Earnings Per Share - Reconciliation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income attributable to UScellular shareholders	$ 85	$ 23	$ 224	$ 109
Weighted average number of shares used in basic earnings per share (in shares)	86	86	86	87
Effects of dilutive securities (in shares)	2	2	1	1
Weighted average number of shares used in diluted earnings per share (in shares)	88	88	87	88
Basic earnings per share attributable to UScellular shareholders (USD per share)	$ 0.98	$ 0.27	$ 2.60	$ 1.26
Diluted earnings per share attributable to UScellular shareholders (in shares)	$ 0.97	$ 0.27	$ 2.56	$ 1.24