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, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue:
Total revenue	$ 990,533	$ 996,810	$ 875,059
Percentage of total revenue	100.00%	100.00%	100.00%
Broadband/Cable/Satellite
Revenue:
Percentage of total revenue	58.00%	58.00%	64.00%
Telecommunications
Revenue:
Percentage of total revenue	19.00%	19.00%	21.00%
Other
Revenue:
Percentage of total revenue	23.00%	23.00%	15.00%
Americas
Revenue:
Percentage of total revenue	86.00%	87.00%	85.00%
Europe, Middle East and Africa
Revenue:
Percentage of total revenue	10.00%	9.00%	10.00%
Asia Pacific
Revenue:
Percentage of total revenue	4.00%	4.00%	5.00%
Cloud and Related Solutions
Revenue:
Total revenue	$ 880,822	$ 896,164	$ 766,377
Software and Services
Revenue:
Total revenue	63,239	52,364	58,101
Maintenance
Revenue:
Total revenue	$ 46,472	$ 48,282	$ 50,581