XML 116 R102.htm IDEA: XBRL DOCUMENT v3.8.0.1

Tax Years Subject To Examination (Details)	12 Months Ended
	Dec. 31, 2017
Internal Revenue Service IRS [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2016
Pennsylvania Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2014
China Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2014
Poland [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2011
United Kingdom Tax [Member]
Income Tax Examination [Line Items]
Earliest Tax Year Open To Examination	2015

X

- Definition

The earliest tax year still open to audit by the income tax examination authorities

+ References

No definition available.

+ Details

Name:	ati_EarliestTaxYearOpenToExamination
Namespace Prefix:	ati_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

X

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_InternalRevenueServiceIRSMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=stpr_PA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=country_CN
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=country_PL
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=country_GB
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: