Summary of Significant Accounting Policies - Schedule of Revenue Disaggregated by Revenue Type, Geographic Region and Customer (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Total revenue	$ 263,209	$ 244,108	$ 771,462	$ 730,046
Percentage of total revenue	100.00%	100.00%	100.00%	100.00%
Broadband/Cable/Satellite
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	56.00%	59.00%	57.00%	59.00%
Telecommunications
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	20.00%	18.00%	19.00%	18.00%
Other
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	24.00%	23.00%	24.00%	23.00%
Americas (principally the U.S.)
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	85.00%	86.00%	85.00%	87.00%
Europe, Middle East and Africa
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	12.00%	10.00%	11.00%	9.00%
Asia Pacific
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	3.00%	4.00%	4.00%	4.00%
Cloud and Related Solutions
Disaggregation Of Revenue [Line Items]
Total revenue	$ (231,418)	$ 217,527	$ 686,685	$ 654,027
Software and Services
Disaggregation Of Revenue [Line Items]
Total revenue	(19,518)	15,260	49,330	43,502
Maintenance
Disaggregation Of Revenue [Line Items]
Total revenue	$ (12,273)	$ 11,321	$ 35,447	$ 32,517