Guarantor Financial Information - Condensed Consolidating Statement of Comprehensive Income Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Revenues	$ 11,878	$ 11,061	$ 10,979	$ 11,080	$ 11,445	$ 10,839	$ 10,571	$ 10,455	$ 44,998	$ 43,310	$ 40,604
Operating expenses
Selling, general and administrative									14,139	13,161	12,259
Depreciation and amortization									6,616	6,486	5,984
Gains on disposal of spectrum licenses									0	0	(235)
Total operating expenses									39,276	38,001	35,716
Operating income	1,234	1,471	1,541	1,476	1,137	1,440	1,450	1,282	5,722	5,309	4,888
Other income (expense)
Interest expense									(727)	(835)	(1,111)
Interest expense to affiliates									(408)	(522)	(560)
Interest income									24	19	17
Other (expense) income, net									(8)	(54)	(73)
Total other expense, net									(1,119)	(1,392)	(1,727)
Income before income taxes									4,603	3,917	3,161
Income tax expense									(1,135)	(1,029)	1,375
Earnings of subsidiaries									0	0	0
Net income	751	870	939	908	640	795	782	671	3,468	2,888	4,536
Preferred Stock Dividends and Other Adjustments									0	0	(55)
Net income attributable to common stockholders	751	870	939	908	640	795	782	671	3,468	2,888	4,481
Net income	$ 751	$ 870	$ 939	$ 908	$ 640	$ 795	$ 782	$ 671	3,468	2,888	4,536
Other comprehensive (loss) income, net of tax
Other comprehensive (loss) income, net of tax									(536)	(332)	7
Total comprehensive income									2,932	2,556	4,543
Service
Revenues
Revenues									33,994	31,992	30,160
Operating expenses
Cost of services and equipment sales									6,622	6,307	6,100
Product
Revenues
Revenues									9,840	10,009	9,375
Operating expenses
Cost of services and equipment sales									11,899	12,047	11,608
Other revenues
Revenues
Revenues									1,164	1,309	1,069
Consolidating and Eliminating Adjustments
Revenues
Revenues									(1,660)	(1,240)	(1,117)
Operating expenses
Selling, general and administrative									(1,333)	(1,038)	(873)
Depreciation and amortization									0	0	0
Gains on disposal of spectrum licenses											0
Total operating expenses									(1,660)	(1,240)	(1,117)
Operating income									0	0	0
Other income (expense)
Interest expense									0	0	0
Interest expense to affiliates									21	21	23
Interest income									(21)	(21)	(23)
Other (expense) income, net									0	0	0
Total other expense, net									0	0	0
Income before income taxes									0	0	0
Income tax expense									0	0	0
Earnings of subsidiaries									(7,818)	(6,904)	(10,440)
Net income									(7,818)	(6,904)	(10,440)
Preferred Stock Dividends and Other Adjustments											0
Net income attributable to common stockholders											(10,440)
Net income									(7,818)	(6,904)	(10,440)
Other comprehensive (loss) income, net of tax
Other comprehensive (loss) income, net of tax									350	216	(14)
Total comprehensive income									(7,468)	(6,688)	(10,454)
Consolidating and Eliminating Adjustments | Service
Revenues
Revenues									(1,277)	(978)	(847)
Operating expenses
Cost of services and equipment sales									(111)	0	0
Consolidating and Eliminating Adjustments | Product
Revenues
Revenues									(216)	(201)	(245)
Operating expenses
Cost of services and equipment sales									(216)	(202)	(244)
Consolidating and Eliminating Adjustments | Other revenues
Revenues
Revenues									(167)	(61)	(25)
Parent | Reportable Legal Entities
Revenues
Revenues									0	0	0
Operating expenses
Selling, general and administrative									0	0	0
Depreciation and amortization									0	0	0
Gains on disposal of spectrum licenses											0
Total operating expenses									0	0	0
Operating income									0	0	0
Other income (expense)
Interest expense									0	0	0
Interest expense to affiliates									0	0	0
Interest income									0	0	1
Other (expense) income, net									0	0	0
Total other expense, net									0	0	1
Income before income taxes									0	0	1
Income tax expense									0	0	0
Earnings of subsidiaries									3,468	2,888	4,535
Net income									3,468	2,888	4,536
Preferred Stock Dividends and Other Adjustments											(55)
Net income attributable to common stockholders											4,481
Net income									3,468	2,888	4,536
Other comprehensive (loss) income, net of tax
Other comprehensive (loss) income, net of tax									(536)	(332)	7
Total comprehensive income									2,932	2,556	4,543
Parent | Reportable Legal Entities | Service
Revenues
Revenues									0	0	0
Operating expenses
Cost of services and equipment sales									0	0	0
Parent | Reportable Legal Entities | Product
Revenues
Revenues									0	0	0
Operating expenses
Cost of services and equipment sales									0	0	0
Parent | Reportable Legal Entities | Other revenues
Revenues
Revenues									0	0	0
Issuer | Reportable Legal Entities
Revenues
Revenues									19	29	3
Operating expenses
Selling, general and administrative									16	11	0
Depreciation and amortization									0	0	0
Gains on disposal of spectrum licenses											0
Total operating expenses									16	11	0
Operating income									3	18	3
Other income (expense)
Interest expense									(454)	(528)	(811)
Interest expense to affiliates									(409)	(522)	(560)
Interest income									22	23	29
Other (expense) income, net									(13)	(87)	(88)
Total other expense, net									(854)	(1,114)	(1,430)
Income before income taxes									(851)	(1,096)	(1,427)
Income tax expense									0	0	0
Earnings of subsidiaries									4,319	3,984	5,962
Net income									3,468	2,888	4,535
Preferred Stock Dividends and Other Adjustments											0
Net income attributable to common stockholders											4,535
Net income									3,468	2,888	4,535
Other comprehensive (loss) income, net of tax
Other comprehensive (loss) income, net of tax									(536)	(332)	7
Total comprehensive income									2,932	2,556	4,542
Issuer | Reportable Legal Entities | Service
Revenues
Revenues									0	0	0
Operating expenses
Cost of services and equipment sales									0	0	0
Issuer | Reportable Legal Entities | Product
Revenues
Revenues									0	0	0
Operating expenses
Cost of services and equipment sales									0	0	0
Issuer | Reportable Legal Entities | Other revenues
Revenues
Revenues									19	29	3
Guarantor Subsidiaries | Reportable Legal Entities
Revenues
Revenues									43,430	41,959	39,393
Operating expenses
Selling, general and administrative									14,467	13,296	12,276
Depreciation and amortization									6,564	6,422	5,914
Gains on disposal of spectrum licenses											(235)
Total operating expenses									38,672	37,240	34,880
Operating income									4,758	4,719	4,513
Other income (expense)
Interest expense									(88)	(114)	(109)
Interest expense to affiliates									(20)	(21)	(23)
Interest income									20	16	10
Other (expense) income, net									6	33	16
Total other expense, net									(82)	(86)	(106)
Income before income taxes									4,676	4,633	4,407
Income tax expense									(965)	(950)	1,527
Earnings of subsidiaries									31	32	(57)
Net income									3,742	3,715	5,877
Preferred Stock Dividends and Other Adjustments											0
Net income attributable to common stockholders											5,877
Net income									3,742	3,715	5,877
Other comprehensive (loss) income, net of tax
Other comprehensive (loss) income, net of tax									186	116	7
Total comprehensive income									3,928	3,831	5,884
Guarantor Subsidiaries | Reportable Legal Entities | Service
Revenues
Revenues									32,268	30,637	28,894
Operating expenses
Cost of services and equipment sales									6,733	6,283	6,076
Guarantor Subsidiaries | Reportable Legal Entities | Product
Revenues
Revenues									10,053	10,209	9,620
Operating expenses
Cost of services and equipment sales									10,908	11,239	10,849
Guarantor Subsidiaries | Reportable Legal Entities | Other revenues
Revenues
Revenues									1,109	1,113	879
Non-Guarantor Subsidiaries | Reportable Legal Entities
Revenues
Revenues									3,209	2,562	2,325
Operating expenses
Selling, general and administrative									989	892	856
Depreciation and amortization									52	64	70
Gains on disposal of spectrum licenses											0
Total operating expenses									2,248	1,990	1,953
Operating income									961	572	372
Other income (expense)
Interest expense									(185)	(193)	(191)
Interest expense to affiliates									0	0	0
Interest income									3	1	0
Other (expense) income, net									(1)	0	(1)
Total other expense, net									(183)	(192)	(192)
Income before income taxes									778	380	180
Income tax expense									(170)	(79)	(152)
Earnings of subsidiaries									0	0	0
Net income									608	301	28
Preferred Stock Dividends and Other Adjustments											0
Net income attributable to common stockholders											28
Net income									608	301	28
Other comprehensive (loss) income, net of tax
Other comprehensive (loss) income, net of tax									0	0	0
Total comprehensive income									608	301	28
Non-Guarantor Subsidiaries | Reportable Legal Entities | Service
Revenues
Revenues									3,003	2,333	2,113
Operating expenses
Cost of services and equipment sales									0	24	24
Non-Guarantor Subsidiaries | Reportable Legal Entities | Product
Revenues
Revenues									3	1	0
Operating expenses
Cost of services and equipment sales									1,207	1,010	1,003
Non-Guarantor Subsidiaries | Reportable Legal Entities | Other revenues
Revenues
Revenues									$ 203	$ 228	$ 212