Business Combination - Business Acquisition, Pro Forma Information (Details) - Bluegrass Materials Company - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Business Acquisition [Line Items]
Total revenues	$ 1,218,904	$ 1,121,258	$ 2,059,816	$ 2,005,775
Net earnings attributable to Martin Marietta	$ 207,886	$ 140,338	$ 216,756	$ 150,011
Diluted EPS	$ 3.28	$ 2.22	$ 3.43	$ 2.37