Finance Receivables, Net (Summary of Impaired Loans by Class of Finance Receivable) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	$ 228		$ 228		$ 218
Impaired Finance Receivables Individually Evaluated with No Related Allowance	230		230		239
Impaired Finance Receivables	680		680		677
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	228		228		218
Unpaid Principal Balance Individually Evaluated with No Related Allowance	230		230		239
Unpaid Principal Balance	678		678		674
Individually Evaluated Allowance	52		52		33
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	218	$ 200	229	$ 204
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	213	237	224	266
Average Impaired Finance Receivables	652	658	675	693
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	1	1	5	4
Interest Income Recognized Individually Evaluated with No Related Allowance	4	2	8	7
Interest Income Recognized	8	7	24	23
Wholesale [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	111		111		93
Impaired Finance Receivables Individually Evaluated with No Related Allowance	74		74		134
Impaired Finance Receivables	185		185		227
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	111		111		93
Unpaid Principal Balance Individually Evaluated with No Related Allowance	74		74		134
Unpaid Principal Balance	185		185		227
Individually Evaluated Allowance	16		16		12
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	93	78	101	73
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	86	125	110	158
Average Impaired Finance Receivables	179	203	211	231
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	1	0	2	1
Interest Income Recognized Individually Evaluated with No Related Allowance	1	1	3	3
Interest Income Recognized	2	1	5	4
Real estate [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	80		80		94
Impaired Finance Receivables Individually Evaluated with No Related Allowance	134		134		105
Impaired Finance Receivables	214		214		199
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	80		80		94
Unpaid Principal Balance Individually Evaluated with No Related Allowance	134		134		105
Unpaid Principal Balance	214		214		199
Individually Evaluated Allowance	3		3		12
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	84	89	89	97
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	116	112	108	107
Average Impaired Finance Receivables	200	201	197	204
Interest Income Recognized
Interest Income Recognized Individually Evaluated with Related Allowance	0	1	2	2
Interest Income Recognized Individually Evaluated with No Related Allowance	2	1	4	4
Interest Income Recognized	2	2	6	6
Working capital [Member]
Impaired Finance Receivables
Impaired Finance Receivables Individually Evaluated with Related Allowance	37		37		31
Impaired Finance Receivables Individually Evaluated with No Related Allowance	22		22		0
Impaired Finance Receivables	59		59		31
Unpaid Principal Balance
Unpaid Principal Balance Individually Evaluated with Related Allowance	37		37		31
Unpaid Principal Balance Individually Evaluated with No Related Allowance	22		22		0
Unpaid Principal Balance	59		59		31
Individually Evaluated Allowance	33		33		9
Average Impaired Finance Receivables
Average Impaired Finance Receivables Individually Evaluated For Impairment with An Allowance	41	33	39	34
Average Impaired Finance Receivables Individually Evaluated For Impairment Without An Allowance	11	0	6	1
Average Impaired Finance Receivables	52	33	45	35
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	1	0
Interest Income Recognized	1	0	2	1
Retail Loan [Member]
Impaired Finance Receivables
Impaired Finance Receivables Aggregated And Evaluated For Impairment	222		222		220
Impaired Finance Receivables	222		222		220
Unpaid Principal Balance
Unpaid Principal Balance Aggregated And Evaluated For Impairment	220		220		217
Unpaid Principal Balance	220		220		$ 217
Average Impaired Finance Receivables
Average Impaired Finance Receivables Account Balances Aggregated And Evaluated For Impairment	221	221	222	223
Average Impaired Finance Receivables	221	221	222	223
Interest Income Recognized
Interest Income Recognized Aggregated And Evaluated For Impairment	3	4	11	12
Interest Income Recognized	$ 3	$ 4	$ 11	$ 12

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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