Significant Accounting Policies (Basic And Diluted Earnings Per Common Share) (Details) (USD $) Share data in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Significant Accounting Policies
Net earnings from continuing operations attributable to Martin Marietta Materials, Inc.	$ 48,909,000	$ 51,968,000	$ 67,350,000	$ 82,074,000
Less: Distributed and undistributed earnings attributable to unvested awards	378,000	529,000	557,000	865,000
Basic and diluted net earnings available to common shareholders from continuing operations attributable to Martin Marietta Materials, Inc.	48,531,000	51,439,000	66,793,000	81,209,000
Basic and diluted net earnings available to common shareholders from discontinued operations	247,000	22,000	191,000	135,000
Basic and diluted net earnings available to common shareholders attributable to Martin Marietta Materials, Inc.	48,778,000	51,461,000	66,984,000	81,344,000
Basic weighted-average common shares outstanding	45,690	45,526	45,634	45,463
Effect of dilutive employee and director awards	109	152	149	176
Diluted weighted-average common shares outstanding	45,799	45,678	45,783	45,639
Consolidated comprehensive earnings	$ 50,091,000	$ 55,495,000	$ 72,592,000	$ 91,293,000