Products and Services Revenues - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Number of categories of products and services	6
Universal service funds taxes and surcharges	$ 34	$ 33
Number of reportable segments	1
Customer relationship period	20 years
Remaining performance obligation	$ 311
Capitalized contract cost, net	$ 126
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer, contract term	1 year
Minimum | Contract Acquisition and Fulfillment Costs
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer, amortization period	30 months
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer, contract term	7 years
Maximum | Contract Acquisition and Fulfillment Costs
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer, amortization period	49 months