Significant Accounting Policies (Policy)	9 Months Ended
Significant Accounting Policies (Policy)	Sep. 30, 2011
Significant Accounting Policies
Basis Of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements of Martin Marietta Materials, Inc. (the "Corporation") have been prepared in accordance with generally accepted accounting principles for interim financial information and with the instructions to the Quarterly Report on Form 10-Q and to Article 10 of Regulation S-X. The Corporation has continued to follow the accounting policies set forth in the audited consolidated financial statements and related notes thereto included in the Corporation's Annual Report on Form 10-K for the year ended December 31, 2010, filed with the Securities and Exchange Commission on February 25, 2011. In the opinion of management, the interim financial information provided herein reflects all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results of operations, financial position and cash flows for the interim periods. The results of operations for the quarter and nine months ended September 30, 2011 are not indicative of the results expected for other interim periods or the full year. The balance sheet at December 31, 2010 has been derived from the audited financial statements at that date but does not include all of the information and notes required by generally accepted accounting principles for complete financial statements. These financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Corporation's Annual Report on Form 10-K for the year ended December 31, 2010.
Earnings Per Common Share	Earnings per Common Share The numerator for basic and diluted earnings per common share is net earnings attributable to Martin Marietta Materials, Inc., reduced by dividends and undistributed earnings attributable to the Corporation's unvested restricted stock awards and incentive stock awards. The denominator for basic earnings per common share is the weighted-average number of common shares outstanding during the period. Diluted earnings per common share are computed assuming that the weighted-average number of common shares is increased by the conversion, using the treasury stock method, of awards to be issued to employees and nonemployee members of the Corporation's Board of Directors under certain stock-based compensation arrangements if the conversion is dilutive. The diluted per-share computations reflect a change in the number of common shares outstanding (the denominator) to include the number of additional shares that would have been outstanding if the potentially dilutive common shares had been issued.
Comprehensive Earnings/Loss	Comprehensive Earnings/Loss Consolidated comprehensive earnings/loss for the Corporation consists of consolidated net earnings or loss; adjustments for the funded status of pension and postretirement benefit plans; foreign currency translation adjustments; and the amortization of the value of terminated forward starting interest rate swap agreements into interest expense. Consolidated comprehensive earnings for the three and nine months ended September 30, 2011 was $50,091,000 and $72,592,000, respectively. Consolidated comprehensive earnings for the three and nine months ended September 30, 2010 was $55,495,000 and $91,293,000, respectively.

Disclosure of accounting policy for computing basic and diluted earnings or loss per share for each class of common stock and participating security. Addresses all significant policy factors, including any antidilutive items that have been excluded from the computation and takes into account stock dividends, splits and reverse splits that occur after the balance sheet date of the latest reporting period but before the issuance of the financial statements.