Revenue Recognition - Schedule of Company's Total Revenues by Category for each Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue Recognition [Line Items]
Total	$ 1,557.3	$ 1,321.4	$ 3,917.6	$ 3,550.3
Building Materials Business
Revenue Recognition [Line Items]
Total	1,478.9	1,260.5	3,692.6	3,370.1
Products and Services
Revenue Recognition [Line Items]
Total	1,462.7	1,240.7	3,679.9	3,321.2
Products and Services | Building Materials Business
Revenue Recognition [Line Items]
Total	1,390.8	1,185.5	3,472.8	3,157.2
Freight
Revenue Recognition [Line Items]
Total	94.6	80.7	237.7	229.1
Freight | Building Materials Business
Revenue Recognition [Line Items]
Total	88.1	75.0	219.8	212.9
Operating Segments | Building Materials Business East Group
Revenue Recognition [Line Items]
Total	684.1	549.3	1,714.4	1,465.9
Operating Segments | Building Materials Business West Group
Revenue Recognition [Line Items]
Total	794.8	711.2	1,978.2	1,904.2
Operating Segments | Building Materials Business
Revenue Recognition [Line Items]
Total	1,478.9	1,260.5	3,692.6	3,370.1
Operating Segments | Magnesia Specialties
Revenue Recognition [Line Items]
Total	78.4	60.9	225.0	180.2
Operating Segments | Products and Services | Building Materials Business East Group
Revenue Recognition [Line Items]
Total	641.8	514.1	1,610.9	1,371.8
Operating Segments | Products and Services | Building Materials Business West Group
Revenue Recognition [Line Items]
Total	749.0	671.4	1,861.9	1,785.4
Operating Segments | Products and Services | Magnesia Specialties
Revenue Recognition [Line Items]
Total	71.9	55.2	207.1	164.0
Operating Segments | Freight | Building Materials Business East Group
Revenue Recognition [Line Items]
Total	42.3	35.2	103.5	94.1
Operating Segments | Freight | Building Materials Business West Group
Revenue Recognition [Line Items]
Total	45.8	39.8	116.3	118.8
Operating Segments | Freight | Building Materials Business
Revenue Recognition [Line Items]
Total	88.1	75.0	219.8	212.9
Operating Segments | Freight | Magnesia Specialties
Revenue Recognition [Line Items]
Total	$ 6.5	$ 5.7	$ 17.9	$ 16.2