Finance Receivables, Net (Impaired Finance Receivables) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2013
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	$ 67		$ 67		$ 73
Impaired Finance Receivables Individually Evaluated with No Related Allowance	165		165		168
Impaired Finance Receivables Aggregated And Evaluated For Impairment	346		346		416
Impaired Finance Receivables	578		578		657
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	67		67		73
Unpaid Principal Balance Individually Evaluated with No Related Allowance	165		165		168
Unpaid Principal Balance Aggregated And Evaluated For Impairment	342		342		411
Unpaid Principal Balance	574		574		652
Individually Evaluated Allowance	30		30		33
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	69	95	74	133
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	157	163	159	114
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	356	459	380	474
Average Impaired Finance Receivables	582	717	613	721
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	0	2	2
Interest Income Recognized Individually Evaluated with No Related Allowance	2	0	4	3
Interest Income Recognized Aggregated And Evaluated For Impairment	7	10	22	29
Interest Income Recognized	9	10	28	34
Wholesale [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	17		17		16
Impaired Finance Receivables Individually Evaluated with No Related Allowance	70		70		66
Impaired Finance Receivables	87		87		82
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	17		17		16
Unpaid Principal Balance Individually Evaluated with No Related Allowance	70		70		66
Unpaid Principal Balance	87		87		82
Individually Evaluated Allowance	1		1		3
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	15	32	17	24
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	61	63	61	63
Average Impaired Finance Receivables	76	95	78	87
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	0	0	0
Interest Income Recognized Individually Evaluated with No Related Allowance	1	0	1	1
Interest Income Recognized	1	0	1	1
Real estate [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	27		27		33
Impaired Finance Receivables Individually Evaluated with No Related Allowance	91		91		97
Impaired Finance Receivables	118		118		130
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	27		27		33
Unpaid Principal Balance Individually Evaluated with No Related Allowance	91		91		97
Unpaid Principal Balance	118		118		130
Individually Evaluated Allowance	7		7		7
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	31	34	33	85
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	92	99	93	50
Average Impaired Finance Receivables	123	133	126	135
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	0	1	1
Interest Income Recognized Individually Evaluated with No Related Allowance	1	0	3	2
Interest Income Recognized	1	0	4	3
Working capital [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	23		23		24
Impaired Finance Receivables Individually Evaluated with No Related Allowance	4		4		5
Impaired Finance Receivables	27		27		29
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	23		23		24
Unpaid Principal Balance Individually Evaluated with No Related Allowance	4		4		5
Unpaid Principal Balance	27		27		29
Individually Evaluated Allowance	22		22		23
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	23	29	24	24
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	4	1	5	1
Average Impaired Finance Receivables	27	30	29	25
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	0	1	1
Interest Income Recognized Individually Evaluated with No Related Allowance	0	0	0	0
Interest Income Recognized	0	0	1	1
Retail Loan [Member]
Impaired Finance Receivables
Impaired Finance Receivables Aggregated And Evaluated For Impairment	345		345		415
Impaired Finance Receivables	345		345		415
Unpaid Principal Balance
Unpaid Principal Balance Aggregated And Evaluated For Impairment	341		341		410
Unpaid Principal Balance	341		341		410
Average Impaired Finance Receivables
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	355	458	379	473
Average Impaired Finance Receivables	355	458	379	473
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	7	10	22	29
Interest Income Recognized	7	10	22	29
Commercial [Member]
Impaired Finance Receivables
Impaired Finance Receivables Aggregated And Evaluated For Impairment	1		1		1
Impaired Finance Receivables	1		1		1
Unpaid Principal Balance
Unpaid Principal Balance Aggregated And Evaluated For Impairment	1		1		1
Unpaid Principal Balance	1		1		1
Average Impaired Finance Receivables
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	1	1	1	1
Average Impaired Finance Receivables	1	1	1	1
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	0	0	0	0
Interest Income Recognized	$ 0	$ 0	$ 0	$ 0