Debt Instrument, Average Amount Outstanding During Period

No definition available.

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

- Definition

Debt Instrument, Redemption Premium

+ References

No definition available.

+ Details

Name:	tmus_DebtInstrumentRedemptionPremium
Namespace Prefix:	tmus_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 55
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-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

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
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-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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
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-URI http://asc.fasb.org/extlink&oid=120391452&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

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
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+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 944
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-Section S99
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+ Details

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

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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Namespace Prefix:
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- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=tmus_A2250SeniorNotesDue2026Member
Namespace Prefix:
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Balance Type:
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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Debt - Additional Information (Details) - USD ($)	Mar. 27, 2021	Mar. 31, 2021	Mar. 23, 2021	Jan. 14, 2021	Oct. 30, 2020	Apr. 06, 2020	Mar. 31, 2020
Debt Instrument [Line Items]
Effective interest rate		4.30%					5.20%
Average debt outstanding during period		$ 73,700,000,000					$ 25,000,000,000.0
Senior Notes
Debt Instrument [Line Items]
Principal Issuances			$ 3,800,000,000	$ 3,000,000,000.0		$ 19,000,000,000.0
Senior Secured Term Loan Commitment
Debt Instrument [Line Items]
Principal Issuances					$ 5,000,000,000.0
Total outstanding obligation				2,000,000,000.0
2.250% Senior Notes due 2026
Debt Instrument [Line Items]
Principal Issuances				$ 1,000,000,000.0
Interest rate, stated percentage				2.25%
2.625% Senior Notes due 2029
Debt Instrument [Line Items]
Principal Issuances				$ 1,000,000,000
Interest rate, stated percentage				2.625%
2.875% Senior Notes due 2031
Debt Instrument [Line Items]
Principal Issuances				$ 1,000,000,000.0
Interest rate, stated percentage				2.875%
2.625% Senior Notes Due 2026
Debt Instrument [Line Items]
Principal Issuances			$ 1,200,000,000
Interest rate, stated percentage			2.625%
3.375% Senior Notes due 2029
Debt Instrument [Line Items]
Principal Issuances			$ 1,250,000,000
Interest rate, stated percentage			3.375%
3.500% Senior Notes due 2031
Debt Instrument [Line Items]
Principal Issuances			$ 1,350,000,000
Interest rate, stated percentage			3.50%
6.500% Senior Notes due 2026
Debt Instrument [Line Items]
Interest rate, stated percentage	6.50%
Principal Amount	$ 2,000,000,000.0
Redemption Price (as a percent)	103.25%
Redemption premium	$ 65,000,000
Write-off of issuance costs	$ 36,000,000