Reserve for Repurchased Loans and Loss Sharing Obligations - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014 SecurityLoan Investor	Dec. 31, 2013 SecurityLoan	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold to FHLB under loss sharing arrangement first loss position	1.00%
Loans sold to FHLB under loss sharing arrangement minimum exposure	1.50%
Loans sold to FHLB under loss sharing arrangement maximum loss position	4.00%
Reserve for repurchased loans and loss sharing obligations	$ 1,000,000	$ 1,500,000
(Decrease) increase in reserve for repurchased loans and loss sharing obligations	(436,000)	265,000
General provision for repurchased loans		975,000	750,000
Additional provision on FHLB loan sales		875,000
Incurred losses on loans	143,000	465,000
Reserve reduced by cash paid as part of settlement	293,000	450,000
Number of investors in comprehensive settlement	1
Recoveries from previous charged-off		205,000
Outstanding number of loan repurchase requests	0	5
Principal balance on loans repurchase		1,200,000
Repurchase Requests [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
General provision for repurchased loans		$ 100,000