Revenues and Gross Profit - Total Revenues and Gross Profit (Loss) by Product Line (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Oct. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Product Information [Line Items]
Total revenues	$ 250.0	$ 1,230.8	$ 982.4
Gross profit (loss)		156.1	174.7
Interproduct Revenues
Product Information [Line Items]
Total revenues		(88.1)	(73.1)
Corporate
Product Information [Line Items]
Gross profit (loss)		(7.9)	(0.8)
Building Materials Business
Product Information [Line Items]
Total revenues		1,153.8	911.5
Building Materials Business | Operating Segments
Product Information [Line Items]
Total revenues		1,153.8	911.5
Gross profit (loss)		138.4	148.0
Building Materials Business | Operating Segments | Products and Services
Product Information [Line Items]
Total revenues		1,077.0	856.6
Gross profit (loss)		137.0	148.3
Magnesia Specialties | Operating Segments
Product Information [Line Items]
Total revenues		77.0	70.9
Gross profit (loss)		25.6	27.5
Magnesia Specialties | Operating Segments | Products and Services
Product Information [Line Items]
Total revenues		70.8	65.3
Gross profit (loss)		26.8	28.4
Aggregates | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues		685.9	572.6
Gross profit (loss)		101.9	121.8
Cement | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues		134.3	109.6
Gross profit (loss)		27.3	15.3
Ready Mixed Concrete | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues		290.1	235.3
Gross profit (loss)		21.1	19.4
Asphalt and Paving | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues		54.8	12.2
Gross profit (loss)		(13.3)	(8.2)
Freight
Product Information [Line Items]
Total revenues		83.0	60.5
Freight | Building Materials Business
Product Information [Line Items]
Total revenues		76.8	54.9
Freight | Building Materials Business | Operating Segments
Product Information [Line Items]
Total revenues		76.8	54.9
Gross profit (loss)		1.4	(0.3)
Freight | Magnesia Specialties | Operating Segments
Product Information [Line Items]
Total revenues		6.2	5.6
Gross profit (loss)		$ (1.2)	$ (0.9)