Basic and Diluted Earnings Loss Per Common Share (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Schedule of Earnings Per Share, Basic and Diluted, by Common Class
Net earnings from continuing operations attributable to Martin Marietta Materials, Inc.	$ 36,435	$ 36,751	$ 296	$ 20,793
Less: Distributed and undistributed earnings attributable to unvested awards	232	298	242	313
Basic and diluted net earnings available to common shareholders from continuing operations attributable to Martin Marietta Materials, Inc.	36,203	36,453	54	20,480
Basic and diluted net earnings (loss) available to common shareholders from discontinued operations	316	(952)	(278)	(2,408)
Basic and diluted net earnings (loss) available to common shareholders attributable to Martin Marietta Materials, Inc.	$ 36,519	$ 35,501	$ (224)	$ 18,072
Basic weighted-average common shares outstanding	45,781	45,628	45,757	45,606
Effect of dilutive employee and director awards	124	166		168
Diluted weighted-average common shares outstanding	45,905	45,794	45,757	45,774