Income Taxes (Income Tax (Expense) Benefit Allocated to Other Items) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended	12 Months Ended
		Mar. 31, 2014	Mar. 31, 2013	Jul. 10, 2013	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2013
Successor [Member]
Income Tax Contingency [Line Items]
Unrecognized net periodic pension and other postretirement benefit cost	[1]	$ 0			$ 0	$ 0	$ (58)
Unrealized holding gains/losses on securities	[1]	$ (1)			$ 0	$ 0	$ (3)
Predecessor [Member]
Income Tax Contingency [Line Items]
Unrecognized net periodic pension and other postretirement benefit cost	[1]		$ (10)	$ (18)
Unrealized holding gains/losses on securities	[1]		$ (1)	$ 0

[1] (1)These amounts have been recognized in accumulated other comprehensive loss.