Leases - Components of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases
Operating lease income1	$ 23	$ 55
Tower leases out of period adjustment
Leases
Immaterial error correction		During the third quarter of 2019, U.S. Cellular recorded an out-of-period adjustment attributable to 2009 through the second quarter of 2019 due to errors in the timing of recognition of revenue for certain tower leases. This out-of-period adjustment had the impact of increasing operating lease income by $5 million for the three and nine months ended September 30, 2019. U.S. Cellular determined that this adjustment was not material to any of the periods impacted.
Other service revenues | Tower leases out of period adjustment
Leases
Out-of-period adjustment	$ 5	$ 5