Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Specific adjustments to impaired loans recognized	$ (14,000)	$ 165,000
Transfers between level 1, 2 and 3	0
Liabilities measured at fair value on a recurring or nonrecurring basis	0
Transfers between level 1, 2 and 3		0
Liabilities measured at fair value on a recurring or nonrecurring basis		$ 0
Fair Value Measurements, Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized cost of Level 3 securities	135,490,000		$ 119,750,000
Unrealized loss	$ 401,000		$ 875,000