Related Party Transactions - Related Party Transactions Financing Support Provided by Parent and Affiliates (Details) In Millions, unless otherwise specified	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2015 TCCI [Member] USD ($)	Mar. 31, 2015 TCCI [Member] CAD	Mar. 31, 2014 TCCI [Member] USD ($)	Mar. 31, 2015 TMFNL [Member] USD ($)	Mar. 31, 2015 TMFNL [Member] EUR (€)	Mar. 31, 2014 TMFNL [Member] USD ($)	Mar. 31, 2015 TFSA [Member] USD ($)	Mar. 31, 2014 TFSA [Member] USD ($)	Mar. 31, 2015 TFA [Member] USD ($)	Mar. 31, 2014 TFA [Member] USD ($)
Related Party Transaction [Line Items]
Financing available to TMCC	$ 0			1,500			€ 1,000		$ 200		$ 1,000
Amounts outstanding provided by parent and affiliates	$ 24	$ 22	$ 0		$ 0	$ 0		$ 0	$ 24	$ 22	$ 0	$ 0