Commitments and Contingencies - Additional Information (Details) - USD ($)	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Commitments And Contingencies [Line Items]
Commitments under operating lease agreements	$ 120,000,000
Lease description	Lease terms may contain renewal and extension options or early termination features. Generally, these options do not impact the lease term because TMCC is not reasonably certain that it will exercise the options. These lease agreements do not impose restrictions on our ability to pay dividends, engage in debt or equity financing transactions or enter into further lease agreements, nor do they have residual value guarantees. We exclude from our Consolidated Balance Sheets leases with a term equal to one year or less and do not separate non-lease components from our real estate leases.
Indemnification provisions	$ 0	$ 0
Putnam and Gibson Counties [Member] | Performance Guarantee [Member]
Commitments And Contingencies [Line Items]
Guarantees of affiliate pollution control and solid waste disposal bonds	$ 100,000,000	100,000,000
TMNA [Member]
Commitments And Contingencies [Line Items]
Lease agreement expiration date	Aug. 31, 2032
Total operating lease expense, including payments to affiliates	$ 36,000,000	30,000,000	$ 30,000,000
TMCC-affiliated companies [Member]
Commitments And Contingencies [Line Items]
Commitments under operating lease agreements	102,000,000	$ 97,000,000
TMCC-affiliated companies [Member] | Putnam and Gibson Counties [Member] | Performance Guarantee [Member]
Commitments And Contingencies [Line Items]
Guarantees of affiliate pollution control and solid waste disposal bonds	100,000,000
TMCC-affiliated companies [Member] | Putnam and Gibson Counties [Member] | Performance Guarantee [Member] | 2028 [Member]
Commitments And Contingencies [Line Items]
Guarantees of affiliate pollution control and solid waste disposal bonds	20,000,000
TMCC-affiliated companies [Member] | Putnam and Gibson Counties [Member] | Performance Guarantee [Member] | 2029 [Member]
Commitments And Contingencies [Line Items]
Guarantees of affiliate pollution control and solid waste disposal bonds	50,000,000
TMCC-affiliated companies [Member] | Putnam and Gibson Counties [Member] | Performance Guarantee [Member] | 2030 [Member]
Commitments And Contingencies [Line Items]
Guarantees of affiliate pollution control and solid waste disposal bonds	10,000,000
TMCC-affiliated companies [Member] | Putnam and Gibson Counties [Member] | Performance Guarantee [Member] | 2031 [Member]
Commitments And Contingencies [Line Items]
Guarantees of affiliate pollution control and solid waste disposal bonds	10,000,000
TMCC-affiliated companies [Member] | Putnam and Gibson Counties [Member] | Performance Guarantee [Member] | 2032 [Member]
Commitments And Contingencies [Line Items]
Guarantees of affiliate pollution control and solid waste disposal bonds	$ 10,000,000