Severance and Exit Costs (Details) - Successor [Member] - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Mar. 31, 2016		Mar. 31, 2015
Restructuring Cost and Reserve [Line Items]
Severance costs			$ 216	[1]	$ 253	[2]
Wireless [Member]
Restructuring Cost and Reserve [Line Items]
Severance costs			191		218
Wireline [Member]
Restructuring Cost and Reserve [Line Items]
Severance costs			$ 25		$ 35
Other Operating Income (Expense) [Member] | Wireless [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, accrual adjustment	$ 20	$ 41

[1] (2)For the Successor year ended March 31, 2016, we recognized costs of $216 million ($191 million Wireless, $25 million Wireline).

[2] (5)For the Successor year ended March 31, 2015, we recognized costs of $253 million ($218 million Wireless, $35 million Wireline).