Significant Accounting Policies - Comprehensive Earnings (Loss) Attributable to Martin Marietta Materials Incorporated (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net earnings attributable to Martin Marietta	$ 295.3	$ 254.6	$ 683.2	$ 545.7
Other comprehensive earnings (loss), net of tax	3.0	1.6	(27.5)	7.0
Consolidated comprehensive earnings attributable to Martin Marietta	$ 298.3	$ 256.2	$ 655.7	$ 552.7