Employee Retirement Plans - Additional Information (Detail)	9 Months Ended
Sep. 30, 2012 MultiEmployerPensionPlan
Description of Multiemployer Plan	Company participates in 20 regional multi-employer pension plans, principally related to building trades; none of the plans are considered significant
Number of regional multi employer pension plan	20

Description of the nature of multiemployer plan benefits as well as who is covered by the benefits. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450702-114947

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 7

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=14450570&loc=SL14450678-114947

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Data Type:	xbrli:stringItemType
Balance Type:	na
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