Activity in Allowance for Doubtful Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance, beginning of period	$ 5,738		$ 2,732	$ 1,920
Provision (recovery) charged to general and administrative expense	(101)		3,116	1,171
Amounts written off, net of recoveries	(516)		(110)	(359)
Other	(278)	[1]
Balance, end of period	$ 4,843		$ 5,738	$ 2,732

[1] Amount includes amounts related to the ISD acquisition and the impact of foreign exchange movements in the allowance balance.