Basic and Diluted Earnings Per Common Share (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net earnings attributable to Martin Marietta Materials, Inc.	$ 151,546	$ 159,479	$ 336,159	$ 326,526
Less: Distributed and undistributed earnings attributable to unvested awards	399	637	1,000	1,388
Basic and diluted net earnings available to common shareholders attributable to Martin Marietta Materials, Inc.	$ 151,147	$ 158,842	$ 335,159	$ 325,138
Basic weighted-average common shares outstanding	62,896	63,452	62,940	63,713
Effect of dilutive employee and director awards	262	271	278	254
Diluted weighted-average common shares outstanding	63,158	63,723	63,218	63,967