Variable Interest Entities - Narrative (Details) - USD ($)		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Variable Interest Entities, Other Disclosures
Assets	[1]	$ 7,228,000,000		$ 6,841,000,000
Investments in unconsolidated entities, maximum exposure		4,000,000		$ 4,000,000
Capital contributions, loans or advances		$ 92,000,000	$ 724,000,000
King Street Wireless out-of-period adjustment
Variable Interest Entities, Other Disclosures
Immaterial error correction		During the nine months ended September 30, 2018, U.S. Cellular recorded out-of-period adjustments attributable to 2016 and 2017 due to errors in the application of accounting guidance applicable to the calculation of Noncontrolling interests with redemption features related to King Street Wireless, Inc. These out-of-period adjustments had the impact of increasing Net income attributable to noncontrolling interests, net of tax, by $8 million and decreasing Net income attributable to U.S. Cellular shareholders by $8 million for the nine months ended September 30, 2018. U.S. Cellular determined that these adjustments were not material to any of the periods impacted.
Net income attributable to noncontrolling interests, net of tax | King Street Wireless out-of-period adjustment
Variable Interest Entities, Other Disclosures
Out-of-period adjustment		$ 8,000,000
Net income attributable to U.S. Cellular shareholders | King Street Wireless out-of-period adjustment
Variable Interest Entities, Other Disclosures
Out-of-period adjustment		(8,000,000)
USCC EIP LLC
Variable Interest Entities, Other Disclosures
Capital contributions, loans or advances		66,000,000	$ 701,000,000
Aquinas L.P.
Variable Interest Entities, Other Disclosures
Assets		$ 0

[1] The consolidated total assets as of September 30, 2018 and December 31, 2017, include assets held by consolidated variable interest entities (VIEs) of $851 million and $785 million, respectively, which are not available to be used to settle the obligations of U.S. Cellular. The consolidated total liabilities as of September 30, 2018 and December 31, 2017, include certain liabilities of consolidated VIEs of $20 million and $24 million, respectively, for which the creditors of the VIEs have no recourse to the general credit of U.S. Cellular. See Note 10 — Variable Interest Entities for additional information.