Revenue Recognition - Additional Information - Overview (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($) category	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)
Revenue from Contract with Customer [Abstract]
Number of categories of products and services | category	4
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,724	$ 1,799	$ 3,516	$ 3,717
Voice and Other - CAF Phase II [Member]
Disaggregation of Revenue [Line Items]
Total operating revenues			$ 73