Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 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 June 30, 2020
Balance at beginning of period	$	(142.4	)	$	(3.0	)	$	(145.4	)
Other comprehensive earnings before reclassifications,    net of tax		—			0.8			0.8
Amounts reclassified from accumulated other    comprehensive loss, net of tax		2.4			—			2.4
Other comprehensive earnings, net of tax		2.4			0.8			3.2
Balance at end of period	$	(140.0	)	$	(2.2	)	$	(142.2	)
	Three Months Ended June 30, 2019
Balance at beginning of period	$	(138.7	)	$	(1.6	)	$	(140.3	)
Other comprehensive earnings before reclassifications,    net of tax		—			0.3			0.3
Amounts reclassified from accumulated other    comprehensive loss, net of tax		2.7			—			2.7
Other comprehensive earnings, net of tax		2.7			0.3			3.0
Balance at end of period	$	(136.0	)	$	(1.3	)	$	(137.3	)
	(Dollars in Millions)
	Pension and Postretirement Benefit Plans			Foreign Currency			Accumulated Other Comprehensive Loss
	Six Months Ended June 30, 2020
Balance at beginning of period	$	(144.9	)	$	(0.9	)	$	(145.8	)
Other comprehensive loss before    reclassifications, net of tax		—			(1.3	)		(1.3	)
Amounts reclassified from accumulated    other comprehensive loss, net of tax		4.9			—			4.9
Other comprehensive earnings (loss), net of tax		4.9			(1.3	)		3.6
Balance at end of period	$	(140.0	)	$	(2.2	)	$	(142.2	)
	Six Months Ended June 30, 2019
Balance at beginning of period	$	(141.5	)	$	(2.1	)	$	(143.6	)
Other comprehensive earnings before    reclassifications, net of tax		—			0.8			0.8
Amounts reclassified from accumulated    other comprehensive loss, net of tax		5.5			—			5.5
Other comprehensive earnings, net of tax		5.5			0.8			6.3
Balance at end of period	$	(136.0	)	$	(1.3	)	$	(137.3	)

Noncurrent Deferred Tax Assets Recorded In Accumulated Other Comprehensive Loss

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

	Pension and Postretirement Benefit Plans
	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2020			2019			2020			2019
	(Dollars in Millions)
Balance at beginning of period	$	84.4		$	83.3		$	85.2		$	84.2
Tax effect of other comprehensive earnings		(0.8	)		(0.9	)		(1.6	)		(1.8	)
Balance at end of period	$	83.6		$	82.4		$	83.6		$	82.4

Reclassification Out of Accumulated Other Comprehensive Loss

Reclassifications out of accumulated other comprehensive loss are as follows:

	Three Months Ended						Six Months Ended						Affected line items in the consolidated
	June 30,						June 30,						statements of earnings and
	2020			2019			2020			2019			comprehensive earnings
	(Dollars in Millions)
Pension and postretirement    benefit plans
Amortization of:
Prior service credit	$	—		$	(0.2	)	$	(0.1	)	$	(0.4	)
Actuarial loss		3.2			3.8			6.6			7.7
		3.2			3.6			6.5			7.3		Other nonoperating (income) and expenses, net
Tax benefit		(0.8	)		(0.9	)		(1.6	)		(1.8	)	Income tax expense
	$	2.4		$	2.7		$	4.9		$	5.5

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				Six Months Ended
	June 30,				June 30,
	2020		2019		2020		2019
	(In Millions)
Net earnings attributable to Martin Marietta	$	217.6	$	189.5	$	243.5	$	232.3
Less: Distributed and undistributed earnings    attributable to unvested awards		0.2		0.4		0.2		0.5
Basic and diluted net earnings available to common    shareholders attributable to Martin Marietta	$	217.4	$	189.1	$	243.3	$	231.8
Basic weighted-average common shares outstanding		62.3		62.6		62.3		62.6
Effect of dilutive employee and director awards		—		0.1		0.1		0.1
Diluted weighted-average common shares    outstanding		62.3		62.7		62.4		62.7

Parent

Significant Accounting Policies [Line Items]

Comprehensive Earnings

Comprehensive earnings attributable to Martin Marietta is as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2020		2019		2020		2019
	(Dollars in Millions)
Net earnings attributable to Martin Marietta	$	217.6	$	189.5	$	243.5	$	232.3
Other comprehensive earnings, net of tax		3.2		3.0		3.6		6.3
Comprehensive earnings attributable to Martin    Marietta	$	220.8	$	192.5	$	247.1	$	238.6