Installment Receivables Installment Receivables On Gross Basis by Credit Category (Details) (Successor [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	$ 1,199	$ 740
Prime [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	771	487
Subprime [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	428	253
Billed Revenues [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	1,120	708
Billed Revenues [Member] | Prime [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	730	466
Billed Revenues [Member] | Subprime [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	390	242
Billed receivables, current [Member] | Billed Revenues [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	51	25
Billed receivables, current [Member] | Billed Revenues [Member] | Prime [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	30	16
Billed receivables, current [Member] | Billed Revenues [Member] | Subprime [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	21	9
Billed receivables, past due [Member] [Member] | Billed Revenues [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	28	7
Billed receivables, past due [Member] [Member] | Billed Revenues [Member] | Prime [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	11	5
Billed receivables, past due [Member] [Member] | Billed Revenues [Member] | Subprime [Member]
Financing Receivable, Recorded Investment [Line Items]
Installment receivables, gross	$ 17	$ 2