Related Party Transactions - Related Party Transactions Financing Support Provided by Parent and Affiliates (Details) € in Millions, CAD in Millions, $ in Millions	Mar. 31, 2017 USD ($)	Mar. 31, 2017 CAD	Mar. 31, 2017 EUR (€)	Mar. 31, 2016 USD ($)
Related Party Transaction [Line Items]
Amounts outstanding provided by parent and affiliates	$ 13			$ 20
TCCI [Member]
Related Party Transaction [Line Items]
Financing available to TMCC | CAD		CAD 1,500
Amounts outstanding provided by parent and affiliates	0			0
TMFNL [Member]
Related Party Transaction [Line Items]
Financing available to TMCC | €			€ 1,000
Amounts outstanding provided by parent and affiliates	0			0
TFSIC [Member]
Related Party Transaction [Line Items]
Financing available to TMCC	200
Amounts outstanding provided by parent and affiliates	5			12
TFA [Member]
Related Party Transaction [Line Items]
Financing available to TMCC	1,000
Amounts outstanding provided by parent and affiliates	0			0
TFSS USA [Member]
Related Party Transaction [Line Items]
Financing available to TMCC	15
Amounts outstanding provided by parent and affiliates	$ 8			$ 8