Postretirement Benefits - Pension Amounts Recorded Within Account Line Items of Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Accrued compensation and benefits	$ 155	$ 298
Long-term pension liability	1,958	2,525
Pension and Other Postretirement Defined Benefit Plans, Liabilities	$ 2,113	$ 2,823