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Employee Benefit Plans - Additional Information (Detail)
12 Months Ended
Sep. 30, 2022
Sep. 30, 2021
USD ($)
Employee
Program
$ / shares
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Sep. 30, 2015
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Maximum participant contribution   60.00%      
Partnership aggregate contributions to defined contribution plans   $ 8,200,000 $ 7,900,000 $ 7,600,000  
Multiemployer pension plans, coverage of bargaining agreement, percentage   44.00%      
Maximum funded for red zone   65.00%      
Maximum funded for yellow zone   80.00%      
Minimum funded for green zone   80.00%      
Partnership contributions in excess of 5% of the plan's total contributions in percentage   5.00% 5.00% 5.00%  
Minimum contribution required   $ 0 $ 0 $ 0  
Accrued expenses and other current liabilities   121,221,000 127,286,000    
Other long-term liabilities   25,244,000 25,001,000    
Defined benefit plan funded status included in deferred charges and other assets   4,000,000.0 $ 3,700,000    
Net actuarial loss balance in accumulated other comprehensive income to be amortized   11,500,000      
Amount to be amortized from accumulated other comprehensive income   $ 900,000      
Discount rate to determine periodic pension expense   2.65% 2.45% 3.00%  
Expected optional pension contribution   $ 0      
Expected benefit payments for year one   4,200,000      
Expected benefit payments for year two   4,200,000      
Expected benefit payments for year three   4,200,000      
Expected benefit payments for year four   4,200,000      
Expected benefit payments for year five   4,200,000      
Aggregate expected benefit payment for five years thereafter   $ 17,700,000      
Cash and Cash Equivalents          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Pension asset allocation   1.00%      
Scenario Forecast          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Rate pension plan assets expect to earn 3.80%        
Renewal within Next Fiscal Year          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Multiemployer pension plans, coverage of bargaining agreement, percentage   10.00%      
Management          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Incentive distribution percentage of available cash in excess of minimum quarterly distribution   50.00%      
Gains interest cash proceeds percentage from the sale of general partner units   50.00%      
Employee and Consultant          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Participant's vested percentage of plan benefits   100.00%      
Termination of employment or consultation          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Participant's vested percentage of plan benefits   20.00%      
Chief executive officer          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Participant's vested percentage of plan benefits   33.333%      
Management And General Partner          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Partnership incentive distribution   $ 1,833,000 $ 1,654,000 $ 1,464,000  
Management Incentive Compensation Plan          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Partnership incentive distribution   917,000 827,000 732,000  
Management Incentive Compensation Plan Executive Officer          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Partnership incentive distribution   $ 386,857 349,494 397,430  
Minimum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Participant Contribution   0.00%      
Minimum | Management          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Quarterly distribution | $ / shares   $ 0.0675      
Other Postretirement Benefit Plan, Defined Benefit          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Partnership aggregate contributions to defined contribution plans   $ 600,000 $ 600,000 $ 600,000  
New England Teamsters & Trucking Industry Pension Fund          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Multiemployer plan undiscounted withdrawal obligation         $ 48,000,000.0
Expected benefit payments in years         30 years
Multiemployer plan annual liability annual payment amount         $ 1,600,000
Accrued expenses and other current liabilities   200,000      
Other long-term liabilities   16,500,000      
New England Teamsters & Trucking Industry Pension Fund | Significant Other Observable Inputs Level 2          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Multiemployer plan discounted withdrawal liability   $ 25,800,000      
New England Teamsters & Trucking Industry Pension Fund | Multiemployer Pension Plans          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Maximum funded for red zone   65.00%      
New England Teamsters & Trucking Industry Pension Fund | Minimum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of employees | Employee   200      
Frozen Defined Benefit Pension Plans          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of frozen defined benefit pension plans | Program   2      
Domestic Fixed Income          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Pension asset allocation   90.00%      
Domestic Equities          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Pension asset allocation   7.00%      
International equity          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Pension asset allocation   2.00%