Components of Contracts in Progress and Advance Billings on Contracts (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Contractors [Abstract]
Costs incurred less costs of revenue recognized	$ 91,401	$ 65,321
Revenues recognized less billings to customers	494,719	494,833
Contracts in Progress	586,120	560,154
Billings to customers less revenue recognized	476,747	394,352
Costs incurred less costs of revenue recognized	(164,479)	(152,656)
Advance Billings on Contracts	$ 312,268	$ 241,696