Annual report pursuant to Section 13 and 15(d)

Net Property and Equipment (Narrative) (Details)

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Net Property and Equipment (Narrative) (Details) - USD ($)
$ in Thousands
1 Months Ended 12 Months Ended
Nov. 30, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property, Plant and Equipment [Line Items]        
Cash payment $ 19,700 $ 0 $ 19,700 $ 0
Fair market value of IRU capacity $ 14,100      
Other Income (Expense)        
Property, Plant and Equipment [Line Items]        
Gain from adjustment to fair value     $ 3,100