Fair Value Measurements - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Specific adjustments to impaired loans recognized	$ 947,000	$ 48,000
Transfers between level 1, 2 and 3	0
Liabilities measured at fair value on a recurring or nonrecurring basis	0	0
Transfers between level 1 and 2		0
Fair Value Measurements, Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized cost of Level 3 securities	97,760,000	37,463,000
Unrealized loss	$ 874,000	$ 866,000