Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Current:
Federal	$ 18,724	$ 28,793	$ 19,747
State	5,344	8,143	4,909
Deferred
Federal	7,485	(3,719)	596
State	2,185	(382)	63
Income tax expense	$ 33,738	$ 32,835	$ 25,315