Earnings per Common Share (Tables)

9 Months Ended

Sep. 30, 2018

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 September 30,					Nine Months Ended September 30,
	2018		2017			2018		2017
(Dollars in millions, except share amounts, in thousands, and per share amounts)
Net income attributable to Koppers	$	7.6	$	19.8		$	26.0	$	43.9
Less: Income (loss) from discontinued operations		0.0		(0.1	)		0.4		(1.3	)
Income from continuing operations attributable to    Koppers	$	7.6	$	19.9		$	25.6	$	45.2
Weighted average common shares outstanding:
Basic		20,946		20,746			20,992		20,750
Effect of dilutive securities		754		1,165			900		1,177
Diluted		21,700		21,911			21,892		21,927
Income per common share – continuing operations:
Basic income per common share	$	0.36	$	0.96		$	1.22	$	2.17
Diluted income per common share		0.35		0.91			1.17		2.06
Other data:
Antidilutive securities excluded from computation of    diluted earnings per common share		571		543			214		482