Income taxes - Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
Federal	$ 4,774	$ 3,047	$ 2,589
State	709	(224)	2,757
Foreign	5,967	7,442	6,753
Deferred:
Federal	(3,986)	3,916	18,361
State	(1,375)	(694)	(206)
Foreign	(439)	16	(1,773)
Income tax expense	$ 5,650	$ 13,503	$ 28,481