Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of revenue
Revenue from contracts with customers	$ 1,297	$ 1,292	$ 3,770	$ 3,765
Operating lease income	27	29	79	75
Total operating revenues	1,324	1,321	3,849	3,840
Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	1,019	1,001	3,009	2,963
Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	674	663	2,004	1,984
Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	42	54	119	132
Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	152	135	441	397
Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	49	52	149	159
Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	45	44	135	137
Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	57	53	161	154
Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	278	291	761	802
UScellular
Disaggregation of revenue
Revenue from contracts with customers	1,007	1,008	2,907	2,915
Operating lease income	20	23	57	55
Total operating revenues	1,027	1,031	2,964	2,970
UScellular | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	755	751	2,233	2,217
UScellular | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	674	663	2,004	1,984
UScellular | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	42	54	119	132
UScellular | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
UScellular | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
UScellular | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
UScellular | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	39	34	110	101
UScellular | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	252	257	674	698
TDS Telecom Total
Disaggregation of revenue
Revenue from contracts with customers	246	230	726	693
Operating lease income	1	1	2	2
Total operating revenues	247	231	728	695
TDS Telecom Total | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	246	230	725	692
TDS Telecom Total | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom Total | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom Total | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	152	135	441	397
TDS Telecom Total | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	49	52	149	159
TDS Telecom Total | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	45	44	135	137
TDS Telecom Total | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	(1)
TDS Telecom Total | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	0	0	1	1
TDS Telecom Wireline
Disaggregation of revenue
Revenue from contracts with customers	173	168	511	511
Operating lease income	0	1	1	1
Total operating revenues	173	169	512	512
TDS Telecom Wireline | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	172	168	510	510
TDS Telecom Wireline | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom Wireline | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom Wireline | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	90	83	260	245
TDS Telecom Wireline | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	38	41	115	127
TDS Telecom Wireline | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	45	44	135	137
TDS Telecom Wireline | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom Wireline | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	0	0	1	1
TDS Telecom Cable
Disaggregation of revenue
Revenue from contracts with customers	74	62	215	184
Operating lease income	0	1	1	1
Total operating revenues	74	62	216	184
TDS Telecom Cable | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	74	62	215	183
TDS Telecom Cable | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom Cable | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom Cable | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	62	52	182	152
TDS Telecom Cable | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	11	10	33	32
TDS Telecom Cable | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom Cable | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
TDS Telecom Cable | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
Corporate, Eliminations and Other
Disaggregation of revenue
Revenue from contracts with customers	44	53	137	157
Operating lease income	6	5	20	18
Total operating revenues	50	59	157	175
Corporate, Eliminations and Other | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	18	19	51	54
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 | Inbound roaming
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	18	19	51	54
Corporate, Eliminations and Other | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	$ 26	$ 34	$ 86	$ 103