Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
6.7% Senior Notes | UScellular
Financial Instruments
Interest rate	6.70%
Institutional and Other | Minimum
Financial Instruments
Interest rate	3.52%	3.52%
Institutional and Other | Maximum
Financial Instruments
Interest rate	7.93%	7.96%
Book Value | Retail
Financial Instruments
Long-term debt	$ 1,500	$ 1,500
Book Value | Institutional
Financial Instruments
Long-term debt	536	536
Book Value | Other
Financial Instruments
Long-term debt	2,187	2,103
Fair Value | Level 2 | Retail
Financial Instruments
Long-term debt	1,109	1,097
Fair Value | Level 2 | Institutional
Financial Instruments
Long-term debt	435	451
Fair Value | Level 2 | Other
Financial Instruments
Long-term debt	$ 2,187	$ 2,103