Captive Insurance Collateral - Schedule of Captive Insurance Collateral to be Available-for-sale Investments (Detail) - USD ($) $ in Thousands		Mar. 31, 2019	Sep. 30, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		$ 54,056	$ 46,623
Gross Unrealized Gain		127
Gross Unrealized (Loss)		(35)	(1,204)
Fair Value	[1]	54,148	45,419
Cash and Receivables
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		376	350
Fair Value		376	350
U.S. Government Sponsored Agencies
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		24,290	10,735
Gross Unrealized Gain		49
Gross Unrealized (Loss)		(2)	(192)
Fair Value		24,337	10,543
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		25,298	30,427
Gross Unrealized Gain		76
Gross Unrealized (Loss)		(27)	(928)
Fair Value		25,347	29,499
Foreign Bonds and Notes
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		4,092	5,111
Gross Unrealized Gain		2
Gross Unrealized (Loss)		(6)	(84)
Fair Value		$ 4,088	$ 5,027

[1] See Note 2 – Significant Accounting Policies – Captive Insurance Collateral.