Business Segments - Financial Data for Continuing Operations for Company's Reportable Business Segments (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 1,270.6	$ 1,279.5	$ 2,228.9	$ 2,218.4
Earnings (Loss) from operations	306.4	285.9	364.2	355.1
Products and Services
Segment Reporting Information [Line Items]
Total revenues	1,189.5	1,196.1	2,080.5	2,074.4
Building Materials Business
Segment Reporting Information [Line Items]
Total revenues	1,217.0	1,203.2	2,109.6	2,068.1
Earnings (Loss) from operations	303.1	284.6	360.6	356.6
Building Materials Business | Products and Services
Segment Reporting Information [Line Items]
Total revenues	1,140.6	1,125.7	1,971.7	1,934.9
Operating Segments | Building Materials Business Mid-America Group
Segment Reporting Information [Line Items]
Total revenues	392.3	414.5	653.1	662.6
Earnings (Loss) from operations	136.2	141.3	157.0	171.9
Operating Segments | Building Materials Business Mid-America Group | Products and Services
Segment Reporting Information [Line Items]
Total revenues	362.9	381.9	603.9	611.5
Operating Segments | Building Materials Business Southeast Group
Segment Reporting Information [Line Items]
Total revenues	142.2	137.0	263.4	256.3
Earnings (Loss) from operations	33.7	32.7	47.7	53.8
Operating Segments | Building Materials Business Southeast Group | Products and Services
Segment Reporting Information [Line Items]
Total revenues	136.8	132.0	253.7	247.4
Operating Segments | Building Materials Business West Group
Segment Reporting Information [Line Items]
Total revenues	682.5	651.7	1,193.1	1,149.2
Earnings (Loss) from operations	133.2	110.6	155.9	130.9
Operating Segments | Building Materials Business West Group | Products and Services
Segment Reporting Information [Line Items]
Total revenues	640.9	611.8	1,114.1	1,076.0
Operating Segments | Magnesia Specialties
Segment Reporting Information [Line Items]
Total revenues	53.6	76.3	119.3	150.3
Earnings (Loss) from operations	13.2	25.2	34.9	47.9
Operating Segments | Magnesia Specialties | Products and Services
Segment Reporting Information [Line Items]
Total revenues	48.9	70.4	108.8	139.5
Operating Segments | Building Materials Business
Segment Reporting Information [Line Items]
Total revenues	1,217.0	1,203.2	2,109.6	2,068.1
Corporate
Segment Reporting Information [Line Items]
Earnings (Loss) from operations	$ (9.9)	$ (23.9)	$ (31.3)	$ (49.4)