Basic and Diluted Earnings Per Common Share (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule of Earnings Per Share, Basic and Diluted, by Common Class
Net earnings from continuing operations attributable to Martin Marietta	$ 53,812	$ 72,107	$ 91,786	$ 85,758
Less: Distributed and undistributed earnings attributable to unvested awards	213	265	372	374
Basic and diluted net earnings available to common shareholders from continuing operations attributable to Martin Marietta	53,599	71,842	91,414	85,384
Basic and diluted net loss available to common shareholders from discontinued operations	(69)	(271)	(140)	(454)
Basic and diluted net earnings available to common shareholders attributable to Martin Marietta	$ 53,530	$ 71,571	$ 91,274	$ 84,930
Basic weighted-average common shares outstanding	67,086	46,244	53,342	46,134
Effect of dilutive employee and director awards	409	105	217	127
Diluted weighted-average common shares outstanding	67,495	46,349	53,559	46,261