Revenue Recognition - Schedule of Company's Total Revenues by Category for each Reportable Segment (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Oct. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Revenue Recognition [Line Items]
Total	$ 250.0	$ 1,230.8	$ 982.4
Building Materials Business
Revenue Recognition [Line Items]
Total		1,153.8	911.5
Products and Services
Revenue Recognition [Line Items]
Total		1,147.8	921.9
Products and Services | Building Materials Business
Revenue Recognition [Line Items]
Total		1,077.0	856.6
Freight
Revenue Recognition [Line Items]
Total		83.0	60.5
Freight | Building Materials Business
Revenue Recognition [Line Items]
Total		76.8	54.9
Operating Segments | Building Materials Business East Group
Revenue Recognition [Line Items]
Total		418.8	394.9
Operating Segments | Building Materials Business West Group
Revenue Recognition [Line Items]
Total		735.0	516.6
Operating Segments | Building Materials Business
Revenue Recognition [Line Items]
Total		1,153.8	911.5
Operating Segments | Magnesia Specialties
Revenue Recognition [Line Items]
Total		77.0	70.9
Operating Segments | Products and Services | Building Materials Business East Group
Revenue Recognition [Line Items]
Total		394.6	372.5
Operating Segments | Products and Services | Building Materials Business West Group
Revenue Recognition [Line Items]
Total		682.4	484.1
Operating Segments | Products and Services | Magnesia Specialties
Revenue Recognition [Line Items]
Total		70.8	65.3
Operating Segments | Freight | Building Materials Business East Group
Revenue Recognition [Line Items]
Total		24.2	22.4
Operating Segments | Freight | Building Materials Business West Group
Revenue Recognition [Line Items]
Total		52.6	32.5
Operating Segments | Freight | Building Materials Business
Revenue Recognition [Line Items]
Total		76.8	54.9
Operating Segments | Freight | Magnesia Specialties
Revenue Recognition [Line Items]
Total		$ 6.2	$ 5.6