Revenue, deferred revenue, and deferred commissions - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Payment terms on invoiced amounts		30 days
Deferred commissions	$ 11,118	$ 11,118		$ 10,307	$ 10,477
Percentage of deferred commissions to be recognized as commission expense in the next 12 months	49.00%	49.00%
Revenue recognized pertaining to amounts deferred as of Beginning of Period		$ 34,200
Revenue recognized pertaining to amounts deferred as of End of Period	$ 17,000		$ 29,400
Deferred revenue and backlog	$ 115,900	$ 115,900
Percentage of deferred revenue to be recognized over the next 12 months	66.00%	66.00%
Contract with Customer, Asset, before Allowance for Credit Loss	$ 4,700	$ 4,700			$ 4,300