Fair Value Measurements - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands		Sep. 30, 2018	Sep. 30, 2017
Assets:
Total		$ 36,472	$ 29,086
Cash
Assets:
Cash equivalents	[1]	18,413	15,295
Marketable securities
Assets:
Debt Securities, Trading, and Equity Securities, FV-NI	[2]	18,059	13,791
Active Markets for Identical Instruments (Level 1)
Assets:
Total		36,472	29,086
Active Markets for Identical Instruments (Level 1) | Cash
Assets:
Cash equivalents	[1]	18,413	15,295
Active Markets for Identical Instruments (Level 1) | Marketable securities
Assets:
Debt Securities, Trading, and Equity Securities, FV-NI	[2]	$ 18,059	$ 13,791

[1] Included in cash and cash equivalents on our balance sheet at September 30, 2018 and 2017. Not included in this table are cash deposits of $71.6 million and $90.3 million at September 30, 2018 and 2017, 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 consolidated balance sheets at September 30, 2018 and 2017.