Business Combination - Business Acquisition, Pro Forma Information (Details) - Bluegrass Materials Company - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Total revenues	$ 1,219,640	$ 1,148,787	$ 3,279,455	$ 3,154,563
Net earnings attributable to Martin Marietta	$ 185,051	$ 151,986	$ 399,113	$ 300,458
Diluted EPS	$ 2.93	$ 2.41	$ 6.31	$ 4.75