Guarantor Financial Information - Condensed Consolidating Balance Sheet Information (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 1,528		$ 1,203
Accounts receivable, net	1,888		1,769
Equipment installment plan receivables, net	2,600		2,538
Accounts receivable from affiliates	20		11
Inventory	964		1,084
Other current assets	2,305	$ 1,598	1,676
Total current assets	9,305		8,281
Property and equipment, net	21,984	21,020	23,359
Operating lease right-of-use assets	10,933	9,251
Financing lease right-of-use assets	2,715	2,271
Goodwill	1,930		1,901
Spectrum licenses	36,465		35,559
Other intangible assets, net	115	186	198
Investments in subsidiaries, net	0		0
Intercompany receivables and note receivables	0		0
Equipment installment plan receivables due after one year, net	1,583		1,547
Other assets	1,891	1,552	1,623
Total assets	86,921		72,468
Current liabilities
Accounts payable and accrued liabilities	6,746	7,676	7,741
Payables to affiliates	187		200
Short-term debt	25		841
Deferred revenue	631		698
Short-term operating lease liabilities	2,287
Short-term financing lease liabilities	957
Other current liabilities	1,673	815	787
Total current liabilities	12,506		10,267
Long-term debt	10,958		12,124
Long-term debt to affiliates	13,986		14,582
Tower obligations	2,236	2,212	2,557
Deferred tax liabilities	5,607	4,703	4,472
Operating lease liabilities	10,539
Financing lease liabilities	1,346
Deferred rent expense			2,781
Negative carrying value of subsidiaries, net	0		0
Intercompany payables and debt	0		0
Other long-term liabilities	954	$ 903	967
Total long-term liabilities	45,626		37,483
Total stockholders' equity (deficit)	28,789		24,718	$ 22,559	$ 18,236
Total liabilities and stockholders' equity	86,921		72,468
Consolidating and Eliminating Adjustments
Current assets
Cash and cash equivalents	0		0
Accounts receivable, net	0		0
Equipment installment plan receivables, net	0		0
Accounts receivable from affiliates	0		0
Inventory	0		0
Other current assets	0		0
Total current assets	0		0
Property and equipment, net	0		0
Operating lease right-of-use assets	0
Financing lease right-of-use assets	0
Goodwill	0		0
Spectrum licenses	0		0
Other intangible assets, net	0		0
Investments in subsidiaries, net	(80,204)		(71,830)
Intercompany receivables and note receivables	(3,464)		(5,174)
Equipment installment plan receivables due after one year, net	0		0
Other assets	(163)		(141)
Total assets	(83,831)		(77,145)
Current liabilities
Accounts payable and accrued liabilities	0		0
Payables to affiliates	0		0
Short-term debt	0		0
Deferred revenue	0		0
Short-term operating lease liabilities	0
Short-term financing lease liabilities	0
Other current liabilities	0		0
Total current liabilities	0		0
Long-term debt	0		0
Long-term debt to affiliates	0		0
Tower obligations	0		0
Deferred tax liabilities	(163)		(141)
Operating lease liabilities	0
Financing lease liabilities	0
Deferred rent expense			0
Negative carrying value of subsidiaries, net	(864)		(676)
Intercompany payables and debt	(3,464)		(5,174)
Other long-term liabilities	0		0
Total long-term liabilities	(4,491)		(5,991)
Total stockholders' equity (deficit)	(79,340)		(71,154)
Total liabilities and stockholders' equity	(83,831)		(77,145)
Parent | Reportable Legal Entities
Current assets
Cash and cash equivalents	5		2
Accounts receivable, net	0		0
Equipment installment plan receivables, net	0		0
Accounts receivable from affiliates	0		0
Inventory	0		0
Other current assets	0		0
Total current assets	5		2
Property and equipment, net	0		0
Operating lease right-of-use assets	0
Financing lease right-of-use assets	0
Goodwill	0		0
Spectrum licenses	0		0
Other intangible assets, net	0		0
Investments in subsidiaries, net	28,898		25,314
Intercompany receivables and note receivables	0		0
Equipment installment plan receivables due after one year, net	0		0
Other assets	0		0
Total assets	28,903		25,316
Current liabilities
Accounts payable and accrued liabilities	0		0
Payables to affiliates	0		0
Short-term debt	0		0
Deferred revenue	0		0
Short-term operating lease liabilities	0
Short-term financing lease liabilities	0
Other current liabilities	0		0
Total current liabilities	0		0
Long-term debt	0		0
Long-term debt to affiliates	0		0
Tower obligations	0		0
Deferred tax liabilities	0		0
Operating lease liabilities	0
Financing lease liabilities	0
Deferred rent expense			0
Negative carrying value of subsidiaries, net	0		0
Intercompany payables and debt	114		598
Other long-term liabilities	0		0
Total long-term liabilities	114		598
Total stockholders' equity (deficit)	28,789		24,718
Total liabilities and stockholders' equity	28,903		25,316
Issuer | Reportable Legal Entities
Current assets
Cash and cash equivalents	1		1
Accounts receivable, net	0		0
Equipment installment plan receivables, net	0		0
Accounts receivable from affiliates	0		0
Inventory	0		0
Other current assets	646		0
Total current assets	647		1
Property and equipment, net	0		0
Operating lease right-of-use assets	0
Financing lease right-of-use assets	0
Goodwill	0		0
Spectrum licenses	0		0
Other intangible assets, net	0		0
Investments in subsidiaries, net	51,306		46,516
Intercompany receivables and note receivables	3,464		5,174
Equipment installment plan receivables due after one year, net	0		0
Other assets	18		7
Total assets	55,435		51,698
Current liabilities
Accounts payable and accrued liabilities	252		228
Payables to affiliates	145		157
Short-term debt	25		0
Deferred revenue	0		0
Short-term operating lease liabilities	0
Short-term financing lease liabilities	0
Other current liabilities	1,171		447
Total current liabilities	1,593		832
Long-term debt	10,958		10,950
Long-term debt to affiliates	13,986		14,582
Tower obligations	0		0
Deferred tax liabilities	0		0
Operating lease liabilities	0
Financing lease liabilities	0
Deferred rent expense			0
Negative carrying value of subsidiaries, net	0		0
Intercompany payables and debt	0		0
Other long-term liabilities	0		20
Total long-term liabilities	24,944		25,552
Total stockholders' equity (deficit)	28,898		25,314
Total liabilities and stockholders' equity	55,435		51,698
Guarantor Subsidiaries | Reportable Legal Entities
Current assets
Cash and cash equivalents	1,350		1,082
Accounts receivable, net	1,616		1,510
Equipment installment plan receivables, net	2,600		2,538
Accounts receivable from affiliates	20		11
Inventory	964		1,084
Other current assets	975		1,032
Total current assets	7,525		7,257
Property and equipment, net	21,790		23,113
Operating lease right-of-use assets	10,933
Financing lease right-of-use assets	2,715
Goodwill	1,930		1,901
Spectrum licenses	36,465		35,559
Other intangible assets, net	115		198
Investments in subsidiaries, net	0		0
Intercompany receivables and note receivables	0		0
Equipment installment plan receivables due after one year, net	1,583		1,547
Other assets	1,797		1,540
Total assets	84,853		71,115
Current liabilities
Accounts payable and accrued liabilities	6,236		7,263
Payables to affiliates	42		43
Short-term debt	0		841
Deferred revenue	631		698
Short-term operating lease liabilities	2,287
Short-term financing lease liabilities	957
Other current liabilities	139		164
Total current liabilities	10,292		9,009
Long-term debt	0		1,174
Long-term debt to affiliates	0		0
Tower obligations	75		384
Deferred tax liabilities	5,770		4,613
Operating lease liabilities	10,539
Financing lease liabilities	1,346
Deferred rent expense			2,781
Negative carrying value of subsidiaries, net	864		676
Intercompany payables and debt	2,968		4,258
Other long-term liabilities	937		926
Total long-term liabilities	22,499		14,812
Total stockholders' equity (deficit)	52,062		47,294
Total liabilities and stockholders' equity	84,853		71,115
Non-Guarantor Subsidiaries | Reportable Legal Entities
Current assets
Cash and cash equivalents	172		118
Accounts receivable, net	272		259
Equipment installment plan receivables, net	0		0
Accounts receivable from affiliates	0		0
Inventory	0		0
Other current assets	684		644
Total current assets	1,128		1,021
Property and equipment, net	194		246
Operating lease right-of-use assets	0
Financing lease right-of-use assets	0
Goodwill	0		0
Spectrum licenses	0		0
Other intangible assets, net	0		0
Investments in subsidiaries, net	0		0
Intercompany receivables and note receivables	0		0
Equipment installment plan receivables due after one year, net	0		0
Other assets	239		217
Total assets	1,561		1,484
Current liabilities
Accounts payable and accrued liabilities	258		250
Payables to affiliates	0		0
Short-term debt	0		0
Deferred revenue	0		0
Short-term operating lease liabilities	0
Short-term financing lease liabilities	0
Other current liabilities	363		176
Total current liabilities	621		426
Long-term debt	0		0
Long-term debt to affiliates	0		0
Tower obligations	2,161		2,173
Deferred tax liabilities	0		0
Operating lease liabilities	0
Financing lease liabilities	0
Deferred rent expense			0
Negative carrying value of subsidiaries, net	0		0
Intercompany payables and debt	382		318
Other long-term liabilities	17		21
Total long-term liabilities	2,560		2,512
Total stockholders' equity (deficit)	(1,620)		(1,454)
Total liabilities and stockholders' equity	$ 1,561		$ 1,484