Other Borrowings - Additional Information (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Debt Disclosure [Abstract]
Outstanding borrowings	$ 43,851,000us-gaap_OtherBorrowings	$ 78,881,000us-gaap_OtherBorrowings	$ 59,677,000us-gaap_OtherBorrowings
Borrowing available with FHLB	275,500,000
Credit arrangements for federal funds purchase	50,000,000
Loans pledged at federal reserve discount window	581,800,000
Loans pledged at federal reserve discount window available for borrowing	$ 409,700,000

Amount of advances or credit lines available from the Federal Home Loan Bank (FHLB).

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

-Publisher FASB

-Name Accounting Standards Codification

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Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresAmountOfAvailableUnusedFunds
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant