Securities - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Schedule Of Marketable Securities [Line Items]
Fair Value of Investment in debt securities	$ 5,000,000		$ 7,100,000
Percentage of fair value of investment in debt	16.18%		35.70%
Available-for-sale securities realized gains	$ 31,000	$ 27,000
Available-for-sale Securities Pledged as Collateral	$ 25,900,000		$ 19,500,000