Business Combinations - Net Assets Acquired and Estimated Purchase Accounting Adjustments (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended
	Dec. 01, 2012
Business Acquisition [Line Items]
Purchase price	$ 1,516
Business acquisition adjustments to purchase price	244
Net assets acquired	859
Fair value of net assets acquired	1,103
Goodwill	413
Securities available for sale [Member]
Business Acquisition [Line Items]
Business acquisition adjustments to purchase price	8
Loans held for investment [Member]
Business Acquisition [Line Items]
Business acquisition adjustments to purchase price	141
Intangible assets [Member]
Business Acquisition [Line Items]
Business acquisition adjustments to purchase price	18
Other assets [Member]
Business Acquisition [Line Items]
Business acquisition adjustments to purchase price	128
Deposits [Member]
Business Acquisition [Line Items]
Business acquisition adjustments to purchase price	(12)
Other short-term borrowings [Member]
Business Acquisition [Line Items]
Business acquisition adjustments to purchase price	(36)
Long-term debt [Member]
Business Acquisition [Line Items]
Business acquisition adjustments to purchase price	(14)
Other Liabilities [Member]
Business Acquisition [Line Items]
Business acquisition adjustments to purchase price	$ 11