Balance sheet components - Accrued and other current liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Accrued and other current liabilities
Employee-related	$ 18,290		$ 17,420
Income and other taxes payable	4,188		3,720
Accrued warranty	685	$ 669	1,175	$ 1,160	$ 1,254	$ 1,751
Penalty payment derivative	389		389
Other accrued expenses	4,632		5,246
Accrued and other current liabilities	$ 28,184		$ 27,950