Summary of Significant Accounting Policies - Schedule of Revenue Disaggregated by Revenue Type, Geographic Region and Customer (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]
Total revenue	$ 255,134	$ 240,321	$ 508,253	$ 485,938
Percentage of total revenue	100.00%	100.00%	100.00%	100.00%
Broadband/Cable/Satellite
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	58.00%	60.00%	58.00%	59.00%
Telecommunications
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	18.00%	18.00%	18.00%	18.00%
Other
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	24.00%	22.00%	24.00%	23.00%
Americas (principally the U.S.)
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	85.00%	87.00%	86.00%	88.00%
Europe, Middle East and Africa
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	11.00%	9.00%	10.00%	9.00%
Asia Pacific
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	4.00%	4.00%	4.00%	3.00%
Cloud and Related Solutions
Disaggregation Of Revenue [Line Items]
Total revenue	$ 228,248	$ 214,280	$ 455,267	$ 436,500
Software and Services
Disaggregation Of Revenue [Line Items]
Total revenue	15,033	15,036	29,812	28,242
Maintenance
Disaggregation Of Revenue [Line Items]
Total revenue	$ 11,853	$ 11,005	$ 23,174	$ 21,196