Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Commitments And Contingencies [Line Items]
Off-balance Sheet Risks, Amount, Liability	338,000	$ 319,000
Reserve for sold mortgages	264,000
Notional amount of RPAs	19,400,000
Negative fair value of RPAs	1,200,000
Interest-earning deposit accounts pledged for Risk Participation Agreements	370,000	690,000
Approximate payment required in event of default of RPAs	1,200,000
Fair value of risk participation agreement guarantee	74,000
Future Rental Income Receivable Under Subleases	183,000
Letter of Credit [Member]
Commitments And Contingencies [Line Items]
Current carrying amount of the contingent obligation	441,000
Minimum [Member]
Commitments And Contingencies [Line Items]
Term of letter of credit	1 year
Terms of the underlying swaps	10 years
Maximum [Member]
Commitments And Contingencies [Line Items]
Term of letter of credit	5 years
Terms of the underlying swaps	13 years
Maximum [Member] | Letter of Credit [Member]
Commitments And Contingencies [Line Items]
Off-balance Sheet Risks, Amount, Liability	46,900,000