Long-Term Debt, Financing and Capital Lease Obligations (Narrative) (Details)	1 Months Ended					3 Months Ended				9 Months Ended		12 Months Ended
	Jun. 30, 2018	Feb. 28, 2017	Oct. 31, 2016 USD ($)	May 31, 2016 USD ($)	Apr. 30, 2016 USD ($)	Dec. 31, 2017 USD ($) site years	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) site years	Dec. 31, 2016 USD ($)	Mar. 31, 2017 USD ($) site	Feb. 02, 2017 USD ($)	Nov. 30, 2015 USD ($)	Dec. 31, 2014 USD ($) tranche
Schedule of Capitalization, Long-term Debt [Line Items]
Maximum Funding Limit														$ 4,300,000,000
Receivables Facility, maximum amount available based on receivables sold to investors, percent						50.00%				50.00%
Receivables Facility, Amount Outstanding						$ 3,000,000,000				$ 3,000,000,000
Receivables Facility, Amount of Funds Available						781,000,000				781,000,000
Receivables Facility, Amount Drawn on Facility										2,700,000,000
Sale Leaseback Transaction, Cumulative Lease Payments										1,700,000,000
Long-term debt issued by 100% owned subsidiary and is fully and unconditionally guaranteed by the parent						22,000,000,000				22,000,000,000
Interest Costs Capitalized										42,000,000	$ 32,000,000
Cash interest payments										1,900,000,000	1,900,000,000
Redeemable notes						27,600,000,000				27,600,000,000
Principal amount of notes with the right to require the Company to repurchase on change of control						$ 21,400,000,000				21,400,000,000
Call premiums paid on debt redemptions										129,000,000	0
Gain (Loss) on Extinguishment of Debt										$ (65,000,000)	0
Long-term Debt, Gross													$ 6,000,000,000
Long-term Debt, Percentage Bearing Variable Interest, Amount													250
Number of cell sites leased back | site						2,000				2,000		3,000
Term in years for cell sites leased back renewal options | years						20				20
Payments for (Proceeds from) Businesses and Interest in Affiliates				$ 181,000,000
Ratio Of Total Indebtedness To Adjusted EBITDA						2.5				2.5
cash paid to purchasers under receivables facility											185,000,000
Financing Receivable, Net						$ 1,383,000,000				$ 1,383,000,000		$ 1,764,000,000
Installment Lease Receivables, Net Book Value						5,600,000,000				5,600,000,000
Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross						334,000,000				334,000,000		3,016,000,000
Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit							$ 3,200,000,000
Network Sale-Leaseback [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Sale Leaseback Transaction, Net Book Value					$ 3,000,000,000	1,800,000,000				1,800,000,000
Sale Leaseback Transaction, Net Proceeds, Financing Activities					2,200,000,000
Long-term Debt and Capital Lease Obligations, Repayments of Principal in Next Twelve Months						454,000,000				454,000,000
Repayments of Debt										1,400,000,000
Handset Sale-Leaseback Tranche 2 [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Sale Leaseback Transaction, Net Book Value				$ 1,300,000,000
Sale Leaseback Transaction, Net Proceeds, Investing Activities					1,100,000,000
Receivables from sale-leaseback					$ 186,000,000
Repayments of Debt										385,000,000
Handset Sale-Leaseback Tranche 1 [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Sale Leaseback Transaction, Monthly Rental Payments									$ 117,000,000		494,000,000
Tower financing [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Sale Leaseback Transaction, Net Book Value						$ 160,000,000				$ 160,000,000
Minimum [Member] | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						2.35%				2.35%
Maximum [Member] | Capital Lease Obligations [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						12.00%				12.00%
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						$ 145,000,000				$ 145,000,000
Delcredere / Ducroire (D/D) Secured Equipment Credit Facility [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of Credit Facility, Increase (Decrease), Net										150,000,000
Delcredere / Ducroire (D/D) Secured Equipment Credit Facility [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit							150,000,000								$ 250,000,000
Repayments of Lines of Credit										23,000,000
Line of Credit Facility, Amount Outstanding						159,000,000				159,000,000
K-sure Secured Equipment Credit Facility [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit															$ 750,000,000
Repayments of Lines of Credit										65,000,000
Number of tranches | tranche															3
Line of Credit Facility, Amount Outstanding						194,000,000				194,000,000
Finnvera Secured Equipment Credit Facility [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of Credit Facility, Increase (Decrease), Net										160,000,000
Finnvera Secured Equipment Credit Facility [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit															$ 800,000,000
Repayments of Lines of Credit										98,000,000
Line of Credit Facility, Amount Outstanding						202,000,000				202,000,000
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						300,000,000				300,000,000
Secured Revolving Bank Credit Facility expires in Feb 2021[Member] [Member] | Revolving Credit Facility [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Aggregate principal amount line of credit													$ 2,000,000,000
Line of Credit Facility, Remaining Borrowing Capacity						1,800,000,000				1,800,000,000
Line of Credit Facility, Amount Outstanding						0				0		0
Ratio Of Total Indebtedness To Adjusted EBITDA													6.0
Ratio Of Total Indebtedness To Adjusted EBITDA, Minimum													3.5
Secured Revolving Bank Credit Facility expires in Feb 2021[Member] [Member] | Letter of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Letters of Credit Outstanding, Amount						$ 151,000,000				$ 151,000,000
Sprint Nextel Corporation [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						9.25%				9.25%
Long-term Debt, Gross						$ 200,000,000				$ 200,000,000		200,000,000
Sprint Nextel Corporation [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross													$ 4,000,000,000
Line of Credit Facility, Amount Outstanding						3,970,000,000				3,970,000,000		4,000,000,000
Debt Instrument, Term		7 years
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		6,080,000,000
Sprint Nextel Corporation [Member] | Guaranteed notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross						$ 2,800,000,000				$ 2,800,000,000		4,000,000,000
Sprint Nextel Corporation [Member] | Minimum [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						6.00%				6.00%
Sprint Nextel Corporation [Member] | Minimum [Member] | Guaranteed notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						7.00%				7.00%
Sprint Nextel Corporation [Member] | Maximum [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						11.50%				11.50%
Sprint Nextel Corporation [Member] | Maximum [Member] | Guaranteed notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						9.00%				9.00%
PRWireless HoldCo, LLC Secured Term Loan [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity						$ 20,000,000				$ 20,000,000
Line of Credit Facility, Amount Outstanding						183,000,000	$ 178,000,000			$ 183,000,000		0
Proceeds from Lines of Credit						$ 5,000,000
Spectrum Financing [Member] | Secured Debt [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Maximum Borrowing Capacity			$ 7,000,000,000
Debt Instrument, Additional Borrowings Available			$ 3,500,000,000
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]
Debt Instrument, Interest Rate, Stated Percentage			3.36%			3.36%				3.36%
Repayments of Debt										$ 219,000,000
Long-term Debt, Gross						$ 3,281,000,000				3,281,000,000		3,500,000,000
Debt instrument face amount			$ 3,500,000,000
Debt Instrument, Term			5 years
Secured Debt, Current						875,000,000				875,000,000
Notes due 2017 and Guaranteed Notes Due 2018 [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Call premiums paid on debt redemptions								$ 129,000,000
Debt Instrument, Unamortized Premium								64,000,000
Gain (Loss) on Extinguishment of Debt								$ 65,000,000
Guaranteed Notes Due 2018 [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage								9.00%
Repayments of Debt								$ 1,200,000,000
Notes due 2017 [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage							8.375%	8.375%
Extinguishment of Debt, Amount							$ 912,000,000
Repayments of Debt								$ 388,000,000
Sprint Corporation [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Long-term Debt, Gross						$ 10,500,000,000				$ 10,500,000,000		10,500,000,000
Sprint Corporation [Member] | Minimum [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						7.13%				7.13%
Sprint Corporation [Member] | Maximum [Member] | Senior Notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						7.88%				7.88%
Clearwire Communications LLC [Member] | Exchangeable notes [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Redemption price (as a percent)										100.00%
Debt Instrument, Interest Rate, Stated Percentage						8.25%				8.25%
Long-term Debt, Gross						$ 0				$ 0		629,000,000
Wireless Service [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation						26.00%
Installment Receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation						28.00%
Future lease receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation						46.00%
Financing Receivable
Schedule of Capitalization, Long-term Debt [Line Items]
Cash received for sale of receivables under receivables facility											625,000,000
Cash Flows Between Transferor and Transferee, Proceeds from Collections Reinvested in Revolving Period Transfers											$ 660,000,000
Accounts and notes receivable, net
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net						$ 1,168,000,000				1,168,000,000		1,195,000,000
Accounts and notes receivable, net | Wireless Services and Installment Receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net						3,000,000,000				3,000,000,000
Other assets
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net						215,000,000				215,000,000		$ 569,000,000
Other assets | Special purpose entity [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Financing Receivable, Net						208,000,000				208,000,000
Interest Rate Swap [Member] | Sprint Nextel Corporation [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Derivative, Notional Amount													$ 2,000,000,000
Derivative Liability, Fair Value, Gross Liability						$ 10,000,000				$ 10,000,000
Derivative, Term of Contract												5 years
Scenario, Forecast [Member] | Wireless Service [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation	26.00%
Scenario, Forecast [Member] | Installment Receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation	18.00%
Scenario, Forecast [Member] | Future lease receivables [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Purchase Commitment Allocation	56.00%
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate							1.25%
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate							4.25%
London Interbank Offered Rate (LIBOR) [Member] | PRWireless HoldCo, LLC Secured Term Loan [Member] | Secured term loan [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate										5.25%
Base Rate [Member] | Minimum [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate							0.25%
Base Rate [Member] | Maximum [Member] | Line of Credit [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Debt Instrument, Basis Spread on Variable Rate							3.25%