T-Mobile US (TMUS) 10-K 23 Feb 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Feb. 17, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	1-33409
Entity Registrant Name	T-MOBILE US, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-0836269
Entity Address, Address Line One	12920 SE 38th Street
Entity Address, City or Town	Bellevue
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	98006-1350
City Area Code	(425)
Local Phone Number	378-4000
Title of 12(b) Security	Common Stock, par value $0.00001 per share
Trading Symbol	TMUS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 40.7
Entity Common Stock, Shares Outstanding		1,242,804,085
Documents Incorporated by Reference	Part III of this Annual Report on Form 10-K will be incorporated by reference from certain portions of the definitive Proxy Statement for the Registrant’s 2021 Annual Meeting of Stockholders, which definitive Proxy Statement will be filed with the Securities and Exchange Commission pursuant to Regulation 14A or will be included in an amendment to this Report.
Entity Central Index Key	0001283699
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 10,385	$ 1,528
Accounts receivable, net of allowance for credit losses of $194 and $61	4,254	1,888
Equipment installment plan receivables, net of allowance for credit losses and imputed discount of $478 and $333	3,577	2,600
Accounts receivable from affiliates	22	20
Inventory	2,527	964
Prepaid expenses	624	333
Other current assets	2,496	1,972
Total current assets	23,885	9,305
Property and equipment, net	41,175	21,984
Operating lease right-of-use assets	28,021	10,933
Financing lease right-of-use assets	3,028	2,715
Goodwill	11,117	1,930
Spectrum licenses	82,828	36,465
Other intangible assets, net	5,298	115
Equipment installment plan receivables due after one year, net of allowance for credit losses and imputed discount of $127 and $66	2,031	1,583
Other assets	2,779	1,891
Total assets	200,162	86,921
Current liabilities
Accounts payable and accrued liabilities	10,196	6,746
Payables to affiliates	157	187
Short-term debt	4,579	25
Deferred revenue	1,030	631
Short-term operating lease liabilities	3,868	2,287
Short-term financing lease liabilities	1,063	957
Other current liabilities	810	1,673
Total current liabilities	21,703	12,506
Long-term debt	61,830	10,958
Long-term debt to affiliates	4,716	13,986
Tower obligations	3,028	2,236
Deferred tax liabilities	9,966	5,607
Operating lease liabilities	26,719	10,539
Financing lease liabilities	1,444	1,346
Other long-term liabilities	5,412	954
Total long-term liabilities	113,115	45,626
Commitments and contingencies (Note 18)
Stockholders' equity
Common Stock, par value $0.00001 per share, 2,000,000,000 shares authorized; 1,243,345,584 and 858,418,615 shares issued, 1,241,805,706 and 856,905,400 shares outstanding	0	0
Additional paid-in capital	72,772	38,498
Treasury stock, at cost, 1,539,878 and 1,513,215 shares issued	(11)	(8)
Accumulated other comprehensive loss	(1,581)	(868)
Accumulated deficit	(5,836)	(8,833)
Total stockholders' equity	65,344	28,789
Total liabilities and stockholders' equity	$ 200,162	$ 86,921

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for credit losses	$ 194	$ 61
Allowance for credit losses and imputed discount	478	333
Allowance for credit losses and imputed discount	$ 127	$ 66
Common stock, par value (in USD per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000
Common stock, shares issued (in shares)	1,243,345,584	858,418,615
Common stock, shares outstanding (in shares)	1,241,805,706	856,905,400
Treasury stock, at cost (in shares)	1,539,878	1,513,215

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Revenues	$ 68,397	$ 44,998	$ 43,310
Operating expenses
Selling, general and administrative	18,926	14,139	13,161
Impairment expense	418	0	0
Depreciation and amortization	14,151	6,616	6,486
Total operating expenses	61,761	39,276	38,001
Operating income	6,636	5,722	5,309
Other income (expense)
Interest expense	(2,483)	(727)	(835)
Interest expense to affiliates	(247)	(408)	(522)
Interest income	29	24	19
Other expense, net	(405)	(8)	(54)
Total other expense, net	(3,106)	(1,119)	(1,392)
Income from continuing operations before income taxes	3,530	4,603	3,917
Income tax expense	(786)	(1,135)	(1,029)
Income from continuing operations	2,744	3,468	2,888
Income from discontinued operations, net of tax	320	0	0
Net income	3,064	3,468	2,888
Other comprehensive loss, net of tax
Unrealized loss on cash flow hedges, net of tax effect of $(250), $(187), and $(115)	(723)	(536)	(332)
Unrealized gain on foreign currency translation adjustment, net of tax effect of $1, $0 and $0	4	0	0
Net unrecognized gain (loss) on pension and other postretirement benefits, net of tax effect of $2, $0 and $0	6	0	0
Other comprehensive income (loss)	(713)	(536)	(332)
Total comprehensive income	$ 2,351	$ 2,932	$ 2,556
Earnings Per Share, Basic [Abstract]
Continuing operations (in USD per share)	$ 2.40	$ 4.06	$ 3.40
Discontinued operations (in USD per share)	0.28	0	0
Basic (in USD per share)	2.68	4.06	3.40
Earnings Per Share, Diluted [Abstract]
Continuing operations (in USD per share)	2.37	4.02	3.36
Discontinued operations (in USD per share)	0.28	0	0
Diluted (in USD per share)	$ 2.65	$ 4.02	$ 3.36
Weighted average shares outstanding
Basic (in shares)	1,144,206,326	854,143,751	849,744,152
Diluted (in shares)	1,154,749,428	863,433,511	858,290,174
Postpaid revenues
Revenues
Revenues	$ 36,306	$ 22,673	$ 20,862
Prepaid revenues
Revenues
Revenues	9,421	9,543	9,598
Wholesale revenues
Revenues
Revenues	2,590	1,279	1,183
Roaming and other service revenues
Revenues
Revenues	2,078	1,005	798
Service
Revenues
Revenues	50,395	34,500	32,441
Operating expenses
Cost of services and equipment sales	11,878	6,622	6,307
Equipment
Revenues
Revenues	17,312	9,840	10,009
Operating expenses
Cost of services and equipment sales	16,388	11,899	12,047
Other revenues
Revenues
Revenues	$ 690	$ 658	$ 860

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Cash flow hedges, tax effect	$ (250)	$ (187)	$ (115)
Foreign currency translation adjustment, tax effect	1	0	0
Net unrecognized gain (loss) on pension and other postretirement benefit, tax	$ 2	$ 0	$ 0

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net income	$ 3,064	$ 3,468	$ 2,888
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	14,151	6,616	6,486
Stock-based compensation expense	694	495	424
Deferred income tax expense	822	1,091	980
Bad debt expense	602	307	297
Losses from sales of receivables	36	130	157
Deferred rent expense	0	0	26
Losses on redemption of debt	371	19	122
Impairment expense	418	0	0
Changes in operating assets and liabilities
Accounts receivable	(3,273)	(3,709)	(4,617)
Equipment installment plan receivables	(1,453)	(1,015)	(1,598)
Inventories	(2,222)	(617)	(201)
Operating lease right-of-use assets	3,465	1,896	0
Other current and long-term assets	(402)	(144)	(181)
Accounts payable and accrued liabilities	(2,123)	17	(867)
Short and long-term operating lease liabilities	(3,699)	(2,131)	0
Other current and long-term liabilities	(2,178)	144	(69)
Other, net	367	257	52
Net cash provided by operating activities	8,640	6,824	3,899
Investing activities
Purchases of property and equipment, including capitalized interest of $440, $473 and $362	(11,034)	(6,391)	(5,541)
Purchases of spectrum licenses and other intangible assets, including deposits	(1,333)	(967)	(127)
Proceeds from sales of tower sites	0	38	0
Proceeds related to beneficial interests in securitization transactions	3,134	3,876	5,406
Net cash related to derivative contracts under collateral exchange arrangements	632	(632)	0
Acquisition of companies, net of cash and restricted cash acquired	(5,000)	(31)	(338)
Proceeds from the divestiture of prepaid business	1,224	0	0
Other, net	(338)	(18)	21
Net cash used in investing activities	(12,715)	(4,125)	(579)
Financing activities
Proceeds from issuance of long-term debt	35,337	0	2,494
Payments of consent fees related to long-term debt	(109)	0	0
Proceeds from borrowing on revolving credit facility	0	2,340	6,265
Repayments of revolving credit facility	0	(2,340)	(6,265)
Repayments of financing lease obligations	(1,021)	(798)
Repayments of financing lease obligations			(700)
Repayments of short-term debt for purchases of inventory, property and equipment and other financial liabilities	(481)	(775)	(300)
Repayments of long-term debt	(20,416)	(600)	(3,349)
Issuance of common stock	19,840	0	0
Repurchases of common stock	(19,536)	0	(1,071)
Proceeds from issuance of short-term debt	18,743	0	0
Repayments of short-term debt	(18,929)	0	0
Tax withholdings on share-based awards	(439)	(156)	(146)
Cash payments for debt prepayment or debt extinguishment costs	(82)	(28)	(212)
Other, net	103	(17)	(52)
Net cash provided by (used in) financing activities	13,010	(2,374)	(3,336)
Change in cash and cash equivalents, including restricted cash	8,935	325	(16)
Cash and cash equivalents, including restricted cash
Beginning of period	1,528	1,203	1,219
End of period	$ 10,463	$ 1,528	$ 1,203

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Cash Flows [Abstract]
Capitalized interest	$ 440	$ 473	$ 362

Condensed Consolidated Statem_5

Condensed Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions		Total	Common Stock Outstanding	Treasury Shares at Cost	Par Value and Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017			859,406,651
Beginning balance at Dec. 31, 2017		$ 22,559		$ (4)	$ 38,629	$ 8	$ (16,074)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		2,888					2,888
Other comprehensive (loss) income		(332)				(332)
Stock-based compensation		473			473
Exercise of stock options (in shares)			187,965
Exercise of stock options		3			3
Stock issued for employee stock purchase plan (in shares)			2,011,794
Stock issued for employee stock purchase plan		103			103
Issuance of vested restricted stock units (in shares)			7,448,148
Issuance of restricted stock awards (in shares)			(225,799)
Shares withheld related to net share settlement of stock awards and stock options (in shares)			(2,321,827)
Shares withheld related to net share settlement of stock awards and stock options		$ (146)			(146)
Repurchases of common stock (in shares)		(16,738,758)	(16,738,758)
Repurchases of common stock		$ (1,054)			(1,054)
Transfer RSU to NQDC plan (in shares)			(39,455)
Transfer RSU from NQDC plan				(2)	2
Prior year Retained Earnings	[1]	224				(8)	232
Ending balance (in shares) at Dec. 31, 2018			850,180,317
Ending balance at Dec. 31, 2018		24,718		(6)	38,010	(332)	(12,954)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		3,468					3,468
Other comprehensive (loss) income		(536)				(536)
Stock-based compensation		517			517
Exercise of stock options (in shares)			85,083
Exercise of stock options		1			1
Stock issued for employee stock purchase plan (in shares)			2,091,650
Stock issued for employee stock purchase plan		124			124
Issuance of vested restricted stock units (in shares)			6,685,950
Issuance of restricted stock awards (in shares)			(24,682)
Shares withheld related to net share settlement of stock awards and stock options (in shares)			(2,094,555)
Shares withheld related to net share settlement of stock awards and stock options		(156)			(156)
Transfer RSU to NQDC plan (in shares)			(18,363)
Transfer RSU from NQDC plan		0		(2)	2
Prior year Retained Earnings	[1]	$ 653					653
Ending balance (in shares) at Dec. 31, 2019		856,905,400	856,905,400
Ending balance at Dec. 31, 2019		$ 28,789		(8)	38,498	(868)	(8,833)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		3,064					3,064
Other comprehensive (loss) income		(713)				(713)
Executive put option (in shares)			(342,000)
Executive put option		1			1
Stock-based compensation		750			750
Exercise of stock options (in shares)			906,295
Exercise of stock options		48			48
Stock issued for employee stock purchase plan (in shares)			2,144,036
Stock issued for employee stock purchase plan		148			148
Issuance of vested restricted stock units (in shares)			13,263,434
Shares withheld related to net share settlement of stock awards and stock options (in shares)			(4,441,107)
Shares withheld related to net share settlement of stock awards and stock options		(439)			(439)
Transfer RSU to NQDC plan (in shares)			(26,662)
Transfer RSU from NQDC plan		0		(3)	3
Shares issued in secondary offering (in shares)			198,314,426
Shares issued in secondary offering		19,766			19,766
Shares repurchased from SoftBank (in shares)			(198,314,426)
Shares repurchased from SoftBank		(19,536)			(19,536)
Merger consideration (in shares)			373,396,310
Merger consideration		33,533			33,533
Prior year Retained Earnings	[1]	$ (67)					(67)
Ending balance (in shares) at Dec. 31, 2020		1,241,805,706	1,241,805,706
Ending balance at Dec. 31, 2020		$ 65,344		$ (11)	$ 72,772	$ (1,581)	$ (5,836)
[1]	Prior year Retained Earnings represents the impact of the adoption of new accounting standards on beginning Accumulated Deficit and Accumulated Other Comprehensive Loss. See Note 1 – Summary of Significant Accounting Policies for further information.

Condensed Consolidated Statem_6

Condensed Consolidated Statement of Stockholders' Equity (Parenthetical) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)shares
Par Value and Additional Paid-in Capital
Payment received to facilitate SoftBank Monetization | $	$ 304
Marcelo Claure
Shares sold (in shares) | shares	5

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policies	Note 1 – Summary of Significant Accounting Policies Description of Business T-Mobile US, Inc. (“T-Mobile,” “we,” “our,” “us” or the “Company”), together with its consolidated subsidiaries, is a leading provider of mobile communications services, including voice, messaging and data, under its flagship brands, T-Mobile and Metro™ by T-Mobile ("Metro by T-Mobile"), in the United States, Puerto Rico and the U.S. Virgin Islands. Substantially all of our revenues were earned in, and substantially all of our long-lived assets are located in, the U.S., Puerto Rico and the U.S. Virgin Islands. We provide mobile communications services primarily using our 4G Long-Term Evolution (“LTE”) network and our 5G technology network. We also offer a wide selection of wireless devices, including handsets, tablets and other mobile communication devices, and accessories for sale, as well as financing through Equipment Installment Plans (“EIP”) and leasing through JUMP! On Demand™. Additionally, we provide reinsurance for device insurance policies and extended warranty contracts offered to our mobile communications customers. Basis of Presentation The consolidated financial statements include the balances and results of operations of T-Mobile and our consolidated subsidiaries. We consolidate majority-owned subsidiaries over which we exercise control, as well as variable interest entities (“VIE”) where we are deemed to be the primary beneficiary and VIEs, which cannot be deconsolidated, such as those related to Tower obligations. Intercompany transactions and balances have been eliminated in consolidation. We operate as a single operating segment. On April 29, 2018, we entered into a Business Combination Agreement (the “Business Combination Agreement”) to merge with Sprint Corporation (“Sprint”) in an all-stock transaction at a fixed exchange ratio of 0.10256 shares of T-Mobile common stock for each share of Sprint common stock, or 9.75 shares of Sprint common stock for each share of T-Mobile common stock (the “Merger”). On April 1, 2020, we completed the Merger and acquired Sprint (see Note 2 - Business Combination ). On July 26, 2019, pursuant to the requirement as set forth in the U.S. Department of Justice’s (the “DOJ”) complaint and proposed final judgement (the “Consent Decree”), T-Mobile entered into an Asset Purchase Agreement (the “Asset Purchase Agreement”) with Sprint and DISH Network Corporation (“DISH”). Pursuant to the Asset Purchase Agreement and upon the terms and subject to the conditions thereof, on July 1, 2020, DISH acquired the prepaid wireless business operated under the Boost Mobile and Sprint prepaid brands (excluding the Assurance brand Lifeline customers and the prepaid wireless customers of Shenandoah Telecommunications Company and Swiftel Communications, Inc.), including customer accounts, inventory, contracts, intellectual property and certain other specified assets (the “Prepaid Business”) and assumed certain related liabilities (the “Prepaid Transaction”). Upon closing of the Prepaid Transaction, we received $1.4 billion from DISH, subject to a working capital adjustment. The revenues and expenses of the Prepaid Business are presented as discontinued operations for the year ended December 31, 2020. The preparation of financial statements in conformity with U.S. generally accepted accounting principles (“GAAP”) requires our management to make estimates and assumptions which affect the financial statements and accompanying notes. Estimates are based on historical experience, where applicable, and other assumptions which our management believes are reasonable under the circumstances, including but not limited to the valuation of assets acquired and liabilities assumed through the Merger with Sprint and the potential impacts arising from the COVID-19 pandemic (the “Pandemic”). These estimates are inherently subject to judgment and actual results could differ from those estimates. Certain prior year amounts have been reclassified to conform to the current year's presentation. Business Combination Assets acquired and liabilities assumed as part of a business combination are generally recorded at their fair value at the date of acquisition. The excess of purchase price over the fair value of assets acquired and liabilities assumed is recorded as goodwill. Determining fair value of identifiable assets, particularly intangibles, and liabilities acquired requires management to make estimates, which are based on all available information and in some cases assumptions with respect to the timing and amount of future revenues and expenses associated with an asset or liability. See N ote 2 – Business Combination for further discussion of the Merger between T-Mobile and Sprint. Cash and Cash Equivalents Cash equivalents consist of highly liquid money market funds and U.S. Treasury securities with remaining maturities of three months or less at the date of purchase. Receivables and Allowance for Credit Losses Accounts Receivable Accounts receivable consists primarily of amounts currently due from customers (e.g., for wireless services and monthly device lease payments), device insurance administrators, wholesale partners, other carriers and third-party retail channels. Accounts receivable are presented in our Consolidated Balance Sheets at the amortized cost basis (i.e., the receivables’ outstanding principal balance adjusted for any write-offs), net of the allowance for expected credit losses. We have an arrangement to sell certain of our customer service accounts receivable on a revolving basis, which are treated as sales of financial assets. Equipment Installment Plan Receivables We offer certain retail customers the option to pay for their devices and other purchases in installments, generally over a period of 24 months using an EIP. EIP receivables are presented in our Consolidated Balance Sheets at the amortized cost basis (i.e., the receivables’ unpaid principal balance adjusted for any write-offs and unamortized discounts), net of the allowance for expected credit losses. At the time of an installment sale, we impute a discount for interest if the term exceeds 12 months as there is no stated rate of interest on the receivables. The receivables are recorded at their present value, which is determined by discounting expected future cash payments at the imputed interest rate. This adjustment results in a discount or reduction in transaction price which is allocated to the performance obligations and reduces Service revenues and Equipment revenues in our Consolidated Statements of Comprehensive Income. The imputed discount rate is the current market interest rate and is predominately comprised of the estimated credit risk underlying the EIP receivable, reflecting the estimated credit worthiness of the customer. The imputed discount on receivables is amortized over the financed installment term using the effective interest method and recognized as Other revenues in our Consolidated Statements of Comprehensive Income. The current portion of the EIP receivables is included in Equipment installment plan receivables, net and the long-term portion of the EIP receivables is included in Equipment installment plan receivables due after one year, net in our Consolidated Balance Sheets. We have an arrangement to sell certain EIP receivables on a revolving basis, which are treated as sales of financial assets. Allowance for Credit Losses We maintain an allowance for expected credit losses and determine its appropriateness through an established process that assesses the lifetime credit losses that we expect to incur related to our receivable portfolio. Our process involves procedures to appropriately consider the unique risk characteristics of our accounts receivable and EIP receivable portfolio segments. For each portfolio segment, losses are estimated collectively for groups of receivables with similar characteristics. Our allowance levels are influenced by receivable volumes, receivable delinquency status, historical loss experience and other conditions that affect loss expectations, such as changes in credit and collections policies and forecasts of macro-economic conditions. While we attribute portions of the allowance to our respective accounts receivable and EIP portfolio segments, the entire allowance is available to credit losses related to the total receivable portfolio. We consider a receivable past due and delinquent when a customer has not paid us by the contractually specified payment due date. Account balances are written off against the allowance for credit losses if collection efforts are unsuccessful and the receivable balance is deemed uncollectible (customer default), based on factors such as customer credit ratings as well as the length of time the amounts are past due. If there is a deterioration of our customers’ financial condition or if future actual default rates on receivables in general differ from those currently anticipated, we will adjust our allowance for credit losses accordingly, which may materially affect our financial results in the period the adjustments are made. Inventories Inventories consist primarily of wireless devices and accessories, which are valued at the lower of cost or net realizable value. Cost is determined using standard cost which approximates average cost. Shipping and handling costs paid to wireless device and accessories vendors as well as costs to refurbish used devices are included in the standard cost of inventory. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of disposal and transportation. We record inventory write-downs to net realizable value for obsolete and slow-moving items based on inventory turnover trends and historical experience. Deferred Purchase Price Assets In connection with the sales of certain service and EIP accounts receivable pursuant to the sale arrangements, we have deferred purchase price assets measured at fair value that are based on a discounted cash flow model using unobservable Level 3 inputs, including estimated customer default rates and credit worthiness. See Note 4 – Sales of Certain Receivables for further information. Long-Lived Assets Long-lived assets include assets that do not have indefinite lives, such as property and equipment and other intangible assets. Substantially all of our long-lived assets are located in the U.S., including Puerto Rico and the U.S. Virgin Islands. We assess potential impairments to our long-lived assets when events or changes in circumstances indicate the carrying amount of the asset may not be recoverable. If any indicators of impairment are present, we test recoverability. The carrying value of a long-lived asset or asset group is not recoverable if it exceeds the sum of the undiscounted cash flows expected to be generated from the use and eventual disposition of the asset or asset group. If the undiscounted cash flows do not exceed the asset or asset group’s carrying amount, then an impairment loss is recorded, measured as the amount by which the carrying amount of a long-lived asset or asset group exceeds its fair value. Property and Equipment Property and equipment consists of buildings and equipment, wireless communications systems, leasehold improvements, capitalized software, leased wireless devices and construction in progress. Buildings and equipment include certain network server equipment. Wireless communications systems include assets to operate our wireless network and IT data centers, including tower assets and leasehold improvements and assets related to the liability for the retirement of long-lived assets. Leasehold improvements include asset improvements other than those related to the wireless network. Property and equipment are recorded at cost less accumulated depreciation and impairments, if any, in Property and equipment, net on our Consolidated Balance Sheets. We generally depreciate property and equipment over the period the property and equipment provide economic benefit using the straight-line method. Depreciable life studies are performed periodically to confirm the appropriateness of depreciable lives for certain categories of property and equipment. These studies take into account actual usage, physical wear and tear, replacement history and assumptions about technology evolution. When these factors indicate the useful life of an asset is different from the previous assessment, the remaining book value is depreciated prospectively over the adjusted remaining estimated useful life. Leasehold improvements are depreciated over the shorter of their estimated useful lives or the related lease term. Costs of major replacements and improvements are capitalized. Repair and maintenance expenditures which do not enhance or extend the asset’s useful life are charged to operating expenses as incurred. Construction costs, labor and overhead incurred in the expansion or enhancement of our wireless network are capitalized. Capitalization commences with pre-construction period administrative and technical activities, which include obtaining zoning approvals and building permits, and ceases at the point at which the asset is ready for its intended use. We capitalize interest associated with the acquisition or construction of certain property and equipment. Capitalized interest is reported as a reduction in interest expense and depreciated over the useful life of the related assets. We record an asset retirement obligation for the estimated fair value of legal obligations associated with the retirement of tangible long-lived assets and a corresponding increase in the carrying amount of the related asset in the period in which the obligation is incurred. In periods subsequent to initial measurement, we recognize changes in the liability resulting from the passage of time and revisions to either the timing or the amount of the original estimate. Over time, the liability is accreted to its present value and the capitalized cost is depreciated over the estimated useful life of the asset. Our obligations relate primarily to certain legal obligations to remediate leased property on which our network infrastructure and administrative assets are located. We capitalize certain costs incurred in connection with developing or acquiring internal use software. Capitalization of software costs commences once the final selection of the specific software solution has been made and management authorizes and commits to funding the software project and ceases once the project is ready for its intended use. Capitalized software costs are included in Property and equipment, net in our Consolidated Balance Sheets and are amortized on a straight-line basis over the estimated useful life of the asset. Costs incurred during the preliminary project stage, as well as maintenance and training costs, are expensed as incurred. Device Leases Through the Merger, we acquired device lease contracts in which Sprint is the lessor (the “Sprint Flex Lease Program”), substantially all of which are classified as operating leases, as well as the associated fixed assets (i.e., the leased devices). These leased devices were recorded as fixed assets at their acquisition date fair value and presented within Property and equipment, net on our Consolidated Balance Sheets. Our leasing programs (“Leasing Programs”), which include JUMP! On Demand and the Sprint Flex Lease Program acquired through the Merger, allow customers to lease a device (handset or tablet) over a period of, generally, 18 months and upgrade it for a new device when eligibility requirements are met. We depreciate leased devices to their estimated residual value, on a group basis, using the straight-line method over the estimated useful life of the device. The estimated useful life reflects the period for which we estimate the group of leased devices will provide utility to us, which may be longer than the initial lease term based on customer options in the Sprint Flex Lease program to renew the lease on a month-to-month basis after the initial lease term concludes. In determining the estimated useful life, we consider the lease term (e.g., 18 months and month-to-month renewal options for the Sprint Flex Lease Program), trade-in activity and write-offs for lost and stolen devices. Lost and stolen devices are incorporated into the estimates of depreciation expense and recognized as an adjustment to accumulated depreciation when the loss event occurs. Our policy of using the group method of depreciation has been applied to acquired leased devices as well as leases originated subsequent to the Merger. Acquired leased devices are grouped based on the age of the device. Revenues associated with the leased wireless devices, net of lease incentives, are generally recognized on a straight-line basis over the lease term. For arrangements in which we are the lessor of wireless devices, we separate lease and non-lease components. Upon device upgrade or at lease end, customers in the JUMP! On Demand lease program must return or purchase their device, and customers in the Sprint Flex Lease Program have the option to return or purchase their device or to renew their lease on a month-to-month basis. The purchase price of the device is established at lease commencement and is based on the type of device leased and any down payment made. The Leasing Programs do not contain any residual value guarantees or variable lease payments, and there are no restrictions or covenants imposed by these leases. Returned devices, including those received upon device upgrade, are transferred from Property and equipment, net to Inventory on our Consolidated Balance Sheets and are valued at the lower of cost or net realizable value, with any write-down recognized as Cost of equipment sales in our Consolidated Statements of Comprehensive Income. Other Intangible Assets Intangible assets that do not have indefinite useful lives are amortized over their estimated useful lives. Customer lists and the Sprint trade name are amortized using the sum-of-the-years digits method over the period in which the asset is expected to contribute to future cash flows. The remaining finite-lived intangible assets are amortized using the straight-line method. Goodwill and Indefinite-Lived Intangible Assets Goodwill Goodwill consists of the excess of the purchase price over the fair value of identifiable net assets acquired in a business combination. Goodwill is allocated to our two reporting units, wireless and Layer3. Spectrum Licenses Spectrum licenses are carried at costs incurred to acquire the spectrum licenses and the costs to prepare the spectrum licenses for their intended use, such as costs to clear acquired spectrum licenses. The Federal Communications Commission (“FCC”) issues spectrum licenses which provide us with the exclusive right to utilize designated radio frequency spectrum within specific geographic service areas to provide wireless communications services. While spectrum licenses are issued for a fixed period of time, typically for up to 15 years, the FCC has granted license renewals routinely and at a nominal cost. The spectrum licenses held by us expire at various dates. We believe we will be able to meet all requirements necessary to secure renewal of our spectrum licenses at nominal costs. Moreover, we determined there are currently no legal, regulatory, contractual, competitive, economic or other factors that limit the useful lives of our spectrum licenses. Therefore, we determined the spectrum licenses should be treated as indefinite-lived intangible assets. At times, we enter into agreements to sell or exchange spectrum licenses. Upon entering into the arrangement, if the transaction has been deemed to have commercial substance, spectrum licenses are reviewed for impairment. The licenses are transferred at their carrying value, as adjusted for any impairment recognized, to assets held for sale, which is included in Other current assets in our Consolidated Balance Sheets until approval and completion of the exchange or sale. Upon closing of the transaction, spectrum licenses acquired as part of an exchange of nonmonetary assets are recorded at fair value and the difference between the fair value of the spectrum licenses obtained, carrying value of the spectrum licenses transferred and cash paid, if any, is recognized as a Gain (loss) on disposal of spectrum licenses included in Selling, general and administrative expenses in our Consolidated Statements of Comprehensive Income. Our fair value estimates of spectrum licenses are based on information for which there is little or no observable market data. If the transaction lacks commercial substance or the fair value is not measurable, the acquired spectrum licenses are recorded at our carrying value of the spectrum assets transferred or exchanged. Spectrum Leases Through the Merger, the Company acquired lease agreements (the “Agreements”) with various educational and non-profit institutions that provide us with the right to use FCC spectrum licenses (Educational Broadband Services or “EBS spectrum”) in the 2.5 GHz band. In addition to the Agreements with educational institutions and private owners who hold the licenses, the Company also acquired direct ownership of spectrum licenses previously acquired by Sprint through government auctions or other acquisitions. The Agreements with educational and certain non-profit institutions are typically for five Leased FCC spectrum licenses are recorded as executory contracts whereby, as a result of business combination accounting, an intangible asset or liability is recorded reflecting the extent to which contractual terms are favorable or unfavorable to current market rates. These intangible assets or liabilities are amortized over the estimated remaining useful life of the lease agreements. Contractual lease payments are recognized on a straight-line basis over the remaining term of the arrangement, including renewals, and are presented in Costs of services within our Consolidated Statements of Comprehensive Income. The Agreements enhance the overall value of the Company’s owned spectrum licenses as the collective value is higher than the value of individual bands of spectrum within a specific geography. This value is derived from the ability to provide wireless service to customers across large geographic areas and maintain the same or similar wireless connectivity quality. This enhanced value from combining owned and leased spectrum licenses is referred to as an aggregation premium. The aggregation premium is a component of the overall fair value of our owned FCC spectrum licenses, which are recorded as indefinite-lived intangible assets. Impairment We assess the carrying value of our goodwill and other indefinite-lived intangible assets, such as our spectrum licenses, for potential impairment annually as of December 31, or more frequently if events or changes in circumstances indicate such assets might be impaired. When assessing goodwill for impairment, we may elect to first perform a qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. If we do not perform a qualitative assessment, or if the qualitative assessment indicates it is more likely than not that the fair value of the two reporting units, wireless and Layer3, is less than its carrying amount, we perform a quantitative test. We recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized would not exceed the total amount of goodwill allocated to that reporting unit. We test our spectrum licenses for impairment on an aggregate basis, consistent with our management of the overall business at a national level. We may elect to first perform a qualitative assessment to determine whether it is more likely than not that the fair value of an intangible asset is less than its carrying value. If we do not perform the qualitative assessment, or if the qualitative assessment indicates it is more likely than not that the fair value of the intangible asset is less than its carrying amount, we calculate the estimated fair value of the intangible asset. If the estimated fair value of the spectrum licenses is lower than their carrying amount, an impairment loss is recognized for the difference. We estimate fair value using the Greenfield methodology, which is an income approach based on discounted cash flows associated with the intangible asset, to estimate the price at which an orderly transaction to sell the asset would take place between market participants at the measurement date under current market conditions. Restricted Cash Certain provisions of our debt agreements require us to maintain specified cash collateral balances. Amounts associated with these balances are considered to be restricted cash and are included within Other assets in our Consolidated Balance Sheets. Guarantee Liabilities We offer a device trade-in program, Just Upgrade My Phone (“JUMP!”), which provides eligible customers a specified-price trade-in right to upgrade their device. Upon enrollment, participating customers must finance the purchase of a device on an EIP and have a qualifying T-Mobile monthly wireless service plan. Upon a qualifying JUMP! program upgrade, the customer’s remaining EIP balance is settled provided they trade-in their eligible used device in good working condition and purchase a new device from us on a new EIP. For customers who enroll in JUMP!, we recognize a liability and reduce revenue for the portion of revenue which represents the estimated fair value of the specified-price trade-in right guarantee. The guarantee liability is valued based on various economic and customer behavioral assumptions, which requires judgment, including estimating the customer's remaining EIP balance at trade-in, the expected fair value of the used device at trade-in, and the probability and timing of trade-in. When customers upgrade their device, the difference between the EIP balance credit to the customer and the fair value of the returned device is recorded against the guarantee liabilities. All assumptions are reviewed periodically. Fair Value Measurements We carry certain assets and liabilities at fair value. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The three-tier hierarchy for inputs used in measuring fair value, which prioritizes the inputs based on the observability as of the measurement date, is as follows: Level 1 Quoted prices in active markets for identical assets or liabilities; Level 2 Observable inputs other than the quoted prices in active markets for identical assets and liabilities; and Level 3 Unobservable inputs for which there is little or no market data, which require us to develop assumptions of what market participants would use in pricing the asset or liability. Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the placement of assets and liabilities being measured within the fair value hierarchy. The carrying values of Cash and cash equivalents, Accounts receivable, Accounts receivable from affiliates, Accounts payable and accrued liabilities and borrowings under our vendor financing arrangements approximate fair value due to the short-term maturities of these instruments. The carrying values of EIP receivables approximate fair value as the receivables are recorded at their present value using an imputed interest rate. With the exception of certain long-term fixed-rate debt, there were no financial instruments with a carrying value materially different from their fair value. See Note 7 - Fair Value Measurements for a comparison of the carrying values and fair values of our short-term and long-term debt. Derivative Financial Instruments Derivative financial instruments are recognized as either assets or liabilities and are measured at fair value. We do not use derivatives for trading or speculative purposes. For derivative instruments designated as cash flow hedges associated with forecasted debt issuances, changes in fair value are reported as a component of Accumulated other comprehensive loss until reclassified into Interest expense in the same period the hedged transaction affects earnings, generally over the life of the related debt. Unrealized gains on derivatives designated in qualifying cash flow hedge relationships are recorded at fair value as assets, and unrealized losses are recorded at fair value as liabilities. Revenue Recognition (Effective January 1, 2018) We primarily generate our revenue from providing wireless services to customers and selling or leasing devices and accessories. Our contracts with customers may involve multiple performance obligations, which include wireless services, wireless devices or a combination thereof, and we allocate the transaction price between each performance obligation based on its relative standalone selling price. Significant Judgments The most significant judgments affecting the amount and timing of revenue from contracts with our customers include the following items: • Revenue for service contracts that we assess are not probable of collection is not recognized until the contract is completed or terminated and cash is received. Collectibility is re-assessed when there is a significant change in facts or circumstances. Our assessment of collectibility considers whether we may limit our exposure to credit risk through our right to stop transferring additional service in the event the customer is delinquent as well as certain contract terms such as down payments that reduce our exposure to credit risk. Customer credit behavior is inherently uncertain. See “Receivables and Allowance for Credit Losses” above, for additional discussion on how we assess credit risk. • Promotional EIP bill credits offered to a customer on an equipment sale that are paid over time and are contingent on the customer maintaining a service contract may result in an extended service contract based on whether a substantive penalty is deemed to exist. Determining whether contingent EIP bill credits result in a substantive termination penalty may require significant judgment. • The identification of distinct performance obligations within our service plans may require significant judgment. • Revenue is recorded net of costs paid to another party for performance obligations where we arrange for the other party to transfer goods or services to the customer (i.e., when we are acting as an agent). For example, performance obligations relating to services provided by third-party content providers where we neither control a right to the content provider’s service nor control the underlying service itself are presented net because we are acting as an agent. The determination of whether we control the underlying service or right to the service prior to our transfer to the customer requires, at times, significant judgment. • Our products are generally sold with a right of return, which is accounted for as variable consideration when estimating the amount of revenue to recognize. Device return levels are estimated based on the expected value method as there are a large number of contracts with similar characteristics and the outcome of each contract is independent of the others. Historical return rate experience is a significant input to our expected value methodology. • Sales of equipment to indirect dealers who have been identified as our customer (referred to as the sell-in model) often include credits subsequently paid to the dealer as a reimbursement for any discount promotions offered to the end consumer. These credits (payments to a customer, the dealer) are accounted for as variable consideration when estimating the amount of revenue to recognize from the sales of equipment to indirect dealers and are estimated based on historical experience and other factors, such as expected promotional activity. • The determination of the standalone selling price for contracts that involve more than one performance obligation may require significant judgment, such as when the selling price of a good or service is not readily observable. Wireless Services Revenue We generate our wir

Business Combination

Business Combination	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Business Combination	Note 2 – Business Combination Business Combination Agreement and Amendments On April 29, 2018, we entered into a Business Combination Agreement for the Merger. The Business Combination Agreement was subsequently amended to provide that, following the closing of the Merger and the other transactions contemplated by the Business Combination Agreement (collectively, the “Transactions”), SoftBank Group Corp. (“SoftBank”) would indemnify us against certain specified matters and the loss of value arising out of, or resulting from, cessation of access to spectrum under certain circumstances and subject to certain limitations and qualifications. On February 20, 2020, T-Mobile, SoftBank and Deutsche Telekom AG (“DT”) entered into a letter agreement (the “Letter Agreement”). Pursuant to the Letter Agreement, SoftBank agreed to cause its applicable affiliates to surrender to T-Mobile, for no additional consideration, an aggregate of 48,751,557 shares of T-Mobile common stock (such number of shares, the “SoftBank Specified Shares Amount”), effective immediately following the Effective Time (as defined in the Business Combination Agreement), making SoftBank’s exchange ratio 11.31 shares of Sprint common stock for each share of T-Mobile common stock. This resulted in an effective exchange ratio of approximately 11.00 shares of Sprint common stock for each share of T-Mobile common stock immediately following the closing of the Merger, an increase from the originally agreed 9.75 shares. Sprint stockholders other than SoftBank received the original fixed exchange ratio of 0.10256 shares of T-Mobile common stock for each share of Sprint common stock, or the equivalent of approximately 9.75 shares of Sprint common stock for each share of T-Mobile common stock. The Letter Agreement requires T-Mobile to issue to SoftBank 48,751,557 shares of T-Mobile common stock, subject to the terms and conditions set forth in the Letter Agreement, for no additional consideration, if certain conditions are met. The issuance of these shares is contingent on the trailing 45-day volume-weighted average price per share of T-Mobile common stock on the NASDAQ Global Select Market being equal to or greater than $150.00, at any time during the period commencing on April 1, 2022 and ending on December 31, 2025. If the threshold price is not met, then none of the SoftBank Specified Shares Amount will be issued. Closing of Sprint Merger On April 1, 2020, we completed the Merger, and as a result, Sprint and its subsidiaries became wholly owned consolidated subsidiaries of T-Mobile. Sprint was the fourth-largest telecommunications company in the U.S. offering a comprehensive range of wireless and wireline communication products and services. As a combined company, we expect to be able to rapidly launch a broad and deep nationwide 5G network, accelerate innovation, increase competition in the U.S. wireless, video and broadband industries and achieve significant synergies and cost reductions by eliminating redundancies within the combined network as well as other business processes and operations. We combined the Sprint and T-Mobile operations under the T-Mobile brand nationwide on August 2, 2020. Upon completion of the Merger, each share of Sprint common stock was exchanged for 0.10256 shares of T-Mobile common stock, or 9.75 shares of Sprint common stock for each share of T-Mobile common stock. After adjustments, including the holdback of the SoftBank Specified Shares Amount and fractional shares, we issued 373,396,310 shares of T-Mobile common stock to Sprint stockholders. The fair value of the T-Mobile common stock provided in exchange for Sprint common stock was approximately $31.3 billion. Additional components of consideration included the repayment of certain of Sprint’s debt, replacement equity awards attributable to pre-combination services, contingent consideration and a cash payment received for certain reimbursed Merger expenses. Immediately following the closing of the Merger and the surrender of the SoftBank Specified Shares Amount, pursuant to the Letter Agreement described above, DT and SoftBank held, directly or indirectly, approximately 43.6% and 24.7%, respectively, of the outstanding T-Mobile common stock, with the remaining approximately 31.7% of the outstanding T-Mobile common stock held by other stockholders. Consideration Transferred The acquisition-date fair value of consideration transferred in the Merger totaled $40.8 billion, comprised of the following: (in millions) April 1, 2020 Fair value of T-Mobile common stock issued to Sprint stockholders (1) $ 31,328 Fair value of T-Mobile replacement equity awards attributable to pre-combination service (2) 323 Repayment of Sprint’s debt (including accrued interest and prepayment penalties) (3) 7,396 Value of contingent consideration (4) 1,882 Payment received from selling stockholder (5) (102) Total consideration exchanged $ 40,827 (1) Represents the fair value of T-Mobile common stock issued to Sprint stockholders pursuant to the Business Combination Agreement, less shares surrendered by SoftBank pursuant to the Letter Agreement. The fair value is based on 373,396,310 shares of Sprint common stock issued and outstanding as of March 31, 2020, an exchange ratio of 0.10256 shares of T-Mobile common stock per share of Sprint common stock, less 48,751,557 T-Mobile shares surrendered by SoftBank which are treated as contingent consideration, and the closing price per share of T-Mobile common stock on NASDAQ on March 31, 2020, of $83.90, as shares were transferred to Sprint stockholders prior to the opening of markets on April 1, 2020. (2) Equity-based awards held by Sprint employees prior to the acquisition date have been replaced with T-Mobile equity-based awards. The portion of the equity-based awards that relates to services performed by the employee prior to the acquisition date is included within consideration transferred, and includes stock options, restricted stock units and performance-based restricted stock units. (3) Represents the cash consideration paid concurrent with the close of the Merger to retire certain Sprint debt, as required by change in control provisions of the debt, plus interest and prepayment penalties. (4) Represents the fair value of the SoftBank Specified Shares Amount contingent consideration that may be issued as set forth in the Letter Agreement. (5) Represents receipt of a cash payment from SoftBank for certain expenses associated with the Merger and is presented in Cash paid for acquisition of companies, net of cash acquired within our Consolidated Statements of Cash Flows. The SoftBank Specified Shares Amount was determined to be contingent consideration with an acquisition-date fair value of $1.9 billion. We estimated the fair value using the income approach, a probability-weighted discounted cash flow model, whereby a Monte Carlo simulation method estimated the probability of different outcomes as the likelihood of achieving the 45-day volume-weighted average price threshold is not easily predicted. This fair value measurement is based on significant inputs not observable in the market and, therefore, represents a Level 3 measurement as defined in ASC 820. The key assumptions in applying the income approach include estimated future share-price volatility, which was based on historical market trends and estimated future performance of T-Mobile. The maximum amount of contingent consideration that could be issued to SoftBank has an estimated value of $7.3 billion, based on SoftBank Specified Shares Amount of 48,751,557 multiplied by the defined volume-weighted average price per share of $150.00. The contingent consideration that could be delivered to SoftBank is classified within equity and is not subject to remeasurement. Fair Value of Assets Acquired and Liabilities Assumed We accounted for the Merger as a business combination. The identifiable assets acquired and liabilities assumed of Sprint were recorded at their estimated fair values as of the acquisition date and consolidated with those of T-Mobile. Assigning fair market values to the assets acquired and liabilities assumed at the date of an acquisition requires the use of significant judgment regarding estimates and assumptions. For the estimated fair values of the assets acquired and liabilities assumed, we used the cost, income and market approaches, including market participant assumptions. The following table summarizes the estimated fair values for each major class of assets acquired and liabilities assumed at the acquisition date. We retained the services of certified valuation specialists to assist with assigning estimated values to certain acquired assets and assumed liabilities. As of December 31, 2020, the valuation of assets acquired and liabilities assumed is substantially complete except for the finalization of certain aspects of spectrum valuation, the valuation of certain income tax matters and loss contingencies. (in millions) April 1, 2020 Cash and cash equivalents $ 2,084 Accounts receivable 1,781 Equipment installment plan receivables 1,088 Inventory 658 Prepaid expenses 140 Assets held for sale 1,908 Other current assets 631 Property and equipment 18,435 Operating lease right-of-use assets 6,583 Financing lease right-of-use assets 291 Goodwill 9,401 Spectrum licenses 45,400 Other intangible assets 6,325 Equipment installment plan receivables due after one year, net 247 Other assets (1) 540 Total assets acquired 95,512 Accounts payable and accrued liabilities 4,944 Short-term debt 2,760 Deferred revenue 508 Short-term operating lease liabilities 1,818 Short-term financing lease liabilities 8 Liabilities held for sale 475 Other current liabilities 671 Long-term debt 29,037 Tower obligations 950 Deferred tax liabilities 3,513 Operating lease liabilities 5,615 Financing lease liabilities 12 Other long-term liabilities 4,374 Total liabilities assumed 54,685 Total consideration transferred $ 40,827 (1) Included in Other assets acquired is $80 million in restricted cash. Amounts previously disclosed for the estimated values of certain acquired assets and liabilities assumed have been revised based on additional information arising subsequent to the initial valuation. Significant Measurement Period Adjustments During the year ended December 31, 2020, we recognized measurement period adjustments to reflect facts and circumstances in existence as of the date of the Merger. These adjustments included: • An increase of $1.2 billion in Property and equipment related to the finalization of valuations related to certain tower assets and an increase of $1.7 billion in Other long-term liabilities associated with contract terms that are unfavorable to market terms. See Note 9 – Tower Obligations for further information; and • A decrease of $690 million in Deferred tax liabilities resulting from a $357 million reclassification from deferred tax liabilities to current liabilities and the continued assessment of valuation allowance necessary as of the date of the Merger along with tax effecting measurement period adjustments. See Note 13 - Income Taxes for further information. The measurement period adjustments did not have a significant impact on our Consolidated Statement of Comprehensive Income for the year ended December 31, 2020. The net impact of the measurement period adjustments resulted in a net increase to goodwill. Intangible Assets and Liabilities Goodwill with a provisionally assigned value of $9.4 billion represents the excess of the consideration transferred over the estimated fair values of assets acquired and liabilities assumed. The preliminary goodwill recognized includes synergies expected to be achieved from the operations of the combined company, the assembled workforce of Sprint and intangible assets that do not qualify for separate recognition. Expected synergies include the cost savings from the planned integration of network infrastructure, facilities, personnel and systems. None of the goodwill resulting from the Merger is deductible for tax purposes. All of the goodwill acquired is allocated to the wireless reporting unit. Other intangible assets include $4.9 billion of customer relationships with a weighted-average useful life of eight years and tradenames of $207 million with a useful life of two years. Leased spectrum arrangements that have favorable (asset) and unfavorable (liability) terms compared to current market rates were assigned preliminary fair values of $790 million and $197 million, respectively, with 18 year and 19 year weighted average useful lives, respectively. The preliminary fair value of Spectrum licenses of $45.4 billion was estimated using the income approach, specifically a Greenfield model. This fair value measurement is based on significant inputs not observable in the market and, therefore, represents a Level 3 measurement as defined in ASC 820. The key assumptions in applying the income approach include the discount rate, market share, estimated capital and operating expenditures, forecasted service revenue and long-term growth rate for a hypothetical market participant that enters the wireless industry and builds a nationwide wireless network. Acquired Receivables The fair value of the assets acquired include Accounts receivable of $1.8 billion and EIP receivables of $1.3 billion. The unpaid principal balance under these contracts as of the Merger date was $1.8 billion and $1.6 billion, respectively. The difference between the fair value and the unpaid principal balance primarily represents amounts expected to be uncollectible. Indemnification Assets and Contingent Liabilities Pursuant to Amendment No 2. to the Business Combination Agreement, SoftBank agreed to indemnify us against certain specified matters and losses. As of December 31, 2020, we have recorded a contingent liability and an offsetting indemnification asset for the expected reimbursement by SoftBank for certain Lifeline matters that have not been resolved. The liability is presented in Accounts payable and accrued liabilities, and the indemnification asset is presented in Other current assets within our Consolidated Balance Sheets. In November 2020, we entered into a consent decree with the FCC to resolve certain Lifeline matters, which resulted in a payment of $200 million by SoftBank. We expect that any additional liabilities related to these indemnified matters would be indemnified and reimbursed by SoftBank. Transaction Costs We recognized transaction costs of $201 million, $106 million and $71 million for the years ended December 31, 2020, 2019 and 2018, respectively. These costs were associated with legal and professional services and were recognized as Selling, general and administrative expenses in our Consolidated Statements of Comprehensive Income. Pro Forma Information The following unaudited pro forma financial information gives effect to the Transactions as if they had been completed on January 1, 2019. The unaudited pro forma information was prepared in accordance with the requirements of ASC 805, which is a different basis than pro forma information prepared under Article 11 of Regulation S-X (“Article 11”). As such, they are not directly comparable with historical results for stand-alone T-Mobile prior to April 1, 2020, historical results for T-Mobile from April 1, 2020 that reflect the Transactions and are inclusive of the results and operations of Sprint, nor our previously provided pro forma financials prepared in accordance with Article 11. The pro forma results for the years ended December 31, 2020 and 2019 include the impact of several adjustments to previously reported operating results. The pro forma adjustments are based on historically reported transactions by the respective companies. The pro forma results do not include any anticipated synergies or other expected benefits of the acquisition. Year Ended December 31, (in millions, except per share amounts) 2020 2019 Total revenues $ 74,681 $ 70,607 Income from continuing operations 3,302 185 Income from discontinued operations, net of tax 677 1,594 Net income 3,979 1,792 Significant nonrecurring pro forma adjustments include: • Transaction costs of $559 million are assumed to have occurred on January 1, 2019, and are recognized as if incurred in the first quarter of 2019; • The Prepaid Business divested on July 1, 2020, is assumed to have been classified as discontinued operations as of January 1, 2019, and the related activities are presented in Income from discontinued operations, net of tax; • Permanent financing issued and debt redemptions occurring in connection with the closing of the Merger are assumed to have occurred on January 1, 2019, and historical interest expense associated with repaid borrowings is removed; • Tangible and intangible assets are assumed to be recorded at their estimated fair values as of the pro forma close date of January 1, 2019 and are depreciated or amortized over their estimated useful lives; and • Accounting policies of Sprint are conformed to those of T-Mobile including depreciation for leased devices, Brightstar distribution, amortization of costs to acquire a contract and certain tower lease transactions as described in Note 1 - Summary of Significant Accounting Policies and Note 9 - Tower Obligations . The selected unaudited pro forma condensed combined financial information is provided for illustrative purposes only and does not purport to represent what the actual consolidated results of operations would have been had the Transactions actually occurred on January 1, 2019, nor do they purport to project the future consolidated results of operations. For the periods subsequent to the Merger close date, the acquired Sprint subsidiaries contributed total revenues and operating income of $20.5 billion and $1.3 billion, respectively, for the year ended December 31, 2020, that were included in our Consolidated Statements of Comprehensive Income. Financing In connection with the entry into the Business Combination Agreement, T-Mobile USA, Inc. (“T-Mobile USA”) entered into a commitment letter, dated as of April 29, 2018 (as amended and restated on May 15, 2018 and on September 6, 2019, the “Commitment Letter”). On April 1, 2020, in connection with the closing of the Merger, we drew down on our $19.0 billion New Secured Bridge Loan Facility and our $4.0 billion New Secured Term Loan Facility (each as defined below). We used the net proceeds from the drawdown of the secured facilities to refinance certain existing debt of us, Sprint and our and Sprint’s respective subsidiaries and for post-closing general corporate purposes of the combined company. See Note 8 – Debt for further information. In connection with the financing provided for in the Commitment Letter, we incurred certain fees payable to the financial institutions. On April 1, 2020, in connection with the closing of the Merger, we paid $355 million in Commitment Letter fees to certain financial institutions. See Note 8 – Debt for further information. In connection with the entry into the Business Combination Agreement, DT and T-Mobile USA entered into a Financing Matters Agreement, dated as of April 29, 2018 (the “Financing Matters Agreement”), pursuant to which DT agreed, among other things, to consent to, subject to certain conditions, amendments to certain existing debt owed to DT, in connection with the Merger. On April 1, 2020, in connection with the closing of the Merger, we made a payment for requisite consents to DT of $13 million. See Note 8 – Debt for further information. On May 18, 2018, under the terms and conditions described in the Consent Solicitation Statement dated as of May 14, 2018 (the “Consent Solicitation Statement”), we obtained consents necessary to effect amendments to certain existing debt of us and our subsidiaries. On April 1, 2020, in connection with the closing of the Merger, we made payments for requisite consents to third-party note holders of $95 million. See Note 8 – Debt for further information. Regulatory Matters The Transactions were the subject of various legal and regulatory proceedings involving a number of state and federal agencies. In connection with those proceedings and the approval of the Transactions, we have certain commitments and other obligations to various state and federal agencies and certain nongovernmental organizations. See Note 1 8 - Commitments and Contingencies for further information. Prepaid Transaction On July 26, 2019, we entered into the Asset Purchase Agreement with Sprint and DISH, pursuant to which, following the consummation of the Merger, DISH would acquire the Prepaid Business. On June 17, 2020, T-Mobile, Sprint and DISH entered into the First Amendment to the Asset Purchase Agreement. Pursuant to the First Amendment of the Asset Purchase Agreement, T-Mobile, Sprint and DISH agreed to proceed with the closing of the Prepaid Transaction in accordance with the Asset Purchase Agreement on July 1, 2020, subject to the terms and conditions of the Asset Purchase Agreement and the terms and conditions of the Consent Decree. On July 1, 2020, pursuant to the Asset Purchase Agreement, we completed the Prepaid Transaction. Upon closing of the Prepaid Transaction, we received $1.4 billion from DISH for the Prepaid Business, subject to working capital adjustments. See Note 12 - Discontinued Operations for further information. Shenandoah Personal Communications Company Affiliate Relationship Sprint PCS (specifically Sprint Spectrum L.P.) is party to a variety of publicly filed agreements with Shenandoah Personal Communications Company LLC (“Shentel”), pursuant to which Shentel is the exclusive provider of Sprint PCS’s wireless mobility communications network products in certain parts of Maryland, North Carolina, Virginia, West Virginia, Kentucky, Ohio and Pennsylvania. Pursuant to one such agreement, the Sprint PCS Management Agreement, dated November 5, 1999 (as amended, supplemented and modified from time to time, the “Management Agreement”), Sprint PCS was granted an option to purchase Shentel’s wireless telecommunications assets used to provide services pursuant to the Management Agreement. On August 26, 2020, Sprint, now our direct subsidiary, on behalf of and as the direct or indirect owner of Sprint PCS, exercised its option by delivering a binding notice of exercise to Shentel. The exercise of this option triggered a requirement for the parties to engage three independent valuation providers (the “Valuation Providers”) to calculate the “entire business value” (the “Entire Business Value”) of such wireless telecommunications assets, pursuant to a formula and valuation process prescribed in the Management Agreement. Subsequent to December 31, 2020, on February 1, 2021, in accordance with the Management Agreement and other agreed-upon terms, the Valuation Providers determined and calculated the Entire Business Value of Shentel’s wireless telecommunication assets used to provide services pursuant to the Management Agreement to be $2.1 billion, and correspondingly, the base purchase price for such wireless telecommunication assets shall be ninety percent (90%) of that Entire Business Value amount ($1.9 billion), subject to certain other purchase price adjustments prescribed by the Management Agreement and such additional purchase price adjustments agreed by the parties. The parties are negotiating the remaining outstanding terms of a definitive agreement to govern the purchase of Shentel’s wireless telecommunication assets and expect the transaction to close in the second quarter of 2021 after satisfying customary conditions to closing.

Receivables and Expected Credit

Receivables and Expected Credit Losses	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Receivables and Expected Credit Losses	Note 3 – Receivables and Expected Credit Losses Our portfolio of receivables is comprised of two portfolio segments: accounts receivable and EIP receivables. Accounts Receivable Portfolio Segment Our accounts receivable segment primarily consists of amounts currently due from customers, including service and leased device receivables, device insurance administrators, wholesale partners, third-party retail channels and other carriers. We estimate expected credit losses associated with our accounts receivable portfolio using an aging schedule methodology that utilizes historical information and current conditions to develop expected credit losses by aging bucket, including for receivables that are not past due. To determine the appropriate credit loss percentages by aging bucket, we consider a number of factors, including our overall historical credit losses, net of recoveries and timely payment experience as well as current collection trends such as write-off frequency and severity, credit quality of the customer base, and other qualitative factors such as macro-economic conditions, including the expected economic impacts of the Pandemic. We consider the need to adjust our estimate of expected credit losses for reasonable and supportable forecasts of future economic conditions. To do so, we monitor professional forecasts of changes in real U.S. gross domestic product and forecasts of consumer credit behavior for comparable credit exposures. We also periodically evaluate other economic indicators such as unemployment rates to assess their level of correlation with our historical credit loss statistics. EIP Receivables Portfolio Segment Based upon customer credit profiles at the time of customer origination, we classify the EIP receivables segment into two customer classes of “Prime” and “Subprime.” Prime customer receivables are those with lower credit risk and Subprime customer receivables are those with higher credit risk. Customers may be required to make a down payment on their equipment purchases. In addition, certain customers within the Subprime category are required to pay an advance deposit. To determine a customer’s credit profile, we use a proprietary credit scoring model that measures the credit quality of a customer using several factors, such as credit bureau information, consumer credit risk scores and service and device plan characteristics. Installment loans acquired in the Merger are included in EIP receivables. We applied our proprietary credit scoring model to the customers acquired in the Merger with an outstanding EIP receivable balance. Based on tenure, consumer credit risk score and credit profile, these acquired customers were classified into our customer classes of Prime or Subprime. Our proprietary credit scoring model is applied to all EIP arrangements originated after the Merger close date. The following table summarizes the EIP receivables, including imputed discounts and related allowance for credit losses: (in millions) December 31, December 31, EIP receivables, gross (1) $ 6,213 $ 4,582 Unamortized imputed discount (325) (299) EIP receivables, net of unamortized imputed discount 5,888 4,283 Allowance for credit losses (2) (280) (100) EIP receivables, net of allowance for credit losses and imputed discount $ 5,608 $ 4,183 Classified on the balance sheet as: Equipment installment plan receivables, net of allowance for credit losses and imputed discount $ 3,577 $ 2,600 Equipment installment plan receivables due after one year, net of allowance for credit losses and imputed discount 2,031 1,583 EIP receivables, net of allowance for credit losses and imputed discount $ 5,608 $ 4,183 (1) Through the Merger, we acquired EIP receivables with a fair value of $1.3 billion as of April 1, 2020. As they were recorded at fair value, an imputed discount was not recognized on the acquired receivables. (2) Allowance for credit losses as of December 31, 2020 was impacted by the cumulative effect of initially applying the new credit loss standard on our receivables portfolio on January 1, 2020, which resulted in an increase to our allowance for credit losses of $91 million. We manage our EIP receivables portfolio using delinquency and customer credit class as key credit quality indicators. As a part of the adoption of the new credit loss standard, we now disclose our EIP receivables portfolio disaggregated by origination year. EIP receivables acquired through the Merger are also presented by origination year. The following table presents the amortized cost of our EIP receivables by delinquency status, customer credit class, and year of origination as of December 31, 2020. Originated in 2020 Originated in 2019 Originated prior to 2019 Total EIP Receivables, net of (in millions) Prime Subprime Prime Subprime Prime Subprime Prime Subprime Grand total Current - 30 days past due $ 2,654 $ 2,035 $ 528 $ 407 $ 124 $ 26 $ 3,306 $ 2,468 $ 5,774 31 - 60 days past due 16 30 6 12 1 — 23 42 65 61 - 90 days past due 4 13 2 5 — — 6 18 24 More than 90 days past due 3 11 2 6 1 2 6 19 25 EIP receivables, net of unamortized imputed discount $ 2,677 $ 2,089 $ 538 $ 430 $ 126 $ 28 $ 3,341 $ 2,547 $ 5,888 We estimate expected credit losses on our EIP receivables by using historical data adjusted for current conditions to calculate default probabilities for our outstanding EIP loans. We consider various risk characteristics when calculating default probabilities, such as how long such loans have been outstanding, customer credit ratings, customer tenure, delinquency status and other correlated variables identified through statistical analyses. We multiply these estimated default probabilities by our estimated loss given default, which considers recoveries. As we do for our accounts receivable portfolio segment, we consider the need to adjust our estimate of expected losses on EIP receivables for reasonable and supportable forecasts of economic conditions through monitoring of external professional forecasts and periodic internal statistical analyses, including the expected economic impacts of the Pandemic. For EIP receivables acquired in the Merger, the difference between the fair value and unpaid principal balance of the loan at the acquisition date is accreted to interest income over the contractual life of the loan using the effective interest method. EIP receivables had a combined weighted average effective interest rate of 6.7% and 8.8% as of December 31, 2020 and 2019, respectively. Activity for the years ended December 31, 2020, 2019 and 2018 in the allowance for credit losses and unamortized imputed discount balances for the accounts receivable and EIP receivables segments were as follows: December 31, 2020 December 31, 2019 December 31, 2018 (in millions) Accounts Receivable Allowance EIP Receivables Allowance Total Accounts Receivable Allowance EIP Receivables Allowance Total Accounts Receivable Allowance EIP Receivables Allowance Total Allowance for credit losses and imputed discount, beginning of period $ 61 $ 399 $ 460 $ 67 $ 449 $ 516 $ 86 $ 396 $ 482 Beginning balance adjustment due to implementation of the new credit loss standard — 91 91 — — — — — — Bad debt expense 338 264 602 77 230 307 69 228 297 Write-offs, net of recoveries (205) (175) (380) (83) (249) (332) (88) (240) (328) Change in imputed discount on short-term and long-term EIP receivables N/A 171 171 N/A 136 136 N/A 250 250 Impact on the imputed discount from sales of EIP receivables N/A (145) (145) N/A (167) (167) N/A (185) (185) Allowance for credit losses and imputed discount, end of period $ 194 $ 605 $ 799 $ 61 $ 399 $ 460 $ 67 $ 449 $ 516 Off-Balance-Sheet Credit Exposures We do not have material, unmitigated off-balance-sheet credit exposures as of December 31, 2020. In connection with the sales of certain service and EIP accounts receivable pursuant to the sale arrangements, we have deferred purchase price assets included in our Consolidated Balance Sheets measured at fair value that are based on a discounted cash flow model using unobservable Level 3 inputs, including customer default rates and credit worthiness, dilutions and recoveries. See Note 4 – Sales of Certain Receivables for further information.

Sales of Certain Receivables

Sales of Certain Receivables	12 Months Ended
	Dec. 31, 2020
Transfers and Servicing [Abstract]
Sales of Certain Receivables	Note 4 – Sales of Certain Receivables We have entered into transactions to sell certain service accounts receivable and EIP receivables. The transactions, including our continuing involvement with the sold receivables and the respective impacts to our consolidated financial statements, are described below. In conjunction with the Merger, the total principal amount outstanding under Sprint’s accounts receivable facility of $2.3 billion was repaid on April 1, 2020, and the facility was terminated. Sales of Service Accounts Receivable Overview of the Transaction In 2014, we entered into an arrangement to sell certain service accounts receivable on a revolving basis (the “service receivable sale arrangement”). The maximum funding commitment of the service receivable sale arrangement is $950 million, and the facility expires in March 2021. As of December 31, 2020 and 2019, the service receivable sale arrangement provided funding of $772 million and $924 million, respectively. Sales of receivables occur daily and are settled on a monthly basis. The receivables consist of service charges currently due from customers and are short-term in nature. In connection with the service receivable sale arrangement, we formed a wholly owned subsidiary, which qualifies as a bankruptcy remote entity, to sell service accounts receivable (the “Service BRE”). The Service BRE does not qualify as a VIE, and due to the significant level of control we exercise over the entity, it is consolidated. Pursuant to the service receivable sale arrangement, certain of our wholly owned subsidiaries transfer selected receivables to the Service BRE. The Service BRE then sells the receivables to an unaffiliated entity (the “Service VIE”), which was established to facilitate the sale of beneficial ownership interests in the receivables to certain third parties. Variable Interest Entity We determined that the Service VIE qualifies as a VIE as it lacks sufficient equity to finance its activities. We have a variable interest in the Service VIE but are not the primary beneficiary as we lack the power to direct the activities that most significantly impact the Service VIE’s economic performance. Those activities include committing the Service VIE to legal agreements to purchase or sell assets, selecting which receivables are purchased in the service receivable sale arrangement, determining whether the Service VIE will sell interests in the purchased service receivables to other parties, funding of the entity and servicing of receivables. We do not hold the power to direct the key decisions underlying these activities. For example, while we act as the servicer of the sold receivables, which is considered a significant activity of the Service VIE, we are acting as an agent in our capacity as the servicer, and the counterparty to the service receivable sale arrangement has the ability to remove us as the servicing agent of the receivables at will with no recourse available to us. As we have determined we are not the primary beneficiary, the balances and results of the Service VIE are not included in our consolidated financial statements. The following table summarizes the carrying amounts and classification of assets, which consist primarily of the deferred purchase price, and liabilities included in our Consolidated Balance Sheets that relate to our variable interest in the Service VIE: (in millions) December 31, December 31, Other current assets $ 378 $ 350 Accounts payable and accrued liabilities — 25 Other current liabilities 357 342 Sales of EIP Receivables Overview of the Transaction In 2015, we entered into an arrangement to sell certain EIP accounts receivable on a revolving basis (the “EIP sale arrangement”). The maximum funding commitment of the sale arrangement is $1.3 billion. In February 2020, we amended the sale arrangement to provide for an alternative advance rate methodology for the EIP accounts receivable sold in the sale arrangement and to make certain other administrative changes. On November 2, 2020, we extended the scheduled expiration date of the EIP sale arrangement to November 18, 2021. On April 30, 2020, we agreed with the purchaser banks to update our collection policies to temporarily allow for flexibility for modifications to the accounts receivable sold that are impacted by COVID-19 and exclusion of such accounts receivable from all pool performance triggers. As of both December 31, 2020 and 2019, the EIP sale arrangement provided funding of $1.3 billion. Sales of EIP receivables occur daily and are settled on a monthly basis. In connection with this EIP sale arrangement, we formed a wholly owned subsidiary, which qualifies as a bankruptcy remote entity (the “EIP BRE”). Pursuant to the EIP sale arrangement, our wholly owned subsidiary transfers selected receivables to the EIP BRE. The EIP BRE then sells the receivables to a non-consolidated and unaffiliated third-party entity over which we do not exercise any level of control, nor does the third-party entity qualify as a VIE. Variable Interest Entity We determined that the EIP BRE is a VIE as its equity investment at risk lacks the obligation to absorb a certain portion of its expected losses. We have a variable interest in the EIP BRE and have determined that we are the primary beneficiary based on our ability to direct the activities which most significantly impact the EIP BRE’s economic performance. Those activities include selecting which receivables are transferred into the EIP BRE and sold in the EIP sale arrangement and funding of the EIP BRE. Additionally, our equity interest in the EIP BRE obligates us to absorb losses and gives us the right to receive benefits from the EIP BRE that could potentially be significant to the EIP BRE. Accordingly, we include the balances and results of operations of the EIP BRE in our consolidated financial statements. The following table summarizes the carrying amounts and classification of assets, which consist primarily of the deferred purchase price, and liabilities included in our Consolidated Balance Sheets of the EIP BRE: (in millions) December 31, December 31, Other current assets $ 388 $ 344 Other assets 120 89 Other long-term liabilities 4 18 In addition, the EIP BRE is a separate legal entity with its own separate creditors who will be entitled, prior to any liquidation of the EIP BRE, to be satisfied prior to any value in the EIP BRE becoming available to us. Accordingly, the assets of the EIP BRE may not be used to settle our general obligations and creditors of the EIP BRE have limited recourse to our general credit. Sales of Receivables The transfers of service receivables and EIP receivables to the non-consolidated entities are accounted for as sales of financial assets. Once identified for sale, the receivable is recorded at the lower of cost or fair value. Upon sale, we derecognize the net carrying amount of the receivables. We recognize the cash proceeds received upon sale in Net cash provided by operating activities in our Consolidated Statements of Cash Flows. We recognize proceeds net of the deferred purchase price, consisting of a receivable from the purchasers that entitles us to certain collections on the receivables. We recognize the collection of the deferred purchase price in Net cash used in investing activities in our Consolidated Statements of Cash Flows as Proceeds related to beneficial interests in securitization transactions. The deferred purchase price represents a financial asset that is primarily tied to the creditworthiness of the customers and which can be settled in such a way that we may not recover substantially all of our recorded investment, due to default by the customers on the underlying receivables. At inception, we elected to measure the deferred purchase price at fair value with changes in fair value included in Selling, general and administrative expense in our Consolidated Statements of Comprehensive Income. The fair value of the deferred purchase price is determined based on a discounted cash flow model which uses primarily unobservable inputs (Level 3 inputs), including customer default rates. As of December 31, 2020 and 2019, our deferred purchase price related to the sales of service receivables and EIP receivables was $884 million and $781 million, respectively. The following table summarizes the impact of the sale of certain service receivables and EIP receivables in our Consolidated Balance Sheets: (in millions) December 31, December 31, Derecognized net service receivables and EIP receivables $ 2,528 $ 2,584 Other current assets 766 694 of which, deferred purchase price 764 692 Other long-term assets 120 89 of which, deferred purchase price 120 89 Accounts payable and accrued liabilities — 25 Other current liabilities 357 342 Other long-term liabilities 4 18 Net cash proceeds since inception 1,715 1,944 Of which: Change in net cash proceeds during the year-to-date period (229) 65 Net cash proceeds funded by reinvested collections 1,944 1,879 We recognized losses from sales of receivables, including adjustments to the receivables’ fair values and changes in fair value of the deferred purchase price, of $36 million, $130 million and $157 million for the years ended December 31, 2020, 2019 and 2018, respectively, in Selling, general and administrative expense in our Consolidated Statements of Comprehensive Income. Continuing Involvement Pursuant to the sale arrangements described above, we have continuing involvement with the service receivables and EIP receivables we sell as we service the receivables and are required to repurchase certain receivables, including ineligible receivables, aged receivables and receivables where write-off is imminent. We continue to service the customers and their related receivables, including facilitating customer payment collection, in exchange for a monthly servicing fee. As the receivables are sold on a revolving basis, the customer payment collections on sold receivables may be reinvested in new receivable sales. At the direction of the purchasers of the sold receivables, we apply the same policies and procedures while servicing the sold receivables as we apply to our owned receivables, and we continue to maintain normal relationships with our customers. Pursuant to the EIP sale arrangement, under certain circumstances, we are required to deposit cash or replacement EIP receivables primarily for contracts terminated by customers under our JUMP! On Demand program. In addition, we have continuing involvement with the sold receivables as we may be responsible for absorbing additional credit losses pursuant to the sale arrangements. Our maximum exposure to loss related to the involvement with the service receivables and EIP receivables sold under the sale arrangements was $1.2 billion as of December 31, 2020. The maximum exposure to loss, which is a required disclosure under U.S. GAAP, represents an estimated loss that would be incurred under severe, hypothetical circumstances whereby we would not receive the deferred purchase price portion of the contractual proceeds withheld by the purchasers and would also be required to repurchase the maximum amount of receivables pursuant to the sale arrangements without consideration for any recovery. We believe the probability of these circumstances occurring is remote and the maximum exposure to loss is not an indication of our expected loss.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment	Note 5 – Property and Equipment The components of property and equipment were as follows: (in millions) Useful Lives December 31, December 31, Land $ 236 $ — Buildings and equipment Up to 30 years 4,006 2,587 Wireless communications systems Up to 20 years 49,453 34,353 Leasehold improvements Up to 12 years 1,879 1,345 Capitalized software Up to 10 years 16,412 12,705 Leased wireless devices Up to 19 months 6,989 1,139 Construction in progress 4,595 2,973 Accumulated depreciation and amortization (42,395) (33,118) Property and equipment, net $ 41,175 $ 21,984 Total depreciation expense relating to property and equipment and financing lease right-of-use assets was $13.1 billion, $6.5 billion and $6.4 billion for the years ended December 31, 2020, 2019 and 2018, respectively. These amounts include depreciation expense related to leased wireless devices of $3.1 billion, $543 million and $940 million for the years ended December 31, 2020, 2019 and 2018, respectively. We capitalize interest associated with the acquisition or construction of certain property and equipment and spectrum intangible assets. We recognized capitalized interest of $440 million, $473 million and $362 million for the years ended December 31, 2020, 2019 and 2018, respectively. Asset retirement obligations are primarily for certain legal obligations to remediate leased property on which our network infrastructure and administrative assets are located. Activity in our asset retirement obligations was as follows: (in millions) Year Ended Year Ended Asset retirement obligations, beginning of year $ 659 $ 609 Fair value of liabilities acquired through Merger 1,110 — Liabilities incurred 16 35 Liabilities settled (40) (2) Accretion expense 55 32 Changes in estimated cash flows 17 (15) Asset retirement obligations, end of period $ 1,817 $ 659 Classified on the balance sheet as: Other current liabilities $ 14 $ — Other long-term liabilities 1,803 659 The corresponding assets, net of accumulated depreciation, related to asset retirement obligations were $912 million and $159 million as of December 31, 2020 and 2019, respectively. Postpaid Billing System Impairment In connection with the continuing integration of the businesses following the Merger, we evaluated the long-term billing system architecture strategy for our postpaid customers. In order to facilitate customer migration from the Sprint legacy billing platform, our postpaid billing system replacement plan and associated development will no longer serve our future needs. As a result, we recorded a non-cash impairment of $200 million related to capitalized software development costs for the year ended December 31, 2020, all of which relates to the impairment recognized during the three months ended June 30, 2020. The expense is included within Impairment expense in our Consolidated Statements of Comprehensive Income. There were no impairments recognized for the years ended December 31, 2019 and 2018.

Goodwill, Spectrum License Tran

Goodwill, Spectrum License Transactions and Other Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, Spectrum License Transactions and Other Intangible Assets	Note 6 – Goodwill, Spectrum License Transactions and Other Intangible Assets Goodwill The changes in the carrying amount of goodwill for the years ended December 31, 2020 and 2019, are as follows: (in millions) Goodwill Historical goodwill, net of accumulated impairment losses of $10,766 $ 1,901 Goodwill from acquisition in 2019 29 Balance as of December 31, 2019 1,930 Goodwill from acquisitions in 2020 9,405 Layer3 goodwill impairment (218) Balance as of December 31, 2020 $ 11,117 Accumulated impairment losses at December 31, 2020 $ (10,984) On April 1, 2020, we completed our Merger with Sprint, which was accounted for as a business combination resulting in $9.4 billion in goodwill. The acquired goodwill was allocated to the wireless reporting unit and will be tested for impairment at this level. See Note 2 - Business Combination for further information. Goodwill Impairment Assessment Certain non-financial assets, including goodwill and indefinite-lived intangible assets such as Spectrum licenses, are not required to be measured at fair value on a recurring basis and are reported at carrying value. However, these assets are required to be assessed for impairment when events or circumstances indicate that carrying value may not be recoverable, and at least annually for goodwill and indefinite-lived intangible assets. The nonrecurring measurements of the fair value of these assets, for which observable market information may be limited, are classified within Level 3 of the fair value hierarchy. In the event an impairment is required, the asset is adjusted to its estimated fair value using market-based assumptions, to the extent they are available, as well as other assumptions that may require significant judgement. For our assessment of the wireless reporting unit we employed a qualitative approach. The fair value of the wireless reporting unit is estimated using a market approach, which is based on market capitalization. We recognize market capitalization is subject to volatility and will monitor changes in market capitalization to determine whether declines, if any, necessitate an interim impairment review. In the event market capitalization does decline below its book value, we will consider the length, severity and reasons for the decline when assessing whether potential impairment exists, including considering whether a control premium should be added to the market capitalization. We believe short-term fluctuations in share price may not necessarily reflect the underlying aggregate fair value. No events or change in circumstances have occurred that indicate the fair value of the wireless reporting unit may be below its carrying amount at December 31, 2020. Our enhanced in-home broadband opportunity following the Merger, along with the acquisition of certain content rights, has created a strategic shift in our TVision TM services offering, allowing us the ability to develop a video product that will be complementary to the in-home broadband offering. As a result of the change in the stand-alone product offering plans and timing, we completed an interim goodwill impairment analysis for the Layer3 reporting unit and recognized a goodwill impairment of $218 million for the year ended December 31, 2020, all of which relates to the impairment recognized during the three months ended June 30, 2020. This impairment reduced the goodwill assigned to the Layer3 reporting unit to zero. The expense is included within Impairment expense in our Consolidated Statements of Comprehensive Income. There were no goodwill impairments recognized for the years ended December 31, 2019 and 2018. Application of the goodwill impairment test requires judgment including the determination of the fair value of the reporting unit. We employed an income approach to assess the fair value of the Layer3 reporting unit based on the present value of estimated future cash flows. Inherent in our preparation of cash flow projections are assumptions and estimates derived from a review of our business plans, expected growth rates, cost of capital and tax rates. We also made certain forecasts about future business strategies and economic conditions, market data, and other assumptions, such as estimates of subscribers for TVision TM services, average revenue and content cost per subscriber. The discount rate used was based on the weighted average cost of capital adjusted for the risk associated with business-specific characteristics and the uncertainty related to the business’s ability to execute on the projected cash flows. As of December 31, 2020, Goodwill was only assigned to the wireless reporting unit as the Goodwill assigned to the Layer3 reporting unit was written-off to a zero balance during the year ended December 31, 2020. Intangible Assets Identifiable Intangible Assets Acquired The following table summarizes the fair value of the intangible assets acquired in the Merger: Weighted Average Useful Life (in years) Fair Value as of April 1, 2020 Spectrum licenses Indefinite-lived $ 45,400 Tradenames (1) 2 years 207 Customer relationships 8 years 4,900 Favorable spectrum leases 18 years 790 Other intangible assets 7 years 428 Total intangible assets acquired $ 51,725 (1) Tradenames include the Sprint brand Spectrum licenses are issued for a fixed period of time, typically up to 15 years; however, the FCC has granted license renewals routinely and at a nominal cost. The spectrum licenses acquired expire at various dates and we believe we will be able to meet all requirements necessary to secure renewal of our spectrum licenses at a nominal cost. Moreover, we determined that there are currently no legal, regulatory, contractual, competitive, economic or other factors that limit the useful lives of our spectrum licenses. Therefore, we determined the spectrum licenses should be treated as indefinite-lived intangible assets. The fair value of spectrum licenses includes the value associated with aggregating a nationwide portfolio of owned and leased spectrum. Favorable spectrum leases represent a lease contract where the market rate is higher than the future contractual lease payments. We lease this spectrum from third parties who hold the spectrum licenses. As these contracts pertain to intangible assets, they are excluded from the lease accounting guidance (ASC 842) and are accounted for as service contracts in which the expense is recognized on a straight-line basis over the lease team. Favorable spectrum leases of $790 million were recorded as an intangible asset as a result of purchase accounting and will be amortized on a straight-line basis over the associated remaining lease term. Additionally, we recognized unfavorable spectrum lease liabilities of $197 million, which are also amortized over their respective remaining lease terms and are included in Other liabilities in our Consolidated Balance Sheets. The customer relationship intangible assets represent the value associated with the acquired Sprint customers. The customer relationship intangible assets are amortized using the sum-of-the-years digits method over periods of up to eight years. Other intangible assets are amortized over the remaining period that the asset is expected to provide benefit to us. Spectrum Licenses The following table summarizes our spectrum license activity for the years ended December 31, 2020 and 2019: (in millions) 2020 2019 Spectrum licenses, beginning of year $ 36,465 $ 35,559 Spectrum license acquisitions 1,023 857 Spectrum licenses acquired in Merger 45,400 — Spectrum licenses transferred to held for sale (83) — Costs to clear spectrum 23 49 Spectrum licenses, end of year $ 82,828 $ 36,465 Spectrum Transactions In March 2020, the FCC announced that we were the winning bidder of 2,384 licenses in Auction 103 (37/39 GHz and 47 GHz spectrum bands) for an aggregate price of $873 million, net of an incentive payment of $59 million. At the inception of Auction 103 in October 2019, we deposited $82 million with the FCC. Upon conclusion of Auction 103 in March 2020, we made a down payment of $93 million for the purchase price of the licenses won in the auction. On April 8, 2020, we paid the FCC the remaining $698 million of the purchase price for the licenses won in the auction. Prior to the Merger, the FCC announced that Sprint was the winning bidder of 127 licenses in Auction 103 (37/39 GHz and 47 GHz spectrum bands). All payments related to the licenses won were made by Sprint prior to the Merger. In November 2020, we executed an agreement with a third party for the exchange of certain AWS spectrum licenses. Upon the execution of the agreement, the spectrum licenses were classified as assets held for sale, included within Other current assets, and measured at the lower of their carrying amount or fair value less cost to sell, which resulted in the recognition of a non-cash impairment loss of $35 million, included in Selling, general and administrative expenses in our Consolidated Statements of Comprehensive Income. We received approval for the transaction from the FCC and the transaction closed in the first quarter of 2021. The licenses are included in Spectrum licenses in our Consolidated Balance Sheets as of December 31, 2020. Cash payments to acquire spectrum licenses and payments for costs to clear spectrum are included in Purchases of spectrum licenses and other intangible assets, including deposits, in our Consolidated Statements of Cash Flows for the year ended December 31, 2020. In April 2020, we acquired FCC licenses in the 800 MHz, 1900 MHz, and 2.5 GHz bands as part of the Merger with Sprint at an estimated fair value of approximately $45.4 billion. See Note 2 - Business Combination for further information. Impairment assessment For our assessment of Spectrum license impairment, we employed a qualitative approach. No events or change in circumstances have occurred that indicate the fair value of the Spectrum licenses may be below its carrying amount at December 31, 2020. Other Intangible Assets The components of Other intangible assets were as follows: Useful Lives December 31, 2020 December 31, 2019 (in millions) Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Customer relationships Up to 8 years $ 4,900 $ (865) $ 4,035 $ 1,104 $ (1,104) $ — Tradenames and patents Up to 19 years 598 (412) 186 323 (258) 65 Favorable spectrum leases Up to 27 years 790 (35) 755 — — — Other Up to 10 years 377 (55) 322 100 (50) 50 Other intangible assets $ 6,665 $ (1,367) $ 5,298 $ 1,527 $ (1,412) $ 115 Amortization expense for intangible assets subject to amortization was $1.2 billion, $82 million and $124 million for the years ended December 31, 2020, 2019 and 2018, respectively. The estimated aggregate future amortization expense for intangible assets subject to amortization are summarized below: (in millions) Estimated Future Amortization Twelve Months Ending December 31, 2021 $ 1,246 2022 982 2023 827 2024 669 2025 511 Thereafter 1,063 Total $ 5,298 Substantially all of the estimated future amortization expense is associated with intangible assets acquired in the Merger.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 7 – Fair Value Measurements The carrying values of Cash and cash equivalents, Accounts receivable, Accounts receivable from affiliates, Accounts payable and accrued liabilities and borrowings under vendor financing arrangements with our primary network equipment suppliers approximate fair value due to the short-term maturities of these instruments. Derivative Financial Instruments Periodically, we use derivatives to manage exposure to market risk, such as interest rate risk. We designate certain derivatives as hedging instruments in a qualifying hedge accounting relationship (cash flow hedge) to help minimize significant, unplanned fluctuations in cash flows caused by interest rate volatility. We do not use derivatives for trading or speculative purposes. Interest Rate Lock Derivatives In October 2018, we entered into interest rate lock derivatives with notional amounts of $9.6 billion. In November 2019, we extended the mandatory termination date on our interest rate lock derivatives to June 3, 2020. For the three months ended March 31, 2020, we made net collateral transfers to certain of our derivative counterparties totaling $580 million, which included variation margin transfers to (or from) such derivative counterparties based on daily market movements. No amounts were transferred to the derivative counterparties subsequent to March 31, 2020. These collateral transfers are included in Net cash related to derivative contracts under collateral exchange arrangements within Net cash used in investing activities in our Consolidated Statements of Cash Flows. The net collateral transfers to certain of our derivative counterparties totaled $632 million for the three months ended December 31, 2019, and was presented in Other current assets in our Consolidated Balance Sheets. There was no collateral receivable balance as of December 31, 2020. We record interest rate lock derivatives on our Consolidated Balance Sheets at fair value that is derived primarily from observable market data, including yield curves. Interest rate lock derivatives were classified as Level 2 in the fair value hierarchy. Cash flows associated with qualifying hedge derivative instruments are presented in the same category on the Consolidated Statements of Cash Flows as the item being hedged. The fair value of interest rate lock derivatives was a liability of $1.2 billion as of December 31, 2019, and was included in Other current liabilities in our Consolidated Balance Sheets. Aggregate changes in fair value, net of tax, of $1.6 billion and $868 million are presented in Accumulated other comprehensive loss as of December 31, 2020 and 2019, respectively. Between April 2 to April 6, 2020, in connection with the issuance of an aggregate of $19.0 billion in Senior Secured Notes bearing interest rates ranging from 3.500% to 4.500% and maturing in 2025 through 2050, we terminated our interest rate lock derivatives. See Note 8 - Debt for further information regarding the issuance of Senior Secured Notes. At the time of termination, the interest rate lock derivatives were a liability of $2.3 billion, of which $1.2 billion was cash-collateralized. The cash flows associated with the settlement of interest rate lock derivatives are presented on a gross basis in our Consolidated Statements of Cash Flows, with the total cash payments to settle the swaps of $2.3 billion presented in changes in Other current and long-term liabilities within Net cash provided by operating activities and the return of cash collateral of $1.2 billion presented as an inflow in Net cash related to derivative contracts under collateral exchange arrangements within Net cash used in investing activities. Upon the issuance of debt to which the hedged interest rate risk related, we began amortizing the Accumulated other comprehensive loss with the derivatives into Interest expense in a manner consistent with how the hedged interest payments affect earnings. For the year ended December 31, 2020, $128 million was amortized from Accumulated other comprehensive loss into Interest expense in the Consolidated Statements of Comprehensive Income. No amounts were amortized into Interest expense for the years ended December 31, 2019 and 2018. We expect to amortize $189 million of the Accumulated other comprehensive loss associated with the derivatives into Interest expense over the next 12 months. Deferred Purchase Price Assets In connection with the sales of certain service and EIP accounts receivable pursuant to the sale arrangements, we have deferred purchase price assets measured at fair value that are based on a discounted cash flow model using unobservable Level 3 inputs, including customer default rates. See Note 4 – Sales of Certain Receivables for further information. The carrying amounts of our deferred purchase price assets, which are measured at fair value on a recurring basis and are included in our Consolidated Balance Sheets, were $884 million and $781 million at December 31, 2020 and 2019, respectively. Fair value was equal to carrying amount at December 31, 2020 and 2019. Debt The fair value of our Senior Unsecured Notes, Senior Secured Notes, and Secured Term Loan Facility to third parties was determined based on quoted market prices in active markets, and therefore were classified as Level 1 within the fair value hierarchy. The fair values of our Senior Notes to affiliates and Incremental Term Loan Facility to affiliates were determined based on a discounted cash flow approach using market interest rates of instruments with similar terms and maturities and an estimate for our standalone credit risk. Accordingly, our Senior Notes to affiliates and Incremental Term Loan Facility to affiliates were classified as Level 2 within the fair value hierarchy. Although we have determined the estimated fair values using available market information and commonly accepted valuation methodologies, considerable judgment was required in interpreting market data to develop fair value estimates for the Senior Notes to affiliates and Incremental Term Loan Facility to affiliates. The fair value estimates were based on information available as of December 31, 2020 and 2019. As such, our estimates are not necessarily indicative of the amount we could realize in a current market exchange. The carrying amounts and fair values of our short-term and long-term debt included in our Consolidated Balance Sheets were as follows: Level within the Fair Value Hierarchy December 31, 2020 December 31, 2019 (in millions) Carrying Amount (1) Fair Value (1) Carrying Amount (1) Fair Value (1) Liabilities: Senior Unsecured Notes to third parties 1 $ 29,966 $ 32,450 $ 10,958 $ 11,479 Senior Notes to affiliates 2 4,716 4,991 9,986 10,366 Senior Secured Notes to third parties 1 36,204 40,519 — — Incremental Term Loan Facility to affiliates 2 — — 4,000 4,000 (1) Excludes $240 million and $25 million as of December 31, 2020 and 2019, respectively, in vendor financing arrangements and other debt as the carrying values approximate fair value primarily due to the short-term maturities of these instruments. Guarantee Liabilities We offer device trade-in programs that provide eligible customers a specified-price trade-in right to upgrade their device. For customers who enroll in these programs, we recognize a liability and reduce revenue for the portion of revenue which represents the estimated fair value of the specified-price trade-in right guarantee, incorporating the expected probability and timing of handset upgrade and the estimated fair value of the handset which is returned. Accordingly, our guarantee liabilities were classified as Level 3 within the fair value hierarchy. When customers upgrade their devices, the difference between the EIP balance credit to the customer and the fair value of the returned device is recorded against the guarantee liabilities. Guarantee liabilities are included in Other current liabilities in our Consolidated Balance Sheets. The carrying amounts of our guarantee liabilities measured at fair value on a non-recurring basis included in our Consolidated Balance Sheets were $50 million and $62 million as of December 31, 2020 and 2019, respectively. The total estimated remaining gross EIP receivable balances of all enrolled handset upgrade program customers, which are the remaining EIP amounts underlying the trade-in right guarantee, including EIP receivables that have been sold, was $3.4 billion as of December 31, 2020. This is not an indication of our expected loss exposure as it does not consider the expected fair value of the used handset or the probability and timing of the trade-in.

Debt

Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt	Note 8 – Debt Debt was as follows: (in millions) December 31, December 31, 3.360% Series 2016-1 A-1 Notes due 2021 $ 656 $ — 5.300% Senior Notes to affiliates due 2021 — 2,000 7.250% Senior Notes due 2021 2,250 — 11.500% Senior Notes due 2021 1,000 — 4.000% Senior Notes to affiliates due 2022 1,000 1,000 4.000% Senior Notes due 2022 500 500 6.000% Senior Notes due 2022 2,280 — Incremental term loan facility to affiliates due 2022 — 2,000 6.000% Senior Notes due 2023 1,300 1,300 7.875% Senior Notes due 2023 4,250 — 6.000% Senior Notes due 2024 1,000 1,000 6.000% Senior Notes to affiliates due 2024 — 1,350 6.000% Senior Notes to affiliates due 2024 — 650 6.500% Senior Notes due 2024 — 1,000 7.125% Senior Notes due 2024 2,500 — Incremental term loan facility to affiliates due 2024 — 2,000 3.500% Senior Secured Notes due 2025 3,000 — 4.738% Series 2018-1 A-1 Notes due 2025 2,100 — 5.125% Senior Notes to affiliates due 2025 (1) — 1,250 5.125% Senior Notes due 2025 500 500 6.375% Senior Notes due 2025 — 1,700 7.625% Senior Notes due 2025 1,500 — 1.500% Senior Secured Notes due 2026 1,000 — 6.500% Senior Notes due 2026 2,000 2,000 4.500% Senior Notes due 2026 1,000 1,000 4.500% Senior Notes to affiliates due 2026 1,000 1,000 7.625% Senior Notes due 2026 1,500 — 3.750% Senior Secured Notes due 2027 4,000 — 5.375% Senior Notes due 2027 500 500 5.375% Senior Notes to affiliates due 2027 (1) 1,250 1,250 2.050% Senior Secured Notes due 2028 1,750 — 4.750% Senior Notes due 2028 1,500 1,500 4.750% Senior Notes to affiliates due 2028 1,500 1,500 5.152% Series 2018-1 A-2 Notes due 2028 1,838 — 6.875% Senior Notes due 2028 2,475 — 3.875% Senior Secured Notes due 2030 7,000 — 2.250% Senior Secured Notes due 2031 1,000 — 2.550% Senior Secured Notes due 2031 2,500 — 8.750% Senior Notes due 2032 2,000 — 4.375% Senior Secured Notes due 2040 2,000 — 3.000% Senior Secured Notes due 2041 2,500 — 4.500% Senior Secured Notes due 2050 3,000 — 3.300% Senior Secured Notes due 2051 3,000 — 3.600% Senior Secured Notes due 2060 1,000 — Other debt 240 25 Unamortized premium on debt to affiliates — 43 Unamortized premium on debt to third parties 2,197 — Unamortized discount on debt to affiliates (20) (53) Unamortized discount on debt to third parties (197) — Debt issuance costs and consent fees (244) (46) Total debt 71,125 24,969 Less: Current portion of Senior Notes and other debt to third parties 4,579 25 Total long-term debt $ 66,546 $ 24,944 Classified on the balance sheet as: Long-term debt $ 61,830 $ 10,958 Long-term debt to affiliates 4,716 13,986 Total long-term debt $ 66,546 $ 24,944 (1) On April 1, 2020, in connection with the closing of the Merger, we amended the $1.25 billion of 5.125% Senior Notes to affiliates due 2025 and $1.25 billion of 5.375% Senior Notes to affiliates due 2027, to change the maturity date thereof to April 15, 2021 and April 15, 2022, respectively. See “Financing Matters Agreement” section below for further information. Our effective interest rate, excluding the impact of derivatives and capitalized interest, was approximately 4.6% and 5.2% for the years ended December 31, 2020 and 2019, respectively, on weighted average debt outstanding of $58.4 billion and $25.5 billion for the years ended December 31, 2020 and 2019, respectively. The weighted average debt outstanding was calculated by applying an average of the monthly ending balances of total short-term and long-term debt and short-term and long-term debt to affiliates, net of unamortized premiums, discounts, debt issuance costs and consent fees. Issuances and Borrowings During the year ended December 31, 2020, we issued the following Senior Secured Notes and entered into the following Secured loan facilities: (in millions) Principal Issuances Premiums, Discounts and Issuance Costs Net Proceeds from Issuance of Long-Term Debt Issue Date 3.500% Senior Secured Notes due 2025 $ 3,000 $ 12 $ 2,988 April 9, 2020 3.750% Senior Secured Notes due 2027 4,000 17 3,983 April 9, 2020 3.875% Senior Secured Notes due 2030 7,000 78 6,922 April 9, 2020 4.375% Senior Secured Notes due 2040 2,000 47 1,953 April 9, 2020 4.500% Senior Secured Notes due 2050 3,000 24 2,976 April 9, 2020 1.500% Senior Secured Notes due 2026 1,000 5 995 June 24, 2020 2.050% Senior Secured Notes due 2028 1,250 8 1,242 June 24, 2020 2.550% Senior Secured Notes due 2031 1,750 12 1,738 June 24, 2020 2.050% Senior Secured Notes due 2028 500 (11) 511 October 6, 2020 2.550% Senior Secured Notes due 2031 750 (29) 779 October 6, 2020 3.000% Senior Secured Notes due 2041 1,250 15 1,235 October 6, 2020 3.300% Senior Secured Notes due 2051 1,500 16 1,484 October 6, 2020 2.250% Senior Secured Notes due 2031 1,000 5 995 October 28, 2020 3.000% Senior Secured Notes due 2041 1,250 38 1,212 October 28, 2020 3.300% Senior Secured Notes due 2051 1,500 58 1,442 October 28, 2020 3.600% Senior Secured Notes due 2060 1,000 11 989 October 28, 2020 Total of Senior Secured Notes issued 31,750 306 31,444 Secured bridge loan facility due 2021 19,000 257 18,743 April 1, 2020 Secured term loan facility due 2027 4,000 107 3,893 April 1, 2020 Total of Secured loan facilities issued 23,000 364 22,636 Total Issuances and Borrowings $ 54,750 $ 670 $ 54,080 Credit Facilities In connection with the entry into the Business Combination Agreement, T-Mobile USA entered into the Commitment Letter, with certain financial institutions named therein that committed to provide up to $27.0 billion in secured debt financing through May 1, 2020, including a $4.0 billion secured revolving credit facility, a $4.0 billion secured term loan facility, and a $19.0 billion secured bridge loan facility. The funding of the debt facilities provided for in the Commitment Letter was subject to the satisfaction of the conditions set forth therein, including consummation of the Merger. On April 1, 2020, in connection with the closing of the Merger, T-Mobile USA and certain of its affiliates, as guarantors, entered into a Bridge Loan Credit Agreement with certain financial institutions named therein, providing for a $19.0 billion secured bridge loan facility (“New Secured Bridge Loan Facility”). The New Secured Bridge Loan Facility had an interest rate equal to a per annum rate of LIBOR plus a margin of 1.25% and had a maturity date of March 31, 2021. On April 1, 2020, in connection with the closing of the Merger, T-Mobile USA and certain of its affiliates, as guarantors, entered into a Credit Agreement (the “New Credit Agreement”) with certain financial institutions named therein, providing for a $4.0 billion secured term loan facility (“New Secured Term Loan Facility”) and a $4.0 billion revolving credit facility (“New Revolving Credit Facility”). On September 16, 2020, we increased the aggregate commitment under the New Revolving Credit Facility to $5.5 billion through an amendment (the “Incremental Amendment”) to the New Credit Agreement. The New Secured Term Loan Facility had an interest rate equal to a per annum rate of LIBOR plus a margin of 3.00% and had a maturity date of April 1, 2027. The New Revolving Credit Facility bears interest at a rate equal to a per annum rate of LIBOR plus a margin of 1.25% with the margin subject to a reduction to 1.00% if T-Mobile’s Total First Lien Net Leverage Ratio (as defined in the New Credit Agreement) is less than or equal to 0.75 to 1.00. The commitments under the New Revolving Credit Facility mature on April 1, 2025. The New Credit Agreement contains customary representations, warranties and covenants, including a financial maintenance covenant of 3.3x with respect to T-Mobile’s Total First Lien Net Leverage Ratio commencing with the period ending September 30, 2020. On April 1, 2020, in connection with the closing of the Merger, we drew down on our $19.0 billion New Secured Bridge Loan Facility and our $4.0 billion New Secured Term Loan Facility. We used the net proceeds of $22.6 billion from the drawdown of the secured facilities to repay our $4.0 billion Incremental Term Loan Facility with DT and to repurchase from DT $4.0 billion of indebtedness to affiliates, consisting of $2.0 billion of 5.300% Senior Notes due 2021 and $2.0 billion of 6.000% Senior Notes due 2024, as well as to redeem certain debt of Sprint and Sprint’s subsidiaries, including the secured term loans due 2024 with a total principal amount outstanding of $5.9 billion, accounts receivable facility with a total amount outstanding of $2.3 billion, and Sprint’s 7.250% Guaranteed Notes due 2028 with a total principal amount outstanding of $1.0 billion, and for post-closing general corporate purposes of the combined company. In connection with the financing provided for in the Commitment Letter, we incurred certain fees payable to the financial institutions, including certain financing fees on the secured term loan commitment and fees for structuring, funding, and providing the commitments. On April 1, 2020, in connection with the closing of the Merger, we paid $355 million in Commitment Letter fees to certain financial institutions. On October 30, 2020, we entered into a $5.0 billion senior secured term loan commitment with certain financial institutions. Subsequent to December 31, 2020, on January 14, 2021, we issued an aggregate of $3.0 billion in Senior Notes. A portion of the senior secured term loan commitment was reduced by an amount equal to the aggregate gross proceeds of the Senior Notes, which reduced the commitment to $2.0 billion. Up to $2.0 billion of loans under the commitment may be drawn at any time (subject to customary conditions precedent) through June 30, 2021. If drawn, the facility matures in 364 days with one six Senior Notes On April 9, 2020, T-Mobile USA and certain of its affiliates, as guarantors, issued an aggregate of $19.0 billion in Senior Secured Notes bearing interest rates ranging from 3.500% to 4.500% and maturing in 2025 through 2050, and used the net proceeds of $18.8 billion together with cash on hand to repay all of the outstanding amounts under, and terminate, our $19.0 billion New Secured Bridge Loan Facility, as described above. On June 24, 2020, T-Mobile USA and certain of its affiliates, as guarantors, issued an aggregate of $4.0 billion in Senior Secured Notes bearing interest rates ranging from 1.500% to 2.550% and maturing in 2026 through 2031. The Senior Secured Notes were issued for refinancing callable Senior Notes and, subsequent to the issuance, we redeemed certain Senior Notes as set forth below under “Senior Secured Notes – Redemptions and Repayments” and “Senior Notes to Affiliates.” On October 6, 2020, T-Mobile USA and certain of its affiliates, as guarantors, issued an aggregate of $4.0 billion in Senior Secured Notes bearing interest rates ranging from 2.050% to 3.300% and maturing in 2028 through 2051. On October 9, 2020, we used the net proceeds of $4.0 billion to repay at par all of the outstanding amounts under, and terminate, our New Secured Term Loan Facility. On October 28, 2020, T-Mobile USA and certain of its affiliates, as guarantors, issued an aggregate of $4.75 billion in Senior Secured Notes bearing interest rates ranging from 2.250% to 3.600% and maturing in 2031 through 2060. We intend to use the net proceeds of $4.6 billion for general corporate purposes, which may include among other things, acquisitions of additional spectrum and refinancing existing indebtedness on an ongoing basis. The Senior Secured Notes have not been registered under the Securities Act of 1933, as amended (the “Securities Act”), and may not be offered or sold in the United States or to, or for the account or benefit of, U.S. persons except in accordance with an applicable exemption from the registration requirements thereof. Accordingly, the Senior Secured Notes were offered and sold only (1) to persons reasonably believed to be “qualified institutional buyers” under Rule 144A under the Securities Act and (2) outside the United States to non-U.S. persons in reliance upon Regulation S under the Securities Act. The Senior Secured Notes are secured by a first priority security interest, subject to permitted liens, in substantially all of our present and future assets, other than certain excluded assets. They are redeemable at our discretion, in whole or in part, at any time. If redeemed prior to their contractually specified Par Call Date, the redemption price is subject to a make-whole premium calculated by reference to then-current U.S. Treasury rates plus a fixed spread; if redeemed on or after their respective Par Call Date, the make-whole premium does not apply. The amount of time by which the Par Call Date precedes the maturity date of the respective note varies from one We have entered into a Registration Rights Agreement that is in effect through the maturity of the applicable Senior Secured Notes. This agreement calls for us to use commercially reasonable efforts to file a registration statement and have it declared effective within a particular time period and to maintain the effectiveness of the registration statement for a certain period of time. If a default occurs, we will pay additional interest up to a maximum increase of 0.50% per annum. We have not accrued any obligations associated with the Registration Rights Agreement as compliance with the agreements is considered probable. Subsequent to December 31, 2020, on January 14, 2021, T-Mobile USA issued $1.0 billion of 2.250% Senior Notes due 2026, $1.0 billion of 2.625% Senior Notes due 2029, and $1.0 billion of 2.875% Senior Notes due 2031. We intend to use the net proceeds of $3.0 billion for general corporate purposes, which may include among other things, financing acquisitions of additional spectrum and refinancing existing indebtedness on an ongoing basis. Debt Assumed In connection with the Merger, we assumed the following indebtedness of Sprint: (in millions) Fair value as of April 1, 2020 Principal Outstanding as of December 31, 2020 Carrying Value as of December 31, 2020 7.250% Senior Notes due 2021 $ 2,324 $ 2,250 $ 2,287 7.875% Senior Notes due 2023 4,682 4,250 4,594 7.125% Senior Notes due 2024 2,746 2,500 2,706 7.625% Senior Notes due 2025 1,677 1,500 1,652 7.625% Senior Notes due 2026 1,701 1,500 1,679 3.360% Senior Secured Series 2016-1 A-1 Notes due 2021 (1) 1,310 656 656 4.738% Senior Secured Series 2018-1 A-1 Notes due 2025 (1) 2,153 2,100 2,145 5.152% Senior Secured Series 2018-1 A-2 Notes due 2028 (1) 1,960 1,838 1,950 7.000% Senior Notes due 2020 1,510 — — 11.500% Senior Notes due 2021 1,105 1,000 1,057 6.000% Senior Notes due 2022 2,372 2,280 2,346 6.875% Senior Notes due 2028 2,834 2,475 2,808 8.750% Senior Notes due 2032 2,649 2,000 2,620 Accounts receivable facility 2,310 — — Other debt 464 256 240 Total Debt Assumed $ 31,797 $ 24,605 $ 26,740 (1) In connection with the closing of the Merger, we assumed Sprint’s spectrum-backed notes, which are collateralized by the acquired directly held and third-party leased Spectrum licenses. See “Spectrum Financing” section below for further information. Redemptions and Repayments During the year ended December 31, 2020, we repaid the following loan facilities and redeemed the following Senior Notes held by third parties and Senior Notes held by affiliates: (in millions) Principal Amount Write-off of Premiums, Discounts and Issuance Costs (1) Other (2) Redemption or Repayment Date Redemption Price 6.500% Senior Notes due 2024 $ 1,000 $ 12 $ 22 July 4, 2020 102.167 % 7.000% Senior Notes due 2020 1,500 — — August 15, 2020 N/A 6.375% Senior Notes due 2025 1,700 24 36 September 1, 2020 102.125 % Total Senior Notes to third parties redeemed 4,200 36 58 5.300% Senior Notes to affiliates due 2021 (3) 2,000 — — April 1, 2020 100.000 % 6.000% Senior Notes to affiliates due 2024 (3) 1,350 (26) — April 1, 2020 100.000 % 6.000% Senior Notes to affiliates due 2024 (3) 650 (15) — April 1, 2020 100.000 % 5.125% Senior Secured Notes to affiliates due 2025 1,250 15 — July 4, 2020 100.000 % Total Senior Notes to affiliates redeemed 5,250 (26) — Total Redemptions $ 9,450 $ 10 $ 58 Incremental term loan facility to affiliates due 2022 $ 2,000 $ — $ — April 1, 2020 100.000 % Incremental term loan facility to affiliates due 2024 2,000 — — April 1, 2020 100.000 % Accounts receivable facility 2,310 — — April 1, 2020 100.000 % Secured bridge loan facility due 2021 19,000 251 (47) April 9, 2020 100.128 % 3.360% Senior Secured Series 2016-1 A-1 Notes due 2021 656 — — Various N/A Secured term loan facility due 2027 4,000 100 — October 9, 2020 100.000 % Other debt 481 — — Various N/A Total Repayments $ 30,447 $ 351 $ (47) (1) Write-off of premiums, discounts and issuance costs are included in Other expense, net in our Consolidated Statements of Comprehensive Income. Write-off of issuance costs are included in Loss on redemption of debt within Net cash provided by operating activities in our Consolidated Statements of Cash Flows. (2) Primarily represents a reimbursement of a portion of the commitment letter fees that were paid to financial institutions when we drew down on the Secured Bridge Loan Facility on April 1, 2020 and is included in Other expense, net in our Consolidated Statements of Comprehensive Income. (3) Pursuant to the Financing Matters Agreement, the Senior Notes were effectively redeemed through a repurchase and were cancelled and retired in full on April 1, 2020. On April 9, 2020, we repaid all of the outstanding amounts under, and terminated, our $19.0 billion New Secured Bridge Loan Facility. Additionally, in connection with the repayment of our New Secured Bridge Loan Facility, we received a reimbursement of $71 million, which represents a portion of the Commitment Letter fees that were paid to certain financial institutions when we drew down on the New Secured Bridge Loan Facility on April 1, 2020. The reimbursement is presented in Other expense, net in our Consolidated Statements of Comprehensive Income. On July 4, 2020, we redeemed $1.0 billion aggregate principal amount of our 6.500% Senior Notes due 2024. The notes were redeemed at a redemption price equal to 102.167% of the principal amount of the notes (plus accrued and unpaid interest thereon), and were paid on July 6, 2020. The redemption premium was approximately $22 million and the write off of issuance costs and consent fees was approximately $12 million, which were included in Other expense, net in our Consolidated Statements of Comprehensive Income and Losses on redemption of debt in our Consolidated Statements of Cash Flows. On July 4, 2020, we also redeemed $1.25 billion aggregate principal amount of our 5.125% Senior Notes to affiliates due 2021, as further described below under “Senior Notes to Affiliates.” On August 15, 2020, we redeemed at maturity $1.5 billion aggregate principal amount of our 7.000% Senior Notes due 2020 (plus accrued and unpaid interest thereon). On September 1, 2020, we redeemed $1.7 billion aggregate principal amount of our 6.375% Senior Notes due 2025. The notes were redeemed at a redemption price equal to 102.125% of the principal amount of the notes (plus accrued and unpaid interest thereon), and were paid on September 1, 2020. The redemption premium was approximately $36 million and the write off of issuance costs and consent fees was approximately $24 million, which were included in Other expense, net in our Consolidated Statements of Comprehensive Income. On October 9, 2020, we repaid at par all of the outstanding amounts under, and terminated, our New Secured Term Loan Facility. The write off of discounts and issuance costs was approximately $100 million, which were included in Other expense, net in our Consolidated Statements of Comprehensive Income. Financing Matters Agreement Pursuant to the Financing Matters Agreement, DT agreed, among other things, to consent to the incurrence by T-Mobile USA of secured debt in connection with and after the consummation of the Merger, and to provide a lock up on sales thereby as to certain Senior Notes of T-Mobile USA held thereby. In connection with receiving the requisite consents, we made upfront payments to DT of $7 million during the second quarter of 2018. These payments were recognized as a reduction to Long-term debt to affiliates in our Consolidated Balance Sheets. On April 1, 2020, in connection with the closing of the Merger, we: • Repaid our $4.0 billion Incremental Term Loan Facility with DT, consisting of a $2.0 billion Incremental Term Loan Facility due 2022 and a $2.0 billion Incremental Term Loan Facility due 2024; • Terminated our revolving credit facility; • Repurchased from DT $4.0 billion of indebtedness to affiliates, consisting of $2.0 billion of 5.300% Senior Notes due 2021 and $2.0 billion of 6.000% Senior Notes due 2024; • Amended the $1.25 billion of 5.125% Senior Notes due 2025 and $1.25 billion of 5.375% Senior Notes due 2027, which represent indebtedness to affiliates, to change the maturity dates thereof to April 15, 2021 and April 15, 2022, respectively (the “2025 and 2027 Amendments”); and • Made an additional payment for requisite consents to DT of $13 million. These payments were recognized as a reduction to Long-term debt to affiliates in our Consolidated Balance Sheets. In accordance with the consents received from DT, on December 20, 2018, T-Mobile USA, the guarantors and Deutsche Bank Trust Company Americas, as trustee, executed and delivered the 38 th supplemental indenture to the Indenture, pursuant to which, with respect to certain T-Mobile USA Senior Notes held by DT, the Debt Amendments (as defined below under “Consents on Debt to Third Parties”) and the 2025 and 2027 Amendments became effective immediately prior to the consummation of the Merger. Senior Notes to Affiliates On July 4, 2020, we redeemed $1.25 billion aggregate principal amount of our 5.125% Senior Notes to affiliates due 2021. The notes were redeemed at a redemption price equal to 100.00% of the principal amount of the notes (plus accrued and unpaid interest thereon), and were paid on July 6, 2020. The write off of discounts was approximately $15 million and was included in Other expense, net in our Consolidated Statements of Comprehensive Income and Losses on redemption of debt in our Consolidated Statements of Cash Flows. Consents on Debt to Third Parties On May 18, 2018, under the terms and conditions described in the Consent Solicitation Statement, we obtained consents necessary to effect certain amendments to our Senior Notes to third parties in connection with the Business Combination Agreement. Pursuant to the Consent Solicitation Statement, third-party note holders agreed, among other things, to consent to increasing the amount of Secured Indebtedness under credit facilities that can be incurred from the greater of $9.0 billion and 150% of Consolidated Cash Flow to the greater of $9.0 billion and an amount that would not cause the Secured Debt to Cash Flow Ratio (calculated net of cash and cash equivalents) to exceed 2.00x (the “Ratio Secured Debt Amendments”) and in each case as such capitalized term is defined in the Indenture. In connection with receiving the requisite consents for the Ratio Secured Debt Amendments, we made upfront payments to third-party note holders of $17 million during the second quarter of 2018. These payments were recognized as a reduction to Long-term debt in our Consolidated Balance Sheets. These upfront payments increased the effective interest rate of the related debt. In addition, note holders agreed, among other things, to allow certain entities related to Sprint’s existing spectrum securitization notes program (“Existing Sprint Spectrum Program”) to be non-guarantor Restricted Subsidiaries, provided that the principal amount of the spectrum notes issued and outstanding under the Existing Sprint Spectrum Program does not exceed $7.0 billion and that the principal amount of such spectrum notes reduces the amount available under the credit facilities ratio basket, and to revise the definition of GAAP to mean generally accepted accounting principles in effect from time to time, unless the Company elects to “freeze” GAAP as of any date, and to exclude the effect of the changes in the accounting treatment of lease obligations (the “Existing Sprint Spectrum and GAAP Amendments,” and together with the Ratio Secured Debt Amendments, the “Debt Amendments”). In connection with receiving the requisite consents for the Existing Sprint Spectrum and GAAP Amendments, we made upfront payments to third-party note holders of $14 million during the second quarter of 2018. These payments were recognized as a reduction to Long-term debt in our Consolidated Balance Sheets. These upfront payments increased the effective interest rate of the related debt. In connection with obtaining the requisite consents, on May 20, 2018, T-Mobile USA, the guarantors and Deutsche Bank Trust Company Americas, as trustee, executed and delivered the 37 th supplemental indenture to the Indenture, pursuant to which, with respect to each of our Senior Notes to third parties, all the amendments mentioned above (collectively, the “Debt Amendments”) would become effective immediately prior to the consummation of the Merger. We paid third-party bank fees associated with obtaining the requisite consents related to the Debt Amendments of $6 million during the second quarter of 2018, which we recognized as Selling, general and administrative expenses in our Consolidated Statements of Comprehensive Income. On April 1, 2020, in connection with the closing of the Merger, we made additional payments to third-party note holders for requisite consents related to the Ratio Secured Debt Amendments of $54 million and related to the Existing Sprint Spectrum and GAAP Amendments of $41 million. These payments were recognized as a reduction to Long-term debt in our Consolidated Balance Sheets. These payments increased the effective interest rate of the related debt. Spectrum Financing On April 1, 2020, in connection with the closing of the Merger, we assumed Sprint’s spectrum-backed notes, which are collateralized by the acquired directly held and third-party leased Spectrum licenses (collectively, the “Spectrum Portfolio“) transferred to wholly owned bankruptcy-remote special purpose entities (collectively, the “Spectrum Financing SPEs”). As of December 31, 2020, the total outstanding obligations under these Notes was $4.6 billion. In October 2016, certain subsidiaries of Sprint Communications, Inc. transferred the Spectrum Portfolio to the Spectrum Financing SPEs, which was used as collateral to raise an initial $3.5 billion in senior secured notes (the “2016 Spectrum-Backed Notes”) bearing interest at 3.360% per annum under a $7.0 billion securitization program. The 2016 Spectrum-Backed Notes are repayable over a five-year term, with interest-only payments over the first four quarters and amortizing quarterly principal payments thereafter commencing December 2017 through September 2021. During the year ended December 31, 2020, we made scheduled principal repayments of $656 million, resulting in a total principal amount outstanding related to the 2016 Spectrum-Backed Notes of $656 million as of December 31, 2020, which was classified as Short-term debt in the Consolidated Balance Sheets . In March 2018, Sprint issued approximately $3.9 billion in aggregate principal amount of senior secured notes (the “2018 Spectrum-Backed Notes” and together with the 2016 Spectrum-Backed Notes, the “Spectrum-Backed Notes”) under the existing $7.0 billion securitization program, consisting of two series of senior secured notes. The first series of notes totaled $2.1 billion in aggregate principal amount, bears interest at 4.738% per annum, and has quarterly interest-only payments until June 2021, and amortizing quarterly principal amounts thereafter commencing in June 2021 through March 2025. As of December 31, 2020, $394 million of the aggregate principal amount was classified as Short-term debt in the Consolidated Balance Sheets. The second series of notes totaled approximately $1.8 billion in aggregate principal amount, bears interest at 5.152% per annum, and has quarterly interest-only payments until June 2023, and amortizing quarterly principal amounts thereafter commencing in June 2023 through March 2028. The Spectrum Portfolio, which also serves as collateral for the Spectrum-Backed Notes, remains substantially identical to the original portfolio from October 2016. Simultaneously with the October 2016 offering, Sprint Communications, Inc. entered a long-term lease with the Spectrum Financing SPEs for the ongoing use of the Spectrum Portfolio. Sprint Communications, Inc. is required to make monthly lease payments to the Spectrum Financing SPEs in an aggregate amount that is market-based relative to the spectrum usage rights as of the closing date and equal to $165 million per month. The lease payments, which are guaranteed by T-Mobile subsidiaries, are sufficient to service all outstanding series of the 2016 Spectrum Backed Notes and the lease also constitutes collateral for the senior secured notes. Because the Spectrum Financing SPEs are wholly owned T-Mobile subsidiaries, these entities are consolidated and all intercompany activity has been eliminated. Each Spectrum Financing SPE is a separate legal entity with its own separate creditors who will be entitled, prior to and upon the liquidation of the respective Spectrum Financing SPE, to be satisfied out of the Spectrum Financing SPE’s assets prior to any assets of such Spectrum Financing SPE becoming available to T-Mobile. Accordingly, the assets of each Spectrum Financing SPE are not available to satisfy the debts and other obligations owed to other creditors of T-Mobile until the obligations of such Spectrum Financing SPE under the spectrum-backed senior secured notes are paid in full. Certain provisions of the Spectrum Financing facility require us to maintain specified cash collateral balances. Amounts associated with these balances are considered to be restricted cash. Restricted Cash Certain provisions of our debt agreements require us to maintain specified cash collateral balances. Amounts associated with these balances are considered to be restricted cash. Standby Letters of Credit

Tower Obligations

Tower Obligations	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Tower Obligations	Note 9 – Tower Obligations Existing CCI Tower Lease Arrangements In 2012, we conveyed to Crown Castle International Corp. (“CCI”) the exclusive right to manage and operate approximately 7,100 tower sites (“CCI Lease Sites”) via a master prepaid lease with site lease terms ranging from 23 to 37 years (the “2012 Tower Transaction”). CCI has fixed-price purchase options for the CCI Lease Sites totaling approximately $2.0 billion, exercisable at the end of the lease term. We lease back a portion of the space at certain tower sites for an initial term of 10 years, followed by optional renewals at customary terms. Assets and liabilities associated with the operation of the tower sites were transferred to special purpose entities (“SPEs”). Assets included ground lease agreements or deeds for the land on which the towers are situated, the towers themselves and existing subleasing agreements with other mobile network operator tenants that lease space at the tower sites. Liabilities included the obligation to pay ground lease rentals, property taxes and other executory costs. We determined the SPEs containing the CCI Lease Sites (“Lease Site SPEs”) are VIEs as they lack sufficient equity to finance their activities. We have a variable interest in the Lease Site VIE but are not the primary beneficiary as we lack the power to direct the activities that most significantly impact the Lease Site VIE’s economic performance. These activities include managing tenants and underlying ground leases, performing repair and maintenance on the towers, the obligation to absorb expected losses and the right to receive the expected future residual returns from the purchase option to acquire the CCI Lease Sites. As we determined that we are not the primary beneficiary and do not have a controlling financial interest in the Lease Site SPEs, the Lease Site SPEs are not included in our consolidated financial statements. However, we also considered if this arrangement resulted in the sale of the CCI Lease Sites for which we would de-recognize the tower assets. By assessing whether control had transferred, we concluded that transfer of control criteria, as discussed in the revenue standard, were not met. Accordingly, we recorded this arrangement as a financing whereby we recorded debt, a financial obligation, and the CCI Lease Sites tower assets remained on our balance sheet. We recorded long-term financial obligations in the amount of the net proceeds received and recognize interest on the tower obligations at a rate of approximately 8% using the effective interest method. The tower obligations are increased by interest expense and amortized through contractual leaseback payments made by us to CCI and through net cash flows generated and retained by CCI from operation of the tower sites. Acquired CCI Tower Lease Arrangements Prior to the Merger, Sprint entered into a lease-out and leaseback arrangement with Global Signal Inc., a third party that was subsequently acquired by CCI, that conveyed to CCI the exclusive right to manage and operate approximately 6,400 tower sites (“Master Lease Sites”) via a master prepaid lease. These agreements were assumed upon the close of the Merger, at which point the remaining term of the lease-out was approximately 17 years with no renewal options. CCI has a fixed price purchase option for all (but not less than all) of the leased or subleased sites for approximately $2.3 billion, exercisable one year prior to the expiration of the agreement and ending 120 days prior to the expiration of the agreement. We lease back a portion of the space at certain tower sites for an initial term of 10 years, followed by optional renewals at customary terms. We considered if this arrangement resulted in the sale of the Master Lease Sites for which we would de-recognize the tower assets. By assessing whether control had transferred, we concluded that transfer of control criteria, as discussed in the revenue standard, were not met. Accordingly, we recorded this arrangement as a financing whereby we recorded debt, a financial obligation, and the Master Lease Sites tower assets remained on our balance sheet. As of the Merger date, we recognized Property and equipment with a fair value of $2.8 billion and tower obligations related to amounts owed to CCI under the leaseback of $1.1 billion. Additionally, we recognized $1.7 billion in Other long-term liabilities associated with contract terms that are unfavorable to current market rates, which includes unfavorable terms associated with the fixed-price purchase option in 2037. We recognize interest expense on the tower obligations at a rate of approximately 6% using the effective interest method. The tower obligations are increased by interest expense and amortized through contractual leaseback payments made by us to CCI. The tower assets are reported in Property and equipment, net in our Consolidated Balance Sheets and are depreciated to their estimated residual values over the expected useful life of the tower, which is 20 years. The following table summarizes the balances associated with both of the tower arrangements in the Consolidated Balance Sheets: (in millions) December 31, December 31, 2019 Property and equipment, net $ 2,838 $ 198 Tower obligations 3,028 2,236 Other long-term liabilities 1,712 — Future minimum payments related to the tower obligations are approximately $397 million for the year ending December 31, 2021, $716 million in total for the years ending December 31, 2022 and 2023, $598 million in total for years ending December 31, 2024 and 2025, and $624 million in total for years thereafter. We are contingently liable for future ground lease payments through the remaining term of the CCI Lease Sites and the Master Lease Sites. These contingent obligations are not included in Operating lease liabilities as any amount due is contractually owed by CCI based on the subleasing arrangement. Under the arrangement, we remain primarily liable for ground lease payments on approximately 900 sites and have included lease liabilities of $282 million in our Operating lease liabilities as of December 31, 2020.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Note 10 – Revenue from Contracts with Customers Disaggregation of Revenue We provide wireless communications services to three primary categories of customers: • Postpaid customers generally include customers who are qualified to pay after receiving wireless communications services utilizing phones, wearables, DIGITS, or other connected devices which includes tablets and SyncUP products. Our postpaid customers include customers of T-Mobile; • Prepaid customers generally include customers who pay for wireless communications services in advance. Our prepaid customers include customers of T-Mobile and Metro by T-Mobile; and • Wholesale customers include Machine-to-Machine and Mobile Virtual Network Operator customers that operate on our network but are managed by wholesale partners. Postpaid service revenues, including postpaid phone revenues and postpaid other revenues, were as follows: Year Ended December 31, (in millions) 2020 2019 2018 Postpaid service revenues Postpaid phone revenues $ 33,939 $ 21,329 $ 19,745 Postpaid other revenues 2,367 1,344 1,117 Total postpaid service revenues $ 36,306 $ 22,673 $ 20,862 We operate as a single operating segment. The balances presented within each revenue line item in our Consolidated Statements of Comprehensive Income represent categories of revenue from contracts with customers disaggregated by type of product and service. Service revenues also include revenues earned for providing value added services to customers, such as device insurance services. Revenue generated from the lease of mobile communication devices is included within Equipment revenues in our Consolidated Statements of Comprehensive Income. We provide wireline communication services to domestic and international customers. Wireline service revenues of $626 million for the year ended December 31, 2020, relate to the wireline operations acquired in the Merger and are presented in Roaming and other service revenues in our Consolidated Statements of Comprehensive Income. Equipment revenues from the lease of mobile communication devices were as follows: Year Ended December 31, (in millions) 2020 2019 2018 Equipment revenues from the lease of mobile communication devices $ 4,181 $ 599 $ 692 Contract Balances The opening and closing balances of our contract asset and contract liability balances from contracts with customers as of December 31, 2019 and December 31, 2020, were as follows: (in millions) Contract Assets Contract Liabilities Balance as of December 31, 2019 $ 63 $ 560 Balance as of December 31, 2020 278 824 Change $ 215 $ 264 Contract assets primarily represent revenue recognized for equipment sales with promotional bill credits offered to customers that are paid over time and are contingent on the customer maintaining a service contract. Through the Merger, we acquired contracts assets associated with promotional bill credits and subsidized devices with a value of $154 million as of April 1, 2020. The change in the existing and acquired contract asset balance includes customer activity related to new promotions, offset by billings on existing contracts and impairment which is recognized as bad debt expense. The current portion of our Contract assets of approximately $204 million and $50 million as of December 31, 2020 and 2019, respectively, was included in Other current assets in our Consolidated Balance Sheets. Contract liabilities are recorded when fees are collected, or we have an unconditional right to consideration (a receivable) in advance of delivery of goods or services. Through the Merger, we assumed contract liabilities with a value of $336 million as of April 1, 2020. Additional changes in contract liabilities are primarily related to the volume and rate plans of active prepaid customers. Contract liabilities are primarily included in Deferred revenue in our Consolidated Balance Sheets. Revenues for the years ended December 31, 2020 and 2019, include the following: Year Ended December 31, (in millions) 2020 2019 Amounts included in the beginning of year contract liability balance $ 545 $ 643 Remaining Performance Obligations As of December 31, 2020, the aggregate amount of transaction price allocated to remaining service performance obligations for postpaid contracts with subsidized devices and promotional bill credits that result in an extended service contract is $1.5 billion. We expect to recognize revenue as service is provided on these postpaid contracts over an extended contract term of 24 months. Transaction price allocated to remaining service performance obligations associated with subsidized devices and promotional bill credits acquired through the Merger at April 1, 2020, was $1.0 billion. Through the Merger, on April 1, 2020, we acquired contracts associated with lease promotional credits with aggregate amount of transaction price allocated to remaining service and lease performance obligations of $4.8 billion and $2.6 billion, respectively. As of December 31, 2020, the aggregate amount of transaction price allocated to remaining service and lease performance obligations associated with operating leases was $2.1 billion and $1.2 billion, respectively. We expect to recognize this revenue as service is provided over the lease contract term of 18 months. Information about remaining performance obligations that are part of a contract that has an original expected duration of one year or less have been excluded from the above, which primarily consists of monthly service contracts. Certain of our wholesale, roaming and other service contracts include variable consideration based on usage. This variable consideration has been excluded from the disclosure of remaining performance obligations. As of December 31, 2020, the aggregate amount of the contractual minimum consideration for wholesale, roaming and other service contracts is $1.3 billion, $1.1 billion and $317 million for 2021, 2022, and 2023 and beyond, respectively. These contracts have a remaining duration ranging from less than one year to nine years. Contract Costs The total balance of deferred incremental costs to obtain contracts was $1.1 billion and $906 million as of December 31, 2020 and 2019, respectively, and is included in Other assets in our Consolidated Balance Sheets. Deferred contract costs incurred to obtain postpaid service contracts are amortized over a period of 24 months. The amortization period is monitored to reflect any significant change in assumptions. Amortization of deferred contract costs is included in Selling, general and administrative expenses in our Consolidated Statements of Comprehensive Income and was $865 million and $604 million for the years ended December 31, 2020 and 2019, respectively. Immediately preceding the close of the Merger, Sprint had deferred costs to obtain postpaid contracts of approximately $1.7 billion. This balance was adjusted to zero as part of our purchase price allocation. Contract costs capitalized for new postpaid contracts will accumulate in Other assets in our Consolidated Balance Sheets from the Merger close date. As a result, there was a net benefit to Operating income in our Consolidated Statements of Comprehensive Income during the year ended December 31, 2020, as capitalization of costs exceed amortization. As capitalized costs amortize into expense over time, the accretive benefit to Operating income is expected to moderate in 2021 and normalize in 2022. The deferred contract cost asset is assessed for impairment on a periodic basis. There were no impairment losses recognized on deferred contract cost assets for the years ended December 31, 2020 and 2019.

Employee Compensation and Benef

Employee Compensation and Benefit Plans	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Employee Compensation and Benefit Plans	Note 11 – Employee Compensation and Benefit Plans Under our 2013 Omnibus Incentive Plan and the Sprint Corporation Amended and Restated 2015 Omnibus Incentive Plan that T-Mobile assumed in connection with the closing of the Merger, as described below (the “Incentive Plans”), we are authorized to issue up to 101 million shares of our common stock. Under our Incentive Plans, we can grant stock options, stock appreciation rights, restricted stock, restricted stock units (“RSUs”), and performance awards to eligible employees, consultants, advisors and non-employee directors. As of December 31, 2020, there were approximately 25 million shares of common stock available for future grants under our Incentive Plans. We grant RSUs to eligible employees, key executives and certain non-employee directors and performance-based restricted stock units (“PRSUs”) to eligible key executives. RSUs entitle the grantee to receive shares of our common stock upon vesting (with vesting generally occurring annually over a three-year period), subject to continued service through the applicable vesting date. PRSUs entitle the holder to receive shares of our common stock at the end of a performance period of generally up to three years if the applicable performance goals are achieved and generally subject to continued service through the applicable performance period. The number of shares ultimately received by the holder of PRSUs is dependent on our business performance against the specified performance goal(s) over a pre-established performance period. We also maintain an employee stock purchase plan (“ESPP”), under which eligible employees can purchase our common stock at a discounted price. Stock-based compensation expense and related income tax benefits were as follows: As of and for the Year Ended December 31, (in millions, except shares, per share and contractual life amounts) 2020 2019 2018 Stock-based compensation expense $ 694 $ 495 $ 424 Income tax benefit related to stock-based compensation $ 132 $ 92 $ 81 Weighted average fair value per stock award granted $ 96.27 $ 73.25 $ 61.52 Unrecognized compensation expense $ 592 $ 515 $ 547 Weighted average period to be recognized (years) 1.9 1.6 1.8 Fair value of stock awards vested $ 1,315 $ 512 $ 471 Stock Awards On April 1, 2020, we closed the Merger to combine T-Mobile and Sprint pursuant to the Business Combination Agreement. Pursuant to the Business Combination Agreement, upon the completion of the Merger, T-Mobile assumed Sprint’s stock compensation plans. In addition, pursuant to the Business Combination Agreement, at the Effective Time, each outstanding option to purchase Sprint common stock (other than under Sprint’s Employee Stock Purchase Plan), each award of time-based RSUs in respect of shares of Sprint common stock and each award of performance-based RSUs in respect of shares of Sprint common stock, in each case, that was outstanding as of immediately prior to the Effective Time was automatically adjusted by the Exchange Ratio (as defined in the Business Combination Agreement) and converted into an equity award of the same type covering shares of T-Mobile common stock, on the same terms and conditions, (including, if applicable, any continuing vesting requirements (but excluding any performance-based vesting conditions)) under the applicable Sprint plan and award agreement in effect immediately prior to the Effective Time (the “Assumed Awards”). The applicable amount of performance-based RSUs eligible for conversion was based on formulas and approximated 100% of target. Any accrued but unpaid dividend equivalents with respect to any such award of time-based RSUs or performance-based RSUs were assumed by T-Mobile at the Effective Time and became an obligation with respect to the applicable award of RSUs in respect of shares of T-Mobile common stock. On April 22, 2020, we filed a Form S-8 to register a total of 25,304,224 shares of common stock, representing those covered by the Sprint Corporation 1997 Long-Term Stock Incentive Program, the Sprint Corporation 2007 Omnibus Incentive Plan and the Sprint Corporation Amended and Restated 2015 Omnibus Incentive Plan (the “2015 Plan”) that T-Mobile assumed in connection with the closing of the Merger. This included 7,043,843 shares of T-Mobile common stock issuable upon exercise or settlement of the Assumed Awards held by current directors, officers, employees and consultants of T-Mobile or its subsidiaries who were directors, officers, employees and consultants of Sprint or its subsidiaries immediately prior to the Effective Time, as well as (i) 12,420,945 shares of T-Mobile common stock that remain available for issuance under the 2015 Plan and (ii) 5,839,436 additional shares of T-Mobile common stock subject to awards granted under the 2015 Plan that may become available for issuance under the 2015 Plan if any awards under the 2015 Plan are forfeited, lapse unexercised or are settled in cash. Time-Based Restricted Stock Units and Restricted Stock Awards (in millions, except shares, per share and contractual life amounts) Number of Units or Awards Weighted Average Grant Date Fair Value Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Nonvested, December 31, 2019 10,503,211 $ 67.31 0.9 $ 824 Assumed through acquisition 1,852,527 83.90 Granted 5,891,303 97.18 Vested (7,112,552) 69.32 Forfeited (1,033,267) 84.52 Nonvested, December 31, 2020 10,101,222 84.61 0.9 1,362 Performance-Based Restricted Stock Units and Restricted Stock Awards (in millions, except shares, per share and contractual life amounts) Number of Units or Awards Weighted Average Grant Date Fair Value Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Nonvested, December 31, 2019 3,803,539 $ 69.78 1.0 $ 300 Assumed through acquisition 3,535,384 83.90 Granted 1,212,522 110.38 Performance award achievement adjustments (1) 887,528 70.96 Vested (6,127,838) 77.11 Forfeited (138,034) 83.90 Nonvested, December 31, 2020 3,173,101 86.58 1.0 428 PRSUs included in the table above are shown at target. Share payout can range from 0% to 200% based on different performance outcomes. Weighted average grant date fair value of RSU and PRSU assumed through acquisition is based on the fair value on the date assumed. (1) Represents PRSUs granted prior to 2020 for which the performance achievement period was completed in 2020, resulting in incremental unit awards. These PRSU awards are also included in the amount vested in 2020. Payment of the underlying shares in connection with the vesting of RSU and PRSU awards generally triggers a tax obligation for the employee, which is required to be remitted to the relevant tax authorities. We have agreed to withhold shares of common stock otherwise issuable under the RSU and PRSU awards to cover certain of these tax obligations, with the net shares issued to the employee accounted for as outstanding common stock. We withheld 4,441,107 and 2,094,555 shares of common stock to cover tax obligations associated with the payment of shares upon vesting of stock awards and remitted cash of $439 million and $156 million to the appropriate tax authorities for the years ended December 31, 2020 and 2019, respectively. Employee Stock Purchase Plan Our ESPP allows eligible employees to contribute up to 15% of their eligible earnings toward the semi-annual purchase of our shares of common stock at a discounted price, subject to an annual maximum dollar amount. Employees can purchase stock at a 15% discount applied to the closing stock price on the first or last day of the six-month offering period, whichever price is lower. The number of shares issued under our ESPP was 2,144,036 and 2,091,650 for the years ended December 31, 2020 and 2019, respectively. As of December 31, 2020, the number of securities remaining available for future sale and issuance under the ESPP was 4,253,858. Sprint’s ESPP was terminated prior to the Merger close and legacy Sprint employees were eligible to enroll in our ESPP on August 15, 2020. Our ESPP provides for an annual increase in the aggregate number of shares of our common stock reserved for sale and authorized for issuance thereunder as of the first day of each fiscal year (beginning with fiscal year 2016) equal to the lesser of (i) 5,000,000 shares of our common stock, and (ii) the number of shares of T-Mobile common stock determined by the Compensation Committee of the Board of Directors of the Company (the “Compensation Committee”). For fiscal years 2016 through 2019, the Compensation Committee determined that no such increase in shares of our common stock was necessary. However, an additional 5,000,000 shares of our common stock were automatically added to the ESPP share reserve as of January 1, 2020 and 2021, respectively. Stock Options Stock options outstanding relate to the Metro Communications, Inc. 2010 Equity Incentive Compensation Plan, the Amended and Restated Metro Communications, Inc. 2004 Equity Incentive Compensation Plan, the Layer3 TV, Inc. 2013 Stock Plan, and the Sprint 2015 Plan (collectively, the “Stock Option Plans”). No new awards may be granted under the Stock Option Plans, and no awards were granted during the year ended December 31, 2020. The following activity occurred under the Stock Option Plans: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Outstanding at December 31, 2019 194,942 $ 13.80 2.9 Assumed through acquisition 1,635,518 33.37 Exercised (906,295) 53.02 Expired/canceled (5,470) 49.75 Outstanding at December 31, 2020 918,695 51.77 4.0 Exercisable at December 31, 2020 917,955 51.79 4.0 Weighted average grant date fair value of stock options assumed through acquisition is based on the fair value on the date assumed. Stock options exercised under the Stock Option Plans generated proceeds of approximately $48 million and $1 million for the years ended December 31, 2020 and 2019, respectively. The grant-date fair value of share-based incentive compensation awards attributable to post-combination services, including restricted stock units and stock options, from our Merger with Sprint was approximately $163 million. Pension and Other Post Retirement Benefits Plans Upon the completion of our Merger with Sprint, we acquired the assets and assumed the liabilities associated with the Sprint Retirement Pension Plan (the “Pension Plan”) as well as other postretirement employee benefit plans. As of December 31, 2005, the Pension Plan was amended to freeze benefit plan accruals for the participants. The plan assets acquired and obligations assumed were recognized at fair value on the Merger close date. The objective for the investment portfolio of the Pension Plan is to achieve a long-term nominal rate of return, net of fees, that exceeds the Pension Plan's long-term expected rate of return on investments for funding purposes. To meet this objective, our investment strategy is governed by an asset allocation policy, whereby a targeted allocation percentage is assigned to each asset class as follows: 24% to U.S. equities; 17% to international equities; 44% to fixed income investments; 11% to real estate investments; and 4% to other investments including hedge funds. Actual allocations are allowed to deviate from target allocation percentages within a range for each asset class as defined in the investment policy. The long-term expected rate of return on plan assets was 5% for the year ended December 31, 2020, while the actual rate of return on plan assets was 21% during that period. The long-term expected rate of return on investments for funding purposes is 4% for the year ended December 31, 2021. The components of net expense recognized for the Pension Plan were as follows: (in millions) Year Ended December 31, 2020 Interest on projected benefit obligations $ 52 Expected return on pension plan assets (45) Net pension expense $ 7 The net expense associated with the Pension Plan is included in Other expense, net of our Consolidated Statements of Comprehensive Income. Investments of the Pension Plan are measured at fair value on a recurring basis, which is determined using quoted market prices or estimated fair values. As of December 31, 2020, 12% of the investment portfolio was valued at quoted prices in active markets for identical assets, 85% was valued using quoted prices for similar assets in active or inactive markets, or other observable inputs, and 3% was valued using unobservable inputs that are supported by little or no market activity, the majority of which used the net asset value per share (or its equivalent) as a practical expedient to measure the fair value. The fair values of our Pension Plan assets and certain other postretirement benefit plan assets in aggregate were $1.2 billion and $1.4 billion and our accumulated benefit obligations in aggregate were $2.1 billion and $2.3 billion as of April 1, 2020 and December 31, 2020, respectively. As a result, the plans were underfunded by approximately $892 million and $828 million as of April 1, 2020 and December 31, 2020, respectively, and were recorded in Other long-term liabilities in our Consolidated Balance Sheets. In determining our pension obligation for the year ended December 31, 2020, we used a weighted-average discount rate of 3%. During the year ended December 31, 2020, we made contributions of $58 million to the benefit plans. No contributions were made by T-Mobile in fiscal periods prior to 2020. We expect to make contributions to the Plan of $89 million through the year ending December 31, 2021. Future benefits expected to be paid are approximately $97 million for the year ending December 31, 2021, $198 million in total for the years ending December 31, 2022 and 2023, $206 million in total for the years ending December 31, 2024 and 2025, and $548 million in total for the years ending December 31, 2026, through December 31, 2030. Employee Retirement Savings Plan We sponsor retirement savings plans for the majority of our employees under Section 401(k) of the Internal Revenue Code and similar plans. The plans allow employees to contribute a portion of their pretax and post-tax income in accordance with specified guidelines. The plans provide that we match a percentage of employee contributions up to certain limits. Employer matching contributions were $179 million, $119 million and $102 million for the years ended December 31, 2020, 2019 and 2018, respectively.

Discontinued Operations and Dis

Discontinued Operations and Disposal Groups	12 Months Ended
	Dec. 31, 2020
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Note 12 – Discontinued Operations On July 26, 2019, we entered into an Asset Purchase Agreement with Sprint and DISH. On June 17, 2020, T-Mobile, Sprint and DISH entered into the First Amendment. Pursuant to the First Amendment to the Asset Purchase Agreement, T-Mobile, Sprint and DISH agreed to proceed with the closing of the Prepaid Transaction in accordance with the Asset Purchase Agreement on July 1, 2020, subject to the terms and conditions of the Asset Purchase Agreement and the terms and conditions of the Consent Decree. On July 1, 2020, pursuant to the Asset Purchase Agreement, upon the terms and subject to the conditions thereof, we completed the Prepaid Transaction. Upon closing of the Prepaid Transaction, we received $1.4 billion from DISH for the Prepaid Business, subject to a working capital adjustment. The close of the Prepaid Transaction did not have a significant impact on our Consolidated Statements of Comprehensive Income. The assets of the Prepaid Business included EIP receivables originated pursuant to financed equipment purchases by customers of the Prepaid Business. At the time of the Prepaid Transaction, DISH did not hold certain licenses required to purchase or originate such contracts. In order to transfer the economics of the contracts to DISH without transferring ownership of them, the parties entered into a Participation Agreement under which we agreed to transfer a 100% participation interest in the contracts to DISH. Under the terms of the agreement, DISH retains all cash flows collected on these assets, and there is no recourse against us for any credit losses on such loans. The proceeds received from DISH in exchange for this participation interest was a component of total consideration received for the Prepaid Transaction. We will temporarily continue to originate equipment installment contracts on DISH’s behalf under the same terms in exchange for an amount equal to the initial outstanding principal balance of the originated contracts, again without recourse against us for any credit losses. Of the total $1.4 billion of proceeds received under the Prepaid Transaction, approximately $162 million was allocated to the EIP receivables to which we transferred DISH a 100% participation interest. We accounted for this portion of the proceeds as a secured borrowing and present it in Other, net, within Net cash provided by (used in) financing activities in our Consolidated Statements of Cash Flows accordingly. The remaining $1.2 billion was allocated to the divested net assets of the Prepaid Business. The net cash received for the Prepaid Business is presented in Proceeds from the divestiture of prepaid business within Net cash used in investing activities in our Consolidated Statements of Cash Flows. The results of the Prepaid Business include revenues and expenses directly attributable to the operations disposed. Corporate and administrative expenses, including Interest expense, not directly attributable to the operations were not allocated to the Prepaid Business. The results of the Prepaid Business from April 1, 2020, through December 31, 2020, are presented in Income from discontinued operations, net of tax in our Consolidated Statements of Comprehensive Income. The components of discontinued operations from the Merger close date of April 1, 2020, through December 31, 2020, were as follows: (in millions) Year Ended Major classes of line items constituting pretax income from discontinued operations Prepaid revenues $ 973 Roaming and other service revenues 27 Total service revenues 1,000 Equipment revenues 270 Total revenues 1,270 Cost of services 25 Cost of equipment sales 499 Selling, general and administrative 314 Total operating expenses 838 Pretax income from discontinued operations 432 Income tax expense (112) Income from discontinued operations $ 320 Net cash provided by operating activities from the Prepaid Business included in the Consolidated Statements of Cash Flows for the year ended December 31, 2020, were $611 million, all of which relates to the operations of the Prepaid Business during the three months ended June 30, 2020. There were no cash flows from investing or financing activities related to the Prepaid Business for the year ended December 31, 2020. Continuing Involvement Upon the closing of the Prepaid Transaction, we and DISH entered into (i) a License Purchase Agreement pursuant to which (a) DISH has the option to purchase certain 800 MHz spectrum licenses for a total of approximately $3.6 billion in a transaction to be completed, subject to certain additional closing conditions, following an application for FCC approval to be filed three years following the closing of the Merger and (b) we will have the option to lease back from DISH, as needed, a portion of the spectrum sold for an additional two years following the closing of the spectrum sale transaction, (ii) a Transition Services Agreement providing for our provisioning of transition services to DISH in connection with the Prepaid Business for a period of up to three years following the closing of the Prepaid Transaction, (iii) a Master Network Services Agreement providing for the provisioning of network services to customers of the Prepaid Business for a period of up to seven years following the closing of the Prepaid Transaction, and (iv) an Option to Acquire Tower and Retail Assets, offering DISH the option to acquire certain decommissioned towers and retail locations from us, subject to obtaining all necessary third-party consents, for a period of up to five years following the closing of the Prepaid Transaction. In the event DISH breaches the License Purchase Agreement or fails to deliver the purchase price following the satisfaction or waiver of all closing conditions, DISH’s sole liability is to pay us a fee of approximately $72 million. Additionally, if DISH does not exercise the option to purchase the 800 MHz spectrum licenses, we have an obligation to offer the licenses for sale through an auction. If the specified minimum price of $3.6 billion was not met in the auction, we would retain the licenses. As the sale of 800 MHz spectrum licenses is not expected to close within one year, the criteria for presentation as an asset held for sale is not met. Cash flows associated with the Master Network Services Agreement and Transition Services Agreement are included within Net cash provided by operating activities in our Consolidated Statements of Cash Flows.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 13 – Income Taxes Our sources of Income before income taxes were as follows: Year Ended December 31, (in millions) 2020 2019 2018 U.S. $ 3,493 $ 4,557 $ 3,686 Foreign 37 46 231 Income from continuing operations before income taxes $ 3,530 $ 4,603 $ 3,917 Income tax expense is summarized as follows: Year Ended December 31, (in millions) 2020 2019 2018 Current tax benefit (expense) Federal $ 17 $ 24 $ 39 State (84) (70) (63) Foreign (10) 2 (25) Total current tax expense (77) (44) (49) Deferred tax benefit (expense) Federal (676) (954) (750) State (34) (125) (160) Foreign 1 (12) (70) Total deferred tax expense (709) (1,091) (980) Total income tax expense $ (786) $ (1,135) $ (1,029) The reconciliation between the U.S. federal statutory income tax rate and our effective income tax rate is as follows: Year Ended December 31, 2020 2019 2018 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % Effect of law and rate changes (0.8) 0.4 1.9 Change in valuation allowance (2.6) (1.8) (1.6) State taxes, net of federal benefit 4.8 5.1 4.8 Foreign taxes, net of federal benefit 0.3 0.3 2.4 Permanent differences 0.4 0.6 0.7 Federal tax credits, net of reserves (0.9) (0.8) (2.9) Equity-based compensation (2.5) (0.6) (0.8) Non-deductible compensation 2.3 0.6 0.8 Other, net 0.3 (0.1) — Effective income tax rate 22.3 % 24.7 % 26.3 % Significant components of deferred income tax assets and liabilities, tax effected, are as follows: (in millions) December 31, December 31, Deferred tax assets Loss carryforwards $ 4,540 $ 823 Lease liabilities 8,031 3,403 Property and equipment 90 — Reserves and accruals 1,348 659 Federal and state tax credits 411 331 Other 2,665 903 Deferred tax assets, gross 17,085 6,119 Valuation allowance (878) (129) Deferred tax assets, net 16,207 5,990 Deferred tax liabilities Spectrum licenses 17,518 5,902 Property and equipment — 2,506 Lease right-of-use assets 7,239 2,881 Other intangible assets 912 19 Other 504 289 Total deferred tax liabilities 26,173 11,597 Net deferred tax liabilities $ 9,966 $ 5,607 Classified on the balance sheet as: Deferred tax liabilities $ 9,966 $ 5,607 As of December 31, 2020, we have tax effected federal net operating loss (“NOL”) carryforwards of $3.5 billion, state NOL carryforwards of $1.5 billion and foreign NOL carryforwards of $67 million, expiring through 2040. Federal and certain state NOLs generated in and after 2018 do not expire. As of December 31, 2020, our tax effected federal, state and foreign NOL carryforwards for financial reporting purposes were approximately $176 million, $455 million and $26 million, respectively, less than our NOL carryforwards for federal, state and foreign income tax purposes, due to unrecognized tax benefits of the same amount. The unrecognized tax benefit amounts exclude offsetting tax effects of $144 million in other jurisdictions. As of December 31, 2020, we have research and development, foreign tax and other general business credit carryforwards with a combined value of $569 million for federal income tax purposes, an immaterial amount of which begins to expire in 2021. As a result of the Merger, we acquired additional deferred tax assets for which a valuation allowance reserve is deemed to be necessary, as well as additional uncertain tax benefit reserves. Due to the size and complexity of the Merger, our estimate of these amounts is preliminary and is subject to finalization and adjustment, which could be material, during the measurement period of up to one year from the Merger close date. During the measurement period, we will adjust these amounts if new information is obtained about facts or circumstances that existed as of the acquisition date that, if known, would have changed these amounts. See Note 2 - Business Combination for further information. As of December 31, 2020, 2019 and 2018, our valuation allowance was $878 million, $129 million and $210 million, respectively. The change from December 31, 2019, to December 31, 2020, primarily related to $848 million of deferred tax assets acquired via the Merger for which a valuation allowance is deemed necessary, partially offset by a reduction in the valuation allowance against deferred tax assets in federal and certain other jurisdictions associated with additional tax attribute utilization and expiration. The change from December 31, 2018, to December 31, 2019, primarily related to a reduction in the valuation allowance against deferred tax assets in certain state jurisdictions resulting from legal entity reorganizations. We will continue to monitor positive and negative evidence related to the utilization of the remaining deferred tax assets for which a valuation allowance continues to be provided. It is possible that our valuation allowance may change within the next 12 months. We file income tax returns in the U.S. federal jurisdiction and in various state and foreign jurisdictions. We are currently under examination by various states. Management does not believe the resolution of any of the audits will result in a material change to our financial condition, results of operations or cash flows. The IRS has concluded its audits of our federal tax returns through the 2009 tax year; however, NOL and other carryforwards for certain audited periods remain open for examination. U.S. federal, state and foreign examination for years prior to 2001 are generally closed. A reconciliation of the beginning and ending amount of unrecognized tax benefits were as follows: Year Ended December 31, (in millions) 2020 2019 2018 Unrecognized tax benefits, beginning of year $ 514 $ 462 $ 412 Gross increases to tax positions in prior periods 6 — 16 Gross decreases to tax positions in prior periods (28) — (11) Gross increases to current period tax positions 45 64 39 Gross increases due to current period business acquisitions 624 — 10 Gross decreases due to settlements with taxing authorities (2) (12) (4) Unrecognized tax benefits, end of year $ 1,159 $ 514 $ 462 As of December 31, 2020, 2019 and 2018, we had $857 million, $310 million and $263 million, respectively, in unrecognized tax benefits that, if recognized, would affect our annual effective tax rate. The balance as of December 31, 2020 includes measurement period adjustments associated with the Merger to reflect facts and circumstances in existence as of the effective time of the Merger. Our estimate of these unrecognized tax benefits is preliminary and is subject to finalization and adjustment, which could be material, during the measurement period of up to one year from the Merger close date. Penalties and interest on income tax assessments are included in Selling, general and administrative expenses and Interest expense, respectively, in our Consolidated Statements of Comprehensive Income. The accrued interest and penalties associated with unrecognized tax benefits are insignificant.

SoftBank Equity Transaction

SoftBank Equity Transaction	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
SoftBank Equity Transaction	Note 14 – SoftBank Equity Transaction On June 22, 2020, we entered into a Master Framework Agreement (the “Master Framework Agreement”) by and among the Company, SoftBank, SoftBank Group Capital Ltd, a wholly owned subsidiary of SoftBank (“SBGC”), Delaware Project 4 L.L.C., a wholly owned subsidiary of SoftBank, Delaware Project 6 L.L.C., a wholly owned subsidiary of SoftBank, Claure Mobile LLC (“CM LLC”), DT, and T-Mobile Agent LLC, a wholly owned subsidiary of the Company. The Master Framework Agreement and related transactions were entered into to facilitate SoftBank’s monetization of a portion of our common stock held by SoftBank (the “SoftBank Monetization”). In connection with the Master Framework Agreement, DT waived the restriction on the transfer under its Proxy, Lock-Up and ROFR Agreement, dated April 1, 2020, with SoftBank (the “SoftBank Proxy Agreement”) with respect to approximately 198 million shares of our common stock held by SoftBank (the “Released Shares”). Upon the close of the Public Equity Offering (as defined below), we received a payment from SoftBank for $304 million for our role in facilitating the SoftBank Monetization. The payment received from SoftBank, net of tax, of $230 million was recorded as Additional paid-in capital in our Consolidated Balance Sheets and is presented as a reduction of Repurchases of common stock within Net cash provided by (used in) financing activities within our Consolidated Statements of Cash Flows . Under the terms of the Master Framework Agreement and the agreements contemplated thereby, SBGC sold the Released Shares to us, and we participated in the following transactions: Public Equity Offering On June 26, 2020, we completed a registered public offering of approximately 154.1 million shares of our common stock ( the “Public Equity Offering”) at a price of $103.00 per share. The net proceeds of the Public Equity Offering were used to repurchase an equal number of issued and outstanding shares of our common stock from SBGC, pursuant to a Share Repurchase Agreement, dated as of June 22, 2020 (the “Share Repurchase Agreement”), between us and SBGC. Mandatory Exchangeable Offering Concurrent with the Public Equity Offering, we sold approximately 19.4 million shares of our common stock to a third-party trust. The net proceeds from the sale of shares to the trust were used to repurchase an equal number of issued and outstanding shares of our common stock from SBGC. The trust issued mandatory exchangeable trust securities, which entitle holders to receive quarterly distributions from the trust and a final mandatory exchange price to be settled on June 1, 2023 (“Mandatory Exchangeable Offering”). The trust was required to use a portion of the net proceeds from the Mandatory Exchangeable Offering to purchase U.S. Treasury securities, to fund quarterly distributions on the mandatory exchangeable trust securities, and the holders of the mandatory exchangeable trust securities will be entitled to a final mandatory exchange amount on June 1, 2023 that will depend on the daily volume-weighted average price of shares of our common stock. The sale of shares through the Public Equity Offering and to the trust occurred simultaneously with the purchase of shares from SBGC. These simultaneous transactions did not result in a net change to our treasury shares or shares of common stock outstanding. As these transactions occurred with separate counterparties, the exchange of shares and cash are presented on a gross basis in our Consolidated Statement of Stockholders’ Equity and Consolidated Statements of Cash Flows, respectively. The shares sold are presented in Shares issued in secondary offering and the shares purchased from SBGC are presented in Shares repurchased from SoftBank within our Consolidated Statement of Stockholders’ Equity. The cash received from the sale of shares is presented in Issuance of common stock and the cash paid to purchase shares from SoftBank are presented in Repurchases of common stock within Net cash provided by (used in) financing activities within our Consolidated Statements of Cash Flows. The Company is not affiliated with the trust, will not retain any proceeds from the offering of the trust securities, and will have no ongoing interest, economic or otherwise, in the trust securities. Rights Offering The Master Framework Agreement provides for the issuance of registered, transferable subscription rights (the “Rights Offering”) resulting in the sale of 19,750,000 shares of our common stock to our stockholders (other than SoftBank, DT and Marcelo Claure and their respective affiliates, who agreed to waive their ability to exercise or transfer such rights). The subscription rights provided the stockholders the option to purchase one share of common stock for every 20 shares of common stock owned, at the same price per share as the common stock sold in the Public Equity Offering of $103.00 per share. The Rights Offering exercise period expired on July 27, 2020. On August 3, 2020, the Rights Offering closed, resulting in the sale of 19,750,000 shares of our common stock. The net proceeds from the Rights Offering were used to purchase an equal number of shares from SBGC pursuant to the Share Repurchase Agreement. Marcelo Claure The Master Framework Agreement provided for the purchase of 5.0 million shares of our common stock by Marcelo Claure, a member of our board of directors, from us at the same price per share as the common stock sold in the Public Equity Offering of $103.00 per share. Following receipt of the necessary regulatory approvals on July 16, 2020, the sale of shares to Marcelo Claure occurred simultaneously with our purchase of an equivalent number of shares from SBGC at the same price per share pursuant to the Share Repurchase Agreement. Ownership Following the SoftBank Monetization As of December 31, 2020, DT and SoftBank held, directly or indirectly, approximately 43.4% and 8.6%, respectively, of the outstanding T-Mobile common stock, with the remaining approximately 48.0% of the outstanding T-Mobile common stock held by other stockholders. The SoftBank Proxy Agreement remains in effect with respect to the remaining shares of our common stock held by SoftBank. In addition, on June 22, 2020, DT, CM LLC, and Marcelo Claure entered into a Proxy, Lock-Up and ROFR Agreement (the “Claure Proxy Agreement,” together with the SoftBank Proxy Agreement, the “Proxy Agreements”), pursuant to which any shares of our common stock acquired after June 22, 2020 by Mr. Claure or CM LLC, an entity controlled by Mr. Claure, other than shares acquired as a result of Mr. Claure’s role as a director or officer of the Company, will be voted in the manner as directed by DT. Accordingly, as a result of the Proxy Agreements, DT has voting control as of December 31, 2020 over approximately 52.3% of the outstanding T-Mobile common stock. DT Call Option In exchange for DT consenting to the transfer of the Released Shares and as provided for in the Master Framework Agreement, DT received direct and indirect call options over up to approximately 101.5 million shares of our common stock held by SBGC. The arrangement provided DT with a fixed-price call option to purchase up to approximately 44.9 million shares at a price of $101.46 per share indirectly from SBGC through a back-to-back arrangement where (i) DT could purchase such shares from us (the “DT Fixed-Price Call Option”) and (ii) we would fulfill our obligations under the DT Fixed-Price Call Option by simultaneously purchasing the same number of shares on the same economic terms from SBGC (the “T-Mobile Fixed-Price Call Option”). In addition, DT has a floating-price call option to purchase up to approximately 56.6 million shares from SBGC directly. The DT Fixed-Price Call Option and the T-Mobile Fixed-Price Call Option represented free-standing derivatives and were recorded at fair value and marked-to-market each period. As the mark-to-market valuations of the T-Mobile Fixed-Price Call Option and the DT Fixed-Price Call Option moved in equal and offsetting directions, there was no net impact on our Consolidated Statements of Comprehensive Income. On October 6, 2020, we assigned our rights under the T-Mobile Fixed-Price Call Option to DT and DT terminated its right to purchase shares from us under the DT Fixed-Price Call Option, resulting in derecognition of the related derivative asset and liability in equal and offsetting amounts of $1.0 billion such that there was no net impact to our Consolidated Statements of Comprehensive Income. Note 15 – Repurchases of Common Stock 2017 Stock Repurchase Program On December 6, 2017, our Board of Directors authorized a stock repurchase program for up to $1.5 billion of our common stock through December 31, 2018 (the “2017 Stock Repurchase Program”). Repurchased shares are retired. The 2017 Stock Repurchase Program completed on April 29, 2018. The following table summarizes information regarding repurchases of our common stock under the 2017 Stock Repurchase Program: (In millions, except shares and per share price) Year ended December 31, Number of Shares Repurchased Average Price Paid Per Share Total Purchase Price 2018 16,738,758 $ 62.96 $ 1,054 Stock Purchases by Affiliate In the first quarter of 2018, DT, our majority stockholder and an affiliated purchaser, purchased 3.3 million additional shares of our common stock at an aggregate market value of $200 million in the public market or from other parties, in accordance with the rules of the SEC and other applicable legal requirements. There were no purchases in 2019 and 2020. We did not receive proceeds from these purchases.

Repurchases of Common Stock

Repurchases of Common Stock	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Repurchases of Common Stock	Note 14 – SoftBank Equity Transaction On June 22, 2020, we entered into a Master Framework Agreement (the “Master Framework Agreement”) by and among the Company, SoftBank, SoftBank Group Capital Ltd, a wholly owned subsidiary of SoftBank (“SBGC”), Delaware Project 4 L.L.C., a wholly owned subsidiary of SoftBank, Delaware Project 6 L.L.C., a wholly owned subsidiary of SoftBank, Claure Mobile LLC (“CM LLC”), DT, and T-Mobile Agent LLC, a wholly owned subsidiary of the Company. The Master Framework Agreement and related transactions were entered into to facilitate SoftBank’s monetization of a portion of our common stock held by SoftBank (the “SoftBank Monetization”). In connection with the Master Framework Agreement, DT waived the restriction on the transfer under its Proxy, Lock-Up and ROFR Agreement, dated April 1, 2020, with SoftBank (the “SoftBank Proxy Agreement”) with respect to approximately 198 million shares of our common stock held by SoftBank (the “Released Shares”). Upon the close of the Public Equity Offering (as defined below), we received a payment from SoftBank for $304 million for our role in facilitating the SoftBank Monetization. The payment received from SoftBank, net of tax, of $230 million was recorded as Additional paid-in capital in our Consolidated Balance Sheets and is presented as a reduction of Repurchases of common stock within Net cash provided by (used in) financing activities within our Consolidated Statements of Cash Flows . Under the terms of the Master Framework Agreement and the agreements contemplated thereby, SBGC sold the Released Shares to us, and we participated in the following transactions: Public Equity Offering On June 26, 2020, we completed a registered public offering of approximately 154.1 million shares of our common stock ( the “Public Equity Offering”) at a price of $103.00 per share. The net proceeds of the Public Equity Offering were used to repurchase an equal number of issued and outstanding shares of our common stock from SBGC, pursuant to a Share Repurchase Agreement, dated as of June 22, 2020 (the “Share Repurchase Agreement”), between us and SBGC. Mandatory Exchangeable Offering Concurrent with the Public Equity Offering, we sold approximately 19.4 million shares of our common stock to a third-party trust. The net proceeds from the sale of shares to the trust were used to repurchase an equal number of issued and outstanding shares of our common stock from SBGC. The trust issued mandatory exchangeable trust securities, which entitle holders to receive quarterly distributions from the trust and a final mandatory exchange price to be settled on June 1, 2023 (“Mandatory Exchangeable Offering”). The trust was required to use a portion of the net proceeds from the Mandatory Exchangeable Offering to purchase U.S. Treasury securities, to fund quarterly distributions on the mandatory exchangeable trust securities, and the holders of the mandatory exchangeable trust securities will be entitled to a final mandatory exchange amount on June 1, 2023 that will depend on the daily volume-weighted average price of shares of our common stock. The sale of shares through the Public Equity Offering and to the trust occurred simultaneously with the purchase of shares from SBGC. These simultaneous transactions did not result in a net change to our treasury shares or shares of common stock outstanding. As these transactions occurred with separate counterparties, the exchange of shares and cash are presented on a gross basis in our Consolidated Statement of Stockholders’ Equity and Consolidated Statements of Cash Flows, respectively. The shares sold are presented in Shares issued in secondary offering and the shares purchased from SBGC are presented in Shares repurchased from SoftBank within our Consolidated Statement of Stockholders’ Equity. The cash received from the sale of shares is presented in Issuance of common stock and the cash paid to purchase shares from SoftBank are presented in Repurchases of common stock within Net cash provided by (used in) financing activities within our Consolidated Statements of Cash Flows. The Company is not affiliated with the trust, will not retain any proceeds from the offering of the trust securities, and will have no ongoing interest, economic or otherwise, in the trust securities. Rights Offering The Master Framework Agreement provides for the issuance of registered, transferable subscription rights (the “Rights Offering”) resulting in the sale of 19,750,000 shares of our common stock to our stockholders (other than SoftBank, DT and Marcelo Claure and their respective affiliates, who agreed to waive their ability to exercise or transfer such rights). The subscription rights provided the stockholders the option to purchase one share of common stock for every 20 shares of common stock owned, at the same price per share as the common stock sold in the Public Equity Offering of $103.00 per share. The Rights Offering exercise period expired on July 27, 2020. On August 3, 2020, the Rights Offering closed, resulting in the sale of 19,750,000 shares of our common stock. The net proceeds from the Rights Offering were used to purchase an equal number of shares from SBGC pursuant to the Share Repurchase Agreement. Marcelo Claure The Master Framework Agreement provided for the purchase of 5.0 million shares of our common stock by Marcelo Claure, a member of our board of directors, from us at the same price per share as the common stock sold in the Public Equity Offering of $103.00 per share. Following receipt of the necessary regulatory approvals on July 16, 2020, the sale of shares to Marcelo Claure occurred simultaneously with our purchase of an equivalent number of shares from SBGC at the same price per share pursuant to the Share Repurchase Agreement. Ownership Following the SoftBank Monetization As of December 31, 2020, DT and SoftBank held, directly or indirectly, approximately 43.4% and 8.6%, respectively, of the outstanding T-Mobile common stock, with the remaining approximately 48.0% of the outstanding T-Mobile common stock held by other stockholders. The SoftBank Proxy Agreement remains in effect with respect to the remaining shares of our common stock held by SoftBank. In addition, on June 22, 2020, DT, CM LLC, and Marcelo Claure entered into a Proxy, Lock-Up and ROFR Agreement (the “Claure Proxy Agreement,” together with the SoftBank Proxy Agreement, the “Proxy Agreements”), pursuant to which any shares of our common stock acquired after June 22, 2020 by Mr. Claure or CM LLC, an entity controlled by Mr. Claure, other than shares acquired as a result of Mr. Claure’s role as a director or officer of the Company, will be voted in the manner as directed by DT. Accordingly, as a result of the Proxy Agreements, DT has voting control as of December 31, 2020 over approximately 52.3% of the outstanding T-Mobile common stock. DT Call Option In exchange for DT consenting to the transfer of the Released Shares and as provided for in the Master Framework Agreement, DT received direct and indirect call options over up to approximately 101.5 million shares of our common stock held by SBGC. The arrangement provided DT with a fixed-price call option to purchase up to approximately 44.9 million shares at a price of $101.46 per share indirectly from SBGC through a back-to-back arrangement where (i) DT could purchase such shares from us (the “DT Fixed-Price Call Option”) and (ii) we would fulfill our obligations under the DT Fixed-Price Call Option by simultaneously purchasing the same number of shares on the same economic terms from SBGC (the “T-Mobile Fixed-Price Call Option”). In addition, DT has a floating-price call option to purchase up to approximately 56.6 million shares from SBGC directly. The DT Fixed-Price Call Option and the T-Mobile Fixed-Price Call Option represented free-standing derivatives and were recorded at fair value and marked-to-market each period. As the mark-to-market valuations of the T-Mobile Fixed-Price Call Option and the DT Fixed-Price Call Option moved in equal and offsetting directions, there was no net impact on our Consolidated Statements of Comprehensive Income. On October 6, 2020, we assigned our rights under the T-Mobile Fixed-Price Call Option to DT and DT terminated its right to purchase shares from us under the DT Fixed-Price Call Option, resulting in derecognition of the related derivative asset and liability in equal and offsetting amounts of $1.0 billion such that there was no net impact to our Consolidated Statements of Comprehensive Income. Note 15 – Repurchases of Common Stock 2017 Stock Repurchase Program On December 6, 2017, our Board of Directors authorized a stock repurchase program for up to $1.5 billion of our common stock through December 31, 2018 (the “2017 Stock Repurchase Program”). Repurchased shares are retired. The 2017 Stock Repurchase Program completed on April 29, 2018. The following table summarizes information regarding repurchases of our common stock under the 2017 Stock Repurchase Program: (In millions, except shares and per share price) Year ended December 31, Number of Shares Repurchased Average Price Paid Per Share Total Purchase Price 2018 16,738,758 $ 62.96 $ 1,054 Stock Purchases by Affiliate In the first quarter of 2018, DT, our majority stockholder and an affiliated purchaser, purchased 3.3 million additional shares of our common stock at an aggregate market value of $200 million in the public market or from other parties, in accordance with the rules of the SEC and other applicable legal requirements. There were no purchases in 2019 and 2020. We did not receive proceeds from these purchases.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	Note 16 – Earnings Per Share The computation of basic and diluted earnings per share was as follows: Year Ended December 31, (in millions, except shares and per share amounts) 2020 2019 2018 Income from continuing operations $ 2,744 $ 3,468 $ 2,888 Income from discontinued operations, net of tax 320 — — Net income $ 3,064 $ 3,468 $ 2,888 Weighted average shares outstanding - basic 1,144,206,326 854,143,751 849,744,152 Effect of dilutive securities: Outstanding stock options and unvested stock awards 10,543,102 9,289,760 8,546,022 Weighted average shares outstanding - diluted 1,154,749,428 863,433,511 858,290,174 Basic earnings per share: Continuing operations $ 2.40 $ 4.06 $ 3.40 Discontinued operations 0.28 — — Earnings per share - basic $ 2.68 $ 4.06 $ 3.40 Diluted earnings per share: Continuing operations $ 2.37 $ 4.02 $ 3.36 Discontinued operations 0.28 — — Earnings per share - diluted $ 2.65 $ 4.02 $ 3.36 Potentially dilutive securities: Outstanding stock options and unvested stock awards 80,180 16,359 148,422 SoftBank contingent consideration (1) 36,630,268 — — (1) Represents the weighted average SoftBank Specified Shares outstanding from April 1, 2020, through December 31, 2020. On April 1, 2020, in connection with the closing of the Merger, we amended and restated the Company’s certificate of incorporation in the form of the Fifth Amended and Restated Certificate of Incorporation (the “Restated Certificate”). Pursuant to the Restated Certificate, the authorized capital stock of T-Mobile consists of 2,000,000,000 shares of T-Mobile common stock and 100,000,000 shares of preferred stock, par value $0.00001 per share. As of December 31, 2020, we had authorized 100 million shares of preferred stock, with a par value of $0.00001 per share. There was no preferred stock outstanding as of December 31, 2020 and 2019. Potentially dilutive securities were not included in the computation of diluted earnings per share if to do so would have been anti-dilutive or if there was a loss from continuing operations for the period.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	Lessee Through the Merger, we acquired leases of real property, including cell sites, switch sites, dark fiber, retail stores and office facilities and recorded lease liabilities and associated right-of-use assets based on the discounted lease payments. Lease terms that are favorable or unfavorable to market terms were recorded as an adjustment to lease right-of-use assets on our Consolidated Balance Sheets. Favorable and unfavorable leases are amortized on a straight-line basis over the associated remaining lease term. On September 14, 2020, T-Mobile and American Tower Corporation (“American Tower”) entered into a lease agreement (the “American Tower Lease Agreement”) that will enable us to lease American Tower towers through April 2035. The American Tower Lease Agreement extended the term and modified the rental payments for approximately 20,729 American Tower towers currently leased by us. As a result of this modification, we remeasured the associated right-of-use assets and lease liabilities resulting in an increase of $11.0 billion to each on the effective date of the modification. The components of lease expense were as follows: Year Ended December 31, (in millions) 2020 2019 Operating lease expense $ 4,438 $ 2,558 Financing lease expense: Amortization of right-of-use assets 681 523 Interest on lease liabilities 81 82 Total financing lease expense 762 605 Variable lease expense 328 243 Total lease expense $ 5,528 $ 3,406 Information relating to the lease term and discount rate is as follows: Year Ended December 31, 2020 2019 Weighted Average Remaining Lease Term (Years) Operating leases 10 6 Financing leases 3 3 Weighted Average Discount Rate Operating leases 3.9 % 4.8 % Financing leases 3.3 % 4.0 % Maturities of lease liabilities as of December 31, 2020, were as follows: (in millions) Operating Leases Finance Leases Twelve Months Ending December 31, 2021 $ 4,903 $ 1,121 2022 4,354 795 2023 3,759 422 2024 3,339 137 2025 2,807 92 Thereafter 18,940 61 Total lease payments 38,102 2,628 Less: imputed interest 7,515 121 Total $ 30,587 $ 2,507 Interest payments for financing leases were $79 million and $82 million for the years ended December 31, 2020 and 2019, respectively. As of December 31, 2020, we have additional operating leases for cell sites and commercial properties that have not yet commenced with future lease payments of approximately $227 million. As of December 31, 2020, we were contingently liable for future ground lease payments related to certain tower obligations. These contingent obligations are not included in the above table as the amounts owed are contractually owed by Crown Castle International Corp. based on the subleasing arrangement. See Note 9 - Tower Obligations for further information. Lessor Through the Merger, we acquired leased wireless devices with a fair value of $5.8 billion as of April 1, 2020. The components of leased wireless devices under our Leasing Programs were as follows: (in millions) Average Remaining Useful Life December 31, 2020 December 31, 2019 Leased wireless devices, gross 8 months $ 6,989 $ 1,139 Accumulated depreciation (2,170) (407) Leased wireless devices, net $ 4,819 $ 732 For equipment revenues from the lease of mobile communication devices, see Note 10 - Revenue from Contracts with Customers . Future minimum payments expected to be received over the lease term related to leased wireless devices, which exclude optional residual buy-out amounts at the end of the lease term, are summarized below: (in millions) Expected Payments Twelve Months Ending December 31, 2021 $ 1,687 2022 92 Total $ 1,779
Leases	Lessee Through the Merger, we acquired leases of real property, including cell sites, switch sites, dark fiber, retail stores and office facilities and recorded lease liabilities and associated right-of-use assets based on the discounted lease payments. Lease terms that are favorable or unfavorable to market terms were recorded as an adjustment to lease right-of-use assets on our Consolidated Balance Sheets. Favorable and unfavorable leases are amortized on a straight-line basis over the associated remaining lease term. On September 14, 2020, T-Mobile and American Tower Corporation (“American Tower”) entered into a lease agreement (the “American Tower Lease Agreement”) that will enable us to lease American Tower towers through April 2035. The American Tower Lease Agreement extended the term and modified the rental payments for approximately 20,729 American Tower towers currently leased by us. As a result of this modification, we remeasured the associated right-of-use assets and lease liabilities resulting in an increase of $11.0 billion to each on the effective date of the modification. The components of lease expense were as follows: Year Ended December 31, (in millions) 2020 2019 Operating lease expense $ 4,438 $ 2,558 Financing lease expense: Amortization of right-of-use assets 681 523 Interest on lease liabilities 81 82 Total financing lease expense 762 605 Variable lease expense 328 243 Total lease expense $ 5,528 $ 3,406 Information relating to the lease term and discount rate is as follows: Year Ended December 31, 2020 2019 Weighted Average Remaining Lease Term (Years) Operating leases 10 6 Financing leases 3 3 Weighted Average Discount Rate Operating leases 3.9 % 4.8 % Financing leases 3.3 % 4.0 % Maturities of lease liabilities as of December 31, 2020, were as follows: (in millions) Operating Leases Finance Leases Twelve Months Ending December 31, 2021 $ 4,903 $ 1,121 2022 4,354 795 2023 3,759 422 2024 3,339 137 2025 2,807 92 Thereafter 18,940 61 Total lease payments 38,102 2,628 Less: imputed interest 7,515 121 Total $ 30,587 $ 2,507 Interest payments for financing leases were $79 million and $82 million for the years ended December 31, 2020 and 2019, respectively. As of December 31, 2020, we have additional operating leases for cell sites and commercial properties that have not yet commenced with future lease payments of approximately $227 million. As of December 31, 2020, we were contingently liable for future ground lease payments related to certain tower obligations. These contingent obligations are not included in the above table as the amounts owed are contractually owed by Crown Castle International Corp. based on the subleasing arrangement. See Note 9 - Tower Obligations for further information. Lessor Through the Merger, we acquired leased wireless devices with a fair value of $5.8 billion as of April 1, 2020. The components of leased wireless devices under our Leasing Programs were as follows: (in millions) Average Remaining Useful Life December 31, 2020 December 31, 2019 Leased wireless devices, gross 8 months $ 6,989 $ 1,139 Accumulated depreciation (2,170) (407) Leased wireless devices, net $ 4,819 $ 732 For equipment revenues from the lease of mobile communication devices, see Note 10 - Revenue from Contracts with Customers . Future minimum payments expected to be received over the lease term related to leased wireless devices, which exclude optional residual buy-out amounts at the end of the lease term, are summarized below: (in millions) Expected Payments Twelve Months Ending December 31, 2021 $ 1,687 2022 92 Total $ 1,779

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 18 – Commitments and Contingencies Purchase Commitments We have commitments for non-dedicated transportation lines with varying expiration terms that generally extend through 2029. In addition, we have commitments to purchase wireless devices, network services, equipment, software, marketing sponsorship agreements and other items in the ordinary course of business, with various terms through 2043. Our purchase commitments, including purchase commitments assumed through the Merger, are approximately $5.0 billion for the year ending December 31, 2021, $4.5 billion in total for the years ending December 31, 2022 and 2023, $2.4 billion in total for the years ending December 31, 2024 and 2025 and $1.7 billion in total for the years thereafter. These amounts are not reflective of our entire anticipated purchases under the related agreements but are determined based on the non-cancelable quantities or termination amounts to which we are contractually obligated. Spectrum Leases In connection with the Merger, we assumed certain spectrum lease contracts from Sprint that include service obligations to the lessors. Certain of the spectrum leases provide for minimum lease payments, additional charges, renewal options and escalation clauses. Leased spectrum agreements have varying expiration terms that generally extend through 2050. We expect that all renewal periods in our spectrum leases will be exercised by us. Our spectrum lease and service credit commitments, including renewal periods, are approximately $338 million for the year ending December 31, 2021, $675 million in total for the years ending December 31, 2022 and 2023, $594 million in total for the years ending December 31, 2024 and 2025 and $5.1 billion in total for the years thereafter. We accrue a monthly obligation for the services and equipment based on the total estimated available service credits divided by the term of the lease. The obligation is reduced by services provided and as actual invoices are presented and paid to the lessors. The maximum remaining service commitment on December 31, 2020 was $92 million and is expected to be incurred over the term of the related lease agreements, which generally range from 15 to 30 years. Merger Commitments In connection with the regulatory proceedings and approvals of the Transactions, we have commitments and other obligations to various state and federal agencies and certain nongovernmental organizations, including pursuant to the Consent Decree agreed to by us, DT, Sprint, SoftBank and DISH and entered by the U.S. District Court for the District of Columbia, and the FCC’s memorandum opinion and order approving our applications for approval of the Merger. These commitments and obligations include, among other things, extensive 5G network build-out commitments, obligations to deliver high-speed wireless services to the vast majority of Americans, including Americans residing in rural areas, and the marketing of an in-home broadband product where spectrum capacity is available. Other commitments relate to national security, pricing, service, employment and support of diversity initiatives. Many of the commitments specify time frames for compliance. Failure to fulfill our obligations and commitments in a timely manner could result in substantial fines, penalties, or other legal and administrative actions. We expect that our monetary commitments associated with these matters are approximately $23 million for the year ended December 31, 2021, $37 million in total for the years ended December 31, 2022 and 2023 and $13 million in total for the years ended December 31, 2024 and 2025. These amounts do not represent our entire anticipated costs to achieve specified network coverage and performance requirements, employment targets or commitments to provide access to affordable rate plans, but represent only those amounts for which we are required to make a specified payment in connection with our commitments or settlements. Contingencies and Litigation Litigation Matters We are involved in various lawsuits and disputes, claims, government agency investigations and enforcement actions, and other proceedings (“Litigation Matters”) that arise in the ordinary course of business, which include claims of patent infringement (most of which are asserted by non-practicing entities primarily seeking monetary damages), class actions, and proceedings to enforce FCC rules and regulations. Those Litigation Matters are at various stages, and some of them may proceed to trial, arbitration, hearing, or other adjudication that could result in fines, penalties, or awards of monetary or injunctive relief in the coming 12 months if they are not otherwise resolved. We have established an accrual with respect to certain of these matters, where appropriate, which is reflected in the consolidated financial statements but that is not considered to be, individually or in the aggregate, material. An accrual is established when we believe it is both probable that a loss has been incurred and an amount can be reasonably estimated. For other matters, where we have not determined that a loss is probable or because the amount of loss cannot be reasonably estimated, we have not recorded an accrual due to various factors typical in contested proceedings, including, but not limited to, uncertainty concerning legal theories and their resolution by courts or regulators, uncertain damage theories and demands, and a less than fully developed factual record. We do not expect that the ultimate resolution of these Litigation Matters, individually or in the aggregate, will have a material adverse effect on our financial position, but we note that an unfavorable outcome of some or all of the specific matters identified below could have a material adverse impact on results of operations or cash flows for a particular period. This assessment is based on our current understanding of relevant facts and circumstances. As such, our view of these matters is subject to inherent uncertainties and may change in the future. On February 28, 2020, we received a Notice of Apparent Liability for Forfeiture and Admonishment from the FCC, which proposed a penalty against us for allegedly violating section 222 of the Communications Act and the FCC’s regulations governing the privacy of customer information. We recorded an accrual for an estimated payment amount as of December 31, 2020, which was included in Accounts payable and accrued liabilities in our Consolidated Balance Sheets. On April 1, 2020, in connection with the closing of the Merger, we assumed the contingencies and litigation matters of Sprint. Those matters include a wide variety of disputes, claims, government agency investigations and enforcement actions, and other proceedings. These matters include, among other things, certain ongoing FCC and state government agency investigations into Sprint’s Lifeline program. In September 2019, Sprint notified the FCC that it had claimed monthly subsidies for serving subscribers even though these subscribers may not have met usage requirements under Sprint's usage policy for the Lifeline program, due to an inadvertent coding issue in the system used to identify qualifying subscriber usage that occurred in July 2017 while the system was being updated. Sprint has made a number of payments to reimburse the federal government and certain states for excess subsidy payments. Resolution of these matters could require making additional reimbursements and paying additional fines and penalties. In November 2020, we entered into a consent decree with the FCC to resolve certain of these Lifeline matters, which resulted in a payment of $200 million by SoftBank. We note that pursuant to Amendment No. 2 to the Business Combination Agreement, SoftBank agreed to indemnify us against certain specified matters and losses, including those relating to these Lifeline matters. As of December 31, 2020, we have recorded a contingent liability and an offsetting indemnification asset for the expected reimbursement by SoftBank for certain Lifeline matters which have not been resolved. We expect that any additional liabilities related to these indemnified matters would be indemnified and reimbursed by SoftBank. See Note 2 - Business Combination for further information.

Restructuring Costs

Restructuring Costs	12 Months Ended
	Dec. 31, 2020
Restructuring and Related Activities [Abstract]
Restructuring Costs	Note 19 – Restructuring Costs Upon close of the Merger, we began implementing restructuring initiatives to realize cost efficiencies and reduce redundancies. The major activities associated with the restructuring initiatives to date include contract termination costs associated with the rationalization of retail stores, distribution channels, duplicative backhaul services and other agreements, severance costs associated with the integration of redundant processes and functions and the decommissioning of network infrastructure including cell sites and equipment to achieve synergies in network costs. The following table summarizes the expenses incurred in connection with our restructuring initiatives: (in millions) Year Ended Contract termination costs $ 178 Severance costs 385 Network decommissioning 497 Total restructuring plan expenses $ 1,060 The expenses associated with the restructuring initiatives are included in Costs of services and Selling, general and administrative in our Consolidated Statements of Comprehensive Income. No expenses were incurred related to our restructuring initiatives for the year ended December 31, 2019. Our restructuring initiatives also include the acceleration or termination of certain of our operating and financing leases for cell sites, switch sites, retail stores, network equipment and office facilities. Incremental expenses associated with accelerating amortization of the right-of-use assets on lease contracts were $153 million for the year ended December 31, 2020 and are included within Costs of services and Selling, general and administrative in our Consolidated Statements of Comprehensive Income. The changes in the liabilities associated with our restructuring initiatives, including expenses incurred and cash payments, are as follows: (in millions) April 1, Expenses Incurred Cash Payments Adjustments for Non-Cash Items (1) December 31, Contract termination costs $ — $ 178 $ (96) $ (1) $ 81 Severance costs — 385 (239) (94) 52 Network decommissioning — 497 (403) (64) 30 Total $ — $ 1,060 $ (738) $ (159) $ 163 (1) Non-cash items consists of non-cash stock-based compensation included within Severance costs and the write-off of assets within Network decommissioning. The liabilities accrued in connection with our restructuring initiatives are presented in Accounts payable and accrued liabilities in our Consolidated Balance Sheets. Our restructuring activities are expected to occur over the next three years with substantially all costs incurred by the end of fiscal year 2023. We are evaluating additional restructuring initiatives, which are dependent on consultations and negotiation with certain counterparties and the expected impact on our business operations, which could affect the amount or timing of the restructuring costs and related payments.

Additional Financial Informatio

Additional Financial Information	12 Months Ended
	Dec. 31, 2020
Supplemental Financial Statement Elements [Abstract]
Additional Financial Information	Note 20 – Additional Financial Information Accounts Payable and Accrued Liabilities Accounts payable and accrued liabilities are summarized as follows: (in millions) December 31, December 31, Accounts payable $ 5,564 $ 4,322 Payroll and related benefits 1,163 802 Property and other taxes, including payroll 1,540 682 Interest 771 227 Commissions 399 251 Toll and interconnect 217 156 Advertising 135 127 Other 407 179 Accounts payable and accrued liabilities $ 10,196 $ 6,746 Book overdrafts included in accounts payable and accrued liabilities were $628 million and $463 million as of December 31, 2020 and 2019, respectively. Related Party Transactions Deutsche Telekom We have related party transactions associated with DT or its affiliates in the ordinary course of business, which are included in the consolidated financial statements. On April 1, 2020, in connection with the closing of the Merger, we: • Repaid our $4.0 billion Incremental Term Loan Facility with DT, consisting of a $2.0 billion Incremental Term Loan Facility due 2022 and a $2.0 billion Incremental Term Loan Facility due 2024; • Terminated our revolving credit facility with DT; • Repurchased from DT $4.0 billion of indebtedness to affiliates, consisting of $2.0 billion of 5.300% Senior Notes due 2021 and $2.0 billion of 6.000% Senior Notes due 2024; • Amended the $1.25 billion of 5.125% Senior Notes due 2025 and $1.25 billion of 5.375% Senior Notes due 2027, which represent indebtedness to affiliates, to change the maturity dates thereof to April 15, 2021 and April 15, 2022, respectively (the “2025 and 2027 Amendments”); and • Made an additional payment for requisite consents to DT of $13 million. These payments were recognized as a reduction to Long-term debt to affiliates in our Consolidated Balance Sheets. On July 4, 2020, we redeemed $1.25 billion aggregate principal amount of our 5.125% Senior Notes to affiliates due 2021. Amounts associated with the debt owed to DT are reflected as Short-term debt to affiliates and Long-term debt to affiliates in our Consolidated Balance Sheets. Interest related to this debt is reflected as Interest expense to affiliates in our Consolidated Statements of Comprehensive Income. The following table summarizes the impact of significant transactions with DT or its affiliates included in Operating expenses in the Consolidated Statements of Comprehensive Income: Year Ended December 31, (in millions) 2020 2019 2018 Discount related to roaming expenses $ (5) $ (9) $ — Fees incurred for use of the T-Mobile brand 83 88 84 International long distance agreement 47 39 36 We have an agreement with DT in which we receive reimbursement of certain administrative expenses, which was $6 million for the year ended December 31, 2020 and $11 million for each of the years ended December 31, 2019 and 2018. Amounts due from and to DT related to these agreements are included in the Consolidated Balance Sheets as “Accounts Receivables from affiliates” and “Payables to affiliates,” respectively. SoftBank On June 22, 2020, we entered into a Master Framework Agreement and related transactions with SoftBank related to the SoftBank Monetization as described in Note 14 - SoftBank Equity Transaction . On July 27, 2020, in connection with the SoftBank Monetization, the Rights Offering exercise period closed, and on August 3, 2020, the Rights Offering closed, resulting in the sale of 19,750,000 shares of our common stock. On August 3, 2020, upon completion of the SoftBank Monetization, DT and SoftBank held, directly or indirectly, approximately 43.4% and 8.6%, respectively, of the outstanding T-Mobile common stock, with the remaining approximately 48.0% of the outstanding T-Mobile common stock held by other stockholders. As a result of the Proxy Agreements, DT has voting control as of August 3, 2020 over approximately 52.4% of the outstanding T-Mobile common stock. In addition, as provided for in the Master Framework Agreement, DT also holds certain call options over approximately 101.5 million shares of our common stock held by SBGC. On October 6, 2020, we assigned our rights under the T-Mobile Fixed-Price Call Option to DT and DT terminated its right to purchase shares from us under the DT Fixed-Price Call Option, resulting in derecognition of the related der ivative asset and liability in equal and offsetting amounts such that there was no net impact to our Consolidated Statements of Comprehensive Income . Brightstar We had arrangements with Brightstar, a subsidiary of SoftBank, whereby Brightstar provided supply chain and inventory management services to us in our indirect channels. We have terminated or restructured most of our arrangements with Brightstar, except for reverse logistics and trade-in services. Revenue resulting from sale of devices distributed by Brightstar is generally recognized when sold to an end customer (commonly referred to as recognized on a sell-through basis). Amounts included in our consolidated financial statements associated with these supply chain and inventory management arrangements with Brightstar were not material. For more information regarding our related party transactions with SoftBank, see Note 2 - Business Combination and Note 14 - SoftBank Equity Transaction of the Notes to the Consolidated Financial Statements. Supplemental Consolidated Statements of Cash Flows Information The following table summarizes T-Mobile’s supplemental cash flow information: Year Ended December 31, (in millions) 2020 2019 2018 Interest payments, net of amounts capitalized $ 2,733 $ 1,128 $ 1,525 Operating lease payments 4,619 2,783 — Income tax payments 218 88 51 Non-cash investing and financing activities Non-cash beneficial interest obtained in exchange for securitized receivables 6,194 6,509 4,972 Non-cash consideration for the acquisition of Sprint 33,533 — — Change in accounts payable and accrued liabilities for purchases of property and equipment 589 (935) 65 Leased devices transferred from inventory to property and equipment 2,795 1,006 1,011 Returned leased devices transferred from property and equipment to inventory (1,460) (267) (326) Short-term debt assumed for financing of property and equipment 38 800 291 Operating lease right-of-use assets obtained in exchange for lease obligations 14,129 3,621 — Financing lease right-of-use assets obtained in exchange for lease obligations 1,273 1,041 885

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Note 21 – Subsequent Events Subsequent to December 31, 2020, on January 14, 2021, we issued an aggregate of $3.0 billion in Senior Notes. A portion of the senior secured term loan commitments were reduced by an amount equal to the aggregate gross proceeds of the Senior Notes, which reduced the commitment to $2.0 billion. See Note 8 – Debt for further information. Subsequent to December 31, 2020, on February 1, 2021, the valuation process was complete with respect to Shentel’s wireless telecommunication assets used to provide services pursuant to the Management Agreement, for which we previously exercised an option to purchase. The parties are negotiating the remaining outstanding terms of a definitive agreement to govern the purchase of Shentel’s wireless telecommunication assets and expect the transaction to close in the second quarter of 2021 after satisfying customary conditions to closing. The base purchase price of the wireless telecommunication assets is $1.9 billion, subject to certain other purchase price adjustments prescribed by the Management Agreement and such additional purchase price adjustments agreed by the parties. See Note 2 – Business Combination

Quarterly Financial Information

Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information [Abstract]
Quarterly Financial Information (Unaudited)	Supplementary Data Quarterly Financial Information (Unaudited) The following table includes the impact of the Merger on a prospective basis from the Merger close date of April 1, 2020. Historical results have not been restated and reflect standalone T-Mobile. (in millions, except share and per share amounts) First Quarter Second Quarter Third Quarter Fourth Quarter Full Year 2020 Total revenues $ 11,113 $ 17,671 $ 19,272 $ 20,341 $ 68,397 Operating income 1,539 820 2,565 1,712 6,636 Income (loss) from continuing operations 951 (210) 1,253 750 2,744 Income from discontinued operations, net of tax — 320 — — 320 Net income 951 110 1,253 750 3,064 Earnings per share Basic earnings per share Continuing operations $ 1.11 $ (0.17) $ 1.01 $ 0.60 $ 2.40 Discontinued operations — 0.26 — — 0.28 Basic $ 1.11 $ 0.09 $ 1.01 $ 0.60 $ 2.68 Diluted earnings per share Continuing operations $ 1.10 $ (0.17) $ 1.00 $ 0.60 $ 2.37 Discontinued operations — 0.26 — — 0.28 Diluted $ 1.10 $ 0.09 $ 1.00 $ 0.60 $ 2.65 Weighted average shares outstanding Basic 858,148,284 1,236,528,444 1,238,450,665 1,241,578,615 1,144,206,326 Diluted 865,998,532 1,236,528,444 1,249,798,740 1,251,566,899 1,154,749,428 2019 Total revenues $ 11,080 $ 10,979 $ 11,061 $ 11,878 $ 44,998 Operating income 1,476 1,541 1,471 1,234 5,722 Income from continuing operations 908 939 870 751 3,468 Net income 908 939 870 751 3,468 Earnings per share Basic $ 1.07 $ 1.10 $ 1.02 $ 0.88 $ 4.06 Diluted $ 1.06 $ 1.09 $ 1.01 $ 0.87 $ 4.02 Weighted average shares outstanding Basic 851,223,498 854,368,443 854,578,241 856,294,467 854,143,751 Diluted 858,643,481 860,135,593 862,690,751 864,158,739 863,433,511 Earnings per share is computed independently for each quarter and the sum of the quarters may not equal earnings per share for the full year. There were no discontinued operations for the year ended December 31, 2019.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidation	The consolidated financial statements include the balances and results of operations of T-Mobile and our consolidated subsidiaries. We consolidate majority-owned subsidiaries over which we exercise control, as well as variable interest entities (“VIE”) where we are deemed to be the primary beneficiary and VIEs, which cannot be deconsolidated, such as those related to Tower obligations. Intercompany transactions and balances have been eliminated in consolidation. We operate as a single operating segment.
Basis of Accounting	The preparation of financial statements in conformity with U.S. generally accepted accounting principles (“GAAP”) requires our management to make estimates and assumptions which affect the financial statements and accompanying notes.
Use of Estimates	Estimates are based on historical experience, where applicable, and other assumptions which our management believes are reasonable under the circumstances, including but not limited to the valuation of assets acquired and liabilities assumed through the Merger with Sprint and the potential impacts arising from the COVID-19 pandemic (the “Pandemic”). These estimates are inherently subject to judgment and actual results could differ from those estimates.
Reclassification	Certain prior year amounts have been reclassified to conform to the current year's presentation.
Business Combination	Business Combination Assets acquired and liabilities assumed as part of a business combination are generally recorded at their fair value at the date of acquisition. The excess of purchase price over the fair value of assets acquired and liabilities assumed is recorded as goodwill. Determining fair value of identifiable assets, particularly intangibles, and liabilities acquired requires management to make estimates, which are based on all available information and in some cases assumptions with respect to the timing and amount of
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents consist of highly liquid money market funds and U.S. Treasury securities with remaining maturities of three months or less at the date of purchase.
Receivables and Allowance for Credit Losses	Receivables and Allowance for Credit Losses Accounts Receivable Accounts receivable consists primarily of amounts currently due from customers (e.g., for wireless services and monthly device lease payments), device insurance administrators, wholesale partners, other carriers and third-party retail channels. Accounts receivable are presented in our Consolidated Balance Sheets at the amortized cost basis (i.e., the receivables’ outstanding principal balance adjusted for any write-offs), net of the allowance for expected credit losses. We have an arrangement to sell certain of our customer service accounts receivable on a revolving basis, which are treated as sales of financial assets. Equipment Installment Plan Receivables We offer certain retail customers the option to pay for their devices and other purchases in installments, generally over a period of 24 months using an EIP. EIP receivables are presented in our Consolidated Balance Sheets at the amortized cost basis (i.e., the receivables’ unpaid principal balance adjusted for any write-offs and unamortized discounts), net of the allowance for expected credit losses. At the time of an installment sale, we impute a discount for interest if the term exceeds 12 months as there is no stated rate of interest on the receivables. The receivables are recorded at their present value, which is determined by discounting expected future cash payments at the imputed interest rate. This adjustment results in a discount or reduction in transaction price which is allocated to the performance obligations and reduces Service revenues and Equipment revenues in our Consolidated Statements of Comprehensive Income. The imputed discount rate is the current market interest rate and is predominately comprised of the estimated credit risk underlying the EIP receivable, reflecting the estimated credit worthiness of the customer. The imputed discount on receivables is amortized over the financed installment term using the effective interest method and recognized as Other revenues in our Consolidated Statements of Comprehensive Income. The current portion of the EIP receivables is included in Equipment installment plan receivables, net and the long-term portion of the EIP receivables is included in Equipment installment plan receivables due after one year, net in our Consolidated Balance Sheets. We have an arrangement to sell certain EIP receivables on a revolving basis, which are treated as sales of financial assets. Allowance for Credit Losses We maintain an allowance for expected credit losses and determine its appropriateness through an established process that assesses the lifetime credit losses that we expect to incur related to our receivable portfolio. Our process involves procedures to appropriately consider the unique risk characteristics of our accounts receivable and EIP receivable portfolio segments. For each portfolio segment, losses are estimated collectively for groups of receivables with similar characteristics. Our allowance levels are influenced by receivable volumes, receivable delinquency status, historical loss experience and other conditions that affect loss expectations, such as changes in credit and collections policies and forecasts of macro-economic conditions. While we attribute portions of the allowance to our respective accounts receivable and EIP portfolio segments, the entire allowance is available to credit losses related to the total receivable portfolio. We consider a receivable past due and delinquent when a customer has not paid us by the contractually specified payment due date. Account balances are written off against the allowance for credit losses if collection efforts are unsuccessful and the receivable balance is deemed uncollectible (customer default), based on factors such as customer credit ratings as well as the length of time the amounts are past due. If there is a deterioration of our customers’ financial condition or if future actual default rates on receivables in general differ from those currently anticipated, we will adjust our allowance for credit losses accordingly, which may materially affect our financial results in the period the adjustments are made.
Inventories	Inventories Inventories consist primarily of wireless devices and accessories, which are valued at the lower of cost or net realizable value. Cost is determined using standard cost which approximates average cost. Shipping and handling costs paid to wireless device and accessories vendors as well as costs to refurbish used devices are included in the standard cost of inventory. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of disposal and transportation. We record inventory write-downs to net realizable value for obsolete and slow-moving items based on inventory turnover trends and historical experience.
Deferred Purchase Price Assets	Deferred Purchase Price Assets In connection with the sales of certain service and EIP accounts receivable pursuant to the sale arrangements, we have deferred purchase price assets measured at fair value that are based on a discounted cash flow model using unobservable Level 3 inputs, including estimated customer default rates and credit worthiness. See Note 4 – Sales of Certain Receivables
Long-Lived Assets and Property and Equipment	Long-Lived Assets Long-lived assets include assets that do not have indefinite lives, such as property and equipment and other intangible assets. Substantially all of our long-lived assets are located in the U.S., including Puerto Rico and the U.S. Virgin Islands. We assess potential impairments to our long-lived assets when events or changes in circumstances indicate the carrying amount of the asset may not be recoverable. If any indicators of impairment are present, we test recoverability. The carrying value of a long-lived asset or asset group is not recoverable if it exceeds the sum of the undiscounted cash flows expected to be generated from the use and eventual disposition of the asset or asset group. If the undiscounted cash flows do not exceed the asset or asset group’s carrying amount, then an impairment loss is recorded, measured as the amount by which the carrying amount of a long-lived asset or asset group exceeds its fair value. Property and Equipment Property and equipment consists of buildings and equipment, wireless communications systems, leasehold improvements, capitalized software, leased wireless devices and construction in progress. Buildings and equipment include certain network server equipment. Wireless communications systems include assets to operate our wireless network and IT data centers, including tower assets and leasehold improvements and assets related to the liability for the retirement of long-lived assets. Leasehold improvements include asset improvements other than those related to the wireless network. Property and equipment are recorded at cost less accumulated depreciation and impairments, if any, in Property and equipment, net on our Consolidated Balance Sheets. We generally depreciate property and equipment over the period the property and equipment provide economic benefit using the straight-line method. Depreciable life studies are performed periodically to confirm the appropriateness of depreciable lives for certain categories of property and equipment. These studies take into account actual usage, physical wear and tear, replacement history and assumptions about technology evolution. When these factors indicate the useful life of an asset is different from the previous assessment, the remaining book value is depreciated prospectively over the adjusted remaining estimated useful life. Leasehold improvements are depreciated over the shorter of their estimated useful lives or the related lease term. Costs of major replacements and improvements are capitalized. Repair and maintenance expenditures which do not enhance or extend the asset’s useful life are charged to operating expenses as incurred. Construction costs, labor and overhead incurred in the expansion or enhancement of our wireless network are capitalized. Capitalization commences with pre-construction period administrative and technical activities, which include obtaining zoning approvals and building permits, and ceases at the point at which the asset is ready for its intended use. We capitalize interest associated with the acquisition or construction of certain property and equipment. Capitalized interest is reported as a reduction in interest expense and depreciated over the useful life of the related assets.
Asset Retirement Obligations	We record an asset retirement obligation for the estimated fair value of legal obligations associated with the retirement of tangible long-lived assets and a corresponding increase in the carrying amount of the related asset in the period in which the obligation is incurred. In periods subsequent to initial measurement, we recognize changes in the liability resulting from the passage of time and revisions to either the timing or the amount of the original estimate. Over time, the liability is accreted to its present value and the capitalized cost is depreciated over the estimated useful life of the asset. Our obligations relate primarily to certain legal obligations to remediate leased property on which our network infrastructure and administrative assets are located.
Software Capitalization	We capitalize certain costs incurred in connection with developing or acquiring internal use software. Capitalization of software costs commences once the final selection of the specific software solution has been made and management authorizes and commits to funding the software project and ceases once the project is ready for its intended use. Capitalized software costs are included in Property and equipment, net in our Consolidated Balance Sheets and are amortized on a straight-line basis over the estimated useful life of the asset. Costs incurred during the preliminary project stage, as well as maintenance and training costs, are expensed as incurred.
Device Leases	Device Leases Through the Merger, we acquired device lease contracts in which Sprint is the lessor (the “Sprint Flex Lease Program”), substantially all of which are classified as operating leases, as well as the associated fixed assets (i.e., the leased devices). These leased devices were recorded as fixed assets at their acquisition date fair value and presented within Property and equipment, net on our Consolidated Balance Sheets. Our leasing programs (“Leasing Programs”), which include JUMP! On Demand and the Sprint Flex Lease Program acquired through the Merger, allow customers to lease a device (handset or tablet) over a period of, generally, 18 months and upgrade it for a new device when eligibility requirements are met. We depreciate leased devices to their estimated residual value, on a group basis, using the straight-line method over the estimated useful life of the device. The estimated useful life reflects the period for which we estimate the group of leased devices will provide utility to us, which may be longer than the initial lease term based on customer options in the Sprint Flex Lease program to renew the lease on a month-to-month basis after the initial lease term concludes. In determining the estimated useful life, we consider the lease term (e.g., 18 months and month-to-month renewal options for the Sprint Flex Lease Program), trade-in activity and write-offs for lost and stolen devices. Lost and stolen devices are incorporated into the estimates of depreciation expense and recognized as an adjustment to accumulated depreciation when the loss event occurs. Our policy of using the group method of depreciation has been applied to acquired leased devices as well as leases originated subsequent to the Merger. Acquired leased devices are grouped based on the age of the device. Revenues associated with the leased wireless devices, net of lease incentives, are generally recognized on a straight-line basis over the lease term. For arrangements in which we are the lessor of wireless devices, we separate lease and non-lease components. Upon device upgrade or at lease end, customers in the JUMP! On Demand lease program must return or purchase their device, and customers in the Sprint Flex Lease Program have the option to return or purchase their device or to renew their lease on a month-to-month basis. The purchase price of the device is established at lease commencement and is based on the type of device leased and any down payment made. The Leasing Programs do not contain any residual value guarantees or variable lease payments, and there are no restrictions or covenants imposed by these leases. Returned devices, including those received upon device upgrade, are transferred from Property and equipment, net to Inventory on our Consolidated Balance Sheets and are valued at the lower of cost or net realizable value, with any write-down recognized as Cost of equipment sales in our Consolidated Statements of Comprehensive Income.
Other Intangible Assets	Other Intangible Assets Intangible assets that do not have indefinite useful lives are amortized over their estimated useful lives. Customer lists and the Sprint trade name are amortized using the sum-of-the-years digits method over the period in which the asset is expected to contribute to future cash flows. The remaining finite-lived intangible assets are amortized using the straight-line method.
Goodwill	Goodwill Goodwill consists of the excess of the purchase price over the fair value of identifiable net assets acquired in a business combination. Goodwill is allocated to our two reporting units, wireless and Layer3.
Spectrum Licenses	Spectrum Licenses Spectrum licenses are carried at costs incurred to acquire the spectrum licenses and the costs to prepare the spectrum licenses for their intended use, such as costs to clear acquired spectrum licenses. The Federal Communications Commission (“FCC”) issues spectrum licenses which provide us with the exclusive right to utilize designated radio frequency spectrum within specific geographic service areas to provide wireless communications services. While spectrum licenses are issued for a fixed period of time, typically for up to 15 years, the FCC has granted license renewals routinely and at a nominal cost. The spectrum licenses held by us expire at various dates. We believe we will be able to meet all requirements necessary to secure renewal of our spectrum licenses at nominal costs. Moreover, we determined there are currently no legal, regulatory, contractual, competitive, economic or other factors that limit the useful lives of our spectrum licenses. Therefore, we determined the spectrum licenses should be treated as indefinite-lived intangible assets. At times, we enter into agreements to sell or exchange spectrum licenses. Upon entering into the arrangement, if the transaction has been deemed to have commercial substance, spectrum licenses are reviewed for impairment. The licenses are transferred at their carrying value, as adjusted for any impairment recognized, to assets held for sale, which is included in Other current assets in our Consolidated Balance Sheets until approval and completion of the exchange or sale. Upon closing of the transaction, spectrum licenses acquired as part of an exchange of nonmonetary assets are recorded at fair value and the difference between the fair value of the spectrum licenses obtained, carrying value of the spectrum licenses transferred and cash paid, if any, is recognized as a Gain (loss) on disposal of spectrum licenses included in Selling, general and administrative expenses in our Consolidated Statements of Comprehensive Income. Our fair value estimates of spectrum licenses are based on information for which there is little or no observable market data. If the transaction lacks commercial substance or the fair value is not measurable, the acquired spectrum licenses are recorded at our carrying value of the spectrum assets transferred or exchanged. Spectrum Leases Through the Merger, the Company acquired lease agreements (the “Agreements”) with various educational and non-profit institutions that provide us with the right to use FCC spectrum licenses (Educational Broadband Services or “EBS spectrum”) in the 2.5 GHz band. In addition to the Agreements with educational institutions and private owners who hold the licenses, the Company also acquired direct ownership of spectrum licenses previously acquired by Sprint through government auctions or other acquisitions. The Agreements with educational and certain non-profit institutions are typically for five Leased FCC spectrum licenses are recorded as executory contracts whereby, as a result of business combination accounting, an intangible asset or liability is recorded reflecting the extent to which contractual terms are favorable or unfavorable to current market rates. These intangible assets or liabilities are amortized over the estimated remaining useful life of the lease agreements. Contractual lease payments are recognized on a straight-line basis over the remaining term of the arrangement, including renewals, and are presented in Costs of services within our Consolidated Statements of Comprehensive Income. The Agreements enhance the overall value of the Company’s owned spectrum licenses as the collective value is higher than the value of individual bands of spectrum within a specific geography. This value is derived from the ability to provide wireless service to customers across large geographic areas and maintain the same or similar wireless connectivity quality. This enhanced value from combining owned and leased spectrum licenses is referred to as an aggregation premium.
Impairment	Impairment We assess the carrying value of our goodwill and other indefinite-lived intangible assets, such as our spectrum licenses, for potential impairment annually as of December 31, or more frequently if events or changes in circumstances indicate such assets might be impaired. When assessing goodwill for impairment, we may elect to first perform a qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. If we do not perform a qualitative assessment, or if the qualitative assessment indicates it is more likely than not that the fair value of the two reporting units, wireless and Layer3, is less than its carrying amount, we perform a quantitative test. We recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized would not exceed the total amount of goodwill allocated to that reporting unit. We test our spectrum licenses for impairment on an aggregate basis, consistent with our management of the overall business at a national level. We may elect to first perform a qualitative assessment to determine whether it is more likely than not that the fair value of an intangible asset is less than its carrying value. If we do not perform the qualitative assessment, or if the qualitative assessment indicates it is more likely than not that the fair value of the intangible asset is less than its carrying amount, we calculate the estimated fair value of the intangible asset. If the estimated fair value of the spectrum licenses is lower than their carrying amount, an impairment loss is recognized for the difference. We estimate fair value using the Greenfield methodology, which is an income approach based on discounted cash flows associated with the intangible asset, to estimate the price at which an orderly transaction to sell the asset would take place between market participants at the measurement date under current market conditions.
Restricted Cash	Restricted CashCertain provisions of our debt agreements require us to maintain specified cash collateral balances. Amounts associated with these balances are considered to be restricted cash and are included within Other assets in our Consolidated Balance Sheets.
Guarantee Liabilities	Guarantee Liabilities We offer a device trade-in program, Just Upgrade My Phone (“JUMP!”), which provides eligible customers a specified-price trade-in right to upgrade their device. Upon enrollment, participating customers must finance the purchase of a device on an EIP and have a qualifying T-Mobile monthly wireless service plan. Upon a qualifying JUMP! program upgrade, the customer’s remaining EIP balance is settled provided they trade-in their eligible used device in good working condition and purchase a new device from us on a new EIP. For customers who enroll in JUMP!, we recognize a liability and reduce revenue for the portion of revenue which represents the estimated fair value of the specified-price trade-in right guarantee. The guarantee liability is valued based on various economic and customer behavioral assumptions, which requires judgment, including estimating the customer's remaining EIP balance at trade-in, the expected fair value of the used device at trade-in, and the probability and timing of trade-in. When customers upgrade their device, the difference between the EIP balance credit to the customer and the fair value of the returned device is recorded against the guarantee liabilities. All assumptions are reviewed periodically.
Fair Value Measurements	Fair Value Measurements We carry certain assets and liabilities at fair value. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The three-tier hierarchy for inputs used in measuring fair value, which prioritizes the inputs based on the observability as of the measurement date, is as follows: Level 1 Quoted prices in active markets for identical assets or liabilities; Level 2 Observable inputs other than the quoted prices in active markets for identical assets and liabilities; and Level 3 Unobservable inputs for which there is little or no market data, which require us to develop assumptions of what market participants would use in pricing the asset or liability. Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the placement of assets and liabilities being measured within the fair value hierarchy. The carrying values of Cash and cash equivalents, Accounts receivable, Accounts receivable from affiliates, Accounts payable and accrued liabilities and borrowings under our vendor financing arrangements approximate fair value due to the short-term maturities of these instruments. The carrying values of EIP receivables approximate fair value as the receivables are recorded at their present value using an imputed interest rate. With the exception of certain long-term fixed-rate debt, there were no financial instruments with a carrying value materially different from their fair value. See Note 7 - Fair Value Measurements for a comparison of the carrying values and fair values of our short-term and long-term debt.
Derivative Financial Instruments	Derivative Financial Instruments Derivative financial instruments are recognized as either assets or liabilities and are measured at fair value. We do not use derivatives for trading or speculative purposes. For derivative instruments designated as cash flow hedges associated with forecasted debt issuances, changes in fair value are reported as a component of Accumulated other comprehensive loss until reclassified into Interest expense in the same period the hedged transaction affects earnings, generally over the life of the related debt. Unrealized gains on derivatives designated in qualifying cash flow hedge relationships are recorded at fair value as assets, and unrealized losses are recorded at fair value as liabilities.
Revenue Recognition	Revenue Recognition (Effective January 1, 2018) We primarily generate our revenue from providing wireless services to customers and selling or leasing devices and accessories. Our contracts with customers may involve multiple performance obligations, which include wireless services, wireless devices or a combination thereof, and we allocate the transaction price between each performance obligation based on its relative standalone selling price. Significant Judgments The most significant judgments affecting the amount and timing of revenue from contracts with our customers include the following items: • Revenue for service contracts that we assess are not probable of collection is not recognized until the contract is completed or terminated and cash is received. Collectibility is re-assessed when there is a significant change in facts or circumstances. Our assessment of collectibility considers whether we may limit our exposure to credit risk through our right to stop transferring additional service in the event the customer is delinquent as well as certain contract terms such as down payments that reduce our exposure to credit risk. Customer credit behavior is inherently uncertain. See “Receivables and Allowance for Credit Losses” above, for additional discussion on how we assess credit risk. • Promotional EIP bill credits offered to a customer on an equipment sale that are paid over time and are contingent on the customer maintaining a service contract may result in an extended service contract based on whether a substantive penalty is deemed to exist. Determining whether contingent EIP bill credits result in a substantive termination penalty may require significant judgment. • The identification of distinct performance obligations within our service plans may require significant judgment. • Revenue is recorded net of costs paid to another party for performance obligations where we arrange for the other party to transfer goods or services to the customer (i.e., when we are acting as an agent). For example, performance obligations relating to services provided by third-party content providers where we neither control a right to the content provider’s service nor control the underlying service itself are presented net because we are acting as an agent. The determination of whether we control the underlying service or right to the service prior to our transfer to the customer requires, at times, significant judgment. • Our products are generally sold with a right of return, which is accounted for as variable consideration when estimating the amount of revenue to recognize. Device return levels are estimated based on the expected value method as there are a large number of contracts with similar characteristics and the outcome of each contract is independent of the others. Historical return rate experience is a significant input to our expected value methodology. • Sales of equipment to indirect dealers who have been identified as our customer (referred to as the sell-in model) often include credits subsequently paid to the dealer as a reimbursement for any discount promotions offered to the end consumer. These credits (payments to a customer, the dealer) are accounted for as variable consideration when estimating the amount of revenue to recognize from the sales of equipment to indirect dealers and are estimated based on historical experience and other factors, such as expected promotional activity. • The determination of the standalone selling price for contracts that involve more than one performance obligation may require significant judgment, such as when the selling price of a good or service is not readily observable. Wireless Services Revenue We generate our wireless services revenues from providing access to, and usage of, our wireless communications network. Service revenues also include revenues earned for providing premium services to customers, such as device insurance services. Service contracts are billed monthly either in advance or arrears, or are prepaid. Generally, service revenue is recognized as we satisfy our performance obligation to transfer service to our customers. We typically satisfy our stand-ready performance obligations, including unlimited wireless services, evenly over the contract term. For usage-based and prepaid wireless services, we satisfy our performance obligations when services are rendered. Consideration payable to a customer is treated as a reduction of the total transaction price, unless the payment is in exchange for a distinct good or service, such as certain commissions paid to dealers, in which case the payment is treated as a purchase of that distinct good or service. Federal Universal Service Fund (“USF”) and other fees are assessed by various governmental authorities in connection with the services we provide to our customers and are included in Cost of services. When we separately bill and collect these regulatory fees from customers, they are recorded gross in Total service revenues in our Consolidated Statements of Comprehensive Income. For the years ended December 31, 2020, 2019 and 2018, we recorded approximately $267 million, $93 million and $161 million, respectively, of USF fees on a gross basis. We have made an accounting policy election to exclude from the measurement of the transaction price all taxes assessed by a governmental authority that are both imposed on and concurrent with a specific revenue-producing transaction and collected by us from a customer (e.g., sales, use, value added, and some excise taxes). Wireline Revenue Performance obligations related to our Wireline customers include the provision of domestic and international data communications services, generally to complement business wireless customers. Wireline revenues are included within Roaming and other service revenues in our Consolidated Statements of Comprehensive Income. Equipment Revenues We generate equipment revenues from the sale or lease of mobile communication devices and accessories. For performance obligations related to equipment contracts, we typically transfer control at a point in time when the device or accessory is delivered to, and accepted by, the customer or dealer. We have elected to account for shipping and handling activities that occur after control of the related good transfers as fulfillment activities instead of assessing such activities as performance obligations. We estimate variable consideration (e.g., device returns or certain payments to indirect dealers) primarily based on historical experience. Equipment sales not probable of collection are generally recorded as payments are received. Our assessment of collectibility considers contract terms such as down payments that reduce our exposure to credit risk. We offer certain customers the option to pay for devices and accessories in installments using an EIP. Generally, we recognize as a reduction of the total transaction price the effects of a financing component in contracts where customers purchase their devices and accessories on an EIP with a term of more than one year, including those financing components that are not considered to be significant to the contract. However, we have elected the practical expedient to not recognize the effects of a significant financing component for contracts where we expect, at contract inception, that the period between the transfer of a performance obligation to a customer and the customer’s payment for that performance obligation will be one year or less. In addition, for customers who enroll in our JUMP! program, we recognize a liability based on the estimated fair value of the specified-price trade-in right guarantee. The fair value of the guarantee is deducted from the transaction price and the remaining transaction price is allocated to other elements of the contract, including service and equipment performance obligations. See “Guarantee Liabilities” above for further information. JUMP! On Demand allows customers to lease a device over a period of up to 18 months and upgrade it for a new device up to one time per month. To date, substantially all of our leased wireless devices are accounted for as operating leases and estimated contract consideration is allocated between lease and non-lease elements (such as service and equipment performance obligations) based on the relative standalone selling price of each performance obligation in the contract. Lease revenues are recorded as equipment revenues and recognized as earned on a straight-line basis over the lease term. Lease revenues on contracts not probable of collection are limited to the amount of payments received. See “Property and Equipment” above for further information. Advertising and Search Revenues Effective April 1, 2020, certain of our advertising and search revenues are now presented within Roaming and other service revenues, resulting in a reclassification of $506 million and $449 million for the years ended December 31, 2019 and 2018, respectively. These revenues were previously presented within Other revenues in our Consolidated Statements of Comprehensive Income. Prior periods have been reclassified to conform to current period presentation. Imputed Interest on EIP Receivables We record the effects of financing on all EIP loans regardless of whether or not the financing is considered to be significant. The imputation of interest results in a discount of the EIP receivable, thereby adjusting the transaction price of the contract with the customer, which is then allocated to the performance obligations of the arrangement. For transactions where we recognize a significant financing component, judgment is required to determine the discount rate. For EIP sales, the discount rate used to adjust the transaction price primarily reflects current market interest rates and the estimated credit risk of the customer. Customer credit behavior is inherently uncertain. See “Receivables and Allowance for Credit Losses” above, for additional discussion on how we assess credit risk. For indirect channel loans to the end service customer in which the sale of the device was to the dealer (sell-in basis), the effect of imputing interest is recognized as a reduction to service revenue, the only performance obligation with the service customer as the device sale was recognized when transferred to the dealer, over the service contract period. Our policies for imputed interest on EIP receivables are applied to loans originated for Sprint and Boost (up to the sale of the Prepaid Business to DISH on July 1, 2020) customers subsequent to Merger close. Contract Balances Generally, our devices and service plans are available at standard prices, which are maintained on price lists and published on our website and/or within our retail stores. For contracts that involve more than one product or service that are identified as separate performance obligations, the transaction price is allocated to the performance obligations based on their relative standalone selling prices. The standalone selling price is the price at which we would sell the good or service separately to a customer and is most commonly evidenced by the price at which we sell that good or service separately in similar circumstances and to similar customers. A contract asset is recorded when revenue is recognized in advance of our right to receive consideration (i.e., we must perform additional services in order to receive consideration). Amounts are recorded as receivables when our right to consideration is unconditional. When consideration is received, or we have an unconditional right to consideration in advance of delivery of goods or services, a contract liability is recorded. The transaction price can include non-refundable upfront fees, which are allocated to the identifiable performance obligations. Contract assets are included in Other current assets and Other assets and contract liabilities are included in Deferred revenue in our Consolidated Balance Sheets. Contract Modifications Our service contracts allow customers to frequently modify their contracts without incurring penalties, in many cases. Each time a contract is modified, we evaluate the change in scope or price of the contract to determine if the modification should be treated as a separate contract, as if there is a termination of the existing contract and creation of a new contract, or if the modification should be considered a change associated with the existing contract. We typically do not have significant impacts from contract modifications. Contract Costs We incur certain incremental costs to obtain a contract that we expect to recover, such as sales commissions. We record an asset when these incremental costs to obtain a contract are incurred and amortize them on a systematic basis that is consistent with the transfer to the customer of the goods or services to which the asset relates. We capitalize postpaid sales commissions for service activation as costs to acquire a contract and amortize them over the estimated period of benefit, currently 24 months. For capitalized contract costs, determining the amortization period over which such costs are recognized as well as assessing the indicators of impairment may require significant judgment. Prepaid commissions are expensed as incurred as their estimated period of benefit does not extend beyond 12 months. Commissions paid upon device upgrade are not capitalized if the remaining customer contract is less than one year. Commissions paid when the customer has a lease are treated as initial direct costs and recognized over the lease term. Our policies for the capitalization and amortization of costs to acquire a contract are applied to the Sprint, Boost (up to the sale of the Prepaid Business to Dish on July 1, 2020) and Assurance Wireless brands subsequent to the Merger close. Incremental costs to obtain equipment contracts (e.g., commissions paid on device and accessory sales) are recognized when the equipment is transferred to the customer. Brightstar Distribution We had arrangements with Brightstar US, Inc. (“Brightstar”), a subsidiary of SoftBank, whereby Brightstar provided supply chain and inventory management services to us in our indirect channels. T-Mobile sold devices through Brightstar to T-Mobile indirect channels who then sold the device to an end customer. The supply chain and inventory management arrangement included, among other things, that Brightstar may purchase inventory from the original equipment manufacturers to sell through to our indirect channels. As compensation for these services, we remitted per unit fees to Brightstar for each device sold to these indirect dealers. Devices sold from T-Mobile to Brightstar do not meet the criteria for a sale. Devices transferred from T-Mobile to Brightstar remain in inventory until control is transferred upon the sale of the device to the end customer, and in some circumstances to the indirect dealer. For customers who choose to lease a device previously sold to the indirect dealer, T-Mobile will repurchase the device from the indirect dealer and originate a lease directly with the end customer. Repurchase activity from the indirect dealer is estimated and treated as a right of return, reducing equipment revenue at the time of sale to the indirect dealer. Upon lease to the end customer, T-Mobile recognizes lease revenue over the associated lease term within Equipment revenues in our Consolidated Statements of Comprehensive Income. By December 31, 2020, we had terminated or restructured most of our arrangements with Brightstar, except for reverse logistics and trade-in services.
Leases	Leases (effective January 1, 2019) Cell Site, Retail Store and Office Facility Leases We are a lessee for non-cancelable operating and financing leases for cell sites, switch sites, retail stores, network equipment and office facilities with contractual terms that generally extend through 2035. Additionally, we lease dark fiber through non-cancelable operating leases with contractual terms that generally extend through 2041. The majority of cell site leases have a non-cancelable term of five five In addition, we have financing leases for certain network equipment that generally have a non-cancelable lease term of two We consider several factors in assessing whether renewal periods are reasonably certain of being exercised, including the continued maturation of our nationwide network, technological advances within the telecommunications industry and the availability of alternative sites. We have concluded it is not reasonably certain that we would exercise the options to extend or terminate our leases. Therefore, as of the lease commencement date, our lease terms generally do not include these options. We include options to extend or terminate a lease when it is reasonably certain that we will exercise that option. In determining the discount rate used to measure the right-of-use asset and lease liability, we use rates implicit in the lease, or if not readily available, we use our incremental borrowing rate. Our incremental borrowing rate is based on an estimated secured rate comprised of a risk-free LIBOR rate plus a credit spread as secured by our assets. Determining a credit spread as secured by our assets may require significant judgment. Certain of our lease agreements include rental payments based on changes in the consumer price index (“CPI”). Lease liabilities are not remeasured as a result of changes in the CPI; instead, changes in the CPI are treated as variable lease payments and are excluded from the measurement of the right-of-use asset and lease liability. These payments are recognized in the period in which the related obligation is incurred. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. Generally, we elected the practical expedient to not separate lease and non-lease components in arrangements where we are the lessee. For arrangements in which we are the lessor of wireless devices, we did not elect this practical expedient. We did not elect the short-term lease recognition exemption; as such, leases with terms shorter than 12-months are included as a right-of-use asset and lease liability. Rental revenues and expenses associated with co-location tower sites are presented on a net basis under Topic 842. These revenues and expenses were presented on a gross basis under Topic 840. See Note 17 - Leases for further information. See Note 1 - Summary of Significant Accounting Policies included in our Annual Report on Form 10-K for the year ended December 31, 201 8 , for additional discussion regarding the accounting policies that governed leases prior to January 1, 2019. Cell Tower Monetization Transactions In 2012, we entered into a prepaid master lease in which we as the lessor provided the rights to utilize tower sites and we leased back space on certain of those towers. Prior to the Merger, Sprint entered into a similar lease-out and leaseback arrangement which we assumed in the Merger. These arrangements are treated as failed sale leasebacks in which the proceeds received are reported as a financing obligation. The principal payments on the tower obligations are included in Other, net within Net cash provided by (used in) financing activities in our Consolidated Statements of Cash Flows. Our historical tower site asset costs are reported in Property and equipment, net in our Consolidated Balance Sheets and are depreciated. See Note 9 - Tower Obligations for further information.
Sprint Retirement Pension Plan	Sprint Retirement Pension Plan Through the Merger, we acquired the assets and assumed the liabilities associated with the Sprint Retirement Pension Plan (the “Pension Plan”), which is a defined benefit pension plan providing postretirement benefits to certain employees. As of December 31, 2005, the Pension Plan was amended to freeze benefit plan accruals for participants. The investments in the Pension Plan are measured at fair value on a recurring basis each quarter using quoted market prices or the net asset value per share as a practical expedient. The projected benefit obligations associated with the Pension Plan are determined based on actuarial models utilizing mortality tables and discount rates applied to the expected benefit term. See Note 11 - Employee Compensation and Benefit Plans for further information on the Pension Plan.
Advertising Expense	Advertising ExpenseWe expense the cost of advertising and other promotional expenditures to market our services and products as incurred.
Income Taxes	Income Taxes Deferred tax assets and liabilities are recognized based on temporary differences between the financial statement and tax bases of assets and liabilities using enacted tax rates expected to be in effect when these differences are realized. A valuation allowance is recorded when it is more likely than not that some portion or all of a deferred tax asset will not be realized. The ultimate realization of a deferred tax asset depends on the ability to generate sufficient taxable income of the appropriate character and in the appropriate taxing jurisdictions within the carryforward periods available. We account for uncertainty in income taxes recognized in the financial statements in accordance with the accounting guidance for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. We
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Other comprehensive income (loss) consists of adjustments, net of tax, related to unrealized gains (losses) on cash flow hedges, available-for-sale securities, foreign currency translation and pension and other postretirement benefits. This is reported in Accumulated other comprehensive loss as a separate component of stockholders’ equity until realized in earnings.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation cost for stock awards, which include restricted stock units (“RSUs”) and performance-based restricted stock units (“PRSUs”), is measured at fair value on the grant date and recognized as expense, net of expected forfeitures, over the related service period. The fair value of stock awards is based on the closing price of our common stock on the date of grant. RSUs are recognized as expense using the straight-line method. PRSUs are recognized as expense following a graded vesting schedule with their performance re-assessed and updated on a quarterly basis, or more frequently as changes in facts and circumstances warrant.
Earnings Per Share	Earnings Per ShareBasic earnings per share is computed by dividing Net income attributable to common stockholders by the weighted-average number of common shares outstanding for the period. Diluted earnings per share is computed by giving effect to all potentially dilutive common shares outstanding during the period. Potentially dilutive common shares consist of outstanding stock options, RSUs and PRSUs, calculated using the treasury stock method.
Variable Interest Entities	Variable Interest Entities VIEs are entities that lack sufficient equity to permit the entity to finance its activities without additional subordinated financial support from other parties, have equity investors that do not have the ability to make significant decisions relating to the entity's operations through voting rights, do not have the obligation to absorb the expected losses or do not have the right to receive the residual returns of the entity. The most common type of VIE is a special purpose entity (“SPE”). SPEs are commonly used in securitization transactions in order to isolate certain assets and distribute the cash flows from those assets to investors. SPEs are generally structured to insulate investors from claims on the SPEs’ assets by creditors of other entities, including the creditors of the seller of the assets, these SPEs are commonly referred to as being bankruptcy remote. The primary beneficiary is required to consolidate the assets and liabilities of the VIE. The primary beneficiary is the party which has both the power to direct the activities of an entity that most significantly impact the VIE's economic performance, and through its interests in the VIE, the obligation to absorb losses or the right to receive benefits from the VIE which could potentially be significant to the VIE. We consolidate VIEs when we are deemed to be the primary beneficiary or when the VIE cannot be deconsolidated. See Note 4 - Sales of Certain Receivables and Note 9 - Tower Obligations for further information. In assessing which party is the primary beneficiary, all the facts and circumstances are considered, including each party’s role in establishing the VIE and its ongoing rights and responsibilities. This assessment includes, first, identifying the activities that most significantly impact the VIE’s economic performance; and second, identifying which party, if any, has power over those activities. In general, the parties that make the most significant decisions affecting the VIE (such as asset managers and servicers) or have the right to unilaterally remove those decision-makers are deemed to have the power to direct the activities of a VIE.
Device Purchases Cash Flow Presentation	Device Purchases Cash Flow Presentation We classify all device purchases, whether acquired for sale or lease, as operating cash outflows as our predominant strategy is to sell devices to customers rather than lease them. See Note 20 – Additional Financial Information for disclosures of Leased devices transferred from inventory to property and equipment and Returned leased devices transferred from property and equipment to inventory.
Accounting Pronouncements Adopted During the Current Year/Accounting Pronouncements Not Yet Adopted	Accounting Pronouncements Adopted During the Current Year Receivables and Expected Credit Losses In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments,” and has since modified the standard with several ASUs (collectively, the “new credit loss standard”). The new credit loss standard requires a financial asset (or a group of financial assets) measured at amortized cost basis to be presented at the net amount expected to be collected. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions and reasonable and supportable forecasts that affect the collectibility of the reported amount. The new credit loss standard became effective for us, and we adopted the standard, on January 1, 2020. The new credit loss standard required a cumulative-effect adjustment to Accumulated deficit at the date of initial application, and as a result, we did not restate prior periods presented in the consolidated financial statements. Under the new credit loss standard, we recognize lifetime expected credit losses at the inception of our credit risk exposures, whereas we previously recognized credit losses only when it was probable that they had been incurred. We also recognize expected credit losses on our EIP receivables, which are inclusive of all installment receivables acquired in the Merger or issued thereafter, separately from, and in addition to, any unamortized discount on those receivables. Prior to the adoption of the new credit loss standard, we had offset our estimate of probable losses on our EIP receivables by the amount of the related unamortized discounts on those receivables. We have developed an expected credit loss model incorporating forward-looking loss indicators. The cumulative effect of initially applying the new credit loss standard on our receivables portfolio on January 1, 2020 was an increase to our allowance for credit losses of $91 million, a decrease to our net deferred tax liabilities of $24 million and an increase to our Accumulated deficit of $67 million. For EIP receivables acquired in the Merger, we also recognize expected credit losses separately from, and in addition to, the acquisition date fair value of the acquired EIP receivables. Cloud Computing Arrangements In August 2018, the FASB issued ASU 2018-15, “Intangibles - Goodwill and Other - Internal-Use Software (Topic 350): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract.” The standard aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The standard also requires the presentation of the amortization of the capitalized implementation costs in the same line item in the Consolidated Statements of Comprehensive Income as the fees associated with the hosting arrangement. The standard became effective for us, and we adopted the standard, on January 1, 2020. We adopted the standard on a prospective basis applying it to implementation costs incurred subsequent to January 1, 2020 and, as a result, did not restate the prior periods presented in the consolidated financial statements. The adoption of the standard did not have a material impact on our consolidated financial statements for the year ended December 31, 2020. Income Taxes In December 2019, the FASB issued ASU 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes.” The standard removes certain exceptions to the general principles in Topic 740. We early adopted the standard on January 1, 2020 and have applied the standard retrospectively to all periods presented. The adoption of this standard did not have a material impact on our consolidated financial statements for the year ended December 31, 2020. Guarantor Financial Information On March 2, 2020, the Securities and Exchange Commission (the “SEC”) adopted amendments to the financial disclosure requirements for guarantors and issuers of guaranteed securities, as well as for affiliates whose securities collateralize a registrant’s securities. The amendments revise Rules 3-10 and 3-16 of Regulation S-X, and relocate part of Rule 3-10 and all of Rule 3-16 to the new Article 13 in Regulation S-X, which is comprised of new Rules 13-01 and 13-02. We early adopted the requirements of the amendments on January 1, 2020, which included replacing guarantor condensed consolidating financial information with summarized financial information for the consolidated obligor group (Parent, Issuer, and Guarantor Subsidiaries) and no longer requiring guarantor cash flow information, financial information for non-guarantor subsidiaries, or a reconciliation to the consolidated results. Regulation S-K Modernization Amendments On August 26, 2020, the SEC adopted amendments to modernize the description of business (Item 101), legal proceedings (Item 103), and risk factor disclosures (Item 105) that registrants are required to make pursuant to Regulation S-K. The amendments are intended to elicit improved disclosures for investors and add efficiencies to the compliance efforts of registrants. The amendments are also intended to improve the readability of disclosure documents, as well as discourage repetition and reduce the disclosure of unnecessary information. The amendments became effective for us, and we adopted the amendments on November 9, 2020, which included making certain updates to our description of business and risk factor disclosures within our Form 10-K for the year ended December 31, 2020. Accounting Pronouncements Not Yet Adopted Reference Rate Reform In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” The standard provides temporary optional expedients and allows for certain exceptions to applying existing GAAP for contract modifications and hedging relationships, subject to meeting certain criteria, that reference LIBOR or another reference rate expected to be discontinued as a result of reference rate reform. The standard is available for adoption for a limited time through December 31, 2022. We are currently evaluating the impact this standard will have, including optional expedients, on our consolidated financial statements. Management’s Discussion and Analysis, Selected Financial Data and Supplementary Information Amendments On January 11, 2021, the SEC adopted amendments to eliminate the requirement for Selected Financial Data, streamline the requirement to disclose Supplementary Financial Information and amend Management’s Discussion & Analysis of Financial Condition and Results of Operations (“MD&A”). These amendments are intended to eliminate duplicative disclosures and modernize and enhance MD&A for the benefit of investors, while simplifying compliance efforts for registrants. The amendments became effective on February 10, 2021. We are currently evaluating the impact these amendments will have on our consolidated financial statements. We will apply the amendments, as applicable, to relevant filings made with the SEC subsequent to this Form 10-K. Other recent accounting pronouncements issued by the FASB (including its Emerging Issues Task Force), the American Institute of Certified Public Accountants, and the SEC did not have, or are not expected to have, a significant impact on our present or future consolidated financial statements.

Business Combination (Tables)

Business Combination (Tables)	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Schedule of Components of Consideration Transferred	The acquisition-date fair value of consideration transferred in the Merger totaled $40.8 billion, comprised of the following: (in millions) April 1, 2020 Fair value of T-Mobile common stock issued to Sprint stockholders (1) $ 31,328 Fair value of T-Mobile replacement equity awards attributable to pre-combination service (2) 323 Repayment of Sprint’s debt (including accrued interest and prepayment penalties) (3) 7,396 Value of contingent consideration (4) 1,882 Payment received from selling stockholder (5) (102) Total consideration exchanged $ 40,827 (1) Represents the fair value of T-Mobile common stock issued to Sprint stockholders pursuant to the Business Combination Agreement, less shares surrendered by SoftBank pursuant to the Letter Agreement. The fair value is based on 373,396,310 shares of Sprint common stock issued and outstanding as of March 31, 2020, an exchange ratio of 0.10256 shares of T-Mobile common stock per share of Sprint common stock, less 48,751,557 T-Mobile shares surrendered by SoftBank which are treated as contingent consideration, and the closing price per share of T-Mobile common stock on NASDAQ on March 31, 2020, of $83.90, as shares were transferred to Sprint stockholders prior to the opening of markets on April 1, 2020. (2) Equity-based awards held by Sprint employees prior to the acquisition date have been replaced with T-Mobile equity-based awards. The portion of the equity-based awards that relates to services performed by the employee prior to the acquisition date is included within consideration transferred, and includes stock options, restricted stock units and performance-based restricted stock units. (3) Represents the cash consideration paid concurrent with the close of the Merger to retire certain Sprint debt, as required by change in control provisions of the debt, plus interest and prepayment penalties. (4) Represents the fair value of the SoftBank Specified Shares Amount contingent consideration that may be issued as set forth in the Letter Agreement. (5) Represents receipt of a cash payment from SoftBank for certain expenses associated with the Merger and is presented in Cash paid for acquisition of companies, net of cash acquired within our Consolidated Statements of Cash Flows.
Schedule of Amounts Recognized as of Acquisition Date	The following table summarizes the estimated fair values for each major class of assets acquired and liabilities assumed at the acquisition date. We retained the services of certified valuation specialists to assist with assigning estimated values to certain acquired assets and assumed liabilities. As of December 31, 2020, the valuation of assets acquired and liabilities assumed is substantially complete except for the finalization of certain aspects of spectrum valuation, the valuation of certain income tax matters and loss contingencies. (in millions) April 1, 2020 Cash and cash equivalents $ 2,084 Accounts receivable 1,781 Equipment installment plan receivables 1,088 Inventory 658 Prepaid expenses 140 Assets held for sale 1,908 Other current assets 631 Property and equipment 18,435 Operating lease right-of-use assets 6,583 Financing lease right-of-use assets 291 Goodwill 9,401 Spectrum licenses 45,400 Other intangible assets 6,325 Equipment installment plan receivables due after one year, net 247 Other assets (1) 540 Total assets acquired 95,512 Accounts payable and accrued liabilities 4,944 Short-term debt 2,760 Deferred revenue 508 Short-term operating lease liabilities 1,818 Short-term financing lease liabilities 8 Liabilities held for sale 475 Other current liabilities 671 Long-term debt 29,037 Tower obligations 950 Deferred tax liabilities 3,513 Operating lease liabilities 5,615 Financing lease liabilities 12 Other long-term liabilities 4,374 Total liabilities assumed 54,685 Total consideration transferred $ 40,827 (1) Included in Other assets acquired is $80 million in restricted cash.
Schedule of Pro Forma Information	The following unaudited pro forma financial information gives effect to the Transactions as if they had been completed on January 1, 2019. The unaudited pro forma information was prepared in accordance with the requirements of ASC 805, which is a different basis than pro forma information prepared under Article 11 of Regulation S-X (“Article 11”). As such, they are not directly comparable with historical results for stand-alone T-Mobile prior to April 1, 2020, historical results for T-Mobile from April 1, 2020 that reflect the Transactions and are inclusive of the results and operations of Sprint, nor our previously provided pro forma financials prepared in accordance with Article 11. The pro forma results for the years ended December 31, 2020 and 2019 include the impact of several adjustments to previously reported operating results. The pro forma adjustments are based on historically reported transactions by the respective companies. The pro forma results do not include any anticipated synergies or other expected benefits of the acquisition. Year Ended December 31, (in millions, except per share amounts) 2020 2019 Total revenues $ 74,681 $ 70,607 Income from continuing operations 3,302 185 Income from discontinued operations, net of tax 677 1,594 Net income 3,979 1,792

Receivables and Expected Cred_2

Receivables and Expected Credit Losses (Tables)	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Schedule of Equipment Installment Plan Receivables	The following table summarizes the EIP receivables, including imputed discounts and related allowance for credit losses: (in millions) December 31, December 31, EIP receivables, gross (1) $ 6,213 $ 4,582 Unamortized imputed discount (325) (299) EIP receivables, net of unamortized imputed discount 5,888 4,283 Allowance for credit losses (2) (280) (100) EIP receivables, net of allowance for credit losses and imputed discount $ 5,608 $ 4,183 Classified on the balance sheet as: Equipment installment plan receivables, net of allowance for credit losses and imputed discount $ 3,577 $ 2,600 Equipment installment plan receivables due after one year, net of allowance for credit losses and imputed discount 2,031 1,583 EIP receivables, net of allowance for credit losses and imputed discount $ 5,608 $ 4,183 (1) Through the Merger, we acquired EIP receivables with a fair value of $1.3 billion as of April 1, 2020. As they were recorded at fair value, an imputed discount was not recognized on the acquired receivables. (2) Allowance for credit losses as of December 31, 2020 was impacted by the cumulative effect of initially applying the new credit loss standard on our receivables portfolio on January 1, 2020, which resulted in an increase to our allowance for credit losses of $91 million.
Schedule of Equipment Installment Plan Receivables by Credit Category	The following table presents the amortized cost of our EIP receivables by delinquency status, customer credit class, and year of origination as of December 31, 2020. Originated in 2020 Originated in 2019 Originated prior to 2019 Total EIP Receivables, net of (in millions) Prime Subprime Prime Subprime Prime Subprime Prime Subprime Grand total Current - 30 days past due $ 2,654 $ 2,035 $ 528 $ 407 $ 124 $ 26 $ 3,306 $ 2,468 $ 5,774 31 - 60 days past due 16 30 6 12 1 — 23 42 65 61 - 90 days past due 4 13 2 5 — — 6 18 24 More than 90 days past due 3 11 2 6 1 2 6 19 25 EIP receivables, net of unamortized imputed discount $ 2,677 $ 2,089 $ 538 $ 430 $ 126 $ 28 $ 3,341 $ 2,547 $ 5,888
Schedule of Unamortized Imputed Discount and Allowance for Credit Losses for Equipment Installment Plan Receivables	Activity for the years ended December 31, 2020, 2019 and 2018 in the allowance for credit losses and unamortized imputed discount balances for the accounts receivable and EIP receivables segments were as follows: December 31, 2020 December 31, 2019 December 31, 2018 (in millions) Accounts Receivable Allowance EIP Receivables Allowance Total Accounts Receivable Allowance EIP Receivables Allowance Total Accounts Receivable Allowance EIP Receivables Allowance Total Allowance for credit losses and imputed discount, beginning of period $ 61 $ 399 $ 460 $ 67 $ 449 $ 516 $ 86 $ 396 $ 482 Beginning balance adjustment due to implementation of the new credit loss standard — 91 91 — — — — — — Bad debt expense 338 264 602 77 230 307 69 228 297 Write-offs, net of recoveries (205) (175) (380) (83) (249) (332) (88) (240) (328) Change in imputed discount on short-term and long-term EIP receivables N/A 171 171 N/A 136 136 N/A 250 250 Impact on the imputed discount from sales of EIP receivables N/A (145) (145) N/A (167) (167) N/A (185) (185) Allowance for credit losses and imputed discount, end of period $ 194 $ 605 $ 799 $ 61 $ 399 $ 460 $ 67 $ 449 $ 516

Sales of Certain Receivables (T

Sales of Certain Receivables (Tables)	12 Months Ended
	Dec. 31, 2020
Transfers and Servicing [Abstract]
Schedule of Variable Interest Entities	The following table summarizes the carrying amounts and classification of assets, which consist primarily of the deferred purchase price, and liabilities included in our Consolidated Balance Sheets that relate to our variable interest in the Service VIE: (in millions) December 31, December 31, Other current assets $ 378 $ 350 Accounts payable and accrued liabilities — 25 Other current liabilities 357 342
Schedule of variable interest entities - EIP	The following table summarizes the carrying amounts and classification of assets, which consist primarily of the deferred purchase price, and liabilities included in our Consolidated Balance Sheets of the EIP BRE: (in millions) December 31, December 31, Other current assets $ 388 $ 344 Other assets 120 89 Other long-term liabilities 4 18
Schedule of Factoring Arrangement	The following table summarizes the impact of the sale of certain service receivables and EIP receivables in our Consolidated Balance Sheets: (in millions) December 31, December 31, Derecognized net service receivables and EIP receivables $ 2,528 $ 2,584 Other current assets 766 694 of which, deferred purchase price 764 692 Other long-term assets 120 89 of which, deferred purchase price 120 89 Accounts payable and accrued liabilities — 25 Other current liabilities 357 342 Other long-term liabilities 4 18 Net cash proceeds since inception 1,715 1,944 Of which: Change in net cash proceeds during the year-to-date period (229) 65 Net cash proceeds funded by reinvested collections 1,944 1,879

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	The components of property and equipment were as follows: (in millions) Useful Lives December 31, December 31, Land $ 236 $ — Buildings and equipment Up to 30 years 4,006 2,587 Wireless communications systems Up to 20 years 49,453 34,353 Leasehold improvements Up to 12 years 1,879 1,345 Capitalized software Up to 10 years 16,412 12,705 Leased wireless devices Up to 19 months 6,989 1,139 Construction in progress 4,595 2,973 Accumulated depreciation and amortization (42,395) (33,118) Property and equipment, net $ 41,175 $ 21,984
Schedule of Asset Retirement Obligations	Activity in our asset retirement obligations was as follows: (in millions) Year Ended Year Ended Asset retirement obligations, beginning of year $ 659 $ 609 Fair value of liabilities acquired through Merger 1,110 — Liabilities incurred 16 35 Liabilities settled (40) (2) Accretion expense 55 32 Changes in estimated cash flows 17 (15) Asset retirement obligations, end of period $ 1,817 $ 659 Classified on the balance sheet as: Other current liabilities $ 14 $ — Other long-term liabilities 1,803 659

Goodwill, Spectrum License Tr_2

Goodwill, Spectrum License Transactions and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The changes in the carrying amount of goodwill for the years ended December 31, 2020 and 2019, are as follows: (in millions) Goodwill Historical goodwill, net of accumulated impairment losses of $10,766 $ 1,901 Goodwill from acquisition in 2019 29 Balance as of December 31, 2019 1,930 Goodwill from acquisitions in 2020 9,405 Layer3 goodwill impairment (218) Balance as of December 31, 2020 $ 11,117 Accumulated impairment losses at December 31, 2020 $ (10,984)
Schedule of Fair Value of Intangible Assets Acquired in Merger	The following table summarizes the fair value of the intangible assets acquired in the Merger: Weighted Average Useful Life (in years) Fair Value as of April 1, 2020 Spectrum licenses Indefinite-lived $ 45,400 Tradenames (1) 2 years 207 Customer relationships 8 years 4,900 Favorable spectrum leases 18 years 790 Other intangible assets 7 years 428 Total intangible assets acquired $ 51,725 (1) Tradenames include the Sprint brand
Schedule of Spectrum Licenses	The following table summarizes our spectrum license activity for the years ended December 31, 2020 and 2019: (in millions) 2020 2019 Spectrum licenses, beginning of year $ 36,465 $ 35,559 Spectrum license acquisitions 1,023 857 Spectrum licenses acquired in Merger 45,400 — Spectrum licenses transferred to held for sale (83) — Costs to clear spectrum 23 49 Spectrum licenses, end of year $ 82,828 $ 36,465
Schedule of Other Intangible Assets	The components of Other intangible assets were as follows: Useful Lives December 31, 2020 December 31, 2019 (in millions) Gross Amount Accumulated Amortization Net Amount Gross Amount Accumulated Amortization Net Amount Customer relationships Up to 8 years $ 4,900 $ (865) $ 4,035 $ 1,104 $ (1,104) $ — Tradenames and patents Up to 19 years 598 (412) 186 323 (258) 65 Favorable spectrum leases Up to 27 years 790 (35) 755 — — — Other Up to 10 years 377 (55) 322 100 (50) 50 Other intangible assets $ 6,665 $ (1,367) $ 5,298 $ 1,527 $ (1,412) $ 115
Schedule of Estimated Aggregate Future Amortization Expense	The estimated aggregate future amortization expense for intangible assets subject to amortization are summarized below: (in millions) Estimated Future Amortization Twelve Months Ending December 31, 2021 $ 1,246 2022 982 2023 827 2024 669 2025 511 Thereafter 1,063 Total $ 5,298

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Carrying Values and Fair Values of Long-term Debt	The carrying amounts and fair values of our short-term and long-term debt included in our Consolidated Balance Sheets were as follows: Level within the Fair Value Hierarchy December 31, 2020 December 31, 2019 (in millions) Carrying Amount (1) Fair Value (1) Carrying Amount (1) Fair Value (1) Liabilities: Senior Unsecured Notes to third parties 1 $ 29,966 $ 32,450 $ 10,958 $ 11,479 Senior Notes to affiliates 2 4,716 4,991 9,986 10,366 Senior Secured Notes to third parties 1 36,204 40,519 — — Incremental Term Loan Facility to affiliates 2 — — 4,000 4,000 (1) Excludes $240 million and $25 million as of December 31, 2020 and 2019, respectively, in vendor financing arrangements and other debt as the carrying values approximate fair value primarily due to the short-term maturities of these instruments.

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Debt	Debt was as follows: (in millions) December 31, December 31, 3.360% Series 2016-1 A-1 Notes due 2021 $ 656 $ — 5.300% Senior Notes to affiliates due 2021 — 2,000 7.250% Senior Notes due 2021 2,250 — 11.500% Senior Notes due 2021 1,000 — 4.000% Senior Notes to affiliates due 2022 1,000 1,000 4.000% Senior Notes due 2022 500 500 6.000% Senior Notes due 2022 2,280 — Incremental term loan facility to affiliates due 2022 — 2,000 6.000% Senior Notes due 2023 1,300 1,300 7.875% Senior Notes due 2023 4,250 — 6.000% Senior Notes due 2024 1,000 1,000 6.000% Senior Notes to affiliates due 2024 — 1,350 6.000% Senior Notes to affiliates due 2024 — 650 6.500% Senior Notes due 2024 — 1,000 7.125% Senior Notes due 2024 2,500 — Incremental term loan facility to affiliates due 2024 — 2,000 3.500% Senior Secured Notes due 2025 3,000 — 4.738% Series 2018-1 A-1 Notes due 2025 2,100 — 5.125% Senior Notes to affiliates due 2025 (1) — 1,250 5.125% Senior Notes due 2025 500 500 6.375% Senior Notes due 2025 — 1,700 7.625% Senior Notes due 2025 1,500 — 1.500% Senior Secured Notes due 2026 1,000 — 6.500% Senior Notes due 2026 2,000 2,000 4.500% Senior Notes due 2026 1,000 1,000 4.500% Senior Notes to affiliates due 2026 1,000 1,000 7.625% Senior Notes due 2026 1,500 — 3.750% Senior Secured Notes due 2027 4,000 — 5.375% Senior Notes due 2027 500 500 5.375% Senior Notes to affiliates due 2027 (1) 1,250 1,250 2.050% Senior Secured Notes due 2028 1,750 — 4.750% Senior Notes due 2028 1,500 1,500 4.750% Senior Notes to affiliates due 2028 1,500 1,500 5.152% Series 2018-1 A-2 Notes due 2028 1,838 — 6.875% Senior Notes due 2028 2,475 — 3.875% Senior Secured Notes due 2030 7,000 — 2.250% Senior Secured Notes due 2031 1,000 — 2.550% Senior Secured Notes due 2031 2,500 — 8.750% Senior Notes due 2032 2,000 — 4.375% Senior Secured Notes due 2040 2,000 — 3.000% Senior Secured Notes due 2041 2,500 — 4.500% Senior Secured Notes due 2050 3,000 — 3.300% Senior Secured Notes due 2051 3,000 — 3.600% Senior Secured Notes due 2060 1,000 — Other debt 240 25 Unamortized premium on debt to affiliates — 43 Unamortized premium on debt to third parties 2,197 — Unamortized discount on debt to affiliates (20) (53) Unamortized discount on debt to third parties (197) — Debt issuance costs and consent fees (244) (46) Total debt 71,125 24,969 Less: Current portion of Senior Notes and other debt to third parties 4,579 25 Total long-term debt $ 66,546 $ 24,944 Classified on the balance sheet as: Long-term debt $ 61,830 $ 10,958 Long-term debt to affiliates 4,716 13,986 Total long-term debt $ 66,546 $ 24,944 (1) On April 1, 2020, in connection with the closing of the Merger, we amended the $1.25 billion of 5.125% Senior Notes to affiliates due 2025 and $1.25 billion of 5.375% Senior Notes to affiliates due 2027, to change the maturity date thereof to April 15, 2021 and April 15, 2022, respectively. See “Financing Matters Agreement” section below for further information. Our effective interest rate, excluding the impact of derivatives and capitalized interest, was approximately 4.6% and 5.2% for the years ended December 31, 2020 and 2019, respectively, on weighted average debt outstanding of $58.4 billion and $25.5 billion for the years ended December 31, 2020 and 2019, respectively. The weighted average debt outstanding was calculated by applying an average of the monthly ending balances of total short-term and long-term debt and short-term and long-term debt to affiliates, net of unamortized premiums, discounts, debt issuance costs and consent fees. Issuances and Borrowings During the year ended December 31, 2020, we issued the following Senior Secured Notes and entered into the following Secured loan facilities: (in millions) Principal Issuances Premiums, Discounts and Issuance Costs Net Proceeds from Issuance of Long-Term Debt Issue Date 3.500% Senior Secured Notes due 2025 $ 3,000 $ 12 $ 2,988 April 9, 2020 3.750% Senior Secured Notes due 2027 4,000 17 3,983 April 9, 2020 3.875% Senior Secured Notes due 2030 7,000 78 6,922 April 9, 2020 4.375% Senior Secured Notes due 2040 2,000 47 1,953 April 9, 2020 4.500% Senior Secured Notes due 2050 3,000 24 2,976 April 9, 2020 1.500% Senior Secured Notes due 2026 1,000 5 995 June 24, 2020 2.050% Senior Secured Notes due 2028 1,250 8 1,242 June 24, 2020 2.550% Senior Secured Notes due 2031 1,750 12 1,738 June 24, 2020 2.050% Senior Secured Notes due 2028 500 (11) 511 October 6, 2020 2.550% Senior Secured Notes due 2031 750 (29) 779 October 6, 2020 3.000% Senior Secured Notes due 2041 1,250 15 1,235 October 6, 2020 3.300% Senior Secured Notes due 2051 1,500 16 1,484 October 6, 2020 2.250% Senior Secured Notes due 2031 1,000 5 995 October 28, 2020 3.000% Senior Secured Notes due 2041 1,250 38 1,212 October 28, 2020 3.300% Senior Secured Notes due 2051 1,500 58 1,442 October 28, 2020 3.600% Senior Secured Notes due 2060 1,000 11 989 October 28, 2020 Total of Senior Secured Notes issued 31,750 306 31,444 Secured bridge loan facility due 2021 19,000 257 18,743 April 1, 2020 Secured term loan facility due 2027 4,000 107 3,893 April 1, 2020 Total of Secured loan facilities issued 23,000 364 22,636 Total Issuances and Borrowings $ 54,750 $ 670 $ 54,080 In connection with the Merger, we assumed the following indebtedness of Sprint: (in millions) Fair value as of April 1, 2020 Principal Outstanding as of December 31, 2020 Carrying Value as of December 31, 2020 7.250% Senior Notes due 2021 $ 2,324 $ 2,250 $ 2,287 7.875% Senior Notes due 2023 4,682 4,250 4,594 7.125% Senior Notes due 2024 2,746 2,500 2,706 7.625% Senior Notes due 2025 1,677 1,500 1,652 7.625% Senior Notes due 2026 1,701 1,500 1,679 3.360% Senior Secured Series 2016-1 A-1 Notes due 2021 (1) 1,310 656 656 4.738% Senior Secured Series 2018-1 A-1 Notes due 2025 (1) 2,153 2,100 2,145 5.152% Senior Secured Series 2018-1 A-2 Notes due 2028 (1) 1,960 1,838 1,950 7.000% Senior Notes due 2020 1,510 — — 11.500% Senior Notes due 2021 1,105 1,000 1,057 6.000% Senior Notes due 2022 2,372 2,280 2,346 6.875% Senior Notes due 2028 2,834 2,475 2,808 8.750% Senior Notes due 2032 2,649 2,000 2,620 Accounts receivable facility 2,310 — — Other debt 464 256 240 Total Debt Assumed $ 31,797 $ 24,605 $ 26,740
Debt Instrument Redemption	During the year ended December 31, 2020, we repaid the following loan facilities and redeemed the following Senior Notes held by third parties and Senior Notes held by affiliates: (in millions) Principal Amount Write-off of Premiums, Discounts and Issuance Costs (1) Other (2) Redemption or Repayment Date Redemption Price 6.500% Senior Notes due 2024 $ 1,000 $ 12 $ 22 July 4, 2020 102.167 % 7.000% Senior Notes due 2020 1,500 — — August 15, 2020 N/A 6.375% Senior Notes due 2025 1,700 24 36 September 1, 2020 102.125 % Total Senior Notes to third parties redeemed 4,200 36 58 5.300% Senior Notes to affiliates due 2021 (3) 2,000 — — April 1, 2020 100.000 % 6.000% Senior Notes to affiliates due 2024 (3) 1,350 (26) — April 1, 2020 100.000 % 6.000% Senior Notes to affiliates due 2024 (3) 650 (15) — April 1, 2020 100.000 % 5.125% Senior Secured Notes to affiliates due 2025 1,250 15 — July 4, 2020 100.000 % Total Senior Notes to affiliates redeemed 5,250 (26) — Total Redemptions $ 9,450 $ 10 $ 58 Incremental term loan facility to affiliates due 2022 $ 2,000 $ — $ — April 1, 2020 100.000 % Incremental term loan facility to affiliates due 2024 2,000 — — April 1, 2020 100.000 % Accounts receivable facility 2,310 — — April 1, 2020 100.000 % Secured bridge loan facility due 2021 19,000 251 (47) April 9, 2020 100.128 % 3.360% Senior Secured Series 2016-1 A-1 Notes due 2021 656 — — Various N/A Secured term loan facility due 2027 4,000 100 — October 9, 2020 100.000 % Other debt 481 — — Various N/A Total Repayments $ 30,447 $ 351 $ (47) (1) Write-off of premiums, discounts and issuance costs are included in Other expense, net in our Consolidated Statements of Comprehensive Income. Write-off of issuance costs are included in Loss on redemption of debt within Net cash provided by operating activities in our Consolidated Statements of Cash Flows. (2) Primarily represents a reimbursement of a portion of the commitment letter fees that were paid to financial institutions when we drew down on the Secured Bridge Loan Facility on April 1, 2020 and is included in Other expense, net in our Consolidated Statements of Comprehensive Income. (3) Pursuant to the Financing Matters Agreement, the Senior Notes were effectively redeemed through a repurchase and were cancelled and retired in full on April 1, 2020.

Tower Obligations (Tables)

Tower Obligations (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Summary of Impacts to Consolidated Balance Sheets	The following table summarizes the balances associated with both of the tower arrangements in the Consolidated Balance Sheets: (in millions) December 31, December 31, 2019 Property and equipment, net $ 2,838 $ 198 Tower obligations 3,028 2,236 Other long-term liabilities 1,712 —

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	Postpaid service revenues, including postpaid phone revenues and postpaid other revenues, were as follows: Year Ended December 31, (in millions) 2020 2019 2018 Postpaid service revenues Postpaid phone revenues $ 33,939 $ 21,329 $ 19,745 Postpaid other revenues 2,367 1,344 1,117 Total postpaid service revenues $ 36,306 $ 22,673 $ 20,862 Equipment revenues from the lease of mobile communication devices were as follows: Year Ended December 31, (in millions) 2020 2019 2018 Equipment revenues from the lease of mobile communication devices $ 4,181 $ 599 $ 692
Schedule of Contract Liability and Receivable Balances	The opening and closing balances of our contract asset and contract liability balances from contracts with customers as of December 31, 2019 and December 31, 2020, were as follows: (in millions) Contract Assets Contract Liabilities Balance as of December 31, 2019 $ 63 $ 560 Balance as of December 31, 2020 278 824 Change $ 215 $ 264 Revenues for the years ended December 31, 2020 and 2019, include the following: Year Ended December 31, (in millions) 2020 2019 Amounts included in the beginning of year contract liability balance $ 545 $ 643

Employee Compensation and Ben_2

Employee Compensation and Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Stock-based Compensation Expense and Related Income Tax Benefits	Stock-based compensation expense and related income tax benefits were as follows: As of and for the Year Ended December 31, (in millions, except shares, per share and contractual life amounts) 2020 2019 2018 Stock-based compensation expense $ 694 $ 495 $ 424 Income tax benefit related to stock-based compensation $ 132 $ 92 $ 81 Weighted average fair value per stock award granted $ 96.27 $ 73.25 $ 61.52 Unrecognized compensation expense $ 592 $ 515 $ 547 Weighted average period to be recognized (years) 1.9 1.6 1.8 Fair value of stock awards vested $ 1,315 $ 512 $ 471
Schedule of RSU and PRSU Awards Activity	Time-Based Restricted Stock Units and Restricted Stock Awards (in millions, except shares, per share and contractual life amounts) Number of Units or Awards Weighted Average Grant Date Fair Value Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Nonvested, December 31, 2019 10,503,211 $ 67.31 0.9 $ 824 Assumed through acquisition 1,852,527 83.90 Granted 5,891,303 97.18 Vested (7,112,552) 69.32 Forfeited (1,033,267) 84.52 Nonvested, December 31, 2020 10,101,222 84.61 0.9 1,362 Performance-Based Restricted Stock Units and Restricted Stock Awards (in millions, except shares, per share and contractual life amounts) Number of Units or Awards Weighted Average Grant Date Fair Value Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Nonvested, December 31, 2019 3,803,539 $ 69.78 1.0 $ 300 Assumed through acquisition 3,535,384 83.90 Granted 1,212,522 110.38 Performance award achievement adjustments (1) 887,528 70.96 Vested (6,127,838) 77.11 Forfeited (138,034) 83.90 Nonvested, December 31, 2020 3,173,101 86.58 1.0 428 PRSUs included in the table above are shown at target. Share payout can range from 0% to 200% based on different performance outcomes. Weighted average grant date fair value of RSU and PRSU assumed through acquisition is based on the fair value on the date assumed. (1) Represents PRSUs granted prior to 2020 for which the performance achievement period was completed in 2020, resulting in incremental unit awards. These PRSU awards are also included in the amount vested in 2020.
Schedule of Stock Options Activity	The following activity occurred under the Stock Option Plans: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Outstanding at December 31, 2019 194,942 $ 13.80 2.9 Assumed through acquisition 1,635,518 33.37 Exercised (906,295) 53.02 Expired/canceled (5,470) 49.75 Outstanding at December 31, 2020 918,695 51.77 4.0 Exercisable at December 31, 2020 917,955 51.79 4.0 Weighted average grant date fair value of stock options assumed through acquisition is based on the fair value on the date assumed.
Components of Net Expense Recognized for Pension Plan	The components of net expense recognized for the Pension Plan were as follows: (in millions) Year Ended December 31, 2020 Interest on projected benefit obligations $ 52 Expected return on pension plan assets (45) Net pension expense $ 7

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2020
Discontinued Operations and Disposal Groups [Abstract]
Schedule of Components of Discontinued Operations	The components of discontinued operations from the Merger close date of April 1, 2020, through December 31, 2020, were as follows: (in millions) Year Ended Major classes of line items constituting pretax income from discontinued operations Prepaid revenues $ 973 Roaming and other service revenues 27 Total service revenues 1,000 Equipment revenues 270 Total revenues 1,270 Cost of services 25 Cost of equipment sales 499 Selling, general and administrative 314 Total operating expenses 838 Pretax income from discontinued operations 432 Income tax expense (112) Income from discontinued operations $ 320

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax	Our sources of Income before income taxes were as follows: Year Ended December 31, (in millions) 2020 2019 2018 U.S. $ 3,493 $ 4,557 $ 3,686 Foreign 37 46 231 Income from continuing operations before income taxes $ 3,530 $ 4,603 $ 3,917
Schedule of Components of Income Tax Expense (Benefit)	Income tax expense is summarized as follows: Year Ended December 31, (in millions) 2020 2019 2018 Current tax benefit (expense) Federal $ 17 $ 24 $ 39 State (84) (70) (63) Foreign (10) 2 (25) Total current tax expense (77) (44) (49) Deferred tax benefit (expense) Federal (676) (954) (750) State (34) (125) (160) Foreign 1 (12) (70) Total deferred tax expense (709) (1,091) (980) Total income tax expense $ (786) $ (1,135) $ (1,029)
Schedule of Effective Income Tax Rate Reconciliation	The reconciliation between the U.S. federal statutory income tax rate and our effective income tax rate is as follows: Year Ended December 31, 2020 2019 2018 Federal statutory income tax rate 21.0 % 21.0 % 21.0 % Effect of law and rate changes (0.8) 0.4 1.9 Change in valuation allowance (2.6) (1.8) (1.6) State taxes, net of federal benefit 4.8 5.1 4.8 Foreign taxes, net of federal benefit 0.3 0.3 2.4 Permanent differences 0.4 0.6 0.7 Federal tax credits, net of reserves (0.9) (0.8) (2.9) Equity-based compensation (2.5) (0.6) (0.8) Non-deductible compensation 2.3 0.6 0.8 Other, net 0.3 (0.1) — Effective income tax rate 22.3 % 24.7 % 26.3 %
Schedule of Deferred Tax Assets and Liabilities	Significant components of deferred income tax assets and liabilities, tax effected, are as follows: (in millions) December 31, December 31, Deferred tax assets Loss carryforwards $ 4,540 $ 823 Lease liabilities 8,031 3,403 Property and equipment 90 — Reserves and accruals 1,348 659 Federal and state tax credits 411 331 Other 2,665 903 Deferred tax assets, gross 17,085 6,119 Valuation allowance (878) (129) Deferred tax assets, net 16,207 5,990 Deferred tax liabilities Spectrum licenses 17,518 5,902 Property and equipment — 2,506 Lease right-of-use assets 7,239 2,881 Other intangible assets 912 19 Other 504 289 Total deferred tax liabilities 26,173 11,597 Net deferred tax liabilities $ 9,966 $ 5,607 Classified on the balance sheet as: Deferred tax liabilities $ 9,966 $ 5,607
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amount of unrecognized tax benefits were as follows: Year Ended December 31, (in millions) 2020 2019 2018 Unrecognized tax benefits, beginning of year $ 514 $ 462 $ 412 Gross increases to tax positions in prior periods 6 — 16 Gross decreases to tax positions in prior periods (28) — (11) Gross increases to current period tax positions 45 64 39 Gross increases due to current period business acquisitions 624 — 10 Gross decreases due to settlements with taxing authorities (2) (12) (4) Unrecognized tax benefits, end of year $ 1,159 $ 514 $ 462

Repurchases of Common Stock (Ta

Repurchases of Common Stock (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of Repurchases of Common Stock	The following table summarizes information regarding repurchases of our common stock under the 2017 Stock Repurchase Program: (In millions, except shares and per share price) Year ended December 31, Number of Shares Repurchased Average Price Paid Per Share Total Purchase Price 2018 16,738,758 $ 62.96 $ 1,054

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of Earnings Per Share	The computation of basic and diluted earnings per share was as follows: Year Ended December 31, (in millions, except shares and per share amounts) 2020 2019 2018 Income from continuing operations $ 2,744 $ 3,468 $ 2,888 Income from discontinued operations, net of tax 320 — — Net income $ 3,064 $ 3,468 $ 2,888 Weighted average shares outstanding - basic 1,144,206,326 854,143,751 849,744,152 Effect of dilutive securities: Outstanding stock options and unvested stock awards 10,543,102 9,289,760 8,546,022 Weighted average shares outstanding - diluted 1,154,749,428 863,433,511 858,290,174 Basic earnings per share: Continuing operations $ 2.40 $ 4.06 $ 3.40 Discontinued operations 0.28 — — Earnings per share - basic $ 2.68 $ 4.06 $ 3.40 Diluted earnings per share: Continuing operations $ 2.37 $ 4.02 $ 3.36 Discontinued operations 0.28 — — Earnings per share - diluted $ 2.65 $ 4.02 $ 3.36 Potentially dilutive securities: Outstanding stock options and unvested stock awards 80,180 16,359 148,422 SoftBank contingent consideration (1) 36,630,268 — — (1) Represents the weighted average SoftBank Specified Shares outstanding from April 1, 2020, through December 31, 2020.

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Components of Lease Expense	The components of lease expense were as follows: Year Ended December 31, (in millions) 2020 2019 Operating lease expense $ 4,438 $ 2,558 Financing lease expense: Amortization of right-of-use assets 681 523 Interest on lease liabilities 81 82 Total financing lease expense 762 605 Variable lease expense 328 243 Total lease expense $ 5,528 $ 3,406
Schedule of Information Relating to Lease Term and Discount Rate	Information relating to the lease term and discount rate is as follows: Year Ended December 31, 2020 2019 Weighted Average Remaining Lease Term (Years) Operating leases 10 6 Financing leases 3 3 Weighted Average Discount Rate Operating leases 3.9 % 4.8 % Financing leases 3.3 % 4.0 %
Maturity Schedule of Operating Lease Liabilities	Maturities of lease liabilities as of December 31, 2020, were as follows: (in millions) Operating Leases Finance Leases Twelve Months Ending December 31, 2021 $ 4,903 $ 1,121 2022 4,354 795 2023 3,759 422 2024 3,339 137 2025 2,807 92 Thereafter 18,940 61 Total lease payments 38,102 2,628 Less: imputed interest 7,515 121 Total $ 30,587 $ 2,507
Maturity Schedule of Finance Lease Liabilities	Maturities of lease liabilities as of December 31, 2020, were as follows: (in millions) Operating Leases Finance Leases Twelve Months Ending December 31, 2021 $ 4,903 $ 1,121 2022 4,354 795 2023 3,759 422 2024 3,339 137 2025 2,807 92 Thereafter 18,940 61 Total lease payments 38,102 2,628 Less: imputed interest 7,515 121 Total $ 30,587 $ 2,507
Schedule of Leased Wireless Devices	The components of leased wireless devices under our Leasing Programs were as follows: (in millions) Average Remaining Useful Life December 31, 2020 December 31, 2019 Leased wireless devices, gross 8 months $ 6,989 $ 1,139 Accumulated depreciation (2,170) (407) Leased wireless devices, net $ 4,819 $ 732
Schedule of Future Minimum Payments Expected to be Received	Future minimum payments expected to be received over the lease term related to leased wireless devices, which exclude optional residual buy-out amounts at the end of the lease term, are summarized below: (in millions) Expected Payments Twelve Months Ending December 31, 2021 $ 1,687 2022 92 Total $ 1,779

Restructuring Costs (Tables)

Restructuring Costs (Tables)	12 Months Ended
	Dec. 31, 2020
Restructuring and Related Activities [Abstract]
Restructuring Plan Expenses Incurred	The following table summarizes the expenses incurred in connection with our restructuring initiatives: (in millions) Year Ended Contract termination costs $ 178 Severance costs 385 Network decommissioning 497 Total restructuring plan expenses $ 1,060
Activity Related to Expenses Incurred and Cash Payments Made	The changes in the liabilities associated with our restructuring initiatives, including expenses incurred and cash payments, are as follows: (in millions) April 1, Expenses Incurred Cash Payments Adjustments for Non-Cash Items (1) December 31, Contract termination costs $ — $ 178 $ (96) $ (1) $ 81 Severance costs — 385 (239) (94) 52 Network decommissioning — 497 (403) (64) 30 Total $ — $ 1,060 $ (738) $ (159) $ 163

Additional Financial Informat_2

Additional Financial Information (Tables)	12 Months Ended
	Dec. 31, 2020
Supplemental Financial Statement Elements [Abstract]
Schedule of Accounts Payable and Accrued Liabilities	Accounts payable and accrued liabilities are summarized as follows: (in millions) December 31, December 31, Accounts payable $ 5,564 $ 4,322 Payroll and related benefits 1,163 802 Property and other taxes, including payroll 1,540 682 Interest 771 227 Commissions 399 251 Toll and interconnect 217 156 Advertising 135 127 Other 407 179 Accounts payable and accrued liabilities $ 10,196 $ 6,746
Schedule of Significant Transactions with Affiliates	The following table summarizes the impact of significant transactions with DT or its affiliates included in Operating expenses in the Consolidated Statements of Comprehensive Income: Year Ended December 31, (in millions) 2020 2019 2018 Discount related to roaming expenses $ (5) $ (9) $ — Fees incurred for use of the T-Mobile brand 83 88 84 International long distance agreement 47 39 36
Schedule of Cash Flow, Supplemental Disclosures	The following table summarizes T-Mobile’s supplemental cash flow information: Year Ended December 31, (in millions) 2020 2019 2018 Interest payments, net of amounts capitalized $ 2,733 $ 1,128 $ 1,525 Operating lease payments 4,619 2,783 — Income tax payments 218 88 51 Non-cash investing and financing activities Non-cash beneficial interest obtained in exchange for securitized receivables 6,194 6,509 4,972 Non-cash consideration for the acquisition of Sprint 33,533 — — Change in accounts payable and accrued liabilities for purchases of property and equipment 589 (935) 65 Leased devices transferred from inventory to property and equipment 2,795 1,006 1,011 Returned leased devices transferred from property and equipment to inventory (1,460) (267) (326) Short-term debt assumed for financing of property and equipment 38 800 291 Operating lease right-of-use assets obtained in exchange for lease obligations 14,129 3,621 — Financing lease right-of-use assets obtained in exchange for lease obligations 1,273 1,041 885

Quarterly Financial Informati_2

Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information [Abstract]
Quarterly Financial Information	Quarterly Financial Information (Unaudited) The following table includes the impact of the Merger on a prospective basis from the Merger close date of April 1, 2020. Historical results have not been restated and reflect standalone T-Mobile. (in millions, except share and per share amounts) First Quarter Second Quarter Third Quarter Fourth Quarter Full Year 2020 Total revenues $ 11,113 $ 17,671 $ 19,272 $ 20,341 $ 68,397 Operating income 1,539 820 2,565 1,712 6,636 Income (loss) from continuing operations 951 (210) 1,253 750 2,744 Income from discontinued operations, net of tax — 320 — — 320 Net income 951 110 1,253 750 3,064 Earnings per share Basic earnings per share Continuing operations $ 1.11 $ (0.17) $ 1.01 $ 0.60 $ 2.40 Discontinued operations — 0.26 — — 0.28 Basic $ 1.11 $ 0.09 $ 1.01 $ 0.60 $ 2.68 Diluted earnings per share Continuing operations $ 1.10 $ (0.17) $ 1.00 $ 0.60 $ 2.37 Discontinued operations — 0.26 — — 0.28 Diluted $ 1.10 $ 0.09 $ 1.00 $ 0.60 $ 2.65 Weighted average shares outstanding Basic 858,148,284 1,236,528,444 1,238,450,665 1,241,578,615 1,144,206,326 Diluted 865,998,532 1,236,528,444 1,249,798,740 1,251,566,899 1,154,749,428 2019 Total revenues $ 11,080 $ 10,979 $ 11,061 $ 11,878 $ 44,998 Operating income 1,476 1,541 1,471 1,234 5,722 Income from continuing operations 908 939 870 751 3,468 Net income 908 939 870 751 3,468 Earnings per share Basic $ 1.07 $ 1.10 $ 1.02 $ 0.88 $ 4.06 Diluted $ 1.06 $ 1.09 $ 1.01 $ 0.87 $ 4.02 Weighted average shares outstanding Basic 851,223,498 854,368,443 854,578,241 856,294,467 854,143,751 Diluted 858,643,481 860,135,593 862,690,751 864,158,739 863,433,511

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Narrative (Details) $ in Millions

Jul. 01, 2020USD ($)

Apr. 01, 2020USD ($)shares

Dec. 31, 2020USD ($)

Sep. 30, 2020USD ($)

Jun. 30, 2020USD ($)

Mar. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Sep. 30, 2019USD ($)

Jun. 30, 2019USD ($)

Mar. 31, 2019USD ($)

Dec. 31, 2020USD ($)unit

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Jan. 01, 2020USD ($)

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Device upgrade period

18 months

Number of reporting units | unit

2

Fixed period

15 years

Federal Universal Service Fund and other fees

$ 267

$ 93

$ 161

Revenues

$ 20,341

$ 19,272

$ 17,671

$ 11,113

$ 11,878

$ 11,061

$ 10,979

$ 11,080

$ 68,397

44,998

43,310

Average amortization period, deferred contract costs (in months)

24 months

24 months

Advertising expense

$ 1,800

1,600

1,700

Accumulated deficit

$ 5,836

$ 8,833

$ 5,836

8,833

Roaming and other service revenues | Reclassification

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Revenues

$ 506

$ 449

Minimum

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Lessee leasing arrangements, operating leases, term of contract (years)

5 years

5 years

Option to extend lease term

5 years

Lessee leasing arrangements, finance leases, term of contract

2 years

2 years

Minimum | EIP Securitization Arrangement

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Equipment installment plan, maximum payment term

24 months

Maximum

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Lessee leasing arrangements, operating leases, term of contract (years)

15 years

15 years

Option to extend lease term

35 years

Lessee leasing arrangements, finance leases, term of contract

5 years

5 years

Accounting Standards Update 2016-13

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Allowance for credit losses

$ (91)

Deferred tax assets

24

Accumulated deficit

$ 67

Prepaid Business | T-Mobile and Sprint | DISH

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Payments for asset acquisition

$ 1,400

Sprint

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Exchange ratio (in shares) | shares

0.10256

Exchange ratio (in shares) | shares

9.75

Total term of agreement

30 years

Deferred tax assets

$ 848

Sprint | Minimum

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Agreements with educational and certain non-profit institutions, term

5 years

Sprint | Maximum

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Agreements with educational and certain non-profit institutions, term

10 years

Business Combination - Narrativ

Business Combination - Narrative (Details) - USD ($)	Apr. 01, 2020	Feb. 20, 2020	Feb. 01, 2021	Nov. 30, 2020	Jun. 30, 2021	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 09, 2020	Jan. 01, 2019
Business Acquisition [Line Items]
Goodwill							$ 11,117,000,000	$ 1,930,000,000
Payments of consent fees							$ 109,000,000	0	$ 0
Sprint
Business Acquisition [Line Items]
Exchange ratio (in shares)	9.75
Exchange ratio (in shares)	0.10256
Stock issued (in shares)	373,396,310
Value of common stock provided in exchange for acquiree common stock	$ 31,328,000,000
Fully-diluted shares of combined company held by public stockholders (percent)							31.70%
Value of contingent consideration	1,882,000,000
Contingent consideration, high end of range	7,300,000,000
Adjustment, property, plant and equipment							$ 1,200,000,000
Adjustment, other long-term liabilities							1,700,000,000
Deferred tax liabilities, adjustment							690,000,000
Deferred tax liabilities, reclassifications							357,000,000
Goodwill	9,401,000,000
Goodwill expected to be tax deductible	0
Spectrum licenses	45,400,000,000
Transaction costs							201,000,000	$ 106,000,000	$ 71,000,000
Transaction costs assumed to have occurred											$ 559,000,000
Total revenue subsequent to Merger date							20,500,000,000
Operating income subsequent to Merger date							$ 1,300,000,000
Total consideration exchanged	40,827,000,000
Sprint | Senior Notes
Business Acquisition [Line Items]
Payments for requisite consents to third-party note holders	95,000,000
Sprint | DT
Business Acquisition [Line Items]
Payments of consent fees						$ 7,000,000
Payments for requisite consents to DT	13,000,000
Sprint | Secured Term Loan Facility
Business Acquisition [Line Items]
Financing commitment, amount	4,000,000,000
Sprint | Secured Bridge Loan Facility
Business Acquisition [Line Items]
Financing commitment, amount	19,000,000,000									$ 19,000,000,000
Sprint | Secured and Unsecured Debt Financing
Business Acquisition [Line Items]
Payments of consent fees	355,000,000
Sprint | Accounts Receivable
Business Acquisition [Line Items]
Fair value of receivables acquired	1,800,000,000
Gross amounts due	1,800,000,000
Sprint | Equipment installment plan receivables, net of allowance for credit losses and imputed discount
Business Acquisition [Line Items]
Fair value of receivables acquired	1,300,000,000
Gross amounts due	1,600,000,000
Sprint | Customer relationships
Business Acquisition [Line Items]
Finite-lived, Fair Value (in millions)	$ 4,900,000,000
Weighted Average Useful Life (in years)	8 years
Sprint | Favorable lease (asset)
Business Acquisition [Line Items]
Finite-lived, Fair Value (in millions)	$ 790,000,000
Weighted Average Useful Life (in years)	18 years
Sprint | SoftBank
Business Acquisition [Line Items]
Fully-diluted shares expected to be held immediately following merger (percent)							24.70%
Settlement to resolve FCC's investigation				$ 200,000,000
Sprint | DT
Business Acquisition [Line Items]
Fully-diluted shares expected to be held immediately following merger (percent)							43.60%
Sprint | Common Stock
Business Acquisition [Line Items]
Exchange ratio (in shares)		11
Sprint | Common Stock | SoftBank
Business Acquisition [Line Items]
Aggregate surrendered (in shares)		48,751,557
Exchange ratio (in shares)		11.31
Volume-weighted average price (in USD per share)		$ 150
Number of shares issued if threshold not met (in shares)		0
Shentel | Subsequent Event | Scenario, Forecast
Business Acquisition [Line Items]
Asset value					$ 2,100,000,000
Purchase price, percent of assets					90.00%
Total consideration exchanged			$ 1,900,000,000		$ 1,900,000,000

Business Combination - Schedule

Business Combination - Schedule of Components of Consideration Transferred (Details) - USD ($) $ / shares in Units, $ in Millions	Apr. 01, 2020	Feb. 20, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2020
Business Acquisition [Line Items]
Payment received from selling shareholder			$ (5,000)	$ (31)	$ (338)
Share price at closing (in USD per share)						$ 83.90
Sprint
Business Acquisition [Line Items]
Fair value of T-Mobile common stock issued to Sprint stockholders	$ 31,328
Fair value of T-Mobile replacement equity awards attributable to pre-combination service	323
Repayments of Sprint's debt (including accrued interest, prepayment penalties)	7,396
Value of contingent consideration	1,882
Payment received from selling shareholder	(102)
Total consideration exchanged	$ 40,827
Stock issued (in shares)	373,396,310
Exchange ratio (in shares)	0.10256
Sprint | SoftBank | Common Stock Outstanding
Business Acquisition [Line Items]
Aggregate surrendered (in shares)		48,751,557

Business Combination - Schedu_2

Business Combination - Schedule of Amounts Recognized as of Acquisition Date (Details) - USD ($) $ in Millions	Apr. 01, 2020	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill		$ 11,117	$ 1,930
Sprint
Business Acquisition [Line Items]
Cash and cash equivalents	$ 2,084
Accounts receivable	1,781
Equipment installment plan receivables	1,088
Inventory	658
Prepaid expenses	140
Assets held for sale	1,908
Other current assets	631
Property and equipment	18,435
Operating lease right-of-use assets	6,583
Financing lease right-of-use assets	291
Goodwill	9,401
Spectrum licenses	45,400
Other intangible assets	6,325
Equipment installment plan receivables due after one year, net	247
Other assets	540
Total assets acquired	95,512
Accounts payable and accrued liabilities	4,944
Short-term debt	2,760
Deferred revenue	508
Short-term operating lease liabilities	1,818
Short-term financing lease liabilities	8
Liabilities held for sale	475
Other current liabilities	671
Long-term debt	29,037
Tower obligations	950
Deferred tax liabilities	3,513
Operating lease liabilities	5,615
Financing lease liabilities	12
Other long-term liabilities	4,374
Total liabilities assumed	54,685
Total consideration exchanged	40,827
Restricted cash	$ 80

Business Combination - Schedu_3

Business Combination - Schedule of Additional Detail on Receivables Acquired in Merger (Details) - Sprint $ in Billions	Apr. 01, 2020USD ($)
Accounts Receivable
Business Acquisition [Line Items]
Fair value of receivables acquired	$ 1.8
Gross amounts due	1.8
EIP Receivables
Business Acquisition [Line Items]
Fair value of receivables acquired	1.3
Gross amounts due	$ 1.6

Business Combination - Schedu_4

Business Combination - Schedule of Pro Forma Information (Details) - Sprint - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Total revenues	$ 74,681	$ 70,607
Income from continuing operations	3,302	185
Income from discontinued operations, net of tax	677	1,594
Net income	$ 3,979	$ 1,792

Receivables and Expected Cred_3

Receivables and Expected Credit Losses - EIP Receivables (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)classsegment	Jan. 01, 2020USD ($)	Dec. 31, 2019USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portfolio segments | segment	2
Customer classes | class	2
Total EIP Receivables, net of unamortized imputed discounts	$ 6,213		$ 4,582
Unamortized imputed discount	(325)		(299)
EIP receivables, net of unamortized imputed discount	5,888		4,283
Allowance for credit losses	(280)		(100)
Equipment installment plan receivables, net	5,608		4,183
Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjustment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses		$ (91)
Equipment installment plan receivables, net of allowance for credit losses and imputed discount
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equipment installment plan receivables, net	3,577		2,600
Equipment installment plan receivables due after one year, net of allowance for credit losses and imputed discount
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equipment installment plan receivables, net	$ 2,031		$ 1,583

Receivables and Expected Cred_4

Receivables and Expected Credit Losses - Gross EIP Receivables by Credit Category (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	$ 5,888	$ 4,283
Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	2,677
Originated in 2019	538
Originated prior to 2019	126
Total EIP Receivables, net of unamortized imputed discounts	3,341
Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	2,089
Originated in 2019	430
Originated prior to 2019	28
Total EIP Receivables, net of unamortized imputed discounts	2,547
Current - 30 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	5,774
Current - 30 days past due | Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	2,654
Originated in 2019	528
Originated prior to 2019	124
Total EIP Receivables, net of unamortized imputed discounts	3,306
Current - 30 days past due | Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	2,035
Originated in 2019	407
Originated prior to 2019	26
Total EIP Receivables, net of unamortized imputed discounts	2,468
31 - 60 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	65
31 - 60 days past due | Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	16
Originated in 2019	6
Originated prior to 2019	1
Total EIP Receivables, net of unamortized imputed discounts	23
31 - 60 days past due | Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	30
Originated in 2019	12
Originated prior to 2019	0
Total EIP Receivables, net of unamortized imputed discounts	42
61 - 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	24
61 - 90 days past due | Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	4
Originated in 2019	2
Originated prior to 2019	0
Total EIP Receivables, net of unamortized imputed discounts	6
61 - 90 days past due | Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	13
Originated in 2019	5
Originated prior to 2019	0
Total EIP Receivables, net of unamortized imputed discounts	18
More than 90 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total EIP Receivables, net of unamortized imputed discounts	25
More than 90 days past due | Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	3
Originated in 2019	2
Originated prior to 2019	1
Total EIP Receivables, net of unamortized imputed discounts	6
More than 90 days past due | Subprime
Financing Receivable, Credit Quality Indicator [Line Items]
Originated in 2020	11
Originated in 2019	6
Originated prior to 2019	2
Total EIP Receivables, net of unamortized imputed discounts	$ 19

Receivables and Expected Cred_5

Receivables and Expected Credit Losses - Unamortized Imputed Discount and Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	$ 460	$ 516	$ 482
Bad debt expense	602	307	297
Write-offs, net of recoveries	(380)	(332)	(328)
Change in imputed discount on short-term and long-term EIP receivables	171	136	250
Impact on the imputed discount from sales of EIP receivables	(145)	(167)	(185)
Allowance for credit losses and imputed discount, end of period	799	460	516
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	91
Allowance for credit losses and imputed discount, end of period		91
Accounts Receivable Allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	61	67	86
Bad debt expense	338	77	69
Write-offs, net of recoveries	(205)	(83)	(88)
Allowance for credit losses and imputed discount, end of period	194	61	67
Accounts Receivable Allowance | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	$ 0
Allowance for credit losses and imputed discount, end of period		$ 0
EIP Receivables Allowance
Financing Receivable, Allowance for Credit Loss [Line Items]
Weighted average effective imputed interest rate (percentage)	6.70%	8.80%
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	$ 399	$ 449	396
Bad debt expense	264	230	228
Write-offs, net of recoveries	(175)	(249)	(240)
Change in imputed discount on short-term and long-term EIP receivables	171	136	250
Impact on the imputed discount from sales of EIP receivables	(145)	(167)	(185)
Allowance for credit losses and imputed discount, end of period	605	399	$ 449
EIP Receivables Allowance | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses and imputed discount, beginning of period	$ 91
Allowance for credit losses and imputed discount, end of period		$ 91

Sales of Certain Receivables -

Sales of Certain Receivables - Sales of Service Receivables (Details) - USD ($)	Dec. 31, 2020	Apr. 01, 2020	Dec. 31, 2019	Dec. 31, 2014
Variable Interest Entity [Line Items]
Other current assets	$ 2,496,000,000		$ 1,972,000,000
Accounts payable and accrued liabilities	10,196,000,000		6,746,000,000
Other current liabilities	810,000,000		1,673,000,000
Factoring Arrangement | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Revolving receivables facility, maximum borrowing capacity				$ 950,000,000
Revolving receivables facility, outstanding borrowings	772,000,000		924,000,000
Other current assets	378,000,000		350,000,000
Accounts payable and accrued liabilities	0		25,000,000
Other current liabilities	$ 357,000,000		$ 342,000,000
Sprint | Accounts receivable facility
Variable Interest Entity [Line Items]
Total amount outstanding		$ 2,300,000,000

Sales of Certain Receivables _2

Sales of Certain Receivables - Sales of EIP Receivables (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2015
Variable Interest Entity [Line Items]
Other current assets	$ 2,496,000,000	$ 1,972,000,000
Other assets	2,779,000,000	1,891,000,000
EIP Securitization Arrangement
Variable Interest Entity [Line Items]
Revolving receivables facility, maximum borrowing capacity	1,300,000,000	1,300,000,000	$ 1,300,000,000
Other current assets	388,000,000	344,000,000
Other assets	120,000,000	89,000,000
Other long-term liabilities	$ 4,000,000	$ 18,000,000

Sales of Certain Receivables _3

Sales of Certain Receivables - Sales of Receivables and Continuing Involvement (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Other current assets	$ 2,496	$ 1,972
Other long-term assets	2,779	1,891
Accounts payable and accrued liabilities	10,196	6,746
Other current liabilities	810	1,673
Other long-term liabilities	5,412	954
Of which:
Losses from sales of receivables	36	130	$ 157
Factoring and EIP Securitization Arrangement | Variable Interest Entity, Primary Beneficiary
Of which:
Maximum exposure to loss, Factoring VIE	1,200
Factoring and EIP Securitization Arrangement | Variable Interest Entity, Primary Beneficiary
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Derecognized net service receivables and EIP receivables	2,528	2,584
Other current assets	766	694
Carrying amounts of deferred purchase price assets	884	781
Other long-term assets	120	89
Accounts payable and accrued liabilities	0	25
Other current liabilities	357	342
Other long-term liabilities	4	18
Net cash proceeds since inception	1,715	1,944
Of which:
Change in net cash proceeds during the year-to-date period	(229)	65
Net cash proceeds funded by reinvested collections	1,944	1,879
Losses from sales of receivables	36	130	$ 157
Factoring and EIP Securitization Arrangement | Other current assets - of which, deferred purchase price | Variable Interest Entity, Primary Beneficiary
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Carrying amounts of deferred purchase price assets	764	692
Factoring and EIP Securitization Arrangement | Other long-term assets - of which, deferred purchase price | Variable Interest Entity, Primary Beneficiary
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Carrying amounts of deferred purchase price assets	$ 120	$ 89

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (42,395)	$ (33,118)
Property and equipment, net	41,175	21,984
Depreciation expense	13,100	6,500	$ 6,400
Depreciation expense for lease devices	3,100	543	940
Capitalized interest	440	473	$ 362
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment	236	0
Buildings and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	4,006	2,587
Wireless communications systems
Property, Plant and Equipment [Line Items]
Property, plant and equipment	49,453	34,353
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,879	1,345
Capitalized software
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 16,412	12,705
Leased wireless devices
Property, Plant and Equipment [Line Items]
Useful life (in years)	8 months
Property, plant and equipment	$ 6,989	1,139
Accumulated depreciation and amortization	(2,170)	(407)
Property and equipment, net	4,819	732
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 4,595	$ 2,973
Maximum | Buildings and equipment
Property, Plant and Equipment [Line Items]
Useful life (in years)	30 years
Maximum | Wireless communications systems
Property, Plant and Equipment [Line Items]
Useful life (in years)	20 years
Maximum | Leasehold improvements
Property, Plant and Equipment [Line Items]
Useful life (in years)	12 years
Maximum | Capitalized software
Property, Plant and Equipment [Line Items]
Useful life (in years)	10 years
Maximum | Leased wireless devices
Property, Plant and Equipment [Line Items]
Useful life (in years)	19 months

Property and Equipment - Asset

Property and Equipment - Asset Retirement Obligation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligations, beginning of year	$ 659	$ 609
Fair value of liabilities acquired through Merger	1,110	0
Liabilities incurred	16	35
Liabilities settled	(40)	(2)
Accretion expense	55	32
Changes in estimated cash flows	17	(15)
Asset retirement obligations, end of period	1,817	659	$ 609
Asset retirement costs capitalized, net	912	159
Non-cash impairment related to capitalized software development costs	200	0	$ 0
Other long-term liabilities
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligations, beginning of year	659
Asset retirement obligations, end of period	1,803	659
Other current liabilities
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligations, beginning of year	0
Asset retirement obligations, end of period	$ 14	$ 0

Goodwill, Spectrum License Tr_3

Goodwill, Spectrum License Transactions and Other Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Millions	Apr. 01, 2020	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Historical goodwill, net of accumulated impairment losses of $10,766			$ 1,901
Beginning balance		$ 1,930
Layer3 goodwill impairment		(218)
Accumulated impairment losses		(10,984)	(10,766)
Ending balance		11,117	1,930
Layer3 TV
Goodwill [Roll Forward]
Goodwill from acquisition			$ 29
Sprint
Goodwill [Roll Forward]
Goodwill from acquisition	$ 9,400	$ 9,405
Ending balance	$ 9,401

Goodwill, Spectrum License Tr_4

Goodwill, Spectrum License Transactions and Other Intangible Assets - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 01, 2020
Goodwill [Line Items]
Goodwill impairment	$ 218,000,000
Goodwill	11,117,000,000	$ 1,930,000,000
Layer3 TV
Goodwill [Line Items]
Goodwill impairment	218,000,000	$ 0	$ 0
Goodwill	$ 0
Sprint
Goodwill [Line Items]
Goodwill				$ 9,401,000,000

Goodwill, Spectrum License Tr_5

Goodwill, Spectrum License Transactions and Other Intangible Assets - Schedule of Fair Value of Intangible Assets Acquired in Merger (Details) - USD ($) $ in Millions	Apr. 01, 2020	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Fixed period		15 years
Sprint
Finite-Lived Intangible Assets [Line Items]
Total intangible assets acquired	$ 51,725
Sprint | Tradenames
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	2 years
Finite-lived, Fair Value (in millions)	$ 207
Sprint | Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	8 years
Finite-lived, Fair Value (in millions)	$ 4,900
Sprint | Favorable spectrum leases
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	18 years
Finite-lived, Fair Value (in millions)	$ 790
Sprint | Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	7 years
Finite-lived, Fair Value (in millions)	$ 428
Sprint | Favorable lease (asset)
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	18 years
Finite-lived, Fair Value (in millions)	$ 790
Sprint | Unfavorable spectrum leases
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	19 years
Finite-lived, Fair Value (in millions)	$ 197
Sprint | Spectrum Licenses
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived, Fair Value (in millions)	$ 45,400
Fixed period	15 years

Goodwill, Spectrum License Tr_6

Goodwill, Spectrum License Transactions and Other Intangible Assets - Spectrum Licenses (Details) $ in Millions	Apr. 08, 2020USD ($)	Apr. 30, 2020USD ($)	Mar. 31, 2020USD ($)license	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Oct. 31, 2019USD ($)
Indefinite-lived Intangible Assets [Roll Forward]
Purchase of spectrum licenses				$ 1,333	$ 967	$ 127
Licensing Agreements
Indefinite-lived Intangible Assets [Roll Forward]
Beginning balance				36,465	35,559
Spectrum license acquisitions				1,023	857
Spectrum licenses transferred to held for sale				(83)	0
Costs to clear spectrum				23	49
Ending balance				82,828	36,465	$ 35,559
Loss from transfer to held-for-sale				35
Licensing Agreements | Auction 103
Indefinite-lived Intangible Assets [Roll Forward]
Number of licenses | license			2,384
Purchase of spectrum licenses	$ 698		$ 873
Incentive payments			59
Asset purchase deposit							$ 82
Down payment			$ 93
Licensing Agreements | Auction 103 | Sprint
Indefinite-lived Intangible Assets [Roll Forward]
Number of licenses | license			127
Sprint | Licensing Agreements
Indefinite-lived Intangible Assets [Roll Forward]
Spectrum license acquisitions				$ 45,400	$ 0
Sprint | Licensing Agreements | 800 MHz, 1.9 GHz and 2.5 GHz
Indefinite-lived Intangible Assets [Roll Forward]
Purchase of spectrum licenses		$ 45,400

Goodwill, Spectrum License Tr_7

Goodwill, Spectrum License Transactions and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 6,665	$ 1,527
Accumulated Amortization	(1,367)	(1,412)
Net Amount	5,298	115
Amortization expense for intangible assets	1,200	82	$ 124
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2021	1,246
2022	982
2023	827
2024	669
2025	511
Thereafter	1,063
Net Amount	5,298	115
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Amount	4,900	1,104
Accumulated Amortization	(865)	(1,104)
Net Amount	4,035	0
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Net Amount	$ 4,035	0
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, useful life (in years)	8 years
Tradenames and patents
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 598	323
Accumulated Amortization	(412)	(258)
Net Amount	186	65
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Net Amount	$ 186	65
Tradenames and patents | Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, useful life (in years)	19 years
Favorable spectrum leases
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 790	0
Accumulated Amortization	(35)	0
Net Amount	755	0
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Net Amount	$ 755	0
Favorable spectrum leases | Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, useful life (in years)	27 years
Other
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 377	100
Accumulated Amortization	(55)	(50)
Net Amount	322	50
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Net Amount	$ 322	$ 50
Other | Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, useful life (in years)	10 years

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 28, 2020	Oct. 06, 2020	Jun. 24, 2020	Apr. 09, 2020	Apr. 06, 2020	Oct. 31, 2018
Derivative [Line Items]
Net collateral transfers to certain derivative counterparties	$ (580,000,000)	$ (632,000,000)	$ (632,000,000)	$ 632,000,000	$ 0
Accumulated other comprehensive loss		868,000,000	1,581,000,000	868,000,000
Principal Issuances			54,750,000,000
Guarantee liabilities		62,000,000	50,000,000	62,000,000
Total EIP Receivables, net of unamortized imputed discounts		4,582,000,000	6,213,000,000	4,582,000,000
Interest Expense
Derivative [Line Items]
Amount amortized from AOCI into Interest expense			128,000,000	0	$ 0
Amount expected to be amortized from AOCI into interest expense over next 12 months			189,000,000
Equipment installment plan receivables, net of allowance for credit losses and imputed discount
Derivative [Line Items]
Total EIP Receivables, net of unamortized imputed discounts			3,400,000,000
Level 3 | Fair Value
Derivative [Line Items]
Carrying amounts of deferred purchase price assets		781,000,000	884,000,000	781,000,000
Senior Secured Notes due 2025, 3.500%
Derivative [Line Items]
Principal Issuances			3,000,000,000
Interest rate, stated percentage									3.50%
Senior Secured Notes due 2050, 4.500%
Derivative [Line Items]
Principal Issuances			$ 3,000,000,000
Interest rate, stated percentage									4.50%
Senior Notes
Derivative [Line Items]
Principal Issuances						$ 4,750,000,000	$ 4,000,000,000	$ 4,000,000,000	$ 19,000,000,000
Interest Rate Contract
Derivative [Line Items]
Derivative liabilities										$ 2,300,000,000
Cash-collateralized										$ 1,200,000,000
Interest Rate Contract | Cash Flow Hedging
Derivative [Line Items]
Aggregate notional amount											$ 9,600,000,000
Fair value of derivative instrument		$ 1,200,000,000		$ 1,200,000,000

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Short-term Investments and Long-term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Vendor Financing Arrangement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Term loans	$ 240	$ 25
Level 1 | Carrying Amount | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	29,966	10,958
Level 1 | Carrying Amount | Senior Notes | Third Party
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	36,204	0
Level 1 | Fair Value | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	32,450	11,479
Level 1 | Fair Value | Senior Notes | Third Party
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	40,519	0
Level 2 | Carrying Amount | Secured Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Term loans	0	4,000
Level 2 | Carrying Amount | Senior Notes | Affiliates
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	4,716	9,986
Level 2 | Fair Value | Secured Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Term loans	0	4,000
Level 2 | Fair Value | Senior Notes | Affiliates
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 4,991	$ 10,366

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Details) - USD ($) $ in Millions	Dec. 31, 2020	Oct. 28, 2020	Jul. 04, 2020	Apr. 01, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Unamortized premium	$ 2,197				$ 0
Unamortized discount	(197)				0
Debt issuance costs and consent fees	(244)				(46)
Long-term debt	71,125				24,969
Less: Current portion of Senior Notes and other debt to third parties	4,579				25
Total long-term debt	66,546				24,944
Long-term debt	61,830				10,958
Long-term debt to affiliates	4,716				13,986
Affiliates
Debt Instrument [Line Items]
Unamortized premium	0				43
Unamortized discount	(20)				(53)
Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360%
Debt Instrument [Line Items]
Long-term debt	$ 656				0
5.300% Senior Notes due 2021 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage	5.30%
Long-term debt	$ 0				2,000
Senior Notes due 2021, 7.250%
Debt Instrument [Line Items]
Long-term debt	2,250				0
Senior Notes due 2021, 11.500%
Debt Instrument [Line Items]
Long-term debt	$ 1,000				0
4.000% Senior Notes due 2022
Debt Instrument [Line Items]
Interest rate, stated percentage	4.00%
Long-term debt	$ 500				500
4.000% Senior Notes due 2022 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage	4.00%
Long-term debt	$ 1,000				1,000
Senior Notes due 2022, 6.000%
Debt Instrument [Line Items]
Long-term debt	2,280				0
Incremental term loan facility to affiliates due 2022 | Affiliates
Debt Instrument [Line Items]
Long-term debt	$ 0				2,000
6.000% Senior Notes due 2023
Debt Instrument [Line Items]
Interest rate, stated percentage	6.00%
Long-term debt	$ 1,300				1,300
Senior Notes due 2023, 7.875%
Debt Instrument [Line Items]
Long-term debt	$ 4,250				0
6.000% Senior Notes due 2024 [$1.0B]
Debt Instrument [Line Items]
Interest rate, stated percentage	6.00%
Long-term debt	$ 1,000				1,000
6.000% Senior Notes due 2024 [$1.35B] | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage	6.00%
Long-term debt	$ 0				1,350
6.000% Senior Notes due 2024 [$650M] | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage	6.00%
Long-term debt	$ 0				650
6.500% Senior Notes due 2024
Debt Instrument [Line Items]
Interest rate, stated percentage	6.50%
Long-term debt	$ 0				1,000
Senior Notes due 2024, 7.125%
Debt Instrument [Line Items]
Long-term debt	2,500				0
Incremental term loan facility to affiliates due 2024 | Affiliates
Debt Instrument [Line Items]
Long-term debt	$ 0				2,000
3.500% Senior Secured Notes due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage	3.50%
Long-term debt	$ 3,000				0
Senior Secured Series 2018-1 A-1 Notes due 2025, 4.738%
Debt Instrument [Line Items]
Long-term debt	$ 2,100				0
5.125% Senior Notes Due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage	5.125%
Long-term debt	$ 500				500
5.125% Senior Notes Due 2025 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage			5.125%
Long-term debt	$ 0				1,250
6.375% Senior Notes due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage	6.375%
Long-term debt	$ 0				1,700
Senior Notes due 2025, 7.625%
Debt Instrument [Line Items]
Long-term debt	$ 1,500				0
1.500% Senior Secured Notes due 2026
Debt Instrument [Line Items]
Interest rate, stated percentage	1.50%
Long-term debt	$ 1,000				0
6.500% Senior Notes due 2026
Debt Instrument [Line Items]
Interest rate, stated percentage	6.50%
Long-term debt	$ 2,000				2,000
Senior Notes due 2026, 4.500%
Debt Instrument [Line Items]
Interest rate, stated percentage	4.50%
Long-term debt	$ 1,000				1,000
Senior Notes due 2026, 4.500% | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage	4.50%
Long-term debt	$ 1,000				1,000
Senior Notes due 2026, 7.625%
Debt Instrument [Line Items]
Long-term debt	$ 1,500				0
3.750% Senior Secured Notes due 2027
Debt Instrument [Line Items]
Interest rate, stated percentage	3.75%
Long-term debt	$ 4,000				0
5.375% Senior Notes Due 2027
Debt Instrument [Line Items]
Interest rate, stated percentage	5.375%
Long-term debt	$ 500				500
5.375% Senior Notes Due 2027 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage	5.375%
Long-term debt	$ 1,250				1,250
2.050% Senior Secured Notes due 2028
Debt Instrument [Line Items]
Interest rate, stated percentage	2.05%
Long-term debt	$ 1,750				0
Senior Notes due 2028, 4.750%
Debt Instrument [Line Items]
Interest rate, stated percentage	4.75%
Long-term debt	$ 1,500				1,500
Senior Notes due 2028, 4.750% | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage	4.75%
Long-term debt	$ 1,500				1,500
Senior Secured Series 2018-1 A-2 Notes due 2028, 5.152%
Debt Instrument [Line Items]
Long-term debt	1,838				0
Senior Notes due 2028, 6.875%
Debt Instrument [Line Items]
Long-term debt	$ 2,475				0
3.875% Senior Secured Notes due 2030
Debt Instrument [Line Items]
Interest rate, stated percentage	3.875%
Long-term debt	$ 7,000				0
2.250% Senior Secured Notes due 2031
Debt Instrument [Line Items]
Interest rate, stated percentage	2.25%	2.25%
Long-term debt	$ 1,000				0
2.550% Senior Secured Notes due 2031
Debt Instrument [Line Items]
Interest rate, stated percentage	2.55%
Long-term debt	$ 2,500				0
Senior Notes due 2032, 8.750%
Debt Instrument [Line Items]
Long-term debt	$ 2,000				0
4.375% Senior Secured Notes due 2040
Debt Instrument [Line Items]
Interest rate, stated percentage	4.375%
Long-term debt	$ 2,000				0
3.000% Senior Secured Notes due 2041
Debt Instrument [Line Items]
Interest rate, stated percentage	3.00%
Long-term debt	$ 2,500				0
4.500% Senior Secured Notes due 2050
Debt Instrument [Line Items]
Interest rate, stated percentage	4.50%
Long-term debt	$ 3,000				0
3.300% Senior Secured Notes due 2051
Debt Instrument [Line Items]
Interest rate, stated percentage	3.30%
Long-term debt	$ 3,000				0
3.600% Senior Secured Notes due 2060
Debt Instrument [Line Items]
Interest rate, stated percentage	3.60%
Long-term debt	$ 1,000				0
Other Debt Obligations
Debt Instrument [Line Items]
Long-term debt	240				$ 25
Sprint
Debt Instrument [Line Items]
Long-term debt	$ 26,740
Sprint | Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360%
Debt Instrument [Line Items]
Interest rate, stated percentage				3.36%
Sprint | Senior Notes due 2021, 7.250%
Debt Instrument [Line Items]
Interest rate, stated percentage				7.25%
Sprint | Senior Notes due 2021, 11.500%
Debt Instrument [Line Items]
Interest rate, stated percentage	11.50%
Sprint | Senior Notes due 2022, 6.000%
Debt Instrument [Line Items]
Interest rate, stated percentage				6.00%
Sprint | Senior Notes due 2023, 7.875%
Debt Instrument [Line Items]
Interest rate, stated percentage				7.875%
Sprint | Senior Notes due 2024, 7.125%
Debt Instrument [Line Items]
Interest rate, stated percentage				7.125%
Sprint | Senior Secured Series 2018-1 A-1 Notes due 2025, 4.738%
Debt Instrument [Line Items]
Interest rate, stated percentage				4.738%
Sprint | Senior Notes due 2025, 7.625%
Debt Instrument [Line Items]
Interest rate, stated percentage				7.625%
Sprint | Senior Notes due 2026, 7.625%
Debt Instrument [Line Items]
Interest rate, stated percentage				7.625%
Sprint | Senior Secured Series 2018-1 A-2 Notes due 2028, 5.152%
Debt Instrument [Line Items]
Interest rate, stated percentage				5.152%
Sprint | Senior Notes due 2028, 6.875%
Debt Instrument [Line Items]
Interest rate, stated percentage				6.875%
Sprint | Senior Notes due 2032, 8.750%
Debt Instrument [Line Items]
Interest rate, stated percentage				8.75%

Debt - Issuances and Borrowings

Debt - Issuances and Borrowings (Details) - USD ($)	Oct. 28, 2020	Oct. 06, 2020	Dec. 31, 2020	Jun. 24, 2020	Apr. 09, 2020
Debt Instrument [Line Items]
Principal Issuances			$ 54,750,000,000
Premiums, Discounts and Issuance Costs			670,000,000
Net Proceeds from Issuance of Long-Term Debt	$ 4,600,000,000	$ 4,000,000,000	54,080,000,000
Senior Secured Notes due 2025, 3.500%
Debt Instrument [Line Items]
Interest rate, stated percentage					3.50%
Principal Issuances			3,000,000,000
Premiums, Discounts and Issuance Costs			12,000,000
Net Proceeds from Issuance of Long-Term Debt			$ 2,988,000,000
Senior Secured Notes due 2027, 3.750%
Debt Instrument [Line Items]
Interest rate, stated percentage			3.75%
Principal Issuances			$ 4,000,000,000
Premiums, Discounts and Issuance Costs			17,000,000
Net Proceeds from Issuance of Long-Term Debt			$ 3,983,000,000
Senior Secured Notes due 2030, 3.875%
Debt Instrument [Line Items]
Interest rate, stated percentage			3.875%
Principal Issuances			$ 7,000,000,000
Premiums, Discounts and Issuance Costs			78,000,000
Net Proceeds from Issuance of Long-Term Debt			$ 6,922,000,000
Senior Secured Notes due 2040, 4.375%
Debt Instrument [Line Items]
Interest rate, stated percentage			4.375%
Principal Issuances			$ 2,000,000,000
Premiums, Discounts and Issuance Costs			47,000,000
Net Proceeds from Issuance of Long-Term Debt			1,953,000,000
Senior Secured Notes due 2050, 4.500%
Debt Instrument [Line Items]
Interest rate, stated percentage					4.50%
Principal Issuances			3,000,000,000
Premiums, Discounts and Issuance Costs			24,000,000
Net Proceeds from Issuance of Long-Term Debt			2,976,000,000
Senior Notes due 2026, 1.500%
Debt Instrument [Line Items]
Interest rate, stated percentage				1.50%
Principal Issuances			1,000,000,000
Premiums, Discounts and Issuance Costs			5,000,000
Net Proceeds from Issuance of Long-Term Debt			$ 995,000,000
Senior Notes due 2028, 2.050%
Debt Instrument [Line Items]
Interest rate, stated percentage			2.05%
Principal Issuances			$ 1,250,000,000
Premiums, Discounts and Issuance Costs			8,000,000
Net Proceeds from Issuance of Long-Term Debt			1,242,000,000
Senior Notes due 2031, 2.550%
Debt Instrument [Line Items]
Interest rate, stated percentage				2.55%
Principal Issuances			1,750,000,000
Premiums, Discounts and Issuance Costs			12,000,000
Net Proceeds from Issuance of Long-Term Debt			1,738,000,000
Senior Notes due 2028, 2.050%, Issued October 6, 2020
Debt Instrument [Line Items]
Interest rate, stated percentage		2.05%
Principal Issuances			500,000,000
Premiums, Discounts and Issuance Costs			(11,000,000)
Net Proceeds from Issuance of Long-Term Debt			$ 511,000,000
Senior Notes due 2031, 2.550%, Issued October 6, 2020
Debt Instrument [Line Items]
Interest rate, stated percentage			2.55%
Principal Issuances			$ 750,000,000
Premiums, Discounts and Issuance Costs			(29,000,000)
Net Proceeds from Issuance of Long-Term Debt			$ 779,000,000
3.000% Senior Secured Notes due 2041
Debt Instrument [Line Items]
Interest rate, stated percentage			3.00%
Principal Issuances			$ 1,250,000,000
Premiums, Discounts and Issuance Costs			15,000,000
Net Proceeds from Issuance of Long-Term Debt			1,235,000,000
3.300% Senior Secured Notes due 2051
Debt Instrument [Line Items]
Interest rate, stated percentage		3.30%
Principal Issuances			1,500,000,000
Premiums, Discounts and Issuance Costs			16,000,000
Net Proceeds from Issuance of Long-Term Debt			$ 1,484,000,000
2.250% Senior Secured Notes due 2031
Debt Instrument [Line Items]
Interest rate, stated percentage	2.25%		2.25%
Principal Issuances			$ 1,000,000,000
Premiums, Discounts and Issuance Costs			5,000,000
Net Proceeds from Issuance of Long-Term Debt			$ 995,000,000
Senior Notes due 2041, 3.000%, Issued October 28, 2020
Debt Instrument [Line Items]
Interest rate, stated percentage			3.00%
Principal Issuances			$ 1,250,000,000
Premiums, Discounts and Issuance Costs			38,000,000
Net Proceeds from Issuance of Long-Term Debt			$ 1,212,000,000
Senior Notes due 2051, 3.300%, Issued October 28, 2020
Debt Instrument [Line Items]
Interest rate, stated percentage			3.30%
Principal Issuances			$ 1,500,000,000
Premiums, Discounts and Issuance Costs			58,000,000
Net Proceeds from Issuance of Long-Term Debt			1,442,000,000
3.600% Senior Secured Notes due 2060
Debt Instrument [Line Items]
Interest rate, stated percentage	3.60%
Principal Issuances			1,000,000,000
Premiums, Discounts and Issuance Costs			11,000,000
Net Proceeds from Issuance of Long-Term Debt			989,000,000
Senior Secured Notes Issued, Total
Debt Instrument [Line Items]
Principal Issuances			31,750,000,000
Premiums, Discounts and Issuance Costs			306,000,000
Net Proceeds from Issuance of Long-Term Debt			31,444,000,000
Secured Bridge Loan Facility | Bridge Loan
Debt Instrument [Line Items]
Principal Issuances			19,000,000,000
Premiums, Discounts and Issuance Costs			257,000,000
Net Proceeds from Issuance of Long-Term Debt			18,743,000,000
Secured Term Loan Facility due 2027
Debt Instrument [Line Items]
Principal Issuances			4,000,000,000
Premiums, Discounts and Issuance Costs			107,000,000
Net Proceeds from Issuance of Long-Term Debt			3,893,000,000
Secured Loan Facilities Issued, Total
Debt Instrument [Line Items]
Principal Issuances			23,000,000,000
Premiums, Discounts and Issuance Costs			364,000,000
Net Proceeds from Issuance of Long-Term Debt			$ 22,636,000,000

Debt - Credit Facility and Seni

Debt - Credit Facility and Senior Notes Narrative (Details)

Jan. 14, 2021USD ($)

Oct. 30, 2020USD ($)option

Oct. 28, 2020USD ($)

Oct. 06, 2020USD ($)

Apr. 09, 2020USD ($)

Apr. 01, 2020USD ($)

Jun. 30, 2018USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Sep. 16, 2020USD ($)

Jun. 24, 2020USD ($)

Mar. 31, 2018USD ($)

Debt Instrument [Line Items]

Effective interest rate

4.60%

5.20%

Average debt outstanding during period

$ 58,400,000,000

$ 25,500,000,000

Principal Issuances

54,750,000,000

Payments of consent fees

109,000,000

$ 0

$ 0

Proceeds from issuance of senior long-term debt

$ 4,600,000,000

$ 4,000,000,000

$ 54,080,000,000

Subsequent Event

Debt Instrument [Line Items]

Proceeds from issuance of senior long-term debt

$ 3,000,000,000

Line of Credit | Revolving Credit Facility

Debt Instrument [Line Items]

Financing commitment, amount

$ 5,500,000,000

Senior Notes

Debt Instrument [Line Items]

Principal Issuances

$ 4,750,000,000

$ 4,000,000,000

$ 19,000,000,000

$ 4,000,000,000

Proceeds from issuance of senior long-term debt

$ 18,800,000,000

Maximum interest increase

0.50%

Senior Notes | Subsequent Event

Debt Instrument [Line Items]

Principal Issuances

3,000,000,000

Senior Notes | Sprint

Debt Instrument [Line Items]

Principal Issuances

$ 3,900,000,000

Minimum | Senior Notes

Debt Instrument [Line Items]

Term preceding maturity date

1 month

Maximum | Senior Notes

Debt Instrument [Line Items]

Term preceding maturity date

6 months

5.300% Senior Notes due 2021 | Affiliates

Debt Instrument [Line Items]

Interest rate, stated percentage

5.30%

5.300% Senior Notes due 2021 | Senior Notes | Affiliates

Debt Instrument [Line Items]

Interest rate, stated percentage

5.30%

Guaranteed Notes due 2028 | Sprint

Debt Instrument [Line Items]

Interest rate, stated percentage

7.25%

Principal amount outstanding

$ 1,000,000,000

Senior Secured Term Loan Commitment

Debt Instrument [Line Items]

Principal Issuances

$ 5,000,000,000

Number of extension options | option

1

Extension term

6 months

Senior Secured Term Loan Commitment | Subsequent Event

Debt Instrument [Line Items]

Total outstanding obligation

2,000,000,000

Senior Secured Term Loan Commitment | LIBOR

Debt Instrument [Line Items]

Variable rate

1.25%

Senior Secured Notes due 2025, 3.500%

Debt Instrument [Line Items]

Principal Issuances

$ 3,000,000,000

Interest rate, stated percentage

3.50%

Proceeds from issuance of senior long-term debt

2,988,000,000

Senior Secured Notes due 2050, 4.500%

Debt Instrument [Line Items]

Principal Issuances

3,000,000,000

Interest rate, stated percentage

4.50%

Proceeds from issuance of senior long-term debt

2,976,000,000

Senior Notes due 2026, 1.500%

Debt Instrument [Line Items]

Principal Issuances

1,000,000,000

Interest rate, stated percentage

1.50%

Proceeds from issuance of senior long-term debt

995,000,000

Senior Notes due 2031, 2.550%

Debt Instrument [Line Items]

Principal Issuances

1,750,000,000

Interest rate, stated percentage

2.55%

Proceeds from issuance of senior long-term debt

1,738,000,000

Senior Notes due 2028, 2.050%, Issued October 6, 2020

Debt Instrument [Line Items]

Principal Issuances

500,000,000

Interest rate, stated percentage

2.05%

Proceeds from issuance of senior long-term debt

511,000,000

3.300% Senior Secured Notes due 2051

Debt Instrument [Line Items]

Principal Issuances

1,500,000,000

Interest rate, stated percentage

3.30%

Proceeds from issuance of senior long-term debt

1,484,000,000

2.250% Senior Secured Notes due 2031

Debt Instrument [Line Items]

Principal Issuances

$ 1,000,000,000

Interest rate, stated percentage

2.25%

2.25%

Proceeds from issuance of senior long-term debt

$ 995,000,000

3.600% Senior Secured Notes due 2060

Debt Instrument [Line Items]

Principal Issuances

1,000,000,000

Interest rate, stated percentage

3.60%

Proceeds from issuance of senior long-term debt

989,000,000

2.250% Senior Notes due 2026 | Subsequent Event

Debt Instrument [Line Items]

Principal Issuances

$ 1,000,000,000

Interest rate, stated percentage

2.25%

2.625% Senior Notes due 2029 | Subsequent Event

Debt Instrument [Line Items]

Principal Issuances

$ 1,000,000,000

Interest rate, stated percentage

2.625%

2.875% Senior Notes due 2031 | Subsequent Event

Debt Instrument [Line Items]

Principal Issuances

$ 1,000,000,000

Interest rate, stated percentage

2.875%

Sprint

Debt Instrument [Line Items]

Principal Issuances

24,605,000,000

Total outstanding obligation

4,600,000,000

Sprint | Senior Notes

Debt Instrument [Line Items]

Payments for requisite consents to third-party note holders

95,000,000

Sprint | DT

Debt Instrument [Line Items]

Payments of consent fees

$ 7,000,000

Sprint | DT | Senior Notes | Affiliates

Debt Instrument [Line Items]

Indebtedness to affiliates

4,000,000,000

Sprint | Secured Debt Financing

Debt Instrument [Line Items]

Financing commitment, amount

27,000,000,000

Proceeds from Lines of Credit

22,600,000,000

Sprint | Secured Revolving Credit Facility

Debt Instrument [Line Items]

Financing commitment, amount

$ 4,000,000,000

Sprint | Secured Revolving Credit Facility | LIBOR | Minimum

Debt Instrument [Line Items]

Variable rate

1.00%

Sprint | Secured Revolving Credit Facility | LIBOR | Maximum

Debt Instrument [Line Items]

Variable rate

1.25%

Sprint | Secured Term Loan Facility

Debt Instrument [Line Items]

Financing commitment, amount

$ 4,000,000,000

Net leverage ratio

0.75

Sprint | Secured Term Loan Facility | DT

Debt Instrument [Line Items]

Repayment of debt

$ 4,000,000,000

Sprint | Secured Term Loan Facility | LIBOR

Debt Instrument [Line Items]

Variable rate

3.00%

Sprint | Secured Bridge Loan Facility

Debt Instrument [Line Items]

Financing commitment, amount

$ 19,000,000,000

$ 19,000,000,000

Sprint | Secured Bridge Loan Facility | LIBOR

Debt Instrument [Line Items]

Variable rate

1.25%

Sprint | New Credit Agreement

Debt Instrument [Line Items]

Financial maintenance covenant

3.3

Sprint | 5.300% Senior Notes due 2021 | DT | Senior Notes

Debt Instrument [Line Items]

Principal Issuances

$ 2,000,000,000

Interest rate, stated percentage

5.30%

Sprint | 6.000% Senior Notes due 2024 | DT | Senior Notes

Debt Instrument [Line Items]

Principal Issuances

$ 2,000,000,000

Interest rate, stated percentage

6.00%

Sprint | Secured Term Loan due 2024

Debt Instrument [Line Items]

Principal amount outstanding

$ 5,900,000,000

Sprint | Accounts receivable facility

Debt Instrument [Line Items]

Principal Issuances

$ 0

Total amount outstanding

2,300,000,000

Sprint | Secured and Unsecured Debt Financing

Debt Instrument [Line Items]

Payments of consent fees

355,000,000

Sprint | Ratio Secured Debt Amendment | Senior Notes

Debt Instrument [Line Items]

Payments for requisite consents to third-party note holders

54,000,000

Sprint | Existing Sprint Spectrum Notes | Senior Notes

Debt Instrument [Line Items]

Payments for requisite consents to third-party note holders

$ 41,000,000

Debt - Debt Assumed (Details)

Debt - Debt Assumed (Details) - USD ($)	Dec. 31, 2020	Oct. 28, 2020	Oct. 06, 2020	Aug. 15, 2020	Jun. 24, 2020	Apr. 09, 2020	Apr. 01, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Principal Outstanding	$ 54,750,000,000
Carrying Value	71,125,000,000							$ 24,969,000,000
Sprint
Debt Instrument [Line Items]
Fair value							$ 31,797,000,000
Principal Outstanding	24,605,000,000
Carrying Value	$ 26,740,000,000
Senior Notes due 2021, 7.250% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							7.25%
Senior Notes due 2023, 7.875% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							7.875%
Senior Notes due 2024, 7.125% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							7.125%
Senior Notes due 2025, 7.625% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							7.625%
Senior Notes due 2026, 7.625% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							7.625%
Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							3.36%
Senior Secured Series 2018-1 A-1 Notes due 2025, 4.738% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							4.738%
Senior Secured Series 2018-1 A-2 Notes due 2028, 5.152% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							5.152%
Senior Notes due 2021, 11.500% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage	11.50%
Senior Notes due 2022, 6.000% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							6.00%
Senior Notes due 2028, 6.875% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							6.875%
Senior Notes due 2032, 8.750% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							8.75%
Accounts receivable facility | Sprint
Debt Instrument [Line Items]
Fair value							$ 2,310,000,000
Principal Outstanding	$ 0
Carrying Value	0
Other debt | Sprint
Debt Instrument [Line Items]
Fair value							464,000,000
Principal Outstanding	256,000,000
Carrying Value	240,000,000
Senior Notes
Debt Instrument [Line Items]
Principal Outstanding		$ 4,750,000,000	$ 4,000,000,000		$ 4,000,000,000	$ 19,000,000,000
Senior Notes | Senior Notes due 2021, 7.250% | Sprint
Debt Instrument [Line Items]
Fair value							2,324,000,000
Principal Outstanding	2,250,000,000
Carrying Value	2,287,000,000
Senior Notes | Senior Notes due 2023, 7.875% | Sprint
Debt Instrument [Line Items]
Fair value							4,682,000,000
Principal Outstanding	4,250,000,000
Carrying Value	4,594,000,000
Senior Notes | Senior Notes due 2024, 7.125% | Sprint
Debt Instrument [Line Items]
Fair value							2,746,000,000
Principal Outstanding	2,500,000,000
Carrying Value	2,706,000,000
Senior Notes | Senior Notes due 2025, 7.625% | Sprint
Debt Instrument [Line Items]
Fair value							1,677,000,000
Principal Outstanding	1,500,000,000
Carrying Value	1,652,000,000
Senior Notes | Senior Notes due 2026, 7.625% | Sprint
Debt Instrument [Line Items]
Fair value							1,701,000,000
Principal Outstanding	1,500,000,000
Carrying Value	$ 1,679,000,000
Senior Notes | Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360%
Debt Instrument [Line Items]
Interest rate, stated percentage	3.36%
Senior Notes | Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360% | Sprint
Debt Instrument [Line Items]
Fair value							1,310,000,000
Principal Outstanding	$ 656,000,000						3,500,000,000
Carrying Value	656,000,000
Senior Notes | Senior Secured Series 2018-1 A-1 Notes due 2025, 4.738% | Sprint
Debt Instrument [Line Items]
Fair value							2,153,000,000
Principal Outstanding	2,100,000,000
Carrying Value	2,145,000,000
Senior Notes | Senior Secured Series 2018-1 A-2 Notes due 2028, 5.152% | Sprint
Debt Instrument [Line Items]
Fair value							1,960,000,000
Principal Outstanding	1,838,000,000						$ 1,800,000,000
Carrying Value	1,950,000,000
Senior Notes | Senior Notes due 2020, 7.000%
Debt Instrument [Line Items]
Interest rate, stated percentage				7.00%
Senior Notes | Senior Notes due 2020, 7.000% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							7.00%
Fair value							$ 1,510,000,000
Principal Outstanding	0
Carrying Value	0
Senior Notes | Senior Notes due 2021, 11.500% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage							11.50%
Fair value							$ 1,105,000,000
Principal Outstanding	1,000,000,000
Carrying Value	1,057,000,000
Senior Notes | Senior Notes due 2022, 6.000% | Sprint
Debt Instrument [Line Items]
Fair value							2,372,000,000
Principal Outstanding	2,280,000,000
Carrying Value	2,346,000,000
Senior Notes | Senior Notes due 2028, 6.875% | Sprint
Debt Instrument [Line Items]
Fair value							2,834,000,000
Principal Outstanding	2,475,000,000
Carrying Value	2,808,000,000
Senior Notes | Senior Notes due 2032, 8.750% | Sprint
Debt Instrument [Line Items]
Fair value							$ 2,649,000,000
Principal Outstanding	2,000,000,000
Carrying Value	$ 2,620,000,000

Debt - Redemptions and Repaymen

Debt - Redemptions and Repayments (Details) - USD ($)	Sep. 01, 2020	Jul. 04, 2020	Apr. 09, 2020	Dec. 31, 2020	Aug. 15, 2020	Apr. 01, 2020
Debt Instrument [Line Items]
Principal Amount				$ 9,450,000,000
Principal Amount				30,447,000,000
Write off of Premiums, Discounts and Issuance Costs				10,000,000
Write off of Premiums, Discounts and Issuance Costs				351,000,000
Other				58,000,000
Other				(47,000,000)
Bridge Loan
Debt Instrument [Line Items]
Principal Amount				19,000,000,000
Write off of Premiums, Discounts and Issuance Costs				251,000,000
Other				$ (47,000,000)
6.500% Senior Notes due 2024
Debt Instrument [Line Items]
Interest rate, stated percentage				6.50%
6.375% Senior Notes due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage				6.375%
5.300% Senior Notes due 2021 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage				5.30%
5.125% Senior Notes Due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage				5.125%
5.125% Senior Notes Due 2025 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage		5.125%
Incremental term loan facility to affiliates due 2022 | Affiliates
Debt Instrument [Line Items]
Principal Amount				$ 2,000,000,000		$ 2,000,000,000
Write off of Premiums, Discounts and Issuance Costs				0
Other				$ 0
Redemption Price (as a percent)				1.00%
Incremental term loan facility to affiliates due 2024 | Affiliates
Debt Instrument [Line Items]
Principal Amount				$ 2,000,000,000		2,000,000,000
Write off of Premiums, Discounts and Issuance Costs				0
Other				$ 0
Redemption Price (as a percent)				1.00%
Accounts receivable facility
Debt Instrument [Line Items]
Principal Amount				$ 2,310,000,000
Write off of Premiums, Discounts and Issuance Costs				0
Other				$ 0
Redemption Price (as a percent)				1.00%
Secured Bridge Loan Facility
Debt Instrument [Line Items]
Other			$ 71,000,000
Secured Bridge Loan Facility | Sprint
Debt Instrument [Line Items]
Financing commitment, amount			$ 19,000,000,000			$ 19,000,000,000
Secured Bridge Loan Facility | Bridge Loan
Debt Instrument [Line Items]
Principal Amount				$ 19,000,000,000
Write off of Premiums, Discounts and Issuance Costs				251,000,000
Other				$ (47,000,000)
Redemption Price (as a percent)				1.00128%
Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage						3.36%
Secured Term Loan Facility due 2027
Debt Instrument [Line Items]
Principal Amount				$ 4,000,000,000
Write off of Premiums, Discounts and Issuance Costs				100,000,000
Other				$ 0
Redemption Price (as a percent)				1.00%
Other debt
Debt Instrument [Line Items]
Principal Amount				$ 481,000,000
Write off of Premiums, Discounts and Issuance Costs				0
Other				$ 0
Senior Notes | 6.500% Senior Notes due 2024
Debt Instrument [Line Items]
Interest rate, stated percentage		6.50%		6.50%
Principal Amount				$ 1,000,000,000
Principal Amount		$ 1,000,000,000
Write off of Premiums, Discounts and Issuance Costs				12,000,000
Other				$ 22,000,000
Redemption Price (as a percent)		102.167%		102.167%
Redemption premium		$ 22,000,000
Write-off of issuance costs		$ 12,000,000
Senior Notes | Senior Notes due 2020, 7.000%
Debt Instrument [Line Items]
Interest rate, stated percentage					7.00%
Principal Amount				$ 1,500,000,000
Principal Amount					$ 1,500,000,000
Write off of Premiums, Discounts and Issuance Costs				0
Other				$ 0
Senior Notes | Senior Notes due 2020, 7.000% | Sprint
Debt Instrument [Line Items]
Interest rate, stated percentage						7.00%
Senior Notes | 6.375% Senior Notes due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage	6.375%			6.375%
Principal Amount				$ 1,700,000,000
Principal Amount	$ 1,700,000,000
Write off of Premiums, Discounts and Issuance Costs				24,000,000
Other				$ 36,000,000
Redemption Price (as a percent)	102.125%			102.125%
Write-off of issuance costs	$ 24,000,000
Senior Notes | Total Senior Notes to third parties redeemed
Debt Instrument [Line Items]
Principal Amount				$ 4,200,000,000
Write off of Premiums, Discounts and Issuance Costs				36,000,000
Other				$ 58,000,000
Senior Notes | 5.300% Senior Notes due 2021 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage				5.30%
Principal Amount				$ 2,000,000,000
Write off of Premiums, Discounts and Issuance Costs				0
Other				$ 0
Redemption Price (as a percent)				100.00%
Senior Notes | 6.000% Senior Notes due 2024 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage				6.00%
Principal Amount				$ 1,350,000,000
Write off of Premiums, Discounts and Issuance Costs				(26,000,000)
Other				$ 0
Redemption Price (as a percent)				100.00%
Senior Notes | 6.000% Senior Notes due 2024 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage				6.00%
Principal Amount				$ 650,000,000
Write off of Premiums, Discounts and Issuance Costs				(15,000,000)
Other				$ 0
Redemption Price (as a percent)				100.00%
Senior Notes | 5.125% Senior Notes Due 2025 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage				5.125%
Principal Amount				$ 1,250,000,000
Write off of Premiums, Discounts and Issuance Costs				15,000,000
Other				$ 0
Redemption Price (as a percent)				100.00%
Senior Notes | Total Senior Notes to affiliates redeemed | Affiliates
Debt Instrument [Line Items]
Principal Amount				$ 5,250,000,000
Write off of Premiums, Discounts and Issuance Costs				(26,000,000)
Other				$ 0
Senior Notes | Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360%
Debt Instrument [Line Items]
Interest rate, stated percentage				3.36%
Principal Amount				$ 656,000,000
Write off of Premiums, Discounts and Issuance Costs				0
Other				$ 0

Debt - Financing Matters Agreem

Debt - Financing Matters Agreement, Senior Notes to Affiliates, Spectrum Financing and Consents on Debt to Third-Parties (Details)	Sep. 01, 2020USD ($)	Jul. 04, 2020USD ($)	Apr. 09, 2020USD ($)	Apr. 01, 2020USD ($)	May 18, 2018USD ($)	Dec. 31, 2020USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Oct. 28, 2020USD ($)	Oct. 06, 2020USD ($)	Aug. 15, 2020USD ($)	Jun. 24, 2020USD ($)	Mar. 31, 2018USD ($)note
Debt Instrument [Line Items]
Other								$ (47,000,000)
Principal Amount						$ 30,447,000,000		30,447,000,000
Payments of consent fees								109,000,000	$ 0	$ 0
Principal Issuances						54,750,000,000		54,750,000,000
Payments for third party bank fees								18,926,000,000	14,139,000,000	$ 13,161,000,000
Short-term debt						$ 4,579,000,000		$ 4,579,000,000	$ 25,000,000
Secured Bridge Loan Facility
Debt Instrument [Line Items]
Other			$ 71,000,000
6.500% Senior Notes due 2024
Debt Instrument [Line Items]
Interest rate, stated percentage						6.50%		6.50%
5.125% Senior Notes Due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage						5.125%		5.125%
5.125% Senior Notes Due 2025 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage		5.125%
6.375% Senior Notes due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage						6.375%		6.375%
Incremental term loan facility to affiliates due 2022 | Affiliates
Debt Instrument [Line Items]
Other								$ 0
Principal Amount				$ 2,000,000,000		$ 2,000,000,000		$ 2,000,000,000
Redemption Price (as a percent)								1.00%
Incremental term loan facility to affiliates due 2024 | Affiliates
Debt Instrument [Line Items]
Other								$ 0
Principal Amount				2,000,000,000		$ 2,000,000,000		$ 2,000,000,000
Redemption Price (as a percent)								1.00%
5.300% Senior Notes due 2021 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage						5.30%		5.30%
5.375% Senior Notes Due 2027
Debt Instrument [Line Items]
Interest rate, stated percentage						5.375%		5.375%
5.375% Senior Notes Due 2027 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage						5.375%		5.375%
Spectrum Financing SPEs
Debt Instrument [Line Items]
Lease payments (per month)				165,000,000
Senior Notes
Debt Instrument [Line Items]
Principal Issuances			19,000,000,000								$ 4,750,000,000	$ 4,000,000,000		$ 4,000,000,000
Senior Notes | 6.500% Senior Notes due 2024
Debt Instrument [Line Items]
Principal Amount		$ 1,000,000,000
Interest rate, stated percentage		6.50%				6.50%		6.50%
Redemption Price (as a percent)		102.167%						102.167%
Redemption premium		$ 22,000,000
Write-off of issuance costs		12,000,000
Senior Notes | 5.125% Senior Notes due 2021 | Affiliates
Debt Instrument [Line Items]
Principal Amount		$ 1,250,000,000
Interest rate, stated percentage		5.125%
Redemption Price (as a percent)		100.00%
Write-off of issuance costs		$ 15,000,000
Senior Notes | 5.125% Senior Notes Due 2025 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage						5.125%		5.125%
Redemption Price (as a percent)								100.00%
Senior Notes | Senior Notes due 2020, 7.000%
Debt Instrument [Line Items]
Principal Amount													$ 1,500,000,000
Interest rate, stated percentage													7.00%
Senior Notes | 6.375% Senior Notes due 2025
Debt Instrument [Line Items]
Principal Amount	$ 1,700,000,000
Interest rate, stated percentage	6.375%					6.375%		6.375%
Redemption Price (as a percent)	102.125%							102.125%
Write-off of issuance costs	$ 24,000,000
Senior Notes | 5.300% Senior Notes due 2021 | Affiliates
Debt Instrument [Line Items]
Interest rate, stated percentage						5.30%		5.30%
Redemption Price (as a percent)								100.00%
Senior Notes | Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360%
Debt Instrument [Line Items]
Other								$ 0
Principal Amount						$ 656,000,000		$ 656,000,000
Interest rate, stated percentage						3.36%		3.36%
Sprint
Debt Instrument [Line Items]
Principal Issuances						$ 24,605,000,000		$ 24,605,000,000
Notes issued and outstanding under Existing Sprint Spectrum Program (not exceed)					$ 7,000,000,000
Total outstanding obligation						4,600,000,000		4,600,000,000
Sprint | Credit Facilities
Debt Instrument [Line Items]
Financing commitment, amount					$ 9,000,000,000
Secured indebtedness, limit, percentage					150.00%
Secured debt to cash flow					2
Sprint | Secured Bridge Loan Facility
Debt Instrument [Line Items]
Financing commitment, amount			$ 19,000,000,000	19,000,000,000
Sprint | Secured Term Loan Facility
Debt Instrument [Line Items]
Financing commitment, amount				$ 4,000,000,000
Sprint | Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360%
Debt Instrument [Line Items]
Interest rate, stated percentage				3.36%
Sprint | Senior Secured Series 2018-1 A-1 Notes due 2025, 4.738%
Debt Instrument [Line Items]
Interest rate, stated percentage				4.738%
Short-term debt						394,000,000		394,000,000
Sprint | Senior Secured Series 2018-1 A-2 Notes due 2028, 5.152%
Debt Instrument [Line Items]
Interest rate, stated percentage				5.152%
Sprint | DT
Debt Instrument [Line Items]
Payments of consent fees							$ 7,000,000
Payments for requisite consents to DT				$ 13,000,000
Sprint | DT | Secured Term Loan Facility
Debt Instrument [Line Items]
Repayment of debt				4,000,000,000
Sprint | Senior Notes
Debt Instrument [Line Items]
Payments for third party bank fees							6,000,000
Payments for requisite consents to third-party note holders				$ 95,000,000
Sprint | Senior Notes | Long-term debt
Debt Instrument [Line Items]
Payments of consent fees							17,000,000
Sprint | Senior Notes | Senior Notes due 2020, 7.000%
Debt Instrument [Line Items]
Interest rate, stated percentage				7.00%
Principal Issuances						0		0
Sprint | Senior Notes | Existing Sprint Spectrum Notes
Debt Instrument [Line Items]
Payments for requisite consents to third-party note holders				$ 41,000,000
Sprint | Senior Notes | Existing Sprint Spectrum Notes | Long-term debt
Debt Instrument [Line Items]
Payments of consent fees							$ 14,000,000
Sprint | Senior Notes | Senior Secured Series 2016-1 A-1 Notes due 2021, 3.360%
Debt Instrument [Line Items]
Principal Issuances				3,500,000,000		656,000,000		656,000,000
Securitization program				$ 7,000,000,000
Payable term				5 years
Schedule principal repayments						656,000,000
Principal amount outstanding						656,000,000		656,000,000
Number of senior secured notes | note															2
Sprint | Senior Notes | Senior Secured Series 2018-1 A-1 Notes due 2025, 4.738%
Debt Instrument [Line Items]
Principal Issuances						2,100,000,000		2,100,000,000
Sprint | Senior Notes | Senior Secured Series 2018-1 A-2 Notes due 2028, 5.152%
Debt Instrument [Line Items]
Principal Issuances				$ 1,800,000,000		$ 1,838,000,000		$ 1,838,000,000
Sprint | Senior Notes | DT | Affiliates
Debt Instrument [Line Items]
Indebtedness to affiliates				$ 4,000,000,000
Sprint | Senior Notes | DT | 5.125% Senior Notes Due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage				5.125%
Principal Issuances				$ 1,250,000,000
Sprint | Senior Notes | DT | 5.300% Senior Notes due 2021
Debt Instrument [Line Items]
Interest rate, stated percentage				5.30%
Principal Issuances				$ 2,000,000,000
Sprint | Senior Notes | DT | 6.000% Senior Notes due 2024
Debt Instrument [Line Items]
Interest rate, stated percentage				6.00%
Principal Issuances				$ 2,000,000,000
Sprint | Senior Notes | DT | 5.375% Senior Notes Due 2027
Debt Instrument [Line Items]
Interest rate, stated percentage				5.375%
Principal Issuances				$ 1,250,000,000
Sprint | Senior Notes
Debt Instrument [Line Items]
Principal Issuances															$ 3,900,000,000

Debt - Standby Letters of Credi

Debt - Standby Letters of Credit (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Letters of credit, amount outstanding	$ 555	$ 113

Tower Obligations - Narrative (

Tower Obligations - Narrative (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020USD ($)tower_site	Dec. 31, 2020USD ($)tower_site	Dec. 31, 2012USD ($)tower_site	Apr. 01, 2020USD ($)
Sale Leaseback Transaction [Line Items]
Lease liabilities		$ 30,587
Sprint
Sale Leaseback Transaction [Line Items]
Property and equipment				$ 18,435
Adjustment, other long-term liabilities		$ 1,700
Crown Castle International Corp.
Sale Leaseback Transaction [Line Items]
Managed sites | tower_site		900
Lease liabilities		$ 282
Minimum
Sale Leaseback Transaction [Line Items]
Lessee leasing arrangements, operating leases, term of contract (years)		5 years
Maximum
Sale Leaseback Transaction [Line Items]
Lessee leasing arrangements, operating leases, term of contract (years)		15 years
Tower Transaction
Sale Leaseback Transaction [Line Items]
Number of wireless communications tower sites sold | tower_site			7,100
Lessee leasing arrangements, operating leases, term of contract (years)			10 years
Sale leaseback transaction, fixed-price purchase options			$ 2,000
Interest rate on tower obligations		6.00%	8.00%
Tower Transaction | Tower
Sale Leaseback Transaction [Line Items]
Useful life (in years)		20 years
Tower Transaction | Crown Castle International Corp.
Sale Leaseback Transaction [Line Items]
Property subject to failed sale leaseback transaction, number of units | tower_site	6,400
Remaining term of lease	17 years
Fixed-price purchase option on leased or subleased sites	$ 2,300
Fixed-price purchase option on lease or subleased sites, exercisable period	1 year
Days prior to expiration of agreement	120 days
Initial term	10 years
Property and equipment				2,800
Tower obligations				$ 1,100
Tower Transaction | Minimum
Sale Leaseback Transaction [Line Items]
Lessee leasing arrangements, operating leases, term of contract (years)			23 years
Tower Transaction | Maximum
Sale Leaseback Transaction [Line Items]
Lessee leasing arrangements, operating leases, term of contract (years)			37 years

Tower Obligations - Sale Leaseb

Tower Obligations - Sale Leaseback Transaction (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Property and equipment, net
Sale Leaseback Transaction [Line Items]
Failed sale-leasebacks	$ 2,838	$ 198
Failed Sale Leaseback Transaction, Tower Obligations
Sale Leaseback Transaction [Line Items]
Failed sale-leasebacks	3,028	2,236
Other Noncurrent Liabilities
Sale Leaseback Transaction [Line Items]
Failed sale-leasebacks	$ 1,712	$ 0

Tower Obligations - Future Mini

Tower Obligations - Future Minimum Payments (Details) $ in Millions	Dec. 31, 2020USD ($)
Leases [Abstract]
Tower obligation payments, due 2021	$ 397
Tower obligation payments, due 2022 and 2023	716
Tower obligation payment, due 2024 and 2025	598
Tower obligation payments due thereafter	$ 624

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 20,341	$ 19,272	$ 17,671	$ 11,113	$ 11,878	$ 11,061	$ 10,979	$ 11,080	$ 68,397	$ 44,998	$ 43,310
Postpaid phone revenues
Disaggregation of Revenue [Line Items]
Revenues									33,939	21,329	19,745
Postpaid other revenues
Disaggregation of Revenue [Line Items]
Revenues									2,367	1,344	1,117
Postpaid service revenues
Disaggregation of Revenue [Line Items]
Revenues									36,306	22,673	20,862
Wireless service revenues | Sprint
Disaggregation of Revenue [Line Items]
Revenues									626
Equipment revenues from the lease of mobile communication devices
Disaggregation of Revenue [Line Items]
Revenues									$ 4,181	$ 599	$ 692

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Contract Balances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Apr. 01, 2020
Disaggregation of Revenue [Line Items]
Contract Assets	$ 278	$ 63
Contract Liabilities	824	560
Change in contract assets included in other current assets	215
Change in contracts liabilities included in deferred revenue	264
Current portion of contract assets	204	50
Amounts included in the beginning of year contract liability balance	$ 545	$ 643
Sprint
Disaggregation of Revenue [Line Items]
Contract Assets			$ 154
Contract Liabilities			$ 336

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Remaining Performance Obligations, Branded Postpaid Contracts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Apr. 01, 2020
Postpaid service revenues
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 1,500
Remaining contract duration (in years)	24 months
Promotional bill credits | Sprint
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation		$ 1,000
Service performance obligations | Sprint
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 2,100	4,800
Lease performance obligation | Sprint
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 1,200	$ 2,600
Remaining contract duration (in years)	18 months
Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining contract duration (in years)	1 year
Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining contract duration (in years)	9 years

Revenue from Contracts with C_6

Revenue from Contracts with Customers - Remaining Performance Obligations (Details) $ in Millions	Dec. 31, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 1,300
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 1,100
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 317
Remaining performance obligation, expected timing of satisfaction, period

Revenue from Contracts with C_7

Revenue from Contracts with Customers - Contract Costs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Apr. 02, 2020
Disaggregation of Revenue [Line Items]
Deferred incremental costs to obtain contracts	$ 1,100,000,000	$ 906,000,000
Average amortization period, deferred contract costs (in months)	24 months
Amortization of deferred costs	$ 865,000,000	604,000,000
Contract Liabilities	824,000,000	560,000,000
Impairment losses recognized on deferred contract cost assets	$ 0	$ 0
Sprint
Disaggregation of Revenue [Line Items]
Contract Liabilities			$ 1,700,000,000

Employee Compensation and Ben_3

Employee Compensation and Benefit Plans - Narrative (Details)	12 Months Ended
	Dec. 31, 2020shares
Restricted Stock and Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	3 years
Performance Restricted Stock Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	3 years
2013 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance (in shares)	101,000,000
Number of shares available for future grants (in shares)	25,000,000

Employee Compensation and Ben_4

Employee Compensation and Benefit Plans - Schedule of Stock-based Compensation Expense and Related Income Tax Benefits (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 694	$ 495	$ 424
Income tax benefit related to stock-based compensation	$ 132	$ 92	$ 81
Restricted Stock Units and Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per stock award granted (in USD per share)	$ 96.27	$ 73.25	$ 61.52
Unrecognized compensation expense	$ 592	$ 515	$ 547
Weighted average period to be recognized (years)	1 year 10 months 24 days	1 year 7 months 6 days	1 year 9 months 18 days
Fair value of stock awards vested	$ 1,315	$ 512	$ 471

Employee Compensation and Ben_5

Employee Compensation and Benefit Plans - Stock Awards (Details) - Long-Term Stock Incentive Program - Common Stock Outstanding	Apr. 22, 2020shares
T-Mobile
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Shares of T-Mobile common stock issuable upon exercise or settlement (in shares)	7,043,843
Shares of common stock available for issuance (in shares)	12,420,945
Additional shares of T-Mobile common stock subject to awards granted (in shares)	5,839,436
Sprint
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Number of shares registered	25,304,224

Employee Compensation and Ben_6

Employee Compensation and Benefit Plans - Schedule of Restricted Stock and Unit Awards and Performance Restricted Stock Units Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Performance award achievement adjustments (in shares)	887,528
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Performance award achievement adjustments (in USD per share)	$ 70.96
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value [Abstract]
Taxes paid related to net share settlement of stock awards	$ 439	$ 156	$ 146
Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value [Abstract]
Share payout percentage	0.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value [Abstract]
Share payout percentage	200.00%
Restricted Stock and Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested, beginning (in shares)	10,503,211
Assumed through acquisition (in shares)	1,852,527
Granted (in shares)	5,891,303
Vested (in shares)	(7,112,552)
Forfeited (in shares)	(1,033,267)
Nonvested, ending (in shares)	10,101,222	10,503,211
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested, beginning (in USD per share)	$ 67.31
Assumed through acquisition (in USD per share)	83.90
Granted (in USD per share)	97.18
Vested (in USD per share)	69.32
Forfeited (in USD per share)	84.52
Nonvested, ending (in USD per share)	$ 84.61	$ 67.31
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Nonvested, Weighted Average Remaining Contractual Term, beginning (in years)	10 months 24 days	10 months 24 days
Nonvested, Weighted Average Remaining Contractual Term, ending (in years)	10 months 24 days	10 months 24 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value [Abstract]
Nonvested, Aggregate Intrinsic Value, beginning	$ 1,362	$ 824
Nonvested, Aggregate Intrinsic Value, ending	$ 1,362	$ 824
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested, beginning (in shares)	3,803,539
Assumed through acquisition (in shares)	3,535,384
Granted (in shares)	1,212,522
Vested (in shares)	(6,127,838)
Forfeited (in shares)	(138,034)
Nonvested, ending (in shares)	3,173,101	3,803,539
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested, beginning (in USD per share)	$ 69.78
Assumed through acquisition (in USD per share)	83.90
Granted (in USD per share)	110.38
Vested (in USD per share)	77.11
Forfeited (in USD per share)	83.90
Nonvested, ending (in USD per share)	$ 86.58	$ 69.78
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Nonvested, Weighted Average Remaining Contractual Term, beginning (in years)	1 year	1 year
Nonvested, Weighted Average Remaining Contractual Term, ending (in years)	1 year	1 year
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value [Abstract]
Nonvested, Aggregate Intrinsic Value, beginning	$ 428	$ 300
Nonvested, Aggregate Intrinsic Value, ending	$ 428	$ 300
Restricted Stock Units and Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Granted (in USD per share)	$ 96.27	$ 73.25	$ 61.52
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value [Abstract]
Shares paid for tax withholding for share based compensation (in shares)	4,441,107	2,094,555

Employee Compensation and Ben_7

Employee Compensation and Benefit Plans - Employee Stock Purchase Plan (Details) - shares	Jan. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Contribution percentage (up to)		15.00%
Stock purchase discount percentage		15.00%
ESPP, offering period		6 months
Number of securities remaining available for future sale and issuance under ESPP (in shares)		4,253,858
Aggregate number of shares, annual increase (in shares)		5,000,000
Additional shares of common stock (in shares)	5,000,000
Common Stock
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Number of shares issued under ESPP (in shares)		2,144,036	2,091,650	2,011,794

Employee Compensation and Ben_8

Employee Compensation and Benefit Plans - Stock Options (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Grant-date fair value of share-based incentive compensation awards	$ 163
Predecessor Plans
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding and exercisable, beginning (in shares)	194,942
Assumed through acquisition (in shares)	1,635,518
Exercised (in shares)	(906,295)
Expired/canceled (in shares)	(5,470)
Outstanding and exercisable, ending (in shares)	918,695	194,942
Exercisable (in shares)	917,955
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding and exercisable, beginning (usd per share)	$ 13.80
Assumed through acquisition (usd per share)	33.37
Exercised (usd per share)	53.02
Expired/canceled (usd per share)	49.75
Outstanding and exercisable, ending (usd per share)	51.77	$ 13.80
Exercisable (usd per share)	$ 51.79
Weighted Average Remaining Contractual Term (Years), Outstanding	4 years	2 years 10 months 24 days
Weighted Average Remaining Contractual Term (Years), Exercisable	4 years
Proceeds from exercise of stock options	$ 48	$ 1

Employee Compensation and Ben_9

Employee Compensation and Benefit Plans - Pension Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Apr. 01, 2020
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Expected long-term rate of return on plan assets	5.00%
Actual rate of return on plan assets during period	21.00%
Expected long-term rate of return on investments	4.00%
Interest on projected benefit obligations	$ 52
Expected return on pension plan assets	(45)
Net pension expense	$ 7
Percent at quoted price	12.00%
Percent at similar assets	85.00%
Percent supported at unobservable inputs	3.00%
Postretirement benefit plan assets	$ 1,400	$ 1,200
Projected benefit obligations	2,300	2,100
Underfunded plan	$ 828	$ 892
Discount rate	3.00%
Contributions to benefit plan	$ 58
Expected future contributions	89
Expected payment, year one	97
Expected payment, years two and three	198
Expected payment, years four and five	(206)
Expected payment, thereafter	$ 548
Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target allocation, percentage	24.00%
Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target allocation, percentage	17.00%
Fixed Income Securities [Member]
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target allocation, percentage	44.00%
Defined Benefit Plan, Real Estate [Member]
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target allocation, percentage	11.00%
Hedge Funds [Member]
Defined Benefit Plan, Plan Assets, Allocation [Line Items]
Target allocation, percentage	4.00%

Employee Compensation and Be_10

Employee Compensation and Benefit Plans - Employee Retirement Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement [Abstract]
Employer retirement savings plan, matching contributions	$ 179	$ 119	$ 102

Discontinued Operations - Narra

Discontinued Operations - Narrative (Details) $ in Millions	Jul. 01, 2020USD ($)
Prepaid Business | T-Mobile and Sprint | DISH
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments for asset acquisition	$ 1,400
Prepaid Business | T-Mobile and Sprint | DISH | Transition Services Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition period (up to)	3 years
Prepaid Business | T-Mobile and Sprint | DISH | Master Network Services Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition period (up to)	7 years
Prepaid Business | T-Mobile and Sprint | DISH | EIP Receivables
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments for asset acquisition	$ 162
Prepaid Business | DISH | EIP Receivables
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Participation interest	100.00%
Prepaid Business, Divested Net Assets | T-Mobile and Sprint | DISH
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments for asset acquisition	$ 1,200
Spectrum Licenses | T-Mobile and Sprint | DISH
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments for asset acquisition	$ 3,600
Additional lease period	2 years
Fee liability for failure to deliver the purchase price	$ 72
Decommissioned Towers and Retail Locations | DISH | T-Mobile and Sprint
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Option period (up to)	5 years

Discontinued Operations - Compo

Discontinued Operations - Components of Discontinued Operations from Merger Date (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations	$ 0	$ 0	$ 320	$ 0	$ 320	$ 0	$ 0
Net cash provided by operating activities from the Prepaid Business					611
Discontinued Operations, Disposed of by Sale | Prepaid Transaction
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Service revenues					1,270
Selling, general and administrative					314
Total operating expenses					838
Pretax income from discontinued operations					432
Income tax expense					(112)
Income from discontinued operations					320
Discontinued Operations, Disposed of by Sale | Prepaid Transaction | Prepaid revenues
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Service revenues					973
Discontinued Operations, Disposed of by Sale | Prepaid Transaction | Roaming and other services revenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Service revenues					27
Discontinued Operations, Disposed of by Sale | Prepaid Transaction | Service
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Service revenues					1,000
Cost of services and sales					25
Discontinued Operations, Disposed of by Sale | Prepaid Transaction | Equipment revenues
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Service revenues					270
Cost of services and sales					$ 499

Income Taxes - Income Tax Domes

Income Taxes - Income Tax Domestic and Foreign (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S.	$ 3,493	$ 4,557	$ 3,686
Foreign	37	46	231
Income from continuing operations before income taxes	$ 3,530	$ 4,603	$ 3,917

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current tax benefit (expense)
Federal	$ 17	$ 24	$ 39
State	(84)	(70)	(63)
Foreign	(10)	2	(25)
Total current tax expense	(77)	(44)	(49)
Deferred tax benefit (expense)
Federal	(676)	(954)	(750)
State	(34)	(125)	(160)
Foreign	1	(12)	(70)
Total deferred tax expense	(822)	(1,091)	(980)
Deferred income tax expense (benefit)	822	1,091	980
Total income tax expense	(786)	(1,135)	(1,029)
Continuing Operations
Deferred tax benefit (expense)
Total deferred tax expense	(709)	(1,091)	(980)
Deferred income tax expense (benefit)	$ 709	$ 1,091	$ 980

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%
Effect of law and rate changes	(0.80%)	0.40%	1.90%
Change in valuation allowance	(2.60%)	(1.80%)	(1.60%)
State taxes, net of federal benefit	4.80%	5.10%	4.80%
Foreign taxes, net of federal benefit	0.30%	0.30%	2.40%
Permanent differences	0.40%	0.60%	0.70%
Federal tax credits, net of reserves	(0.90%)	(0.80%)	(2.90%)
Equity-based compensation	(2.50%)	(0.60%)	(0.80%)
Non-deductible compensation	2.30%	0.60%	0.80%
Other, net	0.30%	(0.10%)	0.00%
Effective income tax rate	22.30%	24.70%	26.30%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Loss carryforwards	$ 4,540	$ 823
Lease liabilities	8,031	3,403
Property and equipment	90	0
Reserves and accruals	1,348	659
Federal and state tax credits	411	331
Other	2,665	903
Deferred tax assets, gross	17,085	6,119
Valuation allowance	(878)	(129)	$ (210)
Deferred tax assets, net	16,207	5,990
Deferred tax liabilities
Spectrum licenses	17,518	5,902
Property and equipment	0	2,506
Lease right-of-use assets	7,239	2,881
Other intangible assets	912	19
Other	504	289
Total deferred tax liabilities	26,173	11,597
Net deferred tax liabilities	$ 9,966	$ 5,607

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2020	Apr. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Indirect tax effects excluded	$ 144
Federal and state tax credits	411		$ 331
Uncertain tax benefit reserves	1,159		514	$ 462	$ 412
Valuation allowance	(878)		(129)	(210)
Unrecognized tax benefits that would impact effective tax rate	857		$ 310	$ 263
Sprint
Income Tax Contingency [Line Items]
Deferred tax assets		$ 848
Federal
Income Tax Contingency [Line Items]
Unrecognized tax benefits, net operating loss	3,500
Operating loss carryforwards	176
Federal | Research Tax Credit Carryforward
Income Tax Contingency [Line Items]
Federal and state tax credits	569
State
Income Tax Contingency [Line Items]
Unrecognized tax benefits, net operating loss	1,500
Operating loss carryforwards	455
Foreign Tax Authority
Income Tax Contingency [Line Items]
Unrecognized tax benefits, net operating loss	67
Operating loss carryforwards	$ 26

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning of year	$ 514	$ 462	$ 412
Gross increases to tax positions in prior periods	6	0	16
Gross decreases to tax positions in prior periods	(28)	0	(11)
Gross increases to current period tax positions	45	64	39
Gross increases due to current period business acquisitions	624	0	10
Gross decreases due to settlements with taxing authorities	(2)	(12)	(4)
Unrecognized tax benefits, end of year	$ 1,159	$ 514	$ 462

SoftBank Equity Transaction - N

SoftBank Equity Transaction - Narrative (Details) $ / shares in Units, shares in Millions, $ in Millions	Aug. 03, 2020	Jun. 26, 2020$ / sharesshares	Jun. 22, 2020USD ($)$ / sharesshares	Dec. 31, 2020USD ($)shares
Valuation, Income Approach
Subsidiary, Sale of Stock [Line Items]
Fair value of each call option, estimate | $				$ 1,000
Marcelo Claure
Subsidiary, Sale of Stock [Line Items]
Shares sold (in shares)				5
Rights Offering
Subsidiary, Sale of Stock [Line Items]
Price per share in public offering (in USD per share) | $ / shares		$ 103
Public Equity Offering
Subsidiary, Sale of Stock [Line Items]
Payment received to facilitate SoftBank Monetization | $			$ 304
Shares sold (in shares)		154.1
Public Equity Offering | Third-party trust
Subsidiary, Sale of Stock [Line Items]
Shares sold (in shares)		19.4
Rights Offering | Warrants and Rights Subject to Mandatory Redemption
Subsidiary, Sale of Stock [Line Items]
Conversion rate for option to purchase common stock		0.05
Additional paid-in capital
Subsidiary, Sale of Stock [Line Items]
Payment received to facilitate SoftBank Monetization | $				$ 304
Additional paid-in capital | Public Equity Offering
Subsidiary, Sale of Stock [Line Items]
Payment received, net of tax | $			$ 230
SoftBank
Subsidiary, Sale of Stock [Line Items]
Shares of common stock held by SoftBank (in shares)			198
Percentage of stock held	8.60%			8.60%
SoftBank | Direct and Indirect Call Option | DT
Subsidiary, Sale of Stock [Line Items]
Option to purchase shares (in shares) (up to)				101.5
SoftBank | Fixed-Price Call Option | DT
Subsidiary, Sale of Stock [Line Items]
Option to purchase shares (in shares) (up to)			44.9
Option to purchase shares (in USD per share) | $ / shares			$ 101.46
SoftBank | Floating-Price Call Option | DT
Subsidiary, Sale of Stock [Line Items]
Option to purchase shares (in shares) (up to)			56.6
Other Stockholders
Subsidiary, Sale of Stock [Line Items]
Percentage of stock held	48.00%			48.00%
DT
Subsidiary, Sale of Stock [Line Items]
Percentage of stock held	43.40%			43.40%
Voting control, percentage	52.40%			52.30%

Repurchases of Common Stock - N

Repurchases of Common Stock - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 06, 2017
Equity, Class of Treasury Stock [Line Items]
Aggregate market value of shares purchased		$ 19,536,000,000
Affiliates | DT
Equity, Class of Treasury Stock [Line Items]
Additional shares purchased (in shares)	3,300,000	0	0
Aggregate market value of shares purchased	$ 200,000,000
2017 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount				$ 1,500,000,000

Repurchases of Common Stock - S

Repurchases of Common Stock - Schedule of Repurchases of Common Stock (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Equity [Abstract]
Number of Shares Repurchased (in shares) | shares	16,738,758
Average Price Paid Per Share (usd per share) | $ / shares	$ 62.96
Total Purchase Price | $	$ 1,054

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Income from continuing operations	$ 750	$ 1,253	$ (210)	$ 951	$ 751	$ 870	$ 939	$ 908	$ 2,744	$ 3,468	$ 2,888
Income from discontinued operations, net of tax	0	0	320	0					320	0	0
Net income	$ 750	$ 1,253	$ 110	$ 951	$ 751	$ 870	$ 939	$ 908	$ 3,064	$ 3,468	$ 2,888
Weighted average shares outstanding - basic (in shares)	1,241,578,615	1,238,450,665	1,236,528,444	858,148,284	856,294,467	854,578,241	854,368,443	851,223,498	1,144,206,326	854,143,751	849,744,152
Effect of dilutive securities:
Outstanding stock options and unvested stock awards (in shares)									10,543,102	9,289,760	8,546,022
Weighted average shares outstanding - diluted (in shares)	1,251,566,899	1,249,798,740	1,236,528,444	865,998,532	864,158,739	862,690,751	860,135,593	858,643,481	1,154,749,428	863,433,511	858,290,174
Basic earnings per share:
Continuing operations (in USD per share)	$ 0.60	$ 1.01	$ (0.17)	$ 1.11					$ 2.40	$ 4.06	$ 3.40
Discontinued operations (in USD per share)	0	0	0.26	0					0.28	0	0
Basic (in USD per share)	0.60	1.01	0.09	1.11	$ 0.88	$ 1.02	$ 1.10	$ 1.07	2.68	4.06	3.40
Earnings Per Share, Diluted [Abstract]
Continuing operations (in USD per share)	0.60	1	(0.17)	1.10					2.37	4.02	3.36
Discontinued operations (in USD per share)	0	0	0.26	0					0.28	0	0
Diluted (in USD per share)	$ 0.60	$ 1	$ 0.09	$ 1.10	$ 0.87	$ 1.01	$ 1.09	$ 1.06	$ 2.65	$ 4.02	$ 3.36
Outstanding stock options and unvested stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)									80,180	16,359	148,422
SoftBank contingent consideration (1)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	48,751,557								36,630,268	0	0

Earnings Per Share - Narrative

Earnings Per Share - Narrative (Details) - $ / shares	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 01, 2020
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000	2,000,000,000		2,000,000,000
SoftBank contingent consideration (1)
Class of Stock [Line Items]
Potentially dilutive securities (in shares)	48,751,557	36,630,268	0	0
Mandatory Convertible Preferred Stock Series A
Class of Stock [Line Items]
Preferred shares authorized (in shares)	100,000,000	100,000,000
Preferred stock, par value (in USD per share)	$ 0.00001	$ 0.00001
Preferred shares outstanding (in shares)	0	0	0

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 14, 2020USD ($)tower_site
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 28,021	$ 10,933
Lease liabilities	30,587
Interest payments for financing leases	79	$ 82
Additional operating leases not yet commenced, payments due	$ 227
American Tower
Lessee, Lease, Description [Line Items]
Number of licensed towers | tower_site			20,729
Operating lease right-of-use assets			$ 11,000
Lease liabilities			$ 11,000

Leases - Schedule of Lease Expe

Leases - Schedule of Lease Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease expense	$ 4,438	$ 2,558
Financing lease expense:
Amortization of right-of-use assets	681	523
Interest on lease liabilities	81	82
Total financing lease expense	762	605
Variable lease expense	328	243
Total lease expense	$ 5,528	$ 3,406

Leases - Schedule of Informatio

Leases - Schedule of Information Related to Lease Term and Discount Rate (Details)	Dec. 31, 2020	Dec. 31, 2019
Weighted Average Remaining Lease Term (Years)
Operating leases	10 years	6 years
Financing leases	3 years	3 years
Weighted Average Discount Rate
Operating leases	3.90%	4.80%
Financing leases	3.30%	4.00%

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Operating and Finance Lease Maturities (Details) $ in Millions	Dec. 31, 2020USD ($)
Operating Leases
2021	$ 4,903
2022	4,354
2023	3,759
2024	3,339
2025	2,807
Thereafter	18,940
Total lease payments	38,102
Less: imputed interest	7,515
Total	30,587
Finance Leases
2021	1,121
2022	795
2023	422
2024	137
2025	92
Thereafter	61
Total lease payments	2,628
Less: imputed interest	121
Total	$ 2,507

Leases - Leased Wireless Device

Leases - Leased Wireless Devices (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Apr. 01, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Accumulated depreciation	$ (42,395)		$ (33,118)
Property and equipment, net	$ 41,175		21,984
Leased wireless devices
Property, Plant and Equipment [Line Items]
Useful life (in years)	8 months
Property, plant and equipment	$ 6,989		1,139
Accumulated depreciation	(2,170)		(407)
Property and equipment, net	$ 4,819		$ 732
Leased wireless devices | Sprint
Property, Plant and Equipment [Line Items]
Property and equipment, net		$ 5,800

Leases - Schedule of Future M_2

Leases - Schedule of Future Minimum Payments Expected to be Received (under 842) (Details) $ in Millions	Dec. 31, 2020USD ($)
Leases [Abstract]
2021	$ 1,687
2022	92
Total	$ 1,779

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Operating Leased Assets [Line Items]
Purchase commitment, due 2021	$ 5,000
Purchase commitment, due 2022 and 2023	4,500
Purchase commitment, due 2024 and 2025	2,400
Purchase commitment, due thereafter	1,700
Lease and service credit commitment, due 2021	338
Lease and service credit commitment, due 2022 and 2023	675
Lease and service credit commitment, due 2024 and 2025	594
Lease and service credit commitment, due thereafter	5,100
Maximum remaining commitment	92
Merger commitment, due 2021	23
Merger commitment, due in 2022 and 2023	37
Merger commitment, due in 2024 and 2025	$ 13
Minimum
Operating Leased Assets [Line Items]
Commitment term	15 years
Maximum
Operating Leased Assets [Line Items]
Commitment term	30 years

Restructuring Costs - Restructu

Restructuring Costs - Restructuring Plan Expenses Incurred (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 1,060	$ 1,060
Contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	178	178
Severance costs
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	385	385
Network decommissioning
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 497	$ 497

Restructuring Costs - Narrative

Restructuring Costs - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Restructuring and Related Activities [Abstract]
Amortization of the right-of-use assets on lease contracts	$ 153
Restructuring Term	3 years

Restructuring Costs - Activity

Restructuring Costs - Activity Related to Expenses Incurred and Cash Payments Made (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	$ 0
Expenses Incurred	1,060	$ 1,060
Cash Payments	(738)
Adjustments	(159)
Restructuring Reserve, Ending Balance	163	163
Contract termination costs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	0
Expenses Incurred	178	178
Cash Payments	(96)
Adjustments	(1)
Restructuring Reserve, Ending Balance	81	81
Severance costs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	0
Expenses Incurred	385	385
Cash Payments	(239)
Adjustments	(94)
Restructuring Reserve, Ending Balance	52	52
Network decommissioning
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	0
Expenses Incurred	497	497
Cash Payments	(403)
Adjustments	(64)
Restructuring Reserve, Ending Balance	$ 30	$ 30

Additional Financial Informat_3

Additional Financial Information - Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Supplemental Financial Statement Elements [Abstract]
Accounts payable	$ 5,564	$ 4,322
Payroll and related benefits	1,163	802
Property and other taxes, including payroll	1,540	682
Interest	771	227
Commissions	399	251
Toll and interconnect	217	156
Advertising	135	127
Other	407	179
Accounts payable and accrued liabilities	10,196	6,746
Accounts Payable and Accrued Liabilities
Accounts Payable and Accrued Liabilities [Line Items]
Outstanding checks	$ 628	$ 463

Additional Financial Informat_4

Additional Financial Information - Related Party Transactions (Details) - USD ($)	Apr. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 28, 2020	Oct. 06, 2020	Jul. 04, 2020	Jun. 24, 2020	Apr. 09, 2020
Related Party Transaction [Line Items]
Principal Amount		$ 30,447,000,000
Principal Issuances		54,750,000,000
Senior Notes
Related Party Transaction [Line Items]
Principal Issuances					$ 4,750,000,000	$ 4,000,000,000		$ 4,000,000,000	$ 19,000,000,000
Sprint
Related Party Transaction [Line Items]
Principal Issuances		24,605,000,000
DT | Sprint
Related Party Transaction [Line Items]
Payments for requisite consents to DT	$ 13,000,000
Affiliates
Related Party Transaction [Line Items]
Discount related to roaming expenses		(5,000,000)	$ (9,000,000)	$ 0
Fees incurred for use of the T-Mobile brand		83,000,000	88,000,000	84,000,000
International long distance agreement		47,000,000	39,000,000	36,000,000
Reimbursement of certain administrative expenses		6,000,000	$ 11,000,000	$ 11,000,000
Affiliates | DT | Sprint | Senior Notes
Related Party Transaction [Line Items]
Indebtedness to affiliates	4,000,000,000
Secured Term Loan Facility | DT | Sprint
Related Party Transaction [Line Items]
Repayments of Debt	4,000,000,000
Incremental term loan facility to affiliates due 2022 | Affiliates
Related Party Transaction [Line Items]
Principal Amount	2,000,000,000	2,000,000,000
Incremental term loan facility to affiliates due 2024 | Affiliates
Related Party Transaction [Line Items]
Principal Amount	2,000,000,000	$ 2,000,000,000
5.300% Senior Notes due 2021 | DT | Sprint | Senior Notes
Related Party Transaction [Line Items]
Principal Issuances	$ 2,000,000,000
Interest rate, stated percentage	5.30%
5.300% Senior Notes due 2021 | Affiliates
Related Party Transaction [Line Items]
Interest rate, stated percentage		5.30%
5.300% Senior Notes due 2021 | Affiliates | Senior Notes
Related Party Transaction [Line Items]
Interest rate, stated percentage		5.30%
6.000% Senior Notes due 2024 | DT | Sprint | Senior Notes
Related Party Transaction [Line Items]
Principal Issuances	$ 2,000,000,000
Interest rate, stated percentage	6.00%
5.125% Senior Notes Due 2025
Related Party Transaction [Line Items]
Interest rate, stated percentage		5.125%
5.125% Senior Notes Due 2025 | DT | Sprint | Senior Notes
Related Party Transaction [Line Items]
Principal Issuances	$ 1,250,000,000
Interest rate, stated percentage	5.125%
5.125% Senior Notes Due 2025 | Affiliates
Related Party Transaction [Line Items]
Interest rate, stated percentage							5.125%
5.125% Senior Notes Due 2025 | Affiliates | Senior Notes
Related Party Transaction [Line Items]
Interest rate, stated percentage		5.125%
5.375% Senior Notes Due 2027
Related Party Transaction [Line Items]
Interest rate, stated percentage		5.375%
5.375% Senior Notes Due 2027 | DT | Sprint | Senior Notes
Related Party Transaction [Line Items]
Principal Issuances	$ 1,250,000,000
Interest rate, stated percentage	5.375%
5.375% Senior Notes Due 2027 | Affiliates
Related Party Transaction [Line Items]
Interest rate, stated percentage		5.375%
5.125% Senior Notes due 2021 | Affiliates | Senior Notes
Related Party Transaction [Line Items]
Principal Amount							$ 1,250,000,000
Interest rate, stated percentage							5.125%

Additional Financial Informat_5

Additional Financial Information - Additional Information (Details) - shares	Aug. 03, 2020	Dec. 31, 2020
DT
Related Party Transaction [Line Items]
Percentage of stock held	43.40%	43.40%
Voting control, percentage	52.40%	52.30%
SoftBank
Related Party Transaction [Line Items]
Percentage of stock held	8.60%	8.60%
SoftBank | DT | Direct and Indirect Call Option
Related Party Transaction [Line Items]
Option to purchase shares (in shares) (up to)		101,500,000
Other Stockholders
Related Party Transaction [Line Items]
Percentage of stock held	48.00%	48.00%
Warrants and Rights Subject to Mandatory Redemption | Rights Offering
Related Party Transaction [Line Items]
Option to purchase common stock (in shares) (up to)	19,750,000

Additional Financial Informat_6

Additional Financial Information - Supplemental Consolidated Statements of Cash Flows Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transactions [Abstract]
Interest payments, net of amounts capitalized	$ 2,733	$ 1,128	$ 1,525
Operating lease payments	4,619	2,783	0
Income tax payments	218	88	51
Non-cash investing and financing activities
Non-cash beneficial interest obtained in exchange for securitized receivables	6,194	6,509	4,972
Non-cash consideration for the acquisition of Sprint	33,533	0	0
Change in accounts payable and accrued liabilities for purchases of property and equipment	589	(935)	65
Leased devices transferred from inventory to property and equipment	2,795	1,006	1,011
Returned leased devices transferred from property and equipment to inventory	(1,460)	(267)	(326)
Short-term debt assumed for financing of property and equipment	38	800	291
Operating lease right-of-use assets obtained in exchange for lease obligations	14,129	3,621	0
Financing lease right-of-use assets obtained in exchange for lease obligations	$ 1,273	$ 1,041	$ 885

Subsequent Events - Narrative (

Subsequent Events - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended
	Feb. 01, 2021	Jun. 30, 2021	Jan. 14, 2021	Dec. 31, 2020	Oct. 30, 2020	Oct. 28, 2020	Oct. 06, 2020	Jun. 24, 2020	Apr. 09, 2020
Subsequent Event [Line Items]
Principal Issuances				$ 54,750,000,000
Senior Notes
Subsequent Event [Line Items]
Principal Issuances						$ 4,750,000,000	$ 4,000,000,000	$ 4,000,000,000	$ 19,000,000,000
Senior Secured Term Loan Commitment
Subsequent Event [Line Items]
Principal Issuances					$ 5,000,000,000
Subsequent Event | Senior Notes
Subsequent Event [Line Items]
Principal Issuances			$ 3,000,000,000
Subsequent Event | Scenario, Forecast | Shentel
Subsequent Event [Line Items]
Total consideration exchanged	$ 1,900,000,000	$ 1,900,000,000
Subsequent Event | Senior Secured Term Loan Commitment
Subsequent Event [Line Items]
Total outstanding obligation			$ 2,000,000,000

Quarterly Financial Informati_3

Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information [Abstract]
Total revenues	$ 20,341	$ 19,272	$ 17,671	$ 11,113	$ 11,878	$ 11,061	$ 10,979	$ 11,080	$ 68,397	$ 44,998	$ 43,310
Operating income	1,712	2,565	820	1,539	1,234	1,471	1,541	1,476	6,636	5,722	5,309
Income from continuing operations	750	1,253	(210)	951	751	870	939	908	2,744	3,468	2,888
Income from discontinued operations, net of tax	0	0	320	0					320	0	0
Net income	$ 750	$ 1,253	$ 110	$ 951	$ 751	$ 870	$ 939	$ 908	$ 3,064	$ 3,468	$ 2,888
Earnings Per Share, Basic [Abstract]
Continuing operations (in USD per share)	$ 0.60	$ 1.01	$ (0.17)	$ 1.11					$ 2.40	$ 4.06	$ 3.40
Discontinued operations (in USD per share)	0	0	0.26	0					0.28	0	0
Earnings per share - basic (in USD per share)	0.60	1.01	0.09	1.11	$ 0.88	$ 1.02	$ 1.10	$ 1.07	2.68	4.06	3.40
Earnings Per Share, Diluted [Abstract]
Continuing operations (in USD per share)	0.60	1	(0.17)	1.10					2.37	4.02	3.36
Discontinued operations (in USD per share)	0	0	0.26	0					0.28	0	0
Earnings per share - diluted (in USD per share)	$ 0.60	$ 1	$ 0.09	$ 1.10	$ 0.87	$ 1.01	$ 1.09	$ 1.06	$ 2.65	$ 4.02	$ 3.36
Weighted average shares outstanding - basic (in shares)	1,241,578,615	1,238,450,665	1,236,528,444	858,148,284	856,294,467	854,578,241	854,368,443	851,223,498	1,144,206,326	854,143,751	849,744,152
Weighted average shares outstanding - diluted (in shares)	1,251,566,899	1,249,798,740	1,236,528,444	865,998,532	864,158,739	862,690,751	860,135,593	858,643,481	1,154,749,428	863,433,511	858,290,174