Earnings per Common Share (Tables)

3 Months Ended

Mar. 31, 2020

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Earnings per Common Share

The following table sets forth the computation of basic and diluted earnings per common share:

	Three Months Ended March 31,
	2020			2019
(Dollars in millions, except share amounts, in thousands)
Net (loss) income attributable to Koppers	$	(1.4	)	$	11.6
(Loss) income from discontinued operations		(4.4	)		2.7
Non-controlling loss (income) from discontinued operations		1.1			(0.9	)
Income from continuing operations attributable to Koppers	$	1.9		$	9.8
Weighted average common shares outstanding:
Basic		20,852			20,575
Effect of dilutive securities		463			306
Diluted		21,315			20,881
Earnings per common share – continuing operations:
Basic earnings per common share	$	0.09		$	0.47
Diluted earnings per common share		0.09			0.47
Other data:
Antidilutive securities excluded from computation of    diluted earnings per common share		682			534