Contingent Consideration Liability Measured at Fair Value on Recurring Basis using Significant Unobservable (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Fair Value Disclosures [Abstract]
Beginning Balance	$ 51,163	$ 72,046
Payment of contingent considerations on acquisitions	(4,899)	(7,651)
Expense (income) from fair value adjustments	3,178	(6,972)
Ending Balance	$ 49,442	$ 57,423

Fair value, as of the acquisition date, of potential payments under the contingent consideration arrangement including cash and shares.

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+ Details