Allowance for Credit Losses - Additional Information (Details) - Finance Receivables, Net [Member] - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: Collectively evaluated for impairment	$ 73,323	$ 70,049
Retail and Commercial Loan [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Impaired finance receivables aggregated and collectively evaluated for impairment	243	216
Dealer Products [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: Collectively evaluated for impairment	16,721	16,092
TMNA [Member] | Financial Guarantee [Member] | Dealer Products [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: Collectively evaluated for impairment	1,052	1,054
Private Toyota Distributors [Member] | Financial Guarantee [Member] | Dealer Products [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: Collectively evaluated for impairment	$ 131	$ 137