Long-Term Debt, Financing and Capital Lease Obligations (Narrative) (Details)		1 Months Ended			9 Months Ended
	Nov. 01, 2019 USD ($)	Feb. 28, 2017	Oct. 31, 2016 USD ($)	May 31, 2016 USD ($)	Dec. 31, 2019 USD ($) site years	Dec. 31, 2018 USD ($)	Sep. 16, 2019 USD ($)	May 01, 2019 USD ($)	Apr. 01, 2019 USD ($)	Mar. 31, 2019 USD ($) site	Feb. 26, 2019 USD ($)	Nov. 26, 2018 USD ($)	Feb. 20, 2018	Feb. 02, 2017 USD ($)
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross												$ 8,000,000,000.0		$ 6,000,000,000.0
Long-term debt issued by 100% owned subsidiary and is fully and unconditionally guaranteed by the parent					$ 20,100,000,000
Interest Costs Capitalized					52,000,000	$ 54,000,000
Cash interest payments					1,700,000,000	$ 1,900,000,000
Redeemable notes					27,700,000,000
Principal amount of notes with the right to require the Company to repurchase on change of control					23,200,000,000
Current portion of long-term debt, financing and capital lease obligations					3,880,000,000				$ 4,514,000,000	$ 4,557,000,000
Operating Leases, Future Minimum Payments Due										$ 11,767,000,000
Maximum Funding Limit					$ 4,500,000,000
Receivables Facility, maximum amount available based on receivables sold to investors, percent					51.00%
Receivables Facility, Amount Outstanding					$ 3,300,000,000
Receivables Facility, Amount of Funds Available					95,000,000
Maximum Funding Limit, increase					200,000,000
Receivables Facility, Amount Drawn on Facility					4,600,000,000
Sale Leaseback Transaction, Cumulative Lease Payments					$ 3,800,000,000
Long-term Debt, Percentage Bearing Variable Interest, Amount												300		250
Number of cell sites leased back | site					1,750					3,000
Term in years for cell sites leased back renewal options | years					20
Payments for (Proceeds from) Businesses and Interest in Affiliates				$ 181,000,000
Ratio of total indebtedness to adjusted EBITDA					2.5
Financing Receivable, Net					$ 1,250,000,000					$ 926,000,000
Installment Lease Receivables, Net Book Value					6,700,000,000
Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross										538,000,000
Finance lease obligations [Domain]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					22,000,000
Other Debt Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 206,000,000
Tower financing
Schedule of Capitalization, Long-term Debt [Line Items]
Sale Leaseback Transaction, Net Book Value										109,000,000
Maximum | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					12.00%
Minimum | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					2.62%
Spectrum Assets [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Concentration Risk, Percentage			14.00%
Shentel [Member] | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 121,000,000
Shentel [Member] | Maximum | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt instrument term				6 years
Shentel [Member] | Minimum | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt instrument term				5 years
Delcredere / Ducroire (D/D) Secured Equipment Credit Facility [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Repayments of Lines of Credit					39,000,000
Line of Credit Facility, Amount Outstanding					80,000,000
K-sure Secured Equipment Credit Facility [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Repayments of Lines of Credit					159,000,000
Line of Credit Facility, Amount Outstanding					387,000,000
Line of credit facility, year-to-date amount drawn					96,000,000
Finnvera Secured Equipment Credit Facility [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Repayments of Lines of Credit					54,000,000
Line of Credit Facility, Amount Outstanding					38,000,000
Export Development Canada Agreement [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of Credit Facility, Amount Outstanding										300,000,000
Export Development Canada Agreement [Member] | Tranche three and four [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of Credit Facility, Amount Outstanding					0		$ 300,000,000
Secured Revolving Bank Credit Facility expires in Feb 2021 | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Repayments of Lines of Credit					30,000,000
Line of Credit Facility, Amount Outstanding					3,900,000,000
Secured Revolving Bank Credit Facility expires in Feb 2021 | Revolving Credit Facility
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit														$ 2,000,000,000.0
Remaining borrowing capacity					1,900,000,000
Line of Credit Facility, Amount Outstanding					$ 0					0
Ratio of total indebtedness to adjusted EBITDA					3.75
Ratio Of Total Indebtedness To Adjusted EBITDA, Minimum														3.5
Secured Revolving Bank Credit Facility expires in Feb 2021 | Letter of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Letters of Credit Outstanding, Amount					$ 116,000,000
Sprint Nextel Corporation [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross												2,000,000,000.0		$ 4,000,000,000.0
Incremental Term Loan borrowing											$ 900,000,000	$ 1,100,000,000
Debt instrument term		7 years
Line of Credit Facility, Amount Outstanding					5,870,000,000					5,915,000,000
Sprint Nextel Corporation [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					4,780,000,000					4,780,000,000
Sprint Nextel Corporation [Member] | Guaranteed notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 1,000,000,000					1,000,000,000
Sprint Nextel Corporation [Member] | Maximum | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					11.50%
Sprint Nextel Corporation [Member] | Minimum | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					6.00%
Sprint Nextel Corporation [Member] | Minimum | Guaranteed notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					7.00%
PRWireless HoldCo, LLC Secured Term Loan [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Repayments of Lines of Credit	$ 199,000,000
Line of Credit Facility, Amount Outstanding					$ 0					198,000,000
Spectrum Financing [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Maximum Borrowing Capacity			$ 7,000,000,000.0
Debt Instrument, Additional Borrowings Available										3,900,000,000
Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					5,469,000,000					6,125,000,000
Debt Instrument, Interest Rate, Stated Percentage			3.36%
Debt instrument face amount			$ 3,500,000,000
Debt instrument term			5 years
Repayments of Debt					656,000,000
Secured Debt, Current					$ 875,000,000
Operating Leases, Future Minimum Payments Due			$ 3,500,000,000
Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member] | Maximum | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					5.15%
Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member] | Minimum | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					3.36%
Sprint Financing maturing 2021 [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 1,500,000,000
Sprint Corporation [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 12,000,000,000					12,000,000,000
Debt Instrument, Interest Rate, Stated Percentage													7.625%
Sprint Corporation [Member] | Maximum | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					7.88%
Sprint Corporation [Member] | Minimum | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					7.13%
Sprint Capital Corporation [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross					$ 4,475,000,000			$ 1,700,000,000		$ 6,204,000,000
Debt Instrument, Interest Rate, Stated Percentage								6.90%
Sprint Capital Corporation [Member] | Maximum | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					8.75%
Sprint Capital Corporation [Member] | Minimum | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					6.88%
Spectrum Financing maturing 2025 [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage										4.738%
Debt Instrument, Additional Borrowings Available										$ 2,100,000,000
Spectrum Financing maturing 2028 [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage										5.152%
Debt Instrument, Additional Borrowings Available										$ 1,800,000,000
Wireless Service [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation					22.00%
Installment Receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation					78.00%
Accounts and notes receivable, net
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net					$ 951,000,000					679,000,000
Accounts and notes receivable, net | Wireless Services and Installment Receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net					2,700,000,000
Other assets
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net					299,000,000					247,000,000
Other assets | Special purpose entity [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net					280,000,000
Interest Rate Swap [Member] | Sprint Nextel Corporation [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Derivative Liability, Fair Value, Gross Liability					$ 17,000,000					$ 13,000,000
Derivative Liability														$ 2,000,000,000.0
Derivative, Term of Contract					5 years