Balance sheet components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Prepaid taxes and taxes receivable	$ 5,523	$ 5,461
Transition services agreement receivable (refer to Note 6)	11,609	11,999
Deposits and other prepaid expenses	2,714	3,020
Other receivable	4,075	6,125
Prepaid expenses and other current assets	23,921	$ 26,605
Capital expenditures incurred but not yet paid	$ 2,800		$ 1,100