the tax bases of those assets and liabilities, as well as operating loss and tax credit carryforwards, using enacted tax rates in effect in the years in which the differences are expected to reverse. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Deferred tax assets and liabilities are recorded on a jurisdictional basis. In assessing the realizability of U.S. and foreign deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. Each quarter, management considers the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies in making this assessment. A valuation allowance has been provided at December 31, 2015 , and 2014 , for the portion of the Company’s net deferred tax assets for which it is more likely than not that they will not be realized. STOCK-BASED COMPENSATION The Company estimates the fair value of performance-based restricted stock awards using a Monte Carlo simulation valuation model. The fair value of time-based restricted stock awards is determined by the market value of the underlying shares on the date of grant. Costs resulting from all share-based payment transactions are recognized in the financial statements over the respective vesting periods. All liability classified performance-based restricted stock awards are revalued each period with a charge to earnings. EARNINGS (LOSS) PER COMMON SHARE Basic earnings (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted earnings (loss) 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 and the Company’s convertible debentures were converted. Reported net income (loss) attributable to common stockholders is adjusted for the interest expense net of capitalized interest (including amortization expense of deferred debt and equity fees), the related income tax effect and the income (loss) attributable to the noncontrolling interest in the computation of basic and diluted earnings per share attributable to common stockholders. The Company currently has only one class of equity shares outstanding. COMPREHENSIVE (LOSS) INCOME Comprehensive (loss) income includes net (loss) income, as well as other changes in stockholders’ equity that result from transactions and events other than those with stockholders. Other comprehensive (loss) income in 2015, 2014 and 2013 consisted of unrealized gains and losses related to available-for-sale marketable securities and deferred compensation. DEBT ISSUANCE COSTS Debt issuance costs are capitalized and amortized to interest expense using the effective interest method over the lives of the related debt agreements. FOREIGN CURRENCY TRANSACTIONS The functional currency of the Company’s Canadian and South American subsidiaries is the U.S. dollar. Gains or losses resulting from transactions denominated in Canadian and South American currencies are included in Foreign currency transaction gain, net in the Company's Consolidated Statements of Comprehensive (Loss) Income . USE OF ESTIMATES The preparation of the Company’s consolidated financial statements in conformity with United States generally accepted accounting principles 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 depletion, depreciation, amortization and accretion calculations, future cash flows from long-lived assets, fair value of long-lived assets, and fair value of derivatives. Actual results could differ from these estimates. RECENT ACCOUNTING STANDARDS On May 28, 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers , which requires an entity to recognize the amount of revenue it expects to be entitled to for the transfer of promised goods or services to customers. The effective date of the new standard has been deferred by one year to January 1, 2018, and will replace most existing revenue recognition guidance in U.S. GAAP. The standard permits the use of either the retrospective or cumulative effect transition method. The Company is evaluating the effect that ASU 2014-09 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early application is not permitted. On April 7, 2015, as part of their initiative to simplify and reduce complexity in the financial statements, the FASB issued ASU 2015-03, Interest - Imputation, (Subtopic 835-30): Simplifying the Presentation of Debt Issuance. This ASU requires the debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the debt liability. Also, requiring retrospective application for all prior periods presented in the financial statements and a disclosure of the nature of and reason for the change in accounting principle, the transition method, a description of the prior-period information that has been retrospectively adjusted and the effect of the change on the financial statement line items. ASU 2015-03 is effective for financial statements issued for fiscal years beginning after December 31, 2015, and interim periods within those fiscal years. The Company is evaluating the effect that ASU 2015-03 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early adoption is permitted for financial statements that have not been previously issued. On November 20, 2015, FASB issued Accounting Standards Update 2015-17, Balance Sheet Classification of Deferred Taxes (ASU 2015-17). The ASU is part of the FASB’s simplification initiative aimed at reducing complexity in accounting standards. The new guidance requires that all deferred tax assets and liabilities, along with any related valuation allowance, be classified as noncurrent on the balance sheet. The guidance is effective for annual periods beginning after December 15, 2016, including interim periods within those years. Early application is permitted. The Company adopted ASU 2015-17 prospectively at December 31, 2015 and prior periods were not retrospectively adjusted. The adoption of ASU 2015-17 has no financial impact to the Company other than to decrease current deferred tax assets resulting in a reduction of working capital.

Sales

Sales	12 Months Ended
	Dec. 31, 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 customers with whom the Company has established trading relationships. Refined 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 are included in revenues from Mine Production. For the respective years 2015, 2014 and 2013 , sales of by-products (gold, nickel, mined rhodium, copper and silver) totaled $23.1 million , $29.6 million and $27.1 million . In July 2014, the Company executed five -year supply and refining agreements with Johnson Matthey (JM). Under the terms of these agreements, JM has an exclusive five -year right to refine all of the PGM filter cake the Company produces at its Columbus, Montana facilities. JM also has the right to purchase all of the Company's mine production of palladium and platinum at competitive market prices (except for platinum sales currently under the Company's sales agreement with Tiffany & Co., which are specifically excluded from the JM agreements) and has the right to bid for any recycling volumes the Company has available. Other provisions of the agreements include a good-faith effort by JM to assist in growing the Company's recycling volumes and the sharing of market intelligence to the extent permitted by law. The Company has the right to exit the JM PGM supply arrangement in return for the payment of a nominal fee. In addition, the Company, in its sole discretion, may elect to terminate the refining arrangement after four years . During 2015 , all Company sales of mined PGMs were either in the spot market or under mutually agreed supply agreements. PGM RECYCLING The Company purchases spent catalyst and other industrial source materials from third-parties and processes this material within its facilities in Columbus, Montana to recover palladium, platinum and rhodium for sale. It also accepts material supplied from third-parties on a tolling basis, processing it for a fee and returning the recovered metals to the supplier. The Company has entered into sourcing arrangements for recycling material with various suppliers. Under these sourcing arrangements as currently structured, the Company may advance cash against a shipment of material shortly before actually receiving the physical shipment at the Company's processing facilities 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 it 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. OTHER In addition to Mine Production and PGM Recycling metal sales, the Company makes other open market purchases of PGMs from time to time for resale to third parties. The Company recognized other revenue of $5.9 million in 2014, including $5.3 million for metal acquired in the open market for immediate resale to third parties. There were no comparable acquisitions in the open market during 2015 or 2013.

Asset Impairment

Asset Impairment	12 Months Ended
	Dec. 31, 2015
Asset Impairment [Abstract]
Asset Impairment	ASSET IMPAIRMENT In accordance with the FASB Accounting Standards Codification 360, Property Plant and Equipment , (ASC 360-10), the Company reviews and evaluates its long-lived assets for impairment when events and changes in circumstances indicate that the related carrying amounts of such assets may not be recoverable and may exceed their fair value. For purposes of determining impairment, assets are grouped at the lowest level for which identifiable cash flows (including estimated future cash flows from non-operating properties) are largely independent of the cash flows of other groups of assets and liabilities. Marathon 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. At June 30, 2015, the Company recorded an impairment charge of $46.8 million (before-tax) against the carrying value of the Marathon mineral properties in Canada, reducing its carrying value to an estimated fair value of $8.6 million . 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 area and impaired those properties by approximately $0.5 million at December 31, 2014. The Company recognized impairment to its Marathon properties in Canada at December 31, 2013. In assessing impairment at Marathon, the Company segregated the assets associated with the proposed Marathon PGM-copper development project from the Company’s other nearby exploration holdings, which are in a less advanced stage of evaluation and therefore not yet integral to the proposed mining operation. Both asset groups were separately considered for impairment because in the Company’s view the value of the exploration properties was likely dependent upon the underlying viability of the Marathon PGM-copper development project. During the fourth quarter of 2013, the detailed engineering feasibility study being undertaken on the Marathon project (following on an earlier study last revised in March 2012) reached a stage where the project economics could be reviewed. Several adverse changes emerged from the new study: • Less favorable third-party off-take terms (including the effect of lower concentrate grades and higher shipping costs); • Higher operating costs; • Higher initial capital cost; and • Reductions in estimated palladium grades in a portion of the ore reserves. The Company concluded that the unfavorable changes identified in the updated feasibility study collectively constituted an “indicator of impairment” that could indicate the carrying value of Marathon, as recorded on the books of the Company at December 31, 2013 (pre-impairment), was unrecoverable. Consequently, the Company was required by accounting principles to determine if the carrying value of the Marathon assets exceeded their expected future undiscounted cash flows and the fair value of the assets. The Company initiated a process, with assistance from a qualified third-party consulting firm, to validate the preliminary economics in the new feasibility study and determine if the carrying value of the assets was more likely than not recoverable. This consulting firm worked with the Company and the engineering firms that prepared the feasibility study, reviewing the assumptions and the cash flows included in the project financial model for reasonableness. The consulting firm’s preliminary report concluded that, more likely than not, if the Marathon PGM-copper project were developed by the Company as planned, the net undiscounted cash flows from the project would be insufficient to recover its pre-impairment carrying value. The Company concurred with this conclusion and, with the continuing assistance of the third-party consulting firm, proceeded to estimate the fair value of its long-lived Marathon assets. In so doing, the Company considered the net present values indicated by the financial model over a range of metal prices (these values were consistently negative using what the Company judged to be a reasonable discount rate), as well as taking into account appropriate comparable sales transactions, adjusted for relative scale and risk, and a value using the appraised value method, based on exploration spending. As a result, in aggregate the Company wrote down the carrying value of its Marathon assets at December 31, 2013, from $228.6 million to $57.3 million , with a corresponding $171.4 million (before-tax) charge that included a charge against mineral properties and mine development of $170.5 million , and against depreciable fixed assets of $0.8 million . Because the Marathon economics at present do not support proceeding with development, the Company no longer is reporting proven and probable ore reserves at Marathon or accounting for Marathon as a development-stage project. Altar The Company regards the Altar project, comprised of contiguous mineral exploration properties situated in Argentina that likely would be mined together as a unit, as a single long-lived asset in considering impairment. During the third quarter of 2013, the Company identified certain events that necessitated the testing of recoverability of the carrying value of the asset. In view of the significant scale of the Altar project, the Company believed it was unlikely that it could develop the project without involving other partners. In assessing recoverability, the Company took into account the effects on the Altar project of continuing deterioration in the legal and business climate in Argentina, coupled with industry announcements of investment cutbacks and the deferral of certain projects in the vicinity of the Altar property, a significant shift away from large greenfield projects by the global mining industry, and the ongoing technical review of the Altar project. Considering these events individually and in the aggregate, the Company concluded that “indicators of potential impairment” had occurred during the 2013 third quarter, requiring the Company to assess whether its investment in the Altar mineral property was recoverable. These adverse changes required the Company to assess whether it reasonably expected to generate future undiscounted cash flows sufficient to recover its investment in the Altar mineral property, utilizing the potential development scenarios under current consideration. These scenarios included developing the project under various capital sensitivity cases, inviting third-party investment in portions of the project, abandoning the project outright, and considering a long-term sale. Probability weighting these scenarios for the Altar mineral property, which were developed in conjunction with the ongoing technical reviews noted above, the Company determined that the probability-weighted undiscounted future cash flows from the Altar mineral property were more likely than not, not sufficient to recover the carrying value of the assets at September 30, 2013. Having made such determination, the Company undertook to determine an estimate of the fair value of the Altar assets. This effort, for which the Company engaged the assistance of a qualified third-party valuation expert, included examining recent comparable transactions for similar undeveloped mineral properties and market multiples for similar projects. Taking the result of this analysis into account, the Company recorded an impairment at September 30, 2013, of $290.4 million (before-tax) in the carrying value of the Altar mineral property, reducing the carrying value to its estimated fair value of $102.0 million . Subsequently, the Company reviewed the recoverability of the Altar carrying value at December 31, 2013, and for each reporting period thereafter and has concluded that no further reduction to the carrying value of the Altar property is indicated to date. Assumptions underlying future cash flows associated with the Company’s long-lived assets are subject to risks and uncertainties. Future changes in such factors as supply and demand fundamentals, metals prices, recoverable reserve estimates, legal requirements and actual operating performance could have a material effect on the Company’s ability to recover the carrying amounts of its long-lived assets, potentially resulting in additional impairment charges. In the case of the Altar and Marathon exploration properties (for which future expected cash flows are difficult to estimate), a pattern of declining realized prices for sales of comparable mineral properties could provide an indication of impairment.

Noncontrolling Interest

Noncontrolling Interest	12 Months Ended
	Dec. 31, 2015
Noncontrolling Interest [Abstract]
Noncontrolling Interest	NONCONTROLLING INTEREST Since 2012, a subsidiary of Mitsubishi Corporation (Mitsubishi) has held a 25% interest in the Company's wholly-owned subsidiary, Stillwater Canada Inc (SCI), which holds the Marathon PGM-copper assets. Mitsubishi paid $81.25 million in cash for its 25% interest and contributed an additional $13.6 million to satisfy its 25% share of the venture's initial cash call. According to the acquisition terms, Mitsubishi was responsible for funding its 25% share of operating, capital and exploration expenditures on the Marathon properties and also had a first right to purchase up to 100% of Marathon's future PGM production at a relatively small discount to market. The change in the parent company's equity as a result of the sale of the noncontrolling interest in SCI was an increase to Additional 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 income (loss) in each period in arriving at Net income (loss) attributable to common stockholders . The reported Net loss attributable to noncontrolling interest for the years ended December 31, 2015, 2014 and 2013 was $11.8 million and $1.4 million , and $31.9 million , respectively. The reported Net loss attributable to noncontrolling interest for the year ended December 31, 2015 reflects Mitsubishi's share of the impairment loss taken on the carrying value of the Marathon assets at June 30, 2015. The noncontrolling interest portion of the impairment loss was $11.7 million (before-tax). In the fourth quarter of 2015, the Company purchased Mitsubishi's 25% interest in SCI and related properties for a total cash consideration of $5.2 million . The total cash consideration was comprised of $1.0 million in cash and the equivalent of 25% of the total cash and cash equivalents held by SCI.

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS The Company uses derivative financial instruments to manage certain of its exposures to changes in PGM market commodity prices. COMMODITY DERIVATIVES PGM Recycling The Company customarily enters into fixed forward sales relating to PGM recycling of catalysts and other industrial sourced materials. Under these fixed forward transactions, the Company agrees to deliver a stated quantity of metal on a specific future date at a price stipulated in advance. The Company uses fixed forward transactions to set in advance the pricing for metals acquired and processed in its recycling segment. The metals from PGM recycled materials are sold forward at the time of purchase and delivered against the fixed forward contracts when the ounces are recovered. Because this forward price is also used to set the acquisition price the Company pays for recycling materials, this arrangement significantly reduces exposure to PGM price volatility. The Company believes such transactions qualify for the exception to hedge accounting treatment and 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 December 31, 2015 , will settle at various periods through June 2016 . The Company has credit agreements with its major trading partners that provide for margin deposits in the event that forward prices for metals exceed the Company’s hedged prices by a predetermined margin limit. At December 31, 2015 , 2014 and 2013, no margin deposits were outstanding or due. The following is a summary of the Company’s outstanding commodity derivatives in its PGM Recycling Segment at December 31, 2015 : PGM Recycling: Fixed Forward Contracts Platinum Palladium Rhodium Settlement Period Ounces Average Price/Ounce Ounces Average Price/Ounce Ounces Average Price/Ounce First Quarter 2016 17,780 $ 921 28,124 $ 596 4,727 $ 727 Second Quarter 2016 2,321 $ 863 2,738 $ 554 658 $ 671 Mine Production The Company was not a party to any derivative instruments involving its mined production during 2015, 2014 or 2013.

Share Compensation Plans

Share Compensation Plans	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share Compensation Plans	SHARE COMPENSATION PLANS EQUITY PLANS The Company sponsors equity plans (the “Plans”) that enable the Company to grant equity based compensation to employees and non-employee directors. In total approximately 11.6 million shares of common stock have been authorized under the Plans, including approximately 5.0 million , 5.2 million and 1.4 million authorized shares for 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 grant under the 2012 Equity Incentive Plan at December 31, 2015 . The Compensation Committee of the Board 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’ options and restricted stock units vest in equal annual installments over a three year period after date of grant. Options expire ten years after the date of grant. NONVESTED SHARES Time-Based Restricted Stock Unit Awards Time-based restricted stock unit awards provide the participant with the right to receive a number of shares of the Company's common stock upon vesting of the awards provided the participant is employed by the Company on the vesting date. Time-based awards are valued using the Company's common stock price on the date of grant. Time-based awards are not entitled to any dividend equivalents with respect to the restricted stock units nor any dividends on stock that may be delivered in settlement of the restricted stock units unless and until the stock is issued in settlement of restricted stock units. Nonvested time-based share activity during 2015 , 2014 and 2013 , is detailed in the following table: Year ended December 31, Nonvested Shares Weighted- Average Grant- Date Fair Value Nonvested time-based shares at December 31, 2012 1,278,590 $ 14.38 Granted 544,122 13.64 Vested (1) (1,791,040 ) 14.19 Forfeited (615 ) 13.99 Nonvested time-based shares at December 31, 2013 31,057 $ 11.55 Granted 348,056 14.68 Vested (158,412 ) 13.84 Forfeited (35,954 ) 14.22 Nonvested time-based shares at December 31, 2014 184,747 $ 13.80 Granted 127,407 14.17 Vested (114,129 ) 13.91 Forfeited (11,370 ) 14.21 Nonvested time-based shares at December 31, 2015 186,655 $ 13.97 (1) Pursuant to the terms of the Company's Equity Plans, the change in control that occurred in the second quarter of 2013 resulted in all outstanding nonvested shares granted under those Equity Plans immediately becoming fully vested. Total compensation expense, included within General and administrative in the Company's Consolidated Statements of Comprehensive (Loss) Income related to grants of time-based nonvested shares for the years ended December 31, 2015 and 2014 was $1.6 million and $2.6 million , respectively. Compensation expense for the year ended December 31, 2013, totaled $13.7 million , of which $4.6 million is included in General and administrative in the Company's Consolidated Statements of Comprehensive (Loss) Income and $9.1 million (non-cash charge) resulting from the triggering of the change in control provisions under the 2004 and 2012 Equity Incentive Plans is recorded as Accelerated equity based compensation for change in control in the Company's Consolidated Statements of Comprehensive (Loss) Income . Performance-Based Restricted Stock Unit Awards A performance-based restricted stock unit award provides the participant with the right to receive a number of shares of the Company's common stock depending on achievement of specific measurable performance criteria. The number of shares earned is determined at the end of each performance period, generally three years, based on the actual performance criteria predetermined by the Compensation Committee at the time of grant. In the period 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. In the event the Company determines it is no longer probable that it will achieve the minimum performance criteria specified in the Plan, the Company reverses all of the previously recognized compensation expense in the period such a determination is made. In 2014, the Company began granting performance-based stock unit awards under its Long Term Incentive Plan (LTIP). The payout of the awards is 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. Market-based performance shares 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 share 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 shares for the years ended December 31, 2015 and 2014 was $1.3 million and $1.5 million , respectively. Performance-based awards are not entitled to any dividend equivalents with respect to the restricted stock units nor any dividends on stock that may be delivered in settlement of the restricted stock units unless and until the stock is issued in settlement of restricted stock units. Nonvested performance-based share activity during 2015 and 2014 is detailed in the following table: Nonvested Shares Weighted- Average Grant- Date Fair Value Nonvested performance-based shares at January 1, 2014 — $ — Granted * 223,412 15.69 Vested — — Forfeited (9,176 ) 15.69 Nonvested performance-based shares at December 31, 2014 214,236 $ 15.69 Granted * 170,078 14.92 Vested — — Forfeited (5,037 ) 15.34 Nonvested performance-based shares at December 31, 2015 379,277 $ 15.34 * The number of performance-based shares granted is based on the target award amounts in the performance share grant agreements. The following table presents the compensation expense of the nonvested shares outstanding at December 31, 2015 , to be recognized over the remaining vesting periods: (In thousands) Time-based shares Performance -based shares 2016 $ 1,522 1,491 2017 631 808 2018 12 — Total $ 2,165 $ 2,299 STOCK OPTIONS Effective March 2011, the Company ceased offering stock options 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. Historically, the Company recognized compensation expense associated with its stock option grants based on their fair market value on the date of grant as determined using a Black-Scholes option pricing model. The Company experienced a change in control event in the second quarter of 2013 resulting in all outstanding, unvested stock options granted under the 2004 and 2012 Equity Plans becoming fully vested. Due to the accelerated vesting of all outstanding stock options in the second quarter of 2013, the Company recognized the remaining expense of $41,400 in 2013. The compensation expense is recorded in General and administrative in the Company's Consolidated Statements of Comprehensive (Loss) Income . Stock option activity for the years ended December 31, 2015 , 2014 and 2013 , is summarized as follows: Year Ended December 31, Shares Weighted Average Exercise Price Options outstanding at December 31, 2012 242,519 $ 10.57 Options exercisable at December 31, 2012 224,933 10.08 2013 Activity Options exercised (25,471 ) 5.02 Options canceled / forfeited (17,757 ) 6.07 Options outstanding and exercisable at December 31, 2013 199,291 $ 11.68 2014 Activity Options exercised (105,047 ) 9.54 Options canceled / forfeited (13,100 ) 14.32 Options outstanding and exercisable at December 31, 2014 81,144 $ 14.03 2015 Activity Options exercised (6,492 ) 9.16 Options canceled / forfeited (17,542 ) 11.01 Options outstanding and exercisable at December 31, 2015 57,110 $ 15.51 The following table summarizes additional stock option activity: (In thousands) 2015 2014 2013 Intrinsic value of exercisable options $ 9 $ 207 $ 469 Cash received from options exercised $ 60 $ 993 $ 128 Intrinsic value of options exercised $ 25 $ 674 $ 205 Compensation expense (recorded in General and administrative) $ — $ — $ 41 The following table summarizes information for outstanding and exercisable options at December 31, 2015 : Options Outstanding and Exercisable Range of Exercise Price Number Outstanding and Exercisable Weighted Average Remaining Contract Life Weighted Average Exercise Price $ 4.17 - $11.50 9,209 2.8 $ 8.69 $11.51 - $12.82 9,117 2.7 $ 12.15 $12.83 - $15.45 9,117 2.5 $ 13.78 $15.46 - $18.56 8,642 4.2 $ 16.80 $18.57 - $19.55 10,600 4.9 $ 19.05 $19.56 - $24.55 10,425 4.3 $ 21.34 57,110 3.6 $ 15.51 DEFERRAL PLANS The Company suspended new deferrals into its Non-Employee Directors’ Deferral Plan effective mid-2014. The Plan previously allowed non-employee directors to defer all or any portion of the compensation received as directors, in accordance with the provisions of Section 409A of the Internal Revenue Code and associated Treasury regulations. All amounts previously deferred under this Plan are fully vested, and each participant elected the deferral period and form of the compensation (Company common stock including a 20% Company match or cash). Compensation expense under the Plan was $13,500 and $64,200 in 2014 and 2013, respectively. The Company match was made in Company common stock. Independent Director Deferred Share Unit Plan (DSU Plan) The Company's DSU Plan was approved in August 2014. Each year, an independent director may irrevocably elect to defer up to 100% of annual fees (annual cash fees payable by the Company to an independent director with respect to service as a member of the Board). A deferred share unit (DSU) is a compensatory unit which represents a promise by the Company to deliver cash equal to the fair market value of one share of the Company's common stock for each awarded DSU. The DSUs are revalued at the end of each reporting period using the closing price of the Company's common stock on the last trading day of the reporting period. Upon separation of service from the Board, an independent director's entire account balance is distributed in a lump sum cash payment. The Company recognized compensation expense of approximately $0.6 million and $0.5 million in 2015 and 2014, respectively. The following table summarizes the activity for the DSU Plan for the years ended December 31, 2015 and 2014: DSUs Fair market value of DSUs (1) Closing Share Price Granted 30,420 $ 18.69 Distributions (5,070 ) $ (66,667 ) Liability at December 31, 2014 25,350 $ 373,637 $ 14.74 Granted 37,053 $ 13.22 Liability at December 31, 2015 62,403 $ 534,804 $ 8.57 (1) Fair market value of DSUs includes effect of fractional shares. Nonqualified Deferred Compensation Plan (NQDC Plan) The Company's NQDC Plan allows certain key personnel of the Company to defer up to 60% of their salaries and up to 100% of other cash compensation and vested restricted stock units in accordance with the provisions of Section 409A of the Internal Revenue Code and associated Treasury regulations. All amounts deferred under this plan are fully vested, and each participant elects the deferral period and form of the compensation (Company common stock or cash). For each Plan year, the Company matches the amount of compensation deferred during that year up to a maximum of 8% of the participant’s total compensation for the calendar year. Compensation expense deferred in cash was approximately $0.3 million , $0.2 million and $0.2 million in 2015, 2014 and 2013 , respectively. Compensation expense deferred upon the vesting of common stock was $12,620 for the year ended December 31, 2015. There were no deferrals upon the vesting of common stock for the years ended December 31, 2014 and 2013. EMPLOYEE BENEFIT PLANS The Company has two savings plans, which qualify under section 401(k) of the U.S. Internal Revenue Code, covering essentially all non-bargaining and bargaining employees. Employees may elect to contribute up to 60% of their eligible compensation, subject to the Employee Retirement Income Security Act of 1974 (ERISA) limitations. The Company is required to make matching contributions equal to 100% of the employee’s contribution up to 8% of the employee’s compensation. Prior to September 1, 2015 matching contributions were made with common stock of the Company. During 2015, 2014 and 2013 , the Company issued approximately 0.6 million , 0.7 million and 0.9 million shares of common stock, respectively, with a market value on the respective grant dates of $7.5 million , $10.3 million and $10.3 million , respectively, to match employees’ contributions. Effective, September 1, 2015, the Company began matching contributions in cash. The Company made cash contributions of $3.9 million into the plans in 2015.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The components of the Company’s deferred income tax liabilities (assets) are comprised of the following temporary differences and carryforwards at December 31, 2015 , and 2014 . (In thousands) 2015 2014 Mine development and mineral interests-US $ 86,905 $ 98,204 Mineral interests-South America 13,697 20,844 Long-term debt 27,835 42,986 Total deferred tax liabilities $ 128,437 $ 162,034 Noncurrent liabilities (9,896 ) (10,703 ) Mine development and mineral interests-Canada (15,900 ) (1,214 ) Property and equipment (16,440 ) (15,683 ) Current liabilities (18,844 ) (21,301 ) Long-term investments (2,989 ) (3,158 ) Inventory (993 ) (933 ) AMT credit and other carryforwards (34,383 ) (30,956 ) Exploration (3,578 ) (4,610 ) Net operating loss (NOL) and other carryforwards (39,244 ) (48,444 ) Total deferred tax assets $ (142,267 ) $ (137,002 ) Valuation allowance 36,591 22,812 Net deferred tax assets (105,676 ) (114,190 ) Net deferred tax liabilities $ 22,761 $ 47,844 On November 20, 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2015-17, Balance Sheet Classification of Deferred Taxes (ASU 2015-17). The ASU is part of the FASB’s simplification initiative aimed at reducing complexity in accounting standards. The new guidance requires that all deferred tax assets and liabilities, along with any related valuation allowance, be classified as noncurrent on the balance sheet. The guidance is effective for annual periods beginning after December 15, 2016, including interim periods within those years. Early application is permitted. The Company adopted ASU 2015-17 prospectively at December 31, 2015 and prior periods were not retrospectively adjusted. The adoption of ASU 2015-17 has no financial impact to the Company other than to decrease current deferred tax assets, resulting in a reduction of working capital. Upon the adoption of ASU 2015-17, all deferred tax assets and liabilities are now classified as non-current regardless of their classification on the balance sheet and the timing of their anticipated reversal. The non-current net deferred tax liability balance at December 31, 2015 was $22.8 million , and is included in the long-term liabilities, net in the Company's Consolidated Balance Sheets . At December 31, 2014, there was a current deferred tax asset balance of $21.1 million and a non-current deferred tax liability balance of $68.9 million . 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 provided 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 NOLs and other carryforwards for 2015 above represent $24.4 million from U.S. operations and $14.8 million from foreign operations. The NOLs for 2014 above represent $34.6 million from U.S. operations and $13.9 million from foreign operations. Reconciliation of the income tax (benefit) provision at the applicable statutory income tax rates to the effective rate is as follows: December 31, (In thousands) 2015 2014 2013 (Loss) income before income taxes $ (36,069 ) $ 85,141 $ (395,726 ) Income tax (benefit) provision at statutory rates (12,624 ) 29,799 (138,504 ) State income tax expense, net of federal benefit 50 3,553 3,995 Percentage depletion (5,366 ) (17,302 ) (8,786 ) Foreign currency transaction loss (gain), net 3,471 (1,353 ) 31,605 Compensation related adjustment 59 6 359 Change in valuation allowance 13,780 2,127 5,595 Return-to-provision (1,259 ) 92 1,097 Impact of foreign operations (2,981 ) (52 ) 8,895 Rate adjustment (7,290 ) (96 ) 1,503 Other (173 ) (516 ) 588 Net income tax (benefit) provision $ (12,333 ) $ 16,258 $ (93,653 ) At December 31, 2015 , the Company had approximately $105.2 million of regular federal tax net operating loss carryforwards in the U.S. expiring from 2020 through 2035. 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 had $32.5 million of alternative minimum tax credit carryforwards which will not expire and $1.9 million in general business credits expiring during 2029 to 2035. The Company had approximately $3.3 million of state tax net operating loss carryforwards expiring during 2020 through 2029. The Company also had $53.8 million of foreign net operating loss carryforwards. The foreign net operating losses expire as follows: $20.5 million during 2016 to 2020 and $25.0 million during 2024 to 2035. Currently, $8.3 million of foreign net operating losses have an indefinite life. Cash payments for state income taxes were made in 2015, 2014 and 2013 in the amounts of $2.4 million , $15.3 million and $0.1 million , respectively. The Company made U.S. federal tax payments in the amounts of $11.0 million , $11.1 million , $5.2 million in 2015, 2014, and 2013, respectively. The Company had a net tax receivable of $13.2 million relating to current and prior year anticipated U.S. and state tax filings. The Company’s policy is to recognize interest and penalties on unrecognized tax benefit (provision) in Income tax benefit (provision) in the Company's Consolidated Statements of Comprehensive (Loss) Income . The Company does not have any uncertain tax benefits at December 31, 2015 and 2014. There were no interest and penalties accrued at December 31, 2015 or 2014. The interest and penalties accrued for December 31, 2013 were $2.1 million . The tax years subject to examination by the taxing authorities are the years ended December 31, 2014 , 2013 and 2012 , although, net operating loss and credit carryforwards from all years are subject to examination and adjustments for three years following the year in which utilized. The income tax (benefit) provision is comprised of the following: December 31, (In thousands) 2015 2014 2013 Current Federal $ 3,203 $ 13,902 $ 9,740 State 2,175 6,947 5,152 Current income tax $ 5,378 $ 20,849 $ 14,892 Deferred Federal (1,474 ) (1,577 ) 5,278 State (14,510 ) (2,462 ) 252 Foreign (1,727 ) (552 ) (114,075 ) Deferred income tax benefit (17,711 ) (4,591 ) (108,545 ) Income tax (benefit) provision $ (12,333 ) $ 16,258 $ (93,653 ) The components of (loss) income before income tax (benefit) provision by tax jurisdiction for the years ended December 31, 2015, 2014 and 2013 were as follows: (In thousands) 2015 2014 2013 United States $ 10,574 $ 88,281 $ 61,671 Foreign (46,643 ) (3,140 ) (457,397 ) Loss / income before income tax (benefit) provision $ (36,069 ) $ 85,141 $ (395,726 )

Comprehensive (Loss) Income

Comprehensive (Loss) Income	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Comprehensive (Loss) Income	COMPREHENSIVE (LOSS) INCOME Comprehensive (loss) / income consists of earnings items and other gains and losses affecting stockholders’ equity that are excluded from current net income. At December 31, 2015, 2014 and 2013 , such items consisted of unrealized gains / losses on available-for-sale marketable securities and deferred compensation. The following summary sets forth the changes in Accumulated other comprehensive (loss) income during 2015, 2014 and 2013 : (In thousands) Available-for-sale marketable securities Deferred Compensation Accumulated Other Comprehensive (Loss) Income Balance at December 31, 2012 $ (99 ) $ — $ (99 ) Change in value, net of tax 105 — 105 Balance at December 31, 2013 6 — 6 Change in value, net of tax 11 — 11 Balance at December 31, 2014 17 — 17 Change in value, net of tax (384 ) 170 (214 ) Balance at December 31, 2015 $ (367 ) $ 170 $ (197 )

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 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 aggregated, as both have similar products, processes, customers, distribution methods and economic characteristics. The PGM Recycling segment is engaged in the recycling of spent catalyst material to recover the PGMs contained in the material. The Company either purchases the catalyst material processed by the PGM Recycling segment from third-party suppliers for its own account and sells the recovered metals directly, or it accepts catalyst material supplied 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 mainly 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. In 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. In the fourth quarter of 2014 the Company recorded an impairment charge of approximately $0.5 million against certain real estate properties owned by the Company in the town of Marathon. In the fourth quarter of 2013, the Company took an impairment charge of $171.4 million on the Marathon properties. At December 31, 2013, the Company ceased reporting proven and probable ore reserves at Marathon or accounting for Marathon as a development-stage project. In general, the Company now expenses Marathon costs in the period in which they are incurred. See " Note 4 - Asset Impairment " for more information. The South American Properties segment consists of the Peregrine Metals Ltd. assets. The principal Peregrine asset is the Altar property, an exploration-stage copper-gold resource located in the San Juan province of Argentina. In the third quarter of 2013, the Company took an impairment charge of $290.4 million (before-tax) on the Peregrine properties. See " Note 4 - Asset Impairment " for more information. 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) Mine Production PGM Recycling Canadian Properties South American Properties All Other Total Year ended December 31, 2015 Revenues $ 415,774 $ 310,156 $ — $ — $ 400 $ 726,330 Depletion, depreciation and amortization $ 64,200 $ 949 $ — $ — $ — $ 65,149 General and administrative expenses $ — $ — $ 1,146 $ 504 $ 32,383 $ 34,033 Interest income $ — $ 1,653 $ 7 $ 27 $ 1,268 $ 2,955 Interest expense $ — $ — $ — $ — $ 20,187 $ 20,187 Income (loss) before impairment charge and income taxes $ 57,618 $ 10,151 $ (1,910 ) $ 2,218 $ (57,374 ) $ 10,703 Impairment charge $ — $ — $ 46,772 $ — $ — $ 46,772 Income (loss) after impairment charge, before income taxes $ 57,618 $ 10,151 $ (48,682 ) $ 2,218 $ (57,374 ) $ (36,069 ) Capital expenditures $ 100,725 $ 327 $ 46 $ — $ 6,336 $ 107,434 Total assets $ 613,498 $ 40,757 $ 26,517 $ 103,774 $ 497,664 $ 1,282,210 (In thousands) Mine Production PGM Recycling Canadian Properties South American Properties All Other Total Year ended December 31, 2014 Revenues $ 536,010 $ 401,684 $ — $ — $ 5,925 $ 943,619 Depletion, depreciation and amortization $ 66,387 $ 1,019 $ — $ — $ — $ 67,406 General and administrative expenses $ — $ — $ 3,251 $ 337 $ 31,479 $ 35,067 Interest income $ — $ 2,535 $ 6 $ 68 $ 942 $ 3,551 Interest expense $ — $ — $ 1 $ — $ 22,718 $ 22,719 Income (loss) before impairment charge and income taxes $ 136,990 $ 11,719 $ (4,581 ) $ 2,600 $ (61,037 ) $ 85,691 Impairment charge $ — $ — $ 550 $ — $ — $ 550 Income (loss) after impairment charge, before income taxes $ 136,990 $ 11,719 $ (5,131 ) $ 2,600 $ (61,037 ) $ 85,141 Capital expenditures $ 115,147 $ 181 $ — $ 45 $ 4,309 $ 119,682 Total assets $ 596,653 $ 65,513 $ 75,250 $ 106,947 $ 554,964 $ 1,399,327 (In thousands) Mine Production PGM Recycling Canadian Properties South American Properties All Other Total Year ended December 31, 2013 Revenues $ 478,918 $ 560,588 $ — $ — $ — $ 1,039,506 Depletion, depreciation and amortization $ 58,201 $ 1,116 $ — $ — $ — $ 59,317 General and administrative expenses $ — $ — $ 1,112 $ 2,549 $ 42,916 $ 46,577 Interest income $ — $ 3,375 $ 20 $ 184 $ 902 $ 4,481 Interest expense $ — $ — $ — $ — $ 22,957 $ 22,957 Income (loss) before impairment charge and income taxes $ 106,122 $ 35,463 $ (4,255 ) $ 8,845 $ (80,146 ) $ 66,029 Impairment charge $ — $ — $ 171,338 $ 290,417 $ — $ 461,755 Income (loss) after impairment charge, before income taxes $ 106,122 $ 35,463 $ (175,593 ) $ (281,572 ) $ (80,146 ) $ (395,726 ) Capital expenditures $ 108,527 $ 330 $ 12,380 $ 101 $ 7,691 $ 129,029 Total assets $ 553,153 $ 80,555 $ 83,800 $ 109,960 $ 519,212 $ 1,346,680

Investments

Investments	12 Months Ended
	Dec. 31, 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 market value in the financial statements with unrealized gains or losses recorded in Other comprehensive (loss) 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. Amounts reclassified out of Other comprehensive (loss) income during the periods ended December 31, 2015 , and 2014 were insignificant. The amortized cost, gross unrealized gains, gross unrealized losses, and fair market value of available-for-sale investment securities by major security type and class of security at December 31, are as follows: (In thousands) Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value 2015 Federal agency notes $ 285,276 $ — $ (519 ) $ 284,757 Commercial paper 31,730 — (58 ) 31,672 Subtotal 317,006 — (577 ) 316,429 Mutual funds 482 261 — 743 Total $ 317,488 $ 261 $ (577 ) $ 317,172 2014 Federal agency notes $ 143,132 $ 40 $ (33 ) $ 143,139 Commercial paper 108,371 1 (257 ) 108,115 Subtotal 251,503 41 (290 ) 251,254 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 . Included in the investments balance at December 31, 2015 is $18.5 million which has been reserved as collateral on the Company's undrawn letters of credit of approximately $17.5 million . The maturities of available-for-sale securities at December 31, 2015 , are as follows: (In thousands) Amortized cost Fair market value Federal agency notes Due in one year or less $ 219,748 $ 219,581 Due after one year through two years 65,528 65,176 Total $ 285,276 $ 284,757 Commercial paper Due in one year or less $ 20,490 $ 20,472 Due after one year through two years 11,240 11,200 Total $ 31,730 $ 31,672 The Company has long-term investments in several Canadian junior exploration companies, recorded on the balance sheet at cost. The Company determined that its long-term investments were other than temporarily impaired and recorded a loss of $0.4 million and $0.1 million for the years ended December 31, 2015 , and 2014 , respectively. At December 31, 2015 , these long-term investments totaled $0.5 million and are recorded in Other noncurrent assets on the Company's Consolidated Balance Sheets .

Inventories

Inventories	12 Months Ended
	Dec. 31, 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 during 2015 and 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 recycled PGM 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 at December 31, consisted of the following: (In thousands) 2015 2014 Metals inventory Raw ore $ 4,234 $ 4,984 Concentrate and in-process 43,727 48,712 Finished goods 32,618 49,885 $ 80,579 $ 103,581 Materials and supplies 21,493 26,726 Total inventory $ 102,072 $ 130,307

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Common Share	EARNINGS PER COMMON SHARE Basic (loss) earnings per share attributable to common stockholders is computed by dividing net earnings available to common stockholders by the weighted average number of common shares outstanding during the period. Diluted (loss) 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. In calculating earnings per share attributable to common stockholders, reported consolidated net income (loss) attributable to common stockholders is adjusted for the interest expense, net of capitalized interest (including amortization expense of deferred debt fees) and the related income tax effect, in computing basic and diluted earnings per share attributable to common stockholders. The Company currently has only one class of equity shares outstanding. Potential dilutive common shares include those associated with outstanding stock options, restricted stock units, performance shares and convertible debentures. For periods in which the Company reports a net loss attributable to common stockholders, potential dilutive common shares are excluded, as their conversion and exercise would be anti-dilutive. The Company reported a net loss attributable to common stockholders, for the years ended December 31, 2015 and 2013 resulting in 182,546 and 98,218 , respectively, potentially dilutive shares being excluded from the computation of diluted weighted average shares outstanding. Outstanding options to purchase 34,259 weighted shares of common stock were excluded from the computation of diluted earnings per share attributable to common stockholders for 2014, due to the average market price at the end of the period being lower than the exercise price, and therefore the effect would have been antidilutive. The reconciliation showing the computation of basic and diluted shares and the related impact on income for the year ended December 31, 2014 is shown in the following table: Year Ended December 31, 2014 (In thousands, except per share amounts) Income (Numerator) Weighted Average Shares (Denominator) Per Share Amount Basic EPS Net income attributable to common stockholders $ 70,297 119,953 $ 0.59 Effect of Dilutive Securities Stock options — 31 Nonvested shares — 53 Contingently issuable shares — 98 1.875% Convertible Debentures, net of tax — 95 1.75% Convertible Debentures, net of tax and capitalized interest 16,613 36,003 Diluted EPS Net income attributable to common stockholders and assumed conversions $ 86,910 156,233 $ 0.56

Debt and Capital Lease Obligati

Debt and Capital Lease Obligations	12 Months Ended
	Dec. 31, 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 of 1.75% Convertible Debentures, due October 15, 2032. Each $1,000 principal amount of these 1.75% Convertible 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% Convertible Debentures also include an embedded conversion enhancement feature that is equivalent to including with each $1,000 of Convertible Debenture a warrant initially exercisable for 30.2481 shares initially at $16.53 per share (also subject to customary anti-dilution adjustments). The Company, at its election, may settle conversions of the 1.75% Convertible 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% Convertible Debentures at face value plus accrued and unpaid interest on October 15, 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% Convertible Debentures at any time on or after October 20, 2019. The 1.75% Convertible 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% Convertible 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 elected to repurchase $61.6 million of the outstanding principal of the 1.75% Convertible Debentures, due 2032, paying cash of $59.4 million . The Company reduced the debt component by $50.7 million , which included a reduction of the debt discount by $10.9 million . The difference between the book value and the fair value (including $0.7 million of debt and equity issuance costs) of the debt component resulted in a $4.2 million loss, recorded in Loss on extinguishment of debt, net in the Company's Consolidated Statements of Comprehensive (Loss) Income . The 1.75% Convertible Debentures have an effective interest rate of 8.50% and a stated interest rate of 1.75% with interest paid semi-annually. The balance included in long-term debt on the Company's Consolidated Balance Sheets for the years ended December 31, 2015 and 2014, was approximately $258.4 million and $291.1 million , respectively, which is net of unamortized discount of $76.8 million and $105.6 million , respectively. 1.875% CONVERTIBLE DEBENTURES In the third quarter of 2015, the Company repurchased $1.7 million of the outstanding principal of the 1.875% Convertible 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 in the Company's Consolidated Statements of Comprehensive (Loss) Income . The outstanding balance of $0.5 million is reported as a long-term debt obligation at December 31, 2015. Holders of the remaining $0.5 million of outstanding 1.875% Convertible Debentures may require the Company to redeem their 1.875% Convertible 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 corporate events. The Company has the right at its discretion to redeem the remaining outstanding 1.875% Convertible Debentures for cash at any time prior to maturity. EXEMPT FACILITY REVENUE BONDS During 2000, the Company completed a $30.0 million offering of 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 8.00% with interest paid semi-annually. Net discounted proceeds from the offering were $28.7 million , yielding an effective interest 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 accrued and unpaid interest of $40,000 . 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 the maximum line of credit to $125.0 million , incurring additional debt issuance costs of $0.2 million . The Company paid an unused line fee on the committed but unutilized balance under the facility at a rate per annum of 0.375% or 0.5% , depending on utilization of the facility. The Company terminated its $125.0 million asset-backed revolving credit facility on December 31, 2015, incurring expenses and fees of approximately $0.2 million . The following table reflects the amortization of debt issuance costs, interest expense and cash payments for interest on the Company's outstanding debt for the years ended December 31, 2015 , 2014 and 2013: (In thousands) 2015 2014 2013 1.75% Convertible Debentures Amortization of debt issuance costs $ 925 $ 1,120 $ 1,139 Interest expense, net of capitalized interest $ 18,752 $ 19,416 $ 18,261 Reduction in debt issuance costs (repurchase of debt) $ 747 $ — $ — Cash payments for interest $ 6,827 $ 6,943 $ 6,905 1.875% Convertible Debentures Amortization of debt issuance costs $ — $ — $ 195 Interest expense, net of capitalized interest $ — $ 42 $ 684 Cash payments for interest $ 42 $ 42 $ 1,582 Asset-Backed Revolving Credit Facility Amortization of debt issuance costs $ 539 $ 272 $ 272 Fees $ 1,168 $ 1,026 $ 1,082 Exempt Facility Revenue Bonds, Series 2000 Amortization of debt issuance costs $ — $ 873 $ 58 Interest expense $ — $ 1,240 $ 2,400 Cash payments for interest $ — $ 1,240 $ 2,400 The Company's total current and long-term debt balances at December 31, 2015 and 2014 were as follows: December 31, 2015 December 31, 2014 (In thousands) Current Long-Term Current Long-Term 1.75% Convertible Debentures Aggregate principal $ — $ 335,150 $ — $ 396,750 Debt discount — (76,754 ) — (105,634 ) Debt balance — 258,396 — 291,116 1.875% Convertible Debentures — 524 — 2,245 Capital Lease Obligation 580 — 2,067 580 Small Land Purchase 77 — 77 82 Total debt balances $ 657 $ 258,920 $ 2,144 $ 294,023 CAPITAL LEASE OBLIGATIONS The Company is party to a lease agreement with General Electric Capital Corporation (GECC) covering the acquisition of a tunnel-boring machine 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 $2.2 million on its capital lease obligations for each of the years ended December 31, 2015 and 2014. These cash payments included interest of $0.1 million and $0.2 million , respectively. At December 31, 2015 , the outstanding principal balance under the capital lease was $0.6 million . The following is a schedule of the future minimum lease payments for the capital lease together with the present value of the net minimum lease payments: Year ended December 31, 2015 (In thousands) 2016 minimum lease payments $ 589 Interest at rates ranging from 5.21% to 5.46% (before-tax) (9 ) Net minimum lease payments $ 580 CAPITALIZED INTEREST The Company capitalizes interest incurred on its various debt instruments as a cost of specific and identified projects under development. For the years ended December 31, 2015 , 2014 and 2013, the Company capitalized interest of $6.0 million , $5.1 million and $4.8 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	12 Months Ended
	Dec. 31, 2015
Extractive Industries [Abstract]
Mineral Properties and Mine Development	MINERAL PROPERTIES AND MINE DEVELOPMENT Mineral properties and mine development at December 31, 2015 , and 2014 , consisted of the following: (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 697,781 616,872 East Boulder Mine 220,281 204,483 $ 1,030,542 $ 980,607 Accumulated depletion and amortization (457,311 ) (411,601 ) Total mineral properties and mine development, net $ 573,231 $ 569,006 An impairment charge of $46.8 million (before-tax) was taken against the Marathon mineral properties in the second quarter of 2015, reflecting an estimated fair market value of $8.6 million . See "Note 4 - Asset Impairment" for further information.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment at December 31, consisted of the following: (In thousands) 2015 2014 Machinery and equipment $ 161,292 $ 152,421 Buildings and structural components 173,580 169,609 Land 11,740 9,488 Construction-in-progress: Stillwater Mine 2,615 2,633 East Boulder Mine 435 1,539 Marathon 148 148 Processing facilities and other 1,982 1,994 $ 351,792 $ 337,832 Accumulated depreciation (241,835 ) (218,951 ) Total property, plant, and equipment, net $ 109,957 $ 118,881 The Company’s capital outlay for the years ended December 31, was as follows: (In thousands) 2015 2014 2013 Stillwater Mine $ 88,799 $ 95,038 $ 90,827 East Boulder Mine 17,916 28,813 25,928 Marathon project — — 14,081 Altar project 46 45 101 Other 5,089 5,917 7,599 Total capital outlay $ 111,850 $ 129,813 $ 138,536 Non-cash capitalized interest / depreciation (9,347 ) (8,443 ) (8,910 ) Change in accounts payable for capital expenditures 4,931 (1,688 ) (597 ) Total cash paid $ 107,434 $ 119,682 $ 129,029 Prior year numbers have been restated to confirm to current year presentation.

Asset Retirement Obligation

Asset Retirement Obligation	12 Months Ended
	Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligation	ASSET RETIREMENT OBLIGATION The following summary sets forth the annual changes to the Company’s asset retirement obligation in 2015, 2014 and 2013 : (In thousands) Stillwater Mine East Boulder Mine Total Balance at December 31, 2012 $ 7,381 $ 584 $ 7,965 Accretion expense 639 50 689 Balance at December 31, 2013 $ 8,020 $ 634 $ 8,654 Accretion expense 700 47 747 Balance at December 31, 2014 $ 8,720 $ 681 $ 9,401 Accretion expense 777 35 812 Additions and changes in estimates $ 1,115 $ (301 ) 814 Balance at December 31, 2015 $ 10,612 $ 415 $ 11,027 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. No adjustments were made to the asset retirement obligations in 2014 or 2013. The Company estimates the mine life of the Stillwater Mine and the East Boulder Mine to the year 2033 and 2081 , respectively. At December 31, 2015 , the Company had posted surety bonds with the State of Montana and the United States Forest Service in the amount of $40.1 million to satisfy the current financial guarantee requirements determined by the regulatory agencies. The final updated environmental impact statement (EIS) was completed during the second quarter of 2012 and the East Boulder financial guarantee was reviewed and revised in 2014. The Company is expecting the review process for the Stillwater Mine financial guarantee to extend through the first quarter of 2016 and anticipates these financial guarantee requirements may increase.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 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 that are supported by little or no market activity and are significant to the fair value of the assets or liabilities. Financial assets and liabilities measured at fair value on a recurring basis at December 31, 2015 , and 2014 consisted of the following: (In thousands) Fair Value Measurements At December 31, 2015 Total Level 1 Level 2 Level 3 Money market fund $ 54,761 $ 54,761 $ — $ — Mutual funds $ 743 $ 743 $ — $ — Investments Federal agency notes $ 284,757 $ — $ 284,757 $ — Commercial paper $ 31,672 $ — $ 31,672 $ — (In thousands) Fair Value Measurements At December 31, 2014 Total Level 1 Level 2 Level 3 Money market fund $ 120,000 $ 120,000 $ — $ — 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 which are readily available and are recorded in Other noncurrent assets on the Company's Consolidated Balance Sheets . The money market fund is recorded in Cash and cash equivalents on the Company's Consolidated Balance Sheets . The fair values of the investments are 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 (loss) income on the Company's Consolidated Balance Sheets . Assets and liabilities measured at fair value on a nonrecurring basis at December 31, 2015 , and 2014 consisted of the following: (In thousands) Fair Value Measurements At December 31, 2015 Total Level 1 Level 2 Level 3 1.875 % Convertible Debentures $ 524 $ — $ 524 $ — 1.75% Convertible Debentures $ 285,446 $ — $ 285,446 $ — Long-term investments $ 524 524 $ — $ — (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 the fair value of the liability component of its outstanding 1.75% Convertible Debentures at December 31, 2015 and 2014, by using observable market based information for debt instruments of similar amounts and duration. The Company used the book value of its outstanding 1.875% Convertible Debentures to represent the fair value at December 31, 2015 and 2014 . The fair value of the Company's long-term investments in certain Canadian junior exploration companies at December 31, 2015 , and 2014 is based on quoted market prices which are readily available. 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. See "Note 4 - Asset Impairment" for further information.

Related Parties

Related Parties	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Parties	RELATED PARTIES Mitsubishi Corporation maintained a 25% ownership interest in the Company's previously wholly-owned subsidiary, Stillwater Canada Inc (SCI) until the Company purchased Mitsubishi's 25% interest in the fourth quarter of 2015. The Company made PGM sales to Mitsubishi Corporation of $38.7 million , during the first nine months of 2015 and $141.7 million and $296.6 million in the full years of 2014 and 2013, respectively. See "Note 5 - Noncontrolling Interest" for further information.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES The Company manages risk through insurance coverage, credit monitoring and diversification of suppliers and customers. The Company also seeks to maintain adequate liquidity to offset the risk of pricing cycles. REFINING AGREEMENT AND SUPPLY AGREEMENT Under the terms of the Company’s agreements with JM, the Company utilizes JM for all of its precious metals refining services. In addition, with the exception of platinum sales commitments to Tiffany & Co., all of the Company’s current mined palladium and platinum is committed for sale to JM. This significant concentration of business with JM could leave the Company without precious metal refining services should JM experience significant financial or operating difficulties during the contract period. Under such circumstances, it is not clear that sufficient alternate processing capacity would be available to cover the Company’s requirements, nor that the terms of any such alternate processing arrangements as might be available would be financially acceptable to the Company. Any such disruption in refining services could have a negative effect on the Company’s ability to generate revenues, profits, and cash flows. OPERATING LEASES The Company has operating leases for various mining equipment, office equipment and office space expiring at various dates through November 30, 2019 . Total rental expense for cancelable and non-cancelable operating leases was $1.8 million , $2.0 million and $2.3 million in 2015, 2014 and 2013 , respectively. Future minimum lease payments for operating leases with terms in excess of one year are as follows: Year ended (In thousands) Minimum Lease Payment 2016 $ 150 2017 148 2018 120 2019 66 Total $ 484 SIGNIFICANT CUSTOMERS Total sales to significant customers as a percentage of total revenues for the years ended December 31, were as follows: 2015 (1) 2014 (1) 2013 (1) Customer A 75 % 51 % 14 % Customer B — 15 % 29 % Customer C — — 14 % Customer D — — 12 % 75 % 66 % 69 % (1) The “—” symbol represents less than 10% of total revenues LABOR UNION CONTRACTS The Company's represented workforce is covered under two separate collective bargaining agreements. One of these agreements, covering approximately 56% of its active labor force which are located at the Stillwater Mine and the Company's processing facilities in Columbus, expired on June 12, 2015. Following the expiration of this agreement, employees located at these sites voted twice, and twice rejected, a tentative labor agreement reached on May 27, 2015 that was recommended by the United Steel Workers (USW) International Union Local 11-0001. Following the votes, employees continued to work under the terms of the previously expired contract. On July 30, 2015, the Company notified the union that negotiations had reached an impasse and that it would implement its last, best and final contract offer, which was the same agreement previously rejected by the represented employees. The Company implemented the new agreement on September 1, 2015, which included: • no increase in base wages for each of the first two years of the agreement; and • simplification of the incentive program and the introduction of metrics in the incentive program that align employee activities and shareholder outcomes. On January 29, 2016, employees located at the Stillwater Mine and Columbus processing facilities voted again and ratified a four year contract. The new agreement essentially mirrors the Company's last, best and final contract offer, which the workers have been working under since September 1, 2015. The contract agreement was retrospectively effective to June 2, 2015. The second collective bargaining agreement, covering approximately 22% of its active labor force, which are located at the East Boulder Mine, was scheduled to expire on December 31, 2015. On December 15, 2015, the union membership at the East Boulder Mine ratified a four year contract. The new agreement essentially rolls forward the previous contract, including a provision for no increase in base wages for each of the first two years of the agreement and other minor modifications. Effective date for this contract is January 1, 2016. The Company's total workforce at December 31, 2015 , was comprised of 1,439 employees, including 1,430 located in Montana and Colorado and 9 located in Canada and South America. This compares to 1,619 employees at December 31, 2014 , of which 1,609 were Montana-based and 10 were located in Canada and South America. LEGAL PROCEEDINGS The Company is involved in various claims and legal actions arising in the ordinary course of business, primarily employee lawsuits. In the opinion of management, the ultimate disposition of these matters is not expected to have a material adverse effect on the Company’s consolidated financial position, results of operations or liquidity.

Quarterly Data (Unaudited)

Quarterly Data (Unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Data (Unaudited)	QUARTERLY DATA (UNAUDITED) Quarterly earnings data for the years ended December 31, 2015 , and 2014 were as follows: (In thousands, except per share data) 2015 Quarter Ended March 31 June 30 September 30 December 31 Revenue $ 200,520 $ 185,384 $ 168,441 $ 171,985 Depletion, depreciation and amortization $ 17,121 $ 17,198 $ 15,362 $ 15,468 Operating income (loss) $ 21,170 $ (34,812 ) $ (6,181 ) $ 129 Net income (loss) * $ 22,888 $ (39,018 ) $ (12,029 ) $ 4,424 Comprehensive income (loss) attributable to common stockholders * $ 23,139 $ (27,429 ) $ (11,912 ) $ 4,061 Basic earnings (loss) per share attributable to common stockholders $ 0.19 $ (0.23 ) $ (0.10 ) $ 0.04 Diluted earnings (loss) per share attributable to common stockholders * $ 0.17 $ (0.23 ) $ (0.10 ) $ 0.04 * The amounts do not equal the year-to-date amounts due to the impact of rounding. (In thousands, except per share data) 2014 Quarter Ended March 31 June 30 September 30 December 31 Revenue $ 219,499 $ 249,887 $ 252,066 $ 222,167 Depletion, depreciation and amortization $ 15,151 $ 17,802 $ 17,181 $ 17,272 Operating income $ 24,977 $ 27,484 $ 26,758 $ 18,948 Net income $ 19,039 $ 17,658 $ 17,835 $ 14,351 Comprehensive income attributable to common stockholders $ 19,535 $ 18,073 $ 17,965 $ 14,735 Basic earnings per share attributable to common stockholders * $ 0.16 $ 0.15 $ 0.15 $ 0.12 Diluted earnings per share attributable to common stockholders * $ 0.15 $ 0.14 $ 0.14 $ 0.12 * The amounts in the table above do not equal the year-to-date amounts due to the impact of rounding.

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	PRINCIPLES OF CONSOLIDATION The accompanying consolidated financial statements include the accounts of Stillwater Mining Company, its wholly-owned subsidiaries and entities in which it holds a controlling interest (collectively referred to as the “Company”). All inter-company transactions and balances have been eliminated upon consolidation.
Cash and Cash Equivalents	CASH AND CASH EQUIVALENTS Cash and cash equivalents consist of all cash balances and all highly liquid investments purchased with an original maturity of three months or less.
Investments and Restricted Investments	INVESTMENTS Investment securities at December 31, 2015 , and 2014 , consist of mutual funds, federal agency notes and commercial paper with stated maturities less than two years . All securities are reported at fair value. Unrealized holding gains and losses on available-for-sale securities are excluded from earnings and are reported as a separate component of other comprehensive income (loss) until realized. Realized gains and losses are based on the carrying value (cost, net of discounts or premiums) of the sold investment and recorded as a component of other income. A decline in the market value of any available-for-sale security below cost that is deemed to be other-than-temporary results in a reduction of the carrying amount of the security to fair value. The impairment is charged to earnings and a new cost basis for the security is established. The Company’s long-term investments in several junior exploration companies were originally recorded at cost due to less than 20% equity ownership interest and no significant Company control over the investees. A decline in the market value of these long-term investments that is deemed to be other-than-temporary will result in a reduction of the carrying amount of the investment to fair value. The impairment is charged to earnings and a new cost basis for the investment is established. RESTRICTED INVESTMENTS Restricted investments are amounts that have been pledged as collateral on outstanding undrawn letters of credit (associated with reclamation obligations). The Company reviews the letters of credit and the nature of the collateral annually and therefore restricted investments is classified as current. The restrictions on the balances lapse upon expiration of the letters of credit which currently have terms of one year or less.
Inventories	INVENTORIES Mined inventories are carried at the lower of current realizable value or average cost. Production costs include the cost of direct labor and materials, depletion, depreciation and amortization, and overhead costs relating to mining and processing activities. The value of recycled inventories is determined based on the acquisition cost of the recycled material and includes all inventoriable processing costs, including direct labor, direct materials, depreciation, transportation and third-party refining costs which relate to the processing activities. Materials and supplies inventories are valued at the lower of average cost or fair market value.
Receivables	RECEIVABLES Trade receivables and other receivable balances recorded in other current assets are reported at outstanding principal amounts, net of an allowance for doubtful accounts, if deemed necessary. Management evaluates the collectability of receivable account balances to determine the allowance, if any. Management considers the other party’s credit risk and financial condition, as well as current and projected economic and market conditions, in determining the amount of the allowance. Receivable balances are written off when management determines that the balance is uncollectable.
Mineral Properties and Mine Development	MINERAL PROPERTIES AND MINE DEVELOPMENT Costs of acquiring mineral properties and mineral rights are capitalized as incurred. Prior to acquiring such mineral properties or mineral rights, the Company makes a preliminary evaluation to determine that the mineral property has significant potential to develop an economic ore body. The time between initial acquisition and full evaluation of a mineral property’s potential is variable and is determined by many factors including its location relative to existing infrastructure, stage of development, geological controls and relevant metal prices. When it has been determined that proven and probable ore reserves have been established in compliance with the SEC's Industry Guide 7, and a determination has been made to proceed toward commercial development, mining development costs incurred to develop the mineral property are capitalized. Mining exploration costs are expensed as incurred. If a mineable ore body is discovered, such costs are amortized when production begins using the units-of-production method based on the estimated quantities of recoverable metal. If no mineable ore body is discovered, such costs are expensed in the period in which it is determined the mineral property has no future economic value. Costs incurred to maintain assets on a standby basis are charged to operations. Costs of abandoned projects are charged to operations upon abandonment. Capitalized mine development costs are expenditures incurred to increase existing production, develop new ore bodies or develop mineral property substantially in advance of production. Capitalized mine development costs include a vertical shaft, multiple surface adits and underground infrastructure development including footwall laterals, ramps, rail and transportation, electrical and ventilation systems, shop facilities, material handling areas, ore handling facilities, dewatering and pumping facilities. These expenditures are capitalized and amortized over the life of the mine or over a shorter mining period, depending on the period benefited by those expenditures, using the units-of-production method. The Company utilizes Industry Guide 7 compliant total proven and probable ore reserves, measured in tons, as the basis for determining the life of mine and uses the ore reserves in the immediate and relevant vicinity as the basis for determining the shorter mining period. The Company calculates amortization of capitalized mine development costs in any vicinity by applying an amortization rate to the relevant current production. The amortization rates are each based upon a ratio of unamortized capitalized mine development costs to the related ore reserves. Capital development expenditures are added to the unamortized capitalized mine development costs and amortization rates are updated as the related assets are placed into service. In calculating the amortization rate, changes in ore reserves are accounted for as a prospective change in estimate. Ore reserves and the further benefit of capitalized mine development costs are determined based on management assumptions. Any significant changes in these assumptions, such as a change in the mine plan or a change in estimated proven and probable ore reserves could have a material effect on the expected period of benefit resulting in a potentially significant change in the amortization rate and / or the valuations of related assets. The Company’s proven ore reserves are generally expected to be extracted utilizing its existing mine development infrastructure. Additional capital expenditures will be required to access the Company’s estimated probable ore reserves. These anticipated capital expenditures are not included in the current calculation of depletion, depreciation and amortization. Expenditures incurred to sustain existing production and directly access specific ore reserve blocks or stopes provide benefit to ore reserve production over limited periods of time (secondary development) and are charged to operations as incurred. These costs include ramp and stope access excavations from the primary haulage levels (footwall laterals), stope material re-handling / laydown excavations, stope ore and waste pass excavations and chute installations, stope ventilation raise excavations and stope utility and pipe raise excavations.
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT Plant facilities and equipment are recorded at cost and depreciated using the straight-line method over estimated useful lives ranging from one to fifteen years. Interest is capitalized on expenditures related to major construction or development projects and is amortized using the same method as the related asset. Interest capitalization is discontinued when the asset is placed into operation or when development and construction cease. Maintenance and repairs are charged to cost of revenues as incurred.
Leases	LEASES The Company classifies a lease as either capital or operating. All capital leases are depreciated over the shorter of the useful life of the asset or the lease term.
Asset Impairment	ASSET IMPAIRMENT The Company reviews and evaluates its long-lived assets, including mineral properties and mine development, for impairment when events or changes in circumstances indicate that the related carrying amounts for such an asset may not be recoverable. For purposes of determining impairment, assets are grouped at the lowest level for which identifiable cash flows are largely independent of the cash flows of other groups of assets and liabilities. Impairment is considered to exist if the carrying amount of any long-lived asset or asset group is not recoverable and exceeds its fair value; the carrying value of a long-lived asset is considered not recoverable if it exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset or asset group. If impairment exists, the associated impairment loss to be recognized is the amount by which the carrying amount of the long-lived asset or asset group exceeds the fair value. In the Company’s case, the estimation of future cash flows takes into account estimates of recoverable ounces, prices for PGMs and other relevant metals (using twelve-quarter historical trailing prices and third-party projections of future prices, rather than prices at a single point in time, as indicators of longer-term future prices), any structural shifts in supply and demand or in competitive position, anticipated production levels, and future capital and reclamation expenditures, all based on life-of-mine plans and projections and measured as of the reporting date. The Company assesses, at least quarterly, whether there has been any event or change in circumstances that might indicate that the carrying value of capitalized mining costs and related property, plant and equipment, if any, may not be recoverable out of expected undiscounted future cash flows plus any estimated salvage value. In estimating the fair value of an asset or asset group, the Company takes into account various measurement alternatives, often engaging third-party advisors to assist in the process. Such alternatives will vary depending on the circumstances but could include information from recent sales of comparable assets, third-party professional appraisals, bona fide purchase offers, and valuations derived from discounted future cash flow models. Assumptions underlying future cash flows are subject to risks and uncertainties. Any differences between significant assumptions and market conditions such as PGM prices, lower than expected recoverable ounces, and / or the Company’s operating performance could have a material effect on the Company’s determination of ore reserves, or its ability to recover the carrying amounts of its long-lived assets resulting in potential additional impairment charges.
Fair Value of Financial Instruments	FAIR VALUE OF FINANCIAL INSTRUMENTS The Company’s non-derivative financial instruments consist primarily of cash equivalents, trade receivables, payables, investments, convertible debentures and capital lease obligations. The carrying amounts of cash equivalents, trade receivables and payables approximate fair value due to their short maturities. The carrying amounts of investments approximate fair value based on market quotes. 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 fair value hierarchy was established which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The fair value hierarchy distinguishes among three levels of inputs that may be utilized when measuring fair value: Level 1 inputs (using quoted prices in active markets for identical assets or liabilities), Level 2 inputs (using external inputs other than Level 1 prices such as quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability) and Level 3 inputs (unobservable inputs supported by little or no market activity and based on internal assumptions used to measure assets and liabilities). The classification of each financial asset or liability within the above hierarchy is determined based on the lowest level input that is significant to the fair value measurement.
Revenue Recognition	REVENUE RECOGNITION Revenue is comprised of Mine Production revenue, PGM Recycling revenue and other sales revenue. Mine Production revenue consists of the sales of palladium and platinum extracted by the Company’s mining operations, including any realized hedging gains or losses. Mine Production revenue also consists of the sales of by-products (rhodium, gold, silver, copper and nickel) extracted by mining operations. PGM Recycling revenue consists of the sales of recycled palladium, platinum and rhodium derived from spent catalytic materials, including any unrealized and realized hedging gains or losses. PGM recycling revenue also includes revenue from toll processing. Other sales revenue consists of sales of PGMs that are acquired periodically in the open market and simultaneously resold to third parties. Revenue is recognized when persuasive evidence of an arrangement exists, delivery has occurred either physically or through an irrevocable transfer of metals to customers’ accounts, the price is fixed or determinable, no related obligations remain and collectability is probable. Under the terms of sales contracts and purchase orders received from customers, the Company recognizes revenue when the product is in a refined and saleable form and title passes, which is typically when the product is transferred from the account of the Company to the account of the customer. Under certain of its sales agreements, the Company instructs a third-party refiner to transfer metal from the Company’s account to the customer’s account; at this point, the Company’s account at the third-party refinery is reduced and the purchaser’s account is increased by the number of ounces of metal sold. These transfers are irrevocable and the Company has no further responsibility for the delivery of the metals. Under other sales agreements, physical conveyance occurs by the Company arranging for shipment of metal from the third-party refinery to the purchaser. In these cases, revenue is recognized at the point when title passes contractually to the purchaser. Sales discounts are recognized when the related revenue is recorded. The Company classifies any sales discounts as a reduction in revenue. The Company recognizes revenue from its toll processing services at the time the contained metals are returned to the supplier at the third-party refinery.
Noncontrolling Interest	NONCONTROLLING INTEREST Noncontrolling interest relates to the sale of a 25% ownership interest in Stillwater Canada Inc during 2012. Noncontrolling interest is classified in the Company's Consolidated Statements of Comprehensive (Loss) Income as part of consolidated net (loss) income and the accumulated amount of noncontrolling interest in the Company's Consolidated Balance Sheets as a component of equity
Reclamation and Environmental Costs	RECLAMATION AND ENVIRONMENTAL COSTS The fair value of a liability for an asset retirement obligation is recognized in the period in which it is incurred if a reasonable estimate of fair value can be made. The fair value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is depreciated over the life of the asset. The liability is accreted at the end of each period through charges to operating expense. If the obligation is settled for other than the carrying amount of the liability, the Company will recognize a gain or loss on settlement. Accounting for reclamation obligations requires management to make estimates for each mining operation of the future costs the Company will incur to complete final reclamation work required to comply with existing laws and regulations. Actual costs incurred in future periods could differ from amounts estimated. Additionally, future changes to environmental laws and regulations could increase the extent of reclamation and remediation work that the Company is required to perform. Any such increases in future costs could materially impact the amounts charged in future periods to operations for reclamation and remediation.
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 for the expected future tax consequences of temporary differences between the carrying amounts and the tax bases of those assets and liabilities, as well as operating loss and tax credit carryforwards, using enacted tax rates in effect in the years in which the differences are expected to reverse. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Deferred tax assets and liabilities are recorded on a jurisdictional basis. In assessing the realizability of U.S. and foreign deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. Each quarter, management considers the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies in making this assessment. A valuation allowance has been provided at December 31, 2015 , and 2014 , for the portion of the Company’s net deferred tax assets for which it is more likely than not that they will not be realized.
Stock-based Compensation	STOCK-BASED COMPENSATION The Company estimates the fair value of performance-based restricted stock awards using a Monte Carlo simulation valuation model. The fair value of time-based restricted stock awards is determined by the market value of the underlying shares on the date of grant. Costs resulting from all share-based payment transactions are recognized in the financial statements over the respective vesting periods. All liability classified performance-based restricted stock awards are revalued each period with a charge to earnings.
Earnings (Loss) Per Common Share	EARNINGS (LOSS) PER COMMON SHARE Basic earnings (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted earnings (loss) 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 and the Company’s convertible debentures were converted. Reported net income (loss) attributable to common stockholders is adjusted for the interest expense net of capitalized interest (including amortization expense of deferred debt and equity fees), the related income tax effect and the income (loss) attributable to the noncontrolling interest in the computation of basic and diluted earnings per share attributable to common stockholders. The Company currently has only one class of equity shares outstanding.
Comprehensive (Loss) Income	COMPREHENSIVE (LOSS) INCOME Comprehensive (loss) income includes net (loss) income, as well as other changes in stockholders’ equity that result from transactions and events other than those with stockholders. Other comprehensive (loss) income in 2015, 2014 and 2013 consisted of unrealized gains and losses related to available-for-sale marketable securities and deferred compensation.
Debt Issuance Costs	DEBT ISSUANCE COSTS Debt issuance costs are capitalized and amortized to interest expense using the effective interest method over the lives of the related debt agreements.
Foreign Currency Transactions	FOREIGN CURRENCY TRANSACTIONS The functional currency of the Company’s Canadian and South American subsidiaries is the U.S. dollar. Gains or losses resulting from transactions denominated in Canadian and South American currencies are included in Foreign currency transaction gain, net in the Company's Consolidated Statements of Comprehensive (Loss) Income .
Use of Estimates	USE OF ESTIMATES The preparation of the Company’s consolidated financial statements in conformity with United States generally accepted accounting principles 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 depletion, depreciation, amortization and accretion calculations, future cash flows from long-lived assets, fair value of long-lived assets, and fair value of derivatives. Actual results could differ from these estimates
Recent Accounting Standards	RECENT ACCOUNTING STANDARDS On May 28, 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers , which requires an entity to recognize the amount of revenue it expects to be entitled to for the transfer of promised goods or services to customers. The effective date of the new standard has been deferred by one year to January 1, 2018, and will replace most existing revenue recognition guidance in U.S. GAAP. The standard permits the use of either the retrospective or cumulative effect transition method. The Company is evaluating the effect that ASU 2014-09 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early application is not permitted. On April 7, 2015, as part of their initiative to simplify and reduce complexity in the financial statements, the FASB issued ASU 2015-03, Interest - Imputation, (Subtopic 835-30): Simplifying the Presentation of Debt Issuance. This ASU requires the debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of the debt liability. Also, requiring retrospective application for all prior periods presented in the financial statements and a disclosure of the nature of and reason for the change in accounting principle, the transition method, a description of the prior-period information that has been retrospectively adjusted and the effect of the change on the financial statement line items. ASU 2015-03 is effective for financial statements issued for fiscal years beginning after December 31, 2015, and interim periods within those fiscal years. The Company is evaluating the effect that ASU 2015-03 will have on its consolidated financial statements and disclosures and has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting. Early adoption is permitted for financial statements that have not been previously issued. On November 20, 2015, FASB issued Accounting Standards Update 2015-17, Balance Sheet Classification of Deferred Taxes (ASU 2015-17). The ASU is part of the FASB’s simplification initiative aimed at reducing complexity in accounting standards. The new guidance requires that all deferred tax assets and liabilities, along with any related valuation allowance, be classified as noncurrent on the balance sheet. The guidance is effective for annual periods beginning after December 15, 2016, including interim periods within those years. Early application is permitted. The Company adopted ASU 2015-17 prospectively at December 31, 2015 and prior periods were not retrospectively adjusted. The adoption of ASU 2015-17 has no financial impact to the Company other than to decrease current deferred tax assets resulting in a reduction of working capital.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Commodity Derivatives	The following is a summary of the Company’s outstanding commodity derivatives in its PGM Recycling Segment at December 31, 2015 : PGM Recycling: Fixed Forward Contracts Platinum Palladium Rhodium Settlement Period Ounces Average Price/Ounce Ounces Average Price/Ounce Ounces Average Price/Ounce First Quarter 2016 17,780 $ 921 28,124 $ 596 4,727 $ 727 Second Quarter 2016 2,321 $ 863 2,738 $ 554 658 $ 671

Share Compensation Plans (Table

Share Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Nonvested Share Activity	Nonvested time-based share activity during 2015 , 2014 and 2013 , is detailed in the following table: Year ended December 31, Nonvested Shares Weighted- Average Grant- Date Fair Value Nonvested time-based shares at December 31, 2012 1,278,590 $ 14.38 Granted 544,122 13.64 Vested (1) (1,791,040 ) 14.19 Forfeited (615 ) 13.99 Nonvested time-based shares at December 31, 2013 31,057 $ 11.55 Granted 348,056 14.68 Vested (158,412 ) 13.84 Forfeited (35,954 ) 14.22 Nonvested time-based shares at December 31, 2014 184,747 $ 13.80 Granted 127,407 14.17 Vested (114,129 ) 13.91 Forfeited (11,370 ) 14.21 Nonvested time-based shares at December 31, 2015 186,655 $ 13.97 (1) Pursuant to the terms of the Company's Equity Plans, the change in control that occurred in the second quarter of 2013 resulted in all outstanding nonvested shares granted under those Equity Plans immediately becoming fully vested. Nonvested performance-based share activity during 2015 and 2014 is detailed in the following table: Nonvested Shares Weighted- Average Grant- Date Fair Value Nonvested performance-based shares at January 1, 2014 — $ — Granted * 223,412 15.69 Vested — — Forfeited (9,176 ) 15.69 Nonvested performance-based shares at December 31, 2014 214,236 $ 15.69 Granted * 170,078 14.92 Vested — — Forfeited (5,037 ) 15.34 Nonvested performance-based shares at December 31, 2015 379,277 $ 15.34 * The number of performance-based shares granted is based on the target award amounts in the performance share grant agreements.
Compensation Expense of Nonvested Shares Outstanding to be Recognized	The following table presents the compensation expense of the nonvested shares outstanding at December 31, 2015 , to be recognized over the remaining vesting periods: (In thousands) Time-based shares Performance -based shares 2016 $ 1,522 1,491 2017 631 808 2018 12 — Total $ 2,165 $ 2,299
Stock Option Activity	Stock option activity for the years ended December 31, 2015 , 2014 and 2013 , is summarized as follows: Year Ended December 31, Shares Weighted Average Exercise Price Options outstanding at December 31, 2012 242,519 $ 10.57 Options exercisable at December 31, 2012 224,933 10.08 2013 Activity Options exercised (25,471 ) 5.02 Options canceled / forfeited (17,757 ) 6.07 Options outstanding and exercisable at December 31, 2013 199,291 $ 11.68 2014 Activity Options exercised (105,047 ) 9.54 Options canceled / forfeited (13,100 ) 14.32 Options outstanding and exercisable at December 31, 2014 81,144 $ 14.03 2015 Activity Options exercised (6,492 ) 9.16 Options canceled / forfeited (17,542 ) 11.01 Options outstanding and exercisable at December 31, 2015 57,110 $ 15.51 The following table summarizes additional stock option activity: (In thousands) 2015 2014 2013 Intrinsic value of exercisable options $ 9 $ 207 $ 469 Cash received from options exercised $ 60 $ 993 $ 128 Intrinsic value of options exercised $ 25 $ 674 $ 205 Compensation expense (recorded in General and administrative) $ — $ — $ 41
Information for Outstanding and Exercisable Options	The following table summarizes information for outstanding and exercisable options at December 31, 2015 : Options Outstanding and Exercisable Range of Exercise Price Number Outstanding and Exercisable Weighted Average Remaining Contract Life Weighted Average Exercise Price $ 4.17 - $11.50 9,209 2.8 $ 8.69 $11.51 - $12.82 9,117 2.7 $ 12.15 $12.83 - $15.45 9,117 2.5 $ 13.78 $15.46 - $18.56 8,642 4.2 $ 16.80 $18.57 - $19.55 10,600 4.9 $ 19.05 $19.56 - $24.55 10,425 4.3 $ 21.34 57,110 3.6 $ 15.51
DSU Plan Activity	The following table summarizes the activity for the DSU Plan for the years ended December 31, 2015 and 2014: DSUs Fair market value of DSUs (1) Closing Share Price Granted 30,420 $ 18.69 Distributions (5,070 ) $ (66,667 ) Liability at December 31, 2014 25,350 $ 373,637 $ 14.74 Granted 37,053 $ 13.22 Liability at December 31, 2015 62,403 $ 534,804 $ 8.57 (1) Fair market value of DSUs includes effect of fractional shares.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Deferred Tax Assets and Liabilities	The components of the Company’s deferred income tax liabilities (assets) are comprised of the following temporary differences and carryforwards at December 31, 2015 , and 2014 . (In thousands) 2015 2014 Mine development and mineral interests-US $ 86,905 $ 98,204 Mineral interests-South America 13,697 20,844 Long-term debt 27,835 42,986 Total deferred tax liabilities $ 128,437 $ 162,034 Noncurrent liabilities (9,896 ) (10,703 ) Mine development and mineral interests-Canada (15,900 ) (1,214 ) Property and equipment (16,440 ) (15,683 ) Current liabilities (18,844 ) (21,301 ) Long-term investments (2,989 ) (3,158 ) Inventory (993 ) (933 ) AMT credit and other carryforwards (34,383 ) (30,956 ) Exploration (3,578 ) (4,610 ) Net operating loss (NOL) and other carryforwards (39,244 ) (48,444 ) Total deferred tax assets $ (142,267 ) $ (137,002 ) Valuation allowance 36,591 22,812 Net deferred tax assets (105,676 ) (114,190 ) Net deferred tax liabilities $ 22,761 $ 47,844
Reconciliation of the Federal Income Tax Provision	Reconciliation of the income tax (benefit) provision at the applicable statutory income tax rates to the effective rate is as follows: December 31, (In thousands) 2015 2014 2013 (Loss) income before income taxes $ (36,069 ) $ 85,141 $ (395,726 ) Income tax (benefit) provision at statutory rates (12,624 ) 29,799 (138,504 ) State income tax expense, net of federal benefit 50 3,553 3,995 Percentage depletion (5,366 ) (17,302 ) (8,786 ) Foreign currency transaction loss (gain), net 3,471 (1,353 ) 31,605 Compensation related adjustment 59 6 359 Change in valuation allowance 13,780 2,127 5,595 Return-to-provision (1,259 ) 92 1,097 Impact of foreign operations (2,981 ) (52 ) 8,895 Rate adjustment (7,290 ) (96 ) 1,503 Other (173 ) (516 ) 588 Net income tax (benefit) provision $ (12,333 ) $ 16,258 $ (93,653 )
Schedule of Components of Income Tax (Benefit) Provision	The income tax (benefit) provision is comprised of the following: December 31, (In thousands) 2015 2014 2013 Current Federal $ 3,203 $ 13,902 $ 9,740 State 2,175 6,947 5,152 Current income tax $ 5,378 $ 20,849 $ 14,892 Deferred Federal (1,474 ) (1,577 ) 5,278 State (14,510 ) (2,462 ) 252 Foreign (1,727 ) (552 ) (114,075 ) Deferred income tax benefit (17,711 ) (4,591 ) (108,545 ) Income tax (benefit) provision $ (12,333 ) $ 16,258 $ (93,653 )
Schedule of Earnings (Losses) Before Income Taxes	The components of (loss) income before income tax (benefit) provision by tax jurisdiction for the years ended December 31, 2015, 2014 and 2013 were as follows: (In thousands) 2015 2014 2013 United States $ 10,574 $ 88,281 $ 61,671 Foreign (46,643 ) (3,140 ) (457,397 ) Loss / income before income tax (benefit) provision $ (36,069 ) $ 85,141 $ (395,726 )

Comprehensive (Loss) Income (Ta

Comprehensive (Loss) Income (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Changes in Accumulated Other Comprehensive (Loss) Income	The following summary sets forth the changes in Accumulated other comprehensive (loss) income during 2015, 2014 and 2013 : (In thousands) Available-for-sale marketable securities Deferred Compensation Accumulated Other Comprehensive (Loss) Income Balance at December 31, 2012 $ (99 ) $ — $ (99 ) Change in value, net of tax 105 — 105 Balance at December 31, 2013 6 — 6 Change in value, net of tax 11 — 11 Balance at December 31, 2014 17 — 17 Change in value, net of tax (384 ) 170 (214 ) Balance at December 31, 2015 $ (367 ) $ 170 $ (197 )

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 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) Mine Production PGM Recycling Canadian Properties South American Properties All Other Total Year ended December 31, 2015 Revenues $ 415,774 $ 310,156 $ — $ — $ 400 $ 726,330 Depletion, depreciation and amortization $ 64,200 $ 949 $ — $ — $ — $ 65,149 General and administrative expenses $ — $ — $ 1,146 $ 504 $ 32,383 $ 34,033 Interest income $ — $ 1,653 $ 7 $ 27 $ 1,268 $ 2,955 Interest expense $ — $ — $ — $ — $ 20,187 $ 20,187 Income (loss) before impairment charge and income taxes $ 57,618 $ 10,151 $ (1,910 ) $ 2,218 $ (57,374 ) $ 10,703 Impairment charge $ — $ — $ 46,772 $ — $ — $ 46,772 Income (loss) after impairment charge, before income taxes $ 57,618 $ 10,151 $ (48,682 ) $ 2,218 $ (57,374 ) $ (36,069 ) Capital expenditures $ 100,725 $ 327 $ 46 $ — $ 6,336 $ 107,434 Total assets $ 613,498 $ 40,757 $ 26,517 $ 103,774 $ 497,664 $ 1,282,210 (In thousands) Mine Production PGM Recycling Canadian Properties South American Properties All Other Total Year ended December 31, 2014 Revenues $ 536,010 $ 401,684 $ — $ — $ 5,925 $ 943,619 Depletion, depreciation and amortization $ 66,387 $ 1,019 $ — $ — $ — $ 67,406 General and administrative expenses $ — $ — $ 3,251 $ 337 $ 31,479 $ 35,067 Interest income $ — $ 2,535 $ 6 $ 68 $ 942 $ 3,551 Interest expense $ — $ — $ 1 $ — $ 22,718 $ 22,719 Income (loss) before impairment charge and income taxes $ 136,990 $ 11,719 $ (4,581 ) $ 2,600 $ (61,037 ) $ 85,691 Impairment charge $ — $ — $ 550 $ — $ — $ 550 Income (loss) after impairment charge, before income taxes $ 136,990 $ 11,719 $ (5,131 ) $ 2,600 $ (61,037 ) $ 85,141 Capital expenditures $ 115,147 $ 181 $ — $ 45 $ 4,309 $ 119,682 Total assets $ 596,653 $ 65,513 $ 75,250 $ 106,947 $ 554,964 $ 1,399,327 (In thousands) Mine Production PGM Recycling Canadian Properties South American Properties All Other Total Year ended December 31, 2013 Revenues $ 478,918 $ 560,588 $ — $ — $ — $ 1,039,506 Depletion, depreciation and amortization $ 58,201 $ 1,116 $ — $ — $ — $ 59,317 General and administrative expenses $ — $ — $ 1,112 $ 2,549 $ 42,916 $ 46,577 Interest income $ — $ 3,375 $ 20 $ 184 $ 902 $ 4,481 Interest expense $ — $ — $ — $ — $ 22,957 $ 22,957 Income (loss) before impairment charge and income taxes $ 106,122 $ 35,463 $ (4,255 ) $ 8,845 $ (80,146 ) $ 66,029 Impairment charge $ — $ — $ 171,338 $ 290,417 $ — $ 461,755 Income (loss) after impairment charge, before income taxes $ 106,122 $ 35,463 $ (175,593 ) $ (281,572 ) $ (80,146 ) $ (395,726 ) Capital expenditures $ 108,527 $ 330 $ 12,380 $ 101 $ 7,691 $ 129,029 Total assets $ 553,153 $ 80,555 $ 83,800 $ 109,960 $ 519,212 $ 1,346,680

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities by Major Security Type and Class	The amortized cost, gross unrealized gains, gross unrealized losses, and fair market value of available-for-sale investment securities by major security type and class of security at December 31, are as follows: (In thousands) Amortized Cost Gross unrealized gains Gross unrealized losses Fair market value 2015 Federal agency notes $ 285,276 $ — $ (519 ) $ 284,757 Commercial paper 31,730 — (58 ) 31,672 Subtotal 317,006 — (577 ) 316,429 Mutual funds 482 261 — 743 Total $ 317,488 $ 261 $ (577 ) $ 317,172 2014 Federal agency notes $ 143,132 $ 40 $ (33 ) $ 143,139 Commercial paper 108,371 1 (257 ) 108,115 Subtotal 251,503 41 (290 ) 251,254 Mutual funds 344 279 — 623 Total $ 251,847 $ 320 $ (290 ) $ 251,877
Maturities of Available-for-sale Securities	The maturities of available-for-sale securities at December 31, 2015 , are as follows: (In thousands) Amortized cost Fair market value Federal agency notes Due in one year or less $ 219,748 $ 219,581 Due after one year through two years 65,528 65,176 Total $ 285,276 $ 284,757 Commercial paper Due in one year or less $ 20,490 $ 20,472 Due after one year through two years 11,240 11,200 Total $ 31,730 $ 31,672

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2015
Inventory Disclosure [Abstract]
Components Of Inventories	Inventories reflected in the accompanying balance sheets at December 31, consisted of the following: (In thousands) 2015 2014 Metals inventory Raw ore $ 4,234 $ 4,984 Concentrate and in-process 43,727 48,712 Finished goods 32,618 49,885 $ 80,579 $ 103,581 Materials and supplies 21,493 26,726 Total inventory $ 102,072 $ 130,307

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Reconciliation of Basic and Diluted Earnings Per Share	The reconciliation showing the computation of basic and diluted shares and the related impact on income for the year ended December 31, 2014 is shown in the following table: Year Ended December 31, 2014 (In thousands, except per share amounts) Income (Numerator) Weighted Average Shares (Denominator) Per Share Amount Basic EPS Net income attributable to common stockholders $ 70,297 119,953 $ 0.59 Effect of Dilutive Securities Stock options — 31 Nonvested shares — 53 Contingently issuable shares — 98 1.875% Convertible Debentures, net of tax — 95 1.75% Convertible Debentures, net of tax and capitalized interest 16,613 36,003 Diluted EPS Net income attributable to common stockholders and assumed conversions $ 86,910 156,233 $ 0.56

Debt and Capital Lease Obliga37

Debt and Capital Lease Obligations (Tables)	12 Months Ended
	Dec. 31, 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 for interest on the Company's outstanding debt for the years ended December 31, 2015 , 2014 and 2013: (In thousands) 2015 2014 2013 1.75% Convertible Debentures Amortization of debt issuance costs $ 925 $ 1,120 $ 1,139 Interest expense, net of capitalized interest $ 18,752 $ 19,416 $ 18,261 Reduction in debt issuance costs (repurchase of debt) $ 747 $ — $ — Cash payments for interest $ 6,827 $ 6,943 $ 6,905 1.875% Convertible Debentures Amortization of debt issuance costs $ — $ — $ 195 Interest expense, net of capitalized interest $ — $ 42 $ 684 Cash payments for interest $ 42 $ 42 $ 1,582 Asset-Backed Revolving Credit Facility Amortization of debt issuance costs $ 539 $ 272 $ 272 Fees $ 1,168 $ 1,026 $ 1,082 Exempt Facility Revenue Bonds, Series 2000 Amortization of debt issuance costs $ — $ 873 $ 58 Interest expense $ — $ 1,240 $ 2,400 Cash payments for interest $ — $ 1,240 $ 2,400
Schedule of Debt	The Company's total current and long-term debt balances at December 31, 2015 and 2014 were as follows: December 31, 2015 December 31, 2014 (In thousands) Current Long-Term Current Long-Term 1.75% Convertible Debentures Aggregate principal $ — $ 335,150 $ — $ 396,750 Debt discount — (76,754 ) — (105,634 ) Debt balance — 258,396 — 291,116 1.875% Convertible Debentures — 524 — 2,245 Capital Lease Obligation 580 — 2,067 580 Small Land Purchase 77 — 77 82 Total debt balances $ 657 $ 258,920 $ 2,144 $ 294,023
Schedule of Future Minimum Lease Payments for Capital Leases	The following is a schedule of the future minimum lease payments for the capital lease together with the present value of the net minimum lease payments: Year ended December 31, 2015 (In thousands) 2016 minimum lease payments $ 589 Interest at rates ranging from 5.21% to 5.46% (before-tax) (9 ) Net minimum lease payments $ 580

Mineral Properties and Mine D38

Mineral Properties and Mine Development (Tables)	12 Months Ended
	Dec. 31, 2015
Extractive Industries [Abstract]
Mineral Properties and Mine Development	Mineral properties and mine development at December 31, 2015 , and 2014 , consisted of the following: (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 697,781 616,872 East Boulder Mine 220,281 204,483 $ 1,030,542 $ 980,607 Accumulated depletion and amortization (457,311 ) (411,601 ) Total mineral properties and mine development, net $ 573,231 $ 569,006

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	Property, plant and equipment at December 31, consisted of the following: (In thousands) 2015 2014 Machinery and equipment $ 161,292 $ 152,421 Buildings and structural components 173,580 169,609 Land 11,740 9,488 Construction-in-progress: Stillwater Mine 2,615 2,633 East Boulder Mine 435 1,539 Marathon 148 148 Processing facilities and other 1,982 1,994 $ 351,792 $ 337,832 Accumulated depreciation (241,835 ) (218,951 ) Total property, plant, and equipment, net $ 109,957 $ 118,881
Schedule of Capital Expenditures	The Company’s capital outlay for the years ended December 31, was as follows: (In thousands) 2015 2014 2013 Stillwater Mine $ 88,799 $ 95,038 $ 90,827 East Boulder Mine 17,916 28,813 25,928 Marathon project — — 14,081 Altar project 46 45 101 Other 5,089 5,917 7,599 Total capital outlay $ 111,850 $ 129,813 $ 138,536 Non-cash capitalized interest / depreciation (9,347 ) (8,443 ) (8,910 ) Change in accounts payable for capital expenditures 4,931 (1,688 ) (597 ) Total cash paid $ 107,434 $ 119,682 $ 129,029

Asset Retirement Obligation (Ta

Asset Retirement Obligation (Tables)	12 Months Ended
	Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
Changes in Asset Retirement Obligation	The following summary sets forth the annual changes to the Company’s asset retirement obligation in 2015, 2014 and 2013 : (In thousands) Stillwater Mine East Boulder Mine Total Balance at December 31, 2012 $ 7,381 $ 584 $ 7,965 Accretion expense 639 50 689 Balance at December 31, 2013 $ 8,020 $ 634 $ 8,654 Accretion expense 700 47 747 Balance at December 31, 2014 $ 8,720 $ 681 $ 9,401 Accretion expense 777 35 812 Additions and changes in estimates $ 1,115 $ (301 ) 814 Balance at December 31, 2015 $ 10,612 $ 415 $ 11,027

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 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 December 31, 2015 , and 2014 consisted of the following: (In thousands) Fair Value Measurements At December 31, 2015 Total Level 1 Level 2 Level 3 Money market fund $ 54,761 $ 54,761 $ — $ — Mutual funds $ 743 $ 743 $ — $ — Investments Federal agency notes $ 284,757 $ — $ 284,757 $ — Commercial paper $ 31,672 $ — $ 31,672 $ — (In thousands) Fair Value Measurements At December 31, 2014 Total Level 1 Level 2 Level 3 Money market fund $ 120,000 $ 120,000 $ — $ — 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 December 31, 2015 , and 2014 consisted of the following: (In thousands) Fair Value Measurements At December 31, 2015 Total Level 1 Level 2 Level 3 1.875 % Convertible Debentures $ 524 $ — $ 524 $ — 1.75% Convertible Debentures $ 285,446 $ — $ 285,446 $ — Long-term investments $ 524 524 $ — $ — (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 $ — $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum lease payments for operating leases with terms in excess of one year are as follows: Year ended (In thousands) Minimum Lease Payment 2016 $ 150 2017 148 2018 120 2019 66 Total $ 484
Schedule of Total Sales to Significant Customers as a Percentage of Total Revenues	Total sales to significant customers as a percentage of total revenues for the years ended December 31, were as follows: 2015 (1) 2014 (1) 2013 (1) Customer A 75 % 51 % 14 % Customer B — 15 % 29 % Customer C — — 14 % Customer D — — 12 % 75 % 66 % 69 % (1) The “—” symbol represents less than 10% of total revenues

Quarterly Data (Unaudited) (Tab

Quarterly Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Earnings Data	Quarterly earnings data for the years ended December 31, 2015 , and 2014 were as follows: (In thousands, except per share data) 2015 Quarter Ended March 31 June 30 September 30 December 31 Revenue $ 200,520 $ 185,384 $ 168,441 $ 171,985 Depletion, depreciation and amortization $ 17,121 $ 17,198 $ 15,362 $ 15,468 Operating income (loss) $ 21,170 $ (34,812 ) $ (6,181 ) $ 129 Net income (loss) * $ 22,888 $ (39,018 ) $ (12,029 ) $ 4,424 Comprehensive income (loss) attributable to common stockholders * $ 23,139 $ (27,429 ) $ (11,912 ) $ 4,061 Basic earnings (loss) per share attributable to common stockholders $ 0.19 $ (0.23 ) $ (0.10 ) $ 0.04 Diluted earnings (loss) per share attributable to common stockholders * $ 0.17 $ (0.23 ) $ (0.10 ) $ 0.04 * The amounts do not equal the year-to-date amounts due to the impact of rounding. (In thousands, except per share data) 2014 Quarter Ended March 31 June 30 September 30 December 31 Revenue $ 219,499 $ 249,887 $ 252,066 $ 222,167 Depletion, depreciation and amortization $ 15,151 $ 17,802 $ 17,181 $ 17,272 Operating income $ 24,977 $ 27,484 $ 26,758 $ 18,948 Net income $ 19,039 $ 17,658 $ 17,835 $ 14,351 Comprehensive income attributable to common stockholders $ 19,535 $ 18,073 $ 17,965 $ 14,735 Basic earnings per share attributable to common stockholders * $ 0.16 $ 0.15 $ 0.15 $ 0.12 Diluted earnings per share attributable to common stockholders * $ 0.15 $ 0.14 $ 0.14 $ 0.12 * The amounts in the table above do not equal the year-to-date amounts due to the impact of rounding.

Summary of Significant Accoun44

Summary of Significant Accounting Policies (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Available-for-sale, stated maturities, less than		2 years	2 years
Equity method investment, ownership percentage, less than	20.00%	20.00%
Noncontrolling interest ownership percentage					25.00%
Percent of noncontrolling interest purchased	25.00%
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, useful life		1 year
Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, useful life		15 years
Stillwater Canada, Inc. [Member]
Property, Plant and Equipment [Line Items]
Noncontrolling interest ownership percentage	25.00%	25.00%	25.00%	25.00%
Percent of noncontrolling interest purchased	25.00%

Sales (Narrative) (Details)

Sales (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Sales [Line Items]
Revenues from by-product sales		$ 23,100	$ 29,600	$ 27,100
Supply and refining agreement term	5 years
Period after which refining arrangement may be terminated	4 years
Metal resold to third parties		$ 400	5,925	$ 0
Metal Acquired in Open Market and Resold to Third Parties [Member]
Sales [Line Items]
Metal resold to third parties			$ 5,300

Asset Impairment (Details)

Asset Impairment (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge						$ 46,772	$ 550	$ 461,755
Marathon Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge			$ 171,400					171,400
Carrying value of mineral properties and mine development, and property, plant and equipment			228,600					228,600
Mineral properties and mine development, and property, plant and equipment, estimated fair market value			$ 57,300					57,300
Marathon Properties [Member] | Mining Properties and Mineral Rights [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge								170,500
Marathon Properties [Member] | Construction-in-Progress [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge								$ 800
Altar Property [Member] | San Juan, Argentina [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge				$ 290,400	$ 290,400
Mineral properties and mine development, estimated fair market value				$ 102,000	$ 102,000
Marathon Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charge	$ 46,800	$ 500
Mineral properties, fair value	$ 8,600

Noncontrolling Interest (Detail

Noncontrolling Interest (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Noncontrolling Interest [Line Items]
Noncontrolling interest ownership percentage					25.00%
Cash paid for noncontrolling interest in SCI by Mitsubishi Corp					$ 81,250
Amount contributed to SCI for initial cash call by Mitsubishi Corp					$ 13,600
Maximum PGM production purchase percentage					100.00%
Net income (loss) attributable to noncontrolling interest		$ (11,808)	$ (1,414)	$ (31,867)
Impairment loss		46,772	$ 550	$ 461,755
Percent of noncontrolling interest purchased	25.00%
Purchase of noncontrolling interest	$ 5,200
Payments to acquire noncontrolling interest	$ 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 loss		$ 11,700
Stillwater Canada, Inc. [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest ownership percentage	25.00%	25.00%	25.00%	25.00%
Percent of noncontrolling interest purchased	25.00%

Derivative Instruments (Company

Derivative Instruments (Company's Outstanding Commodity Derivatives) (Details)	12 Months Ended
	Dec. 31, 2015oz$ / oz
First Quarter 2016 [Member] | Platinum [Member]
Derivative [Line Items]
Ounces | oz	17,780
Average Price/Ounce | $ / oz	921
First Quarter 2016 [Member] | Palladium [Member]
Derivative [Line Items]
Ounces | oz	28,124
Average Price/Ounce | $ / oz	596
First Quarter 2016 [Member] | Rhodium [Member]
Derivative [Line Items]
Ounces | oz	4,727
Average Price/Ounce | $ / oz	727
Second Quarter 2016 [Member] | Platinum [Member]
Derivative [Line Items]
Ounces | oz	2,321
Average Price/Ounce | $ / oz	863
Second Quarter 2016 [Member] | Palladium [Member]
Derivative [Line Items]
Ounces | oz	2,738
Average Price/Ounce | $ / oz	554
Second Quarter 2016 [Member] | Rhodium [Member]
Derivative [Line Items]
Ounces | oz	658
Average Price/Ounce | $ / oz	671

Share Compensation Plans (Chang

Share Compensation Plans (Changes In The Company's Nonvested Shares) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Nonvested Shares
Nonvested shares, Beginning Balance	25,350
Nonvested shares, Granted	37,053	30,420
Nonvested shares, Vested		(5,070)
Nonvested shares, Ending Balance	62,403	25,350
Weighted-Average Grant-Date Fair Value
Nonvested shares, Weighted-Average Grant-Date Fair Value, Beginning of Period (in usd per share)	$ 14.74
Nonvested shares, Weighted-Average Grant-Date Fair Value, Granted (in usd per share)	13.22	$ 18.69
Nonvested shares, Weighted-Average Grant-Date Fair Value, End of Period (in usd per share)	$ 8.57	$ 14.74
Time-based shares [Member]
Nonvested Shares
Nonvested shares, Beginning Balance	184,747	31,057	1,278,590
Nonvested shares, Granted	127,407	348,056	544,122
Nonvested shares, Vested	(114,129)	(158,412)	(1,791,040)
Nonvested shares, Forfeited	(11,370)	(35,954)	(615)
Nonvested shares, Ending Balance	186,655	184,747	31,057
Weighted-Average Grant-Date Fair Value
Nonvested shares, Weighted-Average Grant-Date Fair Value, Beginning of Period (in usd per share)	$ 13.80	$ 11.55	$ 14.38
Nonvested shares, Weighted-Average Grant-Date Fair Value, Granted (in usd per share)	14.17	14.68	13.64
Nonvested shares, Weighted-Average Grant-Date Fair Value, Vested (in usd per share)	13.91	13.84	14.19
Nonvested shares, Weighted-Average Grant-Date Fair Value, Forfeited (in usd per share)	14.21	14.22	13.99
Nonvested shares, Weighted-Average Grant-Date Fair Value, End of Period (in usd per share)	$ 13.97	$ 13.80	$ 11.55
Performance-based shares [Member]
Nonvested Shares
Nonvested shares, Beginning Balance	214,236	0
Nonvested shares, Granted	170,078	223,412
Nonvested shares, Vested	0	0
Nonvested shares, Forfeited	(5,037)	(9,176)
Nonvested shares, Ending Balance	379,277	214,236	0
Weighted-Average Grant-Date Fair Value
Nonvested shares, Weighted-Average Grant-Date Fair Value, Beginning of Period (in usd per share)	$ 15.69	$ 0
Nonvested shares, Weighted-Average Grant-Date Fair Value, Granted (in usd per share)	14.92	15.69
Nonvested shares, Weighted-Average Grant-Date Fair Value, Vested (in usd per share)	0	0
Nonvested shares, Weighted-Average Grant-Date Fair Value, Forfeited (in usd per share)	15.34	15.69
Nonvested shares, Weighted-Average Grant-Date Fair Value, End of Period (in usd per share)	$ 15.34	$ 15.69	$ 0

Share Compensation Plans (Compe

Share Compensation Plans (Compensation Expense to be Recognized) (Details) $ in Thousands	Dec. 31, 2015USD ($)
Time-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
2,016	$ 1,522
2,017	631
2,018	12
Total	2,165
Performance-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
2,016	1,491
2,017	808
2,018	0
Total	$ 2,299

Share Compensation Plans (Stock

Share Compensation Plans (Stock Option Activity) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Shares
Options outstanding, Shares, Beginning Balance	81,144	199,291	242,519
Options exercisable, Shares, Beginning Balance			224,933
Options exercised, Shares	(6,492)	(105,047)	(25,471)
Options canceled/forfeited, Shares	(17,542)	(13,100)	(17,757)
Options outstanding, Shares, Ending Balance	57,110	81,144	199,291
Weighted Average Exercise Price
Options outstanding, Weighted Average Exercise Price, Beginning of Period (in usd per share)	$ 14.03	$ 11.68	$ 10.57
Options exercisable, Weighted Average Exercise Price, Beginning of Period (in usd per share)			10.08
Options exercised, Weighted Average Exercise Price (in usd per share)	9.16	9.54	5.02
Options canceled/forfeited, Weighted Average Exercise Price (in usd per share)	11.01	14.32	6.07
Options outstanding, Weighted Average Exercise Price, End of Period (in usd per share)	$ 15.51	$ 14.03	$ 11.68
Intrinsic value of exercisable options	$ 9,000	$ 207,000	$ 469,000
Cash received from options exercised	60,000	993,000	128,000
Intrinsic value of options exercised	25,000	674,000	205,000
General and Administrative Expense [Member] | Stock Options [Member]
Weighted Average Exercise Price
Compensation expense (recorded in General and administrative)	$ 0	$ 0	$ 41,400

Share Compensation Plans (Outst

Share Compensation Plans (Outstanding and Exercisable Options) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Shares, Number	57,110	81,144	199,291	242,519
Options Outstanding, Average Remaining Contract Life	3 years 7 months 12 days
Options Outstanding, Weighted Average Exercise Price (in usd per share)	$ 15.51	$ 14.03	$ 11.68	$ 10.57
Range of Exercise Price 1 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower range limit (in usd per share)	4.17
Range of Exercise Price, Upper range limit (in usd per share)	$ 11.50
Options Outstanding, Shares, Number	9,209
Options Outstanding, Average Remaining Contract Life	2 years 9 months 25 days
Options Outstanding, Weighted Average Exercise Price (in usd per share)	$ 8.69
Range of Exercise Price 2 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower range limit (in usd per share)	11.51
Range of Exercise Price, Upper range limit (in usd per share)	$ 12.82
Options Outstanding, Shares, Number	9,117
Options Outstanding, Average Remaining Contract Life	2 years 8 months 2 days
Options Outstanding, Weighted Average Exercise Price (in usd per share)	$ 12.15
Range of Exercise Price 3 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower range limit (in usd per share)	12.83
Range of Exercise Price, Upper range limit (in usd per share)	$ 15.45
Options Outstanding, Shares, Number	9,117
Options Outstanding, Average Remaining Contract Life	2 years 6 months 4 days
Options Outstanding, Weighted Average Exercise Price (in usd per share)	$ 13.78
Range of Exercise Price 4 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower range limit (in usd per share)	15.46
Range of Exercise Price, Upper range limit (in usd per share)	$ 18.56
Options Outstanding, Shares, Number	8,642
Options Outstanding, Average Remaining Contract Life	4 years 2 months 26 days
Options Outstanding, Weighted Average Exercise Price (in usd per share)	$ 16.80
Range of Exercise Price 5 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower range limit (in usd per share)	18.57
Range of Exercise Price, Upper range limit (in usd per share)	$ 19.55
Options Outstanding, Shares, Number	10,600
Options Outstanding, Average Remaining Contract Life	4 years 10 months 29 days
Options Outstanding, Weighted Average Exercise Price (in usd per share)	$ 19.05
Range of Exercise Price 6 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, Lower range limit (in usd per share)	19.56
Range of Exercise Price, Upper range limit (in usd per share)	$ 24.55
Options Outstanding, Shares, Number	10,425
Options Outstanding, Average Remaining Contract Life	4 years 3 months 8 days
Options Outstanding, Weighted Average Exercise Price (in usd per share)	$ 21.34

Share Compensation Plans (Defer

Share Compensation Plans (Deferred Share Units) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Nonvested Shares
Nonvested shares, Beginning Balance	25,350
Nonvested shares, Granted	37,053	30,420
Nonvested shares, Distributions		(5,070)
Nonvested shares, Ending Balance	62,403	25,350
Distributions		$ (66,667)
Liability	$ 534,804	$ 373,637
Weighted-Average Grant-Date Fair Value
Nonvested shares, Weighted-Average Grant-Date Fair Value, Beginning of Period (in usd per share)	$ 14.74
Nonvested shares, Weighted-Average Grant-Date Fair Value, Granted (in usd per share)	13.22	$ 18.69
Nonvested shares, Weighted-Average Grant-Date Fair Value, End of Period (in usd per share)	$ 8.57	$ 14.74

Share Compensation Plans (Narra

Share Compensation Plans (Narrative) (Details) shares in Millions	12 Months Ended
	Dec. 31, 2015USD ($)planshares	Dec. 31, 2014USD ($)targetshares	Dec. 31, 2013USD ($)shares	Apr. 30, 2012shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized for issuance under the plan | shares				11.6
Compensation expense related to the accelerated vesting of unvested stock options and nonvested shares	$ 0	$ 0	$ 9,063,000
Deferred compensation arrangement, expense recognized	600,000	500,000
Employee contributions to 401(k) plan	$ 3,900,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Award expiration period	10 years
Stock Options [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 0	0	41,400
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Time-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			13,700,000
Time-based shares [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1,600,000	$ 2,600,000	4,600,000
Time-based shares [Member] | Accelerated Equity-based Compensation for Change-in-Control [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense related to the accelerated vesting of unvested stock options and nonvested shares			9,100,000
Performance-based shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Number of distinct components | target		3
Number of sub-targets | target		5
Number of sub-targets, market-based and equity classified | target		2
Number of sub-targets, market-based and liability classified | target		1
Number of sub-targets, performance-based and equity classified | target		2
Performance-based shares [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1,300,000	$ 1,500,000
2004 and 2012 Plans Combined [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available and reserved for grant | shares	4.4
2012 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized for issuance under the plan | shares				5
2004 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized for issuance under the plan | shares				5.2
General Employee Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized for issuance under the plan | shares				1.4
Non Employee Directors Deferral Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employer matching contribution percentage	20.00%
Share-based compensation expense deferred in common stock		13,500	64,200
Deferred compensation arrangement, percent of fees which may be deferred	100.00%
Nonqualified Deferred Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense deferred in common stock	$ 12,620	0	0
Share-based compensation expense deferred in cash	$ 300,000	$ 200,000	$ 200,000
Nonqualified Deferred Compensation Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation arrangement, percentage of salaries deferred	60.00%
Deferred compensation arrangement, percentage of cash compensation other than salaries deferred	100.00%
Deferred compensation arrangement, percentage of total compensation deferred	8.00%
Employee Benefit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation arrangement, percentage of cash compensation other than salaries deferred	100.00%
Deferred compensation arrangement, percentage of total compensation deferred	8.00%
Number of savings plans | plan	2
Percentage of eligible compensation employees may elect to contribute to savings plan	60.00%
Number of shares issued | shares	0.6	0.7	0.9
Shares issued in period, market value on grant date	$ 7,500,000	$ 10,300,000	$ 10,300,000

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2003
Operating Loss Carryforwards [Line Items]
Non-current net deferred tax liability	$ 22,761,000	$ 68,896,000
Current deferred tax asset		21,100,000
Net operating loss and other carryforwards	39,244,000	48,444,000
Usage of net operating losses				$ 80,900,000
Foreign net operating loss and other deductions	53,800,000
Income tax receivable	13,200,000
Uncertain tax benefits	0	0
Accrued interest and penalties on unrecognized tax benefits (less than $0.1 million in 2013)	0	0	$ 2,100,000
U.S. operations [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss and other carryforwards	24,400,000	34,600,000
Foreign operations [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss and other carryforwards	14,800,000	13,900,000
State income taxes [Member]
Operating Loss Carryforwards [Line Items]
Cash payments for income taxes	2,400,000	15,300,000	100,000
U.S. federal [Member]
Operating Loss Carryforwards [Line Items]
Cash payments for income taxes	11,000,000	$ 11,100,000	$ 5,200,000
Norilsk Nickel [Member]
Operating Loss Carryforwards [Line Items]
Usage of net operating losses				$ 10,200,000
Net Operating Loss Carryforward, Expiring 2019 to 2028 [Member] | U.S. federal [Member]
Operating Loss Carryforwards [Line Items]
Regular net operating loss carryforwards	105,200,000
Net Operating Loss, Indefinite Life [Member]
Operating Loss Carryforwards [Line Items]
Alternative minimum tax credit carryforwards	32,500,000
Foreign net operating loss and other deductions	8,300,000
Net Operating Loss Carryforward, Expiring 2029 to 2034 [Member]
Operating Loss Carryforwards [Line Items]
General business credits	1,900,000
Net Operating Loss Carryforward, Expiring 2020 to 2029 [Member]
Operating Loss Carryforwards [Line Items]
State tax net operating loss carryforwards	3,300,000
Net Operating Loss Carryforward, Expiring 2015 to 2019 [Member]
Operating Loss Carryforwards [Line Items]
Foreign net operating loss and other deductions	20,500,000
Net Operating Loss Carryforward, Expiring in 2024 to 2034 [Member]
Operating Loss Carryforwards [Line Items]
Foreign net operating loss and other deductions	$ 25,000,000

Income Taxes (Components Of Def

Income Taxes (Components Of Deferred Tax Liabilities (Assets)) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Deferred Tax Assets (Liabilities) [Line Items]
Long-term debt	$ 27,835	$ 42,986
Total deferred tax liabilities	128,437	162,034
Noncurrent liabilities	(9,896)	(10,703)
Property and equipment	(16,440)	(15,683)
Current liabilities	(18,844)	(21,301)
Long-term investments	(2,989)	(3,158)
Inventory	(993)	(933)
AMT credit and other carryforwards	(34,383)	(30,956)
Exploration	(3,578)	(4,610)
Net operating loss (NOL) and other carryforwards	(39,244)	(48,444)
Total deferred tax assets	(142,267)	(137,002)
Valuation allowance	36,591	22,812
Net deferred tax assets	(105,676)	(114,190)
Net deferred tax liabilities	22,761	47,844
United States [Member]
Schedule Of Deferred Tax Assets (Liabilities) [Line Items]
Mine development costs	(86,905)	(98,204)
Canada [Member]
Schedule Of Deferred Tax Assets (Liabilities) [Line Items]
Mine development and mineral interests-Canada	(15,900)	(1,214)
South America [Member]
Schedule Of Deferred Tax Assets (Liabilities) [Line Items]
Mine development costs	$ (13,697)	$ (20,844)

Income Taxes (Reconciliation Of

Income Taxes (Reconciliation Of The Federal Income Tax Provision) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
(Loss) income before income taxes	$ (36,069)	$ 85,141	$ (395,726)
Income tax (benefit) provision at statutory rates	(12,624)	29,799	(138,504)
State income tax expense, net of federal benefit	50	3,553	3,995
Percentage depletion	(5,366)	(17,302)	(8,786)
Foreign currency transaction loss (gain), net	3,471	(1,353)	31,605
Compensation related adjustment	59	6	359
Change in valuation allowance	13,780	2,127	5,595
Return-to-provision	(1,259)	92	1,097
Impact of foreign operations	(2,981)	(52)	8,895
Rate adjustment	(7,290)	(96)	1,503
Other	(173)	(516)	588
Income tax (benefit) provision	$ (12,333)	$ 16,258	$ (93,653)

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax (Benefit) Provision) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current
Federal	$ 3,203	$ 13,902	$ 9,740
State	2,175	6,947	5,152
Current income tax	5,378	20,849	14,892
Deferred
Federal	(1,474)	(1,577)	5,278
State	(14,510)	(2,462)	252
Foreign	(1,727)	(552)	(114,075)
Deferred income tax benefit	(17,711)	(4,591)	(108,545)
Income tax (benefit) provision	$ (12,333)	$ 16,258	$ (93,653)

Income Taxes (Schedule of Earni

Income Taxes (Schedule of Earnings (Losses) Before Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income (Loss) From Continuing Operations Before Income Taxes, Minority Interest, And Income (Loss) From Equity Method Investments [Line Items]
Loss / income before income tax (benefit) provision	$ (36,069)	$ 85,141	$ (395,726)
United States [Member]
Income (Loss) From Continuing Operations Before Income Taxes, Minority Interest, And Income (Loss) From Equity Method Investments [Line Items]
Loss / income before income tax (benefit) provision	10,574	88,281	61,671
Foreign [Member]
Income (Loss) From Continuing Operations Before Income Taxes, Minority Interest, And Income (Loss) From Equity Method Investments [Line Items]
Loss / income before income tax (benefit) provision	$ (46,643)	$ (3,140)	$ (457,397)

Comprehensive (Loss) Income (Ch

Comprehensive (Loss) Income (Changes In Accumulated Other Comprehensive (Loss) Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes in Accumulated Other Comprehensive (Loss) [Roll Forward]
Balance at beginning of period, net of tax	$ 17	$ 6	$ (99)
Change in value, net of tax	(214)	11	105
Balance at end of period, net of tax	(197)	17	6
Available-for-sale marketable securities [Member]
Changes in Accumulated Other Comprehensive (Loss) [Roll Forward]
Balance at beginning of period, net of tax	17	6	(99)
Change in value, net of tax	(384)	11	105
Balance at end of period, net of tax	(367)	17	6
Deferred Compensation [Member]
Changes in Accumulated Other Comprehensive (Loss) [Roll Forward]
Balance at beginning of period, net of tax	0	0	0
Change in value, net of tax	170	0	0
Balance at end of period, net of tax	$ 170	$ 0	$ 0

Segment Information (Narrative)

Segment Information (Narrative) (Details) $ in Thousands	3 Months Ended				9 Months Ended	12 Months Ended
	Jun. 30, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Sep. 30, 2013USD ($)	Sep. 30, 2013USD ($)	Dec. 31, 2015USD ($)SegmentBusiness_Component	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Segment Reporting Information [Line Items]
Number of reportable business segments | Segment						5
Impairment charge						$ 46,772	$ 550	$ 461,755
Marathon Properties [Member]
Segment Reporting Information [Line Items]
Impairment charge			$ 171,400					$ 171,400
San Juan, Argentina [Member] | Altar Property [Member]
Segment Reporting Information [Line Items]
Impairment charge				$ 290,400	$ 290,400
Mine Production [Member]
Segment Reporting Information [Line Items]
Number of business components | Business_Component						2
Marathon Properties [Member]
Segment Reporting Information [Line Items]
Impairment charge	$ 46,800	$ 500

Segment Information (Financial

Segment Information (Financial Information Related To The Company's Business Segments) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 171,985	$ 168,441	$ 185,384	$ 200,520	$ 222,167	$ 252,066	$ 249,887	$ 219,499	$ 726,330	$ 943,619	$ 1,039,506
Depletion, depreciation and amortization									65,149	67,406	59,317
General and administrative expenses									34,033	35,067	46,577
Interest income									2,955	3,551	4,481
Interest expense									20,187	22,719	22,957
Income (loss) before impairment charge and income taxes									10,703	85,691	66,029
Impairment charge									46,772	550	461,755
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)									(36,069)	85,141	(395,726)
Capital expenditures									107,434	119,682	129,029
Total assets	1,282,210				1,399,327				1,282,210	1,399,327	1,346,680
Operating Segments [Member] | Mine Production [Member]
Segment Reporting Information [Line Items]
Revenues									415,774	536,010	478,918
Depletion, depreciation and amortization									64,200	66,387	58,201
General and administrative expenses									0	0	0
Interest income									0	0	0
Interest expense									0	0	0
Income (loss) before impairment charge and income taxes									57,618	136,990	106,122
Impairment charge									0	0	0
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)									57,618	136,990	106,122
Capital expenditures									100,725	115,147	108,527
Total assets	613,498				596,653				613,498	596,653	553,153
Operating Segments [Member] | PGM Recycling [Member]
Segment Reporting Information [Line Items]
Revenues									310,156	401,684	560,588
Depletion, depreciation and amortization									949	1,019	1,116
General and administrative expenses									0	0	0
Interest income									1,653	2,535	3,375
Interest expense									0	0	0
Income (loss) before impairment charge and income taxes									10,151	11,719	35,463
Impairment charge									0	0	0
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)									10,151	11,719	35,463
Capital expenditures									327	181	330
Total assets	40,757				65,513				40,757	65,513	80,555
Operating Segments [Member] | Canadian Properties [Member]
Segment Reporting Information [Line Items]
Revenues									0	0	0
Depletion, depreciation and amortization									0	0	0
General and administrative expenses									1,146	3,251	1,112
Interest income									7	6	20
Interest expense									0	1	0
Income (loss) before impairment charge and income taxes									(1,910)	(4,581)	(4,255)
Impairment charge									46,772	550	171,338
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)									(48,682)	(5,131)	(175,593)
Capital expenditures									46	0	12,380
Total assets	26,517				75,250				26,517	75,250	83,800
Operating Segments [Member] | South American Properties [Member]
Segment Reporting Information [Line Items]
Revenues									0	0	0
Depletion, depreciation and amortization									0	0	0
General and administrative expenses									504	337	2,549
Interest income									27	68	184
Interest expense									0	0	0
Income (loss) before impairment charge and income taxes									2,218	2,600	8,845
Impairment charge									0	0	290,417
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)									2,218	2,600	(281,572)
Capital expenditures									0	45	101
Total assets	103,774				106,947				103,774	106,947	109,960
Operating Segments [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Revenues									400	5,925	0
Depletion, depreciation and amortization									0	0	0
General and administrative expenses									32,383	31,479	42,916
Interest income									1,268	942	902
Interest expense									20,187	22,718	22,957
Income (loss) before impairment charge and income taxes									(57,374)	(61,037)	(80,146)
Impairment charge									0	0	0
(LOSS) INCOME BEFORE INCOME TAX BENEFIT (PROVISION)									(57,374)	(61,037)	(80,146)
Capital expenditures									6,336	4,309	7,691
Total assets	$ 497,664				$ 554,964				$ 497,664	$ 554,964	$ 519,212

Investments (Narrative) (Detail

Investments (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Letters of credit	$ 17,500
Loss on long-term investments	372	$ 125	$ 1,894
Collateral Pledged [Member]
Schedule of Available-for-sale Securities [Line Items]
Commercial Paper	18,500
Fair Value, Measurements, Nonrecurring [Member]
Schedule of Available-for-sale Securities [Line Items]
Long-term investments	524	896
Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Schedule of Available-for-sale Securities [Line Items]
Long-term investments	$ 524	$ 896

Investments (Available-for-sale

Investments (Available-for-sale Securities by Major Security Type and Class) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities [Abstract]
Amortized Cost	$ 317,488	$ 251,847
Gross unrealized gains	261	320
Gross unrealized losses	(577)	(290)
Fair market value	317,172	251,877
Cash Equivalents [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	317,006	251,503
Gross unrealized gains	0	41
Gross unrealized losses	(577)	(290)
Fair market value	316,429	251,254
Federal agency notes [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	285,276	143,132
Gross unrealized gains	0	40
Gross unrealized losses	(519)	(33)
Fair market value	284,757	143,139
Commercial paper [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	31,730	108,371
Gross unrealized gains	0	1
Gross unrealized losses	(58)	(257)
Fair market value	31,672	108,115
Mutual funds [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	482	344
Gross unrealized gains	261	279
Gross unrealized losses	0	0
Fair market value	$ 743	$ 623

Investments (Maturities of Avai

Investments (Maturities of Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Amortized cost
Amortized Cost	$ 317,488	$ 251,847
Fair market value
Fair market value	317,172	251,877
Federal agency notes [Member]
Amortized cost
Due in one year or less	219,748
Due after one year through two years	65,528
Amortized Cost	285,276	143,132
Fair market value
Due in one year or less	219,581
Due after one year through two years	65,176
Fair market value	284,757	143,139
Commercial paper [Member]
Amortized cost
Due in one year or less	20,490
Due after one year through two years	11,240
Amortized Cost	31,730	108,371
Fair market value
Due in one year or less	20,472
Due after one year through two years	11,200
Fair market value	$ 31,672	$ 108,115

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Metals inventory
Raw ore	$ 4,234	$ 4,984
Concentrate and in-process	43,727	48,712
Finished goods	32,618	49,885
Metals inventory	80,579	103,581
Materials and supplies	21,493	26,726
Total inventory	$ 102,072	$ 130,307

Earnings Per Common Share (Narr

Earnings Per Common Share (Narrative) (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Options, Excluded Due To Net Loss [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive shares	182,546		98,218
Stock Options, Excluded due to Market Price Less Than Exercise Price [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive shares		34,259

Earnings Per Common Share (Comp

Earnings Per Common Share (Computation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Oct. 31, 2012
Basic EPS
Net income attributable to common stockholders	$ 4,424	$ (12,029)	$ (39,018)	$ 22,888	$ 14,351	$ 17,835	$ 17,658	$ 19,039	$ (11,928)	$ 70,297	$ (270,206)
Basic EPS, Weighted Average Shares (Denominator) (in shares)									120,809	119,953	118,607
Basic EPS, Per Share Amount (in usd per share)	$ 0.04	$ (0.10)	$ (0.23)	$ 0.19	$ 0.12	$ 0.15	$ 0.15	$ 0.16	$ (0.10)	$ 0.59	$ (2.28)
Effect of Dilutive Securities
Effect of stock options (in shares)										31
Effect of nonvested shares (in shares)										53
Effect of contingently issuable shares (in shares)										98
Diluted EPS
Net income attributable to common stockholders and assumed conversions										$ 86,910
Net income attributable to common stockholders and assumed conversions, Weighted Average Shares (Denominator) (in shares)									120,809	156,233	118,607
Net income attributable to common stockholders and assumed conversions, Per Share Amount (in usd per share)	$ 0.04	$ (0.10)	$ (0.23)	$ 0.17	$ 0.12	$ 0.14	$ 0.14	$ 0.15	$ (0.10)	$ 0.56	$ (2.28)
1.875% convertible debentures [Member]
Effect of Dilutive Securities
Effect of convertible debentures, net of tax and capitalized interest										$ 0
Effect of convertible debentures (in shares)										95
Diluted EPS
Debt instrument, stated rate	1.875%				1.875%				1.875%	1.875%		1.875%
1.75% convertible debentures [Member]
Effect of Dilutive Securities
Effect of convertible debentures, net of tax and capitalized interest										$ 16,613
Effect of convertible debentures (in shares)										36,003
Diluted EPS
Debt instrument, stated rate	1.75%				1.75%				1.75%	1.75%		1.75%

Debt and Capital Lease Obliga69

Debt and Capital Lease Obligations (Narrative) (Details)	1 Months Ended						3 Months Ended		12 Months Ended
	Jul. 31, 2014USD ($)	Mar. 31, 2013USD ($)	Oct. 31, 2012USD ($)$ / sharesshares	Jan. 31, 2012USD ($)	Dec. 31, 2011USD ($)	Mar. 31, 2008	Dec. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2000USD ($)
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt, net									$ (4,010,000)	$ 0	$ 0
Redemption of debt	$ 40,000
Line of Credit Facility, Termination Fees							$ 200,000
Capital Lease Obligations [Abstract]
Capital lease term									4 years
Capital lease obligations, principal and interest payments									$ 2,200,000	2,200,000
Capital lease obligations							$ 580,000		580,000
Capitalized Interest
Capitalized interest									6,000,000	5,100,000	4,800,000
Capital Lease Obligations [Member]
Capital Lease Obligations [Abstract]
Interest included in payments									$ 100,000	$ 200,000
1.75% convertible debentures [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 396,750,000
Debt instrument, stated rate			1.75%				1.75%		1.75%	1.75%
Convertible debentures conversion ratio			0.0604961
Debt conversion price (in usd per share) | $ / shares			$ 16.53
Number of shares for each warrant (in shares) | shares			30.2481
Warrant price (in dollars per share) | $ / shares			$ 16.53
Debt Instrument, Effective Term			7 years
Equity component of convertible debenture			$ 141,600,000
Debt issuance costs			$ 12,400,000
Debt issuance costs, amortization period			7 years
Net proceeds from the offering			$ 384,300,000
Extinguishment of Debt, Amount								$ 61,600,000
Repayments of Long-term Debt								59,400,000
Extinguishment of Debt, Reduction of Debt Component								50,700,000
Write Off Of Debt Discount								10,900,000
Reduction in debt issuance costs (repurchase of debt)								700,000	$ 747,000	$ 0	0
Gain (loss) on extinguishment of debt, net								(4,200,000)
Debt instrument, effective interest rate			8.50%
Balance outstanding, convertible debt							$ 258,400,000		258,400,000	291,100,000
Unamortized discount							$ 76,754,000		76,754,000	105,634,000
Capital Lease Obligations [Abstract]
Interest included in payments									$ 6,827,000	$ 6,943,000	6,905,000
1.875% convertible debentures [Member]
Debt Instrument [Line Items]
Debt instrument, stated rate			1.875%				1.875%		1.875%	1.875%
Convertible debentures conversion ratio						0.0425351
Repayments of convertible debt		$ 164,300,000
Extinguishment of Debt, Amount								1,700,000
Repayments of Long-term Debt								1,600,000
Balance outstanding, convertible debt							$ 500,000		$ 500,000
Capital Lease Obligations [Abstract]
Interest included in payments									42,000	$ 42,000	1,582,000
1.875% convertible debentures [Member] | Loss On Debt Extinguishment, Net [Member]
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt, net								$ 100,000
8% Series 2000 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 30,000,000
Debt instrument, stated rate												8.00%
Net proceeds from the offering												$ 28,700,000
Debt instrument, effective interest rate												8.57%
Capital Lease Obligations [Abstract]
Interest included in payments									$ 0	$ 1,240,000	$ 2,400,000
Credit Agreement [Member]
Debt Instrument [Line Items]
Debt issuance costs				$ 200,000	$ 1,100,000
Credit agreement, maximum borrowing capacity				$ 125,000,000	$ 100,000,000
Credit Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Unused capacity, commitment fee percentage				0.50%
Credit Agreement [Member] | Minimum [Member]
Debt Instrument [Line Items]
Unused capacity, commitment fee percentage				0.375%

Debt and Capital Lease Obliga70

Debt and Capital Lease Obligations (Amortization of Debt Issuance Costs, Interest Expense and Cash Payments) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Amortization of debt issuance costs		$ 2,211	$ 2,265	$ 1,664
1.75% convertible debentures [Member]
Debt Instrument [Line Items]
Amortization of debt issuance costs		925	1,120	1,139
Interest expense, net of capitalized interest		18,752	19,416	18,261
Reduction in debt issuance costs (repurchase of debt)	$ 700	747	0	0
Cash payments for interest		6,827	6,943	6,905
1.875% convertible debentures [Member]
Debt Instrument [Line Items]
Amortization of debt issuance costs		0	0	195
Interest expense, net of capitalized interest		0	42	684
Cash payments for interest		42	42	1,582
Credit Agreement [Member]
Debt Instrument [Line Items]
Amortization of debt issuance costs		539	272	272
Fees		1,168	1,026	1,082
8% Series 2000 [Member]
Debt Instrument [Line Items]
Amortization of debt issuance costs		0	873	58
Interest expense, net of capitalized interest		0	1,240	2,400
Cash payments for interest		$ 0	$ 1,240	$ 2,400

Debt and Capital Lease Obliga71

Debt and Capital Lease Obligations (Schedule of Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Current, Capital Lease Obligation	$ 580	$ 2,067
Long-Term, Capital Lease Obligation	0	580
Current, Small Land Purchase	77	77
Long-Term, Small Land Purchase	0	82
Current, Total debt balances	657	2,144
Long-term, Total debt balances	258,920	294,023
1.75% convertible debentures [Member]
Debt Instrument [Line Items]
Current, Aggregate principal	0	0
Long-Term, Aggregate principal	335,150	396,750
Long-Term, Debt discount	(76,754)	(105,634)
Long-Term, Debt balance	258,396	291,116
1.875% convertible debentures [Member]
Debt Instrument [Line Items]
Current, Aggregate principal	0	0
Long-Term, Aggregate principal	$ 524	$ 2,245

Debt and Capital Lease Obliga72

Debt and Capital Lease Obligations (Schedule of Future Minimum Lease Payments for Capital Leases) (Details) $ in Thousands	Dec. 31, 2015USD ($)
Capital Lease Obligations [Abstract]
2016 minimum lease payments	$ 589
Interest at rates ranging from 5.21% to 5.46% (before-tax)	(9)
Capital lease obligations	$ 580
Minimum [Member]
Capital Lease Obligations [Abstract]
Capital lease, interest rate	5.21%
Maximum [Member]
Capital Lease Obligations [Abstract]
Capital lease, interest rate	5.46%

Mineral Properties and Mine D73

Mineral Properties and Mine Development (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Mineral Properties [Line Items]
Impairment charge			$ 46,772	$ 550	$ 461,755
Marathon Properties [Member]
Schedule Of Mineral Properties [Line Items]
Impairment charge	$ 46,800	$ 500
Mineral properties, fair value	$ 8,600

Mineral Properties and Mine D74

Mineral Properties and Mine Development (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Mineral Properties and Mine Development [Abstract]
Total mineral properties and mine development, net	$ 573,231	$ 569,006
Mineral Properties and Mine Development [Member]
Mineral Properties and Mine Development [Abstract]
Mineral Properties and Mine Development, Gross	1,030,542	980,607
Accumulated depletion and amortization	(457,311)	(411,601)
Mining Properties and Mineral Rights [Member] | Stillwater Mine [Member] | Montana, United States of America [Member]
Mineral Properties and Mine Development [Abstract]
Mineral Properties and Mine Development, Gross	1,950	1,950
Mining Properties and Mineral Rights [Member] | Marathon Properties [Member] | Ontario, Canada [Member]
Mineral Properties and Mine Development [Abstract]
Mineral Properties and Mine Development, Gross	8,560	55,332
Mining Properties and Mineral Rights [Member] | Altar Property [Member] | San Juan, Argentina [Member]
Mineral Properties and Mine Development [Abstract]
Mineral Properties and Mine Development, Gross	101,970	101,970
Mine Development [Member] | Stillwater Mine [Member] | Montana, United States of America [Member]
Mineral Properties and Mine Development [Abstract]
Mineral Properties and Mine Development, Gross	697,781	616,872
Mine Development [Member] | East Boulder Mine [Member] | Montana, United States of America [Member]
Mineral Properties and Mine Development [Abstract]
Mineral Properties and Mine Development, Gross	$ 220,281	$ 204,483

Property, Plant and Equipment75

Property, Plant and Equipment (Schedule of Property, Plant and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 351,792	$ 337,832
Accumulated depreciation	(241,835)	(218,951)
Total property, plant, and equipment, net	109,957	118,881
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	161,292	152,421
Building and Structural Components [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	173,580	169,609
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	11,740	9,488
Construction-in-Progress [Member] | Stillwater Mine [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,615	2,633
Construction-in-Progress [Member] | East Boulder Mine [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	435	1,539
Construction-in-Progress [Member] | Marathon Properties [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	148	148
Construction-in-Progress [Member] | Processing Facilities and Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,982	$ 1,994

Property, Plant and Equipment76

Property, Plant and Equipment (Schedule Of Capital Expenditures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Total capital outlay	$ 111,850	$ 129,813	$ 138,536
Non-cash capitalized interest / depreciation	(9,347)	(8,443)	(8,910)
Change in accounts payable for capital expenditures	4,931	(1,688)	(597)
Total cash paid	107,434	119,682	129,029
Stillwater Mine [Member]
Property, Plant and Equipment [Line Items]
Total capital outlay	88,799	95,038	90,827
East Boulder Mine [Member]
Property, Plant and Equipment [Line Items]
Total capital outlay	17,916	28,813	25,928
Marathon project [Member]
Property, Plant and Equipment [Line Items]
Total capital outlay	0	0	14,081
Altar Project [Member]
Property, Plant and Equipment [Line Items]
Total capital outlay	46	45	101
Other [Member]
Property, Plant and Equipment [Line Items]
Total capital outlay	$ 5,089	$ 5,917	$ 7,599

Asset Retirement Obligation (Na

Asset Retirement Obligation (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Asset Retirement Obligations [Line Items]
Current financial guarantee requirements				$ 40,100,000
Stillwater Mine [Member]
Asset Retirement Obligations [Line Items]
Liabilities incurred	$ 1,100,000	$ 0	$ 0

Asset Retirement Obligation (Ch

Asset Retirement Obligation (Changes In Asset Retirement Obligation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	$ 9,401	$ 8,654	$ 7,965
Accretion expense	812	747	689
Additions and changes in estimates	814
Ending Balance	11,027	9,401	8,654
Stillwater Mine [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	8,720	8,020	7,381
Accretion expense	777	700	639
Additions and changes in estimates	1,115
Ending Balance	10,612	8,720	8,020
East Boulder Mine [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	681	634	584
Accretion expense	35	47	50
Additions and changes in estimates	(301)
Ending Balance	$ 415	$ 681	$ 634

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details)	Dec. 31, 2015	Dec. 31, 2014	Oct. 31, 2012
1.75% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, stated rate	1.75%	1.75%	1.75%
1.875% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, stated rate	1.875%	1.875%	1.875%

Fair Value Measurements (Financ

Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 316,429	$ 251,254
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund	54,761	120,000
Mutual funds	743	623
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund	54,761	120,000
Mutual funds	743	623
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund	0	0
Mutual funds	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund	0	0
Mutual funds	0	0
Fair Value, Measurements, Recurring [Member] | Federal agency notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	284,757	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	284,757	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	31,672	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	31,672	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 (Fina81

Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Nonrecurring Basis) (Details) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Certain Marathon real estate properties		$ 754
Long-term investments	$ 524	896
1.875% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	524	2,245
1.75% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	285,446	303,108
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Certain Marathon real estate properties		0
Long-term investments	524	896
Level 1 [Member] | 1.875% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	0	0
Level 1 [Member] | 1.75% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	0	0
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Certain Marathon real estate properties		0
Long-term investments	0	0
Level 2 [Member] | 1.875% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	524	2,245
Level 2 [Member] | 1.75% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	285,446	303,108
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Certain Marathon real estate properties		754
Long-term investments	0	0
Level 3 [Member] | 1.875% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	0	0
Level 3 [Member] | 1.75% convertible debentures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debentures	$ 0	$ 0

Related Parties (Details)

Related Parties (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Noncontrolling interest ownership percentage					25.00%
Percent of noncontrolling interest purchased	25.00%
Affiliated Entity [Member]
Related Party Transaction [Line Items]
PGM sales to related party		$ 38.7	$ 141.7	$ 296.6
Stillwater Canada, Inc. [Member]
Related Party Transaction [Line Items]
Noncontrolling interest ownership percentage	25.00%		25.00%	25.00%
Percent of noncontrolling interest purchased	25.00%
Stillwater Canada, Inc. [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Noncontrolling interest ownership percentage	25.00%

Commitments and Contingencies83

Commitments and Contingencies (Narrative) (Details) $ in Millions	Jan. 29, 2016	Dec. 15, 2015	Sep. 01, 2015	Dec. 31, 2015USD ($)employeeagreement	Dec. 31, 2014USD ($)employee	Dec. 31, 2013USD ($)
Related Party Transaction [Line Items]
Total rental expense for cancelable and non-cancelable operating leases | $				$ 1.8	$ 2	$ 2.3
Number of collective bargaining agreements | agreement				2
Collective bargaining agreement, term		4 years
Collective bargaining agreement, number of years of no increase in base wages		2 years	2 years
Collective bargaining agreement, number of employees				1,439	1,619
Active labor force covered by collective bargaining arrangements expiring on June 1, 2015 [Member]
Related Party Transaction [Line Items]
Percentage of active labor force covered by collective bargaining agreements				56.00%
Active labor force covered by collective bargaining arrangements expiring on December 1, 2015 [Member]
Related Party Transaction [Line Items]
Percentage of active labor force covered by collective bargaining agreements				22.00%
Montana and Colorado [Member]
Related Party Transaction [Line Items]
Collective bargaining agreement, number of employees				1,430	1,609
Canada and South America [Member]
Related Party Transaction [Line Items]
Collective bargaining agreement, number of employees				9	10
Subsequent Event [Member]
Related Party Transaction [Line Items]
Collective bargaining agreement, term	4 years

Commitments and Contingencies84

Commitments and Contingencies (Future Minimum Lease Payments For Operating Leases) (Details) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 150
2,017	148
2,018	120
2,019	66
Total	$ 484

Commitments and Contingencies85

Commitments and Contingencies (Percentage Of Total Revenues From Significant Customers) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	75.00%	66.00%	69.00%
Revenues [Member] | Customer Concentration Risk [Member] | Customer A [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	75.00%	51.00%	14.00%
Revenues [Member] | Customer Concentration Risk [Member] | Customer B [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	0.00%	15.00%	29.00%
Revenues [Member] | Customer Concentration Risk [Member] | Customer C [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	0.00%	0.00%	14.00%
Revenues [Member] | Customer Concentration Risk [Member] | Customer D [Member]
Revenue, Major Customer [Line Items]
Concentration Risk, Percentage	0.00%	0.00%	12.00%

Quarterly Data (Unaudited) (Det

Quarterly Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 171,985	$ 168,441	$ 185,384	$ 200,520	$ 222,167	$ 252,066	$ 249,887	$ 219,499	$ 726,330	$ 943,619	$ 1,039,506
Depletion, depreciation and amortization	15,468	15,362	17,198	17,121	17,272	17,181	17,802	15,151	65,149	67,406	59,317
Operating income (loss)	129	(6,181)	(34,812)	21,170	18,948	26,758	27,484	24,977	(19,694)	98,168	(396,623)
Net income (loss)	4,424	(12,029)	(39,018)	22,888	14,351	17,835	17,658	19,039	(11,928)	70,297	(270,206)
Comprehensive income attributable to common stockholders	$ 4,061	$ (11,912)	$ (27,429)	$ 23,139	$ 14,735	$ 17,965	$ 18,073	$ 19,535	$ (12,142)	$ 70,308	$ (270,101)
Basic earnings (loss) per share attributable to common stockholders (in usd per share)	$ 0.04	$ (0.10)	$ (0.23)	$ 0.19	$ 0.12	$ 0.15	$ 0.15	$ 0.16	$ (0.10)	$ 0.59	$ (2.28)
Diluted earnings (loss) per share attributable to common stockholders (in usd per share)	$ 0.04	$ (0.10)	$ (0.23)	$ 0.17	$ 0.12	$ 0.14	$ 0.14	$ 0.15	$ (0.10)	$ 0.56	$ (2.28)