Loans and Allowance for Loan Losses - Summary of Loans (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and industrial	$ 20,827		$ 19,226
Commercial mortgage	9,939		8,175
Construction	627		870
Lease financing	1,104		965
Total commercial portfolio	32,497		29,236
Residential mortgage	22,705		19,625
Home equity and other consumer loans	3,647		3,730
Total consumer portfolio	26,352		23,355
Total loans held for investment, before purchased credit-impaired loans	58,849		52,591
Purchased credit-impaired loans	1,185	[1]	949	[1]
Total loans held for investment	60,034	[2]	53,540	[2]
Allowance for loan losses	(653)		(764)
Loans held for investment, net	$ 59,381		$ 52,776

[1] Includes $421 million and $949 million as of December 31, 2012 and 2011, respectively, of loans for which the Company will be reimbursed a substantial portion of any future losses under the terms of the FDIC loss share agreements. Of these FDIC covered loans, $24 million and $47 million as of December 31, 2012 and 2011, respectively, were not accounted for under accounting guidance for loans acquired with deteriorated credit quality.

[2] Includes $5 million and ($30) million at December 31, 2012 and 2011, respectively, for net unamortized discounts and premiums and deferred fees and costs.