Consolidated Statements of Comprehensive Earnings - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Consolidated Net Earnings	$ 702.8	$ 721.1	$ 612.0
Defined benefit pension and postretirement plans:
Net gain (loss) arising during period, net of tax of $16.8, $(8.7) and $(4.8), respectively	51.3	(26.6)	(14.5)
Amortization of prior service credit, net of tax of $0.0, $0.0 and $(0.2), respectively		(0.1)	(0.6)
Amortization of actuarial loss, net of tax of $2.9, $3.6 and $3.8, respectively	9.2	10.7	11.7
Amount recognized in net periodic pension cost due to settlement, net of tax of $0.0, $0.9 and $0.0, respectively		2.8
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	60.5	(13.2)	(3.4)
Foreign currency translation gain	0.3	0.6	1.2
Other Comprehensive Income (Loss), Net of Tax	60.8	(12.6)	(2.2)
Consolidated comprehensive earnings	763.6	708.5	609.8
Less: Comprehensive earnings attributable to noncontrolling interests	0.3	0.1	0.1
Comprehensive Earnings Attributable to Martin Marietta	$ 763.3	$ 708.4	$ 609.7