Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2020

Significant Accounting Policies [Line Items]

Changes in Accumulated Other Comprehensive Loss Net of Tax

Changes in accumulated other comprehensive loss, net of tax, are as follows:  

	(Dollars in Millions)
	Pension and Postretirement Benefit Plans			Foreign Currency			Accumulated Other Comprehensive Loss
	Three Months Ended March 31, 2020
Balance at beginning of period	$	(144.9	)	$	(0.9	)	$	(145.8	)
Other comprehensive loss before reclassifications,    net of tax		—			(2.1	)		(2.1	)
Amounts reclassified from accumulated other    comprehensive loss, net of tax		2.5			—			2.5
Other comprehensive earnings (loss), net of tax		2.5			(2.1	)		0.4
Balance at end of period	$	(142.4	)	$	(3.0	)	$	(145.4	)
	Three Months Ended March 31, 2019
Balance at beginning of period	$	(141.5	)	$	(2.1	)	$	(143.6	)
Other comprehensive earnings before reclassifications,    net of tax		—			0.5			0.5
Amounts reclassified from accumulated other    comprehensive loss, net of tax		2.7			—			2.7
Other comprehensive earnings, net of tax		2.7			0.5			3.2
Balance at end of period	$	(138.8	)	$	(1.6	)	$	(140.4	)

Noncurrent Deferred Tax Assets Recorded In Accumulated Other Comprehensive Loss

Changes in net noncurrent deferred tax assets recorded in accumulated other comprehensive loss are as follows:

	(Dollars in Millions)
	Pension and Postretirement Benefit Plans
	Three Months Ended March 31, 2020
Balance at beginning of period	$	85.2
Tax effect of other comprehensive earnings		(0.8	)
Balance at end of period	$	84.4
	Three Months Ended March 31, 2019
Balance at beginning of period	$	84.2
Tax effect of other comprehensive earnings		(0.9	)
Balance at end of period	$	83.3

Reclassification Out of Accumulated Other Comprehensive Loss

Reclassifications out of accumulated other comprehensive loss are as follows:

	Three Months Ended						Affected line items in the consolidated
	March 31,						statements of earnings and
	2020			2019			comprehensive earnings
	(Dollars in Millions)
Pension and postretirement benefit    plans
Amortization of:
Prior service credit	$	—		$	(0.2	)
Actuarial loss		3.3			3.8
		3.3			3.6		Other nonoperating expenses and (income),    net
Tax benefit		(0.8	)		(0.9	)	Income tax expense (benefit)
	$	2.5		$	2.7

Basic and Diluted Earnings Per Common Share

The following table reconciles the numerator and denominator for basic and diluted earnings per common share:

	Three Months Ended
	March 31,
	2020		2019
	(In Millions)
Net earnings attributable to Martin Marietta    Materials, Inc.	$	25.9	$	42.9
Less: Distributed and undistributed earnings    attributable to unvested awards		—		0.1
Basic and diluted net earnings available to common    shareholders attributable to Martin Marietta    Materials, Inc.	$	25.9	$	42.8
Basic weighted-average common shares outstanding		62.3		62.6
Effect of dilutive employee and director awards		0.2		0.2
Diluted weighted-average common shares outstanding		62.5		62.8

Parent

Significant Accounting Policies [Line Items]

Comprehensive Earnings

Comprehensive earnings attributable to Martin Marietta is as follows:

	Three Months Ended
	March 31,
	2020		2019
	(Dollars in Millions)
Net earnings attributable to Martin Marietta Materials, Inc.	$	25.9	$	42.9
Other comprehensive earnings, net of tax		0.4		3.2
Comprehensive earnings attributable to Martin Marietta    Materials, Inc.	$	26.3	$	46.1