Finance Receivables, Net (Impaired Finance Receivables) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	$ 63	$ 73
Impaired Finance Receivables Individually Evaluated with No Related Allowance	145	168
Impaired Finance Receivables Aggregated And Evaluated For Impairment	323	416
Impaired Finance Receivables	531	657
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	63	73
Unpaid Principal Balance Individually Evaluated with No Related Allowance	145	168
Unpaid Principal Balance Aggregated And Evaluated For Impairment	319	411
Unpaid Principal Balance	527	652
Individually Evaluated Allowance	31	33
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	72	121
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	156	124
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	369	463
Average Impaired Finance Receivables	597	708
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	3	2
Interest Income Recognized Individually Evaluated with No Related Allowance	5	6
Interest Income Recognized Aggregated And Evaluated For Impairment	27	37
Interest Income Recognized	35	45
Wholesale [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	13	16
Impaired Finance Receivables Individually Evaluated with No Related Allowance	51	66
Impaired Finance Receivables	64	82
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	13	16
Unpaid Principal Balance Individually Evaluated with No Related Allowance	51	66
Unpaid Principal Balance	64	82
Individually Evaluated Allowance	1	3
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	16	22
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	59	63
Average Impaired Finance Receivables	75	85
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	0
Interest Income Recognized Individually Evaluated with No Related Allowance	1	2
Interest Income Recognized	1	2
Real estate [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	27	33
Impaired Finance Receivables Individually Evaluated with No Related Allowance	90	97
Impaired Finance Receivables	117	130
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	27	33
Unpaid Principal Balance Individually Evaluated with No Related Allowance	90	97
Unpaid Principal Balance	117	130
Individually Evaluated Allowance	8	7
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	32	75
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	93	59
Average Impaired Finance Receivables	125	134
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	1	1
Interest Income Recognized Individually Evaluated with No Related Allowance	4	4
Interest Income Recognized	5	5
Working capital [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	23	24
Impaired Finance Receivables Individually Evaluated with No Related Allowance	4	5
Impaired Finance Receivables	27	29
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	23	24
Unpaid Principal Balance Individually Evaluated with No Related Allowance	4	5
Unpaid Principal Balance	27	29
Individually Evaluated Allowance	22	23
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	24	24
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	4	2
Average Impaired Finance Receivables	28	26
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	2	1
Interest Income Recognized Individually Evaluated with No Related Allowance	0	0
Interest Income Recognized	2	1
Retail Loan [Member]
Impaired Finance Receivables
Impaired Finance Receivables Aggregated And Evaluated For Impairment	322	415
Impaired Finance Receivables	322	415
Unpaid Principal Balance
Unpaid Principal Balance Aggregated And Evaluated For Impairment	318	410
Unpaid Principal Balance	318	410
Average Impaired Finance Receivables
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	368	462
Average Impaired Finance Receivables	368	462
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	27	37
Interest Income Recognized	27	37
Commercial [Member]
Impaired Finance Receivables
Impaired Finance Receivables Aggregated And Evaluated For Impairment	1	1
Impaired Finance Receivables	1	1
Unpaid Principal Balance
Unpaid Principal Balance Aggregated And Evaluated For Impairment	1	1
Unpaid Principal Balance	1	1
Average Impaired Finance Receivables
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	1	1
Average Impaired Finance Receivables	1	1
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	0	0
Interest Income Recognized	$ 0	$ 0