Significant Accounting Policies - Comprehensive Earnings Attributable to Martin Marietta Materials Incorporated (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net earnings attributable to Martin Marietta Materials, Inc.	$ 189,475	$ 185,377	$ 232,328	$ 195,400
Other comprehensive earnings, net of tax	2,990	1,602	6,245	3,221
Earnings attributable to Martin Marietta Materials, Inc.	$ 192,465	$ 186,979	$ 238,573	$ 198,621