Revenue Recognition - Schedule of Company's Total Revenues by Category for each Reportable Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue Recognition [Line Items]
Total	$ 4,739.1	$ 4,244.3	$ 3,965.6
Building Materials Business
Revenue Recognition [Line Items]
Total	4,467.8	3,956.6	3,695.6
Products and Services
Revenue Recognition [Line Items]
Total	4,422.3	3,980.4	3,723.5
Products and Services | Building Materials Business
Revenue Recognition [Line Items]
Total	4,172.4	3,711.8	3,470.8
Freight
Revenue Recognition [Line Items]
Total	316.8	263.9	242.1
Freight | Building Materials Business
Revenue Recognition [Line Items]
Total	295.4	244.8	224.8
Operating Segments | Building Materials Business
Revenue Recognition [Line Items]
Total	4,467.8	3,956.6	3,695.6
Operating Segments | Building Materials Business Mid-America Group
Revenue Recognition [Line Items]
Total	1,446.0	1,223.2	1,053.3
Operating Segments | Building Materials Business Southeast Group
Revenue Recognition [Line Items]
Total	506.4	423.4	362.6
Operating Segments | Building Materials Business West Group
Revenue Recognition [Line Items]
Total	2,515.4	2,310.0	2,279.7
Operating Segments | Magnesia Specialties
Revenue Recognition [Line Items]
Total	271.3	287.7	270.0
Operating Segments | Products and Services | Building Materials Business Mid-America Group
Revenue Recognition [Line Items]
Total	1,328.8	1,133.8	982.2
Operating Segments | Products and Services | Building Materials Business Southeast Group
Revenue Recognition [Line Items]
Total	489.1	409.6	348.7
Operating Segments | Products and Services | Building Materials Business West Group
Revenue Recognition [Line Items]
Total	2,354.5	2,168.4	2,139.9
Operating Segments | Products and Services | Magnesia Specialties
Revenue Recognition [Line Items]
Total	249.9	268.6	252.7
Operating Segments | Freight | Building Materials Business
Revenue Recognition [Line Items]
Total	295.4	244.8	224.8
Operating Segments | Freight | Building Materials Business Mid-America Group
Revenue Recognition [Line Items]
Total	117.2	89.4	71.1
Operating Segments | Freight | Building Materials Business Southeast Group
Revenue Recognition [Line Items]
Total	17.3	13.8	13.9
Operating Segments | Freight | Building Materials Business West Group
Revenue Recognition [Line Items]
Total	160.9	141.6	139.8
Operating Segments | Freight | Magnesia Specialties
Revenue Recognition [Line Items]
Total	$ 21.4	$ 19.1	$ 17.3