Balance sheet components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Prepaid taxes and taxes receivable	$ 4,130	$ 5,461
Transition services agreement receivable (see Note 6)	12,016	11,999
Deposits and other prepaid expenses	2,424	3,020
Other receivable	4,827	6,125
Prepaid expenses and other current assets	23,397	$ 26,605
Capital expenditures incurred but not yet paid	$ 1,500		$ 3,100