Business Segments - Financial Data for Continuing Operations for Company's Reportable Business Segments (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 958.2	$ 939.0
Earnings (Loss) from operations	57.8	69.2
Products and Services
Segment Reporting Information [Line Items]
Total revenues	891.0	878.3
Building Materials Business
Segment Reporting Information [Line Items]
Total revenues	892.5	864.9
Earnings (Loss) from operations	57.5	72.0
Building Materials Business | Products and Services
Segment Reporting Information [Line Items]
Total revenues	831.1	809.1
Operating Segments | Building Materials Business Mid-America Group
Segment Reporting Information [Line Items]
Total revenues	260.8	248.1
Earnings (Loss) from operations	20.8	30.6
Operating Segments | Building Materials Business Mid-America Group | Products and Services
Segment Reporting Information [Line Items]
Total revenues	241.0	229.6
Operating Segments | Building Materials Business Southeast Group
Segment Reporting Information [Line Items]
Total revenues	121.1	119.2
Earnings (Loss) from operations	14.0	21.1
Operating Segments | Building Materials Business Southeast Group | Products and Services
Segment Reporting Information [Line Items]
Total revenues	116.9	115.3
Operating Segments | Building Materials Business West Group
Segment Reporting Information [Line Items]
Total revenues	510.6	497.6
Earnings (Loss) from operations	22.7	20.3
Operating Segments | Building Materials Business West Group | Products and Services
Segment Reporting Information [Line Items]
Total revenues	473.2	464.2
Operating Segments | Magnesia Specialties
Segment Reporting Information [Line Items]
Total revenues	65.7	74.1
Earnings (Loss) from operations	21.7	22.6
Operating Segments | Magnesia Specialties | Products and Services
Segment Reporting Information [Line Items]
Total revenues	59.9	69.2
Operating Segments | Building Materials Business
Segment Reporting Information [Line Items]
Total revenues	892.5	864.9
Corporate
Segment Reporting Information [Line Items]
Earnings (Loss) from operations	$ (21.4)	$ (25.4)