Other current liabilities - Summary of Other Current Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Payables And Accruals [Abstract]
Accrued expenses	$ 17,452	$ 15,002
Salaries, bonuses, commissions and related taxes payable	17,915	22,743
Other payables	4,227	3,091
Total	$ 39,594	$ 40,836