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Summary of Significant Accounting Policies - Narrative (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2017
USD ($)
service_provider
active_license
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Adjustment impact $ (50,491) $ (97,431) $ (35,762)  
Active licenses | active_license 294      
Cable-ships and Submersibles        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Useful lives 35 years      
Minimum | Buildings and Leasehold Improvements        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Useful lives 5 years      
Minimum | Equipment, Furniture and Fixtures        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Useful lives 3 years      
Minimum | Plant and Transportation Equipment        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Useful lives 3 years      
Maximum | Buildings and Leasehold Improvements        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Useful lives 40 years      
Maximum | Equipment, Furniture and Fixtures        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Useful lives 15 years      
Maximum | Plant and Transportation Equipment        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Useful lives 20 years      
Marine Services        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Number of telecommunication providers | service_provider 60      
Marine Services | Minimum        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Contract term 5 years      
Installation contract term 1 month      
Marine Services | Maximum        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Contract term 7 years      
Installation contract term 5 months      
Error in Accounting for Certain Items Related to Purchase Accounting        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Adjustment impact   800 $ 700 $ (200)
Net adjustment amount   $ 1,300    
Licensing Agreements        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Renewal period 2 years 11 months 16 days      
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2016-01        
Error Corrections and Prior Period Adjustments Restatement [Line Items]        
Gain on investment $ 1,100