Significant Accounting Policies (Basic And Diluted Earnings (Loss) Per Common Share) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Significant Accounting Policies [Abstract]
Net loss from continuing operations attributable to Martin Marietta Materials, Inc.	$ (36,140)	$ (15,958)
Less: Distributed and undistributed earnings attributable to unvested awards	(126)	(165)
Basic and diluted net loss available to common shareholders from continuing operations attributable to Martin Marietta Materials, Inc.	(36,266)	(16,123)
Basic and diluted net loss available to common shareholders from discontinued operations	(592)	(1,456)
Basic and diluted net loss available to common shareholders attributable to Martin Marietta Materials, Inc.	$ (36,858)	$ (17,579)
Basic weighted-average common shares outstanding	45,734	45,584
Effect of dilutive employee and director awards
Diluted weighted-average common shares outstanding	45,734	45,584