Comprehensive Earnings Attributable to Martin Marietta Materials Incorporated (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net earnings attributable to Martin Marietta Materials, Inc.	$ 117,544	$ 53,743	$ 205,607	$ 91,646
Other comprehensive earnings (loss), net of tax	72	(1,140)	(6,583)	833
Earnings attributable to Martin Marietta Materials, Inc.	$ 117,616	$ 52,603	$ 199,024	$ 92,479