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Significant Accounting Policies - Comprehensive Earnings Attributable to Martin Marietta Materials Incorporated (Detail) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]        
Net earnings attributable to Martin Marietta $ 225.8 $ 217.6 $ 291.1 $ 243.5
Other comprehensive earnings, net of tax 2.6 3.2 5.4 3.6
Earnings attributable to Martin Marietta Materials, Inc. $ 228.4 $ 220.8 $ 296.5 $ 247.1