Summary of Significant Accounting Policies - Insurance Coverage (Details) $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($) item policy	Dec. 31, 2022 USD ($)
Insurance Coverage
Accrued insurance claims receivables	$ 4.3	$ 5.8
Marine Segment
Insurance Coverage
Levels of insurance coverage maintained by the Company | item	5
Amount in excess of primary insurance coverage	$ 200.0
Marine Segment | Other liability policies
Insurance Coverage
Primary limit of insurance coverage	1.0
Marine Segment | Maritime employer's liability
Insurance Coverage
Primary limit of insurance coverage	10.0
Marine Segment | Watercraft pollution policy
Insurance Coverage
Primary limit of insurance coverage	$ 5.0
Concrete Segment
Insurance Coverage
Levels of insurance coverage maintained by the Company | item	5
Amount in excess of primary insurance coverage	$ 200.0
Number of employee health care insurance policies | policy	2
Concrete Segment | Other liability policies
Insurance Coverage
Primary limit of insurance coverage	$ 1.0