Mortgage Banking Activities - Additional Information (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Mortgage Banking [Abstract]
Mortgage loans serviced for others	$ 1,100,000,000	$ 1,100,000,000
Total services loans	1,100,000	1,700,000
Fair value of mortgage servicing rights	$ 9,900,000	$ 6,800,000

The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes and insurance obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments. This element excludes replacement reserves which are an escrow separately provided for within the US GAAP taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.10)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Name:	us-gaap_EscrowDeposit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant