Revenues and Gross Profit - Total Revenues and Gross Profit by Product Line (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Product Information [Line Items]
Total revenues	$ 1,557.3	$ 1,321.4	$ 3,917.6	$ 3,550.3
Gross profit (loss)	441.9	404.5	1,001.7	927.4
Interproduct Revenues
Product Information [Line Items]
Total revenues	(115.3)	(81.4)	(285.1)	(210.9)
Corporate
Product Information [Line Items]
Gross profit (loss)	0.5	0.7	0.3	4.3
Building Materials Business
Product Information [Line Items]
Total revenues	1,478.9	1,260.5	3,692.6	3,370.1
Building Materials Business | Operating Segments
Product Information [Line Items]
Total revenues	1,478.9	1,260.5	3,692.6	3,370.1
Gross profit (loss)	414.4	383.8	920.0	861.0
Building Materials Business | Operating Segments | Products and Services
Product Information [Line Items]
Total revenues	1,390.8	1,185.5	3,472.8	3,157.2
Gross profit (loss)	413.1	382.9	918.3	860.7
Magnesia Specialties | Operating Segments
Product Information [Line Items]
Total revenues	78.4	60.9	225.0	180.2
Gross profit (loss)	27.0	20.0	81.4	62.1
Magnesia Specialties | Operating Segments | Products and Services
Product Information [Line Items]
Total revenues	71.9	55.2	207.1	164.0
Gross profit (loss)	28.1	21.0	84.4	65.3
Aggregates | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues	857.1	766.9	2,231.5	2,092.1
Gross profit (loss)	292.9	279.1	687.7	640.4
Cement | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues	132.3	115.6	358.4	331.7
Gross profit (loss)	49.9	46.5	101.3	117.2
Ready Mixed Concrete | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues	320.8	254.6	824.5	689.4
Gross profit (loss)	31.4	24.7	69.9	56.7
Asphalt and Paving | Building Materials Business | Operating Segments | Reportable Subsegments | Products and Services
Product Information [Line Items]
Total revenues	195.9	129.8	343.5	254.9
Gross profit (loss)	38.9	32.6	59.4	46.4
Freight
Product Information [Line Items]
Total revenues	94.6	80.7	237.7	229.1
Freight | Building Materials Business
Product Information [Line Items]
Total revenues	88.1	75.0	219.8	212.9
Freight | Building Materials Business | Operating Segments
Product Information [Line Items]
Total revenues	88.1	75.0	219.8	212.9
Gross profit (loss)	1.3	0.9	1.7	0.3
Freight | Magnesia Specialties | Operating Segments
Product Information [Line Items]
Total revenues	6.5	5.7	17.9	16.2
Gross profit (loss)	$ (1.1)	$ (1.0)	$ (3.0)	$ (3.2)