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

Related Parties - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Sep. 30, 2018	Mar. 31, 2019	Dec. 31, 2017
SunTx Capital Partners \| Affiliated Entity
Related Party Transaction [Line Items]
Payment to related party		$ 250
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 Assets \| Consideration Note Receivable
Related Party Transaction [Line Items]
Note receivable as consideration for sale of the wholly-owned subsidiary		700
Other Assets \| Accounts Payable Note Receivable
Related Party Transaction [Line Items]
Note receivable as consideration for sale of the wholly-owned subsidiary		$ 800