Construction Partners, Inc. Quarterly report pursuant to Section 13 or 15(d)

Related Parties - Schedule of Related Party Transactions (Details) - Affiliated Entity - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Purchaser of Subsidiary
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	$ 0	$ 0
Accounts Receivable (Payable)	725		$ 756
Disposed Entity
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	0	0
Accounts Receivable (Payable)	462		846
Land Development Project
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	0	0
Accounts Receivable (Payable)	774		774
Subcontracting Services
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	(1,578)	(3,293)
Accounts Receivable (Payable)	(316)		(1,238)
Construction Services
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	1,280	113
Accounts Receivable (Payable)	1,643		2,434
Island Pond
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	(80)	(80)
Accounts Receivable (Payable)	0		0
Vehicles
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	(253)	(289)
Accounts Receivable (Payable)	0		0
Consulting Services
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	(71)	(67)
Accounts Receivable (Payable)	0		0
H&K
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	0	(21)
Accounts Receivable (Payable)	0		0
SunTx
Related Party Transaction [Line Items]
Revenue Earned (Expense Incurred)	(314)	$ (254)
Accounts Receivable (Payable)	$ 0		$ 0