Summary of Activity Related to Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Goodwill And Intangible Assets [Line Items]
Goodwill, Gross Carrying Amount Beginning Balance		$ 120,149
Goodwill, Accumulated Impairment Losses Beginning Balance	(304)
Goodwill, Net Carrying Amount Ending Balance	$ 119,845	$ 119,845

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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