Severance and Exit Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			$ 32
Wireless [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 6		15
Other Operating Income (Expense) [Member] | Wireless [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment		$ 41
Access [Member] | Wireless [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			20
Successor [Member] | Other Operating Income (Expense) [Member] | Wireless [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment				$ 20
Successor [Member] | Access [Member] | Severance and exit costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	11		18
Successor [Member] | Access [Member] | Severance and exit costs [Member] | Wireless [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	6		8
Successor [Member] | Access [Member] | Severance and exit costs [Member] | Wireline [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 5		10
Successor [Member] | Access [Member] | Cost of Sales [Member] | Wireline [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			$ 2