Revenues and Gross Profit - Total Revenues and Gross Profit by Product Line (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Product Information [Line Items]
Total revenues	$ 4,729.9	$ 4,739.1	$ 4,244.3
Gross profit (loss)	1,252.8	1,179.0	966.6
Interproduct Revenues
Product Information [Line Items]
Total revenues	(294.4)	(265.5)	(264.2)
Corporate
Product Information [Line Items]
Gross profit (loss)	7.5	3.0	7.6
Building Materials Business
Product Information [Line Items]
Total revenues	4,487.2	4,467.8	3,956.6
Gross profit (loss)	1,159.8	1,080.6	860.3
Building Materials Business | Operating Segments
Product Information [Line Items]
Total revenues	4,487.2	4,467.8	3,956.6
Gross profit (loss)	1,159.8	1,080.6	860.3
Building Materials Business | Operating Segments | Products and Services
Product Information [Line Items]
Total revenues	4,211.2	4,172.4	3,711.8
Gross profit (loss)	1,159.4	1,080.8	860.1
Magnesia Specialties | Operating Segments
Product Information [Line Items]
Total revenues	242.7	271.3	287.7
Gross profit (loss)	85.5	95.4	98.7
Magnesia Specialties | Operating Segments | Products and Services
Product Information [Line Items]
Total revenues	220.9	249.9	268.6
Gross profit (loss)	89.6	99.4	102.9
Aggregates | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues	2,769.3	2,756.7	2,365.8
Gross profit (loss)	848.5	807.9	608.4
Cement | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues	452.5	439.1	387.8
Gross profit (loss)	170.9	143.4	126.2
Ready Mixed Concrete | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues	952.1	948.1	963.8
Gross profit (loss)	79.6	78.8	74.2
Asphalt and Paving | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues	331.7	294.0	258.6
Gross profit (loss)	60.4	50.7	51.3
Freight
Product Information [Line Items]
Total revenues	297.8	316.8	263.9
Freight | Building Materials Business
Product Information [Line Items]
Total revenues	276.0	295.4	244.8
Freight | Building Materials Business | Operating Segments
Product Information [Line Items]
Total revenues	276.0	295.4	244.8
Gross profit (loss)	0.4	(0.2)	0.2
Freight | Magnesia Specialties | Operating Segments
Product Information [Line Items]
Total revenues	21.8	21.4	19.1
Gross profit (loss)	$ (4.1)	$ (4.0)	$ (4.2)