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

Equity-Based Compensation (Detail)

v3.20.2

Equity-Based Compensation (Detail)	1 Months Ended		12 Months Ended
Equity-Based Compensation (Detail)	Sep. 30, 2019 USD ($)	Aug. 31, 2019 $ / shares shares	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($) shares
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate grant date fair value	$ 3,800,000			$ 3,800,000
Compensation expense			$ 1,600,000	500,000
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense			0	$ 400,000
Conversion ratio		0.367
Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 700,000
Exercises in period, weighted average (in dollars per share) \| $ / shares		$ 0.0357
Class A Common Stock \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares) \| shares				292,534
Unrecognized compensation expense			$ 1,700,000
Class B Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares) \| shares		74,592

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