Related Party Transactions - Related Party Transactions Financing Support Provided to Parent and Affiliates (Details) In Millions, unless otherwise specified	Mar. 31, 2015 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2015 TFSB [Member] USD ($)	Mar. 31, 2014 TFSB [Member] USD ($)	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 TFSMX [Member] USD ($)	Mar. 31, 2014 TFSMX [Member] USD ($)	Mar. 31, 2015 BTB [Member] USD ($)	Mar. 31, 2014 BTB [Member] USD ($)	Mar. 31, 2015 TFA [Member] USD ($)	Mar. 31, 2014 TFA [Member] USD ($)
Related Party Transaction [Line Items]
Financing made available by TMCC			$ 400			2,500			€ 1,000		$ 200		$ 500		$ 300		$ 1,000
Amounts outstanding provided to affiliates	$ 1,184	$ 1,172	$ 25	$ 40	$ 0		$ 0	$ 778		$ 827	$ 0	$ 0	$ 0	$ 0	$ 81	$ 105	$ 300	$ 200