Construction Partners, Inc. Annual report pursuant to Section 13 and 15(d)

Related Parties - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
	Jun. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Sep. 30, 2019	Dec. 31, 2017
SunTx Capital Partners \| Affiliated Entity
Related Party Transaction [Line Items]
Payment to related party			$ 250
H&K \| Affiliated Entity
Related Party Transaction [Line Items]
Payment to related party	$ 15
Consideration Note Receivable
Related Party Transaction [Line Items]
Note receivable as consideration for sale of the wholly-owned subsidiary					$ 1,000
Accounts Payable Note Receivable
Related Party Transaction [Line Items]
Note receivable as consideration for sale of the wholly-owned subsidiary					$ 1,000
H&A \| Affiliated Entity
Related Party Transaction [Line Items]
Purchases from related party		$ 500
Other Current Assets \| Consideration Note Receivable
Related Party Transaction [Line Items]
Note receivable as consideration for sale of the wholly-owned subsidiary				$ 100
Other Current Assets \| Accounts Payable Note Receivable
Related Party Transaction [Line Items]
Note receivable as consideration for sale of the wholly-owned subsidiary				100
Other Noncurrent Assets \| Consideration Note Receivable
Related Party Transaction [Line Items]
Note receivable as consideration for sale of the wholly-owned subsidiary				700
Other Noncurrent Assets \| Accounts Payable Note Receivable
Related Party Transaction [Line Items]
Note receivable as consideration for sale of the wholly-owned subsidiary				$ 700