Installment Receivables Installment Receivables - (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Sep. 30, 2014	Sep. 30, 2014 Successor [Member]	Mar. 31, 2014 Successor [Member]	Sep. 30, 2014 Successor [Member] Prime [Member]	Mar. 31, 2014 Successor [Member] Prime [Member]	Sep. 30, 2014 Successor [Member] Subprime [Member]	Mar. 31, 2014 Successor [Member] Subprime [Member]	Sep. 30, 2014 Successor [Member] Trade Accounts Receivable [Member]	Mar. 31, 2014 Successor [Member] Trade Accounts Receivable [Member]	Sep. 30, 2014 Successor [Member] Other Noncurrent Assets [Member]	Mar. 31, 2014 Successor [Member] Other Noncurrent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Installment Billing Maximum Payment Term	24 months
Installment receivables, gross		$ 1,494	$ 740	$ 1,065	$ 487	$ 429	$ 253
Deferred interest		(133)	(77)
Installment receivables, net of deferred interest		1,361	663
Allowance for credit losses		(141)	(47)
Installment receivables, net		$ 1,220	$ 616					$ 818	$ 299	$ 402	$ 317