Goodwill And Other Intangible Assets (Goodwill And Intangible Assets) (Detail) (USD $)	Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012	Dec. 31, 2011
Amortizing intangible assets
Gross carrying amount	$ 141,200,000	[1]	$ 129,400,000	[1]
Less: accumulated amortization	(67,000,000)	[1]	(58,500,000)	[1]
Amortizing intangible assets, net	74,200,000	[1]	70,900,000	[1]	38,800,000	44,500,000
Non-amortizing intangible assets
Non-amortizing intangible assets	94,500,000		66,200,000		66,200,000	66,200,000
Goodwill	860,207,000		826,110,000		718,300,000	714,800,000
Goodwill and other intangible assets	1,028,908,000		963,210,000		823,300,000	825,500,000
Trade Names [Member]
Non-amortizing intangible assets
Non-amortizing intangible assets	34,900,000		34,900,000
Pre-Qualifications [Member]
Non-amortizing intangible assets
Non-amortizing intangible assets	$ 59,600,000		$ 31,300,000

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