Basic and Diluted Earnings Per Common Share (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net earnings attributable to Martin Marietta Materials, Inc.	$ 142,279	$ 122,052	$ 184,613	$ 167,047
Less: Distributed and undistributed earnings attributable to unvested awards	413	519	553	730
Basic and diluted net earnings available to common shareholders attributable to Martin Marietta Materials, Inc.	$ 141,866	$ 121,533	$ 184,060	$ 166,317
Basic weighted-average common shares outstanding	62,858	63,532	62,961	63,845
Effect of dilutive employee and director awards	283	270	285	246
Diluted weighted-average common shares outstanding	63,141	63,802	63,246	64,091