Significant Accounting Policies Additional Information (Detail)	9 Months Ended
	Sep. 30, 2012
Minimum
Significant Accounting Policies [Line Items]
Warranty term	9 months
Minimum | Certain construction contracts
Significant Accounting Policies [Line Items]
Warranty term	2 years
Maximum
Significant Accounting Policies [Line Items]
Warranty term	1 year
Maximum | Certain construction contracts
Significant Accounting Policies [Line Items]
Warranty term	10 years