Related Party Transactions - Related Party Transactions Financing Support Provided to 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 to affiliates	$ 823			$ 1,177
TFSB [Member]
Related Party Transaction [Line Items]
Financing made available by TMCC	400
Amounts outstanding provided to affiliates	0			0
TCCI [Member]
Related Party Transaction [Line Items]
Financing made available by TMCC | CAD		CAD 2,500
Amounts outstanding provided to affiliates	0			220
TMFNL [Member]
Related Party Transaction [Line Items]
Financing made available by TMCC | €			€ 1,000
Amounts outstanding provided to affiliates	407			619
TFSIC [Member]
Related Party Transaction [Line Items]
Financing made available by TMCC	200
Amounts outstanding provided to affiliates	0			0
TFSMX [Member]
Related Party Transaction [Line Items]
Financing made available by TMCC	500
Amounts outstanding provided to affiliates	0			0
BTB [Member]
Related Party Transaction [Line Items]
Financing made available by TMCC	300
Amounts outstanding provided to affiliates	116			58
TFA [Member]
Related Party Transaction [Line Items]
Financing made available by TMCC	1,000
Amounts outstanding provided to affiliates	$ 300			$ 280