Finance Receivables, Net (Summary of Investment in Impaired Loans by Class of Finance Receivable) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2015
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	$ 234		$ 234		$ 162
Impaired Finance Receivables Individually Evaluated with No Related Allowance	268		268		198
Impaired Finance Receivables Aggregated And Evaluated For Impairment	237		237		264
Impaired Finance Receivables	739		739		624
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	234		234		162
Unpaid Principal Balance Individually Evaluated with No Related Allowance	268		268		198
Unpaid Principal Balance Aggregated And Evaluated For Impairment	234		234		261
Unpaid Principal Balance	736		736		621
Individually Evaluated Allowance	59		59		55
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	214	$ 54	205	$ 60
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	235	154	213	150
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	241	285	251	302
Average Impaired Finance Receivables	690	493	669	512
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	1	0	4	1
Interest Income Recognized Individually Evaluated with No Related Allowance	2	1	5	3
Interest Income Recognized Aggregated And Evaluated For Impairment	4	5	13	17
Interest Income Recognized	7	6	22	21
Wholesale [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	78		78		76
Impaired Finance Receivables Individually Evaluated with No Related Allowance	164		164		105
Impaired Finance Receivables	242		242		181
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	78		78		76
Unpaid Principal Balance Individually Evaluated with No Related Allowance	164		164		105
Unpaid Principal Balance	242		242		181
Individually Evaluated Allowance	11		11		14
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	77	17	83	17
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	136	62	119	56
Average Impaired Finance Receivables	213	79	202	73
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	0	1	0
Interest Income Recognized Individually Evaluated with No Related Allowance	1	0	2	1
Interest Income Recognized	1	0	3	1
Real estate [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	121		121		52
Impaired Finance Receivables Individually Evaluated with No Related Allowance	99		99		91
Impaired Finance Receivables	220		220		143
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	121		121		52
Unpaid Principal Balance Individually Evaluated with No Related Allowance	99		99		91
Unpaid Principal Balance	220		220		143
Individually Evaluated Allowance	15		15		10
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	103	14	87	20
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	94	89	90	91
Average Impaired Finance Receivables	197	103	177	111
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	1	0	2	0
Interest Income Recognized Individually Evaluated with No Related Allowance	1	1	3	2
Interest Income Recognized	2	1	5	2
Working capital [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	35		35		34
Impaired Finance Receivables Individually Evaluated with No Related Allowance	5		5		2
Impaired Finance Receivables	40		40		36
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	35		35		34
Unpaid Principal Balance Individually Evaluated with No Related Allowance	5		5		2
Unpaid Principal Balance	40		40		36
Individually Evaluated Allowance	33		33		31
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	34	23	35	23
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	5	3	4	3
Average Impaired Finance Receivables	39	26	39	26
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	237		237		264
Impaired Finance Receivables	237		237		264
Unpaid Principal Balance
Unpaid Principal Balance Aggregated And Evaluated For Impairment	234		234		261
Unpaid Principal Balance	234		234		261
Average Impaired Finance Receivables
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	241	284	251	301
Average Impaired Finance Receivables	241	284	251	301
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	4	5	13	17
Interest Income Recognized	4	5	13	17
Commercial Finance [Member]
Impaired Finance Receivables
Impaired Finance Receivables Aggregated And Evaluated For Impairment	0		0		0
Impaired Finance Receivables	0		0		0
Unpaid Principal Balance
Unpaid Principal Balance Aggregated And Evaluated For Impairment	0		0		0
Unpaid Principal Balance	0		0		$ 0
Average Impaired Finance Receivables
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	0	1	0	1
Average Impaired Finance Receivables	0	1	0	1
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	0	0	0	0
Interest Income Recognized	$ 0	$ 0	$ 0	$ 0