Components of Contracts in Progress and Advance Billings on Contracts (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Contractors [Abstract]
Costs incurred less costs of revenue recognized	$ 83,354	$ 65,321
Revenues recognized less billings to customers	540,576	494,833
Contracts in Progress	623,930	560,154
Billings to customers less revenue recognized	467,049	394,352
Costs incurred less costs of revenue recognized	(165,623)	(152,656)
Advance Billings on Contracts	$ 301,426	$ 241,696