Accounting Policies - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2021 USD ($)	Jun. 30, 2020 Executive	Dec. 31, 2020 USD ($) Facility State Plant Division	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Significant Accounting Policies [Line Items]
Number of quarries and yards | Facility			300
Number of states with aggregates business sales by destination | State			27
Number of cement plants | Plant			2
Number of asphalt plants | Plant			8
Number of senior executives retirement | Executive		2
Number of building material divisions | Division			4
Out of period expenses				$ 15.7
Restricted cash			$ 97.1
Number of days restricted from utilizing cash			180 days
Retirement plans and postretirement benefits amortized amount representing percentage of greater of projected benefit obligation or pension plan assets.			10.00%
Minimum likelihood for recognition of tax benefit related to uncertain tax position			50.00%
Operating lease, right of use asset			$ 453.0	481.9
Operating lease, liability			459.0	486.6
Finance lease, right of use asset			37.8	18.3
Finance lease, liability			$ 24.5	$ 8.7
ASU 2016-13
Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adoption date			Jan. 01, 2020
Change in accounting principle, accounting standards update, adopted [true false]			true
Change in accounting principle, accounting standards update, immaterial effect [true false]			true
ASU 2018-14
Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted [true false]			true
Change in accounting principle, accounting standards update, immaterial effect [true false]			false
Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adoption date			Jan. 01, 2019
Change in accounting principle, accounting standards update, adopted [true false]			true
Change in accounting principle, accounting standards update, immaterial effect [true false]			true
Operating lease, right of use asset					$ 502.5
Operating lease, liability					501.6
Finance lease, right of use asset					10.9
Finance lease, liability					$ 12.1
Expendable Parts Inventory
Significant Accounting Policies [Line Items]
Allowance for inventories in excess of sales requisite record period			5 years
Supplies Inventory
Significant Accounting Policies [Line Items]
Allowance for inventories in excess of sales requisite record period			1 year
Subsequent Event
Significant Accounting Policies [Line Items]
Cash transferred from restricted to unrestricted	$ 47.2
Percentage of Aggregates Business Net Sales in Top Five Sales states | Geographic Concentration Risk | Sales Revenue Segment
Significant Accounting Policies [Line Items]
Total net sales, percentage			71.00%
Minimum
Significant Accounting Policies [Line Items]
Number of ready mixed concrete plants | Plant			120
Minimum | Inventory Finished Goods
Significant Accounting Policies [Line Items]
Allowance for inventories in excess of sales requisite record period			12 months
Maximum | Inventory Finished Goods
Significant Accounting Policies [Line Items]
Allowance for inventories in excess of sales requisite record period			5 years