Finance Receivables, Net (Impaired Finance Receivables) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Mar. 31, 2012
Recorded Investment
Recorded Investment Individually Evaluated with Related Allowance	$ 192		$ 150
Recorded Investment Individually Evaluated with No Related Allowance	66		61
Recorded Investment Account Balances Aggregated And Evaluated For Impairment	477		503
Recorded Investment	735		714
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	192		150
Unpaid Principal Balance Individually Evaluated with No Related Allowance	66		61
Unpaid Principal Balance Aggregated And Evaluated For Impairment	472		497
Unpaid Principal Balance	730		708
Individually Evaluated Allowance	75		45
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	191	161
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	61	43
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	490	580
Average Impaired Finance Receivables	742	784
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	1	1
Interest Income Recognized Individually Evaluated with No Related Allowance	0	1
Interest Income Recognized Aggregated And Evaluated For Impairment	10	12
Interest Income Recognized	11	14
Wholesale [Member]
Recorded Investment
Recorded Investment Individually Evaluated with Related Allowance	25		7
Recorded Investment Individually Evaluated with No Related Allowance	65		60
Recorded Investment	90		67
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	25		7
Unpaid Principal Balance Individually Evaluated with No Related Allowance	65		60
Unpaid Principal Balance	90		67
Individually Evaluated Allowance	5		1
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	23	10
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	60	42
Average Impaired Finance Receivables	83	52
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	0
Interest Income Recognized Individually Evaluated with No Related Allowance	0	1
Interest Income Recognized	0	1
Real estate [Member]
Recorded Investment
Recorded Investment Individually Evaluated with Related Allowance	137		136
Recorded Investment Individually Evaluated with No Related Allowance	0		0
Recorded Investment	137		136
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	137		136
Unpaid Principal Balance Individually Evaluated with No Related Allowance	0		0
Unpaid Principal Balance	137		136
Individually Evaluated Allowance	41		37
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	137	137
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	0	0
Average Impaired Finance Receivables	137	137
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	1	1
Interest Income Recognized Individually Evaluated with No Related Allowance	0	0
Interest Income Recognized	1	1
Working capital [Member]
Recorded Investment
Recorded Investment Individually Evaluated with Related Allowance	30		7
Recorded Investment Individually Evaluated with No Related Allowance	1		1
Recorded Investment	31		8
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	30		7
Unpaid Principal Balance Individually Evaluated with No Related Allowance	1		1
Unpaid Principal Balance	31		8
Individually Evaluated Allowance	29		7
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	31	14
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	1	1
Average Impaired Finance Receivables	32	15
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
Retail Loan [Member]
Recorded Investment
Recorded Investment Account Balances Aggregated And Evaluated For Impairment	476		502
Recorded Investment	476		502
Unpaid Principal Balance
Unpaid Principal Balance Aggregated And Evaluated For Impairment	471		496
Unpaid Principal Balance	471		496
Average Impaired Finance Receivables
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	489	577
Average Impaired Finance Receivables	489	577
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	10	12
Interest Income Recognized	10	12
Commercial [Member]
Recorded Investment
Recorded Investment Account Balances Aggregated And Evaluated For Impairment	1		1
Recorded Investment	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	3
Average Impaired Finance Receivables	1	3
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	0	0
Interest Income Recognized	$ 0	$ 0