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Contract Costs - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Project	Sep. 30, 2011 Project
Long-term Contracts or Programs Disclosure [Line Items]
Percentage of pass-through costs included in revenue	58.20%	46.90%	46.00%	46.60%
Total revenue recorded in relation to orders change in projects			$ 1.7	$ 1.7
Number of projects orders changed			2	2
Total revenue recorded in relation to re-measure units and quantities within customer construction contract			6.6
Recognized contract losses from uncompleted contracts	(20.6)	(1.8)	(21.2)	(2.4)
Unfavorable reduction in gross margin due to contract loss from uncompleted contracts	$ 26.8	$ 1.8	$ 24.5	$ 2.4