Goodwill And Other Intangible Assets (Goodwill And Intangible Assets) (Detail) (USD $)										12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2012 Trade Names [Member]	Dec. 31, 2011 Trade Names [Member]	Dec. 31, 2012 Pre-Qualifications [Member]	Dec. 31, 2011 Pre-Qualifications [Member]	Dec. 31, 2012 Weighted Average [Member]	Dec. 31, 2011 Weighted Average [Member]
Goodwill And Other Intangible Assets [Line Items]
Gross carrying amount	$ 129,400,000	[1]	$ 95,800,000	[1]
Less: accumulated amortization	(58,500,000)	[1]	(51,300,000)	[1]
Amortizing intangible assets, net	70,900,000	[1]	44,500,000	[1]	36,000,000
Amortizing intangible assets, useful life										12 years	14 years
Non-amortizing intangible assets	66,200,000		66,200,000		34,900,000	34,900,000	34,900,000	31,300,000	31,300,000
Goodwill	820,341,000		714,760,000		525,600,000
Goodwill and other intangible assets	$ 957,441,000		$ 825,467,000		$ 596,500,000

[1] Consists principally of customer relationships, backlog, trade names and non-compete agreements with finite lives.