Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Net revenues	$ 71,532	$ 76,535	$ 137,031	$ 153,657
Professional Services
Disaggregation of Revenue [Line Items]
Net revenues	8,589	13,692	17,236	27,619
Transaction Services
Disaggregation of Revenue [Line Items]
Net revenues	2,268	3,689	6,512	6,070
Subscription Services
Disaggregation of Revenue [Line Items]
Net revenues	60,153	56,352	112,196	109,547
License
Disaggregation of Revenue [Line Items]
Net revenues	522	2,802	1,087	10,421
Americas
Disaggregation of Revenue [Line Items]
Net revenues	58,939	61,898	110,726	123,060
APAC
Disaggregation of Revenue [Line Items]
Net revenues	7,164	7,727	14,992	17,460
EMEA
Disaggregation of Revenue [Line Items]
Net revenues	5,429	6,910	11,313	13,137
Cloud
Disaggregation of Revenue [Line Items]
Net revenues	38,891	42,447	77,787	83,491
Cloud | Professional Services
Disaggregation of Revenue [Line Items]
Net revenues	3,884	4,984	7,809	9,145
Cloud | Transaction Services
Disaggregation of Revenue [Line Items]
Net revenues	1,321	1,474	3,296	2,781
Cloud | Subscription Services
Disaggregation of Revenue [Line Items]
Net revenues	33,686	35,989	66,682	71,565
Cloud | License
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Cloud | Americas
Disaggregation of Revenue [Line Items]
Net revenues	37,071	40,761	74,102	80,083
Cloud | APAC
Disaggregation of Revenue [Line Items]
Net revenues	0	0	0	0
Cloud | EMEA
Disaggregation of Revenue [Line Items]
Net revenues	1,820	1,686	3,685	3,408
Digital
Disaggregation of Revenue [Line Items]
Net revenues	12,131	15,003	25,108	27,755
Digital | Professional Services
Disaggregation of Revenue [Line Items]
Net revenues	2,118	2,736	4,229	7,272
Digital | Transaction Services
Disaggregation of Revenue [Line Items]
Net revenues	945	2,215	3,213	3,289
Digital | Subscription Services
Disaggregation of Revenue [Line Items]
Net revenues	8,546	9,251	16,979	16,253
Digital | License
Disaggregation of Revenue [Line Items]
Net revenues	522	801	687	941
Digital | Americas
Disaggregation of Revenue [Line Items]
Net revenues	10,603	12,637	21,843	23,574
Digital | APAC
Disaggregation of Revenue [Line Items]
Net revenues	915	1,019	2,043	1,577
Digital | EMEA
Disaggregation of Revenue [Line Items]
Net revenues	613	1,347	1,222	2,604
Messaging
Disaggregation of Revenue [Line Items]
Net revenues	20,510	19,085	34,136	42,411
Messaging | Professional Services
Disaggregation of Revenue [Line Items]
Net revenues	2,587	5,972	5,198	11,202
Messaging | Transaction Services
Disaggregation of Revenue [Line Items]
Net revenues	2	0	3	0
Messaging | Subscription Services
Disaggregation of Revenue [Line Items]
Net revenues	17,921	11,112	28,535	21,729
Messaging | License
Disaggregation of Revenue [Line Items]
Net revenues	0	2,001	400	9,480
Messaging | Americas
Disaggregation of Revenue [Line Items]
Net revenues	11,265	8,500	14,781	19,403
Messaging | APAC
Disaggregation of Revenue [Line Items]
Net revenues	6,249	6,708	12,949	15,883
Messaging | EMEA
Disaggregation of Revenue [Line Items]
Net revenues	$ 2,996	$ 3,877	$ 6,406	$ 7,125