Employee Benefit Plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012
Employee Benefit Plans [Abstract]
Employer contribution to defined benefit pension plans	$ 3.0
Defined benefit pension plans, additional voluntary contribution	2.5
Expected contribution to defined benefit pension plans	6.0
Expected contribution to meet minimum required contributions	3.5
Additional voluntary contribution	2.5
Expected contribution to defined contribution retirement plans	$ 0.9

Defined benefit pension plan additional voluntary contribution

No definition available.

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- Definition

Defined benefit plan, additional voluntary contribution in current fiscal year

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

The employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan in the current fiscal period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Defined benefit plan, minimum required contributions in current fiscal year

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount the company expects to contribute to it's defined contribution retirement plan.

+ References

No definition available.

+ Details

Name:	atx_DefinedContributionRetirementPlanExpectedContributionInCurrentFiscalYear
Namespace Prefix:	atx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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Period Type:	duration

- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(3)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

+ Details

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Balance Type:	debit
Period Type:	duration