Restructuring Charges, Net of Tax

No definition available.

Name:	ati_RestructuringChargesNetofTax
Namespace Prefix:	ati_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Restructuring Charges, Per Share

+ References

No definition available.

+ Details

Name:	ati_RestructuringChargesPerShare
Namespace Prefix:	ati_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

+ Details

Name:	us-gaap_AssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of the Increase or Decrease in the amount of the asset retirement obligation during the current period for changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)(4)

-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

+ Details

Name:	us-gaap_AssetRetirementObligationRevisionOfEstimate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of positions eliminated during the period as a result of restructuring activities.

+ References

No definition available.

+ Details

Name:	us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminated
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.P.3)

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140864-122747

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

+ Details

Name:	us-gaap_RestructuringCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_RestructuringCostAndReserveLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

+ Details

Name:	us-gaap_RestructuringReserve
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of expenses for special or contractual termination benefits provided to current employees involuntarily terminated under a benefit arrangement associated exit or disposal activities pursuant to an authorized plan. Excludes expenses related to one-time termination benefits, a discontinued operation or an asset retirement obligation.

+ References

+ Details

Name:	us-gaap_SeveranceCosts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	dei_EntityByLocationAxis=ati_AlbanyOregonStandardgradeTitaniumSpongeFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_EntityByLocationAxis=ati_NewCastleIndianaStainlessFinishingFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_EntityByLocationAxis=ati_WallingfordConnecticutStainlessFinishingFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=us-gaap_RestructuringChargesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ati_HighPerformanceMaterialsComponentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Restructuring Costs (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$ 0us-gaap_RestructuringCharges	$ 67.5us-gaap_RestructuringCharges	$ 0us-gaap_RestructuringCharges
Restructuring costs, net of tax	41.2ati_RestructuringChargesNetofTax		41.2ati_RestructuringChargesNetofTax
Restructuring costs, per share (in dollars per share)			$ 0.39ati_RestructuringChargesPerShare
Long-lived asset impairment charges			55.1us-gaap_AssetImpairmentCharges
Revision of estimates		(1.0)	13.8
Severance and termination benefit costs			8.2us-gaap_SeveranceCosts1
Restructuring Reserve	2us-gaap_RestructuringReserve		2us-gaap_RestructuringReserve
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			8.0
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			1.0
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			$ 5.0