Costs and Estimated Earnings on Uncompleted Contracts - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2013 Customer	Dec. 31, 2012 Customer
Contractors [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts, net of billings in excess of costs and estimated earnings	90.70%	86.50%
Number of significant customers	5	5