Variable Interest Entities, Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Variable Interest Entities, Other Disclosures
Capital contributions, loans or advances	$ 19	$ 654
Investments in unconsolidated entities, maximum exposure	$ 5		$ 4
Out-of-period adjustment description	During the three months ended March 31, 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 three months ended March 31, 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
Variable Interest Entities, Other Disclosures
Out-of-period adjustment	$ 8
Net income attributable to U.S. Cellular shareholders
Variable Interest Entities, Other Disclosures
Out-of-period adjustment	(8)
USCC EIP LLC
Variable Interest Entities, Other Disclosures
Capital contributions, loans or advances	$ 10	$ 650