Property, Plant and Equipment (Components of Property Plant and Equipment) (Details) (Successor [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Property, Plant and Equipment [Line Items]
Less accumulated depreciation	$ (5,358)	$ (2,449)
Property, plant and equipment, net	19,721	16,299
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	266	265
Network Equipment, Site Costs and Related Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	18,990	14,902
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	754	745
Non-network internal use software, office equipment, leased devices and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,979	866
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Construction in progress	$ 2,090	$ 1,970