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Employee Benefit Plans - Multi-Employer Plan (Details)
3 Months Ended 12 Months Ended
Sep. 30, 2018
USD ($)
quarter
hour
plan
Sep. 30, 2017
USD ($)
Jun. 30, 2012
USD ($)
quarter
Jun. 30, 2018
USD ($)
Jan. 05, 2015
USD ($)
Nov. 18, 2014
USD ($)
Multiemployer Plans [Line Items]            
Defined Contribution Plan, Employer Matching Contribution, Amount $ 500,000          
Multiemployer plans, number of plans | plan 2          
Defined contribution plan, hours threshold for eligibility | hour 1,000          
Defined contribution plan, employer matching contribution percent 50.00%          
Defined contribution plan, employer matching contribution, percent of eligible income 6.00%          
Defined contribution plan, employer matching contribution, annual vesting percent 20.00%          
Defined contribution plan, vesting period 5 years          
Defined contribution plan, automatic vesting age 65 years          
Defined contribution plan, employee vesting percent 100.00%          
WCTPP [Member]            
Multiemployer Plans [Line Items]            
Multiemployer plan, quarterly installments for withdrawal liability, number of quarters | quarter 18          
Labor Management Pension Fund            
Multiemployer Plans [Line Items]            
Withdrawal obligation $ 3,000,000   $ 4,300,000 $ 3,800,000 $ 4,900,000 $ 4,400,000
Multiemployer plan, quarterly installments for withdrawal liability     $ 100,000      
Multiemployer plan, quarterly installments for withdrawal liability, number of quarters | quarter     80      
Multiemployer Plans, Pension | Multiemployer Plans, Defined Benefit Pension Plans [Member]            
Multiemployer Plans [Line Items]            
Multiemployer plans, number of plans | plan 2          
Other Postretirement Benefit Plan            
Multiemployer Plans [Line Items]            
Defined Benefit Plan, Service Cost $ 133,000 $ 152,000        
Multiemployer plans, number of plans | plan 9          
Defined Benefit Plan, Interest Cost $ 222,000 209,000        
Defined Benefit Plan, Amortization of Gain (Loss) (209,000) (210,000)        
Amortization of prior service credit (439,000) (439,000)        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) (293,000) $ (288,000)        
Employee-related | WCTPP [Member]            
Multiemployer Plans [Line Items]            
Withdrawal obligation 3,200,000          
Multiemployer plan, quarterly installments for withdrawal liability $ 190,507