Significant Transactions Significant Transactions (Details) (USD $)		6 Months Ended	12 Months Ended		6 Months Ended		12 Months Ended			6 Months Ended		3 Months Ended	12 Months Ended		5 Months Ended
	Sep. 30, 2014	Jul. 09, 2013 Clearwire Acquisition [Member]	Jun. 30, 2014 Clearwire Acquisition [Member]	Jul. 08, 2013 Clearwire Acquisition [Member]	Jul. 09, 2013 Clearwire Acquisition [Member] Clearwire [Member]	Jul. 10, 2013 SoftBank Merger [Member]	Jun. 30, 2014 SoftBank Merger [Member]	Sep. 30, 2014 SoftBank Merger [Member]	Oct. 22, 2012 SoftBank Merger [Member]	Sep. 30, 2014 Successor [Member]	Sep. 30, 2013 Successor [Member]	Jul. 10, 2013 Predecessor [Member]	Jun. 30, 2014 deferred tax liability [Member] Clearwire Acquisition [Member]	Jun. 30, 2014 deferred tax liability [Member] SoftBank Merger [Member]	Sep. 30, 2014 Accounts Receivable [Member]	May 16, 2014 Accounts Receivable [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired					$ 3,500,000,000	$ 14,100,000,000				$ 0	$ 14,112,000,000	$ 4,039,000,000
Cash Acquired from Acquisition		198,000,000				2,500,000,000
Cash consideration accrued for dissenting shares relating to stockholders who exercised their right to appraisal		125,000,000
Business combination, cost of acquired entity, partial cash paid		3,700,000,000				16,600,000,000
Stock Issued During Period, Value, Acquisitions						5,300,000,000
Equity Method Investments, Fair Value Disclosure				3,300,000,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities													270,000,000	300,000,000
Conversion of Sprint vested stock-based awards upon acquisition		59,000,000				193,000,000
Goodwill, Purchase Accounting Adjustments			269,000,000				476,000,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners						22.00%		20.00%
Convertible Debt									3,100,000,000
Debt Instrument, Interest Rate, Stated Percentage									1.00%
Stock Issued During Period, Shares, Conversion of Convertible Securities						590,476,190
Debt Instrument, Convertible, Conversion Price						$ 5.25
Business Acquisition, Percentage of Voting Interests Acquired								80.00%
Capital Contribution By SoftBank						5,000,000,000
Business combination, cost of acquired entity, additional partial cash paid						1,900,000,000
Accounts Receivable Facility, Expiration Period															2 years
Maximum Funding Limit																1,300,000,000
Receivables Facility, Amount of Funds Available	$ 1,100,000,000