Discontinued Operations (Details) (Aluminum Extrusions Canada Business, USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended
Feb. 12, 2008	Mar. 31, 2013
Aluminum Extrusions Canada Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of business	$ 25.0
Charges for indemnifications under the purchase agreement related to environmental matters		5.2
Charges for indemnifications under the purchase agreement related to environmental matters, net of tax		$ 5.2

Pretax adjustment to an amount previously reported in discontinued operations that is directly related to the disposal of the component in a prior period. Examples of circumstances leading to such adjustments include the resolution of contingencies relating to the terms of the disposal transaction or relating to the operations of the component prior to its disposal, and the settlement of certain employee benefit plan obligations.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1012-107759

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1510-107760

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1020-107759

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