Summary of Significant Accounting Policies - Insurance Coverage (Details) $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($) item	Dec. 31, 2023 USD ($)
Insurance Coverage
Accrued insurance claims liability	$ 5.2	$ 7.5
Marine
Insurance Coverage
Levels of insurance coverage maintained by the Company | item	5
Amount in excess of primary insurance coverage	$ 300.0
Marine | Other liability policies
Insurance Coverage
Primary limit of insurance coverage	1.0
Marine | Maritime employer's liability
Insurance Coverage
Primary limit of insurance coverage	10.0
Marine | Watercraft pollution policy
Insurance Coverage
Primary limit of insurance coverage	$ 5.0
Concrete
Insurance Coverage
Levels of insurance coverage maintained by the Company | item	5
Amount in excess of primary insurance coverage	$ 300.0
Number of employee health care insurance policies | item	2
Concrete | Other liability policies
Insurance Coverage
Primary limit of insurance coverage	$ 1.0