Business Combination, Required Fees by Acquirer, Accrued Amount

No definition available.

Name:	tmus_BusinessCombinationRequiredFeesByAcquirerAccruedAmount
Namespace Prefix:	tmus_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Business Combination, Required Financing Fees by Acquirer to Affiliate Upon Consummation

+ References

No definition available.

+ Details

Name:	tmus_BusinessCombinationRequiredFinancingFeesByAcquirerToAffiliateUponConsummation
Namespace Prefix:	tmus_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Business Combination, Required Financing Fees by Acquirer to Third Party Note Holders Upon Consummation

+ References

No definition available.

+ Details

Name:	tmus_BusinessCombinationRequiredFinancingFeesByAcquirerToThirdPartyNoteHoldersUponConsummation
Namespace Prefix:	tmus_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line of Credit Facility, Secured Indebtedness, Limit, Percentage

+ References

No definition available.

+ Details

Name:	tmus_LineofCreditFacilitySecuredIndebtednessLimitPercentage
Namespace Prefix:	tmus_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Notes Issued and Outstanding, Principal Amount

+ References

No definition available.

+ Details

Name:	tmus_NotesIssuedandOutstandingPrincipalAmount
Namespace Prefix:	tmus_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Secured Debt to Cash Flow, Ratio

+ References

No definition available.

+ Details

Name:	tmus_SecuredDebttoCashFlowRatio
Namespace Prefix:	tmus_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow for loan and debt issuance costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfFinancingCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=68048583&loc=d3e3636-108311

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.4)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

Name:	us-gaap_SellingGeneralAndAdministrativeExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmus_SeniorNotesDue20255.125Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmus_SeniorNotesDue20275.375Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=tmus_SprintCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=tmus_CreditFacilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_LongTermDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmus_ExistingSprintSpectrumNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=tmus_DeutscheTelekomAGMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmus_A5.300SeniorNotesdue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tmus_SeniorNotesdue20246.000Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt - Debt to Affiliates - Financing Matters Agreement and Consents on Debt to Third-Parties (Details) - USD ($)			3 Months Ended	12 Months Ended
	May 18, 2018	Apr. 29, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Payments for third party bank fees				$ 14,139,000,000	$ 13,161,000,000	$ 12,259,000,000
Senior Notes \| 5.125% Senior Notes Due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage				512.50%
Senior Notes \| 5.375% Senior Notes Due 2027
Debt Instrument [Line Items]
Interest rate, stated percentage				537.50%
Sprint
Debt Instrument [Line Items]
Required fees by acquirer upon consummation				$ 0
Notes issued and outstanding under Existing Sprint Spectrum Program (not exceed)	$ 7,000,000,000.0
Sprint \| Credit Facilities
Debt Instrument [Line Items]
Financing commitment, amount	$ 9,000,000,000.0
Secured indebtedness, limit, percentage	150.00%
Secured debt to cash flow	2.00
Sprint \| Senior Notes
Debt Instrument [Line Items]
Payments of consent fees				$ 242,000,000
Payments for third party bank fees			$ 6,000,000
Payments for requisite consents to third-party note holders	$ 95,000,000		54,000,000
Sprint \| Senior Notes \| Long-term debt
Debt Instrument [Line Items]
Payments of consent fees			17,000,000
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 \| Deutsche Telekom AG
Debt Instrument [Line Items]
Payments of consent fees			$ 7,000,000
Payments for requisite consents to DT		$ 13,000,000
Sprint \| Deutsche Telekom AG \| Senior Notes \| 5.300% Senior Notes to affiliates due 2021
Debt Instrument [Line Items]
Repayment of debt		$ 2,000,000,000.0
Interest rate, stated percentage		5.30%
Sprint \| Deutsche Telekom AG \| Senior Notes \| 6.000% Senior Notes due 2024
Debt Instrument [Line Items]
Repayment of debt		$ 2,000,000,000.0
Interest rate, stated percentage		6.00%
Sprint \| Deutsche Telekom AG \| Senior Notes \| 5.125% Senior Notes Due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage		5.125%
Debt instrument, face amount		$ 1,250,000,000
Sprint \| Deutsche Telekom AG \| Senior Notes \| 5.375% Senior Notes Due 2027
Debt Instrument [Line Items]
Interest rate, stated percentage		5.375%
Debt instrument, face amount		$ 1,250,000,000