Revenues and Gross Profit - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Revenue Recognition [Line Items]
Performance obligations, description of timing			Performance obligations within paving service agreements are satisfied over time, primarily ranging from one day to two years. For product and freight revenues, customer payment terms are generally 30 days from invoice date. Customer payments for the paving operations are based on a contractual billing schedule and are due 30 days from invoice date.
Product and freight revenues customer payment terms			30 days
Customer payments terms based on contractual billing			30 days
Future revenues from unsatisfied performance obligations	$ 268.0	$ 304.3	$ 268.0	$ 304.3
Service revenues	1,994.1	1,811.7	5,169.0	4,684.2
Revenue recognized from contract liabilities	5.4	4.1	9.8	7.4
Retainage on contracts	15.7		15.7		$ 13.4
Service | CALIFORNIA and COLORADO | West Group
Revenue Recognition [Line Items]
Service revenues	$ 172.9	$ 138.7	$ 307.2	$ 252.1
Minimum | Service
Revenue Recognition [Line Items]
Performance obligations, period			1 day
Maximum | Service
Revenue Recognition [Line Items]
Performance obligations, period			2 years