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Commitments, Contingencies and Other Items (Details)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
USD ($)
patent
lawsuit
Mar. 31, 2019
USD ($)
lawsuit
Loss Contingencies [Line Items]    
Estimate of possible loss | $ $ 22,000 $ 22,000
Number of patents allegedly infringed (minimum) | patent 1  
Louisiana State Court    
Loss Contingencies [Line Items]    
Number of claims | lawsuit   2
Interexchange carriers | Subsidiaries of CenturyLink, Inc.    
Loss Contingencies [Line Items]    
Number of lawsuits (approximately) | lawsuit 100 100
Unfavorable Regulatory Action    
Loss Contingencies [Line Items]    
Estimate of possible loss | $ $ 100 $ 100