Investments in debt and equity securities available-for-sale - Debt Securities According to Contractual Terms (Detail) $ in Thousands	Sep. 30, 2015 USD ($)
Amortized costs
In one year or less	$ 26,212
After one year through five years	238,660
After five years through ten years	205,953
After ten years	38,320
Amortized costs, total	509,145
Fair values
In one year or less	26,443
After one year through five years	245,170
After five years through ten years	212,373
After ten years	40,051
Debt securities, fair values total	$ 524,037