Significant Accounting Policies - Comprehensive (Loss) Earnings Attributable to Martin Marietta Materials Incorporated (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement of Comprehensive Income [Abstract]
Net earnings attributable to Martin Marietta	$ 366.5	$ 225.8	$ 387.9	$ 291.1
Other comprehensive (loss) earnings, net of tax	1.2	2.6	(30.5)	5.4
Earnings attributable to Martin Marietta Materials, Inc.	$ 367.7	$ 228.4	$ 357.4	$ 296.5