Variable Interest Entities - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Variable Interest Entity [Line Items]
Investments in unconsolidated entities, maximum exposure	$ 5		$ 4
Capital contributions, loans or advances	$ 229	$ 92
King Street Wireless out-of-period adjustment
Variable Interest Entity [Line Items]
Immaterial error correction	During the first quarter of 2018, U.S. Cellular recorded an out-of-period adjustment 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. This out-of-period adjustment 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 this adjustment was 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 Entity [Line Items]
Out-of-period adjustment		8
Net income attributable to U.S. Cellular shareholders | King Street Wireless out-of-period adjustment
Variable Interest Entity [Line Items]
Out-of-period adjustment		(8)
USCC EIP LLC
Variable Interest Entity [Line Items]
Capital contributions, loans or advances	$ 199	$ 66