Revenue Recognition - Disaggregation Of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Disaggregation of revenue
Revenue from contracts with customers	$ 944	$ 950
Operating lease income	19	16
Total operating revenues	963	966
Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	743	725
Transferred over time \| Retail service
Disaggregation of revenue
Revenue from contracts with customers	671	659
Transferred over time \| Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	37	34
Transferred over time \| Other service
Disaggregation of revenue
Revenue from contracts with customers	35	32
Transferred at point in time \| Equipment sales
Disaggregation of revenue
Revenue from contracts with customers	$ 201	$ 225

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Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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