Components of Net Deferred Taxes (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 6,647	$ 5,374
Vacation accrual	2,658	3,542
Pension accrual	4,425	7,455
Allowance for bad debts	2,226	2,166
Insurance accrual	2,425	19,914
Inventory capitalization	350	895
Other, net	1,382	2,242
Total deferred tax assets	20,113	41,588
Valuation allowance	(3,980)	(3,168)
Net deferred tax assets	16,133	38,420
Deferred tax liabilities:
Property and equipment	9,783	8,001
Fair value of derivative instruments	4,673	1,683
Intangibles	22,883	34,876
Total deferred tax liabilities	37,339	44,560
Net deferred tax liabilities	$ (21,206)	$ (6,140)