Fair value measurement - reconciliation of changes in three financial liabilities measured at fair value on recurring (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Changes in Level 3 Financial Liabilities Related to Contingent Consideration [Roll Forward]
Beginning balance	$ 20,313	$ 51,196
Initial estimate upon acquisition	20,538	0
Payment	0	(18,880)
Revaluations	(7,418)	(11,982)
Translation adjustment	0	(21)
Ending balance	$ 33,433	$ 20,313