v3.26.1
Fair Value Measurements - Schedule of Fair Value Hierarchy of Plan's Assets and Estimated Fair Value of Plan's Investment Funds (Details) - EBP 006 - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value $ 1,041,346 $ 878,295
Martin Marietta Materials, Inc. Common Stock    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 60,667 56,373
Mutual Funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 141,373 128,266
Collective Trust Fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 346  
Collective Trust Funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 839,306 693,656
Level 1 | Martin Marietta Materials, Inc. Common Stock    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 60,667 56,373
Level 1 | Mutual Funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 141,373 128,266
Level 1 | Collective Trust Fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 346  
Fair Value Measured at Net Asset Value Per Share    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 838,960 693,656
Fair Value Measured at Net Asset Value Per Share | Galliard Stable Return Fund E    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value $ 62,771 66,293
Redemption Notice Period 12 months  
Fair Value Measured at Net Asset Value Per Share | BlackRock Equity Index Fund J    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value $ 126,461 106,076
Fair Value Measured at Net Asset Value Per Share | Harbor Capital Appreciation R    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 70,339 62,958
Fair Value Measured at Net Asset Value Per Share | BlackRock LifePath Portfolios Class O    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 565,338 447,863
Fair Value Measured at Net Asset Value Per Share | BlackRock Mid Cap Equity Index Fund M    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 10,582 8,536
Fair Value Measured at Net Asset Value Per Share | BlackRock Russell 2000 Index Fund M    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 1,624 931
Fair Value Measured at Net Asset Value Per Share | BlackRock US Debt Index Fund M    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value 1,845 999
Fair Value Measured at Net Asset Value Per Share | Collective Trust Funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Investments at fair value $ 838,960 $ 693,656