Loans - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Accounts Notes And Loans Receivable [Line Items]
Evaluation period of net charge-off history	2 years 6 months		2 years
Amounts charged off	$ 712,000	$ 1,164,000
Period of cumulative homogeneous loans past due included in company analysis	90 days
TDRs [Member]
Accounts Notes And Loans Receivable [Line Items]
Increment in allowance for loan losses	58,000	56,000
Amounts charged off	0	0
TDRs with Subsequent Default [Member]
Accounts Notes And Loans Receivable [Line Items]
Amounts charged off	0	0
Effect of troubled debt restructurings on provision for loan losses	$ 0	$ 0
Majority [Member]
Accounts Notes And Loans Receivable [Line Items]
Term of loan commitments	60 days
Maximum [Member]
Accounts Notes And Loans Receivable [Line Items]
Term of loan commitments	36 months