Loans and Leases - Additional Information (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable
Unamortized premiums and discounts, deferred loan fees and costs, and fair value adjustments	$ 86,000,000	$ 73,000,000
Loans and Leases Net of Unearned Income	736,000,000	758,000,000
Loans pledged at the FHLB	12,600,000,000	12,700,000,000
Loans pledged at the FRB	$ 33,100,000,000	$ 30,900,000,000

Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6378536&loc=d3e10092-111533

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 91

-Paragraph 21

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Balance Type:	debit
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