Reconciliation of Beginning and Ending Balances of Gross Unrecognized Tax Benefits (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits [Line Items]
Balance as of January 1,	$ 25,312	$ 20,266	$ 4,442
Additions based on tax positions related to the current year	3,855	7,231	54
Additions for tax positions of prior years	969	3	16
Additions for acquired uncertain tax benefits			16,670
Reductions for tax positions of prior years	(3,819)	(2,188)	(916)
Balance as of December 31,	$ 26,317	$ 25,312	$ 20,266