Property, Plant and Equipment (Components of Property Plant and Equipment) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Mar. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	$ 20,297	$ 19,721
Successor [Member]
Property, Plant and Equipment [Line Items]
Less accumulated depreciation	(9,692)	(5,358)
Property, plant and equipment, net	20,297	19,721
Successor [Member] | Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	260	266
Successor [Member] | Network Equipment, Site Costs and Related Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	21,500	18,990
Successor [Member] | Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	798	754
Successor [Member] | Non-network internal use software, office equipment, leased devices and other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,182	2,979
Successor [Member] | Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Construction in progress	$ 1,249	$ 2,090