Business Segments - Financial Data for Continuing Operations for Company's Reportable Business Segments (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total revenues	$ 1,557.3	$ 1,321.4	$ 3,917.6	$ 3,550.3
Earnings (Loss) from operations	356.9	400.6	763.7	764.8
Assets employed	13,786.2		13,786.2		$ 10,580.8
Products and Services
Segment Reporting Information [Line Items]
Total revenues	1,462.7	1,240.7	3,679.9	3,321.2
Building Materials Business
Segment Reporting Information [Line Items]
Total revenues	1,478.9	1,260.5	3,692.6	3,370.1
Earnings (Loss) from operations	356.4	393.7	749.5	754.3
Assets employed	10,689.3		10,689.3		9,698.0
Building Materials Business | Products and Services
Segment Reporting Information [Line Items]
Total revenues	1,390.8	1,185.5	3,472.8	3,157.2
Operating Segments | Building Materials Business East Group
Segment Reporting Information [Line Items]
Total revenues	684.1	549.3	1,714.4	1,465.9
Earnings (Loss) from operations	205.8	181.4	465.3	386.1
Assets employed	5,075.9		5,075.9		4,342.5
Operating Segments | Building Materials Business East Group | Products and Services
Segment Reporting Information [Line Items]
Total revenues	641.8	514.1	1,610.9	1,371.8
Operating Segments | Building Materials Business West Group
Segment Reporting Information [Line Items]
Total revenues	794.8	711.2	1,978.2	1,904.2
Earnings (Loss) from operations	150.6	212.3	284.2	368.2
Assets employed	5,613.4		5,613.4		5,355.5
Operating Segments | Building Materials Business West Group | Products and Services
Segment Reporting Information [Line Items]
Total revenues	749.0	671.4	1,861.9	1,785.4
Operating Segments | Magnesia Specialties
Segment Reporting Information [Line Items]
Total revenues	78.4	60.9	225.0	180.2
Earnings (Loss) from operations	23.1	16.4	69.8	51.2
Assets employed	169.6		169.6		167.9
Operating Segments | Magnesia Specialties | Products and Services
Segment Reporting Information [Line Items]
Total revenues	71.9	55.2	207.1	164.0
Operating Segments | Building Materials Business
Segment Reporting Information [Line Items]
Total revenues	1,478.9	1,260.5	3,692.6	3,370.1
Corporate
Segment Reporting Information [Line Items]
Earnings (Loss) from operations	(22.6)	$ (9.5)	(55.6)	$ (40.7)
Assets employed	$ 2,927.3		$ 2,927.3		$ 714.9