Amortized Cost and Fair Value of Available-for-Sale Securities and Held-to-Maturity Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale, Amortized Cost
Within one year	$ 830
One to five years	28,264
Five to ten years	1,493
After ten years	0
Totals	30,587
Available-for-sale, Fair Value
Within one year	833
One to five years	28,308
Five to ten years	1,505
After ten years	0
Totals	30,646	$ 19,348
Held-to-maturity, Amortized Cost
Within one year	235
One to five years	0
Five to ten years	0
After ten years	0
Totals	235	450
Held-to-maturity, Fair Value
Within one year	236
One to five years	0
Five to ten years	0
After ten years	0
Totals	$ 236	$ 19,348