Income Taxes (Unrecognized Tax Benefit Rollforward) (Details) (Successor [Member], USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2015
Successor [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 166	$ 160
Additions based on current year tax positions	0	5
Additions based on prior year tax positions	1	3
Reductions for prior year tax positions	(1)	(3)
Reductions for settlements	0	(1)
Reductions for lapse of statute of limitations	(6)	(1)
Balance at end of period	$ 160	$ 163