Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
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

+ 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

Amount, after accumulated amortization, of debt discount (premium).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28567-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

+ Details

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

- Definition

Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

+ References

+ Details

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

- Definition

Amount of long-term debt and capital leases due within one year or the normal operating cycle, if longer.

+ References

+ Details

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

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

+ Details

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

- Definition

+ References

+ Details

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

Long-Term Debt, Financing and Capital Lease Obligations (Schedule of Long-term Debt Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Mar. 31, 2018	Feb. 20, 2018	Feb. 02, 2017	Oct. 31, 2016
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 6,000
Debt Instrument, Unamortized Premium (Discount), Net	$ (338)	$ (111)
Current and Long-term Debt, Financing and Capital Lease Obligations	40,675	40,892
Current portion of long-term debt, financing and capital lease obligations	5,346	3,429
Long-term debt, financing and capital lease obligations	35,329	37,463
Senior Notes [Member] \| Sprint Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			7.625%
Long-term Debt, Gross	12,000	12,000
Senior Notes [Member] \| Sprint Nextel Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					9.25%
Long-term Debt, Gross	4,980	4,980
Current portion of long-term debt, financing and capital lease obligations	200
Senior Notes [Member] \| Sprint Capital Corporation [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	6,204	6,204
Guaranteed notes [Member] \| Sprint Nextel Corporation [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	2,753	2,753
Secured Debt [Member] \| Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					3.36%
Long-term Debt, Gross	6,563	7,000
Financing Obligation [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 3,024	2,411
Revolving Credit Facility [Member] \| Secured Revolving Bank Credit Facility expires in Feb 2021[Member] [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	4.50%
Line of Credit Facility, Amount Outstanding	$ 0	0
Secured term loan [Member] \| Sprint Nextel Corporation [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	4.75%
Long-term Debt, Gross				$ 4,000
Line of Credit Facility, Amount Outstanding	$ 3,940	3,960
Secured term loan [Member] \| PRWireless HoldCo, LLC Secured Term Loan [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	7.64%
Line of Credit Facility, Amount Outstanding	$ 181	182
Line of Credit [Member] \| Export Development Canada Agreement [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding		300
Line of Credit [Member] \| Secured Equipment Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	461	527
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	308	$ 686
Financing Obligations, Capital Lease Obligations and Other [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 607
Minimum [Member] \| Senior Notes [Member] \| Sprint Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.13%
Minimum [Member] \| Senior Notes [Member] \| Sprint Nextel Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Minimum [Member] \| Senior Notes [Member] \| Sprint Capital Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.88%
Minimum [Member] \| Guaranteed notes [Member] \| Sprint Nextel Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.00%
Minimum [Member] \| Secured Debt [Member] \| Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.36%
Minimum [Member] \| Financing Obligation [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.32%
Minimum [Member] \| Line of Credit [Member] \| Secured Equipment Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	3.75%
Minimum [Member] \| Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.35%
Maximum [Member] \| Senior Notes [Member] \| Sprint Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.88%
Maximum [Member] \| Senior Notes [Member] \| Sprint Nextel Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	11.50%
Maximum [Member] \| Senior Notes [Member] \| Sprint Capital Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.75%
Maximum [Member] \| Guaranteed notes [Member] \| Sprint Nextel Corporation [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	9.00%
Maximum [Member] \| Secured Debt [Member] \| Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.15%
Maximum [Member] \| Financing Obligation [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.52%
Maximum [Member] \| Line of Credit [Member] \| Export Development Canada Agreement [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	4.74%
Maximum [Member] \| Line of Credit [Member] \| Secured Equipment Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate	4.43%
Maximum [Member] \| Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	12.00%