Long-Term Debt, Financing and Capital Lease Obligations (Narrative) (Details) site in Thousands		1 Months Ended				3 Months Ended		12 Months Ended
		Feb. 28, 2017	Oct. 31, 2016 USD ($)	May 31, 2016 USD ($)	Apr. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2017 USD ($) site years		Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Feb. 02, 2017 USD ($)	Nov. 30, 2015 USD ($)	Nov. 19, 2015 USD ($)	Dec. 31, 2014 USD ($) tranche	Jul. 10, 2013 USD ($)	Apr. 02, 2013 USD ($)
Schedule of Capitalization, Long-term Debt [Line Items]
Receivables Facility, Amount of Funds Available								$ 826,000,000
Receivables Facility, Repayment Under Facility								416,000,000
Receivables Facility, Amount Drawn on Facility								100,000,000
Long-term debt, gross												$ 6,000,000,000
Long-term debt issued by 100% owned subsidiary and is fully and unconditionally guaranteed by the parent								26,100,000,000
Secured debt								13,100,000,000
Interest costs capitalized								44,000,000		$ 51,000,000	$ 56,000,000
Cash interest payments							$ 2,300,000,000	$ 2,700,000,000		$ 2,400,000,000
Senior notes weighted average effective interest rate								6.40%		6.40%	6.10%
Redeemable notes								$ 30,200,000,000
Principal amount of notes with the right to require the Company to repurchase on change of control								24,100,000,000
Fixed amount of cash for a fixed principal amount of notes surrendered that becomes exchangeable at the holder's option																$ 706.21
Fixed principal amount of notes surrendered for a fixed amount of cash that becomes exchangeable at the holder's option																$ 1,000
Maximum funding limit													$ 4,300,000,000
Receivables Facility, Amount Outstanding								2,000,000,000
Repayments of Accounts Receivable Securitization								$ 654,000,000
Number of cell sites leased back | site								3
Term in years for cell sites leased back renewal options | years								20
Ratio of total indebtedness to adjusted EBITDA								2.5
Sale Leaseback Transaction, Net Book Value						$ 1,300,000,000								$ 1,300,000,000
Payments for (Proceeds from) Businesses and Interest in Affiliates				$ 181,000,000
Proceeds from sale-leaseback transaction						$ 1,100,000,000		$ 0		$ 1,136,000,000	$ 0
FCC Licenses [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Indefinite-lived Intangible Assets Acquired								85,000,000
Exchangeable Notes [Member] | Clearwire Communications LLC [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross								$ 629,000,000	[1]	629,000,000
Debt instrument, interest rate, stated percentage								8.25%								8.25%
Secured Notes [Member] | Spectrum Financing [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Additional Borrowings Available			$ 3,500,000,000
Debt Instrument, Maximum Borrowing Capacity			$ 7,000,000,000
Secured Notes [Member] | Clearwire Communications LLC [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross	[1]							$ 0		300,000,000
Principal amount of notes with the right to require the Company to repurchase on change of control								$ 300,000,000
Debt instrument, interest rate, stated percentage	[1]							14.75%
Secured Notes [Member] | Sprint Spectrum Co LLC, Sprint Spectrum Co II LLC, Sprint Spectrum Co III LLC [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross								$ 3,500,000,000		0
Debt instrument, interest rate, stated percentage			3.36%					3.36%
Debt instrument, face amount			$ 3,500,000,000
Debt Instrument, Term			5 years
Secured Debt, Current								$ 438,000,000
Debt Issuance Costs, Gross			$ 95,000,000
Secured term loan [Member] | Sprint Nextel Corporation Guaranteed Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross												4,000,000,000
Line of credit facility, amount outstanding								$ 4,000,000,000		0
Debt Instrument, Term		7 years
Senior Notes [Member] | Sprint Communications, Inc. 6% Senior Note [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt instrument, interest rate, stated percentage								6.00%
Repayments of Debt								$ 2,000,000,000
Senior Notes [Member] | Sprint Corporation [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross								10,500,000,000		10,500,000,000
Senior Notes [Member] | Sprint Nextel Corporation Guaranteed Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross								$ 6,280,000,000		9,280,000,000
Senior Notes [Member] | Sprint Communications, Inc. 9.125% Senior Note [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt instrument, interest rate, stated percentage								9.125%
Repayments of Debt								$ 1,000,000,000
Line of Credit [Member] | Export Development Canada Credit Facilities [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Repayments of Debt								250,000,000
Line of credit facility, amount outstanding								300,000,000		550,000,000
Line of Credit [Member] | Secured Equipment Credit Facility [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt instrument, annual principal payment								254,000,000
Line of Credit [Member] | Finnvera Secured Equipment Credit Facility [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity															$ 800,000,000
Line of credit facility, amount outstanding								140,000,000
Debt instrument, annual principal payment								56,000,000
Line of Credit [Member] | K-sure Secured Equipment Credit Facility [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity															$ 750,000,000
Line of credit facility, amount outstanding								259,000,000
Debt instrument, annual principal payment								65,000,000
Number of tranches | tranche															3
Line of Credit [Member] | Delcredere / Ducroire (D/D) Secured Equipment Credit Facility [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity															$ 250,000,000
Line of credit facility, amount outstanding								32,000,000
Guaranteed Notes [Member] | Sprint Nextel Corporation Guaranteed Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross								4,000,000,000		4,000,000,000
Revolving Credit Facility [Member] | Unsecured Revolving Credit Facility expires in 2018 [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity																	$ 3,300,000,000
Line of Credit Facility, Remaining Borrowing Capacity								1,800,000,000
Line of credit facility, amount outstanding								$ 0		0
Revolving Credit Facility [Member] | Secured Revolving Bank Credit Facility expires in Feb 2021[Member] [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity												2,000,000,000
Ratio of total indebtedness to adjusted EBITDA								6.0
Ratio Of Total Indebtedness To Adjusted EBITDA, Minimum								3.5
Letter of Credit [Member] | Unsecured Revolving Credit Facility expires in 2018 [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Letters of credit outstanding, amount								$ 215,000,000
Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross								315,000,000
Capital Lease Obligations [Member] | Shentel [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross								225,000,000
Parent [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term debt, gross								10,500,000,000
Proceeds from sale-leaseback transaction										$ 0
Spectrum Assets [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Concentration Risk, Percentage			14.00%
MLS 2nd Tranche [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Sale Leaseback Transaction, Net Book Value				$ 1,300,000,000				385,000,000
Proceeds from sale-leaseback transaction					$ 1,100,000,000
Tower financing [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Sale Leaseback Transaction, Net Book Value								191,000,000
Network Sale-Leaseback [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt and Capital Lease Obligations, Repayments of Principal in Next Twelve Months								1,900,000,000
Repayments of Debt								300,000,000
Proceeds from sale-leaseback transaction					2,200,000,000
Sale Leaseback Transaction, Net Book Value					$ 3,000,000,000			2,400,000,000
Other, Net [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Payments for (Proceeds from) Businesses and Interest in Affiliates								$ 96,000,000
Interest Rate Swap [Member] | Secured term loan [Member] | Sprint Nextel Corporation Guaranteed Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Derivative, Term of Contract								5 years
Derivative, Notional Amount												$ 2,000,000,000.0
Derivative Liability, Fair Value, Gross Liability								$ 2,000,000
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] | Secured Revolving Bank Credit Facility expires in Feb 2021[Member] [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate								2.50%

[1] (1)Notes of Clearwire Communications LLC are also direct obligations of Clearwire Finance, Inc. and are guaranteed by certain Clearwire subsidiaries.