Fair Value Measurement - Schedule of Assets Measured at Fair Value on Nonrecurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other real estate owned and repossessed assets	6,226	5,082
Nonrecurring Fair Value Measurements [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	4,533	6,024
Other real estate owned and repossessed assets	6,226	5,082
Significant Unobservable Inputs (Level 3) [Member] | Nonrecurring Fair Value Measurements [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	4,533	6,024
Other real estate owned and repossessed assets	6,226	5,082
Minimum [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans, Appraisal adjustments	0.00%	0.00%
Impaired loans, Liquidation expenses	(3.10%)	(1.20%)
Maximum [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans, Appraisal adjustments	(38.50%)	(39.70%)
Impaired loans, Liquidation expenses	(8.00%)	(8.00%)
Weighted Average [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans, Appraisal adjustments	(6.90%)	(6.70%)
Impaired loans, Liquidation expenses	(7.40%)	(6.70%)