Acquisitions (Provisional Amount Of Goodwill Recognized) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2011		Dec. 31, 2010		Mar. 31, 2011 Whitehall Group [Member]
Business Acquisition [Line Items]
Fair value of previously held interest					$ 250,156
Consideration paid for the remaining shares in Whitehall					75,713
Less: Net identifiable assets and liabilities					(55,238)
Goodwill on acquisition (restated)	$ 1,068,378	[1]	$ 1,452,986	[1]	$ 270,631

[1] Restated