Commitments and Contingencies - Additional Information (Details) - USD ($)	6 Months Ended
Sep. 30, 2019	Mar. 31, 2019
Commitments And Contingencies [Line Items]
Commitments under operating lease agreements	$ 119,000,000
Lease description	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 lease expense, including payments to affiliates	$ 18,000,000
TMCC-affiliated companies [Member]
Commitments And Contingencies [Line Items]
Commitments under operating lease agreements	76,000,000	$ 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

Commitments and contingencies.

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- Definition

Provision for indemnification.

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- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
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Date which lease or group of leases is set to expire, in CCYY-MM-DD format.

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- Definition

Description of lessee's operating lease.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
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Present value of lessee's discounted obligation for lease payments from operating lease.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
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- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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