Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		3 Months Ended		6 Months Ended		0 Months Ended	3 Months Ended
	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2014 Successor [Member]	Sep. 30, 2013 Successor [Member]	Sep. 30, 2014 Successor [Member]	Sep. 30, 2013 Successor [Member]	Jul. 10, 2013 Predecessor [Member]	Jul. 10, 2013 Predecessor [Member]	Jul. 10, 2013 Clearwire [Member] Predecessor [Member]
Income Tax Contingency [Line Items]
Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance					$ 297	$ 327		$ 1,145
Decrease in valuation allowance attributable to disposition of intangible assets					73
Income tax benefit (expense)			(71)	(90)	(56)	(29)	(1,508)	(1,563)
Gain on previously-held equity interests			0	0	0	0	2,926	2,926	2,900
FCC License Amortization Period for Tax Purposes In Years	15 years
Unrecognized tax benefit	159	160
Income Taxes Paid, Net					$ 40