Significant Accounting Policies - Comprehensive Earnings Attributable to Martin Marietta Materials Incorporated (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net earnings attributable to Martin Marietta Materials, Inc.	$ 185,377	$ 142,279	$ 195,400	$ 184,613
Other comprehensive earnings, net of tax	1,602	2,519	3,221	4,781
Earnings attributable to Martin Marietta Materials, Inc.	$ 186,979	$ 144,798	$ 198,621	$ 189,394