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Employee Benefit Plans, Narrative (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Employee benefits      
Description of defined contribution plan TDS sponsors a qualified noncontributory defined contribution pension plan. The plan provides benefits for certain employees of TDS Corporate, TDS Telecom and U.S. Cellular. Under this plan, pension costs are calculated separately for each participant and are funded annually. Total pension costs were $16 million, $17 million and $16 million in 2017, 2016 and 2015, respectively. In addition, TDS sponsors a defined contribution retirement savings plan (401(k)) plan. Total costs incurred from TDS’ contributions to the 401(k) plan were $27 million in 2017 and 2016, and $26 million in 2015.    
Change in plan assets      
Fair value of plan assets at end of year $ 59 $ 52  
Funded status 14 13  
Change in benefit obligation      
Benefit obligation at end of year 45 39  
Pension      
Employee benefits      
Defined contribution cost 16 17 $ 16
401(k)      
Employee benefits      
Defined contribution cost $ 27 $ 27 $ 26