Investments - Schedule of Investments to be Available-for-sale (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Sep. 30, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		$ 51,068	$ 46,623
Gross Unrealized (Loss)		(815)	(1,204)
Fair Value	[1]	50,253	45,419
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		416	350
Fair Value		416	350
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		16,208	10,735
Gross Unrealized (Loss)		(55)	(192)
Fair Value		16,153	10,543
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		29,344	30,427
Gross Unrealized (Loss)		(701)	(928)
Fair Value		28,643	29,499
Foreign Bonds and Notes
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		5,100	5,111
Gross Unrealized (Loss)		(59)	(84)
Fair Value		$ 5,041	$ 5,027

[1] See Note 2 – Investments