Basic and Diluted Earnings Per Common Share (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net earnings attributable to Martin Marietta Materials, Inc.	$ 10,023	$ 42,334
Less: Distributed and undistributed earnings attributable to unvested awards	63	153
Basic and diluted net earnings available to common shareholders attributable to Martin Marietta Materials, Inc.	$ 9,960	$ 42,181
Basic weighted-average common shares outstanding	62,957	63,024
Effect of dilutive employee and director awards	265	295
Diluted weighted-average common shares outstanding	63,222	63,319