Disclosures about Fair Value of Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Five-year Senior Unsecured Notes [Member]	Sep. 30, 2013 Five-year Senior Unsecured Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale, average life from purchase to sale	17 days
Issuance of senior unsecured notes		$ 25	$ 63