ATI (ATI) 10-K 26 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 13, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Entity Registrant Name	ALLEGHENY TECHNOLOGIES INCORPORATED
Entity Central Index Key	1018963
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding		108,629,452
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Entity Public Float			$4.90

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Sales	$4,223.40	$4,043.50	$4,666.90
Costs and expenses:
Cost of sales	3,844.80	3,790.90	4,041.40
Selling and administrative expenses	272.5	276.4	321.6
Restructuring costs	0	67.5	0
Income (loss) before interest, other income and income taxes	106.1	-91.3	303.9
Interest expense, net	-108.7	-65.2	-71.6
Other income, net	4.1	1.7	0
Income (loss) from continuing operations before income taxes	1.5	-154.8	232.3
Income tax provision (benefit)	-8.7	-63.6	72.4
Income (loss) from continuing operations	10.2	-91.2	159.9
Income (loss) from discontinued operations, net of tax	-0.6	252.8	7.9
Net income	9.6	161.6	167.8
Less: Net income attributable to noncontrolling interests	12.2	7.6	9.4
Net income (loss) attributable to ATI	-2.6	154	158.4
Basic net income (loss) per common share
Continuing operations attributable to ATI per common share (in dollars per share)	($0.02)	($0.93)	$1.42
Discontinued operations attributable to ATI per common share (in dollars per share)	($0.01)	$2.37	$0.07
Basic net income attributable to ATI per common share (in dollars per share)	($0.03)	$1.44	$1.49
Diluted net income (loss) per common share
Continuing operations attributable to ATI per common share (in dollars per share)	($0.02)	($0.93)	$1.36
Discontinued operations attributable to ATI per common share (in dollars per share)	($0.01)	$2.37	$0.07
Diluted net income attributable to ATI per common share (in dollars per share)	($0.03)	$1.44	$1.43
Income (loss) from continuing operations, net of tax	-2	-98.8	150.5
Income (loss) from discontinued operations, net of tax	($0.60)	$252.80	$7.90

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$9.60	$161.60	$167.80
Currency translation adjustment
Unrealized net change arising during the period	-34.1	13.8	14.3
Reclassification adjustment included in net income	0.5	1.5	0
Total	-33.6	15.3	14.3
Unrealized holding gain (loss) on securities
Net gain arising during the period	0	0.1	0
Derivatives
Net derivatives gain (loss) on hedge transactions	45.7	-25.2	-9.8
Reclassification to net income of net realized loss (gain)	-3.6	14	5.2
Income taxes on derivative transactions	16.2	-4.3	-1.8
Total	25.9	-6.9	-2.8
Postretirement benefit plans- Actuarial loss
Amortization of net actuarial loss	88.1	129	119.8
Net gain (loss) arising during the period	-424.5	384.9	-272.7
Postretirement benefit plans- Prior Service Cost
Amortization to net income of net prior service credits	-0.7	-15.2	-11.8
Income taxes on postretirement benefit plans	-124.5	187.6	-67.3
Total	-212.6	311.1	-97.4
Other comprehensive income (loss), net of tax	-220.3	319.6	-85.9
Comprehensive income (loss)	-210.7	481.2	81.9
Less: Comprehensive income attributable to noncontrolling interests	10.1	11	11.3
Comprehensive income (loss) attributable to ATI	($220.80)	$470.20	$70.60

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Assets
Cash and cash equivalents	$269.50	$1,026.80
Accounts receivable, net	603.6	528.2
Inventories, net	1,472.80	1,322.10
Prepaid expenses and other current assets	136.2	73.7
Total Current Assets	2,482.10	2,950.80
Property, plant and equipment, net	2,961.80	2,874.10
Cost in excess of net assets acquired	780.4	727.9
Other assets	358.3	345.7
Total Assets	6,582.60	6,898.50
Liabilities and Stockholders’ Equity
Accounts payable	556.7	471.8
Accrued liabilities	323.2	315.8
Deferred income taxes	62.2	3.5
Short-term debt and current portion of long-term debt	17.8	419.9
Total Current Liabilities	959.9	1,211
Long-term debt	1,509.10	1,527.40
Accrued postretirement benefits	415.8	442.4
Pension liabilities	739.3	368.2
Deferred income taxes	80.9	206.6
Other long-term liabilities	156.2	148.2
Total Liabilities	3,861.20	3,903.80
Redeemable noncontrolling interest	12.1	0
ATI Stockholders’ Equity:
Preferred stock, par value $0.10: authorized-50,000,000 shares; issued-none	0	0
Common stock, par value $0.10: authorized-500,000,000 shares; issued-109,695,171 shares at December 31, 2014 and 2013; outstanding-108,710,914 shares at December 31, 2014 and 107,983,360 shares at December 31, 2013	11	11
Additional paid-in capital	1,164.20	1,185.90
Retained earnings	2,398.90	2,490.10
Treasury stock: 984,257 shares at December 31, 2014 and 1,711,811 shares at December 31, 2013	-44.3	-79.6
Accumulated other comprehensive loss, net of tax	-931.4	-713.2
Total ATI Stockholders’ Equity	2,598.40	2,894.20
Noncontrolling interests
Noncontrolling Interests	110.9	100.5
Total Stockholders’ Equity	2,709.30	2,994.70
Total Liabilities and Stockholders’ Equity	$6,582.60	$6,898.50

Consolidated_Balance_Sheets_PA

Consolidated Balance Sheets (PARENTHETICAL) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Preferred stock, par value	$0.10	$0.10
Preferred stock, authorized	50,000,000	50,000,000
Preferred stock, issued	0	0
Common stock, par value	$0.10	$0.10
Common stock, authorized	500,000,000	500,000,000
Common stock, issued	109,695,171	109,695,171
Common stock, oustanding	108,710,914	107,983,360
Treasury Stock	984,257	1,711,811

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Activities:
Net income	$9.60	$161.60	$167.80
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	176.8	189.9	194
Deferred taxes	31.7	70.1	-19.4
Non-cash restructuring costs	0	72.7	13
Gain on sale of business	0	-428.3	0
Change in operating assets and liabilities:
Retirement benefits	3.1	70.6	58.9
Accounts receivable	-70.3	41.1	95.8
Inventories	-143.7	146.6	-152.3
Accounts payable	82.1	-7.8	9.2
Accrued income taxes	-37.5	-25.5	9.4
Accrued liabilities and other	4.1	77.4	51.1
Cash provided by operating activities	55.9	368.4	427.5
Investing Activities:
Purchases of property, plant and equipment	-225.7	-612.7	-382
Proceeds from sale of business, net of transaction costs	0	600.9	0
Purchases of businesses, net of cash acquired	-92.9	0	0
Asset disposals and other	2.4	0.8	3.3
Cash used in investing activities	-316.2	-11	-378.7
Financing Activities:
Issuances of long-term debt	0	500	0
Payments on long-term debt and capital leases	-414.9	-17.1	-16.7
Net repayments under credit facilities	0	-14.4	-10.4
Debt issuance costs	-1.2	-5.2	0
Dividends paid to shareholders	-77.1	-76.9	-76.5
Dividends paid to noncontrolling interests	0	-18	0
Shares repurchased for income tax withholding on share-based compensation	-3.9	-6.6	-23.4
Taxes on share-based compensation	0	2.6	0
Exercises of stock options and other	0.1	0.4	2.2
Cash provided by (used in) financing activities	-497	364.8	-124.8
Increase (decrease) in cash and cash equivalents	-757.3	722.2	-76
Cash and cash equivalents at beginning of year	1,026.80	304.6	380.6
Cash and cash equivalents at end of year	$269.50	$1,026.80	$304.60

Statements_of_Changes_in_Conso

Statements of Changes in Consolidated Equity (USD $)	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
In Millions, unless otherwise specified
Beginning balance at Dec. 31, 2011	$2,571.60	$11	$1,207.10	$2,361.50	($162.70)	($941.60)	$96.30
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	167.8			158.4			9.4
Other comprehensive income (loss)	-85.9					-87.8	1.9
Cash dividends on common stock ($0.72 per share)	-76.5			-76.5
Purchase of subsidiary shares from noncontrolling interest	-0.1						-0.1
Employee Stock Plans	10.2		-25.4	-15.8	51.4
Ending balance at Dec. 31, 2012	2,587.10	11	1,181.70	2,427.60	-111.3	-1,029.40	107.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	161.6			154			7.6
Other comprehensive income (loss)	319.6					316.2	3.4
Cash dividends on common stock ($0.72 per share)	-76.9			-76.9
Dividends paid to noncontrolling interest	-18						-18
Employee Stock Plans	21.3		4.2	-14.6	31.7
Ending balance at Dec. 31, 2013	2,994.70	11	1,185.90	2,490.10	-79.6	-713.2	100.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	9.6			-2.6			12.2
Other comprehensive income (loss)	-220.3					-218.2	-2.1
Cash dividends on common stock ($0.72 per share)	-77.1			-77.1
Conversion of convertible notes	5			-0.5	5.5
Redeemable noncontrolling interest	0			-0.3			0.3
Employee Stock Plans	-2.6		-21.7	-10.7	29.8
Ending balance at Dec. 31, 2014	$2,709.30	$11	$1,164.20	$2,398.90	($44.30)	($931.40)	$110.90

Statements_of_Changes_in_Conso1

Statements of Changes in Consolidated Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Stockholders' Equity [Abstract]
Cash dividends on common stock per share	$0.72	$0.72	$0.72

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies
	Principles of Consolidation
	The consolidated financial statements include the accounts of Allegheny Technologies Incorporated and its subsidiaries, including the Chinese joint venture known as Shanghai STAL Precision Stainless Steel Company Limited (“STAL”), in which the Company has a 60% interest. The remaining 40% interest in STAL is owned by Baosteel Group, a state authorized investment company whose equity securities are publicly traded in the People’s Republic of China. The financial results of STAL are consolidated into the Company’s operating results and financial position, with the 40% interest of our minority partner recognized in the consolidated statement of income as net income attributable to noncontrolling interests and as equity attributable to the noncontrolling interest within total stockholders’ equity. Investments in which the Company exercises significant influence, but which it does not control (generally a 20% to 50% ownership interest), including ATI’s 50% interest in the industrial titanium joint venture known as Uniti LLC (“Uniti”), are accounted for under the equity method of accounting. Accounts receivable from Uniti were $4.3 million and $3.1 million at December 31, 2014 and 2013, respectively. Significant intercompany accounts and transactions have been eliminated. Unless the context requires otherwise, “Allegheny Technologies,” “ATI” and the “Company” refer to Allegheny Technologies Incorporated and its subsidiaries.
	Basis of Presentation
	ATI’s strategic vision is to be an aligned and integrated specialty materials and components company. In connection with this initiative, in the first quarter of 2014, the High Performance Metals segment was renamed the High Performance Materials & Components segment. Individual business unit names within each segment were also changed to reflect their aligned and integrated product focus. There was no change to the business units that comprise each business segment or the manner in which resources are allocated and performance is assessed for the business units by management. Therefore, there was no change to business segment reporting as a result of this initiative. Certain prior year amounts have been reclassified in order to conform with 2014 presentation.
	Risks and Uncertainties and Use of Estimates
	The preparation of consolidated financial statements in conformity with United States generally accepted accounting principles requires management to make estimates and assumptions that affect reported amounts of assets and liabilities at the date of the financial statements, as well as the reported amounts of income and expenses during the reporting period. Actual results could differ from those estimates. Management believes that the estimates are reasonable.
	The Company markets its products to a diverse customer base, principally throughout the United States. No single customer accounted for more than 10% of sales for any year presented. The principal end markets for the ATI’s products are customers in the aerospace and defense, oil & gas/chemical process industry, electrical energy, automotive, construction and mining, food equipment and appliances, and medical markets.
	ATI has approximately 9,700 full-time employees, of which approximately 15% are located outside the United States. Approximately 50% of ATI’s workforce is covered by various collective bargaining agreements (“CBAs”), predominantly with the United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union (“USW”). Certain of these CBAs expire in 2015, including CBAs with the USW for approximately 2,300 Flat Rolled Products segment production, office and maintenance employees and approximately 150 production and maintenance employees in a High Performance Materials & Components segment Albany, Oregon facility, which will expire on June 30, 2015.
	Cash Equivalents and Investments
	Cash equivalents are highly liquid investments valued at cost, which approximates fair value, acquired with an original maturity of three months or less.
	Accounts Receivable
	Accounts receivable are presented net of a reserve for doubtful accounts of $4.8 million at December 31, 2014 and $5.3 million at December 31, 2013. Trade credit is extended based upon evaluations of each customer’s ability to perform its obligations, which are updated periodically. Accounts receivable reserves are determined based upon an aging of accounts and a review for collectability of specific accounts.
	Inventories
	Inventories are stated at the lower of cost (last-in, first-out (LIFO), first-in, first-out (FIFO), and average cost methods) or market, less progress payments. Costs include direct material, direct labor and applicable manufacturing and engineering overhead, and other direct costs. Most of the Company’s inventory is valued utilizing the LIFO costing methodology. Inventory of the Company’s non-U.S. operations is valued using average cost or FIFO methods.
	The Company evaluates product lines on a quarterly basis to identify inventory carrying values that exceed estimated net realizable value. In applying the lower of cost or market principle, market means current replacement cost, subject to a ceiling (market value shall not exceed net realizable value) and a floor (market shall not be less than net realizable value reduced by an allowance for a normal profit margin). The calculation of a resulting reserve, if any, is recognized as an expense in the period that the need for the reserve is identified. However, in cases where inventory at FIFO cost is lower than the LIFO carrying value, a write-down of the inventory to market may be required, subject to the ceiling and floor. It is the Company’s general policy to write-down to scrap value any inventory that is identified as obsolete and any inventory that has aged or has not moved in more than twelve months. In some instances this criterion is up to twenty-four months.
	Long-Lived Assets
	Property, plant and equipment are recorded at cost, including capitalized interest, and includes long-lived assets acquired under capital leases. The principal method of depreciation adopted for all property placed into service after July 1, 1996 is the straight-line method. For buildings and equipment acquired prior to July 1, 1996, depreciation is computed using a combination of accelerated and straight-line methods. Property, plant and equipment associated with the Company’s Rowley titanium sponge facility in the High Performance Materials & Components segment, and the Hot-Rolling and Processing Facility (HRPF) in the Flat Rolled Products segment, are being depreciated utilizing the units of production method of depreciation, which the Company believes provides a better matching of costs and revenues. The Company periodically reviews estimates of useful life and production capacity assigned to new and in service assets. Significant enhancements, including major maintenance activities that extend the lives of property and equipment, are capitalized. Costs related to repairs and maintenance are charged to expense in the period incurred. The cost and related accumulated depreciation of property and equipment retired or disposed of are removed from the accounts and any related gains or losses are included in income.
	The Company monitors the recoverability of the carrying value of its long-lived assets. An impairment charge is recognized when an indicator of impairment occurs and the expected net undiscounted future cash flows from an asset’s use (including any proceeds from disposition) are less than the asset’s carrying value and the asset’s carrying value exceeds its fair value. Assets to be disposed of by sale are stated at the lower of their fair values or carrying amounts and depreciation is no longer recognized.
	Cost in Excess of Net Assets Acquired
	At December 31, 2014, the Company had $780.4 million of goodwill on its consolidated balance sheet. Of the total, $653.8 million related to the High Performance Materials & Components segment and $126.6 million related to the Flat Rolled Products segment. Goodwill increased $55.0 million in 2014 from the acquisitions of Dynamic Flowform Corp. and Hanard Machine, Inc. (see Note 2) which was partially offset by a decrease of $2.5 million as a result of the impact of foreign currency translation on goodwill denominated in functional currencies other than the U.S. dollar. Goodwill is reviewed annually for impairment or more frequently if impairment indicators arise. The review for goodwill impairment requires a comparison of the fair value of each reporting unit that has goodwill associated with its operations with its carrying amount, including goodwill. If this comparison reflects impairment, then the loss would be measured as the excess of recorded goodwill over its implied fair value. Implied fair value is the excess of the fair value of the reporting unit over the fair value of all recognized and unrecognized assets and liabilities.
	Generally accepted accounting standards provide the option to qualitatively assess goodwill for impairment before completing a quantitative assessment. Under the qualitative approach, if, after assessing the totality of events or circumstances, including both macroeconomic, industry and market factors, and entity-specific factors, the Company determines it is likely (more likely than not) that the fair value of a reporting unit is greater than its carrying amount, then the quantitative impairment analysis is not required. The quantitative assessment may be performed each year for a reporting unit at the Company’s option without first performing a qualitative assessment. The Company’s quantitative assessment of goodwill for possible impairment includes estimating the fair market value of a reporting unit which has goodwill associated with its operations using discounted cash flow and multiples of cash earnings valuation techniques, plus valuation comparisons to recent public sale transactions of similar businesses, if any. These impairment assessments and valuation methods require the Company to make estimates and assumptions regarding future operating results, cash flows, changes in working capital and capital expenditures, selling prices, profitability, and the cost of capital. Many of these assumptions are determined by reference to market participants identified by the Company. Although management believes that the estimates and assumptions used were reasonable, actual results could differ from those estimates and assumptions.
	The Company performs the required annual goodwill impairment evaluations in the fourth quarter of each year. No impairments were determined to exist for the years ended December 31, 2014, 2013 or 2012. The fair values of all reporting units significantly exceeded the carrying values for the 2014 evaluation.
	Environmental
	Costs that mitigate or prevent future environmental contamination or extend the life, increase the capacity or improve the safety or efficiency of property utilized in current operations are capitalized. Other costs that relate to current operations or an existing condition caused by past operations are expensed. Environmental liabilities are recorded when the Company’s liability is probable and the costs are reasonably estimable, but generally not later than the completion of the feasibility study or the Company’s recommendation of a remedy or commitment to an appropriate plan of action. The accruals are reviewed periodically and, as investigations and remediations proceed, adjustments of the accruals are made to reflect new information as appropriate. Accruals for losses from environmental remediation obligations do not take into account the effects of inflation, and anticipated expenditures are not discounted to their present value. The accruals are not reduced by possible recoveries from insurance carriers or other third parties, but do reflect allocations among potentially responsible parties (“PRPs”) at Federal Superfund sites or similar state-managed sites after an assessment is made of the likelihood that such parties will fulfill their obligations at such sites and after appropriate cost-sharing or other agreements are entered. The measurement of environmental liabilities by the Company is based on currently available facts, present laws and regulations, and current technology. Such estimates take into consideration the Company’s prior experience in site investigation and remediation, the data concerning cleanup costs available from other companies and regulatory authorities, and the professional judgment of the Company’s environmental experts in consultation with outside environmental specialists, when necessary.
	Foreign Currency Translation
	Assets and liabilities of international operations are translated into U.S. dollars using year-end exchange rates, while revenues and expenses are translated at average exchange rates during the period. The resulting net translation adjustments are recorded as a component of accumulated other comprehensive income (loss) in stockholders’ equity.
	Sales Recognition
	Sales are recognized when title passes or as services are rendered.
	Research and Development
	Company funded research and development costs from continuing operations were $17.4 million in 2014, $16.1 million in 2013, and $22.3 million in 2012 and were expensed as incurred. Customer funded research and development costs were $2.7 million in 2014, $2.7 million in 2013, and $1.5 million in 2012.
	Stock-based Compensation
	The Company accounts for stock-based compensation transactions, such as nonvested stock and performance equity awards, using fair value. Compensation expense for an award is estimated at the date of grant and is recognized over the requisite service period. Compensation expense is adjusted for equity awards that do not vest because service or performance conditions are not satisfied. However, compensation expense already recognized is not adjusted if market conditions are not met, such as the Company’s total shareholder return performance relative to a peer group under the Company’s performance equity awards.
	Income Taxes
	The provision for, or benefit from, income taxes includes deferred taxes resulting from temporary differences in income for financial and tax purposes using the liability method. Such temporary differences result primarily from differences in the carrying value of assets and liabilities. Future realization of deferred income tax assets requires sufficient taxable income within the carryback, carryforward period available under tax law.
	The Company evaluates, on a quarterly basis whether, based on all available evidence, it is probable that the deferred income tax assets are realizable. Valuation allowances are established when it is estimated that it is more likely than not that the tax benefit of the deferred tax asset will not be realized. The evaluation includes the consideration of all available evidence, both positive and negative, regarding historical operating results including recent years with reported losses, the estimated timing of future reversals of existing taxable temporary differences, estimated future taxable income exclusive of reversing temporary differences and carryforwards, and potential tax planning strategies which may be employed to prevent an operating loss or tax credit carryforward from expiring unused.
	It is the Company’s policy to classify interest and penalties recognized on underpayment of income taxes as income tax expense.
	Net Income Per Common Share
	Basic and diluted net income per share are calculated by dividing the net income available to common stockholders by the weighted average number of common shares outstanding during the year. Diluted amounts assume the issuance of common stock for all potentially dilutive share equivalents outstanding. The calculations of all diluted income/loss per share figures for a period exclude the potentially dilutive effect of dilutive share equivalents if there is a net loss from continuing operations since the inclusion in the calculation of additional shares in the net loss from continuing operations per share would result in a lower per share loss and therefore be anti-dilutive.
	New Accounting Pronouncements Adopted
	In January 2014, the Company adopted changes issued by the Financial Accounting Standards Board (FASB) that require an entity to net its liability for unrecognized tax positions against a net operating loss carryforward, a similar tax loss or a tax credit carryforward when settlement in this manner is available under the tax law. The adoption of these changes had no impact on the consolidated financial statements.
	In January 2014, the Company adopted changes issued by the FASB to the accounting for obligations resulting from joint and several liability arrangements. This guidance requires an entity that is joint and severally liable to measure the obligation as the sum of the amount the entity has agreed with co-obligors to pay and any additional amount it expects to pay on behalf of one or more co-obligors. Required disclosures include a description of the nature of the arrangement, how the liability arose, the relationship with co-obligors and the terms and conditions of the arrangement. The adoption of these changes had no impact on the consolidated financial statements.
	In January 2014, the Company adopted changes issued by the FASB to a parent entity’s accounting for the cumulative translation adjustment (CTA) upon derecognition of certain subsidiaries or groups of assets within a foreign entity or of an investment in a foreign entity. The amendments specify that CTA should be released into earnings when an entity ceases to have a controlling financial interest in a subsidiary or group of assets within a consolidated foreign entity and the sale or transfer results in the complete or substantially complete liquidation of the foreign entity. For sales of an equity method investment that is a foreign entity, a pro rata portion of CTA attributable to the investment would be recognized in earnings when the investment is sold. When an entity sells either a part or all of its investment in a consolidated foreign entity, CTA would be recognized in earnings only if the sale results in the parent no longer having a controlling financial interest in the foreign entity. In addition, CTA should be recognized in earnings in a business combination achieved in stages (i.e., a step acquisition). The adoption of these changes had no impact on the consolidated financial statements.
	Pending Accounting Pronouncements
	In May 2014, the FASB issued changes to revenue recognition with customers. This update provides a five-step analysis of transactions to determine when and how revenue is recognized. An entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This update will be effective for the Company beginning in fiscal year 2017. This update may be applied retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying this update recognized at the date of initial application. The Company is currently evaluating the impact of the new guidance on its consolidated financial statements.
	In April 2014, the FASB issued changes to the criteria for reporting discontinued operations. Under the new criteria, a disposal of a component of an entity is required to be reported as discontinued operations only if the disposal represents a strategic shift that has, or will have, a major effect on an entity’s operations and financial results. The current criteria that there be no significant continuing involvement in the operations of the component after the disposal transaction has been removed under the new guidance. The new guidance also requires the presentation of the assets and liabilities of a disposal group that includes a discontinued operation for each comparative period and requires additional disclosures about discontinued operations, including the major line items constituting the pretax profit or loss of the discontinued operation, certain cash flow information for the discontinued operation, expanded disclosures about an entity’s significant continuing involvement in a discontinued operation, and disclosures about a disposal of an individually significant component of an entity that does not qualify for discontinued operations presentation. The provisions of the new guidance become effective for all disposals that occur for the Company beginning in fiscal year 2015. The Company does not anticipate a material impact to the consolidated financial statements upon adoption.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Acquisitions	Acquisitions
	On February 7, 2014, the Company acquired 85% of Dynamic Flowform Corp. (“Dynamic Flowform”) for $72.9 million of cash consideration, net of cash acquired. The Dynamic Flowform acquisition is treated as an asset purchase for tax purposes. The holders of the 15% noncontrolling interest have a put option requiring the Company to purchase their equity interest (see Note 17 for additional explanation). The Company also incurred $0.7 million of pre-tax costs related to the acquisition, consisting primarily of professional fees, which were recorded in selling and administrative expenses in the 2014 consolidated statement of operations.
	Based in Billerica, MA, Dynamic Flowform, which has been renamed ATI Flowform Products, uses precision flowforming process technologies to produce thin-walled components in net or near-net shapes across multiple alloy systems, including nickel-based alloys and superalloys, titanium and titanium alloys, zirconium alloys, and specialty and stainless alloys. Management expects this acquisition to expand the Company’s capabilities to produce specialty materials parts and components, primarily in the aerospace and defense, and oil & gas/chemical process industry markets. ATI Flowform Products results are included in the High Performance Materials & Components segment from the date of the acquisition.
	The purchase price allocation includes technology, trademarks and customer intangible assets of $21.4 million, which will be amortized over a 23 year weighted average life, and goodwill of $46.8 million, which is deductible for tax purposes. The final allocation of the purchase price was completed in the second quarter of 2014.
	In addition, on June 12, 2014, the Company acquired Hanard Machine, Inc. (“Hanard”) for $20.5 million of cash consideration, net of cash acquired, including $20.0 million paid in 2014 and $0.5 million that is expected to be paid in 2015. Located in Salem, OR, Hanard performs precision machining on parts and components made from titanium alloys, nickel-based alloys and superalloys, aluminum, specialty steel, and other ferrous and non-ferrous metals. The business operates as ATI Cast Products Salem Operations, and is reported as a part of the High Performance Materials & Components segment from the date of the acquisition. Management expects this acquisition to expand the Company’s capabilities to produce finished specialty materials parts and components and reinforces the Company’s important aerospace supply chain role.  The purchase price allocation includes technology and customer intangible assets of $4.3 million, which will be amortized over a 20 year life, and goodwill of $8.3 million, which is deductible for tax purposes. The final allocation of the purchase price is expected to be completed by the end of the first quarter of 2015.
	Pro forma financial information has not been included because these acquisitions did not meet certain significance thresholds individually or in the aggregate.

Discontinued_Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Discontinued Operations
	On November 4, 2013, the Company completed the sale of its tungsten materials business, which produces tungsten powder, tungsten heavy alloys, tungsten carbide materials, and carbide cutting tools. In 2013, the Company received cash proceeds, net of transaction costs, of $600.9 million on the sale of this business and recognized a $428.3 million pre-tax ($261.4 million after tax) gain which has been recorded in discontinued operations.
	Also, during 2013, the Company completed a strategic review of its iron castings and fabricated components businesses. These businesses were not projected to meet the Company’s long-term profitable growth and return on capital employed expectations, resulting in the closure of the fabricated components business and planned divestiture of the iron casting business in 2013. In April 2014, the Company announced the closure of the iron castings business, as the divestiture of this business through a sale process on commercially acceptable terms was unlikely to be successful. The orderly wind-down of operations was completed by the end of the third quarter 2014. The closure of the iron castings business resulted in $1.8 million of cash exit costs in 2014, primarily related to severance benefits, of which $1.0 million was paid in 2014. Payment of the remaining cash exit costs for the iron casting business is expected to be completed within the next twelve months.
	The operating results of the tungsten materials, iron castings and fabricated components businesses have been included in discontinued operations in the Company’s consolidated statements of income for all periods presented. Results of discontinued operations for 2014 include $1.8 million pre-tax of charges associated with the iron castings closure. Results of discontinued operations for 2013 include $19.5 million pre-tax ($11.9 million after-tax) of charges associated with the iron castings and fabricated components divestitures, including $18.6 million of pre-tax asset impairment charges. Results of discontinued operations for 2012 include a $13.0 million pre-tax ($8.8 million after-tax) charge to write down the value of the long-lived assets with the closing of the Alpena, MI iron casting facility.
	The following table presents summarized results for these discontinued operations (in millions):
		2014				2013		2012
	Sales	$	14.9			$	268.2	$	364.6
	Income (loss) before income taxes	$	(0.9	)		$	414.2	$	11.7
	Net liabilities of discontinued operations were $1.3 million at December 31, 2014 and were net assets of $4.2 million at December 31, 2013 and were reported as follows on the consolidated balance sheet (in millions):
		2014			2013
	Prepaid expenses and other current assets	$	0.4		$	6.1
	Other assets	1.4			3.7
	Total Assets	1.8			9.8
	Accrued liabilities	2.5			4.9
	Other long-term liabilities	0.6			0.7
	Total Liabilities	3.1			5.6
	Net Assets (Liabilities)	$	(1.3	)	$	4.2

Inventories

Inventories	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Inventories	Inventories
	Inventories at December 31, 2014 and 2013 were as follows (in millions):
		2014			2013
	Raw materials and supplies	$	249.3		$	277.6
	Work-in-process	1,184.10			984.9
	Finished goods	172.2			162.1
	Total inventories at current cost	1,605.60			1,424.60
	Adjustment from current cost to LIFO cost basis	4.8			29.4
	Inventory valuation reserves	(68.8		)	(84.3		)
	Progress payments	(68.8		)	(47.6		)
	Total inventories, net	$	1,472.80		$	1,322.10
	Inventories, before progress payments, determined on the LIFO method were $1,102.4 million at December 31, 2014, and $976.1 million at December 31, 2013. The remainder of the inventory was determined using the FIFO and average cost methods, and these inventory values do not differ materially from current cost. The effect of using the LIFO costing methodology to value inventory, rather than FIFO, increased cost of sales by $24.6 million in 2014. Fiscal years 2013 and 2012 included a decrease in cost of sales of $80.9 million and $75.6 million, respectively, from using the LIFO costing methodology. Due to deflationary impacts primarily related to raw materials, the carrying value of the Company’s inventory as valued on the LIFO inventory accounting method exceeded current replacement cost at December 31, 2013, and based on a lower of cost or market value analysis, a $35.0 million net realizable value reserve was recorded in the High Performance Materials & Components segment in 2013. This net realizable value reserve was reduced to $10.0 million at December 31, 2014. In addition, continued sluggish demand for industrial titanium products from global markets has resulted in much lower selling prices for these products. As a result, the Company recorded a lower of cost or market charge for industrial titanium products in the Flat Rolled Products segment of $23.2 million in 2014 and $20.5 million in 2013.
	During 2013, and 2012, inventory usage resulted in liquidations of LIFO inventory quantities, increasing cost of sales by $3.8 million and $1.5 million in 2013 and 2012, respectively. These inventories were carried at differing costs prevailing in prior years as compared with the cost of current manufacturing cost and purchases. There were no LIFO liquidations in 2014.

Property_Plant_And_Equipment

Property Plant And Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property Plant and Equipment	Property, Plant and Equipment
	Property, plant and equipment at December 31, 2014 and 2013 was as follows:
	(In millions)	2014			2013
	Land	$	30.2		$	30.2
	Buildings	1,048.90			1,019.10
	Equipment and leasehold improvements	3,702.50			3,526.00
		4,781.60			4,575.30
	Accumulated depreciation and amortization	(1,819.8		)	(1,701.2		)
	Total property, plant and equipment, net	$	2,961.80		$	2,874.10
	Construction in progress at December 31, 2014 and 2013 was $71.1 million and $186.2 million, respectively. Depreciation and amortization from continuing operations for the years ended December 31, 2014, 2013 and 2012 was as follows:
	(In millions)	2014			2013			2012
	Depreciation of property, plant and equipment	$	146.7		$	156.8		$	157
	Software and other amortization	29.9			23.8			24.4
	Total depreciation and amortization	$	176.6		$	180.6		$	181.4

Asset_Retirement_Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligation	Asset Retirement Obligations
	The Company maintains reserves where a legal obligation exists to perform an asset retirement activity and the fair value of the liability can be reasonably estimated. These asset retirement obligations (“AROs”) include liabilities where the timing and (or) method of settlement may be conditional on a future event, that may or may not be within the control of the entity. At December 31, 2014, the Company had recognized AROs of $25.4 million related to landfill closures, decommissioning costs, facility leases and conditional AROs associated with manufacturing activities using what may be characterized as potentially hazardous materials. The 2013 sale of the tungsten materials business included an indemnification to the buyer for conditional ARO costs of up to $13 million for a five year period. The Company recorded a $9.4 million charge in 2013 to increase recorded reserves to $13 million for these retained liabilities, which was reported as part of the gain on sale of the tungsten materials business. In addition, as part of facility closures in 2013, $4.2 million in decommissioning AROs were reported in continuing operations (see Note 16) on the 2013 consolidated statement of operations.
	Estimates of AROs are evaluated annually in the fourth quarter, or more frequently if material new information becomes known. Accounting for asset retirement obligations requires significant estimation and in certain cases, the Company has determined that an ARO exists, but the amount of the obligation is not reasonably estimable. The Company may determine that additional AROs are required to be recognized as new information becomes available.
	Changes in asset retirement obligations for the years ended December 31, 2014 and 2013 were as follows:
	(In millions)	2014			2013
	Balance at beginning of year	$	27.7		$	13
	Accretion expense	0.9			1.1
	Payments	(2.2		)	(0.8		)
	Revision of estimates	(1.0		)	13.8
	Liabilities incurred	—			0.6
	Balance at end of year	$	25.4		$	27.7

Supplemental_Financial_Stateme

Supplemental Financial Statement Information	12 Months Ended
	Dec. 31, 2014
Additional Financial Information Disclosure [Abstract]
Supplemental Financial Statement Information	Supplemental Financial Statement Information
	Cash and cash equivalents at December 31, 2014 and 2013 were as follows:
	(In millions)	2014				2013
	Cash	$	267.7			$	1,025.20
	Other short-term investments	1.8				1.6
	Total cash and cash equivalents	$	269.5			$	1,026.80
	Accounts receivable are presented net of a reserve for doubtful accounts of $4.8 million at December 31, 2014, and $5.3 million at December 31, 2013. During 2014, the Company recognized expense of $0.5 million to increase the reserve for doubtful accounts and wrote off $1.0 million of uncollectible accounts, which decreased the reserve. During 2013, the Company recognized expense of $1.1 million to increase the reserve for doubtful accounts and wrote off $0.8 million of uncollectible accounts, which decreased the reserve. Additionally, the reserve for doubtful accounts in 2013 decreased $0.5 million as a result of the sale of the tungsten materials business. During 2012, the Company recognized expense of $1.0 million to increase the reserve for doubtful accounts and wrote off $1.4 million of uncollectible accounts, which decreased the reserve.
	Other intangible assets, which are included in Other assets on the accompanying consolidated balance sheets as of December 31, 2014 and 2013 were as follows:
				31-Dec-14								31-Dec-13
	(in millions)	Weighted Average Useful life		Gross				Accumulated				Gross		Accumulated
		(years)		carrying				amortization				carrying		amortization
				amount								amount
	Technology	21		$	91.4			$	(14.2	)		$	74	$	(9.9	)
	Customer relationships	24		35.7				(4.7		)		31		(3.3		)
	Trademarks	15		64.6				(4.3		)		—		—
	Total amortizable intangible assets			191.7				(23.2		)		105		(13.2		)
	Indefinite-lived trademarks			—				—				61		—
	Total intangible assets			$	191.7			$	(23.2	)		$	166	$	(13.2	)
	Amortizable intangible assets increased in 2014 by $21.4 million and $4.3 million from the acquisitions of ATI Flowform Products and ATI Cast Products Salem Operations, respectively. For a $61.0 million trademark intangible asset, the Company changed the estimate of the period of future benefit from indefinite life to a 15 year useful life beginning in 2014 based on a de-emphasis of legacy business unit tradenames. Amortization expense from continuing operations related to intangible assets was approximately $10 million for the year ended December 31, 2014 and $5 million for the year ended December 31, 2013. For each of the years ending December 31, 2015 through 2019, annual amortization expense is expected to be approximately $10 million. No impairment of indefinite-lived intangible assets was determined to exist for the year ended December 31, 2013.
	Accrued liabilities included salaries, wages and other payroll-related liabilities of $77.3 million and $52.7 million at December 31, 2014 and 2013, respectively.
	Other income (expense) from continuing operations for the years ended December 31, 2014, 2013, and 2012 was as follows:
	(In millions)	2014				2013				2012
	Rent and royalty income	$	4			$	0.9			$	0.7
	Net gains (losses) on property and investments	0.1				0.7				(0.7		)
	Other	—				0.1				—
	Total other income, net	$	4.1			$	1.7			$	—

Debt

Debt	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt	Debt
	Debt at December 31, 2014 and 2013 was as follows:
	(In millions)		2014		2013
	Allegheny Technologies $500 million 5.875% Senior Notes due 2023 (a)		$	500	$	500
	Allegheny Technologies $500 million 5.95% Senior Notes due 2021		500		500
	Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014		—		402.5
	Allegheny Technologies $350 million 9.375% Senior Notes due 2019		350		350
	Allegheny Ludlum 6.95% Debentures due 2025		150		150
	Ladish Series B 6.14% Notes due 2016 (b)		11.9		18.2
	Ladish Series C 6.41% Notes due 2015 (c)		10.3		21.1
	Domestic Bank Group $400 million unsecured credit agreement		—		—
	Foreign credit agreements		—		—
	Industrial revenue bonds, due through 2020, and other		4.7		5.5
	Total short-term and long-term debt		1,526.90		1,947.30
	Short-term debt and current portion of long-term debt		17.8		419.9
	Total long-term debt		$	1,509.10	$	1,527.40
	(a)	Bearing interest at 6.125% effective August 15, 2014.
	(b)	Includes fair value adjustments of $0.4 million and $1.0 million at December 31, 2014 and December 31, 2013, respectively.
	(c)	Includes fair value adjustments of $0.3 million and $1.1 million at December 31, 2014 and December 31, 2013, respectively.
	Interest expense was $109.8 million in 2014, $66.0 million in 2013, and $72.4 million in 2012. Interest expense was reduced by $5.3 million, $45.7 million, and $24.5 million, in 2014, 2013, and 2012, respectively, from interest capitalization on capital projects. Interest and commitment fees paid were $113.2 million in 2014, $110.6 million in 2013, and $96.5 million in 2012. Net interest expense includes interest income of $1.1 million in 2014, $0.8 million in 2013, and $0.8 million in 2012.
	Scheduled principal payments during the next five years are $17.8 million in 2015, $7.7 million in 2016, $0.5 million in 2017, $0.2 million in 2018, and $350.1 million in 2019.
	2023 Notes
	On July 12, 2013, ATI issued $500 million aggregate principal amount of 5.875% Senior Notes due 2023 (the “2023 Notes”). Interest on the 2023 Notes is payable semi-annually in arrears, and the 2023 Notes will mature on August 15, 2023, unless redeemed or repurchased earlier. Underwriting fees, discount, and other third-party expenses for the issuance of the 2023 Notes were $5.2 million in 2013, and are being amortized to interest expense over the 10-year term of the 2023 Notes. The 2023 Notes are unsecured and unsubordinated obligations of the Company and equally ranked with all of its existing and future senior unsecured debt. The interest rate payable on the 2023 Notes is subject to adjustment in the event of a change in the credit ratings on the 2023 Notes. During the fourth quarter of 2014, Moody’s downgraded the Company’s credit rating one notch to Ba1 from Baa3, resulting in an increase of the interest rate on the 2023 Notes from 5.875% to 6.125% effective with the interest period beginning August 15, 2014. Future downgrades of the Company’s credit ratings could result in additional increases to the interest cost with respect to the 2023 Notes.
	Unsecured Credit Agreement
	The Company has a $400 million senior unsecured domestic revolving credit facility (“credit facility”) which expires May 31, 2018. Under the terms of the facility, the Company may increase the size of the credit facility by up to $100 million without seeking the further approval of the lending group.
	In October 2014, the Company amended the credit facility to modify the maximum leverage ratio and minimum interest coverage ratio permitted under the credit facility and to revise the calculation definitions for these two ratios. In addition, the amended credit facility provides for a springing lien on certain of the Company’s accounts receivable and inventory. This springing lien would become effective in the future if the Company’s credit ratings from both Standard & Poor’s and Moody’s are below investment grade, and would be subsequently released if the Company’s credit rating returns to investment grade from either rating agency, assuming no event of default condition existed. Third-party costs associated with this amendment were $1.2 million in 2014, and are being amortized to interest expense over the remaining term of the credit facility.
	As amended, the credit facility requires the Company to maintain a leverage ratio (measured as consolidated total indebtedness net of cash on hand in excess of $50 million, divided by consolidated EBITDA, defined as earnings before interest, taxes, depreciation and amortization, and non-cash pension expense, with the definition of consolidated EBIT excluding any gain or loss attributable to sale or other dispositions of assets outside the ordinary course of business, for the four prior fiscal quarters) of not greater than 5.75 for the quarter ended December 31, 2014, 5.00 for the quarter ended March 31, 2015, 4.50 for the quarter ended June 30, 2015, 3.75 for the quarter ended September 30, 2015, and 3.50 for the quarter ended December 31, 2015 and for each fiscal quarter thereafter. The credit facility, as amended, also requires the Company to maintain an interest coverage ratio (consolidated EBITDA as calculated for the leverage ratio, divided by interest expense) of not less than 2.0 for the quarter ended December 31, 2014, 2.50 for the quarter ended March 31, 2015, 3.00 for the quarter ended June 30, 2015, 3.25 for the quarter ended September 30, 2015, and 3.50 for the quarter ended December 31, 2015 and for each fiscal quarter thereafter. At December 31, 2014, the leverage ratio was 4.20 and the interest coverage ratio was 2.79. The Company was in compliance with these required ratios during all applicable periods. As of December 31, 2014, there were no outstanding borrowings made against the facility, although a portion of the facility was used to support approximately $4.7 million in letters of credit. The credit facility includes a $200 million sublimit for the issuance of letters of credit.
	Borrowings under the credit facility bear interest at the Company’s option at either: (1) the one-, two-, three- or six-month LIBOR rate plus a margin ranging from 1.25% to 2.50% depending upon the value of the leverage ratio as defined by the credit facility agreement; or (2) a base rate announced from time-to-time by the lending group (i.e., the Prime lending rate plus a margin ranging from 0.25% to 1.50% depending on the value of the leverage ratio). In addition, the credit facility contains a letter of credit fee of 1.25% to 2.50% and a facility fee of 0.18% to 0.35%, both depending upon the value of the leverage ratio. The Company’s overall borrowing costs under the credit facility are not affected by changes in the Company’s credit ratings.
	Convertible Notes
	In June 2009, ATI issued $402.5 million in aggregate principal amount of 4.25% Convertible Senior Notes due 2014 (the “Convertible Notes”). Interest was payable semi-annually on June 1 and December 1 of each year. The Convertible Notes were unsecured and unsubordinated obligations of the Company and ranked equally with all of its existing and future senior unsecured debt.
	On June 2, 2014, the Company repaid the remaining $397.5 million outstanding of the Convertible Notes. Holders of the Convertible Notes had the option to convert their notes into shares of ATI common stock at any time prior to the close of business on the second scheduled trading day immediately preceding the June 1, 2014 maturity date. Prior to the maturity date, $5.0 million of the Convertible Notes were converted into 120,476 shares of ATI common stock. The conversion rate for the Convertible Notes was 23.9263 shares of ATI common stock per $1,000 principal amount of Convertible Notes, equivalent to a conversion price of approximately $41.795 per share. Other than receiving cash in lieu of fractional shares, holders did not have the option to receive cash instead of shares of common stock upon conversion.
	Ladish Notes
	In conjunction with the acquisition of Ladish Co., Inc. (“Ladish”, now ATI Ladish LLC) in May 2011, the Company assumed the Series B and Series C Notes previously issued by Ladish. The Series B 6.14% Notes are unsecured and have a principal balance of $11.5 million at December 31, 2014, excluding fair value adjustments. The Series B Notes pay interest semi-annually and mature on May 16, 2016, with the principal amortizing equally in annual payments over the remaining term. The Series C 6.41% Notes are unsecured and have a principal balance of $10.0 million at December 31, 2014, excluding fair value adjustments. The Series C Notes pay interest semi-annually and mature on September 2, 2015, with the principal amortizing equally in annual payments over the remaining term. The Series B and Series C Notes contain financial covenants specific to Ladish which (1) limit the incurrence of certain additional debt; (2) require a certain level of consolidated adjusted net worth; (3) require minimum fixed charges coverage ratio; and (4) require a limited amount of funded debt to consolidated cash flow. The covenant on incurrence of additional debt limits funded debt to 60% of total capitalization. Ladish was in compliance with all Series B and Series C covenants at December 31, 2014. In March 2012, the Ladish Series B and Series C Notes were amended to replace certain reporting requirements specific to these Notes with a Parent Guaranty Agreement by ATI, by which ATI unconditionally guarantees all amounts payable by ATI Ladish LLC for the Series B and Series C Notes. As a result of the March 2012 amendment, the Series B and Series C Notes are equally ranked with all of ATI’s existing and future senior unsecured debt.
	Foreign and Other Credit Facilities
	The Company has an additional separate credit facility for the issuance of letters of credit. As of December 31, 2014, $32 million in letters of credit were outstanding under this facility.
	STAL, the Company’s Chinese joint venture company in which ATI has a 60% interest, had a 205 million renminbi revolving credit facility with a group of banks that expired in August 2014. Replacement of the credit facility is expected to be finalized in the first quarter of 2015.
	The Company has no off-balance sheet financing relationships as defined in Item 303(a)(4) of SEC Regulation S-K, with variable interest entities, structured finance entities, or any other unconsolidated entities. At December 31, 2014, the Company had not guaranteed any third-party indebtedness.

Derivative_Financial_Instrumen

Derivative Financial Instruments and Hedging	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments and Hedging	Derivative Financial Instruments and Hedging
	As part of its risk management strategy, the Company, from time-to-time, utilizes derivative financial instruments to manage its exposure to changes in raw material prices, energy costs, foreign currencies, and interest rates. In accordance with applicable accounting standards, the Company accounts for most of these contracts as hedges. In general, hedge effectiveness is determined by examining the relationship between offsetting changes in fair value or cash flows attributable to the item being hedged, and the financial instrument being used for the hedge. Effectiveness is measured utilizing regression analysis and other techniques to determine whether the change in the fair market value or cash flows of the derivative exceeds the change in fair value or cash flow of the hedged item. Calculated ineffectiveness, if any, is immediately recognized on the statement of operations.
	The Company sometimes uses futures and swap contracts to manage exposure to changes in prices for forecasted purchases of raw materials, such as nickel, and energy costs, such as electricity and natural gas. Generally under these contracts, which are accounted for as cash flow hedges, the price of the item being hedged is fixed at the time that the contract is entered into and the Company is obligated to make or receive a payment equal to the net change between this fixed price and the market price at the date the contract matures.
	The majority of ATI’s products are sold utilizing raw material surcharges and index mechanisms. However, as of December 31, 2014, the Company had entered into financial hedging arrangements primarily at the request of its customers, related to firm orders, for an aggregate notional amount of approximately 15% of the Company’s estimated annual nickel requirements. These nickel hedges extend to 2020.
	At December 31, 2014, the outstanding financial derivatives used to hedge the Company’s exposure to energy cost volatility included natural gas cost hedges for approximately 80% of its annual forecasted domestic requirements for 2015, 70% for 2016, and approximately 40% for 2017. There were no material electricity hedge contracts outstanding as of December 31, 2014.
	While the majority of the Company’s direct export sales are transacted in U.S. dollars, foreign currency exchange contracts are used, from time-to-time, to limit transactional exposure to changes in currency exchange rates for those transactions denominated in a non-U.S. currency. The Company sometimes purchases foreign currency forward contracts that permit it to sell specified amounts of foreign currencies expected to be received from its export sales for pre-established U.S. dollar amounts at specified dates. The forward contracts are denominated in the same foreign currencies in which export sales are denominated. These contracts are designated as hedges of the variability in cash flows of a portion of the forecasted future export sales transactions which otherwise would expose the Company to foreign currency risk, primarily euros. At December 31, 2014, the Company held euro forward sales contracts designated as hedges with a notional value of approximately 388 million euros with maturity dates through June 2018, including approximately 175 million euros with maturities in 2015. In addition, the Company may also designate cash balances held in foreign currencies as hedges of forecasted foreign currency transactions.
	The Company may enter into derivative interest rate contracts to maintain a reasonable balance between fixed- and floating-rate debt. There were no unsettled derivative financial instruments related to debt balances for the periods presented.
	There are no credit risk-related contingent features in the Company’s derivative contracts, and the contracts contained no provisions under which the Company has posted, or would be required to post, collateral. The counterparties to the Company’s derivative contracts were substantial and creditworthy commercial banks that are recognized market makers. The Company controls its credit exposure by diversifying across multiple counterparties and by monitoring credit ratings and credit default swap spreads of its counterparties. The Company also enters into master netting agreements with counterparties when possible.
	The fair values of the Company’s derivative financial instruments are presented below, representing the gross amounts recognized which are not offset by counterpart or by type of item hedged. All fair values for these derivatives were measured using Level 2 information as defined by the accounting standard hierarchy, which includes quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs derived principally from or corroborated by observable market data.
	(In millions)				December 31,				December 31,
	Asset derivatives		Balance sheet location		2014				2013
	Derivatives designated as hedging instruments:
	Foreign exchange contracts		Prepaid expenses and other current assets		$	23.6			$	0.3
	Nickel and other raw material contracts		Prepaid expenses and other current assets		1.1				0.1
	Natural gas contracts		Prepaid expenses and other current assets		—				2.5
	Foreign exchange contracts		Other assets		28.3				—
	Natural gas contracts		Other assets		—				1
	Nickel and other raw material contracts		Other assets		0.5				0.4
	Total derivatives designated as hedging instruments:				53.5				4.3
	Derivatives not designated as hedging instruments:
	Foreign exchange contracts		Prepaid expenses and other current assets		6.4				—
	Total derivatives not designated as hedging instruments:				6.4				—
	Total asset derivatives				$	59.9			$	4.3
	Liability derivatives		Balance sheet location
	Derivatives designated as hedging instruments:
	Natural gas contracts		Accrued liabilities		$	10.2			$	0.4
	Foreign exchange contracts		Accrued liabilities		—				7.8
	Nickel and other raw material contracts		Accrued liabilities		5.8				4.5
	Electricity contracts		Accrued liabilities		0.1				0.5
	Foreign exchange contracts		Other long-term liabilities		—				5.4
	Natural gas contracts		Other long-term liabilities		7.9				—
	Nickel and other raw material contracts		Other long-term liabilities		3				1.3
	Total liability derivatives				$	27			$	19.9
	Derivatives not designated as hedging instruments:
	Foreign exchange contracts		Accrued liabilities		—				1.7
	Total derivatives not designated as hedging instruments:				—				1.7
	Total liability derivatives				$	27			$	21.6
	For derivative financial instruments that are designated as cash flow hedges, the effective portion of the gain or loss on the derivative is reported as a component of other comprehensive income (OCI) and reclassified into earnings in the same period or periods during which the hedged item affects earnings. Gains and losses on the derivative representing either hedge ineffectiveness or hedge components excluded from the assessment of effectiveness are recognized in current period results. The Company did not use fair value or net investment hedges for the periods presented. The effects of derivative instruments in the tables below are presented net of related income taxes.
	Activity with regard to derivatives designated as cash flow hedges for the year ended December 31, 2014 were as follows (in millions):
	Derivatives in Cash Flow		Amount of Gain (Loss)								Amount of Gain (Loss)						Amount of Gain (Loss)
	Hedging Relationships		Recognized in OCI on								Reclassified from						Recognized in Income
			Derivatives								Accumulated OCI						on Derivatives  (Ineffective
			(Effective Portion)								into Income						Portion and Amount
											(Effective Portion) (a)						Excluded from
																	Effectiveness Testing) (b)
			2014				2013				2014			2013			2014		2013
	Nickel and other raw material contracts		$	(1.6	)		$	(8.4	)		$	(0.6	)	$	(5.4	)	$	—	$	—
	Natural gas contracts		(10.9		)		2.1				2.1			(2.3		)	—		—
	Electricity contracts		0.5				(0.1		)		0.4			(0.2		)	—		—
	Foreign exchange contracts		40.1				(9.1		)		0.3			(0.7		)	—		—
	Total		$	28.1			$	(15.5	)		$	2.2		$	(8.6	)	$	—	$	—
	(a)	The gains (losses) reclassified from accumulated OCI into income related to the effective portion of the derivatives are presented in cost of sales.
	(b)	The gains (losses) recognized in income on derivatives related to the ineffective portion and the amount excluded from effectiveness testing are presented in selling and administrative expenses.
	Assuming market prices remain constant with those at December 31, 2014, a gain of $5.3 million, net of tax, is expected to be recognized over the next 12 months.
	The disclosures of gains or losses presented above for nickel and other raw material contracts and foreign exchange contracts do not take into account the anticipated underlying transactions. Since these derivative contracts represent hedges, the net effect of any gain or loss on results of operations may be fully or partially offset.
	Derivatives that are not designated as hedging instruments were as follows:
	(In millions)		Amount of Gain (Loss) Recognized
			in Income on Derivatives
	Derivatives Not Designated as Hedging Instruments		2014				2013
	Foreign exchange contracts		$	5.2			$	(0.3	)
	Changes in the fair value of foreign exchange contract derivatives not designated as hedging instruments are recorded in cost of sales.

Fair_Value_Of_Financial_Instru

Fair Value Of Financial Instruments	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Of Financial Instruments	Fair Value of Financial Instruments
	The estimated fair value of financial instruments at December 31, 2014 was as follows:
				Fair Value Measurements at Reporting Date Using
	(In millions)	Total		Total		Quoted Prices in		Significant
		Carrying		Estimated		Active Markets for		Observable
		Amount		Fair Value		Identical Assets		Inputs
						(Level 1)		(Level 2)
	Cash and cash equivalents	$	269.5	$	269.5	$	269.5	$	—
	Derivative financial instruments:
	Assets	59.9		59.9		—		59.9
	Liabilities	27		27		—		27
	Debt	1,526.90		1,616.00		1,589.10		26.9
	The estimated fair value of financial instruments at December 31, 2013 was as follows:
				Fair Value Measurements at Reporting Date Using
	(In millions)	Total		Total		Quoted Prices in		Significant
		Carrying		Estimated		Active Markets for		Observable
		Amount		Fair Value		Identical Assets		Inputs
						(Level 1)		(Level 2)
	Cash and cash equivalents	$	1,026.80	$	1,026.80	$	1,026.80	$	—
	Derivative financial instruments:
	Assets	4.3		4.3		—		4.3
	Liabilities	21.6		21.6		—		21.6
	Debt	1,947.30		2,072.60		2,027.80		44.8
	In accordance with accounting standards, fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Accounting standards established three levels of a fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy requires entities to maximize the use of observable inputs and minimize the use of unobservable inputs. 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 other 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 that are significant to the fair value of the assets and liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.
	The availability of observable market data is monitored to assess the appropriate classification of financial instruments within the fair value hierarchy. Changes in economic conditions or model-based valuation techniques may require the transfer of financial instruments from one fair value level to another. In such instances, the transfer is reported at the beginning of the reporting period. No transfers between levels were reported in 2014 or 2013.
	The following methods and assumptions were used by the Company in estimating the fair value of its financial instruments:
	Cash and cash equivalents: Fair values were determined using Level 1 information.
	Derivative financial instruments: Fair values for derivatives were measured using exchange-traded prices for the hedged items. The fair value was determined using Level 2 information, including consideration of counterparty risk and the Company’s credit risk.
	Short-term and long-term debt: The fair values of the Allegheny Technologies 4.25% Convertible Senior Notes due 2014 (for 2013 fair value), the Allegheny Technologies 9.375% Senior Notes due 2019, the Allegheny Technologies 5.95% Senior Notes due 2021, the Allegheny Technologies 5.875% Senior Notes due 2023 and the Allegheny Ludlum 6.95% Debentures due 2025 were determined using Level 1 information. The fair values of the other short-term and long-term debt were determined using Level 2 information.

Pension_Plans_and_Other_Postre

Pension Plans and Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Pension Plans and Other Postretirement Benefits	Pension Plans and Other Postretirement Benefits
	The Company has defined benefit pension plans or defined contribution retirement plans covering substantially all employees. Benefits under the defined benefit pension plans are generally based on years of service and/or final average pay. The Company funds the U.S. pension plans in accordance with the Employee Retirement Income Security Act of 1974, as amended, and the Internal Revenue Code (“Code”).
	The Company also sponsors several postretirement plans covering certain salaried and hourly employees. The plans provide health care and life insurance benefits for eligible retirees. In most retiree health care plans, Company contributions towards premiums are capped based on the cost as of a certain date, thereby creating a defined contribution. For the non-collectively bargained plans, the Company maintains the right to amend or terminate the plans at its discretion.
	In December 2014, the Company announced several significant changes to its retirement benefit programs. These changes are part of the Company’s ongoing initiatives to create an integrated and aligned business with a market competitive, cost competitive, and consistent health, welfare and retirement benefit structure across its operations. These changes included:
	•	Freezing all future benefit accruals to its U.S. qualified defined benefit pension plan (U.S. Plan), and to the Company’s non-qualified defined benefit pension plans, including the executive Supplemental Pension Plan, effective December 31, 2014.
	•	Implementing a consistent defined contribution retirement plan with a base 6.5% company contribution and up to 3% in Company matching contributions across all U.S. operations effective January 1, 2015.
	•	Ending Company-provided salaried retiree life insurance benefits effective January 1, 2015.
	•	Ending all remaining Company-provided salaried retiree medical benefits on January 1, 2016. The salaried retiree medical benefit plan being ended was assumed as part of the 2011 Ladish acquisition. Certain participants in the retiree medical plan will have transition provisions through the end of 2016.
	•	These changes to pension, retiree life insurance and medical benefits do not affect benefits for those employees or retirees covered by collective bargaining contracts or other contractual employment agreements.
	The components of pension and other postretirement benefit expense for the Company’s defined benefit plans included the following:
			Pension Benefits											Other Postretirement Benefits
	(In millions)		2014				2013				2012			2014				2013			2012
	Service cost—benefits earned during the year		$	29.4			$	39			$	35		$	2.9			$	3.2		$	3.1
	Interest cost on benefits earned in prior years		133.6				122.8				132.4			24				22.4			26.1
	Expected return on plan assets		(184.2		)		(176.0		)		(181.4		)	(0.3		)		(0.5		)	(0.8		)
	Amortization of prior service cost (credit)		2.3				3				6.4			(3.0		)		(18.2		)	(18.2		)
	Amortization of net actuarial loss		74				111.8				105.2			14.1				17.2			14.6
	Curtailment (gain) loss		0.5				—				—			(25.5		)		—			—
	Termination benefits		0.3				4.8				—			—				1.3			—
	Total retirement benefit expense		$	55.9			$	105.4			$	97.6		$	12.2			$	25.4		$	24.8
	Other postretirement benefit costs for a defined contribution plan were $2.6 million and $4.6 million for the fiscal years ended December 31, 2014 and 2013, respectively. The curtailment loss for pension benefits recorded in 2014 relates to unamortized prior service cost recognized as a result of the freezing of pension benefit accruals in the fourth quarter of 2014, as discussed above. The curtailment gain for other postretirement benefits recorded in 2014 relates to the changes to salaried retiree life insurance and medical benefits in the fourth quarter of 2014 as discussed above. Special termination benefits recorded in 2014 relate to the acceptance of an early retirement benefit in the Forged Products business. Special termination benefits recorded in 2013 relate largely to the closure of the Flat Rolled Product segment’s Wallingford, CT finishing facility, and these costs were reported in restructuring costs for segment reporting (see Notes 15 and 16).
	Actuarial assumptions used to develop the components of defined benefit pension expense and other postretirement benefit expense were as follows:
			Pension Benefits									Other Postretirement Benefits
			2014			2013			2012			2014		2013			2012
	Discount rate (a)		5.15	%		4.25 - 4.95%			5	%		5.15	%	4.25	%		5	%
	Rate of increase in future compensation levels		3.0 - 3.50%			3.0 - 3.50%			3.0 - 4.50%			—		—			—
	Expected long-term rate of return on assets		8.25	%		8.25	%		8.5	%		8.3	%	8.3	%		8.3	%
	(a)	Pension expense for 2013 was initially measured at a 4.25% discount rate. The U.S. Plan was remeasured using a 4.95% discount rate as of October 31, 2013, following the sale of the tungsten materials business.
	Actuarial assumptions used for the valuation of defined benefit pension and other postretirement benefit obligations at the end of the respective periods were as follows:
			Pension Benefits						Other Postretirement Benefits
			2014			2013			2014			2013
	Discount rate		4.25	%		5.15	%		4.1	%		5.15	%
	Rate of increase in future compensation levels		3.0 - 3.5%			3.0 - 3.5%			—			—
	A reconciliation of the funded status for the Company’s defined benefit pension and other postretirement benefit plans at December 31, 2014 and 2013 was as follows:
			Pension Benefits								Other Postretirement Benefits
	(In millions)		2014				2013				2014			2013
	Change in benefit obligations:
	Benefit obligation at beginning of year		$	2,698.20			$	2,952.00			$	506.7		$	574.3
	Service cost		29.4				39				2.9			3.2
	Interest cost		133.6				122.8				24			22.4
	Benefits paid		(269.9		)		(195.6		)		(54.3		)	(52.9		)
	Subsidy paid		—				—				1			1.2
	Participant contributions		0.3				0.1				—			—
	Effect of currency rates		(4.9		)		0.8				—			—
	Net actuarial (gains) losses – discount rate change		288.5				(280.4		)		39.5			(36.9		)
	– other		78.4				54.7				(19.5		)	(5.9		)
	Plan curtailments		—				—				(7.2		)	—
	Plan settlements		—				—				(27.0		)	—
	Special termination benefits		0.3				4.8				—			1.3
	Benefit obligation at end of year		$	2,953.90			$	2,698.20			$	466.1		$	506.7
	Pension benefit payments in 2014 include approximately $52 million associated with a one-time, voluntary lump sum cash out offer to terminated vested participants in the U.S. Plan. Changes in the pension benefit obligation for 2014 include the effects of updated estimates of participant life expectancy, including consideration of the impacts of the updated 2014 U.S. Society of Actuaries projections and Company-specific experience. These mortality assumption changes increased the pension benefit obligation at December 31, 2014 by approximately $90 million.
	Change in plan assets:
	Fair value of plan assets at beginning of year		$	2,329.80			$	2,220.00			$	4		$	6.3
	Actual returns on plan assets and plan expenses		136.8				293.8				(0.9		)	(0.9		)
	Employer contributions		11.5				10.7				—			—
	Participant contributions		0.3				0.1				—			—
	Effect of currency rates		(4.1		)		0.8				—			—
	Benefits paid		(269.9		)		(195.6		)		(0.2		)	(1.4		)
	Fair value of plan assets at end of year		$	2,204.40			$	2,329.80			$	2.9		$	4
	Amounts recognized in the consolidated balance sheet:
	Noncurrent assets		$	—			$	5.1			$	—		$	—
	Current liabilities		(10.2		)		(5.3		)		(47.3		)	(60.3		)
	Noncurrent liabilities		(739.3		)		(368.2		)		(415.8		)	(442.4		)
	Total amount recognized		$	(749.5	)		$	(368.4	)		$	(463.1	)	$	(502.7	)
Changes to accumulated other comprehensive loss related to pension and other postretirement benefit plans in 2014 and 2013 were as follows:
		Pension Benefits								Other Postretirement Benefits
(In millions)		2014				2013				2014			2013
Beginning of year accumulated other comprehensive loss		$	(1,016.4	)		$	(1,474.7	)		$	(151.5	)	$	(191.9	)
Amortization of net actuarial loss		74				111.8				14.1			17.2
Amortization of prior service cost (credit)		2.3				3				(3.0		)	(18.2		)
Remeasurements		(412.0		)		343.5				(12.5		)	41.4
End of year accumulated other comprehensive loss		$	(1,352.1	)		$	(1,016.4	)		$	(152.9	)	$	(151.5	)
Net change in accumulated other comprehensive loss		$	(335.7	)		$	458.3			$	(1.4	)	$	40.4
Amounts included in accumulated other comprehensive loss at December 31, 2014 and 2013 were as follows:
		Pension Benefits								Other Postretirement Benefits
(In millions)		2014				2013				2014			2013
Prior service (cost) credit		$	(4.9	)		$	(7.7	)		$	(11.8	)	$	(8.7	)
Net actuarial loss		(1,347.2		)		(1,008.7		)		(141.1		)	(142.8		)
Accumulated other comprehensive loss		(1,352.1		)		(1,016.4		)		(152.9		)	(151.5		)
Deferred tax effect		514.7				390.7				58.8			58.3
Accumulated other comprehensive loss, net of tax		$	(837.4	)		$	(625.7	)		$	(94.1	)	$	(93.2	)
Retirement benefit expense for 2015 for defined benefit plans is estimated to be approximately $77 million, comprised of $37 million for pension expense and $40 million of expense for other postretirement benefits. As a result of the pension freeze effective December 31, 2014 and the resultant determination of inactive status, beginning in 2015, the U.S. Plan and the non-qualified U.S. pension plans will change the amortization period for accumulated other comprehensive loss recognition to the average remaining life expectancy, which is approximately 18 years on a weighted average basis, rather than the average remaining service period of 10 years, which was used in 2014 and prior periods.
Amounts in accumulated other comprehensive loss that are expected to be recognized as components of net periodic benefit cost in 2015 are:
(In millions)		Pension				Other				Total
		Benefits				Postretirement
						Benefits
Amortization of prior service cost		$	1.3			$	4.9			$	6.2
Amortization of net actuarial loss		60.5				14.7				75.2
Amortization of accumulated other comprehensive loss		$	61.8			$	19.6			$	81.4
The accumulated benefit obligation for all defined benefit pension plans was $2,917.3 million and $2,621.8 million at December 31, 2014 and 2013, respectively. Additional information for pension plans with accumulated benefit obligations in excess of plan assets:
		Pension Benefits
(In millions)		2014				2013
Projected benefit obligation		$	2,953.90			$	2,619.60
Accumulated benefit obligation		$	2,917.30			$	2,545.40
Fair value of plan assets		$	2,204.40			$	2,246.10
Based upon current regulations and actuarial studies, the Company does not expect to be required to make cash contributions to its U.S. Plan for 2015. However, the Company may elect, depending upon the investment performance of the pension plan assets and other factors, to make voluntary cash contributions to this pension plan in the future. For 2015, the Company expects to fund benefits of approximately $10 million for its U.S. nonqualified benefit pension plans and its U.K. defined benefit plan.
The following table summarizes expected benefit payments from the Company’s various pension and other postretirement benefit defined benefit plans through 2024, and also includes estimated Medicare Part D subsidies projected to be received during this period based on currently available information.
(In millions)		Pension				Other				Medicare Part
		Benefits				Postretirement				D Subsidy
						Benefits
2015		$	195.4			$	51.3			$	1.1
2016		195.4				44.7				1.1
2017		195.1				42.6				1.1
2018		195.4				40.4				1.1
2019		195.1				38.3				1.1
2020 - 2024		967.7				154.7				4.7
The annual assumed rate of increase in the per capita cost of covered benefits (the health care cost trend rate) for health care plans was 8.0% in 2015 and is assumed to gradually decrease to 5.0% in the year 2028 and remain at that level thereafter. Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one percentage point change in assumed health care cost trend rates would have the following effects:
(In millions)		One				One
		Percentage				Percentage
		Point				Point
		Increase				Decrease
Effect on total of service and interest cost components for the year ended December 31, 2014		$	0.5			$	(0.5	)
Effect on other postretirement benefit obligation at December 31, 2014		$	11.1			$	(9.7	)
The plan assets for the U.S. Plan represent approximately 96% of total pension plan assets at December 31, 2014. The U.S. Plan invests in a diversified portfolio consisting of an array of asset classes that attempts to maximize returns while minimizing volatility. These asset classes include U.S. domestic equities, developed market equities, emerging market equities, private equity, global high quality and high yield fixed income, floating rate debt and real estate. The Company continually monitors the investment results of these asset classes and its fund managers, and explores other potential asset classes for possible future investment.
U.S. Plan assets at December 31, 2014 and 2013 included 3.0 million shares of ATI common stock with a fair value of $102.7 million and $105.3 million, respectively. Dividends of $2.1 million were received by the U.S. Plan in both 2014 and 2013 on the ATI common stock held by this plan.
The fair values of the Company’s pension plan assets at December 31, 2014 by asset category and by the level of inputs used to determine fair value, were as follows:
(In millions)						Quoted Prices in				Significant			Significant
						Active Markets for				Observable Inputs			Unobservable Inputs
						Identical Assets
Asset category		Total				(Level 1)				(Level 2)			(Level 3)
Equity securities:
ATI common stock		$	102.7			$	102.7			$	—		$	—
Other U.S. equities (a)		673.8				306.1				367.7			—
International equities (b)		238.2				—				238.2			—
Global debt securities and cash: (c)
Fixed income and cash equivalents		383.5				0.7				373.9			8.9
Floating rate		392.3				—				—			392.3
Private equity		134.7				—				—			134.7
Hedge funds		122.6				—				—			122.6
Real estate and other		156.6				—				5.4			151.2
Total assets		$	2,204.40			$	409.5			$	985.2		$	809.7
(a)	Includes investments in commingled funds that invest in U.S. equity securities, comprised of approximately 90% large-cap U.S. companies and 10% small-cap U.S. companies.
(b)	Includes investments in commingled funds that invest in non-U.S. equity securities, comprised of approximately 90% developed countries and 10% emerging market economies.
(c)	Global debt securities include both fixed interest rate and floating interest rate instruments. These are comprised of actively managed investments which include U.S. government and U.S. government agency securities, foreign government securities, corporate bonds, mortgage-backed securities and other debt securities, and include both investment grade and non-investment grade debt, public and private debt, and secured and unsecured debt investments. To mitigate risk, investment managers have limitations regarding the amount of investment in particular securities and the credit quality of such investments.
The fair values of the Company’s pension plan assets at December 31, 2013 by asset category and by the level of inputs used to determine fair value, were as follows:
(In millions)						Quoted Prices in				Significant			Significant
						Active Markets for				Observable Inputs			Unobservable Inputs
						Identical Assets
Asset category		Total				(Level 1)				(Level 2)			(Level 3)
Equity securities:
ATI common stock		$	105.3			$	105.3			$	—		$	—
Other U.S. equities (a)		746				257.2				488.8			—
International equities (b)		311				—				311			—
Global securities and cash: (c)
Fixed income and cash equivalents		508				—				507.2			0.8
Floating rate		294.5				—				—			294.5
Private equity		94.5				—				—			94.5
Hedge funds		139.7				—				—			139.7
Real estate and other		130.8				—				5			125.8
Total assets		$	2,329.80			$	362.5			$	1,312.00		$	655.3
(a)	Includes investments in commingled funds that invest in U.S. equity securities, comprised of approximately 90% large-cap U.S. companies and 10% small-cap U.S. companies.
(b)	Includes investments in commingled funds that invest in non-U.S. equity securities, comprised of approximately 80% developed countries and 20% emerging market economies.
(c)	Global debt securities include both fixed interest rate and floating interest rate instruments. These are comprised of actively managed investments which include U.S. government and U.S. government agency securities, foreign government securities, corporate bonds, mortgage-backed securities and other debt securities, and include both investment grade and non-investment grade debt, public and private debt, and secured and unsecured debt investments. To mitigate risk, investment managers have limitations regarding the amount of investment in particular securities and the credit quality of such investments.
Transfers from Level 1 to Level 2 of the fair value hierarchy were approximately $203 million in 2013 based on the Company’s reassessment of fair value input measures and observable market data used to value certain investments, due to a changing mix of securities and the increased use of derivative financial instruments.
Changes in the fair value of Level 3 pension plan assets for the year ended December 31, 2014 were as follows:
(In millions)		January 1,				Net Realized				Net Purchases,			Net Transfers				December 31,
		2014 Balance				and Unrealized				Issuances and			Into (Out Of)				2014 Balance
						Gains (Losses)				Settlements			Level 3
Global debt securities and cash:
Fixed income and cash equivalents		$	0.8			$	0.1			$	8		$	—			$	8.9
Floating rate debt		294.5				4.6				93.2			—				392.3
Private equity		94.5				19.1				21.1			—				134.7
Hedge funds		139.7				5.9				(23.0		)	—				122.6
Real estate and other		125.8				13.7				11.7			—				151.2
Total		$	655.3			$	43.4			$	111		$	—			$	809.7
Changes in the fair value of Level 3 pension plan assets for the year ended December 31, 2013 were as follows:
(In millions)		January 1,				Net Realized				Net Purchases,			Net Transfers				December 31,
		2013 Balance				and Unrealized				Issuances and			Into (Out Of)				2013 Balance
						Gains (Losses)				Settlements			Level 3
Global debt securities and cash:
Fixed income and cash equivalents		$	1.4			$	0.1			$	(0.7	)	$	—			$	0.8
Floating rate debt		—				5.4				289.1			—				294.5
Private equity		85.5				3.9				5.1			—				94.5
Hedge funds		148.9				13.8				(23.0		)	—				139.7
Real estate and other		104.4				16.4				5			—				125.8
Total		$	340.2			$	39.6			$	275.5		$	—			$	655.3
A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Investments in U.S. and International equities, and Fixed Income are predominantly held in common/collective trust funds and registered investment companies. These investments are public investment vehicles valued using the net asset value (NAV) provided by the administrator of the fund. The NAV is based on the value of the underlying assets owned by the fund, minus its liabilities, and then divided by the number of shares outstanding. In certain cases NAV is a quoted price in a market that is not active, and valuation is based on quoted prices for similar assets and liabilities in active markets, and these investments are classified within Level 2 of the valuation hierarchy. Investments that are not actively traded, such as non-publicly traded real estate funds, are classified within Level 3 of the valuation hierarchy, as the NAV is based on significant unobservable information.
Hedge fund investments are made either (1) as a limited partner in a portfolio of underlying hedge funds managed by a general partner or (2) through commingled institutional funds (CIFs) that in-turn invest in various portfolios of hedge funds whereby the allocation of the Plan’s investments to each CIF is managed by a third party Investment Manager. All hedge fund investments are classified within Level 3 of the valuation hierarchy, as the valuations are substantially based on unobservable information.
Private equity investments include both Direct Funds and Fund-of-Funds. All private equity investments are classified as Level 3 in the valuation hierarchy, as the valuations are substantially based upon unobservable information. Direct Funds are investments in Limited Partnership (LP) interests. Fund-of-Funds are investments in private equity funds that invest in other private equity funds or LPs.
Real estate investments are made in either (1) as a limited partner in a portfolio of properties managed by a general partner or (2) through a CIF that invests in a portfolio of real estate funds.
For certain investments classified as Level 3 which have formal financial valuations reported on a one-quarter lag, fair value is determined utilizing net asset values adjusted for subsequent cash flows, estimated financial performance and other significant events.
For 2015, the expected long-term rate of returns on defined benefit pension assets will be 8.0%. In developing the expected long-term rate of return assumptions, the Company evaluated input from its third party pension plan asset managers and actuaries, including reviews of their asset class return expectations and long-term inflation assumptions. The expected long-term rate of return is based on expected asset allocations within ranges for each investment category, and includes consideration of both historical and projected annual compound returns, weighted on a 65%/35% basis, respectively. The Company’s actual returns on pension assets for the last five years have been 6.5% for 2014, 14.3% for 2013, 8.0% for 2012, 0.3% for 2011, and 12.2% for 2010.
The target asset allocations for pension plans for 2015, by major investment category, are:
Asset category		Target asset allocation range
Equity securities:
U. S. equities		18% - 40%
International equities		7% - 17%
Global debt securities and cash		35% - 48%
Private equity*		0% - 10%
Hedge funds*		0% - 10%
Real estate and other*		0% - 10%
* Have a combined target allocation of 18% and a 20% limit.
At December 31, 2014, other postretirement benefit plan assets of $2.9 million are primarily invested in private equity investments, which are classified as Level 3 in the valuation hierarchy, as the valuations are substantially based upon unobservable information. For 2015, the expected long-term rate of returns on these other postretirement benefit assets will be 4.0%.
Costs for defined contribution plans were $21.9 million in 2014, $24.3 million in 2013, and $23.8 million in 2012. Company contributions to these defined contribution plans are funded with cash.
Labor agreements with USW-represented employees require the Company to make contributions to VEBA trusts based upon the attainment of a certain level of profitability. The Company expects to make approximately $16 million of contributions, tied to profitability levels, to these VEBA trusts in 2015.
The Company contributes to several multiemployer defined benefit pension plans under collective bargaining agreements that cover certain of its union-represented employees. The risks of participating in such plans are different from the risks of single-employer plans, in the following respects:
a.	Assets contributed to a multiemployer plan by one employer may be used to provide benefits to employees of other participating employers.
b.	If a participating employer ceases to contribute to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers.
c.	If the Company ceases to have an obligation to contribute to the multiemployer plan in which it had been a contributing employer, it may be required to pay to the plan an amount based on the underfunded status of the plan and on the history of the Company’s participation in the plan prior to the cessation of its obligation to contribute. The amount that an employer that has ceased to have an obligation to contribute to a multiemployer plan is required to pay to the plan is referred to as a withdrawal liability.
The Company’s participation in multiemployer plans for the years ended December 31, 2014, 2013 and 2012 is reported in the following table. The Company’s contributions to the Steelworkers Western Independent Shops Pension Plan exceed 5% of this plan’s total contributions for the plan year ended September 30, 2013, which is the most recent information available from the Plan Administrator.
				Pension				FIP / RP Status		in millions												Expiration Dates
				Protection Act				Pending /														of Collective
		EIN / Pension		Zone Status (1)				Implemented (2)		Company Contributions										Surcharge		Bargaining
Pension Fund		Plan Number		2014		2013				2014			2013				2012			Imposed (3)		Agreements
Steelworkers Western Independent Shops Pension Plan		90-0169564		Green		Red		N/A		$	1.1		$	1			$	1.3		No		6/30/15
		/ 001
Boilermakers-Blacksmiths National Pension Trust		48-6168020		Yellow		Yellow		Yes		2			2.2				2.4			No		9/30/18
		/ 001
IAM National Pension Fund		51-6031295		Green		Green		N/A		1.6			1.8				1.9			No		Various between 2018-2019 (4)
		/ 002
Total contributions										$	4.7		$	5			$	5.6
-1	The most recent Pension Protection Act Zone Status available for ATI’s fiscal years 2014 and 2013 is for plan years ending in calendar years 2013 and 2012, respectively. The zone status is based on information provided to ATI and other participating employers by each plan and is certified by the plan’s actuary. A plan in the “red” zone had been determined to be in “critical status”, based on criteria established by the Code, and is generally less than 65% funded. A plan in the “yellow” zone has been determined to be in “endangered status”, based on criteria established under the Code, and is generally less than 80% funded. A plan in the “green” zone has been determined to be neither in “critical status” nor in “endangered status”, and is generally at least 80% funded.
-2	The “FIP / RP status Pending / Implemented” column indicates whether a Funding Improvement Plan, as required under the Code by plans in the “yellow” zone, or a Rehabilitation Plan, as required under the Code to be adopted by plans in the “red” zone, is pending or has been implemented as of the end of the plan year that ended in 2014.
-3	The “Surcharge Imposed” column indicates whether ATI’s contribution rate for 2014 included an amount in addition to the contribution rate specified in the applicable collective bargaining agreement, as imposed by a plan in “critical status”, in accordance with the requirements of the Code.
-4	The Company is party to five separate bargaining agreements that require contributions to this plan. Expiration dates of these collective bargaining agreements range between February 25, 2018 and July 14, 2019.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)
	The changes in accumulated other comprehensive income (loss) (AOCI) by component, net of tax, for the fiscal years ended December 31, 2014 and 2013 were as follows (in millions):
		Post-				Currency				Unrealized			Derivatives			Total
		retirement				translation				holding gains
		benefit plans				adjustment				on securities
	Attributable to ATI:
	Balance, December 31, 2012	$	(1,030.0	)		$	3.4			$	(0.1	)	$	(2.7	)	$	(1,029.4	)
	OCI before reclassifications		241.1				10.4				0.1			(15.5	)	236.1
	Amounts reclassified from AOCI	(a)	70			(b)	1.5			(c)	—		(d)	8.6		80.1
	Net current-period OCI		311.1				11.9				0.1			(6.9	)	316.2
	Balance, December 31, 2013		(718.9	)			15.3				—			(9.6	)	(713.2		)
	OCI before reclassifications		(266.4	)			(32.0	)			—			28.1		$	(270.3	)
	Amounts reclassified from AOCI	(a)	53.8				0.5			(c)	—		(d)	(2.2	)	52.1
	Net current-period OCI		(212.6	)			(31.5	)			—			25.9		(218.2		)
	Balance, December 31, 2014	$	(931.5	)		$	(16.2	)		$	—		$	16.3		$	(931.4	)
	Attributable to noncontrolling interests:
	Balance, December 31, 2012	$	—			$	23.7			$	—		$	—		$	23.7
	OCI before reclassifications		—				3.4				—			—		3.4
	Amounts reclassified from AOCI		—			(c)	—				—			—		—
	Net current-period OCI		—				3.4				—			—		3.4
	Balance, December 31, 2013		—				27.1				—			—		27.1
	OCI before reclassifications		—				(2.1	)			—			—		(2.1		)
	Amounts reclassified from AOCI		—			(c)	—				—			—		—
	Net current-period OCI		—				(2.1	)			—			—		(2.1		)
	Balance, December 31, 2014	$	—			$	25			$	—		$	—		$	25
	(a)	Amounts were included in net periodic benefit cost for pension and other postretirement benefit plans (see Note 11).
	(b)	Amount was included in discontinued operations as part of the gain on sale of the tungsten materials business (see Note 3).
	(c)	No amounts were reclassified to earnings.
	(d)	Amounts were included in cost of goods sold in the period or periods the hedged item affects earnings (see Note 9).
	Other comprehensive income (loss) amounts are net of applicable income tax expense (benefit) for each year presented. Foreign currency translation adjustments, including those pertaining to noncontrolling interests, are generally not adjusted for income taxes as they relate to indefinite investments in non-U.S. subsidiaries.
	Reclassifications out of AOCI for the fiscal years ended December 31, 2014 and 2013 were as follows:
			Amount reclassified from AOCI (d)
			Fiscal year ended
	Details about AOCI Components		31-Dec-14						31-Dec-13				Affected line item in the
	(In millions)												consolidated statement of operations
	Postretirement benefit plans
	Prior service credit		$	0.7			(a)		$	15.2		(a)
	Actuarial losses		(88.1		)		(a)		(129.0		)	(a)
			(87.4		)		(d)		(113.8		)	(d)	Total before tax
			(33.6		)				(43.8		)		Tax provision (benefit)
			$	(53.8	)				$	(70.0	)		Net of tax
	Currency translation adjustment		$	(0.5	)		(b) , (d)		$	(1.5	)	(b) , (d)
	Derivatives
	Nickel and other raw material contracts		$	(1.0	)		(c)		$	(8.8	)	(c)
	Natural gas contracts		3.4				(c)		(3.8		)	(c)
	Electricity contracts		0.7				(c)		(0.3		)	(c)
	Foreign exchange contracts		0.5				(c)		(1.1		)	(c)
			3.6				(d)		(14.0		)	(d)	Total before tax
			1.4						(5.4		)		Tax provision (benefit)
			$	2.2					$	(8.6	)		Net of tax
	(a)	Amounts are included in the computation of pension and other postretirement benefit expense, which is reported in both cost of goods sold and selling and administrative expenses. For additional information, see Note 11.
	(b)	Amount in 2014 is included in other income, net, and amount in 2013 is included in discontinued operations as part of the gain on sale of the tungsten materials business (see Note 3).
	(c)	Amounts are included in cost of goods sold in the period or periods the hedged item affects earnings. For additional information, see Note 9.
	(d)	For pretax items, positive amounts are income and negative amounts are expense in terms of the impact to net income. Tax effects are presented in conformity with ATI’s presentation in the consolidated statements of operations.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity
	Preferred Stock
	Authorized preferred stock may be issued in one or more series, with designations, powers and preferences as shall be designated by the Board of Directors. At December 31, 2014, there were no shares of preferred stock issued.
	Share-based Compensation
	During 2007, the Company adopted the Allegheny Technologies Incorporated 2007 Incentive Plan (the “Incentive Plan”), which was amended and restated in 2010 and further amended in 2012. Awards earned under share-based incentive compensation programs are generally paid with shares held in treasury, if sufficient treasury shares are held, and any additional required share payments are made with newly issued shares. At December 31, 2014, approximately 1.6 million shares of common stock were available for future awards under the Incentive Plan. The general terms of each arrangement granted under the Incentive Plan, and predecessor plans, the method of estimating fair value for each arrangement, and award activity is reported below.
	The Company sponsors two principal share-based incentive compensation programs, the Performance/Restricted Stock Program (PRSP) of nonvested stock awards, and the Long-Term Performance Plan (LTPP), which was adopted in 2014 and may include performance shares under the Total Shareholder Return (TSR) portion and nonvested stock awards under the Long-Term Shareholder Value (LTSV) portion. Prior periods include performance equity awards issued under the former Total Shareholder Return Program (TRSP), which has the same performance measurement criteria as the TSR.
	Nonvested stock awards: Awards of nonvested stock are granted to employees, with either performance and/or service conditions. Awards of nonvested stock are also granted to non-employee directors, with service conditions. For nonvested stock awarded in 2014, 2013 and 2012, dividend equivalents, whether in stock or cash form, accumulate but are not paid until the underlying award vests. In 2014, 492,773 shares of nonvested stock were granted to employees under the PRSP.
	In 2014, 113,827 shares of nonvested stock were also granted under the LTSV portion of the newly-adopted LTPP plan. The LTSV award vests at the end of a three-year measurement period subject to the achievement, in whole or in part, of specified Operational Goals. As of December 31, 2014, these Operational Goals were expected to be attained.
	The fair value of nonvested stock awards is measured based on the stock price at the grant date, adjusted for non-participating dividends, as applicable, based on the current dividend rate. For nonvested stock awards to employees in 2014, 2013, and 2012, under the Company’s PRSP, one-half of the nonvested stock (“performance shares”) vests only on the attainment of an income target, measured over a cumulative three-year period. The remaining nonvested stock awarded to employees vests over a service period of five years, with accelerated vesting to three years if the performance shares’ vesting criterion is attained. Expense for each of these awards is recognized based on estimates of attaining the performance criterion, including estimated forfeitures. As of December 31, 2014, the income target for the 2012 PRSP award was not met, and 171,083 shares were forfeited. Vesting of the remaining half of the 2012 PRSP award continues over the five-year service period through February 2017. The income target for the 2013 PRSP awards is not expected to be attained for the performance shares, therefore, no expense was recognized on the performance shares and expense for the remaining nonvested stock was recognized on a straight line basis over the five-year service period. As of December 31, 2014, the income target for the 2014 PRSP nonvested stock award is expected to be attained for the performance shares, and expense for both portions of the award was recognized on a straight line basis based on a three-year vesting assumption.
	Compensation expense in continuing operations related to all nonvested stock awards was $2.4 million in 2014, $11.3 million in 2013, and $14.0 million in 2012. Reduced compensation expense in 2014 is primarily the result of the forfeiture of the 2012 PRSP award performance shares. Approximately $18.9 million of unrecognized fair value compensation expense relating to nonvested stock awards is expected to be recognized through 2018 based on estimates of attaining performance vesting criteria, including estimated forfeitures. Activity under the Company’s nonvested stock awards for the years ended December 31, 2014, 2013, and 2012 was as follows:
	(Shares in thousands, $ in millions)	2014					2013					2012
		Number of		Weighted			Number of		Weighted			Number of		Weighted
		shares		Average			shares		Average Grant			shares		Average Grant
				Grant Date					Date Fair					Date Fair
				Fair Value					Value					Value
	Nonvested, beginning of year	927		$	36.9		727		$	38.6		677		$	36.4
	Granted	675		20.3			576		16.4			394		16.4
	Vested	(18	)	(1.0		)	(333	)	(16.4		)	(343	)	(14.1		)
	Forfeited	(208	)	(8.4		)	(43	)	(1.7		)	(1	)	(0.1		)
	Nonvested, end of year	1,376		$	47.8		927		$	36.9		727		$	38.6
	Performance equity awards: Award opportunities under the TSR, and previously the TSRP, are determined at a target number of shares, and performance equity awards pay out based on the measured return of the Company’s stock price and dividend performance at the end of three-year periods as compared to the stock price and dividend performance of a group of industry peers. In 2014, the Company established a 2014-2016 TSR award, with 319,955 shares as the target award level. A maximum of 1.85 million shares have been reserved for issuance for award periods under the TSR and the TSRP. The actual number of shares awarded at the end of the performance measurement period may range from a minimum of zero to a maximum of two times target. Fair values for these performance awards were estimated using Monte Carlo simulations of stock price correlation, projected dividend yields and other variables over three-year time horizons matching the total shareholder return performance measurement periods. Compensation expense from continuing operations was $9.8 million in 2014, $12.3 million in 2013, and $19.2 million in 2012 for the fair value of TSR and TSRP awards.
	The estimated fair value of each performance equity award, the projected shares to be awarded and future compensation expense to be recognized for these awards, including actual and estimated forfeitures, was as follows:
	(Shares in thousands, $ in millions)
	TSR / TSRP Award Performance Period	Award			December 31, 2014			Minimum		Target		Maximum
		Fair Value			Unrecognized			Shares		Shares		Shares
					Compensation
					Expense
	2012 - 2014	$	8.8		$	—		—		186		373
	2013 - 2015	$	11		3.7			—		309		618
	2014 - 2016	$	9.9		6.6			—		294		589
	Total				$	10.3		—		789		1,580
	An award was earned for the 2012-2014 TSRP performance period based on the Company’s stock price and dividend performance for the three-year period ended December 31, 2014 relative to the peer group, which resulted in the issuance of 137,843 shares of stock to participants in the 2015 first quarter.
	Undistributed Earnings of Investees
	Stockholders’ equity includes undistributed earnings of investees accounted for under the equity method of accounting of approximately $12 million at December 31, 2014.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	The income tax provision (benefit) was as follows:
	(In millions)	2014			2013			2012
	Continuing operations:
	Current:
	Federal	$	(47.9	)	$	(127.5	)	$	82.3
	State	(4.0		)	(10.2		)	8.7
	Foreign	9.8			7.9			9
	Total	(42.1		)	(129.8		)	100
	Deferred:
	Federal	34.1			62.7			(27.6		)
	State	(0.2		)	4.6			0.1
	Foreign	(0.5		)	(1.1		)	(0.1		)
	Total	33.4			66.2			(27.6		)
	Income tax provision (benefit) from continuing operations	$	(8.7	)	$	(63.6	)	$	72.4
	Income tax provision (benefit) from discontinued operations	$	(0.3	)	$	161.4		$	3.8
	Total company income tax provision (benefit)	$	(9.0	)	$	97.8		$	76.2
	The following is a reconciliation of income taxes computed at the statutory U.S. Federal income tax rate to the actual effective income tax provision (benefit) from continuing operations:
		Income Tax Provision (Benefit)
	(In millions)	2014			2013			2012
	Taxes computed at the federal rate	$	0.5		$	(54.2	)	$	81.3
	State and local income taxes, net of federal tax benefit	(2.0		)	(11.8		)	0.6
	Tax reserve adjustments	(0.5		)	(10.2		)	(0.4		)
	Repatriation of foreign earnings	0.3			9.4			1.3
	Valuation allowance	0.5			9.1			2.2
	Adjustment to prior years’ taxes	0.1			(5.3		)	1.4
	Foreign earnings taxed at different rate	(6.6		)	(2.5		)	(10.2		)
	Manufacturing deduction	—			—			(7.1		)
	Other	(1.0		)	1.9			3.3
	Income tax provision (benefit)	$	(8.7	)	$	(63.6	)	$	72.4
	In general, the Company is responsible for filing consolidated U.S. Federal, foreign and combined, unitary or separate state income tax returns. The Company is responsible for paying the taxes relating to such returns, including any subsequent adjustments resulting from the redetermination of such tax liability by the applicable taxing authorities. No provision has been made for U.S. Federal, state or additional foreign taxes related to approximately $181 million of undistributed earnings of foreign subsidiaries which have been permanently re-invested. It is not practical to determine the deferred tax liability on these earnings.
	Income (loss) from continuing operations before income taxes for the Company’s U.S. and non-U.S. operations was as follows:
	(In millions)	2014			2013			2012
	U.S.	$	(46.1	)	$	(180.0	)	$	178.4
	Non-U.S.	47.6			25.2			53.9
	Income (loss) from continuing operations before income taxes	$	1.5		$	(154.8	)	$	232.3
	Income taxes paid and amounts received as refunds were as follows:
	(In millions)	2014			2013			2012
	Income taxes paid	$	15.1		$	21.4		$	101.7
	Income tax refunds received	(20.2		)	(18.3		)	(15.8		)
	Income taxes paid (received), net	$	(5.1	)	$	3.1		$	85.9
	The Company’s income tax payments have benefited over the last several years from provisions under the U.S. tax code allowing companies to immediately deduct a significant portion of the cost of new capital investments placed into service. In the first-half of 2015, the Company expects to receive an approximately $60 million federal tax refund which relates to a refund of prior years’ taxes. After this refund, the Company expects to have approximately $76 million of tax-effected federal net operating loss carryforwards and $33.5 million of other federal tax credits to offset future federal tax liabilities.
	Deferred income taxes result from temporary differences in the recognition of income and expense for financial and income tax reporting purposes, and differences between the fair value of assets acquired in business combinations accounted for as purchases for financial reporting purposes and their corresponding tax bases. Deferred income taxes represent future tax benefits or costs to be recognized when those temporary differences reverse. The categories of assets and liabilities that have resulted in differences in the timing of the recognition of income and expense at December 31, 2014 and 2013 were as follows:
	(In millions)	2014			2013
	Deferred income tax assets
	Pensions	$	251.8		$	115.7
	Postretirement benefits other than pensions	169			182.9
	Federal and state net operating loss tax carryovers	122.7			32.2
	Federal and state tax credits	53.6			42
	Deferred compensation and other benefit plans	25.6			29.4
	Self insurance reserves	10.1			10.1
	Other items	79.1			79.5
	Gross deferred income tax assets	711.9			491.8
	Valuation allowance for deferred tax assets	(34.4		)	(33.9		)
	Total deferred income tax assets	677.5			457.9
	Deferred income tax liabilities
	Bases of property, plant and equipment	579.5			488.1
	Inventory valuation	111.7			66.5
	Bases of amortizable intangible assets	75.5			67.1
	Other items	53.9			46.3
	Total deferred tax liabilities	820.6			668
	Net deferred tax liability	$	(143.1	)	$	(210.1	)
	The Company had $34.4 million and $33.9 million in deferred tax asset valuation allowances at December 31, 2014 and 2013, respectively, related to federal foreign tax credits and state deferred tax assets. The valuation allowance at December 31, 2014 includes $2.3 million for federal foreign tax credits, $20.9 million for state net operating loss tax carryforwards, $10.0 million for state tax credits and $1.2 million for state temporary differences, since the Company has concluded, based on current state tax laws, that it is more likely than not that these tax benefits would not be realized. For these state net operating loss tax carryforwards, expiration will generally occur within 20 years of the year generated and utilization of the tax benefit is limited to $5 million per year or 30% of apportioned income, whichever is greater.
	The changes in the liability for unrecognized income tax benefits for the years ended December 31, 2014, 2013 and 2012 were as follows:
(In millions)	2014			2013			2012
Balance at beginning of year	$	72.8		$	29.2		$	29.7
Increases in prior period tax positions	2			0.1			0.2
Decreases in prior period tax positions	(0.6		)	(5.8		)	(0.3		)
Increases in current period tax positions	0.7			60.4			1.2
Expiration of the statute of limitations	(0.5		)	(0.7		)	(2.0		)
Settlements	(0.7		)	(8.6		)	(0.4		)
Interest and penalties, net	(0.3		)	(1.8		)	0.8
Balance at end of year	$	73.4		$	72.8		$	29.2
At December 31, 2014, interest and penalties included in the liability for unrecognized tax benefits were $4.4 million.
For the years ended December 31, 2014 and 2013, $60.9 million and $59.4 million, respectively, of the liability for unrecognized income tax benefits relates to temporary differences, which would not impact the effective tax rate upon resolution of the uncertainty. Including tax positions for which the Company determined that the tax position would not meet the more-likely-than-not recognition threshold upon examination by the tax authorities based upon the technical merits of the position, the total estimated unrecognized tax benefit that, if recognized, would affect ATI’s effective tax rate was approximately $9 million. At this time, the Company believes that it is reasonably possible that approximately $62 million of the estimated unrecognized tax benefits as of December 31, 2014 will be recognized within the next twelve months based on the expiration of statutory review periods.
The Company, and/or one of its subsidiaries, files income tax returns in the U.S. Federal jurisdiction and in various state and foreign jurisdictions. A summary of tax years that remain subject to examination, by major tax jurisdiction, is as follows:
Jurisdiction	Earliest Year Open to
	Examination
U.S. Federal	2013
States:
Alabama	2011
Illinois	2011
North Carolina	2010
Oregon	2011
Pennsylvania	2011
Foreign:
China	2010
Germany	2012
Poland	2010
United Kingdom	2011

Business_Segments

Business Segments	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Business Segments	Business Segments
	The Company operates in two business segments: High Performance Materials & Components and Flat Rolled Products. The High Performance Materials & Components business segment produces, converts and distributes a wide range of high performance materials, including titanium and titanium-based alloys, nickel- and cobalt-based alloys and superalloys, zirconium and related alloys including hafnium and niobium, advanced powder alloys and other specialty materials, in long product forms such as ingot, billet, bar, rod, wire, shapes and rectangles, and seamless tubes, plus precision forgings and castings, components and machined parts. These products are designed for the high performance requirements of such major end markets as aerospace and defense, oil and gas, chemical process industry, electrical energy, and medical. The business units in this segment include ATI Specialty Materials, ATI Specialty Alloys and Components, ATI Forged Products, ATI Cast Products and ATI Flowform Products.
	The Flat Rolled Products business segment produces, converts and distributes stainless steel, nickel-based alloys, specialty alloys, and titanium and titanium-based alloys, in a variety of product forms including plate, sheet, engineered strip, and Precision Rolled Strip® products, as well as grain-oriented electrical steel. The major end markets for our flat rolled products are oil and gas, chemical process industry, electrical energy, automotive, food processing equipment and appliances, construction and mining, electronics, communication equipment and computers, and aerospace and defense. The business units in this segment include ATI Flat Rolled Products and STAL, in which the Company has a 60% ownership interest. Segment results also include ATI’s 50% interest in Uniti, which is accounted for under the equity method. Sales to Uniti, which are included in ATI’s consolidated statements of operations, were $75.3 million in 2014, $95.9 million in 2013, and $77.1 million in 2012. ATI’s share of Uniti’s (loss)/income was $(8.9) million in 2014, $(7.1) million in 2013, and $4.9 million in 2012, which is included in the Flat Rolled Products segment’s operating profit, and within cost of sales in the consolidated statements of operations. The remaining 50% interest in Uniti is held by VSMPO, a Russian producer of titanium, aluminum, and specialty steel products.
	Intersegment sales are generally recorded at full cost or market. Common services are allocated on the basis of estimated utilization. Business segment results exclude amounts reported in discontinued operations.
	(In millions)		2014			2013				2012
	Total sales:
	High Performance Materials & Components		$	2,084.60		$	2,016.70			$	2,398.10
	Flat Rolled Products		2,320.20			2,146.60				2,398.90
	Total sales		4,404.80			4,163.30				4,797.00
	Intersegment sales:
	High Performance Materials & Components		77.8			71.9				84.1
	Flat Rolled Products		103.6			47.9				46
	Total intersegment sales		181.4			119.8				130.1
	Sales to external customers:
	High Performance Materials & Components		2,006.80			1,944.80				2,314.00
	Flat Rolled Products		2,216.60			2,098.70				2,352.90
	Total sales to external customers		$	4,223.40		$	4,043.50			$	4,666.90
	Total direct international sales were $1,607.5 million in 2014, $1,585.1 million in 2013, and $1,705.7 million in 2012. Of these amounts, sales by operations in the United States to customers in other countries were $1,201.8 million in 2014, $1,175.1 million in 2013, and $1,262.9 million in 2012.
	(In millions)		2014			2013				2012
	Operating profit (loss):
	High Performance Materials & Components		$	289.6		$	209.1			$	385.4
	Flat Rolled Products		(43.3		)	(44.7		)		127.8
	Total operating profit		246.3			164.4				513.2
	Corporate expenses		(44.2		)	(43.0		)		(68.4		)
	Interest expense, net		(108.7		)	(65.2		)		(71.6		)
	Restructuring costs		—			(67.5		)		—
	Closed company and other expenses		(21.2		)	(14.2		)		(18.5		)
	Retirement benefit expense		(70.7		)	(129.3		)		(122.4		)
	Income (loss) before income taxes		$	1.5		$	(154.8	)		$	232.3
	Business segment operating profit excludes costs for restructuring charges (see Note 16), retirement benefit income or expense, corporate expenses, interest expenses, debt extinguishment costs, and costs associated with closed operations. These costs are excluded for segment reporting to provide a profit measure based on what management considers to be controllable costs at the segment level. Retirement benefit expense includes both defined benefit pension expense and other postretirement benefit expenses. Costs associated with multiemployer pension plans are included in segment operating profit, and costs associated with defined contribution retirement plans are included in segment operating profit or corporate expenses, as applicable.
	Business segment operating profit for 2013 includes a $55.5 million charge for inventory valuation adjustments, including a $35.0 million LIFO-related net realizable value charge in the High Performance Materials & Components segment and a $20.5 million charge related to the market-based valuation of industrial titanium products in the Flat Rolled Products segment. The $35.0 million net realizable value reserve in the High Performance Materials & Components segment was reduced to $10.0 million at December 31, 2014. A charge of $23.2 million related to the market-based valuation of industrial titanium products was recorded in 2014 in the Flat Rolled Products segment.
	Closed company and other expenses, which were $21.2 million in 2014, $14.2 million in 2013 and $18.5 million in 2012, includes charges incurred in connection with closed operations, pre-tax gains and losses on the sale of surplus real estate, non-strategic investments, and other assets, and other non-operating income or expense. Other items are primarily presented in selling and administrative expenses in the consolidated statements of operations. In 2014, these other items included $8.0 million for closed company environmental costs, $3.8 million for closed company insurance obligations, and $9.4 million for other expenses including legal matters and real estate costs at closed companies. In 2013, the Company recorded $14.2 million in other charges primarily related to closed companies, including $3.9 million for environmental costs and $10.3 million for other expenses including real estate costs at closed companies. In 2012, the Company recorded $18.5 million in other charges primarily related to closed companies, including $4.3 million for environmental costs, $4.0 million for real estate costs at closed companies, and $10.2 million for other expenses including legal matters and foreign exchange losses.
	Certain additional information regarding the Company’s business segments is presented below:
	(In millions)		2014			2013				2012
	Depreciation and amortization:
	High Performance Materials & Components		$	124.4		$	127.4			$	130
	Flat Rolled Products		49.3			49.5				49.7
	Corporate		2.9			3.7				1.7
	Total depreciation and amortization		176.6			180.6				181.4
	Capital expenditures:
	High Performance Materials & Components		51.9			39.5				59.9
	Flat Rolled Products		172.1			568.1				311.3
	Corporate		1.7			0.2				1.3
	Total capital expenditures		225.7			607.8				372.5
	Identifiable assets:		2014			2013				2012
	High Performance Materials & Components		3,555.80			3,452.20				3,720.70
	Flat Rolled Products		2,601.60			2,320.90				1,857.00
	Discontinued Operations		1.8			9.8				214
	Corporate:
	Prepaid pension cost		—			5.1				—
	Deferred taxes		—			—				71.5
	Cash and cash equivalents and other		423.4			1,110.50				384.6
	Total assets		$	6,582.60		$	6,898.50			$	6,247.80
	Geographic information for external sales based on country of destination, and assets, are as follows:
	($ in millions)		2014			Percent			2013				Percent		2012		Percent
						of total							of total				of total
	External sales:
	United States		$	2,615.90		62	%		$	2,458.40			61	%	$	2,961.10	63	%
	China		249.6			6	%		237.7				6	%	255.4		5	%
	United Kingdom		228.4			5	%		251.5				6	%	303.9		7	%
	Germany		207.7			5	%		215.4				5	%	256		6	%
	France		168.1			4	%		152.8				4	%	157		3	%
	Italy		160.7			4	%		132.3				3	%	136.1		3	%
	Canada		147			3	%		141				4	%	134.9		3	%
Japan		89.3			2	%		124.7				3	%	93.7		2	%
Mexico		76.5			2	%		54.9				1	%	49.3		1	%
Other		280.2			7	%		274.8				7	%	319.5		7	%
Total External Sales		$	4,223.40		100	%		$	4,043.50			100	%	$	4,666.90	100	%
($ in millions)		2014			Percent			2013				Percent		2012		Percent
					of total							of total				of total
Total assets:
United States		$	5,879.60		90	%		$	6,145.40			89	%	$	5,505.00	88	%
China		280.5			4	%		258.1				4	%	276.2		4	%
United Kingdom		196.3			3	%		208				3	%	239.2		4	%
Luxembourg (a)		81.8			1	%		145.9				2	%	48.3		1	%
Other		144.4			2	%		141.1				2	%	179.1		3	%
Total Assets		$	6,582.60		100	%		$	6,898.50			100	%	$	6,247.80	100	%
(a)	Comprises assets held by the Company’s European Treasury Center operation.

Restructuring_Costs

Restructuring Costs	12 Months Ended
	Dec. 31, 2014
Restructuring and Related Activities [Abstract]
Restructuring Costs	Restructuring Costs
	For the year ended December 31, 2013, the Company recorded pre-tax restructuring charges in continuing operations of $67.5 million ($41.2 million after-tax or $0.39 per share) which are presented as restructuring costs in the consolidated statement of operations. These pre-tax charges were comprised of $55.1 million in non-cash long-lived asset impairment charges, $4.2 million in facility closure costs and $8.2 million in employee severance and termination benefit charges. The non-cash long-lived asset impairment charges were based on analysis of the estimated fair values, which represents Level 3 unobservable information in the fair value hierarchy.
	•	In the High Performance Materials & Components segment, the Company permanently closed the previously idled Albany, Oregon standard-grade titanium sponge facility, resulting in a $38.1 million non-cash asset impairment charge in 2013. In addition, a charge was recorded for $3.5 million of asset retirement obligations, which were substantially completed in 2014.
	•	In the Flat Rolled Products segment, the Company permanently closed the previously idled New Castle, Indiana stainless finishing facility in 2013, and the Wallingford, Connecticut stainless finishing facility in 2014. The closure of New Castle and Wallingford resulted in $6.3 million and $2.7 million, respectively, of non-cash asset impairment charges in 2013. Facility closure costs in 2013 included $0.3 million and $0.4 million in asset retirement obligations for New Castle and Wallingford, respectively. Additionally, pension and other postretirement benefit termination charges of $5.0 million, and $1.0 million of employee termination costs were recognized in 2013 for approximately 65 employees affected by the Wallingford facility closure.
	In addition to the above facility closures, restructuring costs in 2013 included $8.0 million of other non-cash long-lived asset impairment charges in the High Performance Materials & Components segment. Other severance charges in 2013 included $1.1 million in pension benefit termination charges in the High Performance Materials & Components segment, and $1.1 million in severance costs, collectively affecting approximately 75 employees.
	Reserves for restructuring charges at December 31, 2013 were approximately $2 million for severance costs, which were paid in 2014.

Redeemable_Noncontrolling_Inte

Redeemable Noncontrolling Interest	12 Months Ended
	Dec. 31, 2014
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interest	Redeemable Noncontrolling Interest
	The holders of the 15% noncontrolling interest in ATI Flowform Products have a put option to require the Company to purchase their equity interest at a redemption value determinable from a specified formula based on a multiple of EBITDA (subject to a fixed minimum linked to the original acquisition date value). The put option is fully exercisable beginning in the second quarter of 2017, and is also exercisable under certain other circumstances. The put option cannot be separated from the noncontrolling interest, and the combination of a noncontrolling interest and the redemption feature requires classification as redeemable noncontrolling interest in the consolidated balance sheet, separate from Stockholders’ Equity.
	The carrying amount of the redeemable noncontrolling interest approximates its maximum redemption value. Any subsequent change in maximum redemption value is adjusted through retained earnings. The adjustment to the carrying amount for the year ended December 31, 2014 reduced retained earnings by $0.3 million. The Company applied the two-class method of calculating earnings per share, and as such this adjustment to the carrying amount was reflected in earnings per share. The redeemable noncontrolling interest was $12.1 million as of December 31, 2014, which was unchanged from the acquisition date value.

Per_Share_Information

Per Share Information	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Per Share Information	Per Share Information
	The following table sets forth the computation of basic and diluted income (loss) from continuing operations per common share:
	(In millions, except per share amounts)
	For the Years Ended December 31,	2014			2013			2012
	Numerator:
	Numerator for basic income (loss) from continuing operations per common share -
	Income (loss) from continuing operations attributable to ATI	$	(2.0	)	$	(98.8	)	$	150.5
	Redeemable noncontrolling interest (Note 17)	(0.3		)	—			—
	Effect of dilutive securities:
	4.25% Convertible Senior Notes due 2014	—			—			8.5
	Numerator for diluted net income (loss) per common share -
	Income (loss) from continuing operations attributable to ATI after assumed conversions	$	(2.3	)	$	(98.8	)	$	159
	Denominator:
	Denominator for basic net income per common share—weighted average shares	107.1			106.8			106.1
	Effect of dilutive securities:
	Share-based compensation	—			—			0.9
	4.25% Convertible Senior Notes due 2014	—			—			9.6
	Denominator for diluted net income per common share—adjusted weighted average shares and assumed conversions	107.1			106.8			116.6
	Basic income (loss) from continuing operations attributable to ATI per common share	$	(0.02	)	$	(0.93	)	$	1.42
	Diluted income (loss) from continuing operations attributable to ATI per common share	$	(0.02	)	$	(0.93	)	$	1.36
	Common stock that would be issuable upon the assumed conversion of the 2014 Convertible Notes (prior to maturity on June 2, 2014) and other option equivalents and contingently issuable shares are excluded from the computation of contingently issuable shares, and therefore, from the denominator for diluted earnings per share, if the effect of inclusion would have been anti-dilutive. Excluded shares were 4.7 million for 2014, and 10.0 million for 2013. There were no anti-dilutive shares for 2012.

Financial_Information_for_Subs

Financial Information for Subsidiary and Guarantor Parent	12 Months Ended
	Dec. 31, 2014
Financial Information for Subsidiary and Guarantor Parent [Abstract]
Financial Information for Subsidiary and Guarantor Parent	Financial Information for Subsidiary and Guarantor Parent
	The payment obligations under the $150.0 million 6.95% Debentures due 2025 issued by Allegheny Ludlum, LLC (formerly known as Allegheny Ludlum Corporation) (the “Subsidiary”) are fully and unconditionally guaranteed by Allegheny Technologies Incorporated (the “Guarantor Parent”). In accordance with positions established by the U.S. Securities and Exchange Commission, the following financial information sets forth separately financial information with respect to the Subsidiary, the Non-guarantor Subsidiaries and the Guarantor Parent. The principal elimination entries eliminate investments in subsidiaries and certain intercompany balances and transactions.
	Allegheny Technologies is the plan sponsor for the U.S. qualified defined benefit pension plan (the “Plan”) which covers certain current and former employees of the Subsidiary and the Non-guarantor Subsidiaries. As a result, the balance sheets presented for the Subsidiary and the Non-guarantor Subsidiaries do not include any Plan assets or liabilities, or the related deferred taxes. The Plan assets, liabilities and related deferred taxes and pension income or expense are recognized by the Guarantor Parent. Management and royalty fees charged to the Subsidiary and to the Non-guarantor Subsidiaries by the Guarantor Parent have been excluded solely for purposes of this presentation.
	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Balance Sheets
	December 31, 2014
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Assets:
	Cash and cash equivalents	$	2.2		$	13.8		$	253.5		$	—		$	269.5
	Accounts receivable, net	0.1			209.1			394.4			—			603.6
	Intercompany notes receivable	—			—			2,390.80			(2,390.8		)	—
	Inventories, net	—			387.7			1,085.10			—			1,472.80
	Prepaid expenses and other current assets	63.7			13.2			59.3			—			136.2
	Total current assets	66			623.8			4,183.10			(2,390.8		)	2,482.10
	Property, plant and equipment, net	2.2			1,545.10			1,414.50			—			2,961.80
	Cost in excess of net assets acquired	—			126.6			653.8			—			780.4
	Intercompany notes receivable	—			—			200			(200.0		)	—
	Investments in subsidiaries	6,149.40			37.7			—			(6,187.1		)	—
	Other assets	23.7			28			306.6			—			358.3
	Total assets	$	6,241.30		$	2,361.20		$	6,758.00		$	(8,777.9	)	$	6,582.60
	Liabilities and stockholders’ equity:
	Accounts payable	$	4.5		$	302		$	250.2		$	—		$	556.7
	Accrued liabilities	47.5			72			203.7			—			323.2
	Intercompany notes payable	1,232.60			1,158.20			—			(2,390.8		)	—
	Deferred income taxes	62.2			—			—			—			62.2
	Short-term debt and current portion of long-term debt	0.5			0.1			17.2			—			17.8
	Total current liabilities	1,347.30			1,532.30			471.1			(2,390.8		)	959.9
	Long-term debt	1,350.60			150.3			8.2			—			1,509.10
	Intercompany notes payable	—			200			—			(200.0		)	—
	Accrued postretirement benefits	—			153			262.8			—			415.8
	Pension liabilities	675.5			6			57.8			—			739.3
	Deferred income taxes	80.9			—			—			—			80.9
	Other long-term liabilities	77.7			22.5			56			—			156.2
	Total liabilities	3,532.00			2,064.10			855.9			(2,590.8		)	3,861.20
	Redeemable noncontrolling interest	—			—			12.1			—			12.1
	Total stockholders’ equity	2,709.30			297.1			5,890.00			(6,187.1		)	2,709.30
	Total liabilities and stockholders’ equity	$	6,241.30		$	2,361.20		$	6,758.00		$	(8,777.9	)	$	6,582.60
	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Statements of Operations
	For the year ended December 31, 2014
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Sales	$	—		$	1,878.00		$	2,345.40		$	—		$	4,223.40
	Cost of sales	45.3			1,874.80			1,924.70			—			3,844.80
	Selling and administrative expenses	103.9			44			124.6			—			272.5
	Income (loss) before interest, other income and income taxes	(149.2		)	(40.8		)	296.1			—			106.1
	Interest income (expense), net	(111.0		)	(44.9		)	47.2			—			(108.7		)
	Other income (expense) including equity in income of unconsolidated subsidiaries	261.7			1.1			2.9			(261.6		)	4.1
	Income (loss) from continuing operations before income taxes	1.5			(84.6		)	346.2			(261.6		)	1.5
	Income tax provision (benefit)	(8.7		)	(29.3		)	116.7			(87.4		)	(8.7		)
	Income (loss) from continuing operations	10.2			(55.3		)	229.5			(174.2		)	10.2
	Income (loss) from discontinued operations, net of tax	(0.6		)	—			(0.6		)	0.6			(0.6		)
	Net income (loss)	9.6			(55.3		)	228.9			(173.6		)	9.6
	Less: Net income attributable to noncontrolling interest	—			—			12.2			—			12.2
	Net income (loss) attributable to ATI	$	9.6		$	(55.3	)	$	216.7		$	(173.6	)	$	(2.6	)
	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Statements of Comprehensive Income
	For the year ended December 31, 2014
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
Net income (loss)	$	9.6		$	(55.3	)	$	228.9		$	(173.6	)	$	9.6
Other comprehensive income (loss)
Currency translation adjustment arising during the period	(33.6		)	—			(33.6		)	33.6			(33.6		)
Net derivative gain on hedge transactions	25.9			—			—			—			25.9
Pension and postretirement benefits	(212.6		)	1.8			(28.4		)	26.6			(212.6		)
Other comprehensive income (loss), net of tax	(220.3		)	1.8			(62.0		)	60.2			(220.3		)
Comprehensive income (loss)	(210.7		)	(53.5		)	166.9			(113.4		)	(210.7		)
Less: Comprehensive income attributable to noncontrolling interest	—			—			10.1			—			10.1
Comprehensive income (loss) attributable to ATI	$	(210.7	)	$	(53.5	)	$	156.8		$	(113.4	)	$	(220.8	)
Condensed Statements of Cash Flows
For the year ended December 31, 2014
(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
	Parent						Subsidiaries
Cash flows provided by (used in) operating activities	$	(66.9	)	$	(313.8	)	$	436.6		$	—		$	55.9
Investing Activities:
Purchases of property, plant and equipment	(0.1		)	(170.8		)	(54.8		)	—			(225.7		)
Net receipts (payments) on intercompany activity	—			—			(1,027.7		)	1,027.70			—
Purchases of businesses, net of cash acquired	—			—			(92.9		)	—			(92.9		)
Asset disposals and other	—			1.7			0.7			—			2.4
Cash flows provided by (used in) investing activities	(0.1		)	(169.1		)	(1,174.7		)	1,027.70			(316.2		)
Financing Activities:
Payments on long-term debt and capital leases	(397.9		)	(0.1		)	(16.9		)	—			(414.9		)
Net receipts (payments) on intercompany activity	544.4			483.3			—			(1,027.7		)	—
Dividends paid to stockholders	(77.1		)	—			—			—			(77.1		)
Other	(3.8		)	—			(1.2		)	—			(5.0		)
Cash flows provided by (used in) financing activities	65.6			483.2			(18.1		)	(1,027.7		)	(497.0		)
Increase (decrease) in cash and cash equivalents	$	(1.4	)	$	0.3		$	(756.2	)	$	—		$	(757.3	)
Allegheny Technologies Incorporated
Financial Information for Subsidiary and Guarantor Parent
Balance Sheets
December 31, 2013
(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
	Parent						Subsidiaries
Assets:
Cash and cash equivalents	$	3.6		$	13.5		$	1,009.70		$	—		$	1,026.80
Accounts receivable, net	0.3			179.4			348.5			—			528.2
Intercompany notes receivable	—			—			1,589.40			(1,589.4		)	—
Inventories, net	—			295.5			1,026.60			—			1,322.10
Prepaid expenses and other current assets	26.2			6.5			41			—			73.7
Total current assets	30.1			494.9			4,015.20			(1,589.4		)	2,950.80
Property, plant and equipment, net	2.9			1,397.50			1,473.70			—			2,874.10
Cost in excess of net assets acquired	—			112.1			615.8			—			727.9
Intercompany notes receivable	—			—			200			(200.0		)	—
Investments in subsidiaries	6,170.80			37.7			—			(6,208.5		)	—
Other assets	35.7			32			278			—			345.7
Total assets	$	6,239.50		$	2,074.20		$	6,582.70		$	(7,997.9	)	$	6,898.50
Liabilities and stockholders’ equity:
Accounts payable	$	3.1		$	310.5		$	158.2		$	—		$	471.8
Accrued liabilities	51.6			56.6			207.6			—			315.8
Intercompany notes payable	825.6			763.8			—			(1,589.4		)	—
Deferred income taxes	3.5			—			—			—			3.5
Short-term debt and current portion of long-term debt	402.9			0.1			16.9			—			419.9
Total current liabilities	1,286.70			1,131.00			382.7			(1,589.4		)	1,211.00
Long-term debt	1,350.80			150.4			26.2			—			1,527.40
Intercompany notes payable	—			200			—			(200.0		)	—
Accrued postretirement benefits	—			179.7			262.7			—			442.4
Pension liabilities	323			5.6			39.6			—			368.2
Deferred income taxes	206.6			—			—			—			206.6
Other long-term liabilities	77.7			20.2			50.3			—			148.2
Total liabilities	3,244.80			1,686.90			761.5			(1,789.4		)	3,903.80
Total stockholders’ equity	2,994.70			387.3			5,821.20			(6,208.5		)	2,994.70
Total liabilities and stockholders’ equity	$	6,239.50		$	2,074.20		$	6,582.70		$	(7,997.9	)	$	6,898.50
Allegheny Technologies Incorporated
Financial Information for Subsidiary and Guarantor Parent
Statements of Operations
For the year ended December 31, 2013
(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
	Parent						Subsidiaries
Sales	$	—		$	1,769.40		$	2,274.10		$	—		$	4,043.50
Cost of sales	75.2			1,748.80			1,966.90			—			3,790.90
Selling and administrative expenses	124.3			34.9			117.2			—			276.4
Restructuring costs	1.1			15.7			50.7			—			67.5
Income (loss) before interest, other income and income taxes	(200.6		)	(30.0		)	139.3			—			(91.3		)
Interest income (expense), net	(63.4		)	(37.2		)	35.4			—			(65.2		)
Other income (expense) including equity in income of unconsolidated subsidiaries	109.2			0.9			0.8			(109.2		)	1.7
Income (loss) from continuing operations before income taxes	(154.8		)	(66.3		)	175.5			(109.2		)	(154.8		)
Income tax provision (benefit)	(63.6		)	(20.0		)	40.4			(20.4		)	(63.6		)
Income (loss) from continuing operations	(91.2		)	(46.3		)	135.1			(88.8		)	(91.2		)
Income (loss) from discontinued operations, net of tax	252.8			—			252.8			(252.8		)	252.8
Net income (loss)	161.6			(46.3		)	387.9			(341.6		)	161.6
Less: Net income attributable to noncontrolling interest	—			—			7.6			—			7.6
Net income (loss) attributable to ATI	$	161.6		$	(46.3	)	$	380.3		$	(341.6	)	$	154
Allegheny Technologies Incorporated
Financial Information for Subsidiary and Guarantor Parent
Statements of Comprehensive Income
For the year ended December 31, 2013
(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
	Parent						Subsidiaries
Net income (loss)	$	161.6		$	(46.3	)	$	387.9		$	(341.6	)	$	161.6
Other comprehensive income (loss)
Currency translation adjustment arising during the period	15.3			—			15.3			(15.3		)	15.3
Unrealized holding gain (loss) on securities	0.1			—			0.1			(0.1		)	0.1
Net derivative loss on hedge transactions	(6.9		)	—			—			—			(6.9		)
Pension and postretirement benefits	311.1			22			27.6			(49.6		)	311.1
Other comprehensive income (loss), net of tax	319.6			22			43			(65.0		)	319.6
Comprehensive income (loss)	481.2			(24.3		)	430.9			(406.6		)	481.2
Less: Comprehensive income attributable to noncontrolling interest	—			—			11			—			11
Comprehensive income (loss) attributable to ATI	$	481.2		$	(24.3	)	$	419.9		$	(406.6	)	$	470.2
Condensed Statements of Cash Flows
For the year ended December 31, 2013
(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
	Parent						Subsidiaries
Cash flows provided by (used in) operating activities	$	(41.1	)	$	(50.4	)	$	484.2		$	(24.3	)	$	368.4
Investing Activities:
Purchases of property, plant and equipment	(0.2		)	(564.8		)	(47.7		)	—			(612.7		)
Net receipts (payments) on intercompany activity	—			—			(248.8		)	248.8			—
Proceeds from sale of business, net of transaction costs	(7.9		)	—			608.8			—			600.9
Asset disposals and other	—			0.2			0.6			—			0.8
Cash flows provided by (used in) investing activities	(8.1		)	(564.6		)	312.9			248.8			(11.0		)
Financing Activities:
Borrowings on long-term debt	500			—			—			—			500
Net receipts (payments) on intercompany acivity	(366.7		)	615.5			—			(248.8		)	—
Dividends paid to stockholders	(76.9		)	—			(24.3		)	24.3			(76.9		)
Other	(9.1		)	(0.1		)	(49.1		)	—			(58.3		)
Cash flows provided by (used in) financing activities	47.3			615.4			(73.4		)	(224.5		)	364.8
Increase (decrease) in cash and cash equivalents	$	(1.9	)	$	0.4		$	723.7		$	—		$	722.2
Allegheny Technologies Incorporated
Financial Information for Subsidiary and Guarantor Parent
Statements of Operations
For the year ended December 31, 2012
(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
	Parent						Subsidiaries
Sales	$	—		$	2,031.80		$	2,635.10		$	—		$	4,666.90
Cost of sales	57			1,888.20			2,096.20			—			4,041.40
Selling and administrative expenses	144.2			42.6			134.8			—			321.6
Income (loss) before interest, other income and income taxes	(201.2		)	101			404.1			—			303.9
Interest expense, net	(60.7		)	(10.5		)	(0.4		)	—			(71.6		)
Other income (expense) including equity in income of unconsolidated subsidiaries	494.2			(21.5		)	31.8			(504.5		)	—
Income (loss) from continuing operations, before income taxes	232.3			69			435.5			(504.5		)	232.3
Income tax provision (benefit)	72.4			27.5			168.7			(196.2		)	72.4
Income (loss) from continuing operations	159.9			41.5			266.8			(308.3		)	159.9
Income (loss) from discontinued operations, net of tax	7.9			—			7.9			(7.9		)	7.9
Net income (loss)	167.8			41.5			274.7			(316.2		)	167.8
Less: Net income (loss) attributable to noncontrolling interest	—			—			9.4			—			9.4
Net income (loss) attributable to ATI	$	167.8		$	41.5		$	265.3		$	(316.2	)	$	158.4
Allegheny Technologies Incorporated
Financial Information for Subsidiary and Guarantor Parent
Statements of Comprehensive Income
For the year ended December 31, 2012
(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
	Parent						Subsidiaries
Net income (loss)	$	167.8		$	41.5		$	274.7		$	(316.2	)	$	167.8
Other comprehensive income (loss)
Currency translation adjustment arising during the period	14.3			—			14.3			(14.3		)	14.3
Net derivative loss on hedge transactions	(2.8		)	—			—			—			(2.8		)
Pension and postretirement benefits	(97.4		)	(18.1		)	(5.1		)	23.2			(97.4		)
Other comprehensive income (loss), net of tax	(85.9		)	(18.1		)	9.2			8.9			(85.9		)
Comprehensive income (loss)	81.9			23.4			283.9			(307.3		)	81.9
Less: Comprehensive income attributable to noncontrolling interest	—			—			11.3			—			11.3
Comprehensive income (loss) attributable to ATI	$	81.9		$	23.4		$	272.6		$	(307.3	)	$	70.6
Condensed Statements of Cash Flows
For the year ended December 31, 2012
(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
	Parent						Subsidiaries
Cash flows provided by (used in) operating activities	$	(52.3	)	$	43.9		$	435.9		$	—		$	427.5
Investing Activities:
Purchases of property, plant and equipment	(1.7		)	(308.6		)	(71.7		)	—			(382.0		)
Net receipts (payments) on intercompany activity	—			—			(304.4		)	304.4			—
Asset disposals and other	—			0.3			3			—			3.3
Cash flows provided by (used in) investing activities	(1.7		)	(308.3		)	(373.1		)	304.4			(378.7		)
Financing Activities:
Net receipts (payments) on intercompany activity	156.5			147.9			—			(304.4		)	—
Dividends paid to stockholders	(76.5		)	—			—			—			(76.5		)
Other	(21.2		)	(0.1		)	(27.0		)	—			(48.3		)
Cash flows provided by (used in) financing activities	58.8			147.8			(27.0		)	(304.4		)	(124.8		)
Increase (decrease) in cash and cash equivalents	$	4.8		$	(116.6	)	$	35.8		$	—		$	(76.0	)

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	Rental expense from continuing operations under operating leases was $22.4 million in 2014, $20.5 million in 2013, and $22.5 million in 2012. Future minimum rental commitments under operating leases with non-cancelable terms of more than one year at December 31, 2014, were as follows: $19.2 million in 2015, $17.7 million in 2016, $15.3 million in 2017, $13.5 million in 2018, $8.0 million in 2019 and $24.3 million thereafter. Commitments for expenditures on property, plant and equipment at December 31, 2014 were approximately $118.0 million.
	The Company is subject to various domestic and international environmental laws and regulations that govern the discharge of pollutants and disposal of wastes, and which may require that it investigate and remediate the effects of the release or disposal of materials at sites associated with past and present operations. The Company could incur substantial cleanup costs, fines, and civil or criminal sanctions, third party property damage or personal injury claims as a result of violations or liabilities under these laws or noncompliance with environmental permits required at its facilities. The Company is currently involved in the investigation and remediation of a number of its current and former sites, as well as third party sites.
	Environmental liabilities are recorded when the Company’s liability is probable and the costs are reasonably estimable. In many cases, however, the Company is not able to determine whether it is liable or, if liability is probable, to reasonably estimate the loss or range of loss. Estimates of the Company’s liability remain subject to additional uncertainties, including the nature and extent of site contamination, available remediation alternatives, the extent of corrective actions that may be required, and the number, participation, and financial condition of other PRPs. The Company adjusts its accruals to reflect new information as appropriate. Future adjustments could have a material adverse effect on the Company’s consolidated results of operations in a given period, but the Company cannot reliably predict the amounts of such future adjustments.
	At December 31, 2014, the Company’s reserves for environmental remediation obligations totaled approximately $17 million, of which $9 million was included in other current liabilities. The reserve includes estimated probable future costs of $5 million for federal Superfund and comparable state-managed sites; $10 million for formerly owned or operated sites for which the Company has remediation or indemnification obligations; $1 million for owned or controlled sites at which Company operations have been discontinued; and $1 million for sites utilized by the Company in its ongoing operations. The Company continues to evaluate whether it may be able to recover a portion of future costs for environmental liabilities from third parties and to pursue such recoveries where appropriate.
	Based on currently available information, it is reasonably possible that the costs for active matters may exceed the Company’s recorded reserves by as much as $11 million. However, future investigation or remediation activities may result in the discovery of additional hazardous materials, potentially higher levels of contamination than discovered during prior investigation, and may impact costs of the success or lack thereof in remedial solutions. Therefore, future developments, administrative actions or liabilities relating to environmental matters could have a material adverse effect on the Company’s consolidated financial condition or results of operations.
	The timing of expenditures depends on a number of factors that vary by site. The Company expects that it will expend present accruals over many years and that remediation of all sites with which it has been identified will be completed within thirty years.
	A number of other lawsuits, claims and proceedings have been or may be asserted against the Company relating to the conduct of its currently and formerly owned businesses, including those pertaining to product liability, patent infringement, commercial, government contracting, employment, employee and retiree benefits, taxes, environmental, health and safety, occupational disease, and stockholder and corporate governance matters. While the outcome of litigation cannot be predicted with certainty, and some of these lawsuits, claims or proceedings may be determined adversely to the Company, management does not believe that the disposition of any such pending matters is likely to have a material adverse effect on the Company’s consolidated financial condition or liquidity, although the resolution in any reporting period of one or more of these matters could have a material adverse effect on the Company’s consolidated results of operations for that period.

Selected_Quarterly_Financial_D

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data
	(Unaudited)
		Quarter Ended
	(In millions, except share and per share amounts)	March 31			June 30			September 30			December 31
	2014 -
	Sales	$	987.3		$	1,119.00		$	1,069.60		$	1,047.50
	Gross Profit	70.2			89.5			97			121.9
	Income (loss) from continuing operations attributable to ATI	(18.1		)	(3.8		)	—			19.9
	Net income (loss)	(17.9		)	(0.7		)	2.9			25.3
	Net income (loss) attributable to ATI	(20.0		)	(4.0		)	(0.7		)	22.1
	Basic income (loss) from continuing operations attributable to ATI per common share	$	(0.17	)	$	(0.03	)	$	—		$	0.18
	Basic income (loss) attributable to ATI per common share	$	(0.19	)	$	(0.03	)	$	(0.01	)	$	0.2
	Diluted income (loss) from continuing operations attributable to ATI per common share	$	(0.17	)	$	(0.03	)	$	—		$	0.18
	Diluted income (loss) attributable to ATI per common share	$	(0.19	)	$	(0.03	)	$	(0.01	)	$	0.2
	Average shares outstanding	108,173,581			108,628,024			108,712,682			108,704,983
	2013 -
	Sales	$	1,099.00		$	1,056.80		$	972.4		$	915.3
	Gross Profit	100.5			87.7			53.1			11.3
	Income (loss) from continuing operations attributable to ATI	9.7			3.7			(28.4		)	(83.8		)
	Net income (loss)	11.6			6.6			(32.2		)	175.6
	Net income (loss) attributable to ATI	10			4.4			(33.8		)	173.4
	Basic income (loss) from continuing operations attributable to ATI per common share	$	0.09		$	0.04		$	(0.27	)	$	(0.79	)
	Basic income (loss) attributable to ATI per common share	$	0.09		$	0.04		$	(0.32	)	$	1.62
	Diluted income (loss) from continuing operations attributable to ATI per common share	$	0.09		$	0.04		$	(0.27	)	$	(0.79	)
	Diluted income (loss) attributable to ATI per common share	$	0.09		$	0.04		$	(0.32	)	$	1.62
	Average shares outstanding	107,614,468			107,980,753			108,001,306			107,984,535
	Fourth quarter 2014 results from continuing operations include postretirement benefit curtailment and settlement gains of $25.5 million pre-tax ($18.4 million, net of tax).
	Fourth quarter 2013 results from continuing operations included restructuring costs of $41.2 million, net of tax, for non-cash long-lived asset impairment charges, facility closure costs and employee severance and termination benefits (see Note 16). Net income (loss) and net income (loss) attributable to ATI includes discontinued operations, which includes a $261.4 million after-tax gain in 2013 from the sale of the Company’s tungsten materials business. In addition, results from discontinued operations for the third and fourth quarters of 2013 also include $5.8 million and $6.1 million after-tax charges, respectively, for non-cash asset impairment charges and facility closure costs associated with the iron castings and fabricated components divestitures.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies - Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation
	The consolidated financial statements include the accounts of Allegheny Technologies Incorporated and its subsidiaries, including the Chinese joint venture known as Shanghai STAL Precision Stainless Steel Company Limited (“STAL”), in which the Company has a 60% interest. The remaining 40% interest in STAL is owned by Baosteel Group, a state authorized investment company whose equity securities are publicly traded in the People’s Republic of China. The financial results of STAL are consolidated into the Company’s operating results and financial position, with the 40% interest of our minority partner recognized in the consolidated statement of income as net income attributable to noncontrolling interests and as equity attributable to the noncontrolling interest within total stockholders’ equity. Investments in which the Company exercises significant influence, but which it does not control (generally a 20% to 50% ownership interest), including ATI’s 50% interest in the industrial titanium joint venture known as Uniti LLC (“Uniti”), are accounted for under the equity method of accounting. Accounts receivable from Uniti were $4.3 million and $3.1 million at December 31, 2014 and 2013, respectively. Significant intercompany accounts and transactions have been eliminated. Unless the context requires otherwise, “Allegheny Technologies,” “ATI” and the “Company” refer to Allegheny Technologies Incorporated and its subsidiaries.
Basis of Presentation	Basis of Presentation
	ATI’s strategic vision is to be an aligned and integrated specialty materials and components company. In connection with this initiative, in the first quarter of 2014, the High Performance Metals segment was renamed the High Performance Materials & Components segment. Individual business unit names within each segment were also changed to reflect their aligned and integrated product focus. There was no change to the business units that comprise each business segment or the manner in which resources are allocated and performance is assessed for the business units by management. Therefore, there was no change to business segment reporting as a result of this initiative. Certain prior year amounts have been reclassified in order to conform with 2014 presentation.
Use of Estimates	Risks and Uncertainties and Use of Estimates
	The preparation of consolidated financial statements in conformity with United States generally accepted accounting principles requires management to make estimates and assumptions that affect reported amounts of assets and liabilities at the date of the financial statements, as well as the reported amounts of income and expenses during the reporting period. Actual results could differ from those estimates. Management believes that the estimates are reasonable.
Concentration Risks	The Company markets its products to a diverse customer base, principally throughout the United States. No single customer accounted for more than 10% of sales for any year presented. The principal end markets for the ATI’s products are customers in the aerospace and defense, oil & gas/chemical process industry, electrical energy, automotive, construction and mining, food equipment and appliances, and medical markets.
Cash Equivalents and Investments	Cash Equivalents and Investments
	Cash equivalents are highly liquid investments valued at cost, which approximates fair value, acquired with an original maturity of three months or less.
Accounts Receivable	Accounts Receivable
	Accounts receivable are presented net of a reserve for doubtful accounts of $4.8 million at December 31, 2014 and $5.3 million at December 31, 2013. Trade credit is extended based upon evaluations of each customer’s ability to perform its obligations, which are updated periodically. Accounts receivable reserves are determined based upon an aging of accounts and a review for collectability of specific accounts.
Inventories	Inventories
	Inventories are stated at the lower of cost (last-in, first-out (LIFO), first-in, first-out (FIFO), and average cost methods) or market, less progress payments. Costs include direct material, direct labor and applicable manufacturing and engineering overhead, and other direct costs. Most of the Company’s inventory is valued utilizing the LIFO costing methodology. Inventory of the Company’s non-U.S. operations is valued using average cost or FIFO methods.
	The Company evaluates product lines on a quarterly basis to identify inventory carrying values that exceed estimated net realizable value. In applying the lower of cost or market principle, market means current replacement cost, subject to a ceiling (market value shall not exceed net realizable value) and a floor (market shall not be less than net realizable value reduced by an allowance for a normal profit margin). The calculation of a resulting reserve, if any, is recognized as an expense in the period that the need for the reserve is identified. However, in cases where inventory at FIFO cost is lower than the LIFO carrying value, a write-down of the inventory to market may be required, subject to the ceiling and floor. It is the Company’s general policy to write-down to scrap value any inventory that is identified as obsolete and any inventory that has aged or has not moved in more than twelve months. In some instances this criterion is up to twenty-four months.
Long-Lived Assets	Long-Lived Assets
	Property, plant and equipment are recorded at cost, including capitalized interest, and includes long-lived assets acquired under capital leases. The principal method of depreciation adopted for all property placed into service after July 1, 1996 is the straight-line method. For buildings and equipment acquired prior to July 1, 1996, depreciation is computed using a combination of accelerated and straight-line methods. Property, plant and equipment associated with the Company’s Rowley titanium sponge facility in the High Performance Materials & Components segment, and the Hot-Rolling and Processing Facility (HRPF) in the Flat Rolled Products segment, are being depreciated utilizing the units of production method of depreciation, which the Company believes provides a better matching of costs and revenues. The Company periodically reviews estimates of useful life and production capacity assigned to new and in service assets. Significant enhancements, including major maintenance activities that extend the lives of property and equipment, are capitalized. Costs related to repairs and maintenance are charged to expense in the period incurred. The cost and related accumulated depreciation of property and equipment retired or disposed of are removed from the accounts and any related gains or losses are included in income.
	The Company monitors the recoverability of the carrying value of its long-lived assets. An impairment charge is recognized when an indicator of impairment occurs and the expected net undiscounted future cash flows from an asset’s use (including any proceeds from disposition) are less than the asset’s carrying value and the asset’s carrying value exceeds its fair value. Assets to be disposed of by sale are stated at the lower of their fair values or carrying amounts and depreciation is no longer recognized.
Cost in Excess of Net Assets Acquired	Cost in Excess of Net Assets Acquired
	At December 31, 2014, the Company had $780.4 million of goodwill on its consolidated balance sheet. Of the total, $653.8 million related to the High Performance Materials & Components segment and $126.6 million related to the Flat Rolled Products segment. Goodwill increased $55.0 million in 2014 from the acquisitions of Dynamic Flowform Corp. and Hanard Machine, Inc. (see Note 2) which was partially offset by a decrease of $2.5 million as a result of the impact of foreign currency translation on goodwill denominated in functional currencies other than the U.S. dollar. Goodwill is reviewed annually for impairment or more frequently if impairment indicators arise. The review for goodwill impairment requires a comparison of the fair value of each reporting unit that has goodwill associated with its operations with its carrying amount, including goodwill. If this comparison reflects impairment, then the loss would be measured as the excess of recorded goodwill over its implied fair value. Implied fair value is the excess of the fair value of the reporting unit over the fair value of all recognized and unrecognized assets and liabilities.
	Generally accepted accounting standards provide the option to qualitatively assess goodwill for impairment before completing a quantitative assessment. Under the qualitative approach, if, after assessing the totality of events or circumstances, including both macroeconomic, industry and market factors, and entity-specific factors, the Company determines it is likely (more likely than not) that the fair value of a reporting unit is greater than its carrying amount, then the quantitative impairment analysis is not required. The quantitative assessment may be performed each year for a reporting unit at the Company’s option without first performing a qualitative assessment. The Company’s quantitative assessment of goodwill for possible impairment includes estimating the fair market value of a reporting unit which has goodwill associated with its operations using discounted cash flow and multiples of cash earnings valuation techniques, plus valuation comparisons to recent public sale transactions of similar businesses, if any. These impairment assessments and valuation methods require the Company to make estimates and assumptions regarding future operating results, cash flows, changes in working capital and capital expenditures, selling prices, profitability, and the cost of capital. Many of these assumptions are determined by reference to market participants identified by the Company. Although management believes that the estimates and assumptions used were reasonable, actual results could differ from those estimates and assumptions.
	The Company performs the required annual goodwill impairment evaluations in the fourth quarter of each year. No impairments were determined to exist for the years ended December 31, 2014, 2013 or 2012. The fair values of all reporting units significantly exceeded the carrying values for the 2014 evaluation.
Environmental	Environmental
	Costs that mitigate or prevent future environmental contamination or extend the life, increase the capacity or improve the safety or efficiency of property utilized in current operations are capitalized. Other costs that relate to current operations or an existing condition caused by past operations are expensed. Environmental liabilities are recorded when the Company’s liability is probable and the costs are reasonably estimable, but generally not later than the completion of the feasibility study or the Company’s recommendation of a remedy or commitment to an appropriate plan of action. The accruals are reviewed periodically and, as investigations and remediations proceed, adjustments of the accruals are made to reflect new information as appropriate. Accruals for losses from environmental remediation obligations do not take into account the effects of inflation, and anticipated expenditures are not discounted to their present value. The accruals are not reduced by possible recoveries from insurance carriers or other third parties, but do reflect allocations among potentially responsible parties (“PRPs”) at Federal Superfund sites or similar state-managed sites after an assessment is made of the likelihood that such parties will fulfill their obligations at such sites and after appropriate cost-sharing or other agreements are entered. The measurement of environmental liabilities by the Company is based on currently available facts, present laws and regulations, and current technology. Such estimates take into consideration the Company’s prior experience in site investigation and remediation, the data concerning cleanup costs available from other companies and regulatory authorities, and the professional judgment of the Company’s environmental experts in consultation with outside environmental specialists, when necessary.
Foreign Currency Translation	Foreign Currency Translation
	Assets and liabilities of international operations are translated into U.S. dollars using year-end exchange rates, while revenues and expenses are translated at average exchange rates during the period. The resulting net translation adjustments are recorded as a component of accumulated other comprehensive income (loss) in stockholders’ equity.
Sales Recognition	Sales Recognition
	Sales are recognized when title passes or as services are rendered.
Research and Development	Research and Development
	Company funded research and development costs from continuing operations were $17.4 million in 2014, $16.1 million in 2013, and $22.3 million in 2012 and were expensed as incurred. Customer funded research and development costs were $2.7 million in 2014, $2.7 million in 2013, and $1.5 million in 2012.
Stock-based Compensation	Stock-based Compensation
	The Company accounts for stock-based compensation transactions, such as nonvested stock and performance equity awards, using fair value. Compensation expense for an award is estimated at the date of grant and is recognized over the requisite service period. Compensation expense is adjusted for equity awards that do not vest because service or performance conditions are not satisfied. However, compensation expense already recognized is not adjusted if market conditions are not met, such as the Company’s total shareholder return performance relative to a peer group under the Company’s performance equity awards
Income Taxes	Income Taxes
	The provision for, or benefit from, income taxes includes deferred taxes resulting from temporary differences in income for financial and tax purposes using the liability method. Such temporary differences result primarily from differences in the carrying value of assets and liabilities. Future realization of deferred income tax assets requires sufficient taxable income within the carryback, carryforward period available under tax law.
	The Company evaluates, on a quarterly basis whether, based on all available evidence, it is probable that the deferred income tax assets are realizable. Valuation allowances are established when it is estimated that it is more likely than not that the tax benefit of the deferred tax asset will not be realized. The evaluation includes the consideration of all available evidence, both positive and negative, regarding historical operating results including recent years with reported losses, the estimated timing of future reversals of existing taxable temporary differences, estimated future taxable income exclusive of reversing temporary differences and carryforwards, and potential tax planning strategies which may be employed to prevent an operating loss or tax credit carryforward from expiring unused.
	It is the Company’s policy to classify interest and penalties recognized on underpayment of income taxes as income tax expense.
Net Income Per Common Share	Net Income Per Common Share
	Basic and diluted net income per share are calculated by dividing the net income available to common stockholders by the weighted average number of common shares outstanding during the year. Diluted amounts assume the issuance of common stock for all potentially dilutive share equivalents outstanding. The calculations of all diluted income/loss per share figures for a period exclude the potentially dilutive effect of dilutive share equivalents if there is a net loss from continuing operations since the inclusion in the calculation of additional shares in the net loss from continuing operations per share would result in a lower per share loss and therefore be anti-dilutive.
New Accounting Pronouncements Adopted	New Accounting Pronouncements Adopted
	In January 2014, the Company adopted changes issued by the Financial Accounting Standards Board (FASB) that require an entity to net its liability for unrecognized tax positions against a net operating loss carryforward, a similar tax loss or a tax credit carryforward when settlement in this manner is available under the tax law. The adoption of these changes had no impact on the consolidated financial statements.
	In January 2014, the Company adopted changes issued by the FASB to the accounting for obligations resulting from joint and several liability arrangements. This guidance requires an entity that is joint and severally liable to measure the obligation as the sum of the amount the entity has agreed with co-obligors to pay and any additional amount it expects to pay on behalf of one or more co-obligors. Required disclosures include a description of the nature of the arrangement, how the liability arose, the relationship with co-obligors and the terms and conditions of the arrangement. The adoption of these changes had no impact on the consolidated financial statements.
	In January 2014, the Company adopted changes issued by the FASB to a parent entity’s accounting for the cumulative translation adjustment (CTA) upon derecognition of certain subsidiaries or groups of assets within a foreign entity or of an investment in a foreign entity. The amendments specify that CTA should be released into earnings when an entity ceases to have a controlling financial interest in a subsidiary or group of assets within a consolidated foreign entity and the sale or transfer results in the complete or substantially complete liquidation of the foreign entity. For sales of an equity method investment that is a foreign entity, a pro rata portion of CTA attributable to the investment would be recognized in earnings when the investment is sold. When an entity sells either a part or all of its investment in a consolidated foreign entity, CTA would be recognized in earnings only if the sale results in the parent no longer having a controlling financial interest in the foreign entity. In addition, CTA should be recognized in earnings in a business combination achieved in stages (i.e., a step acquisition). The adoption of these changes had no impact on the consolidated financial statements.
New Accounting Pronouncements Not yet Adopted	Pending Accounting Pronouncements
	In May 2014, the FASB issued changes to revenue recognition with customers. This update provides a five-step analysis of transactions to determine when and how revenue is recognized. An entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This update will be effective for the Company beginning in fiscal year 2017. This update may be applied retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying this update recognized at the date of initial application. The Company is currently evaluating the impact of the new guidance on its consolidated financial statements.
	In April 2014, the FASB issued changes to the criteria for reporting discontinued operations. Under the new criteria, a disposal of a component of an entity is required to be reported as discontinued operations only if the disposal represents a strategic shift that has, or will have, a major effect on an entity’s operations and financial results. The current criteria that there be no significant continuing involvement in the operations of the component after the disposal transaction has been removed under the new guidance. The new guidance also requires the presentation of the assets and liabilities of a disposal group that includes a discontinued operation for each comparative period and requires additional disclosures about discontinued operations, including the major line items constituting the pretax profit or loss of the discontinued operation, certain cash flow information for the discontinued operation, expanded disclosures about an entity’s significant continuing involvement in a discontinued operation, and disclosures about a disposal of an individually significant component of an entity that does not qualify for discontinued operations presentation. The provisions of the new guidance become effective for all disposals that occur for the Company beginning in fiscal year 2015. The Company does not anticipate a material impact to the consolidated financial statements upon adoption.
Asset Retirement Obligations	Asset Retirement Obligations
	The Company maintains reserves where a legal obligation exists to perform an asset retirement activity and the fair value of the liability can be reasonably estimated. These asset retirement obligations (“AROs”) include liabilities where the timing and (or) method of settlement may be conditional on a future event, that may or may not be within the control of the entity. At December 31, 2014, the Company had recognized AROs of $25.4 million related to landfill closures, decommissioning costs, facility leases and conditional AROs associated with manufacturing activities using what may be characterized as potentially hazardous materials. The 2013 sale of the tungsten materials business included an indemnification to the buyer for conditional ARO costs of up to $13 million for a five year period. The Company recorded a $9.4 million charge in 2013 to increase recorded reserves to $13 million for these retained liabilities, which was reported as part of the gain on sale of the tungsten materials business. In addition, as part of facility closures in 2013, $4.2 million in decommissioning AROs were reported in continuing operations (see Note 16) on the 2013 consolidated statement of operations.
	Estimates of AROs are evaluated annually in the fourth quarter, or more frequently if material new information becomes known. Accounting for asset retirement obligations requires significant estimation and in certain cases, the Company has determined that an ARO exists, but the amount of the obligation is not reasonably estimable. The Company may determine that additional AROs are required to be recognized as new information becomes available.
Derivative Financial Instruments and Hedging	Derivative Financial Instruments and Hedging
	As part of its risk management strategy, the Company, from time-to-time, utilizes derivative financial instruments to manage its exposure to changes in raw material prices, energy costs, foreign currencies, and interest rates. In accordance with applicable accounting standards, the Company accounts for most of these contracts as hedges. In general, hedge effectiveness is determined by examining the relationship between offsetting changes in fair value or cash flows attributable to the item being hedged, and the financial instrument being used for the hedge. Effectiveness is measured utilizing regression analysis and other techniques to determine whether the change in the fair market value or cash flows of the derivative exceeds the change in fair value or cash flow of the hedged item. Calculated ineffectiveness, if any, is immediately recognized on the statement of operations.
	The Company sometimes uses futures and swap contracts to manage exposure to changes in prices for forecasted purchases of raw materials, such as nickel, and energy costs, such as electricity and natural gas. Generally under these contracts, which are accounted for as cash flow hedges, the price of the item being hedged is fixed at the time that the contract is entered into and the Company is obligated to make or receive a payment equal to the net change between this fixed price and the market price at the date the contract matures.
	The majority of ATI’s products are sold utilizing raw material surcharges and index mechanisms. However, as of December 31, 2014, the Company had entered into financial hedging arrangements primarily at the request of its customers, related to firm orders, for an aggregate notional amount of approximately 15% of the Company’s estimated annual nickel requirements. These nickel hedges extend to 2020.
	At December 31, 2014, the outstanding financial derivatives used to hedge the Company’s exposure to energy cost volatility included natural gas cost hedges for approximately 80% of its annual forecasted domestic requirements for 2015, 70% for 2016, and approximately 40% for 2017. There were no material electricity hedge contracts outstanding as of December 31, 2014.
	While the majority of the Company’s direct export sales are transacted in U.S. dollars, foreign currency exchange contracts are used, from time-to-time, to limit transactional exposure to changes in currency exchange rates for those transactions denominated in a non-U.S. currency. The Company sometimes purchases foreign currency forward contracts that permit it to sell specified amounts of foreign currencies expected to be received from its export sales for pre-established U.S. dollar amounts at specified dates. The forward contracts are denominated in the same foreign currencies in which export sales are denominated. These contracts are designated as hedges of the variability in cash flows of a portion of the forecasted future export sales transactions which otherwise would expose the Company to foreign currency risk, primarily euros. At December 31, 2014, the Company held euro forward sales contracts designated as hedges with a notional value of approximately 388 million euros with maturity dates through June 2018, including approximately 175 million euros with maturities in 2015. In addition, the Company may also designate cash balances held in foreign currencies as hedges of forecasted foreign currency transactions.
	The Company may enter into derivative interest rate contracts to maintain a reasonable balance between fixed- and floating-rate debt. There were no unsettled derivative financial instruments related to debt balances for the periods presented.
	There are no credit risk-related contingent features in the Company’s derivative contracts, and the contracts contained no provisions under which the Company has posted, or would be required to post, collateral. The counterparties to the Company’s derivative contracts were substantial and creditworthy commercial banks that are recognized market makers. The Company controls its credit exposure by diversifying across multiple counterparties and by monitoring credit ratings and credit default swap spreads of its counterparties. The Company also enters into master netting agreements with counterparties when possible.
	The fair values of the Company’s derivative financial instruments are presented below, representing the gross amounts recognized which are not offset by counterpart or by type of item hedged. All fair values for these derivatives were measured using Level 2 information as defined by the accounting standard hierarchy, which includes quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs derived principally from or corroborated by observable market data.
Pension Plans and Other Postretirement Benefits	Pension Plans and Other Postretirement Benefits
	The Company has defined benefit pension plans or defined contribution retirement plans covering substantially all employees. Benefits under the defined benefit pension plans are generally based on years of service and/or final average pay. The Company funds the U.S. pension plans in accordance with the Employee Retirement Income Security Act of 1974, as amended, and the Internal Revenue Code (“Code”).
	The Company also sponsors several postretirement plans covering certain salaried and hourly employees. The plans provide health care and life insurance benefits for eligible retirees. In most retiree health care plans, Company contributions towards premiums are capped based on the cost as of a certain date, thereby creating a defined contribution. For the non-collectively bargained plans, the Company maintains the right to amend or terminate the plans at its discretion.

Discontinued_Operations_Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
Discontinued operations, income from operations and net assets	The following table presents summarized results for these discontinued operations (in millions):
		2014				2013		2012
	Sales	$	14.9			$	268.2	$	364.6
	Income (loss) before income taxes	$	(0.9	)		$	414.2	$	11.7
	Net liabilities of discontinued operations were $1.3 million at December 31, 2014 and were net assets of $4.2 million at December 31, 2013 and were reported as follows on the consolidated balance sheet (in millions):
		2014			2013
	Prepaid expenses and other current assets	$	0.4		$	6.1
	Other assets	1.4			3.7
	Total Assets	1.8			9.8
	Accrued liabilities	2.5			4.9
	Other long-term liabilities	0.6			0.7
	Total Liabilities	3.1			5.6
	Net Assets (Liabilities)	$	(1.3	)	$	4.2

Inventories_Tables

Inventories (Tables)	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventories at December 31, 2014 and 2013 were as follows (in millions):
		2014			2013
	Raw materials and supplies	$	249.3		$	277.6
	Work-in-process	1,184.10			984.9
	Finished goods	172.2			162.1
	Total inventories at current cost	1,605.60			1,424.60
	Adjustment from current cost to LIFO cost basis	4.8			29.4
	Inventory valuation reserves	(68.8		)	(84.3		)
	Progress payments	(68.8		)	(47.6		)
	Total inventories, net	$	1,472.80		$	1,322.10

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Schedule of property plant and equipment, net	Property, plant and equipment at December 31, 2014 and 2013 was as follows:
	(In millions)	2014			2013
	Land	$	30.2		$	30.2
	Buildings	1,048.90			1,019.10
	Equipment and leasehold improvements	3,702.50			3,526.00
		4,781.60			4,575.30
	Accumulated depreciation and amortization	(1,819.8		)	(1,701.2		)
	Total property, plant and equipment, net	$	2,961.80		$	2,874.10
Schedule depreciation and amortization	Depreciation and amortization from continuing operations for the years ended December 31, 2014, 2013 and 2012 was as follows:
	(In millions)	2014			2013			2012
	Depreciation of property, plant and equipment	$	146.7		$	156.8		$	157
	Software and other amortization	29.9			23.8			24.4
	Total depreciation and amortization	$	176.6		$	180.6		$	181.4

Asset_Retirement_Obligations_T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]
Schedule of changes in asset retirement obligations	Changes in asset retirement obligations for the years ended December 31, 2014 and 2013 were as follows:
	(In millions)	2014			2013
	Balance at beginning of year	$	27.7		$	13
	Accretion expense	0.9			1.1
	Payments	(2.2		)	(0.8		)
	Revision of estimates	(1.0		)	13.8
	Liabilities incurred	—			0.6
	Balance at end of year	$	25.4		$	27.7

Supplemental_Financial_Stateme1

Supplemental Financial Statement Information (Tables)	12 Months Ended
	Dec. 31, 2014
Additional Financial Information Disclosure [Abstract]
Schedule of cash and cash equivalents	Cash and cash equivalents at December 31, 2014 and 2013 were as follows:
	(In millions)	2014				2013
	Cash	$	267.7			$	1,025.20
	Other short-term investments	1.8				1.6
	Total cash and cash equivalents	$	269.5			$	1,026.80
Schedule of acquired finite-lived intangible assets by major class	Other intangible assets, which are included in Other assets on the accompanying consolidated balance sheets as of December 31, 2014 and 2013 were as follows:
				31-Dec-14								31-Dec-13
	(in millions)	Weighted Average Useful life		Gross				Accumulated				Gross		Accumulated
		(years)		carrying				amortization				carrying		amortization
				amount								amount
	Technology	21		$	91.4			$	(14.2	)		$	74	$	(9.9	)
	Customer relationships	24		35.7				(4.7		)		31		(3.3		)
	Trademarks	15		64.6				(4.3		)		—		—
	Total amortizable intangible assets			191.7				(23.2		)		105		(13.2		)
	Indefinite-lived trademarks			—				—				61		—
	Total intangible assets			$	191.7			$	(23.2	)		$	166	$	(13.2	)
Schedule of other non-operating income (expense)	Other income (expense) from continuing operations for the years ended December 31, 2014, 2013, and 2012 was as follows:
	(In millions)	2014				2013				2012
	Rent and royalty income	$	4			$	0.9			$	0.7
	Net gains (losses) on property and investments	0.1				0.7				(0.7		)
	Other	—				0.1				—
	Total other income, net	$	4.1			$	1.7			$	—

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of debt	Debt at December 31, 2014 and 2013 was as follows:
	(In millions)		2014		2013
	Allegheny Technologies $500 million 5.875% Senior Notes due 2023 (a)		$	500	$	500
	Allegheny Technologies $500 million 5.95% Senior Notes due 2021		500		500
	Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014		—		402.5
	Allegheny Technologies $350 million 9.375% Senior Notes due 2019		350		350
	Allegheny Ludlum 6.95% Debentures due 2025		150		150
	Ladish Series B 6.14% Notes due 2016 (b)		11.9		18.2
	Ladish Series C 6.41% Notes due 2015 (c)		10.3		21.1
	Domestic Bank Group $400 million unsecured credit agreement		—		—
	Foreign credit agreements		—		—
	Industrial revenue bonds, due through 2020, and other		4.7		5.5
	Total short-term and long-term debt		1,526.90		1,947.30
	Short-term debt and current portion of long-term debt		17.8		419.9
	Total long-term debt		$	1,509.10	$	1,527.40
	(a)	Bearing interest at 6.125% effective August 15, 2014.
	(b)	Includes fair value adjustments of $0.4 million and $1.0 million at December 31, 2014 and December 31, 2013, respectively.
	(c)	Includes fair value adjustments of $0.3 million and $1.1 million at December 31, 2014 and December 31, 2013, respectively.

Derivative_Financial_Instrumen1

Derivative Financial Instruments and Hedging (Tables)	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of derivative instruments
	(In millions)				December 31,				December 31,
	Asset derivatives		Balance sheet location		2014				2013
	Derivatives designated as hedging instruments:
	Foreign exchange contracts		Prepaid expenses and other current assets		$	23.6			$	0.3
	Nickel and other raw material contracts		Prepaid expenses and other current assets		1.1				0.1
	Natural gas contracts		Prepaid expenses and other current assets		—				2.5
	Foreign exchange contracts		Other assets		28.3				—
	Natural gas contracts		Other assets		—				1
	Nickel and other raw material contracts		Other assets		0.5				0.4
	Total derivatives designated as hedging instruments:				53.5				4.3
	Derivatives not designated as hedging instruments:
	Foreign exchange contracts		Prepaid expenses and other current assets		6.4				—
	Total derivatives not designated as hedging instruments:				6.4				—
	Total asset derivatives				$	59.9			$	4.3
	Liability derivatives		Balance sheet location
	Derivatives designated as hedging instruments:
	Natural gas contracts		Accrued liabilities		$	10.2			$	0.4
	Foreign exchange contracts		Accrued liabilities		—				7.8
	Nickel and other raw material contracts		Accrued liabilities		5.8				4.5
	Electricity contracts		Accrued liabilities		0.1				0.5
	Foreign exchange contracts		Other long-term liabilities		—				5.4
	Natural gas contracts		Other long-term liabilities		7.9				—
	Nickel and other raw material contracts		Other long-term liabilities		3				1.3
	Total liability derivatives				$	27			$	19.9
	Derivatives not designated as hedging instruments:
	Foreign exchange contracts		Accrued liabilities		—				1.7
	Total derivatives not designated as hedging instruments:				—				1.7
	Total liability derivatives				$	27			$	21.6
Schedule of derivative instruments gain (loss)	Activity with regard to derivatives designated as cash flow hedges for the year ended December 31, 2014 were as follows (in millions):
	Derivatives in Cash Flow		Amount of Gain (Loss)								Amount of Gain (Loss)						Amount of Gain (Loss)
	Hedging Relationships		Recognized in OCI on								Reclassified from						Recognized in Income
			Derivatives								Accumulated OCI						on Derivatives  (Ineffective
			(Effective Portion)								into Income						Portion and Amount
											(Effective Portion) (a)						Excluded from
																	Effectiveness Testing) (b)
			2014				2013				2014			2013			2014		2013
	Nickel and other raw material contracts		$	(1.6	)		$	(8.4	)		$	(0.6	)	$	(5.4	)	$	—	$	—
	Natural gas contracts		(10.9		)		2.1				2.1			(2.3		)	—		—
	Electricity contracts		0.5				(0.1		)		0.4			(0.2		)	—		—
	Foreign exchange contracts		40.1				(9.1		)		0.3			(0.7		)	—		—
	Total		$	28.1			$	(15.5	)		$	2.2		$	(8.6	)	$	—	$	—
	(a)	The gains (losses) reclassified from accumulated OCI into income related to the effective portion of the derivatives are presented in cost of sales.
	(b)	The gains (losses) recognized in income on derivatives related to the ineffective portion and the amount excluded from effectiveness testing are presented in selling and administrative expenses.
Schedule of derivatives not designated as hedging instruments, gain (loss)	Derivatives that are not designated as hedging instruments were as follows:
	(In millions)		Amount of Gain (Loss) Recognized
			in Income on Derivatives
	Derivatives Not Designated as Hedging Instruments		2014				2013
	Foreign exchange contracts		$	5.2			$	(0.3	)

Recovered_Sheet1

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Schedule of financial instrument fair value	The estimated fair value of financial instruments at December 31, 2014 was as follows:
				Fair Value Measurements at Reporting Date Using
	(In millions)	Total		Total		Quoted Prices in		Significant
		Carrying		Estimated		Active Markets for		Observable
		Amount		Fair Value		Identical Assets		Inputs
						(Level 1)		(Level 2)
	Cash and cash equivalents	$	269.5	$	269.5	$	269.5	$	—
	Derivative financial instruments:
	Assets	59.9		59.9		—		59.9
	Liabilities	27		27		—		27
	Debt	1,526.90		1,616.00		1,589.10		26.9
	The estimated fair value of financial instruments at December 31, 2013 was as follows:
				Fair Value Measurements at Reporting Date Using
	(In millions)	Total		Total		Quoted Prices in		Significant
		Carrying		Estimated		Active Markets for		Observable
		Amount		Fair Value		Identical Assets		Inputs
						(Level 1)		(Level 2)
	Cash and cash equivalents	$	1,026.80	$	1,026.80	$	1,026.80	$	—
	Derivative financial instruments:
	Assets	4.3		4.3		—		4.3
	Liabilities	21.6		21.6		—		21.6
	Debt	1,947.30		2,072.60		2,027.80		44.8

Pension_Plans_and_Other_Postre1

Pension Plans and Other Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Schedule of defined benefit plans	The components of pension and other postretirement benefit expense for the Company’s defined benefit plans included the following:
			Pension Benefits											Other Postretirement Benefits
	(In millions)		2014				2013				2012			2014				2013			2012
	Service cost—benefits earned during the year		$	29.4			$	39			$	35		$	2.9			$	3.2		$	3.1
	Interest cost on benefits earned in prior years		133.6				122.8				132.4			24				22.4			26.1
	Expected return on plan assets		(184.2		)		(176.0		)		(181.4		)	(0.3		)		(0.5		)	(0.8		)
	Amortization of prior service cost (credit)		2.3				3				6.4			(3.0		)		(18.2		)	(18.2		)
	Amortization of net actuarial loss		74				111.8				105.2			14.1				17.2			14.6
	Curtailment (gain) loss		0.5				—				—			(25.5		)		—			—
	Termination benefits		0.3				4.8				—			—				1.3			—
	Total retirement benefit expense		$	55.9			$	105.4			$	97.6		$	12.2			$	25.4		$	24.8
Schedule of assumptions used	Actuarial assumptions used to develop the components of defined benefit pension expense and other postretirement benefit expense were as follows:
			Pension Benefits									Other Postretirement Benefits
			2014			2013			2012			2014		2013			2012
	Discount rate (a)		5.15	%		4.25 - 4.95%			5	%		5.15	%	4.25	%		5	%
	Rate of increase in future compensation levels		3.0 - 3.50%			3.0 - 3.50%			3.0 - 4.50%			—		—			—
	Expected long-term rate of return on assets		8.25	%		8.25	%		8.5	%		8.3	%	8.3	%		8.3	%
	(a)	Pension expense for 2013 was initially measured at a 4.25% discount rate. The U.S. Plan was remeasured using a 4.95% discount rate as of October 31, 2013, following the sale of the tungsten materials business.
Schedule of assumptions used for year end valuation	Actuarial assumptions used for the valuation of defined benefit pension and other postretirement benefit obligations at the end of the respective periods were as follows:
			Pension Benefits						Other Postretirement Benefits
			2014			2013			2014			2013
	Discount rate		4.25	%		5.15	%		4.1	%		5.15	%
	Rate of increase in future compensation levels		3.0 - 3.5%			3.0 - 3.5%			—			—
Schedule of changes in projected benefit obligations	A reconciliation of the funded status for the Company’s defined benefit pension and other postretirement benefit plans at December 31, 2014 and 2013 was as follows:
			Pension Benefits								Other Postretirement Benefits
	(In millions)		2014				2013				2014			2013
	Change in benefit obligations:
	Benefit obligation at beginning of year		$	2,698.20			$	2,952.00			$	506.7		$	574.3
	Service cost		29.4				39				2.9			3.2
	Interest cost		133.6				122.8				24			22.4
	Benefits paid		(269.9		)		(195.6		)		(54.3		)	(52.9		)
	Subsidy paid		—				—				1			1.2
	Participant contributions		0.3				0.1				—			—
	Effect of currency rates		(4.9		)		0.8				—			—
	Net actuarial (gains) losses – discount rate change		288.5				(280.4		)		39.5			(36.9		)
	– other		78.4				54.7				(19.5		)	(5.9		)
	Plan curtailments		—				—				(7.2		)	—
	Plan settlements		—				—				(27.0		)	—
	Special termination benefits		0.3				4.8				—			1.3
	Benefit obligation at end of year		$	2,953.90			$	2,698.20			$	466.1		$	506.7
Schedule of changes in fair value of plan assets
	Change in plan assets:
	Fair value of plan assets at beginning of year		$	2,329.80			$	2,220.00			$	4		$	6.3
	Actual returns on plan assets and plan expenses		136.8				293.8				(0.9		)	(0.9		)
	Employer contributions		11.5				10.7				—			—
	Participant contributions		0.3				0.1				—			—
	Effect of currency rates		(4.1		)		0.8				—			—
	Benefits paid		(269.9		)		(195.6		)		(0.2		)	(1.4		)
	Fair value of plan assets at end of year		$	2,204.40			$	2,329.80			$	2.9		$	4
Schedule of amounts recognized in balance sheet
	Amounts recognized in the consolidated balance sheet:
	Noncurrent assets		$	—			$	5.1			$	—		$	—
	Current liabilities		(10.2		)		(5.3		)		(47.3		)	(60.3		)
	Noncurrent liabilities		(739.3		)		(368.2		)		(415.8		)	(442.4		)
	Total amount recognized		$	(749.5	)		$	(368.4	)		$	(463.1	)	$	(502.7	)
Schedule of amounts recognized in other comprehensive income	Changes to accumulated other comprehensive loss related to pension and other postretirement benefit plans in 2014 and 2013 were as follows:
			Pension Benefits								Other Postretirement Benefits
	(In millions)		2014				2013				2014			2013
	Beginning of year accumulated other comprehensive loss		$	(1,016.4	)		$	(1,474.7	)		$	(151.5	)	$	(191.9	)
	Amortization of net actuarial loss		74				111.8				14.1			17.2
	Amortization of prior service cost (credit)		2.3				3				(3.0		)	(18.2		)
	Remeasurements		(412.0		)		343.5				(12.5		)	41.4
	End of year accumulated other comprehensive loss		$	(1,352.1	)		$	(1,016.4	)		$	(152.9	)	$	(151.5	)
	Net change in accumulated other comprehensive loss		$	(335.7	)		$	458.3			$	(1.4	)	$	40.4
Schedule of net periodic benefit cost not yet recognized	Amounts included in accumulated other comprehensive loss at December 31, 2014 and 2013 were as follows:
			Pension Benefits								Other Postretirement Benefits
	(In millions)		2014				2013				2014			2013
	Prior service (cost) credit		$	(4.9	)		$	(7.7	)		$	(11.8	)	$	(8.7	)
	Net actuarial loss		(1,347.2		)		(1,008.7		)		(141.1		)	(142.8		)
	Accumulated other comprehensive loss		(1,352.1		)		(1,016.4		)		(152.9		)	(151.5		)
	Deferred tax effect		514.7				390.7				58.8			58.3
	Accumulated other comprehensive loss, net of tax		$	(837.4	)		$	(625.7	)		$	(94.1	)	$	(93.2	)
Schedule of amounts in accumulated other comprehensive income to be recognized	Amounts in accumulated other comprehensive loss that are expected to be recognized as components of net periodic benefit cost in 2015 are:
	(In millions)		Pension				Other				Total
			Benefits				Postretirement
							Benefits
	Amortization of prior service cost		$	1.3			$	4.9			$	6.2
	Amortization of net actuarial loss		60.5				14.7				75.2
	Amortization of accumulated other comprehensive loss		$	61.8			$	19.6			$	81.4
Schedule of accumulated benefit obligations in excess of fair value of plan assets	Additional information for pension plans with accumulated benefit obligations in excess of plan assets:
			Pension Benefits
	(In millions)		2014				2013
	Projected benefit obligation		$	2,953.90			$	2,619.60
	Accumulated benefit obligation		$	2,917.30			$	2,545.40
	Fair value of plan assets		$	2,204.40			$	2,246.10
Schedule of expected benefit payments	The following table summarizes expected benefit payments from the Company’s various pension and other postretirement benefit defined benefit plans through 2024, and also includes estimated Medicare Part D subsidies projected to be received during this period based on currently available information.
	(In millions)		Pension				Other				Medicare Part
			Benefits				Postretirement				D Subsidy
							Benefits
	2015		$	195.4			$	51.3			$	1.1
	2016		195.4				44.7				1.1
	2017		195.1				42.6				1.1
	2018		195.4				40.4				1.1
	2019		195.1				38.3				1.1
	2020 - 2024		967.7				154.7				4.7
Schedule of effect of one-percentage-point change in assumed health care cost trend rates	A one percentage point change in assumed health care cost trend rates would have the following effects:
	(In millions)		One				One
			Percentage				Percentage
			Point				Point
			Increase				Decrease
	Effect on total of service and interest cost components for the year ended December 31, 2014		$	0.5			$	(0.5	)
	Effect on other postretirement benefit obligation at December 31, 2014		$	11.1			$	(9.7	)
Schedule of allocation of plan assets	The fair values of the Company’s pension plan assets at December 31, 2014 by asset category and by the level of inputs used to determine fair value, were as follows:
	(In millions)						Quoted Prices in				Significant			Significant
							Active Markets for				Observable Inputs			Unobservable Inputs
							Identical Assets
	Asset category		Total				(Level 1)				(Level 2)			(Level 3)
	Equity securities:
	ATI common stock		$	102.7			$	102.7			$	—		$	—
	Other U.S. equities (a)		673.8				306.1				367.7			—
	International equities (b)		238.2				—				238.2			—
	Global debt securities and cash: (c)
	Fixed income and cash equivalents		383.5				0.7				373.9			8.9
	Floating rate		392.3				—				—			392.3
	Private equity		134.7				—				—			134.7
	Hedge funds		122.6				—				—			122.6
	Real estate and other		156.6				—				5.4			151.2
	Total assets		$	2,204.40			$	409.5			$	985.2		$	809.7
	(a)	Includes investments in commingled funds that invest in U.S. equity securities, comprised of approximately 90% large-cap U.S. companies and 10% small-cap U.S. companies.
	(b)	Includes investments in commingled funds that invest in non-U.S. equity securities, comprised of approximately 90% developed countries and 10% emerging market economies.
	(c)	Global debt securities include both fixed interest rate and floating interest rate instruments. These are comprised of actively managed investments which include U.S. government and U.S. government agency securities, foreign government securities, corporate bonds, mortgage-backed securities and other debt securities, and include both investment grade and non-investment grade debt, public and private debt, and secured and unsecured debt investments. To mitigate risk, investment managers have limitations regarding the amount of investment in particular securities and the credit quality of such investments.
	The fair values of the Company’s pension plan assets at December 31, 2013 by asset category and by the level of inputs used to determine fair value, were as follows:
	(In millions)						Quoted Prices in				Significant			Significant
							Active Markets for				Observable Inputs			Unobservable Inputs
							Identical Assets
	Asset category		Total				(Level 1)				(Level 2)			(Level 3)
	Equity securities:
	ATI common stock		$	105.3			$	105.3			$	—		$	—
	Other U.S. equities (a)		746				257.2				488.8			—
	International equities (b)		311				—				311			—
	Global securities and cash: (c)
	Fixed income and cash equivalents		508				—				507.2			0.8
	Floating rate		294.5				—				—			294.5
	Private equity		94.5				—				—			94.5
	Hedge funds		139.7				—				—			139.7
	Real estate and other		130.8				—				5			125.8
	Total assets		$	2,329.80			$	362.5			$	1,312.00		$	655.3
	(a)	Includes investments in commingled funds that invest in U.S. equity securities, comprised of approximately 90% large-cap U.S. companies and 10% small-cap U.S. companies.
	(b)	Includes investments in commingled funds that invest in non-U.S. equity securities, comprised of approximately 80% developed countries and 20% emerging market economies.
	(c)	Global debt securities include both fixed interest rate and floating interest rate instruments. These are comprised of actively managed investments which include U.S. government and U.S. government agency securities, foreign government securities, corporate bonds, mortgage-backed securities and other debt securities, and include both investment grade and non-investment grade debt, public and private debt, and secured and unsecured debt investments. To mitigate risk, investment managers have limitations regarding the amount of investment in particular securities and the credit quality of such investments.
Changes in fair value of level 3 plan investments	Changes in the fair value of Level 3 pension plan assets for the year ended December 31, 2014 were as follows:
	(In millions)		January 1,				Net Realized				Net Purchases,			Net Transfers				December 31,
			2014 Balance				and Unrealized				Issuances and			Into (Out Of)				2014 Balance
							Gains (Losses)				Settlements			Level 3
	Global debt securities and cash:
	Fixed income and cash equivalents		$	0.8			$	0.1			$	8		$	—			$	8.9
	Floating rate debt		294.5				4.6				93.2			—				392.3
	Private equity		94.5				19.1				21.1			—				134.7
	Hedge funds		139.7				5.9				(23.0		)	—				122.6
	Real estate and other		125.8				13.7				11.7			—				151.2
	Total		$	655.3			$	43.4			$	111		$	—			$	809.7
	Changes in the fair value of Level 3 pension plan assets for the year ended December 31, 2013 were as follows:
	(In millions)		January 1,				Net Realized				Net Purchases,			Net Transfers				December 31,
			2013 Balance				and Unrealized				Issuances and			Into (Out Of)				2013 Balance
							Gains (Losses)				Settlements			Level 3
	Global debt securities and cash:
	Fixed income and cash equivalents		$	1.4			$	0.1			$	(0.7	)	$	—			$	0.8
	Floating rate debt		—				5.4				289.1			—				294.5
	Private equity		85.5				3.9				5.1			—				94.5
	Hedge funds		148.9				13.8				(23.0		)	—				139.7
	Real estate and other		104.4				16.4				5			—				125.8
	Total		$	340.2			$	39.6			$	275.5		$	—			$	655.3
Schedule of target asset allocations for pension plans	The target asset allocations for pension plans for 2015, by major investment category, are:
	Asset category		Target asset allocation range
	Equity securities:
	U. S. equities		18% - 40%
	International equities		7% - 17%
	Global debt securities and cash		35% - 48%
	Private equity*		0% - 10%
	Hedge funds*		0% - 10%
	Real estate and other*		0% - 10%
	* Have a combined target allocation of 18% and a 20% limit.
Schedule of multiemployer plans	The Company’s participation in multiemployer plans for the years ended December 31, 2014, 2013 and 2012 is reported in the following table. The Company’s contributions to the Steelworkers Western Independent Shops Pension Plan exceed 5% of this plan’s total contributions for the plan year ended September 30, 2013, which is the most recent information available from the Plan Administrator.
					Pension				FIP / RP Status		in millions												Expiration Dates
					Protection Act				Pending /														of Collective
			EIN / Pension		Zone Status (1)				Implemented (2)		Company Contributions										Surcharge		Bargaining
	Pension Fund		Plan Number		2014		2013				2014			2013				2012			Imposed (3)		Agreements
	Steelworkers Western Independent Shops Pension Plan		90-0169564		Green		Red		N/A		$	1.1		$	1			$	1.3		No		6/30/15
			/ 001
	Boilermakers-Blacksmiths National Pension Trust		48-6168020		Yellow		Yellow		Yes		2			2.2				2.4			No		9/30/18
			/ 001
	IAM National Pension Fund		51-6031295		Green		Green		N/A		1.6			1.8				1.9			No		Various between 2018-2019 (4)
			/ 002
	Total contributions										$	4.7		$	5			$	5.6
	-1	The most recent Pension Protection Act Zone Status available for ATI’s fiscal years 2014 and 2013 is for plan years ending in calendar years 2013 and 2012, respectively. The zone status is based on information provided to ATI and other participating employers by each plan and is certified by the plan’s actuary. A plan in the “red” zone had been determined to be in “critical status”, based on criteria established by the Code, and is generally less than 65% funded. A plan in the “yellow” zone has been determined to be in “endangered status”, based on criteria established under the Code, and is generally less than 80% funded. A plan in the “green” zone has been determined to be neither in “critical status” nor in “endangered status”, and is generally at least 80% funded.
	-2	The “FIP / RP status Pending / Implemented” column indicates whether a Funding Improvement Plan, as required under the Code by plans in the “yellow” zone, or a Rehabilitation Plan, as required under the Code to be adopted by plans in the “red” zone, is pending or has been implemented as of the end of the plan year that ended in 2014.
	-3	The “Surcharge Imposed” column indicates whether ATI’s contribution rate for 2014 included an amount in addition to the contribution rate specified in the applicable collective bargaining agreement, as imposed by a plan in “critical status”, in accordance with the requirements of the Code.
	-4	The Company is party to five separate bargaining agreements that require contributions to this plan. Expiration dates of these collective bargaining agreements range between February 25, 2018 and July 14, 2019.

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Schedule of accumulated other comprehensive income (loss)	The changes in accumulated other comprehensive income (loss) (AOCI) by component, net of tax, for the fiscal years ended December 31, 2014 and 2013 were as follows (in millions):
		Post-				Currency				Unrealized			Derivatives			Total
		retirement				translation				holding gains
		benefit plans				adjustment				on securities
	Attributable to ATI:
	Balance, December 31, 2012	$	(1,030.0	)		$	3.4			$	(0.1	)	$	(2.7	)	$	(1,029.4	)
	OCI before reclassifications		241.1				10.4				0.1			(15.5	)	236.1
	Amounts reclassified from AOCI	(a)	70			(b)	1.5			(c)	—		(d)	8.6		80.1
	Net current-period OCI		311.1				11.9				0.1			(6.9	)	316.2
	Balance, December 31, 2013		(718.9	)			15.3				—			(9.6	)	(713.2		)
	OCI before reclassifications		(266.4	)			(32.0	)			—			28.1		$	(270.3	)
	Amounts reclassified from AOCI	(a)	53.8				0.5			(c)	—		(d)	(2.2	)	52.1
	Net current-period OCI		(212.6	)			(31.5	)			—			25.9		(218.2		)
	Balance, December 31, 2014	$	(931.5	)		$	(16.2	)		$	—		$	16.3		$	(931.4	)
	Attributable to noncontrolling interests:
	Balance, December 31, 2012	$	—			$	23.7			$	—		$	—		$	23.7
	OCI before reclassifications		—				3.4				—			—		3.4
	Amounts reclassified from AOCI		—			(c)	—				—			—		—
	Net current-period OCI		—				3.4				—			—		3.4
	Balance, December 31, 2013		—				27.1				—			—		27.1
	OCI before reclassifications		—				(2.1	)			—			—		(2.1		)
	Amounts reclassified from AOCI		—			(c)	—				—			—		—
	Net current-period OCI		—				(2.1	)			—			—		(2.1		)
	Balance, December 31, 2014	$	—			$	25			$	—		$	—		$	25
	(a)	Amounts were included in net periodic benefit cost for pension and other postretirement benefit plans (see Note 11).
	(b)	Amount was included in discontinued operations as part of the gain on sale of the tungsten materials business (see Note 3).
	(c)	No amounts were reclassified to earnings.
	(d)	Amounts were included in cost of goods sold in the period or periods the hedged item affects earnings (see Note 9).
Reclassification out of accumulated other comprehensive income	Reclassifications out of AOCI for the fiscal years ended December 31, 2014 and 2013 were as follows:
			Amount reclassified from AOCI (d)
			Fiscal year ended
	Details about AOCI Components		31-Dec-14						31-Dec-13				Affected line item in the
	(In millions)												consolidated statement of operations
	Postretirement benefit plans
	Prior service credit		$	0.7			(a)		$	15.2		(a)
	Actuarial losses		(88.1		)		(a)		(129.0		)	(a)
			(87.4		)		(d)		(113.8		)	(d)	Total before tax
			(33.6		)				(43.8		)		Tax provision (benefit)
			$	(53.8	)				$	(70.0	)		Net of tax
	Currency translation adjustment		$	(0.5	)		(b) , (d)		$	(1.5	)	(b) , (d)
	Derivatives
	Nickel and other raw material contracts		$	(1.0	)		(c)		$	(8.8	)	(c)
	Natural gas contracts		3.4				(c)		(3.8		)	(c)
	Electricity contracts		0.7				(c)		(0.3		)	(c)
	Foreign exchange contracts		0.5				(c)		(1.1		)	(c)
			3.6				(d)		(14.0		)	(d)	Total before tax
			1.4						(5.4		)		Tax provision (benefit)
			$	2.2					$	(8.6	)		Net of tax
	(a)	Amounts are included in the computation of pension and other postretirement benefit expense, which is reported in both cost of goods sold and selling and administrative expenses. For additional information, see Note 11.
	(b)	Amount in 2014 is included in other income, net, and amount in 2013 is included in discontinued operations as part of the gain on sale of the tungsten materials business (see Note 3).
	(c)	Amounts are included in cost of goods sold in the period or periods the hedged item affects earnings. For additional information, see Note 9.
	(d)	For pretax items, positive amounts are income and negative amounts are expense in terms of the impact to net income. Tax effects are presented in conformity with ATI’s presentation in the consolidated statements of operations.

Stockholders_Equity_Stockholde

Stockholders' Equity Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Nonvested stock rollforward	Activity under the Company’s nonvested stock awards for the years ended December 31, 2014, 2013, and 2012 was as follows:
	(Shares in thousands, $ in millions)	2014					2013					2012
		Number of		Weighted			Number of		Weighted			Number of		Weighted
		shares		Average			shares		Average Grant			shares		Average Grant
				Grant Date					Date Fair					Date Fair
				Fair Value					Value					Value
	Nonvested, beginning of year	927		$	36.9		727		$	38.6		677		$	36.4
	Granted	675		20.3			576		16.4			394		16.4
	Vested	(18	)	(1.0		)	(333	)	(16.4		)	(343	)	(14.1		)
	Forfeited	(208	)	(8.4		)	(43	)	(1.7		)	(1	)	(0.1		)
	Nonvested, end of year	1,376		$	47.8		927		$	36.9		727		$	38.6
Tsr/Tsrp Award Performance	The estimated fair value of each performance equity award, the projected shares to be awarded and future compensation expense to be recognized for these awards, including actual and estimated forfeitures, was as follows:
	(Shares in thousands, $ in millions)
	TSR / TSRP Award Performance Period	Award			December 31, 2014			Minimum		Target		Maximum
		Fair Value			Unrecognized			Shares		Shares		Shares
					Compensation
					Expense
	2012 - 2014	$	8.8		$	—		—		186		373
	2013 - 2015	$	11		3.7			—		309		618
	2014 - 2016	$	9.9		6.6			—		294		589
	Total				$	10.3		—		789		1,580

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Schedule income tax provision (benefit)	The income tax provision (benefit) was as follows:
	(In millions)	2014			2013			2012
	Continuing operations:
	Current:
	Federal	$	(47.9	)	$	(127.5	)	$	82.3
	State	(4.0		)	(10.2		)	8.7
	Foreign	9.8			7.9			9
	Total	(42.1		)	(129.8		)	100
	Deferred:
	Federal	34.1			62.7			(27.6		)
	State	(0.2		)	4.6			0.1
	Foreign	(0.5		)	(1.1		)	(0.1		)
	Total	33.4			66.2			(27.6		)
	Income tax provision (benefit) from continuing operations	$	(8.7	)	$	(63.6	)	$	72.4
	Income tax provision (benefit) from discontinued operations	$	(0.3	)	$	161.4		$	3.8
	Total company income tax provision (benefit)	$	(9.0	)	$	97.8		$	76.2
Schedule of effective income tax rate reconciliation	The following is a reconciliation of income taxes computed at the statutory U.S. Federal income tax rate to the actual effective income tax provision (benefit) from continuing operations:
		Income Tax Provision (Benefit)
	(In millions)	2014			2013			2012
	Taxes computed at the federal rate	$	0.5		$	(54.2	)	$	81.3
	State and local income taxes, net of federal tax benefit	(2.0		)	(11.8		)	0.6
	Tax reserve adjustments	(0.5		)	(10.2		)	(0.4		)
	Repatriation of foreign earnings	0.3			9.4			1.3
	Valuation allowance	0.5			9.1			2.2
	Adjustment to prior years’ taxes	0.1			(5.3		)	1.4
	Foreign earnings taxed at different rate	(6.6		)	(2.5		)	(10.2		)
	Manufacturing deduction	—			—			(7.1		)
	Other	(1.0		)	1.9			3.3
	Income tax provision (benefit)	$	(8.7	)	$	(63.6	)	$	72.4
Schedule of income before income tax	Income (loss) from continuing operations before income taxes for the Company’s U.S. and non-U.S. operations was as follows:
	(In millions)	2014			2013			2012
	U.S.	$	(46.1	)	$	(180.0	)	$	178.4
	Non-U.S.	47.6			25.2			53.9
	Income (loss) from continuing operations before income taxes	$	1.5		$	(154.8	)	$	232.3
Schedule of income taxes paid	Income taxes paid and amounts received as refunds were as follows:
	(In millions)	2014			2013			2012
	Income taxes paid	$	15.1		$	21.4		$	101.7
	Income tax refunds received	(20.2		)	(18.3		)	(15.8		)
	Income taxes paid (received), net	$	(5.1	)	$	3.1		$	85.9
Schedule of deferred tax assets and liabilities	The categories of assets and liabilities that have resulted in differences in the timing of the recognition of income and expense at December 31, 2014 and 2013 were as follows:
	(In millions)	2014			2013
	Deferred income tax assets
	Pensions	$	251.8		$	115.7
	Postretirement benefits other than pensions	169			182.9
	Federal and state net operating loss tax carryovers	122.7			32.2
	Federal and state tax credits	53.6			42
	Deferred compensation and other benefit plans	25.6			29.4
	Self insurance reserves	10.1			10.1
	Other items	79.1			79.5
	Gross deferred income tax assets	711.9			491.8
	Valuation allowance for deferred tax assets	(34.4		)	(33.9		)
	Total deferred income tax assets	677.5			457.9
	Deferred income tax liabilities
	Bases of property, plant and equipment	579.5			488.1
	Inventory valuation	111.7			66.5
	Bases of amortizable intangible assets	75.5			67.1
	Other items	53.9			46.3
	Total deferred tax liabilities	820.6			668
	Net deferred tax liability	$	(143.1	)	$	(210.1	)
Schedule of changes in unrecognized income tax benefits	The changes in the liability for unrecognized income tax benefits for the years ended December 31, 2014, 2013 and 2012 were as follows:
	(In millions)	2014			2013			2012
	Balance at beginning of year	$	72.8		$	29.2		$	29.7
	Increases in prior period tax positions	2			0.1			0.2
	Decreases in prior period tax positions	(0.6		)	(5.8		)	(0.3		)
	Increases in current period tax positions	0.7			60.4			1.2
	Expiration of the statute of limitations	(0.5		)	(0.7		)	(2.0		)
	Settlements	(0.7		)	(8.6		)	(0.4		)
	Interest and penalties, net	(0.3		)	(1.8		)	0.8
	Balance at end of year	$	73.4		$	72.8		$	29.2
Summary of income tax examinations	A summary of tax years that remain subject to examination, by major tax jurisdiction, is as follows:
	Jurisdiction	Earliest Year Open to
		Examination
	U.S. Federal	2013
	States:
	Alabama	2011
	Illinois	2011
	North Carolina	2010
	Oregon	2011
	Pennsylvania	2011
	Foreign:
	China	2010
	Germany	2012
	Poland	2010
	United Kingdom	2011

Business_Segments_Tables

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Schedule of sales by segment
	(In millions)		2014			2013				2012
	Total sales:
	High Performance Materials & Components		$	2,084.60		$	2,016.70			$	2,398.10
	Flat Rolled Products		2,320.20			2,146.60				2,398.90
	Total sales		4,404.80			4,163.30				4,797.00
	Intersegment sales:
	High Performance Materials & Components		77.8			71.9				84.1
	Flat Rolled Products		103.6			47.9				46
	Total intersegment sales		181.4			119.8				130.1
	Sales to external customers:
	High Performance Materials & Components		2,006.80			1,944.80				2,314.00
	Flat Rolled Products		2,216.60			2,098.70				2,352.90
	Total sales to external customers		$	4,223.40		$	4,043.50			$	4,666.90
Schedule of operating profit (loss) by segment
	(In millions)		2014			2013				2012
	Operating profit (loss):
	High Performance Materials & Components		$	289.6		$	209.1			$	385.4
	Flat Rolled Products		(43.3		)	(44.7		)		127.8
	Total operating profit		246.3			164.4				513.2
	Corporate expenses		(44.2		)	(43.0		)		(68.4		)
	Interest expense, net		(108.7		)	(65.2		)		(71.6		)
	Restructuring costs		—			(67.5		)		—
	Closed company and other expenses		(21.2		)	(14.2		)		(18.5		)
	Retirement benefit expense		(70.7		)	(129.3		)		(122.4		)
	Income (loss) before income taxes		$	1.5		$	(154.8	)		$	232.3
Schedule of other financial information by segment	Certain additional information regarding the Company’s business segments is presented below:
	(In millions)		2014			2013				2012
	Depreciation and amortization:
	High Performance Materials & Components		$	124.4		$	127.4			$	130
	Flat Rolled Products		49.3			49.5				49.7
	Corporate		2.9			3.7				1.7
	Total depreciation and amortization		176.6			180.6				181.4
	Capital expenditures:
	High Performance Materials & Components		51.9			39.5				59.9
	Flat Rolled Products		172.1			568.1				311.3
	Corporate		1.7			0.2				1.3
	Total capital expenditures		225.7			607.8				372.5
	Identifiable assets:		2014			2013				2012
	High Performance Materials & Components		3,555.80			3,452.20				3,720.70
	Flat Rolled Products		2,601.60			2,320.90				1,857.00
	Discontinued Operations		1.8			9.8				214
	Corporate:
	Prepaid pension cost		—			5.1				—
	Deferred taxes		—			—				71.5
	Cash and cash equivalents and other		423.4			1,110.50				384.6
	Total assets		$	6,582.60		$	6,898.50			$	6,247.80
Schedule of revenue by country	Geographic information for external sales based on country of destination, and assets, are as follows:
	($ in millions)		2014			Percent			2013				Percent		2012		Percent
						of total							of total				of total
	External sales:
	United States		$	2,615.90		62	%		$	2,458.40			61	%	$	2,961.10	63	%
	China		249.6			6	%		237.7				6	%	255.4		5	%
	United Kingdom		228.4			5	%		251.5				6	%	303.9		7	%
	Germany		207.7			5	%		215.4				5	%	256		6	%
	France		168.1			4	%		152.8				4	%	157		3	%
	Italy		160.7			4	%		132.3				3	%	136.1		3	%
	Canada		147			3	%		141				4	%	134.9		3	%
	Japan		89.3			2	%		124.7				3	%	93.7		2	%
	Mexico		76.5			2	%		54.9				1	%	49.3		1	%
	Other		280.2			7	%		274.8				7	%	319.5		7	%
	Total External Sales		$	4,223.40		100	%		$	4,043.50			100	%	$	4,666.90	100	%
Schedule of company assets by country
	($ in millions)		2014			Percent			2013				Percent		2012		Percent
						of total							of total				of total
	Total assets:
	United States		$	5,879.60		90	%		$	6,145.40			89	%	$	5,505.00	88	%
	China		280.5			4	%		258.1				4	%	276.2		4	%
	United Kingdom		196.3			3	%		208				3	%	239.2		4	%
	Luxembourg (a)		81.8			1	%		145.9				2	%	48.3		1	%
	Other		144.4			2	%		141.1				2	%	179.1		3	%
	Total Assets		$	6,582.60		100	%		$	6,898.50			100	%	$	6,247.80	100	%
	(a)	Comprises assets held by the Company’s European Treasury Center operation.

Per_Share_Information_Tables

Per Share Information (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Schedule earnings per share	The following table sets forth the computation of basic and diluted income (loss) from continuing operations per common share:
	(In millions, except per share amounts)
	For the Years Ended December 31,	2014			2013			2012
	Numerator:
	Numerator for basic income (loss) from continuing operations per common share -
	Income (loss) from continuing operations attributable to ATI	$	(2.0	)	$	(98.8	)	$	150.5
	Redeemable noncontrolling interest (Note 17)	(0.3		)	—			—
	Effect of dilutive securities:
	4.25% Convertible Senior Notes due 2014	—			—			8.5
	Numerator for diluted net income (loss) per common share -
	Income (loss) from continuing operations attributable to ATI after assumed conversions	$	(2.3	)	$	(98.8	)	$	159
	Denominator:
	Denominator for basic net income per common share—weighted average shares	107.1			106.8			106.1
	Effect of dilutive securities:
	Share-based compensation	—			—			0.9
	4.25% Convertible Senior Notes due 2014	—			—			9.6
	Denominator for diluted net income per common share—adjusted weighted average shares and assumed conversions	107.1			106.8			116.6
	Basic income (loss) from continuing operations attributable to ATI per common share	$	(0.02	)	$	(0.93	)	$	1.42
	Diluted income (loss) from continuing operations attributable to ATI per common share	$	(0.02	)	$	(0.93	)	$	1.36

Financial_Information_for_Subs1

Financial Information for Subsidiary and Guarantor Parent (Tables)	12 Months Ended
	Dec. 31, 2014
Financial Information for Subsidiary and Guarantor Parent [Abstract]
Schedule of condensed consolidating balance sheets	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Balance Sheets
	December 31, 2013
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Assets:
	Cash and cash equivalents	$	3.6		$	13.5		$	1,009.70		$	—		$	1,026.80
	Accounts receivable, net	0.3			179.4			348.5			—			528.2
	Intercompany notes receivable	—			—			1,589.40			(1,589.4		)	—
	Inventories, net	—			295.5			1,026.60			—			1,322.10
	Prepaid expenses and other current assets	26.2			6.5			41			—			73.7
	Total current assets	30.1			494.9			4,015.20			(1,589.4		)	2,950.80
	Property, plant and equipment, net	2.9			1,397.50			1,473.70			—			2,874.10
	Cost in excess of net assets acquired	—			112.1			615.8			—			727.9
	Intercompany notes receivable	—			—			200			(200.0		)	—
	Investments in subsidiaries	6,170.80			37.7			—			(6,208.5		)	—
	Other assets	35.7			32			278			—			345.7
	Total assets	$	6,239.50		$	2,074.20		$	6,582.70		$	(7,997.9	)	$	6,898.50
	Liabilities and stockholders’ equity:
	Accounts payable	$	3.1		$	310.5		$	158.2		$	—		$	471.8
	Accrued liabilities	51.6			56.6			207.6			—			315.8
	Intercompany notes payable	825.6			763.8			—			(1,589.4		)	—
	Deferred income taxes	3.5			—			—			—			3.5
	Short-term debt and current portion of long-term debt	402.9			0.1			16.9			—			419.9
	Total current liabilities	1,286.70			1,131.00			382.7			(1,589.4		)	1,211.00
	Long-term debt	1,350.80			150.4			26.2			—			1,527.40
	Intercompany notes payable	—			200			—			(200.0		)	—
	Accrued postretirement benefits	—			179.7			262.7			—			442.4
	Pension liabilities	323			5.6			39.6			—			368.2
	Deferred income taxes	206.6			—			—			—			206.6
	Other long-term liabilities	77.7			20.2			50.3			—			148.2
	Total liabilities	3,244.80			1,686.90			761.5			(1,789.4		)	3,903.80
	Total stockholders’ equity	2,994.70			387.3			5,821.20			(6,208.5		)	2,994.70
	Total liabilities and stockholders’ equity	$	6,239.50		$	2,074.20		$	6,582.70		$	(7,997.9	)	$	6,898.50
	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Balance Sheets
	December 31, 2014
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Assets:
	Cash and cash equivalents	$	2.2		$	13.8		$	253.5		$	—		$	269.5
	Accounts receivable, net	0.1			209.1			394.4			—			603.6
	Intercompany notes receivable	—			—			2,390.80			(2,390.8		)	—
	Inventories, net	—			387.7			1,085.10			—			1,472.80
	Prepaid expenses and other current assets	63.7			13.2			59.3			—			136.2
	Total current assets	66			623.8			4,183.10			(2,390.8		)	2,482.10
	Property, plant and equipment, net	2.2			1,545.10			1,414.50			—			2,961.80
	Cost in excess of net assets acquired	—			126.6			653.8			—			780.4
	Intercompany notes receivable	—			—			200			(200.0		)	—
	Investments in subsidiaries	6,149.40			37.7			—			(6,187.1		)	—
	Other assets	23.7			28			306.6			—			358.3
	Total assets	$	6,241.30		$	2,361.20		$	6,758.00		$	(8,777.9	)	$	6,582.60
	Liabilities and stockholders’ equity:
	Accounts payable	$	4.5		$	302		$	250.2		$	—		$	556.7
	Accrued liabilities	47.5			72			203.7			—			323.2
	Intercompany notes payable	1,232.60			1,158.20			—			(2,390.8		)	—
	Deferred income taxes	62.2			—			—			—			62.2
	Short-term debt and current portion of long-term debt	0.5			0.1			17.2			—			17.8
	Total current liabilities	1,347.30			1,532.30			471.1			(2,390.8		)	959.9
	Long-term debt	1,350.60			150.3			8.2			—			1,509.10
	Intercompany notes payable	—			200			—			(200.0		)	—
	Accrued postretirement benefits	—			153			262.8			—			415.8
Pension liabilities	675.5			6			57.8			—			739.3
Deferred income taxes	80.9			—			—			—			80.9
Other long-term liabilities	77.7			22.5			56			—			156.2
Total liabilities	3,532.00			2,064.10			855.9			(2,590.8		)	3,861.20
Redeemable noncontrolling interest	—			—			12.1			—			12.1
Total stockholders’ equity	2,709.30			297.1			5,890.00			(6,187.1		)	2,709.30
Total liabilities and stockholders’ equity	$	6,241.30		$	2,361.20		$	6,758.00		$	(8,777.9	)	$	6,582.60
Schedule of condensed consolidating statements of operations	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Statements of Operations
	For the year ended December 31, 2014
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Sales	$	—		$	1,878.00		$	2,345.40		$	—		$	4,223.40
	Cost of sales	45.3			1,874.80			1,924.70			—			3,844.80
	Selling and administrative expenses	103.9			44			124.6			—			272.5
	Income (loss) before interest, other income and income taxes	(149.2		)	(40.8		)	296.1			—			106.1
	Interest income (expense), net	(111.0		)	(44.9		)	47.2			—			(108.7		)
	Other income (expense) including equity in income of unconsolidated subsidiaries	261.7			1.1			2.9			(261.6		)	4.1
	Income (loss) from continuing operations before income taxes	1.5			(84.6		)	346.2			(261.6		)	1.5
	Income tax provision (benefit)	(8.7		)	(29.3		)	116.7			(87.4		)	(8.7		)
	Income (loss) from continuing operations	10.2			(55.3		)	229.5			(174.2		)	10.2
	Income (loss) from discontinued operations, net of tax	(0.6		)	—			(0.6		)	0.6			(0.6		)
	Net income (loss)	9.6			(55.3		)	228.9			(173.6		)	9.6
	Less: Net income attributable to noncontrolling interest	—			—			12.2			—			12.2
	Net income (loss) attributable to ATI	$	9.6		$	(55.3	)	$	216.7		$	(173.6	)	$	(2.6	)
	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Statements of Operations
	For the year ended December 31, 2013
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Sales	$	—		$	1,769.40		$	2,274.10		$	—		$	4,043.50
	Cost of sales	75.2			1,748.80			1,966.90			—			3,790.90
	Selling and administrative expenses	124.3			34.9			117.2			—			276.4
	Restructuring costs	1.1			15.7			50.7			—			67.5
	Income (loss) before interest, other income and income taxes	(200.6		)	(30.0		)	139.3			—			(91.3		)
	Interest income (expense), net	(63.4		)	(37.2		)	35.4			—			(65.2		)
	Other income (expense) including equity in income of unconsolidated subsidiaries	109.2			0.9			0.8			(109.2		)	1.7
	Income (loss) from continuing operations before income taxes	(154.8		)	(66.3		)	175.5			(109.2		)	(154.8		)
	Income tax provision (benefit)	(63.6		)	(20.0		)	40.4			(20.4		)	(63.6		)
	Income (loss) from continuing operations	(91.2		)	(46.3		)	135.1			(88.8		)	(91.2		)
	Income (loss) from discontinued operations, net of tax	252.8			—			252.8			(252.8		)	252.8
	Net income (loss)	161.6			(46.3		)	387.9			(341.6		)	161.6
	Less: Net income attributable to noncontrolling interest	—			—			7.6			—			7.6
	Net income (loss) attributable to ATI	$	161.6		$	(46.3	)	$	380.3		$	(341.6	)	$	154
	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Statements of Operations
	For the year ended December 31, 2012
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Sales	$	—		$	2,031.80		$	2,635.10		$	—		$	4,666.90
	Cost of sales	57			1,888.20			2,096.20			—			4,041.40
	Selling and administrative expenses	144.2			42.6			134.8			—			321.6
	Income (loss) before interest, other income and income taxes	(201.2		)	101			404.1			—			303.9
	Interest expense, net	(60.7		)	(10.5		)	(0.4		)	—			(71.6		)
	Other income (expense) including equity in income of unconsolidated subsidiaries	494.2			(21.5		)	31.8			(504.5		)	—
	Income (loss) from continuing operations, before income taxes	232.3			69			435.5			(504.5		)	232.3
	Income tax provision (benefit)	72.4			27.5			168.7			(196.2		)	72.4
	Income (loss) from continuing operations	159.9			41.5			266.8			(308.3		)	159.9
	Income (loss) from discontinued operations, net of tax	7.9			—			7.9			(7.9		)	7.9
	Net income (loss)	167.8			41.5			274.7			(316.2		)	167.8
	Less: Net income (loss) attributable to noncontrolling interest	—			—			9.4			—			9.4
	Net income (loss) attributable to ATI	$	167.8		$	41.5		$	265.3		$	(316.2	)	$	158.4
Schedule of condensed consolidating comprehensive income	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Statements of Comprehensive Income
	For the year ended December 31, 2013
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Net income (loss)	$	161.6		$	(46.3	)	$	387.9		$	(341.6	)	$	161.6
	Other comprehensive income (loss)
	Currency translation adjustment arising during the period	15.3			—			15.3			(15.3		)	15.3
	Unrealized holding gain (loss) on securities	0.1			—			0.1			(0.1		)	0.1
	Net derivative loss on hedge transactions	(6.9		)	—			—			—			(6.9		)
	Pension and postretirement benefits	311.1			22			27.6			(49.6		)	311.1
	Other comprehensive income (loss), net of tax	319.6			22			43			(65.0		)	319.6
	Comprehensive income (loss)	481.2			(24.3		)	430.9			(406.6		)	481.2
	Less: Comprehensive income attributable to noncontrolling interest	—			—			11			—			11
	Comprehensive income (loss) attributable to ATI	$	481.2		$	(24.3	)	$	419.9		$	(406.6	)	$	470.2
	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Statements of Comprehensive Income
	For the year ended December 31, 2012
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Net income (loss)	$	167.8		$	41.5		$	274.7		$	(316.2	)	$	167.8
	Other comprehensive income (loss)
	Currency translation adjustment arising during the period	14.3			—			14.3			(14.3		)	14.3
	Net derivative loss on hedge transactions	(2.8		)	—			—			—			(2.8		)
	Pension and postretirement benefits	(97.4		)	(18.1		)	(5.1		)	23.2			(97.4		)
	Other comprehensive income (loss), net of tax	(85.9		)	(18.1		)	9.2			8.9			(85.9		)
	Comprehensive income (loss)	81.9			23.4			283.9			(307.3		)	81.9
	Less: Comprehensive income attributable to noncontrolling interest	—			—			11.3			—			11.3
	Comprehensive income (loss) attributable to ATI	$	81.9		$	23.4		$	272.6		$	(307.3	)	$	70.6
	Allegheny Technologies Incorporated
	Financial Information for Subsidiary and Guarantor Parent
	Statements of Comprehensive Income
	For the year ended December 31, 2014
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Net income (loss)	$	9.6		$	(55.3	)	$	228.9		$	(173.6	)	$	9.6
	Other comprehensive income (loss)
	Currency translation adjustment arising during the period	(33.6		)	—			(33.6		)	33.6			(33.6		)
	Net derivative gain on hedge transactions	25.9			—			—			—			25.9
	Pension and postretirement benefits	(212.6		)	1.8			(28.4		)	26.6			(212.6		)
	Other comprehensive income (loss), net of tax	(220.3		)	1.8			(62.0		)	60.2			(220.3		)
	Comprehensive income (loss)	(210.7		)	(53.5		)	166.9			(113.4		)	(210.7		)
	Less: Comprehensive income attributable to noncontrolling interest	—			—			10.1			—			10.1
	Comprehensive income (loss) attributable to ATI	$	(210.7	)	$	(53.5	)	$	156.8		$	(113.4	)	$	(220.8	)
Schedule of condensed consolidating statements of cash flow	Condensed Statements of Cash Flows
	For the year ended December 31, 2014
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Cash flows provided by (used in) operating activities	$	(66.9	)	$	(313.8	)	$	436.6		$	—		$	55.9
	Investing Activities:
	Purchases of property, plant and equipment	(0.1		)	(170.8		)	(54.8		)	—			(225.7		)
	Net receipts (payments) on intercompany activity	—			—			(1,027.7		)	1,027.70			—
	Purchases of businesses, net of cash acquired	—			—			(92.9		)	—			(92.9		)
	Asset disposals and other	—			1.7			0.7			—			2.4
	Cash flows provided by (used in) investing activities	(0.1		)	(169.1		)	(1,174.7		)	1,027.70			(316.2		)
	Financing Activities:
	Payments on long-term debt and capital leases	(397.9		)	(0.1		)	(16.9		)	—			(414.9		)
	Net receipts (payments) on intercompany activity	544.4			483.3			—			(1,027.7		)	—
	Dividends paid to stockholders	(77.1		)	—			—			—			(77.1		)
	Other	(3.8		)	—			(1.2		)	—			(5.0		)
	Cash flows provided by (used in) financing activities	65.6			483.2			(18.1		)	(1,027.7		)	(497.0		)
	Increase (decrease) in cash and cash equivalents	$	(1.4	)	$	0.3		$	(756.2	)	$	—		$	(757.3	)
	Condensed Statements of Cash Flows
	For the year ended December 31, 2012
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Cash flows provided by (used in) operating activities	$	(52.3	)	$	43.9		$	435.9		$	—		$	427.5
	Investing Activities:
	Purchases of property, plant and equipment	(1.7		)	(308.6		)	(71.7		)	—			(382.0		)
	Net receipts (payments) on intercompany activity	—			—			(304.4		)	304.4			—
	Asset disposals and other	—			0.3			3			—			3.3
	Cash flows provided by (used in) investing activities	(1.7		)	(308.3		)	(373.1		)	304.4			(378.7		)
	Financing Activities:
	Net receipts (payments) on intercompany activity	156.5			147.9			—			(304.4		)	—
	Dividends paid to stockholders	(76.5		)	—			—			—			(76.5		)
	Other	(21.2		)	(0.1		)	(27.0		)	—			(48.3		)
	Cash flows provided by (used in) financing activities	58.8			147.8			(27.0		)	(304.4		)	(124.8		)
	Increase (decrease) in cash and cash equivalents	$	4.8		$	(116.6	)	$	35.8		$	—		$	(76.0	)
	Condensed Statements of Cash Flows
	For the year ended December 31, 2013
	(In millions)	Guarantor			Subsidiary			Non-guarantor			Eliminations			Consolidated
		Parent						Subsidiaries
	Cash flows provided by (used in) operating activities	$	(41.1	)	$	(50.4	)	$	484.2		$	(24.3	)	$	368.4
	Investing Activities:
	Purchases of property, plant and equipment	(0.2		)	(564.8		)	(47.7		)	—			(612.7		)
	Net receipts (payments) on intercompany activity	—			—			(248.8		)	248.8			—
	Proceeds from sale of business, net of transaction costs	(7.9		)	—			608.8			—			600.9
	Asset disposals and other	—			0.2			0.6			—			0.8
	Cash flows provided by (used in) investing activities	(8.1		)	(564.6		)	312.9			248.8			(11.0		)
	Financing Activities:
	Borrowings on long-term debt	500			—			—			—			500
	Net receipts (payments) on intercompany acivity	(366.7		)	615.5			—			(248.8		)	—
	Dividends paid to stockholders	(76.9		)	—			(24.3		)	24.3			(76.9		)
	Other	(9.1		)	(0.1		)	(49.1		)	—			(58.3		)
	Cash flows provided by (used in) financing activities	47.3			615.4			(73.4		)	(224.5		)	364.8
	Increase (decrease) in cash and cash equivalents	$	(1.9	)	$	0.4		$	723.7		$	—		$	722.2

Selected_Quarterly_Financial_D1

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Schedule of quarterly financial information
		Quarter Ended
	(In millions, except share and per share amounts)	March 31			June 30			September 30			December 31
	2014 -
	Sales	$	987.3		$	1,119.00		$	1,069.60		$	1,047.50
	Gross Profit	70.2			89.5			97			121.9
	Income (loss) from continuing operations attributable to ATI	(18.1		)	(3.8		)	—			19.9
	Net income (loss)	(17.9		)	(0.7		)	2.9			25.3
	Net income (loss) attributable to ATI	(20.0		)	(4.0		)	(0.7		)	22.1
	Basic income (loss) from continuing operations attributable to ATI per common share	$	(0.17	)	$	(0.03	)	$	—		$	0.18
	Basic income (loss) attributable to ATI per common share	$	(0.19	)	$	(0.03	)	$	(0.01	)	$	0.2
	Diluted income (loss) from continuing operations attributable to ATI per common share	$	(0.17	)	$	(0.03	)	$	—		$	0.18
	Diluted income (loss) attributable to ATI per common share	$	(0.19	)	$	(0.03	)	$	(0.01	)	$	0.2
	Average shares outstanding	108,173,581			108,628,024			108,712,682			108,704,983
	2013 -
	Sales	$	1,099.00		$	1,056.80		$	972.4		$	915.3
	Gross Profit	100.5			87.7			53.1			11.3
	Income (loss) from continuing operations attributable to ATI	9.7			3.7			(28.4		)	(83.8		)
	Net income (loss)	11.6			6.6			(32.2		)	175.6
	Net income (loss) attributable to ATI	10			4.4			(33.8		)	173.4
	Basic income (loss) from continuing operations attributable to ATI per common share	$	0.09		$	0.04		$	(0.27	)	$	(0.79	)
	Basic income (loss) attributable to ATI per common share	$	0.09		$	0.04		$	(0.32	)	$	1.62
	Diluted income (loss) from continuing operations attributable to ATI per common share	$	0.09		$	0.04		$	(0.27	)	$	(0.79	)
	Diluted income (loss) attributable to ATI per common share	$	0.09		$	0.04		$	(0.32	)	$	1.62
	Average shares outstanding	107,614,468			107,980,753			108,001,306			107,984,535

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - Principles of Consolidation (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Noncontrolling Interest [Line Items]
Related party accounts receivable	$4.30	$3.10
Shanghai STAL Precision Stainless Steel Co Ltd [Member]
Noncontrolling Interest [Line Items]
Joint venture ownership percentage	60.00%
Joint venture ownership percentage by unaffiliated entity	40.00%
Uniti [Member]
Noncontrolling Interest [Line Items]
Equity method investment ownership percentage	50.00%

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Basis of Presentation (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disposal Group, Including Discontinued Operations [Line Items]
Sales	$1,047.50	$1,069.60	$1,119	$987.30	$915.30	$972.40	$1,056.80	$1,099	$4,223.40	$4,043.50	$4,666.90

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Risks and Uncertainties and Use of Estimates (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	customer	customer	customer
Segment Reporting Information [Line Items]
Number of employees	9,700
Percent of employees located outside of the U.S.	15.00%
Percent of employees covered by collective bargaining agreements	50.00%
Sales Revenue [Member]
Segment Reporting Information [Line Items]
Number of customers	0	0	0
Workforce Subject to Collective Bargaining Arrangements [Member] | Flat Rolled Products [Member]
Segment Reporting Information [Line Items]
Number of employees	2,300
Workforce Subject to Collective Bargaining Arrangements [Member] | High Performance Materials & Components [Member]
Segment Reporting Information [Line Items]
Number of employees	150

Summary_of_Significant_Account5

Summary of Significant Accounting Policies - Accounts Receivable (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Accounting Policies [Abstract]
Allowances for Doubtful Accounts	$4.80	$5.30

Summary_of_Significant_Account6

Summary of Significant Accounting Policies - Cost in Excess of Net Assets Acquired (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Line Items]
Goodwill	$780,400,000	$727,900,000
Foreign currency translation adjustment effect on goodwill	-2,500,000
Goodwill impairment loss	0	0	0
High Performance Materials & Components [Member]
Goodwill [Line Items]
Goodwill	653,800,000
Flat Rolled Products [Member]
Goodwill [Line Items]
Goodwill	126,600,000
Dynamic Flowform Corp. and Hanard Machine, Inc. [Member]
Goodwill [Line Items]
Increase (decrease) in goodwill	$55,000,000

Summary_of_Significant_Account7

Summary of Significant Accounting Policies - Research and Development (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Research and Development Expense	$17.40	$16.10	$22.30
Customer funded research and development costs	$2.70	$2.70	$1.50

Acquisitions_Narrative_Details

Acquisitions - Narrative (Details) (USD $)	12 Months Ended			0 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 07, 2014	Jun. 12, 2014	Dec. 31, 2015
Business Acquisition [Line Items]
Cash consideration, net of cash acquired	$92.90	$0	$0
Goodwill	780.4	727.9
ATI Flowform [Member]
Business Acquisition [Line Items]
Percentage of company acquired				85.00%
Cash consideration, net of cash acquired				72.9
Noncontrolling interest held by others				15.00%
Acquisition costs				0.7
Intangible assets acquired				21.4
Weighted average life of acquired intangible assets				23 years
Goodwill				46.8
Hanard [Member]
Business Acquisition [Line Items]
Cash consideration, net of cash acquired	20				20.5
Intangible assets acquired					4.3
Weighted average life of acquired intangible assets					20 years
Goodwill					8.3
Hanard [Member] | Forecast Payment [Member]
Business Acquisition [Line Items]
Cash consideration, net of cash acquired						$0.50

Discontinued_Operations_Narrat

Discontinued Operations - Narrative (Details) (USD $)	3 Months Ended	12 Months Ended			3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of business, net of transaction costs		$0	$600.90	$0
Restructuring costs, net of tax	41.2		41.2
Tungsten Materials Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of business, net of transaction costs			600.9
Gain on disposed operation, pre-tax			428.3
Gain on disposed operation net of tax			261.4
Iron Castings Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restructuring Charge		1.8		13
Cash exit costs paid		1
Restructuring costs, net of tax				8.8
Iron Castings and Fabricated Components Businesses [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restructuring Charge			19.5
Restructuring costs, net of tax	6.1		11.9		5.8
Asset impairment charges			$18.60

Discontinued_Operations_Schedu

Discontinued Operations - Schedule of Income (Loss) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Discontinued Operations and Disposal Groups [Abstract]
Sales	$14.90	$268.20	$364.60
Income (loss) before income taxes	($0.90)	$414.20	$11.70

Discontinued_Operations_Schedu1

Discontinued Operations - Schedule of Assets and LIabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Discontinued Operations and Disposal Groups [Abstract]
Prepaid expenses and other current assets	$0.40	$6.10
Other assets	1.4	3.7
Total Assets	1.8	9.8
Accrued liabilities	2.5	4.9
Other long-term liabilities	0.6	0.7
Total Liabilities	3.1	5.6
Net Assets (Liabilities)	($1.30)	$4.20

Inventories_Details

Inventories (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Raw Materials And Supplies	$249.30	$277.60
Work In Process	1,184.10	984.9
Finished Goods	172.2	162.1
Total inventories at current cost	1,605.60	1,424.60
Adjustment from current cost to LIFO cost basis	-4.8	-29.4
Inventory valuation reserves	68.8	84.3
Progress payments	-68.8	-47.6
Total inventories, net	1,472.80	1,322.10
LIFO Inventory Amount	1,102.40	976.1
LIFO provision (benefit)	24.6	-80.9	-75.6
Inventory valuation reserve		55.5
Effect of LIFO liquidation on income	0	-3.8	-1.5
High Performance Materials & Components [Member]
Segment Reporting Information [Line Items]
Inventory valuation reserves	10	35
Flat Rolled Products [Member]
Segment Reporting Information [Line Items]
Inventory valuation reserve	$23.20	$20.50

Property_Plant_and_Equipment_D

Property, Plant and Equipment (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property Plant And Equipment Details [Abstract]
Land	$30.20	$30.20
Buildings	1,048.90	1,019.10
Equipment and leasehold improvements	3,702.50	3,526
Property plant and equipment, gross	4,781.60	4,575.30
Accumulated depreciation and amortization	-1,819.80	-1,701.20
Property, plant and equipment, net	2,961.80	2,874.10
Construction in progress	71.1	186.2
Depreciation, Depletion and Amortization [Abstract]
Software and other amortization	10	5
Total depreciation and amortization	176.8	189.9	194
Continuing Operations [Member]
Depreciation, Depletion and Amortization [Abstract]
Depreciation of property, plant and equipment	146.7	156.8	157
Software and other amortization	29.9	23.8	24.4
Total depreciation and amortization	$176.60	$180.60	$181.40

Asset_Retirement_Obligations_D

Asset Retirement Obligations (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loss Contingencies [Line Items]
Asset retirement obligation	$25.40	$27.70	$13
Revision of estimates	-1	13.8
Tungsten Materials Business [Member]
Loss Contingencies [Line Items]
Asset retirement obligation		13
Asset retirement obligation period		5 years
Revision of estimates		9.4
Restructuring Charges [Member]
Loss Contingencies [Line Items]
Revision of estimates		$4.20

Asset_Retirement_Obligations_C

Asset Retirement Obligations - Change in Asset Retirement Obligations (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Asset Retirement Obligation Disclosure [Abstract]
Balance at beginning of year	$27.70	$13
Accretion expense	0.9	1.1
Payments	-2.2	-0.8
Revision of estimates	-1	13.8
Liabilities incurred	0	0.6
Balance at end of year	$25.40	$27.70

Supplemental_Financial_Stateme2

Supplemental Financial Statement Information - Cash and Cash Equivalents (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Millions, unless otherwise specified
Cash and Cash Equivalents [Abstract]
Cash	$267.70	$1,025.20
Other short-term investments	1.8	1.6
Total cash and cash equivalents	$269.50	$1,026.80	$304.60	$380.60

Supplemental_Financial_Stateme3

Supplemental Financial Statement Information - Allowance for Doubtful Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for doubtful accounts	$4.80	$5.30
Reserve for doubtful accounts, increase	0.5	1.1	1
Reserve for doubtful accounts, decrease	1	0.8	1.4
Tungsten Materials Business [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserve for doubtful accounts, decrease		$0.50

Supplemental_Financial_Stateme4

Supplemental Financial Statement Information - Intangible Assets (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Feb. 07, 2014	Jun. 12, 2014
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$191.70	$105
Finite-lived intangible assets, accumulated amortization	-23.2	-13.2
Impairment of indefinite-lived intangible assets	0	0
Indefinite-lived Intangible Assets [Line Items]
Total intangible assets, Gross	191.7	166
Amortization expense	10	5
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2015	10
2016	10
2017	10
2018	10
2019	10
Trademarks [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	0	61
ATI Flowform [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired			21.4
Hanard [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired				4.3
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life	21 years
Finite-lived intangible assets, gross	91.4	74
Finite-lived intangible assets, accumulated amortization	-14.2	-9.9
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life	24 years
Finite-lived intangible assets, gross	35.7	31
Finite-lived intangible assets, accumulated amortization	-4.7	-3.3
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life	15 years
Finite-lived intangible assets, gross	64.6	0
Finite-lived intangible assets, accumulated amortization	($4.30)	$0

Supplemental_Financial_Stateme5

Supplemental Financial Statement Information - Accrued Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Additional Financial Information Disclosure [Abstract]
Accrued salaries, wages and payroll liabilities	$77.30	$52.70

Supplemental_Financial_Stateme6

Supplemental Financial Statement Information - Other Non-operating Income (Expense) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Nonoperating Income (Expense) [Abstract]
Rent and royalty income	$4	$0.90	$0.70
Net gains (losses) on property and investments	0.1	0.7	-0.7
Other	0	0.1	0
Other income, net	$4.10	$1.70	$0

Debt_Schedule_of_Debt_Details

Debt - Schedule of Debt (Details) (USD $)	0 Months Ended	12 Months Ended
	Jul. 12, 2013	Dec. 31, 2014		Dec. 31, 2013		Aug. 15, 2014
Debt Instrument [Line Items]
Total short-term and long-term debt		$1,526,900,000		$1,947,300,000
Short-term debt and current portion of long-term debt		17,800,000		419,900,000
Total long-term debt		1,509,100,000		1,527,400,000
Domestic Bank Group $400 million unsecured credit agreement [Member]
Debt Instrument [Line Items]
Line of credit facility amount outstanding		0		0
Allegheny Technologies $500 million 5.875% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument issuer		Allegheny Technologies
Debt instrument maturity date	15-Aug-23
Debt instrument interest rate stated percentage				5.88%		6.13%
Debt instrument carrying amount	500,000,000	500,000,000	[1]	500,000,000	[1]
Allegheny Technologies $500 million 5.95% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Debt instrument issuer		Allegheny Technologies		Allegheny Technologies
Debt instrument interest rate stated percentage		5.95%		5.95%
Debt instrument carrying amount		500,000,000		500,000,000
Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Debt instrument issuer				Allegheny Technologies
Debt instrument interest rate stated percentage				4.25%
Debt instrument carrying amount		0		402,500,000
Allegheny Technologies $350 million 9.375% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Debt instrument issuer		Allegheny Technologies		Allegheny Technologies
Debt instrument interest rate stated percentage		9.38%		9.38%
Debt instrument carrying amount		350,000,000		350,000,000
Allegheny Ludlum 6.95% Debentures due 2025 [Member]
Debt Instrument [Line Items]
Debt instrument issuer		Allegheny Ludlum		Allegheny Ludlum
Debt instrument interest rate stated percentage		6.95%		6.95%
Debt instrument carrying amount		150,000,000		150,000,000
Ladish Series B 6.14% Notes due 2016 [Member]
Debt Instrument [Line Items]
Debt instrument issuer		ATI Ladish, LLC	[2]	ATI Ladish, LLC	[2]
Debt instrument interest rate stated percentage		6.14%	[2]	6.14%	[2]
Debt instrument carrying amount		11,900,000	[3]	18,200,000	[3]
Business acquisition fair value adjustment of debt assumed		400,000		1,000,000
Ladish Series C 6.41% Notes due 2015 [Member]
Debt Instrument [Line Items]
Debt instrument issuer		ATI Ladish, LLC	[3]	ATI Ladish, LLC	[3]
Debt instrument interest rate stated percentage		6.41%	[3]	6.41%	[3]
Debt instrument carrying amount		10,300,000	[2]	21,100,000	[2]
Business acquisition fair value adjustment of debt assumed		300,000		1,100,000
Foreign credit agreements [Member]
Debt Instrument [Line Items]
Debt instrument carrying amount		0		0
Industrial revenue bonds, due through 2020, and other [Member]
Debt Instrument [Line Items]
Debt instrument carrying amount		$4,700,000		$5,500,000
[1]	earing interest at 6.125% effective August 15, 2014.
[2]	Includes fair value adjustments of $0.3 million and $1.1 million at December 31, 2014 and December 31, 2013, respectively.
[3]	Includes fair value adjustments of $0.4 million and $1.0 million at December 31, 2014 and December 31, 2013, respectively.

Debt_Narrative_Details

Debt - Narrative (Details)

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Jul. 12, 2013

Dec. 31, 2014

Dec. 31, 2013

Aug. 15, 2014

Jun. 02, 2014

Jun. 01, 2014

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

Dec. 31, 2014

USD ($)

USD ($)

USD ($)

Allegheny Technologies $500 million 5.875% Senior Notes due 2023 [Member]

Allegheny Technologies $500 million 5.875% Senior Notes due 2023 [Member]

Allegheny Technologies $500 million 5.875% Senior Notes due 2023 [Member]

Allegheny Technologies $500 million 5.875% Senior Notes due 2023 [Member]

Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014 [Member]

Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014 [Member]

Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014 [Member]

Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014 [Member]

Ladish Series B 6.14% Notes due 2016 [Member]

Ladish Series B 6.14% Notes due 2016 [Member]

Ladish Series C 6.41% Notes due 2015 [Member]

Ladish Series C 6.41% Notes due 2015 [Member]

Domestic Bank Group $400 million unsecured credit agreement [Member]

Domestic Bank Group $400 million unsecured credit agreement [Member]

Seperate Letter of Credit Facility [Member]

STAL Revolving Credit Facility [Member]

STAL Revolving Credit Facility [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

CNY

Domestic Bank Group $400 million unsecured credit agreement [Member]

Domestic Bank Group $400 million unsecured credit agreement [Member]

Domestic Bank Group $400 million unsecured credit agreement [Member]

Domestic Bank Group $400 million unsecured credit agreement [Member]

Domestic Bank Group $400 million unsecured credit agreement [Member]

Domestic Bank Group $400 million unsecured credit agreement [Member]

London Interbank Offered Rate (LIBOR) [Member]

Prime Lending Rate [Member]

London Interbank Offered Rate (LIBOR) [Member]

Prime Lending Rate [Member]

Interest Costs Incurred [Abstract]

Interest expense

$109,800,000

$66,000,000

$72,400,000

Interest costs capitalized

5,300,000

45,700,000

24,500,000

Interest costs paid

113,200,000

110,600,000

96,500,000

Interest income

1,100,000

800,000

800,000

Long-term Debt, Fiscal Year Maturity [Abstract]

2015

17,800,000

2016

7,700,000

2017

500,000

2018

200,000

2019

350,100,000

Debt Instrument [Line Items]

Debt instrument carrying amount

500,000,000

500,000,000

[1]

500,000,000

[1]

0

402,500,000

11,900,000

[2]

18,200,000

[2]

10,300,000

[3]

21,100,000

[3]

Debt instrument interest rate stated percentage

5.88%

6.13%

4.25%

6.14%

[3]

6.14%

[3]

6.41%

[2]

6.41%

[2]

Repayments of Convertible Debt

397,500,000

Debt instrument maturity date

15-Aug-23

Payments of debt issuance costs

1,200,000

5,200,000

0

5,200,000

1,200,000

Amortization period of debt issuance costs

10 years

Line of credit maximum borrowing capacity

400,000,000

205,000,000

Line of credit borrowing capacity increase limit

100,000,000

Amount of cash on hand used to reduce the indebtness figure used in the leverage ratio calculation

50,000,000

Maximum leverage ratio quarter ended March 31, 2015

5.75

Maximum leverage ratio quarter ended June 30, 2015

5

Maximum leverage ratio quarter ended September 30, 2015

4.5

Maximum leverage ratio quarter ended December 31, 2015

3.75

Debt Instrument, Covenant, Maximum Leverage Ratio, Period Five

3.5

Minimum interest coverage ratio quarter ended March 31, 2015

2

Minimum interest coverage ratio quarter ended June 30, 2015

2.5

Minimum interest coverage ratio quarter ended September 30, 2015

3

Minimum interest coverage ratio quarter ended December 31, 2015

3.25

Debt Instrument, Covenant, Minimum Interest Coverage Ratio, Period Five

3.5

Leverage ratio

4.2

Interest coverage ratio

2.79

Line of credit facility amount outstanding

0

0

32,000,000

Credit facility amount used to support letters of credit

4,700,000

Credit facility sublimit for letters of credit

200,000,000

Variable rate spread

1.25%

0.25%

2.50%

1.50%

Letter of credit fee

1.25%

2.50%

Facility fee

0.18%

0.35%

Convertible notes, Amount converted

5,000,000

Convertible notes, Shares issued

120,476

Convertible debt conversion rate in shares of stock (per $1,000 of notes)

23.9263

Conversion price of convertible notes

$41.80

Outstanding balance

$11,500,000

$10,000,000

Funded debt limit maximum percent of capitalization

60.00%

Joint venture ownership percentage

60.00%

[1]

earing interest at 6.125% effective August 15, 2014.

[2]

Includes fair value adjustments of $0.4 million and $1.0 million at December 31, 2014 and December 31, 2013, respectively.

[3]

Includes fair value adjustments of $0.3 million and $1.1 million at December 31, 2014 and December 31, 2013, respectively.

Derivative_Financial_Instrumen2

Derivative Financial Instruments and Hedging - Narrative (Details)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2014
	USD ($)	Foreign Exchange Forward [Member]	Foreign Exchange Forward [Member]
		Designated as Hedging Instrument [Member]	Designated as Hedging Instrument [Member]
		Maturity Dates Through 2018 [Member]	Maturity Dates Through 2015 [Member]
		EUR (€)	EUR (€)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Percentage of estimated annual nickel requirements	15.00%
Maximum amount of time hedged for nickel requirements	2020
Percentage of forecasted natural gas usage hedged for 2015	80.00%
Percentage of forecasted natural gas usage hedged for 2016	70.00%
Percentage of forecasted natural gas usage hedged for 2017	40.00%
Derivative [Line Items]
Derivative notional amount		€ 388	€ 175
Cash flow hedge gain (loss) to be reclassified within twelve months	$5.30

Derivative_Financial_Instrumen3

Derivative Financial Instruments and Hedging - Schedule of Derivative Instruments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	$59.90	$4.30
Fair value of derivative liability	27	21.6
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	53.5	4.3
Fair value of derivative liability	27	19.9
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	6.4	0
Fair value of derivative liability	0	1.7
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] | Prepaid expenses and other current assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	23.6	0.3
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	28.3	0
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	0	7.8
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	0	5.4
Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member] | Prepaid expenses and other current assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	6.4	0
Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	0	1.7
Nickel and other raw material contracts [Member] | Designated as Hedging Instrument [Member] | Prepaid expenses and other current assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	1.1	0.1
Nickel and other raw material contracts [Member] | Designated as Hedging Instrument [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	0.5	0.4
Nickel and other raw material contracts [Member] | Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	5.8	4.5
Nickel and other raw material contracts [Member] | Designated as Hedging Instrument [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	3	1.3
Electricity contracts [Member] | Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	0.1	0.5
Natural gas contracts [Member] | Designated as Hedging Instrument [Member] | Prepaid expenses and other current assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	0	2.5
Natural gas contracts [Member] | Designated as Hedging Instrument [Member] | Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative asset	0	1
Natural gas contracts [Member] | Designated as Hedging Instrument [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	10.2	0.4
Natural gas contracts [Member] | Designated as Hedging Instrument [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair value of derivative liability	$7.90	$0

Derivative_Financial_Instrumen4

Derivative Financial Instruments and Hedging - Schedule of Derivative Instruments Gain (Loss) (Details) (Cash Flow Hedging [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Other Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	$28.10		($15.50)
Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	2.2	[1]	-8.6	[1]
Selling and administrative expenses [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	0	[2]	0	[2]
Nickel and other raw material contracts [Member] | Other Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	-1.6		-8.4
Nickel and other raw material contracts [Member] | Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	-0.6	[1]	-5.4	[1]
Nickel and other raw material contracts [Member] | Selling and administrative expenses [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	0	[2]	0	[2]
Natural gas contracts [Member] | Other Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	-10.9		2.1
Natural gas contracts [Member] | Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	2.1	[1]	-2.3	[1]
Natural gas contracts [Member] | Selling and administrative expenses [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	0	[2]	0	[2]
Electricity contracts [Member] | Other Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	0.5		-0.1
Electricity contracts [Member] | Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0.4	[1]	-0.2	[1]
Electricity contracts [Member] | Selling and administrative expenses [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	0	[2]	0	[2]
Foreign Exchange Contract [Member] | Other Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion)	40.1		-9.1
Foreign Exchange Contract [Member] | Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0.3	[1]	-0.7	[1]
Foreign Exchange Contract [Member] | Selling and administrative expenses [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	$0	[2]	$0	[2]
[1]	The gains (losses) reclassified from accumulated OCI into income related to the effective portion of the derivatives are presented in cost of sales.
[2]	The gains (losses) recognized in income on derivatives related to the ineffective portion and the amount excluded from effectiveness testing are presented in selling and administrative expenses.

Derivative_Financial_Instrumen5

Derivative Financial Instruments and Hedging - Schedule of Derivatives Not Designated as Hedging Instruments Gain (Loss) (Details) (Foreign Exchange Contract [Member], Cost of Sales [Member], Not Designated as Hedging Instrument [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Foreign Exchange Contract [Member] | Cost of Sales [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	$5.20	($0.30)

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	$269.50	$1,026.80
Derivative financial instruments: Assets	0	0
Derivative financial instruments: Liabilities	0	0
Debt	1,589.10	2,027.80
Fair Value Measurements at Reporting Date Using Significant Observable Inputs (Level 2)
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Derivative financial instruments: Assets	59.9	4.3
Derivative financial instruments: Liabilities	27	21.6
Debt	26.9	44.8
Total Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	269.5	1,026.80
Derivative financial instruments: Assets	59.9	4.3
Derivative financial instruments: Liabilities	27	21.6
Debt	1,526.90	1,947.30
Fair Value Measurements at Reporting Date Using Total Estimated Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	269.5	1,026.80
Derivative financial instruments: Assets	59.9	4.3
Derivative financial instruments: Liabilities	27	21.6
Debt	$1,616	$2,072.60

Recovered_Sheet2

Fair Value Of Financial Instruments - Narrative (Details)	Dec. 31, 2013	Dec. 31, 2014	Aug. 15, 2014
Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	4.25%
Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014 [Member] | Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	4.25%
Allegheny Technologies $350 million 9.375% Senior Notes due 2019 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	9.38%	9.38%
Allegheny Technologies $350 million 9.375% Senior Notes due 2019 [Member] | Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage		9.38%
Allegheny Technologies $500 million 5.95% Senior Notes due 2021 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	5.95%	5.95%
Allegheny Technologies $500 million 5.95% Senior Notes due 2021 [Member] | Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage		5.95%
Allegheny Technologies $500 million 5.875% Senior Notes due 2023 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	5.88%		6.13%
Allegheny Technologies $500 million 5.875% Senior Notes due 2023 [Member] | Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	5.88%
Allegheny Ludlum 6.95% Debentures due 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage	6.95%	6.95%
Allegheny Ludlum 6.95% Debentures due 2025 [Member] | Fair Value Measurements at Reporting Date Using Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate stated percentage		6.95%

Pension_Plans_and_Other_Postre2

Pension Plans and Other Postretirement Benefits - Narrative (Details) (USD $)	12 Months Ended			3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected Retirement Benefit Expense In Next 12 months	$77
Defined contribution plan- Company contribution (percent)	6.50%
Defined contribution plan- Company matching contribution (percent)	3.00%
Other postretirement benefit costs for a defined contribution plan	21.9	24.3	23.8
Projected future contributions to VEBA trusts	16
US Qualified Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of total assets	96.00%
Number of shares of equity securities issued by employer included in plan assets	3
Fair value of employer equity securities included in plan assets	102.7	105.3
Dividends on employer stock received by plan	2.1	2.1
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected Retirement Benefit Expense In Next 12 months	37
One-time, voluntary lump sum payments	52
Benefit obligation increase for changes in mortality assumptions	90
Weighted average life expectancy	18 years
Average remaining service period	10 years
Accumulated benefit obligation	2,917.30	2,621.80
Fair value of transfers from level 1 to level 2		203
Expected long-term rate of return on assets	8.25%	8.25%	8.50%
Actual return on plan assets	6.50%	14.30%	8.00%	12.20%	0.30%
Fair value of plan assets	2,204.40	2,329.80	2,220
Other Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Estimated employer contributions in next 12 months	10
Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Projected Retirement Benefit Expense In Next 12 months	40
Assumed increase in per capita cost of covered benefits in next 12 months	8.00%
Assumed ultimate health care cost trend rate	5.00%
Year that ultimate trend rate is reached	2028
Expected long-term rate of return on assets	8.30%	8.30%	8.30%
Fair value of plan assets	2.9	4	6.3
Private equity [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	134.7	94.5
Fair Value, Inputs, Level 3 [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	809.7	655.3	340.2
Fair Value, Inputs, Level 3 [Member] | Private equity [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	134.7	94.5	85.5
Fair Value, Inputs, Level 3 [Member] | Private equity [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	2.9
Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other postretirement benefit costs for a defined contribution plan	$2.60	$4.60
Forecast [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term rate of return on assets						8.00%
Forecast [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term rate of return on assets						4.00%
MultiemployerPlan1 [Member] | Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percent of Current Year Contributions to Plan that Company Contributions Exceed		5.00%

Pension_Plans_and_Other_Postre3

Pension Plans and Other Postretirement Benefits (Details 1) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	$29.40	$39	$35
Interest cost on benefits earned in prior years	133.6	122.8	132.4
Expected return on plan assets	-184.2	-176	-181.4
Amortization of prior service cost (credit)	2.3	3	6.4
Amortization of net actuarial loss	74	111.8	105.2
Curtailment (gain) loss	0.5	0	0
Termination benefits	0.3	4.8	0
Total retirement benefit expense	55.9	105.4	97.6
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the year	2.9	3.2	3.1
Interest cost on benefits earned in prior years	24	22.4	26.1
Expected return on plan assets	-0.3	-0.5	-0.8
Amortization of prior service cost (credit)	-3	-18.2	-18.2
Amortization of net actuarial loss	14.1	17.2	14.6
Curtailment (gain) loss	-25.5	0	0
Termination benefits	0	1.3	0
Total retirement benefit expense	$12.20	$25.40	$24.80

Pension_Plans_and_Other_Postre4

Pension Plans and Other Postretirement Benefits (Details 2)	12 Months Ended						0 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Oct. 31, 2013	Oct. 29, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.15%	[1]			5.00%	[1]
Expected long-term rate of return on assets	8.25%		8.25%		8.50%
Pension Benefits [Member] | Benefit changes [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate							4.95%	4.25%
Pension Benefits [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.25%	[1]
Rate of increase in future compensation levels	3.00%		3.00%		3.00%
Pension Benefits [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.95%	[1]
Rate of increase in future compensation levels	3.50%		3.50%		4.50%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.15%	[1]	4.25%	[1]	5.00%	[1]
Rate of increase in future compensation levels	0.00%		0.00%		0.00%
Expected long-term rate of return on assets	8.30%		8.30%		8.30%
[1]	Pension expense for 2013 was initially measured at a 4.25% discount rate. The U.S. Plan was remeasured using a 4.95% discount rate as of October 31, 2013, following the sale of the tungsten materials business.

Pension_Plans_and_Other_Postre5

Pension Plans and Other Postretirement Benefits (Details 3)	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.25%	5.15%
Pension Benefits [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of increase in future compensation levels	3.00%	3.00%
Pension Benefits [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of increase in future compensation levels	3.50%	3.50%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.10%	5.15%
Rate of increase in future compensation levels	0.00%	0.00%

Pension_Plans_and_Other_Postre6

Pension Plans and Other Postretirement Benefits (Details 4) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$2,698.20	$2,952
Service cost	29.4	39	35
Interest cost	133.6	122.8	132.4
Benefits paid	-269.9	-195.6
Subsidy paid	0	0
Participant contributions	0.3	0.1
Effect of currency rates	-4.9	0.8
Net actuarial (gains) losses - discount rate change	288.5	-280.4
Net actuarial (gains) losses - other	78.4	54.7
Plan curtailments	0	0
Plan settlements	0	0
Special termination benefits	0.3	4.8
Benefit obligation at end of year	2,953.90	2,698.20	2,952
Other Postretirement Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	506.7	574.3
Service cost	2.9	3.2	3.1
Interest cost	24	22.4	26.1
Benefits paid	-54.3	-52.9
Subsidy paid	1	1.2
Participant contributions	0	0
Effect of currency rates	0	0
Net actuarial (gains) losses - discount rate change	39.5	-36.9
Net actuarial (gains) losses - other	-19.5	-5.9
Plan curtailments	-7.2	0
Plan settlements	-27	0
Special termination benefits	0	1.3
Benefit obligation at end of year	$466.10	$506.70	$574.30

Pension_Plans_and_Other_Postre7

Pension Plans and Other Postretirement Benefits (Details 5) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$2,329.80	$2,220
Actual returns on plan assets and plan expenses	136.8	293.8
Employer contributions	11.5	10.7
Participant contributions	0.3	0.1
Effect of currency rates	-4.1	0.8
Benefits paid	-269.9	-195.6
Fair value of plan assets at end of year	2,204.40	2,329.80
Other Postretirement Benefits [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	4	6.3
Actual returns on plan assets and plan expenses	-0.9	-0.9
Employer contributions	0	0
Participant contributions	0	0
Effect of currency rates	0	0
Benefits paid	-0.2	-1.4
Fair value of plan assets at end of year	$2.90	$4

Pension_Plans_and_Other_Postre8

Pension Plans and Other Postretirement Benefits (Details 6) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	$0	$5.10
Current liabilities	-10.2	-5.3
Noncurrent liabilities	-739.3	-368.2
Total amount recognized	-749.5	-368.4
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	0	0
Current liabilities	-47.3	-60.3
Noncurrent liabilities	-415.8	-442.4
Total amount recognized	($463.10)	($502.70)

Pension_Plans_and_Other_Postre9

Pension Plans and Other Postretirement Benefits (Details 7) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Amortization of net actuarial loss	($88.10)	($129)	($119.80)
Amortization to net income of net prior service cost (credit)	0.7	15.2	11.8
Remeasurements	424.5	-384.9	272.7
Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Beginning of year accumulated other comprehensive loss	-1,016.40	-1,474.70
Amortization of net actuarial loss	74	111.8
Amortization to net income of net prior service cost (credit)	2.3	3
Remeasurements	-412	343.5
End of year accumulated other comprehensive loss	-1,352.10	-1,016.40
Net change in accumulated other comprehensive loss	-335.7	458.3
Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Beginning of year accumulated other comprehensive loss	-151.5	-191.9
Amortization of net actuarial loss	14.1	17.2
Amortization to net income of net prior service cost (credit)	-3	-18.2
Remeasurements	-12.5	41.4
End of year accumulated other comprehensive loss	-152.9	-151.5
Net change in accumulated other comprehensive loss	($1.40)	$40.40

Recovered_Sheet3

Pension Plans and Other Postretirement Benefits (Details 8) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost) credit	$4.90	$7.70
Net actuarial loss	-1,347.20	-1,008.70
Accumulated other comprehensive loss	-1,352.10	-1,016.40	-1,474.70
Deferred tax effect	-514.7	-390.7
Accumulated other comprehensive loss, net of tax	-837.4	-625.7
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service (cost) credit	11.8	8.7
Net actuarial loss	-141.1	-142.8
Accumulated other comprehensive loss	-152.9	-151.5	-191.9
Deferred tax effect	-58.8	-58.3
Accumulated other comprehensive loss, net of tax	($94.10)	($93.20)

Recovered_Sheet4

Pension Plans and Other Postretirement Benefits (Details 9) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	$6.20
Amortization of net actuarial loss	75.2
Amortization of accumulated other comprehensive loss	81.4
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	1.3
Amortization of net actuarial loss	60.5
Amortization of accumulated other comprehensive loss	61.8
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	4.9
Amortization of net actuarial loss	14.7
Amortization of accumulated other comprehensive loss	$19.60

Recovered_Sheet5

Pension Plans and Other Postretirement Benefits (Details 10) (Pension Benefits [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$2,953.90	$2,619.60
Accumulated benefit obligation	2,917.30	2,545.40
Fair value of plan assets	$2,204.40	$2,246.10

Recovered_Sheet6

Pension Plans and Other Postretirement Benefits (Details 14) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Pension Benefits [Member]
Defined Benefit Plan Expected Future Benefit Payments [Abstract]
2015	$195.40
2016	195.4
2017	195.1
2018	195.4
2019	195.1
2020-2024	967.7
Other Postretirement Benefits [Member]
Defined Benefit Plan Expected Future Benefit Payments [Abstract]
2015	51.3
2016	44.7
2017	42.6
2018	40.4
2019	38.3
2020-2024	154.7
Medicare Part D Subsidy [Abstract]
2015	1.1
2016	1.1
2017	1.1
2018	1.1
2019	1.1
2020-2024	$4.70

Recovered_Sheet7

Pension Plans and Other Postretirement Benefits (Details 22) (Other Postretirement Benefits [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Effect on total of service and interest cost components, One Percentage Point Increase	$0.50
Effect on total of service and interest cost components, One Percentage Point Decrease	-0.5
Effect on other postretirement benefit obligation, One Percentage Point Increase	11.1
Effect on other postretirement benefit obligation, One Percentage Point Decrease	($9.70)

Recovered_Sheet8

Pension Plans and Other Postretirement Benefits (Details 11) (USD $)	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
In Millions, unless otherwise specified
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	$2,204.40		$2,329.80		$2,220
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	409.5		362.5
Significant Observable Inputs (Level 2) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	985.2		1,312
Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	809.7		655.3		340.2
Equity Securities: ATI common stock [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	102.7		105.3
Equity Securities: ATI common stock [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	102.7		105.3
Equity Securities: ATI common stock [Member] | Significant Observable Inputs (Level 2) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0		0
Equity Securities: ATI common stock [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0		0
Equity Securities: Other U.S. equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of co-mingled funds comprised of large-cap investments	90.00%		90.00%
Percentage of co-mingled funds comprised of small-cap investments	10.00%		10.00%
Equity Securities: Other U.S. equities [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	673.8	[1]	746	[1]
Equity Securities: Other U.S. equities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	306.1	[1]	257.2	[1]
Equity Securities: Other U.S. equities [Member] | Significant Observable Inputs (Level 2) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	367.7	[1]	488.8	[1]
Equity Securities: Other U.S. equities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	[1]	0	[1]
Equity Securities: International equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of co-mingled funds comprised of developed countries investments	90.00%		80.00%
Percentage of co-mingled funds comprised of emerging market investments	10.00%		20.00%
Equity Securities: International equities [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	238.2	[2]	311	[3]
Equity Securities: International equities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	[2]	0	[3]
Equity Securities: International equities [Member] | Significant Observable Inputs (Level 2) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	238.2	[2]	311	[3]
Equity Securities: International equities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	[2]	0	[3]
Fixed income and cash equivalents [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	383.5	[4]	508	[4]
Fixed income and cash equivalents [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0.7	[4]	0	[4]
Fixed income and cash equivalents [Member] | Significant Observable Inputs (Level 2) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	373.9	[4]	507.2	[4]
Fixed income and cash equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	8.9	[4]	0.8	[4]	1.4
Floating rate [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	392.3	[4]	294.5	[4]
Floating rate [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	[4]	0	[4]
Floating rate [Member] | Significant Observable Inputs (Level 2) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	[4]	0	[4]
Floating rate [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	392.3	[4]	294.5	[4]	0
Private equity [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	134.7		94.5
Private equity [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0		0
Private equity [Member] | Significant Observable Inputs (Level 2) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0		0
Private equity [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	134.7		94.5		85.5
Hedge funds [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	122.6		139.7
Hedge funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0		0
Hedge funds [Member] | Significant Observable Inputs (Level 2) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0		0
Hedge funds [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	122.6		139.7		148.9
Real estate and other [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	156.6		130.8
Real estate and other [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0		0
Real estate and other [Member] | Significant Observable Inputs (Level 2) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	5.4		5
Real estate and other [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	$151.20		$125.80		$104.40
[1]	Includes investments in commingled funds that invest in U.S. equity securities, comprised of approximately 90% large-cap U.S. companies and 10% small-cap U.S. companies.
[2]	Includes investments in commingled funds that invest in non-U.S. equity securities, comprised of approximately 90% developed countries and 10% emerging market economies.
[3]	Includes investments in commingled funds that invest in non-U.S. equity securities, comprised of approximately 80% developed countries and 20% emerging market economies.
[4]	Global debt securities include both fixed interest rate and floating interest rate instruments. These are comprised of actively managed investments which include U.S. government and U.S. government agency securities, foreign government securities, corporate bonds, mortgage-backed securities and other debt securities, and include both investment grade and non-investment grade debt, public and private debt, and secured and unsecured debt investments. To mitigate risk, investment managers have limitations regarding the amount of investment in particular securities and the credit quality of such investments.

Recovered_Sheet9

Pension Plans and Other Postretirement Benefits (Details 12) (Pension Benefits [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$2,329.80		$2,220
Net Realized and Unrealized Gains (Losses)	136.8		293.8
Fair value of plan assets at end of year	2,204.40		2,329.80
Fixed income and cash equivalents [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	383.5	[1]	508	[1]
Floating rate [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	392.3	[1]	294.5	[1]
Private equity [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	134.7		94.5
Hedge funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	122.6		139.7
Real estate and other [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	156.6		130.8
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	655.3		340.2
Net Realized and Unrealized Gains (Losses)	43.4		39.6
Net Purchases, Issuances and Settlements	111		275.5
Net Transfers Into (Out Of) Level 3	0		0
Fair value of plan assets at end of year	809.7		655.3
Significant Unobservable Inputs (Level 3) [Member] | Fixed income and cash equivalents [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.8	[1]	1.4
Net Realized and Unrealized Gains (Losses)	0.1		0.1
Net Purchases, Issuances and Settlements	8		-0.7
Net Transfers Into (Out Of) Level 3	0		0
Fair value of plan assets at end of year	8.9	[1]	0.8	[1]
Significant Unobservable Inputs (Level 3) [Member] | Floating rate [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	294.5	[1]	0
Net Realized and Unrealized Gains (Losses)	4.6		5.4
Net Purchases, Issuances and Settlements	93.2		289.1
Net Transfers Into (Out Of) Level 3	0		0
Fair value of plan assets at end of year	392.3	[1]	294.5	[1]
Significant Unobservable Inputs (Level 3) [Member] | Private equity [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	94.5		85.5
Net Realized and Unrealized Gains (Losses)	19.1		3.9
Net Purchases, Issuances and Settlements	21.1		5.1
Net Transfers Into (Out Of) Level 3	0		0
Fair value of plan assets at end of year	134.7		94.5
Significant Unobservable Inputs (Level 3) [Member] | Hedge funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	139.7		148.9
Net Realized and Unrealized Gains (Losses)	5.9		13.8
Net Purchases, Issuances and Settlements	-23		-23
Net Transfers Into (Out Of) Level 3	0		0
Fair value of plan assets at end of year	122.6		139.7
Significant Unobservable Inputs (Level 3) [Member] | Real estate and other [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	125.8		104.4
Net Realized and Unrealized Gains (Losses)	13.7		16.4
Net Purchases, Issuances and Settlements	11.7		5
Net Transfers Into (Out Of) Level 3	0		0
Fair value of plan assets at end of year	$151.20		$125.80
[1]	Global debt securities include both fixed interest rate and floating interest rate instruments. These are comprised of actively managed investments which include U.S. government and U.S. government agency securities, foreign government securities, corporate bonds, mortgage-backed securities and other debt securities, and include both investment grade and non-investment grade debt, public and private debt, and secured and unsecured debt investments. To mitigate risk, investment managers have limitations regarding the amount of investment in particular securities and the credit quality of such investments.

Recovered_Sheet10

Pension Plans and Other Postretirement Benefits (Details 13) (Pension Benefits [Member])	12 Months Ended
	Dec. 31, 2014
U.S. equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations range, Minimum	18.00%
Target asset allocations range, Maximum	40.00%
International equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations range, Minimum	7.00%
Target asset allocations range, Maximum	17.00%
Global debt securities and cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations range, Minimum	35.00%
Target asset allocations range, Maximum	48.00%
Private equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations range, Minimum	0.00%	[1]
Target asset allocations range, Maximum	10.00%	[1]
Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations range, Minimum	0.00%	[1]
Target asset allocations range, Maximum	10.00%	[1]
Real estate and other [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations range, Minimum	0.00%	[1]
Target asset allocations range, Maximum	10.00%	[1]
Private Equity, Hedge Funds, and Real Estate and Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocations range, Minimum	18.00%
Target asset allocations range, Maximum	20.00%
[1]	Have a combined target allocation of 18% and a 20% limit.

Recovered_Sheet11

Pension Plans and Other Postretirement Benefits (Details 17) (Pension Benefits [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Multiemployer Plan Disclosure [Line Items]
Company Contributions	$4.70		$5		$5.60
Steelworkers Western Independent Shops Pension Plan [Member]
Multiemployer Plan Disclosure [Line Items]
EIN	900169564
Pension Plan Number	1
Pension Protection Act Zone Status	Green	[1]	Red	[1]
FIP / RP Status Pending / Implemented	NA	[2]
Company Contributions	1.1		1		1.3
Surcharge Imposed	No	[3]
Expiration Dates of Collective Bargaining Agreements	30-Jun-15
Boilermakers-Blacksmiths National Pension Trust [Member]
Multiemployer Plan Disclosure [Line Items]
EIN	486168020
Pension Plan Number	1
Pension Protection Act Zone Status	Yellow	[1]	Yellow	[1]
FIP / RP Status Pending / Implemented	Implemented	[2]
Company Contributions	2		2.2		2.4
Surcharge Imposed	No	[3]
Expiration Dates of Collective Bargaining Agreements	30-Sep-18
IAM National Pension Fund [Member]
Multiemployer Plan Disclosure [Line Items]
EIN	516031295
Pension Plan Number	2
Pension Protection Act Zone Status	Green	[1]	Green	[1]
FIP / RP Status Pending / Implemented	NA	[2]
Company Contributions	$1.60		$1.80		$1.90
Surcharge Imposed	No	[3]
Expiration Dates of Collective Bargaining Agreements, First Date	25-Feb-18	[4]
Expiration Dates of Collective-Bargaining Agreements, Last Date	14-Jul-19	[4]
[1]	The most recent Pension Protection Act Zone Status available for ATI’s fiscal years 2014 and 2013 is for plan years ending in calendar years 2013 and 2012, respectively. The zone status is based on information provided to ATI and other participating employers by each plan and is certified by the plan’s actuary. A plan in the “red” zone had been determined to be in “critical status”, based on criteria established by the Code, and is generally less than 65% funded. A plan in the “yellow” zone has been determined to be in “endangered status”, based on criteria established under the Code, and is generally less than 80% funded. A plan in the “green” zone has been determined to be neither in “critical status” nor in “endangered status”, and is generally at least 80% funded.
[2]	The “FIP / RP status Pending / Implemented” column indicates whether a Funding Improvement Plan, as required under the Code by plans in the “yellow” zone, or a Rehabilitation Plan, as required under the Code to be adopted by plans in the “red” zone, is pending or has been implemented as of the end of the plan year that ended in 2014.
[3]	The “Surcharge Imposed” column indicates whether ATI’s contribution rate for 2014 included an amount in addition to the contribution rate specified in the applicable collective bargaining agreement, as imposed by a plan in “critical status”, in accordance with the requirements of the Code.
[4]	The Company is party to five separate bargaining agreements that require contributions to this plan. Expiration dates of these collective bargaining agreements range between February 25, 2018 and July 14, 2019.

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	($713.20)		($1,029.40)
OCI before reclassifications	-270.3		236.1
Amounts reclassified from AOCI	52.1		80.1
Net current-period OCI	-218.2		316.2
Ending balance	-931.4		-713.2
Increase (Decrease) in Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	27.1		23.7
OCI before reclassifications	-2.1		3.4
Amounts reclassified from AOCI	0		0
Net current-period OCI	-2.1		3.4
Ending balance	25		27.1
Post- retirement benefit plans [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	-718.9		-1,030
OCI before reclassifications	-266.4		241.1
Amounts reclassified from AOCI	53.8	[1]	70	[1]
Net current-period OCI	-212.6		311.1
Ending balance	-931.5		-718.9
Increase (Decrease) in Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	0		0
OCI before reclassifications	0		0
Amounts reclassified from AOCI	0		0
Net current-period OCI	0		0
Ending balance	0		0
Currency translation adjustment [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	15.3		3.4
OCI before reclassifications	-32		10.4
Amounts reclassified from AOCI	0.5		1.5	[2]
Net current-period OCI	-31.5		11.9
Ending balance	-16.2		15.3
Increase (Decrease) in Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	27.1		23.7
OCI before reclassifications	-2.1		3.4
Amounts reclassified from AOCI	0	[3]	0	[3]
Net current-period OCI	-2.1		3.4
Ending balance	25		27.1
Unrealized holding gains on securities [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	0		-0.1
OCI before reclassifications	0		0.1
Amounts reclassified from AOCI	0	[3]	0	[3]
Net current-period OCI	0		0.1
Ending balance	0		0
Increase (Decrease) in Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	0		0
OCI before reclassifications	0		0
Amounts reclassified from AOCI	0		0
Net current-period OCI	0		0
Ending balance	0		0
Derivatives [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	-9.6		-2.7
OCI before reclassifications	28.1		-15.5
Amounts reclassified from AOCI	-2.2	[4]	8.6	[4]
Net current-period OCI	25.9		-6.9
Ending balance	16.3		-9.6
Increase (Decrease) in Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	0		0
OCI before reclassifications	0		0
Amounts reclassified from AOCI	0		0
Net current-period OCI	0		0
Ending balance	$0		$0
[1]	Amounts were included in net periodic benefit cost for pension and other postretirement benefit plans (see Note 11).
[2]	Amount was included in discontinued operations as part of the gain on sale of the tungsten materials business (see Note 3).
[3]	No amounts were reclassified to earnings.
[4]	Amounts were included in cost of goods sold in the period or periods the hedged item affects earnings (see Note 9).

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Income (Loss) (Details2) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization to net income of net prior service credits	($0.70)		($15.20)		($11.80)
Amortization of net actuarial loss	88.1		129		119.8
Cost of sales	-3,844.80		-3,790.90		-4,041.40
Income (loss) from continuing operations before income taxes	1.5		-154.8		232.3
Income tax provision (benefit)	-8.7		-63.6		72.4
Income (loss) from continuing operations	10.2		-91.2		159.9
Income (loss) from discontinued operations, net of tax	-0.6		252.8		7.9
Reclassification out of Accumulated Other Comprehensive Income [Member] | Post- retirement benefit plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization to net income of net prior service credits	0.7	[1]	15.2	[1]
Amortization of net actuarial loss	-88.1	[1]	-129	[1]
Income (loss) from continuing operations before income taxes	-87.4	[2]	-113.8	[2]
Income tax provision (benefit)	-33.6		-43.8
Income (loss) from continuing operations	-53.8		-70
Reclassification out of Accumulated Other Comprehensive Income [Member] | Currency translation adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) from continuing operations	-0.5	[2],[3]
Income (loss) from discontinued operations, net of tax			-1.5	[2],[3]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivatives [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) from continuing operations before income taxes	3.6	[2]	-14	[2]
Income tax provision (benefit)	1.4		-5.4
Income (loss) from continuing operations	2.2		-8.6
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivatives [Member] | Nickel and other raw material contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	-1	[4]	-8.8	[4]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivatives [Member] | Natural gas contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	3.4	[4]	-3.8	[4]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivatives [Member] | Electricity contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	0.7	[4]	-0.3	[4]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivatives [Member] | Foreign Exchange Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales	$0.50	[4]	($1.10)	[4]
[1]	Amounts are included in the computation of pension and other postretirement benefit expense, which is reported in both cost of goods sold and selling and administrative expenses. For additional information, see Note 11.
[2]	For pretax items, positive amounts are income and negative amounts are expense in terms of the impact to net income. Tax effects are presented in conformity with ATI’s presentation in the consolidated statements of operations.
[3]	Amount in 2014 is included in other income, net, and amount in 2013 is included in discontinued operations as part of the gain on sale of the tungsten materials business (see Note 3).
[4]	Amounts are included in cost of goods sold in the period or periods the hedged item affects earnings. For additional information, see Note 9.

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)	12 Months Ended			3 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2015
	plan
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Preferred stock, issued	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Additional General Disclosures [Abstract]
Number of share-based compensation plans	2
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted (shares)	675,000	576,000	394,000
Common stock shares available for future awards	1,600,000
Shares vested	18,000	333,000	343,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested beginning of the year (shares)	927,000	727,000	677,000
Granted (shares)	675,000	576,000	394,000
Vested (shares)	-18,000	-333,000	-343,000
Forfeited (shares)	-208,000	-43,000	-1,000
Nonvested end of the year (shares)	1,376,000	927,000	727,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Beginning balance (in dollars per share)	$36.90	$38.60	$36.40
Granted (in dollars per share)	$20.30	$16.40	$16.40
Vested (in dollars per share)	($1)	($16.40)	($14.10)
Forfeited (in dollars per share)	($8.40)	($1.70)	($0.10)
Ending balance (in dollars per share)	$47.80	$36.90	$38.60
Retained Earnings Note Disclosure [Abstract]
Undistributed earnings of investees accounted for under equity method	$12
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Income target attainment measurement period	3 years
Share based compensation expense	2.4	11.3	14
Unrecognized compensation expense	18.9
Performance Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense	10.3
TSR/TSRP Minimum Shares	0
TSR/TSRP Target Shares	789,000
TSR/TSRP Maximum Shares	1,580,000
PRSP 2014 [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted (shares)	492,773
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (shares)	492,773
LTSV 2014 [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted (shares)	113,827
Award vesting period	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (shares)	113,827
PRSP 2012 [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Forfeited (shares)	-171,083
TSRP 2012-2014 [Member] | Performance Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
TSR/TSRP Award Fair Value	8.8
Unrecognized compensation expense	0
TSR/TSRP Minimum Shares	0
TSR/TSRP Target Shares	186,000
TSR/TSRP Maximum Shares	373,000
TSRP 2013-2015 [Member] | Performance Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
TSR/TSRP Award Fair Value	11
Unrecognized compensation expense	3.7
TSR/TSRP Minimum Shares	0
TSR/TSRP Target Shares	309,000
TSR/TSRP Maximum Shares	618,000
TSR 2014-2016 [Member] | Performance Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Target share award level	319,955
TSR/TSRP Award Fair Value	9.9
Unrecognized compensation expense	6.6
TSR/TSRP Minimum Shares	0
TSR/TSRP Target Shares	294,000
TSR/TSRP Maximum Shares	589,000
TSR and TSRP Awards [Member] | Performance Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation expense	$9.80	$12.30	$19.20
Performance measurement period	3 years
Common stock shares available for future awards	1,850,000
Maximum [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period	5 years
Maximum [Member] | PRSP 2013 [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period	5 years
Maximum [Member] | TSR and TSRP Awards [Member] | Performance Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award multiplier	2
Minimum [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period	3 years
Minimum [Member] | PRSP 2014 [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period	3 years
Minimum [Member] | TSR and TSRP Awards [Member] | Performance Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award multiplier	0
Subsequent Event [Member] | TSRP 2012-2014 [Member] | Performance Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares vested				137,843
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Vested (shares)				-137,843

Schedule_of_Income_Tax_Provisi

Schedule of Income Tax Provision (Benefit) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Components Of Income Tax Expense Benefit Continuing Operations Abstract
Current: Federal	($47.90)	($127.50)	$82.30
Current: State	-4	-10.2	8.7
Current: Foreign	9.8	7.9	9
Total Current	-42.1	-129.8	100
Deferred: Federal	34.1	62.7	-27.6
Deferred: State	-0.2	4.6	0.1
Deferred: Foreign	-0.5	-1.1	-0.1
Total Deferred	33.4	66.2	-27.6
Income tax provision (benefit) from continuing operations	-8.7	-63.6	72.4
Income tax provision (benefit) from discontinued operations	-0.3	161.4	3.8
Total company income tax provision (benefit)	($9)	$97.80	$76.20

Reconciliation_of_Federal_Tax_

Reconciliation of Federal Tax Rate to Effective Tax Rate (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Taxes computed at the federal rate	$0.50	($54.20)	$81.30
State and local income taxes, net of federal tax benefit	-2	-11.8	0.6
Tax reserve adjustments	-0.5	-10.2	-0.4
Repatriation of foreign earnings	0.3	9.4	1.3
Valuation allowance	0.5	9.1	2.2
Adjustment to prior years’ taxes	0.1	-5.3	1.4
Foreign earnings taxed at different rate	-6.6	-2.5	-10.2
Manufacturing deduction	0	0	-7.1
Other	-1	1.9	3.3
Income tax provision (benefit) from continuing operations	($8.70)	($63.60)	$72.40

Income_Taxes_Deferred_Tax_Liab

Income Taxes Deferred Tax Liability not Recognized (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Income Tax Disclosure [Abstract]
Undistributed earnings of foreign subsidiaries	$181

Schedule_of_Income_Taxes_by_Re

Schedule of Income Taxes by Region (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
U.S.	($46.10)	($180)	$178.40
Non-U.S.	47.6	25.2	53.9
Income (loss) from continuing operations before income taxes	$1.50	($154.80)	$232.30

Schedule_of_Income_Taxes_Paid_

Schedule of Income Taxes Paid and Refunded (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes Paid, Net [Abstract]
Income Taxes Paid	$15.10	$21.40	$101.70
Income tax refunds received	-20.2	-18.3	-15.8
Income Taxes Paid (Received), Net, Total	-5.1	3.1	85.9
Income tax refund expected	60
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	76
Tax credit carryforwards	$33.50

Schedule_of_Deferred_Tax_Asset

Schedule of Deferred Tax Assets and Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Deferred income tax assets
Pensions	$251.80	$115.70
Postretirement benefits other than pensions	169	182.9
Federal and state net operating loss tax carryovers	122.7	32.2
Federal and state tax credits	53.6	42
Deferred compensation and other benefit plans	25.6	29.4
Self insurance reserves	10.1	10.1
Other items	79.1	79.5
Gross deferred income tax assets	711.9	491.8
Valuation allowance for deferred tax assets	-34.4	-33.9
Total deferred income tax assets	677.5	457.9
Deferred income tax liabilities
Bases of property, plant and equipment	579.5	488.1
Inventory valuation	111.7	66.5
Bases of amortizable intangible assets	75.5	67.1
Other items	53.9	46.3
Total deferred tax liabilities	820.6	668
Net deferred tax liability	($143.10)	($210.10)

Income_Tax_Valuation_Allowance

Income Tax Valuation Allowance (Details6) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Valuation Allowance [Line Items]
Valuation allowance for deferred tax assets	$34.40	$33.90
Federal [Member]
Valuation Allowance [Line Items]
Valuation allowance for deferred tax assets	2.3
State net operating loss carryforwards [Member]
Valuation Allowance [Line Items]
Valuation allowance for deferred tax assets	20.9
State tax credits [Member]
Valuation Allowance [Line Items]
Valuation allowance for deferred tax assets	10
State temporary differences [Member]
Valuation Allowance [Line Items]
Valuation allowance for deferred tax assets	1.2
State [Member]
Valuation Allowance [Line Items]
Operating loss carryforward period	20 years
Maximum tax benefit available per year amount	$5
Maximum tax benefit available per year percent of income	30.00%

Schedule_of_Changes_in_Unrecog

Schedule of Changes in Unrecognized Income Tax Benefits (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Beginning balance	$72.80	$29.20	$29.70
Increases in prior period tax positions	2	0.1	0.2
Decreases in prior period tax positions	-0.6	-5.8	-0.3
Expiration of the statute of limitations	-0.5	-0.7	-2
Settlements	-0.7	-8.6	-0.4
Interest and penalties, net	-0.3	-1.8	0.8
Ending balance	73.4	72.8	29.2
unrecognized tax benefit [Line Items]
Income tax penalties and interest accrued	4.4
Unrecognized tax benefits	73.4	72.8	29.2
Increases in current period tax positions	0.7	60.4	1.2
Unrecognized tax benefits that would impact effective tax rate	9
Unrecognized tax benefits that will be recognized within 12 months of year end	62
Temporary difference [Member]
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Ending balance	60.9	59.4
unrecognized tax benefit [Line Items]
Unrecognized tax benefits	$60.90	$59.40

Tax_Years_Subject_To_Examinati

Tax Years Subject To Examination (Details)	12 Months Ended
	Dec. 31, 2014
Internal Revenue Service IRS [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2013
Alabama Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2011
Illinois Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2011
North Carolina Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2010
Oregon Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2011
Pennsylvania Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2011
China Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2010
Germany Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2012
Poland Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2010
United Kingdom Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2011

Business_Segments_Narrative_De

Business Segments - Narrative (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total direct international sales	$1,607.50	$1,585.10	$1,705.70
Sales by U.S. operations to foreign countries	1,201.80	1,175.10	1,262.90
Inventory valuation reserve		55.5
LIFO-related net realizable value charge	-4.8	-29.4
Inventory valuation reserves	68.8	84.3
Closed company and other expense	21.2	14.2	18.5
Closed companies environmental costs	8	3.9	4.3
Closed companies insurance obligations	3.8
Other corporate expense	9.4	10.3	10.2
Closed companies real estate costs			4
Flat Rolled Products [Member]
Segment Reporting Information [Line Items]
Income (loss) from equity method investments	-8.9	-7.1	4.9
Inventory valuation reserve	23.2	20.5
High Performance Materials & Components [Member]
Segment Reporting Information [Line Items]
Inventory valuation reserves	10	35
STAL Precision Stainless Steel Company Limited [Member]
Segment Reporting Information [Line Items]
Joint venture ownership percentage	60.00%
Corporate Joint Venture [Member]
Segment Reporting Information [Line Items]
Equity method investment ownership percentage	50.00%
Revenue from related parties	$75.30	$95.90	$77.10
Corporate Joint Venture [Member] | VSMPO [Member]
Segment Reporting Information [Line Items]
Joint venture ownership percentage by unaffiliated entity	50.00%

Business_Segments_Details

Business Segments (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Sales	$1,047.50	$1,069.60	$1,119	$987.30	$915.30	$972.40	$1,056.80	$1,099	$4,223.40	$4,043.50	$4,666.90
External Sales [Member]
Segment Reporting Information [Line Items]
Sales									4,223.40	4,043.50	4,666.90
Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales									4,404.80	4,163.30	4,797
Operating Segments [Member] | Intersegment Sales [Member]
Segment Reporting Information [Line Items]
Sales									181.4	119.8	130.1
Operating Segments [Member] | External Sales [Member]
Segment Reporting Information [Line Items]
Sales									4,223.40	4,043.50	4,666.90
Operating Segments [Member] | High Performance Materials & Components [Member]
Segment Reporting Information [Line Items]
Sales									2,084.60	2,016.70	2,398.10
Operating Segments [Member] | High Performance Materials & Components [Member] | Intersegment Sales [Member]
Segment Reporting Information [Line Items]
Sales									77.8	71.9	84.1
Operating Segments [Member] | High Performance Materials & Components [Member] | External Sales [Member]
Segment Reporting Information [Line Items]
Sales									2,006.80	1,944.80	2,314
Operating Segments [Member] | Flat Rolled Products [Member]
Segment Reporting Information [Line Items]
Sales									2,320.20	2,146.60	2,398.90
Operating Segments [Member] | Flat Rolled Products [Member] | Intersegment Sales [Member]
Segment Reporting Information [Line Items]
Sales									103.6	47.9	46
Operating Segments [Member] | Flat Rolled Products [Member] | External Sales [Member]
Segment Reporting Information [Line Items]
Sales									$2,216.60	$2,098.70	$2,352.90

Business_Segments_Details8

Business Segments (Details8) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Segment Operating Profit Loss	$246.30	$164.40	$513.20
Corporate expenses	-44.2	-43	-68.4
Interest expense, net	-108.7	-65.2	-71.6
Restructuring costs	0	-67.5	0
Closed company and other expense	-21.2	-14.2	-18.5
Retirement Benefit Expense	-70.7	-129.3	-122.4
Income (loss) from continuing operations before income taxes	1.5	-154.8	232.3
Operating Segments [Member] | High Performance Materials & Components [Member]
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Segment Operating Profit Loss	289.6	209.1	385.4
Operating Segments [Member] | Flat Rolled Products [Member]
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Segment Operating Profit Loss	($43.30)	($44.70)	$127.80

Business_Segments_Details2

Business Segments (Details2) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Other Significant Reconciling Item [Line Items]
Depreciation and amortization	$176.80	$189.90	$194
Capital expenditures	225.7	612.7	382
Continuing Operations [Member]
Segment Reporting Other Significant Reconciling Item [Line Items]
Depreciation and amortization	176.6	180.6	181.4
Capital expenditures	225.7	607.8	372.5
Continuing Operations [Member] | High Performance Materials & Components [Member]
Segment Reporting Other Significant Reconciling Item [Line Items]
Depreciation and amortization	124.4	127.4	130
Capital expenditures	51.9	39.5	59.9
Continuing Operations [Member] | Flat Rolled Products [Member]
Segment Reporting Other Significant Reconciling Item [Line Items]
Depreciation and amortization	49.3	49.5	49.7
Capital expenditures	172.1	568.1	311.3
Continuing Operations [Member] | Corporate [Member]
Segment Reporting Other Significant Reconciling Item [Line Items]
Depreciation and amortization	2.9	3.7	1.7
Capital expenditures	$1.70	$0.20	$1.30

Business_Segments_Details3

Business Segments (Details3) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	$6,582.60	$6,898.50	$6,247.80
High Performance Materials & Components [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	3,555.80	3,452.20	3,720.70
Flat Rolled Products [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	2,601.60	2,320.90	1,857
Discontinued Operations [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	1.8	9.8	214
Corporate Prepaid Pension Cost [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	0	5.1	0
Corporate: Deferred Tax Assets [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	0	0	71.5
Corporate: Cash and cash equivalents and other [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Identifiable Assets	$423.40	$1,110.50	$384.60

Business_Segments_Details4

Business Segments (Details4) (USD $)	3 Months Ended										12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	$1,047.50		$1,069.60	$1,119	$987.30	$915.30		$972.40	$1,056.80	$1,099	$4,223.40		$4,043.50		$4,666.90
Identifiable Assets	6,582.60					6,898.50					6,582.60		6,898.50		6,247.80
Percent of total	100.00%					100.00%					100.00%		100.00%		100.00%
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable Assets	5,879.60					6,145.40					5,879.60		6,145.40		5,505
Percent of total	90.00%					89.00%					90.00%		89.00%		88.00%
United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable Assets	196.3					208					196.3		208		239.2
Percent of total	3.00%					3.00%					3.00%		3.00%		4.00%
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable Assets	280.5					258.1					280.5		258.1		276.2
Percent of total	4.00%					4.00%					4.00%		4.00%		4.00%
Luxembourg [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable Assets	81.8	[1]				145.9	[1]				81.8	[1]	145.9	[1]	48.3	[1]
Percent of total	1.00%	[1]				2.00%	[1]				1.00%	[1]	2.00%	[1]	1.00%	[1]
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable Assets	144.4					141.1					144.4		141.1		179.1
Percent of total	2.00%					2.00%					2.00%		2.00%		3.00%
External Sales [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											4,223.40		4,043.50		4,666.90
Percent of total											100.00%		100.00%		100.00%
External Sales [Member] | United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											2,615.90		2,458.40		2,961.10
Percent of total											62.00%		61.00%		63.00%
External Sales [Member] | United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											228.4		251.5		303.9
Percent of total											5.00%		6.00%		7.00%
External Sales [Member] | China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											249.6		237.7		255.4
Percent of total											6.00%		6.00%		5.00%
External Sales [Member] | Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											207.7		215.4		256
Percent of total											5.00%		5.00%		6.00%
External Sales [Member] | France [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											168.1		152.8		157
Percent of total											4.00%		4.00%		3.00%
External Sales [Member] | Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											147		141		134.9
Percent of total											3.00%		4.00%		3.00%
External Sales [Member] | Italy [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											160.7		132.3		136.1
Percent of total											4.00%		3.00%		3.00%
External Sales [Member] | Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											89.3		124.7		93.7
Percent of total											2.00%		3.00%		2.00%
External Sales [Member] | Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											76.5		54.9		49.3
Percent of total											2.00%		1.00%		1.00%
External Sales [Member] | Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales											$280.20		$274.80		$319.50
Percent of total											7.00%		7.00%		7.00%
[1]	Comprises assets held by the Company’s European Treasury Center operation.

Restructuring_Costs_Details

Restructuring Costs (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$0	$67.50	$0
Restructuring costs, net of tax	41.2		41.2
Restructuring costs, per share (in dollars per share)			$0.39
Long-lived asset impairment charges			55.1
Revision of estimates		-1	13.8
Severance and termination benefit costs			8.2
Restructuring Reserve	2		2
Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Revision of estimates			4.2
High Performance Materials & Components [Member]
Restructuring Cost and Reserve [Line Items]
Long-lived asset impairment charges			8
Severance and termination benefit costs			1.1
Number of employees affected by restructuring			75
High Performance Materials & Components [Member] | Benefit Termination [Member]
Restructuring Cost and Reserve [Line Items]
Severance and termination benefit costs			1.1
Albany, Oregon Standard-grade Titanium Sponge Facility [Member] | High Performance Materials & Components [Member]
Restructuring Cost and Reserve [Line Items]
Long-lived asset impairment charges			38.1
Revision of estimates			3.5
New Castle, Indiana Stainless Finishing Facility [Member] | Flat Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Long-lived asset impairment charges			6.3
Revision of estimates			0.3
Wallingford, Connecticut Stainless Finishing Facility [Member] | Flat Rolled Products [Member]
Restructuring Cost and Reserve [Line Items]
Long-lived asset impairment charges			2.7
Revision of estimates			0.4
Severance and termination benefit costs			1
Number of employees affected by restructuring			65
Wallingford, Connecticut Stainless Finishing Facility [Member] | Flat Rolled Products [Member] | Benefit Termination [Member]
Restructuring Cost and Reserve [Line Items]
Severance and termination benefit costs			$5

Redeemable_Noncontrolling_Inte1

Redeemable Noncontrolling Interest - Narrative (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Feb. 07, 2014
Noncontrolling Interest [Line Items]
Redeemable noncontrolling interest	$0
Redeemable noncontrolling interest	12.1	0
ATI Flowform [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest held by others			15.00%
Retained Earnings
Noncontrolling Interest [Line Items]
Redeemable noncontrolling interest	($0.30)

Per_Share_Information_Details

Per Share Information (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share Reconciliation [Abstract]
Income (loss) from continuing operations, net of tax	$19.90	$0	($3.80)	($18.10)	($83.80)	($28.40)	$3.70	$9.70	($2)	($98.80)	$150.50
Redeemable noncontrolling interest									-0.3	0	0
Redeemable noncontrolling interest									0
Effect of dilutive securities: 4.25% Convertible Notes due 2014									0	0	8.5
Numerator for diluted net income (loss) per common share - Income (loss) from continuing operations attributable to ATI after assumed conversions									($2.30)	($98.80)	$159
Denominator for basic net income per common share - weighted average shares (shares)	108,704,983	108,712,682	108,628,024	108,173,581	107,984,535	108,001,306	107,980,753	107,614,468	107,100,000	106,800,000	106,100,000
Effect of dilutive securities: Share-based compensation									0	0	900,000
Effect of dilutive securities: 4.25% Convertible Notes due 2014									0	0	9,600,000
Denominator for diluted net income per common share—adjusted weighted average shares and assumed conversions									107,100,000	106,800,000	116,600,000
Basic income (loss) from continuing operations attributable to ATI per common share (in dollars per share)	$0.18	$0	($0.03)	($0.17)	($0.79)	($0.27)	$0.04	$0.09	($0.02)	($0.93)	$1.42
Diluted income (loss) from continuing operations attributable to ATI per common share (in dollars per share)	$0.18	$0	($0.03)	($0.17)	($0.79)	($0.27)	$0.04	$0.09	($0.02)	($0.93)	$1.36
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share amount									4,700,000	10,000,000	0
Allegheny Technologies $402.5 million 4.25% Convertible Senior Notes due 2014 [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt instrument interest rate stated percentage					4.25%					4.25%

Financial_Information_for_Subs2

Financial Information for Subsidiary and Guarantor Parent - Narrative (Details) (Allegheny Ludlum 6.95% Debentures due 2025 [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
Allegheny Ludlum 6.95% Debentures due 2025 [Member]
Condensed Financial Statements, Captions [Line Items]
Debt instrument carrying amount	$150,000,000	$150,000,000
Debt instrument interest rate stated percentage	6.95%	6.95%

Financial_Information_for_Subs3

Financial Information for Subsidiary and Guarantor Parent (B.S.) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Millions, unless otherwise specified
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$269.50	$1,026.80	$304.60	$380.60
Accounts receivable, net	603.6	528.2
Intercompany notes receivable	0	0
Inventories, net	1,472.80	1,322.10
Prepaid expenses and other current assets	136.2	73.7
Total Current Assets	2,482.10	2,950.80
Property, plant and equipment, net	2,961.80	2,874.10
Cost in excess of net assets acquired	780.4	727.9
Intercompany notes receivable	0	0
Investments in subsidiaries	0	0
Other assets	358.3	345.7
Total Assets	6,582.60	6,898.50	6,247.80
Accounts payable	556.7	471.8
Accrued liabilities	323.2	315.8
Intercompany notes payable	0	0
Deferred income taxes	62.2	3.5
Short-term debt and current portion of long-term debt	17.8	419.9
Total Current Liabilities	959.9	1,211
Long-term debt	1,509.10	1,527.40
Intercompany notes payable	0	0
Accrued postretirement benefits	415.8	442.4
Pension liabilities	739.3	368.2
Deferred income taxes	80.9	206.6
Other long-term liabilities	156.2	148.2
Total Liabilities	3,861.20	3,903.80
Redeemable noncontrolling interest	12.1	0
Total Stockholders’ Equity	2,709.30	2,994.70	2,587.10	2,571.60
Total Liabilities and Stockholders’ Equity	6,582.60	6,898.50
Guarantor Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	2.2	3.6
Accounts receivable, net	0.1	0.3
Intercompany notes receivable	0	0
Inventories, net	0	0
Prepaid expenses and other current assets	63.7	26.2
Total Current Assets	66	30.1
Property, plant and equipment, net	2.2	2.9
Cost in excess of net assets acquired	0	0
Intercompany notes receivable	0	0
Investments in subsidiaries	6,149.40	6,170.80
Other assets	23.7	35.7
Total Assets	6,241.30	6,239.50
Accounts payable	4.5	3.1
Accrued liabilities	47.5	51.6
Intercompany notes payable	1,232.60	825.6
Deferred income taxes	62.2	3.5
Short-term debt and current portion of long-term debt	0.5	402.9
Total Current Liabilities	1,347.30	1,286.70
Long-term debt	1,350.60	1,350.80
Intercompany notes payable	0	0
Accrued postretirement benefits	0	0
Pension liabilities	675.5	323
Deferred income taxes	80.9	206.6
Other long-term liabilities	77.7	77.7
Total Liabilities	3,532	3,244.80
Redeemable noncontrolling interest	0
Total Stockholders’ Equity	2,709.30	2,994.70
Total Liabilities and Stockholders’ Equity	6,241.30	6,239.50
Subsidiary [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	13.8	13.5
Accounts receivable, net	209.1	179.4
Intercompany notes receivable	0	0
Inventories, net	387.7	295.5
Prepaid expenses and other current assets	13.2	6.5
Total Current Assets	623.8	494.9
Property, plant and equipment, net	1,545.10	1,397.50
Cost in excess of net assets acquired	126.6	112.1
Intercompany notes receivable	0	0
Investments in subsidiaries	37.7	37.7
Other assets	28	32
Total Assets	2,361.20	2,074.20
Accounts payable	302	310.5
Accrued liabilities	72	56.6
Intercompany notes payable	1,158.20	763.8
Deferred income taxes	0	0
Short-term debt and current portion of long-term debt	0.1	0.1
Total Current Liabilities	1,532.30	1,131
Long-term debt	150.3	150.4
Intercompany notes payable	200	200
Accrued postretirement benefits	153	179.7
Pension liabilities	6	5.6
Deferred income taxes	0	0
Other long-term liabilities	22.5	20.2
Total Liabilities	2,064.10	1,686.90
Redeemable noncontrolling interest	0
Total Stockholders’ Equity	297.1	387.3
Total Liabilities and Stockholders’ Equity	2,361.20	2,074.20
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	253.5	1,009.70
Accounts receivable, net	394.4	348.5
Intercompany notes receivable	2,390.80	1,589.40
Inventories, net	1,085.10	1,026.60
Prepaid expenses and other current assets	59.3	41
Total Current Assets	4,183.10	4,015.20
Property, plant and equipment, net	1,414.50	1,473.70
Cost in excess of net assets acquired	653.8	615.8
Intercompany notes receivable	200	200
Investments in subsidiaries	0	0
Other assets	306.6	278
Total Assets	6,758	6,582.70
Accounts payable	250.2	158.2
Accrued liabilities	203.7	207.6
Intercompany notes payable	0	0
Deferred income taxes	0	0
Short-term debt and current portion of long-term debt	17.2	16.9
Total Current Liabilities	471.1	382.7
Long-term debt	8.2	26.2
Intercompany notes payable	0	0
Accrued postretirement benefits	262.8	262.7
Pension liabilities	57.8	39.6
Deferred income taxes	0	0
Other long-term liabilities	56	50.3
Total Liabilities	855.9	761.5
Redeemable noncontrolling interest	12.1
Total Stockholders’ Equity	5,890	5,821.20
Total Liabilities and Stockholders’ Equity	6,758	6,582.70
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0
Accounts receivable, net	0	0
Intercompany notes receivable	-2,390.80	-1,589.40
Inventories, net	0	0
Prepaid expenses and other current assets	0	0
Total Current Assets	-2,390.80	-1,589.40
Property, plant and equipment, net	0	0
Cost in excess of net assets acquired	0	0
Intercompany notes receivable	-200	-200
Investments in subsidiaries	-6,187.10	-6,208.50
Other assets	0	0
Total Assets	-8,777.90	-7,997.90
Accounts payable	0	0
Accrued liabilities	0	0
Intercompany notes payable	-2,390.80	-1,589.40
Deferred income taxes	0	0
Short-term debt and current portion of long-term debt	0	0
Total Current Liabilities	-2,390.80	-1,589.40
Long-term debt	0	0
Intercompany notes payable	-200	-200
Accrued postretirement benefits	0	0
Pension liabilities	0	0
Deferred income taxes	0	0
Other long-term liabilities	0	0
Total Liabilities	-2,590.80	-1,789.40
Redeemable noncontrolling interest	0
Total Stockholders’ Equity	-6,187.10	-6,208.50
Total Liabilities and Stockholders’ Equity	($8,777.90)	($7,997.90)

Financial_Information_for_Subs4

Financial Information for Subsidiary and Guarantor Parent (I.S.) (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Sales	$1,047.50	$1,069.60	$1,119	$987.30	$915.30	$972.40	$1,056.80	$1,099	$4,223.40	$4,043.50	$4,666.90
Cost of sales									3,844.80	3,790.90	4,041.40
Selling and administrative expenses									272.5	276.4	321.6
Restructuring costs									0	67.5	0
Income (loss) before interest, other income and income taxes									106.1	-91.3	303.9
Interest expense, net									-108.7	-65.2	-71.6
Other income (expense) including equity in income of unconsolidated subsidiaries									4.1	1.7	0
Income (loss) from continuing operations before income taxes									1.5	-154.8	232.3
Income tax provision (benefit)									-8.7	-63.6	72.4
Income (loss) from continuing operations									10.2	-91.2	159.9
Income (loss) from discontinued operations, net of tax									-0.6	252.8	7.9
Net income	25.3	2.9	-0.7	-17.9	175.6	-32.2	6.6	11.6	9.6	161.6	167.8
Less: Net income attributable to noncontrolling interests									12.2	7.6	9.4
Net income (loss) attributable to ATI	22.1	-0.7	-4	-20	173.4	-33.8	4.4	10	-2.6	154	158.4
Guarantor Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Sales									0	0	0
Cost of sales									45.3	75.2	57
Selling and administrative expenses									103.9	124.3	144.2
Restructuring costs										1.1
Income (loss) before interest, other income and income taxes									-149.2	-200.6	-201.2
Interest expense, net									-111	-63.4	-60.7
Other income (expense) including equity in income of unconsolidated subsidiaries									261.7	109.2	494.2
Income (loss) from continuing operations before income taxes									1.5	-154.8	232.3
Income tax provision (benefit)									-8.7	-63.6	72.4
Income (loss) from continuing operations									10.2	-91.2	159.9
Income (loss) from discontinued operations, net of tax									-0.6	252.8	7.9
Net income									9.6	161.6	167.8
Less: Net income attributable to noncontrolling interests									0	0	0
Net income (loss) attributable to ATI									9.6	161.6	167.8
Subsidiary [Member]
Condensed Financial Statements, Captions [Line Items]
Sales									1,878	1,769.40	2,031.80
Cost of sales									1,874.80	1,748.80	1,888.20
Selling and administrative expenses									44	34.9	42.6
Restructuring costs										15.7
Income (loss) before interest, other income and income taxes									-40.8	-30	101
Interest expense, net									-44.9	-37.2	-10.5
Other income (expense) including equity in income of unconsolidated subsidiaries									1.1	0.9	-21.5
Income (loss) from continuing operations before income taxes									-84.6	-66.3	69
Income tax provision (benefit)									-29.3	-20	27.5
Income (loss) from continuing operations									-55.3	-46.3	41.5
Income (loss) from discontinued operations, net of tax									0	0	0
Net income									-55.3	-46.3	41.5
Less: Net income attributable to noncontrolling interests									0	0	0
Net income (loss) attributable to ATI									-55.3	-46.3	41.5
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Sales									2,345.40	2,274.10	2,635.10
Cost of sales									1,924.70	1,966.90	2,096.20
Selling and administrative expenses									124.6	117.2	134.8
Restructuring costs										50.7
Income (loss) before interest, other income and income taxes									296.1	139.3	404.1
Interest expense, net									47.2	35.4	-0.4
Other income (expense) including equity in income of unconsolidated subsidiaries									2.9	0.8	31.8
Income (loss) from continuing operations before income taxes									346.2	175.5	435.5
Income tax provision (benefit)									116.7	40.4	168.7
Income (loss) from continuing operations									229.5	135.1	266.8
Income (loss) from discontinued operations, net of tax									-0.6	252.8	7.9
Net income									228.9	387.9	274.7
Less: Net income attributable to noncontrolling interests									12.2	7.6	9.4
Net income (loss) attributable to ATI									216.7	380.3	265.3
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Sales									0	0	0
Cost of sales									0	0	0
Selling and administrative expenses									0	0	0
Income (loss) before interest, other income and income taxes									0	0	0
Interest expense, net									0	0	0
Other income (expense) including equity in income of unconsolidated subsidiaries									-261.6	-109.2	-504.5
Income (loss) from continuing operations before income taxes									-261.6	-109.2	-504.5
Income tax provision (benefit)									-87.4	-20.4	-196.2
Income (loss) from continuing operations									-174.2	-88.8	-308.3
Income (loss) from discontinued operations, net of tax									0.6	-252.8	-7.9
Net income									-173.6	-341.6	-316.2
Less: Net income attributable to noncontrolling interests									0	0	0
Net income (loss) attributable to ATI									($173.60)	($341.60)	($316.20)

Financial_Information_for_Subs5

Financial Information for Subsidiary and Guarantor Parent (Comp Inc.) (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$25.30	$2.90	($0.70)	($17.90)	$175.60	($32.20)	$6.60	$11.60	$9.60	$161.60	$167.80
Currency translation adjustment arising during the period									-33.6	15.3	14.3
Unrealized holding gain (loss) on securities									0	0.1	0
Unrealized holding gain (loss) on securities									0	0.1	0
Net derivative gain (loss) on hedge transactions									25.9	-6.9	-2.8
Pension and postretirement benefits									-212.6	311.1	-97.4
Other comprehensive income (loss), net of tax									-220.3	319.6	-85.9
Comprehensive income (loss)									-210.7	481.2	81.9
Less: Comprehensive income attributable to noncontrolling interest									10.1	11	11.3
Comprehensive income (loss) attributable to ATI									-220.8	470.2	70.6
Guarantor Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									9.6	161.6	167.8
Currency translation adjustment arising during the period									-33.6	15.3	14.3
Unrealized holding gain (loss) on securities									0	0.1	0
Net derivative gain (loss) on hedge transactions									25.9	-6.9	-2.8
Pension and postretirement benefits									-212.6	311.1	-97.4
Other comprehensive income (loss), net of tax									-220.3	319.6	-85.9
Comprehensive income (loss)									-210.7	481.2	81.9
Less: Comprehensive income attributable to noncontrolling interest									0	0	0
Comprehensive income (loss) attributable to ATI									-210.7	481.2	81.9
Subsidiary [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									-55.3	-46.3	41.5
Currency translation adjustment arising during the period									0	0	0
Unrealized holding gain (loss) on securities									0	0	0
Net derivative gain (loss) on hedge transactions									0	0	0
Pension and postretirement benefits									1.8	22	-18.1
Other comprehensive income (loss), net of tax									1.8	22	-18.1
Comprehensive income (loss)									-53.5	-24.3	23.4
Less: Comprehensive income attributable to noncontrolling interest									0	0	0
Comprehensive income (loss) attributable to ATI									-53.5	-24.3	23.4
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									228.9	387.9	274.7
Currency translation adjustment arising during the period									-33.6	15.3	14.3
Unrealized holding gain (loss) on securities									0	0.1	0
Net derivative gain (loss) on hedge transactions									0	0	0
Pension and postretirement benefits									-28.4	27.6	-5.1
Other comprehensive income (loss), net of tax									-62	43	9.2
Comprehensive income (loss)									166.9	430.9	283.9
Less: Comprehensive income attributable to noncontrolling interest									10.1	11	11.3
Comprehensive income (loss) attributable to ATI									156.8	419.9	272.6
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									-173.6	-341.6	-316.2
Currency translation adjustment arising during the period									33.6	-15.3	-14.3
Unrealized holding gain (loss) on securities									0	-0.1	0
Net derivative gain (loss) on hedge transactions									0	0	0
Pension and postretirement benefits									26.6	-49.6	23.2
Other comprehensive income (loss), net of tax									60.2	-65	8.9
Comprehensive income (loss)									-113.4	-406.6	-307.3
Less: Comprehensive income attributable to noncontrolling interest									0	0	0
Comprehensive income (loss) attributable to ATI									($113.40)	($406.60)	($307.30)

Financial_Information_for_Subs6

Financial Information for Subsidiary and Guarantor Parent (Cash Flows) (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Cash flows provided by (used in) operating activities	$55.90	$368.40	$427.50
Purchases of property, plant and equipment	-225.7	-612.7	-382
Net receipts (payments) on intercompany activity	0	0	0
Proceeds from sale of business, net of transaction costs	0	600.9	0
Purchases of businesses, net of cash acquired	-92.9	0	0
Asset disposals and other	2.4	0.8	3.3
Cash used in investing activities	-316.2	-11	-378.7
Issuances of long-term debt	0	500	0
Payments on long-term debt and capital leases	-414.9
Payments on long-term debt	-414.9	-17.1	-16.7
Net receipts (payments) on intercompany activity	0	0	0
Dividends paid to stockholders	-77.1	-76.9	-76.5
Other	-5	-58.3	-48.3
Cash provided by (used in) financing activities	-497	364.8	-124.8
Increase (decrease) in cash and cash equivalents	-757.3	722.2	-76
Guarantor Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Cash flows provided by (used in) operating activities	-66.9	-41.1	-52.3
Purchases of property, plant and equipment	-0.1	-0.2	-1.7
Net receipts (payments) on intercompany activity	0	0	0
Proceeds from sale of business, net of transaction costs		-7.9
Purchases of businesses, net of cash acquired	0
Asset disposals and other	0	0	0
Cash used in investing activities	-0.1	-8.1	-1.7
Issuances of long-term debt		500
Payments on long-term debt and capital leases	-397.9
Net receipts (payments) on intercompany activity	544.4	-366.7	156.5
Dividends paid to stockholders	-77.1	-76.9	-76.5
Other	-3.8	-9.1	-21.2
Cash provided by (used in) financing activities	65.6	47.3	58.8
Increase (decrease) in cash and cash equivalents	-1.4	-1.9	4.8
Subsidiary [Member]
Condensed Financial Statements, Captions [Line Items]
Cash flows provided by (used in) operating activities	-313.8	-50.4	43.9
Purchases of property, plant and equipment	-170.8	-564.8	-308.6
Net receipts (payments) on intercompany activity	0	0	0
Proceeds from sale of business, net of transaction costs		0
Purchases of businesses, net of cash acquired	0
Asset disposals and other	1.7	0.2	0.3
Cash used in investing activities	-169.1	-564.6	-308.3
Issuances of long-term debt		0
Payments on long-term debt and capital leases	-0.1
Net receipts (payments) on intercompany activity	483.3	615.5	147.9
Dividends paid to stockholders	0	0	0
Other	0	-0.1	-0.1
Cash provided by (used in) financing activities	483.2	615.4	147.8
Increase (decrease) in cash and cash equivalents	0.3	0.4	-116.6
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash flows provided by (used in) operating activities	436.6	484.2	435.9
Purchases of property, plant and equipment	-54.8	-47.7	-71.7
Net receipts (payments) on intercompany activity	-1,027.70	-248.8	-304.4
Proceeds from sale of business, net of transaction costs		608.8
Purchases of businesses, net of cash acquired	-92.9
Asset disposals and other	0.7	0.6	3
Cash used in investing activities	-1,174.70	312.9	-373.1
Issuances of long-term debt		0
Payments on long-term debt and capital leases	-16.9
Net receipts (payments) on intercompany activity	0	0	0
Dividends paid to stockholders	0	-24.3	0
Other	-1.2	-49.1	-27
Cash provided by (used in) financing activities	-18.1	-73.4	-27
Increase (decrease) in cash and cash equivalents	-756.2	723.7	35.8
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash flows provided by (used in) operating activities	0	-24.3	0
Purchases of property, plant and equipment	0	0	0
Net receipts (payments) on intercompany activity	1,027.70	248.8	304.4
Proceeds from sale of business, net of transaction costs		0
Purchases of businesses, net of cash acquired	0
Asset disposals and other	0	0	0
Cash used in investing activities	1,027.70	248.8	304.4
Issuances of long-term debt		0
Payments on long-term debt and capital leases	0
Net receipts (payments) on intercompany activity	-1,027.70	-248.8	-304.4
Dividends paid to stockholders	0	24.3	0
Other	0	0	0
Cash provided by (used in) financing activities	-1,027.70	-224.5	-304.4
Increase (decrease) in cash and cash equivalents	$0	$0	$0

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Leases, Operating [Abstract]
Rent expense	$22.40	$20.50	$22.50
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2015	19.2
2016	17.7
2017	15.3
2018	13.5
2019	8
Thereafter	24.3
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation, property, plant, and equipment	118
Accrual for Environmental Loss Contingencies [Abstract]
Accrual for environmental remediation obligations	17
Accrued environmental loss contingencies recorded in other current liabilities	9
Components of Environmental Loss Accrual [Abstract]
Federal Superfund and comparable state-managed sites	5
Formerly owned or operated sites	10
Owned or controlled sites at which Company operations have been discontinued	1
Sites utilized by the company in its ongoing operations	1
Reasonably possible amount by which current matters may exceed reserves	$11

Selected_Quarterly_Financial_D2

Selected Quarterly Financial Data (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Sales	$1,047.50	$1,069.60	$1,119	$987.30	$915.30	$972.40	$1,056.80	$1,099	$4,223.40	$4,043.50	$4,666.90
Gross Profit	121.9	97	89.5	70.2	11.3	53.1	87.7	100.5
Income (loss) from continuing operations attributable to ATI	19.9	0	-3.8	-18.1	-83.8	-28.4	3.7	9.7	-2	-98.8	150.5
Net income (loss)	25.3	2.9	-0.7	-17.9	175.6	-32.2	6.6	11.6	9.6	161.6	167.8
Net income (loss) attributable to ATI	$22.10	($0.70)	($4)	($20)	$173.40	($33.80)	$4.40	$10	($2.60)	$154	$158.40
Basic income (loss) from continuing operations attributable to ATI per common share (in dollars per share)	$0.18	$0	($0.03)	($0.17)	($0.79)	($0.27)	$0.04	$0.09	($0.02)	($0.93)	$1.42
Basic net income attributable to ATI per common share (in dollars per share)	$0.20	($0.01)	($0.03)	($0.19)	$1.62	($0.32)	$0.04	$0.09	($0.03)	$1.44	$1.49
Diluted income (loss) from continuing operations attributable to ATI per common share (in dollars per share)	$0.18	$0	($0.03)	($0.17)	($0.79)	($0.27)	$0.04	$0.09	($0.02)	($0.93)	$1.36
Diluted net income attributable to ATI per common share (in dollars per share)	$0.20	($0.01)	($0.03)	($0.19)	$1.62	($0.32)	$0.04	$0.09	($0.03)	$1.44	$1.43
Average shares outstanding (shares)	108,704,983	108,712,682	108,628,024	108,173,581	107,984,535	108,001,306	107,980,753	107,614,468	107,100,000	106,800,000	106,100,000

Selected_Quarterly_Financial_D3

Selected Quarterly Financial Data (Unaudited) - Narrative (Details) (USD $)	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2014
Unusual Or Infrequent Item [Line Items]
Restructuring costs, net of tax	$41.20	$41.20
Tungsten Materials Business [Member]
Unusual Or Infrequent Item [Line Items]
Gain on disposed operation net of tax		261.4
Iron Castings and Fabricated Components Businesses [Member]
Unusual Or Infrequent Item [Line Items]
Restructuring costs, net of tax	6.1	11.9	5.8
Iron Castings Business [Member]
Unusual Or Infrequent Item [Line Items]
Restructuring costs, net of tax				8.8
Other Postretirement Benefits [Member]
Unusual Or Infrequent Item [Line Items]
Settlements and curtailments gains					25.5
Settlements and curtailments gains net of tax					$18.40