Income taxes - Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
Federal	$ 4,718	$ 4,774	$ 3,047
State	1,447	709	(224)
Foreign	5,983	5,967	7,442
Deferred:
Federal	6,262	(3,986)	3,916
State	(1,347)	(1,375)	(694)
Foreign	2,542	(439)	16
Income tax expense	$ 19,605	$ 5,650	$ 13,503