Significant Accounting Policies (Tables)

12 Months Ended

Sep. 30, 2021

Accounting Policies [Abstract]

Schedule of customer concentration risk

Customers that accounted for more than 10% of consolidated revenues during fiscal years ended September 30, 2021, 2020 and 2019 are presented below:

	% of Consolidated Revenues for the Fiscal Year Ended September 30,
	2021	2020	2019
Alabama Department of Transportation	10.8%	11.6%	13.8%
North Carolina Department of Transportation	10.3%	7.8%	13.1%

Schedule of revenue by major customers by reporting segments

The following table reflects, for the periods presented, (i) revenues generated from public infrastructure construction projects and the sale of construction materials to public customers and (ii) revenues generated from private infrastructure construction projects and the sale of construction materials to private customers.

	% of Consolidated Revenues for the Fiscal Year Ended September 30,
	2021	2020	2019
Public	61.3%	65.3%	69.3%
Private	38.7%	34.7%	30.7%

Schedule of useful lives of property, plant and equipment

The estimated useful lives of property, plant and equipment categories are as follows:

Category	Estimated Useful Life
Land and improvements	Land, unlimited; improvements, 15-25 years
Mineral reserves	Based on depletion
Buildings	5 - 39 years
Plants	3 - 20 years
Construction equipment	3 - 10 years
Furniture and fixtures	5 - 10 years
Leasehold improvements	The shorter of 15 years or the remaining lease term

Property, plant and equipment at September 30, 2021 and 2020 consisted of the following (in thousands):

	September 30,
	2021		2020
Construction equipment	$	333,966	$	253,157
Plants	143,172		102,392
Land and improvements	53,415		38,647
Mineral reserves	86,556		22,205
Buildings	27,163		18,307
Furniture and fixtures	6,426		5,648
Leasehold improvements	1,230		1,135
Total property, plant and equipment, gross	651,928		441,491
Accumulated depreciation, depletion and amortization	(250,803)		(209,532)
Construction in progress	3,707		5,271
Total property, plant and equipment, net	$	404,832	$	237,230