Revenues and Gross Profit - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
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. 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	$ 250.5	$ 239.2	$ 153.9
Service revenues	6,777.2	6,160.7	5,414.0
Revenue recognized from contract liabilities	10.3	7.7
Retainage on contracts	16.6	13.4
Service | CALIFORNIA and COLORADO | West Group
Revenue Recognition [Line Items]
Service revenues	$ 410.7	$ 353.7	$ 259.1
Minimum | Service
Revenue Recognition [Line Items]
Performance obligations, period	1 day
Maximum | Service
Revenue Recognition [Line Items]
Performance obligations, period	2 years