Retirement Plans, Postretirement and Postemployment Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation for defined benefit pension plans	$ 974.0	$ 878.7
Combined pension plan and SERP contributions	88.4	58.9
Estimated contribution of pension plans	82.6
Corporation's matching obligations	$ 17.9	$ 17.6	$ 16.5
Defined contribution plan name	401(a)
Defined Contribution Plan, Plan Name [Extensible List]	mlm:A401DefinedContributionPlanMember
Postretirement Health Care Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated contribution of pension plans				$ 1.3
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Percentage of pension asset equity securities in mid and large capitalization funds	45.00%