Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of revenue
Revenue from contracts with customers	$ 1,237	$ 1,238	$ 2,472	$ 2,473
Operating lease income	26	23	52	45
Total operating revenues	1,263	1,261	2,524	2,518
Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	990	990	1,990	1,963
Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	658	662	1,329	1,322
Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	41	44	77	78
Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	145	131	289	262
Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	49	54	99	107
Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	45	48	91	94
Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	52	51	106	100
Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	247	248	482	510
U.S. Cellular
Disaggregation of revenue
Revenue from contracts with customers	954	957	1,899	1,907
Operating lease income	19	16	38	32
Total operating revenues	973	973	1,937	1,939
U.S. Cellular | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	734	741	1,477	1,466
U.S. Cellular | Transferred over time | Retail service
Disaggregation of revenue
Revenue from contracts with customers	658	662	1,329	1,322
U.S. Cellular | Transferred over time | Inbound roaming
Disaggregation of revenue
Revenue from contracts with customers	41	44	77	78
U.S. Cellular | Transferred over time | Residential
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
U.S. Cellular | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
U.S. Cellular | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	0	0	0	0
U.S. Cellular | Transferred over time | Other service
Disaggregation of revenue
Revenue from contracts with customers	35	35	71	66
U.S. Cellular | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	220	216	422	441
TDS Telecom Total
Disaggregation of revenue
Revenue from contracts with customers	240	233	479	463
Operating lease income	1	0	2	1
Total operating revenues	241	233	481	464
TDS Telecom Total | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	239	233	479	462
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	145	131	289	262
TDS Telecom Total | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	49	54	99	107
TDS Telecom Total | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	45	48	91	94
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	169	172	338	342
Operating lease income	1	0	1	0
Total operating revenues	169	172	339	343
TDS Telecom Wireline | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	169	172	338	342
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	85	81	170	162
TDS Telecom Wireline | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	38	42	77	86
TDS Telecom Wireline | Transferred over time | Wholesale
Disaggregation of revenue
Revenue from contracts with customers	45	48	91	94
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	0	1
TDS Telecom Cable
Disaggregation of revenue
Revenue from contracts with customers	71	62	142	121
Operating lease income	0	0	1	0
Total operating revenues	71	62	142	121
TDS Telecom Cable | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	71	62	141	121
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	60	51	119	100
TDS Telecom Cable | Transferred over time | Commercial
Disaggregation of revenue
Revenue from contracts with customers	11	11	22	21
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	43	48	94	103
Operating lease income	6	7	12	12
Total operating revenues	49	55	106	115
Corporate, Eliminations and Other | Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	17	16	35	35
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	17	16	35	35
Corporate, Eliminations and Other | Transferred at point in time | Equipment and product sales
Disaggregation of revenue
Revenue from contracts with customers	$ 27	$ 32	$ 59	$ 68