Annual report pursuant to Section 13 and 15(d)

Software Impairment (Details)

v3.8.0.1
Software Impairment (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Software impairment charge $ 0 $ 0 $ 29,839,000
Wireless, Internet, Video, Local Service, and Long Distance Customer Billing Systems      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Fair value of remaining capital expenditures     0
Software impairment charge     20,700,000
Internally Developed Machine-to-Machine Billing System      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Software impairment charge     7,100,000
User Management Software      
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]      
Software impairment charge     $ 1,000,000