Revenue from Contracts with Customers - Concentration Risk (Details) - CenturyLink, Inc. - Customer Concentration Risk
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 27, 2020
Jun. 29, 2019
Jun. 27, 2020
Jun. 29, 2019
Dec. 31, 2019
Revenue from Contract with Customer Benchmark [Member]          
Concentration Risk [Line Items]          
Concentration risk, percentage 15.00% 17.00% 15.00% 15.00%  
Accounts Receivable          
Concentration Risk [Line Items]          
Concentration risk, percentage     19.00%   17.00%