Investments - Sales of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 19,071	$ 65,455	$ 21,722	$ 157,970
Gross realized gains	26		26	126
Gross realized losses	$ (65)		$ (73)	$ (1)