Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of revenue
Revenue from contracts with customers	$ 1,193	$ 1,247	$ 3,630	$ 3,753
Operating lease income	31	31	94	95
Total operating revenues	1,224	1,278	3,724	3,848
Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	996	1,012	3,011	3,033
Transferred over time \| Retail service
Disaggregation of revenue
Revenue from contracts with customers	669	687	2,014	2,065
Transferred over time \| Residential
Disaggregation of revenue
Revenue from contracts with customers	186	177	558	521
Transferred over time \| Commercial
Disaggregation of revenue
Revenue from contracts with customers	36	38	110	118
Transferred over time \| Wholesale
Disaggregation of revenue
Revenue from contracts with customers	40	41	126	125
Transferred over time \| Other service
Disaggregation of revenue
Revenue from contracts with customers	65	69	203	204
Transferred at point in time \| Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	197	235	619	720
UScellular Total
Disaggregation of revenue
Revenue from contracts with customers	896	938	2,722	2,831
Operating lease income	26	25	77	75
Total operating revenues	922	963	2,799	2,906
UScellular Total \| Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	721	737	2,168	2,214
UScellular Total \| Transferred over time \| Retail service
Disaggregation of revenue
Revenue from contracts with customers	669	687	2,014	2,065
UScellular Total \| Transferred over time \| Residential
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
UScellular Total \| Transferred over time \| Commercial
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
UScellular Total \| Transferred over time \| Wholesale
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
UScellular Total \| Transferred over time \| Other service
Disaggregation of revenue
Revenue from contracts with customers	52	50	154	149
UScellular Total \| Transferred at point in time \| Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	175	201	554	617
TDS Telecom
Disaggregation of revenue
Revenue from contracts with customers	262	256	794	764
Operating lease income	1	1	2	3
Total operating revenues	263	256	797	767
TDS Telecom \| Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	262	255	794	763
TDS Telecom \| Transferred over time \| Retail service
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom \| Transferred over time \| Residential
Disaggregation of revenue
Revenue from contracts with customers	186	177	558	521
TDS Telecom \| Transferred over time \| Commercial
Disaggregation of revenue
Revenue from contracts with customers	36	38	110	118
TDS Telecom \| Transferred over time \| Wholesale
Disaggregation of revenue
Revenue from contracts with customers	40	41	126	125
TDS Telecom \| Transferred over time \| Other service
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom \| Transferred at point in time \| Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	0	0	1	1
Corporate, Eliminations and Other
Disaggregation of revenue
Revenue from contracts with customers	35	53	113	157
Operating lease income	4	5	15	17
Total operating revenues	39	59	128	175
Corporate, Eliminations and Other \| Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	13	19	49	55
Corporate, Eliminations and Other \| Transferred over time \| Retail service
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
Corporate, Eliminations and Other \| Transferred over time \| Residential
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
Corporate, Eliminations and Other \| Transferred over time \| Commercial
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
Corporate, Eliminations and Other \| Transferred over time \| Wholesale
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
Corporate, Eliminations and Other \| Transferred over time \| Other service
Disaggregation of revenue
Revenue from contracts with customers	13	19	49	55
Corporate, Eliminations and Other \| Transferred at point in time \| Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	$ 22	$ 34	$ 64	$ 102