Summary of Significant Accounting Policies - Schedule of Revenue Disaggregated by Revenue Type, Geographic Region and Customer (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue:
Total revenue	$ 1,046,487	$ 990,533	$ 996,810
Percentage of total revenue	100.00%	100.00%	100.00%
Broadband/Cable/Satellite
Revenue:
Percentage of total revenue	57.00%	58.00%	58.00%
Telecommunications
Revenue:
Percentage of total revenue	19.00%	19.00%	19.00%
Other
Revenue:
Percentage of total revenue	24.00%	23.00%	23.00%
Americas (principally the U.S.)
Revenue:
Percentage of total revenue	85.00%	86.00%	87.00%
Europe, Middle East and Africa
Revenue:
Percentage of total revenue	11.00%	10.00%	9.00%
Asia Pacific
Revenue:
Percentage of total revenue	4.00%	4.00%	4.00%
SaaS and Related Solutions
Revenue:
Total revenue	$ 926,290	$ 880,822	$ 896,164
Software and Services
Revenue:
Total revenue	72,818	63,239	52,364
Maintenance
Revenue:
Total revenue	$ 47,379	$ 46,472	$ 48,282