Securities - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Schedule Of Marketable Securities [Line Items]
Fair Value of Investment in debt securities		$ 18,000,000		$ 24,000,000
Percentage of fair value of investment in debt		56.50%		69.20%
Proceeds from sale of available-for-sale securities	$ 13,000	$ 0	$ 383,000
Available-for-sale securities realized gains	11,000		31,000
Available-for-sale securities realized losses	0		0
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax	$ 3,000		$ 4,000