Long-Term Debt - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014	Mar. 31, 2014
Parent company | Senior Debt Obligations | Fixed Rate 2.30 Percent Notes Due 2019
Debt Instrument
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 | Variable Interest Entity, Primary Beneficiary | Automobile Loan
Debt Instrument
Other Long Term Debt	2,800,000,000
Subsidiaries | Senior Debt Obligations
Debt Instrument
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
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
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