Fair Value Measurements - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands		Jun. 30, 2019	Sep. 30, 2018
Assets:
Marketable securities			$ 18,059
Cash deposits		$ 52,900	71,600
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	[1]	25,944	18,413
Marketable securities	[2]	20,054	18,059
Total		45,998	36,472
Fair Value, Measurements, Recurring | Active Markets for Identical Instruments (Level 1)
Assets:
Cash equivalents	[1]	25,944	18,413
Marketable securities	[2]	20,054	18,059
Total		$ 45,998	$ 36,472

[1] Included in cash and cash equivalents on our condensed consolidated balance sheets at June 30, 2019 and September 30, 2018. Not included in these tables are cash deposits of $52.9 million and $71.6 million at June 30, 2019 and September 30, 2018, respectively.

[2] Represents securities held under a supplemental retirement and savings plan for senior management employees, which are distributed upon termination or retirement of the employees. Included in marketable securities on our condensed consolidated balance sheets at June 30, 2019 and September 30, 2018.