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Bank Credit Arrangements - Additional Information (Detail) - USD ($)		12 Months Ended
	May 24, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	May 31, 2019	Mar. 22, 2016
Debt Instrument [Line Items]
Interest rate swap asset			$ 1,722,000
Cash paid for interest		$ 1,405,000	1,487,000	$ 1,605,000
Interest rate swap balance reflected within other comprehensive income		$ (1,159,000)	907,000	$ 1,544,000
Fixed interest rate		2.76%
Fair value of interest rate swap					$ 563,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument effective interest rate		3.78%
Line of credit facility borrowing Capacity	$ 125,000,000
Draws on credit facility		$ 75,824,000
Expiration of credit facility	May 2024
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Interest rate swap balance reflected within other comprehensive income		$ 461,000	1,722,000
Five - Year Term Loan [Member] \| Magellan [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 50,180,000			$ 60,000,000
Long-term Debt, Term		5 years