Revenue Recognition - Disaggregation Of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of revenue
Revenue from contracts with customers	$ 1,235	$ 1,203
Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	973	956
Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	659	649
Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	34	27
Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	131	126
Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	54	57
Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	45	47
Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	50	50
Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	262	247
U.S. Cellular
Disaggregation of revenue
Revenue from contracts with customers	950	926
U.S. Cellular | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	725	708
U.S. Cellular | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	659	649
U.S. Cellular | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	34	27
U.S. Cellular | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	0	0
U.S. Cellular | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	0	0
U.S. Cellular | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	0	0
U.S. Cellular | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	32	32
U.S. Cellular | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	225	218
TDS Telecom Total
Disaggregation of revenue
Revenue from contracts with customers	230	230
TDS Telecom Total | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	229	230
TDS Telecom Total | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Total | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Total | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	131	126
TDS Telecom Total | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	54	57
TDS Telecom Total | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	45	47
TDS Telecom Total | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Total | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Wireline
Disaggregation of revenue
Revenue from contracts with customers	170	175
TDS Telecom Wireline | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	170	175
TDS Telecom Wireline | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Wireline | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Wireline | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	81	80
TDS Telecom Wireline | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	43	48
TDS Telecom Wireline | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	45	47
TDS Telecom Wireline | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Wireline | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Cable
Disaggregation of revenue
Revenue from contracts with customers	60	55
TDS Telecom Cable | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	60	55
TDS Telecom Cable | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Cable | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Cable | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	49	46
TDS Telecom Cable | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	10	10
TDS Telecom Cable | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Cable | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	0	0
TDS Telecom Cable | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	0	0
Corporate, Eliminations and Other
Disaggregation of revenue
Revenue from contracts with customers	55	47
Corporate, Eliminations and Other | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	18	18
Corporate, Eliminations and Other | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	0	0
Corporate, Eliminations and Other | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	0	0
Corporate, Eliminations and Other | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	0	0
Corporate, Eliminations and Other | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	0	0
Corporate, Eliminations and Other | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	0	0
Corporate, Eliminations and Other | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	18	18
Corporate, Eliminations and Other | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	$ 37	$ 29