Fair Value Measurements - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands		Sep. 30, 2017	Sep. 30, 2016
Assets:
Total		$ 29,086	$ 11,456
Cash
Assets:
Cash equivalents	[1]	15,295	440
Marketable securities
Assets:
Marketable securities	[2]	13,791	11,016
Active Markets for Identical Instruments (Level 1)
Assets:
Total		29,086	11,456
Active Markets for Identical Instruments (Level 1) | Cash
Assets:
Cash equivalents	[1]	15,295	440
Active Markets for Identical Instruments (Level 1) | Marketable securities
Assets:
Marketable securities	[2]	$ 13,791	$ 11,016

[1] Included in cash and cash equivalents on our balance sheet at September 30, 2017 and 2016. Not included in this table are cash deposits of $90.3 million and $75.5 million at September 30, 2017 and 2016, respectively.

[2] Represents securities held under a supplemental retirement and savings plan for certain officers and senior management employees, which are distributed upon termination or retirement of the employees. Included in long-term marketable securities on our balance sheet at September 30, 2017 and 2016.