Goodwill And Other Intangible Assets (Goodwill And Intangible Assets) (Detail) (USD $)	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012	Dec. 31, 2011
Amortizing intangible assets
Gross carrying amount	$ 129,400,000	[1]	$ 129,500,000	[1]
Less: accumulated amortization	(62,500,000)	[1]	(58,500,000)	[1]
Amortizing intangible assets, net	66,800,000	[1]	71,000,000	[1]	41,700,000	44,500,000
Non-amortizing intangible assets
Non-amortizing intangible assets	66,000,000		66,100,000		66,200,000	66,200,000
Goodwill	824,014,000		824,707,000		714,800,000	714,800,000
Goodwill and other intangible assets	956,899,000		961,807,000		822,700,000	825,500,000
Trade Names [Member]
Non-amortizing intangible assets
Non-amortizing intangible assets	34,700,000		34,800,000
Pre-Qualifications [Member]
Non-amortizing intangible assets
Non-amortizing intangible assets	$ 31,300,000		$ 31,300,000

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