Finance Receivables, Net (Impaired Finance Receivables) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2013
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	$ 87		$ 73
Impaired Finance Receivables Individually Evaluated with No Related Allowance	153		168
Impaired Finance Receivables Aggregated And Evaluated For Impairment	390		416
Impaired Finance Receivables	630		657
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	87		73
Unpaid Principal Balance Individually Evaluated with No Related Allowance	153		168
Unpaid Principal Balance Aggregated And Evaluated For Impairment	386		411
Unpaid Principal Balance	626		652
Individually Evaluated Allowance	35		33
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	80	191
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	161	61
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	403	490
Average Impaired Finance Receivables	644	742
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	1	1
Interest Income Recognized Individually Evaluated with No Related Allowance	1	0
Interest Income Recognized Aggregated And Evaluated For Impairment	8	10
Interest Income Recognized	10	11
Wholesale [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	24		16
Impaired Finance Receivables Individually Evaluated with No Related Allowance	55		66
Impaired Finance Receivables	79		82
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	24		16
Unpaid Principal Balance Individually Evaluated with No Related Allowance	55		66
Unpaid Principal Balance	79		82
Individually Evaluated Allowance	4		3
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	20	23
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	60	60
Average Impaired Finance Receivables	80	83
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	0
Interest Income Recognized Individually Evaluated with No Related Allowance	0	0
Interest Income Recognized	0	0
Real estate [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	38		33
Impaired Finance Receivables Individually Evaluated with No Related Allowance	93		97
Impaired Finance Receivables	131		130
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	38		33
Unpaid Principal Balance Individually Evaluated with No Related Allowance	93		97
Unpaid Principal Balance	131		130
Individually Evaluated Allowance	7		7
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	36	137
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	96	0
Average Impaired Finance Receivables	132	137
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	1
Interest Income Recognized Individually Evaluated with No Related Allowance	1	0
Interest Income Recognized	1	1
Working capital [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	25		24
Impaired Finance Receivables Individually Evaluated with No Related Allowance	5		5
Impaired Finance Receivables	30		29
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	25		24
Unpaid Principal Balance Individually Evaluated with No Related Allowance	5		5
Unpaid Principal Balance	30		29
Individually Evaluated Allowance	24		23
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	24	31
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	5	1
Average Impaired Finance Receivables	29	32
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	1	0
Interest Income Recognized Individually Evaluated with No Related Allowance	0	0
Interest Income Recognized	1	0
Retail Loan [Member]
Impaired Finance Receivables
Impaired Finance Receivables Aggregated And Evaluated For Impairment	389		415
Impaired Finance Receivables	389		415
Unpaid Principal Balance
Unpaid Principal Balance Aggregated And Evaluated For Impairment	385		410
Unpaid Principal Balance	385		410
Average Impaired Finance Receivables
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	402	489
Average Impaired Finance Receivables	402	489
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	8	10
Interest Income Recognized	8	10
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