Long-Term Debt - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Parent company | Variable Interest Entity, Primary Beneficiary | Automobile Loan Securitizations
Debt Instrument [Line Items]
Other Long Term Debt	$ 2,800,000,000
Parent company | Senior Debt Obligations | Fixed Rate 2.30 Percent Notes Due 2019
Debt Instrument [Line Items]
Issue of senior notes to third party investors	500,000,000
Maturity date(s) Start	Feb. 28, 2014
Maturity date(s) End	Mar. 01, 2019
Parent company | Senior Debt Obligations | Fixed Rate 2.875% senior notes due 2021
Debt Instrument [Line Items]
Issue of senior notes to third party investors	850,000,000
Maturity date(s) Start	Sep. 05, 2014
Maturity date(s) End	Oct. 01, 2021
Subsidiaries | Senior Debt Obligations
Debt Instrument [Line Items]
Issue of senior notes to third party investors	1,500,000,000
Subsidiaries | Senior Debt Obligations | Fixed rate 2.375% senior notes due 2019
Debt Instrument [Line Items]
Issue of senior notes to third party investors	850,000,000
Maturity date(s) Start	Apr. 25, 2014
Maturity date(s) End	Apr. 25, 2019
Subsidiaries | Senior Debt Obligations | Fixed rate 1.35% senior notes due 2017
Debt Instrument [Line Items]
Issue of senior notes to third party investors	$ 650,000,000
Maturity date(s) Start	Apr. 25, 2014
Maturity date(s) End	Jun. 01, 2017