Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options And Performance Award Fair Value Assumptions

We calculated the fair value of stock options on the date of grant using the Black-Scholes-Merton model and the assumptions listed below:

	March 2020 Grant			March 2019 Grant			March 2018 Grant			March 2017 Grant
Grant date price per share of stock   option award	$	19.63		$	26.63		$	41.60		$	44.10
Expected dividend yield per share		0.00	%		0.00	%		0.00	%		0.00	%
Expected life in years		6.40			6.14			5.73			5.77
Expected volatility		42.85	%		39.44	%		37.05	%		39.70	%
Risk-free interest rate		0.87	%		2.53	%		2.67	%		2.13	%
Grant date fair value per share of option awards	$	8.42		$	11.29		$	16.38		$	17.90

Summary of Performance Stock Units

The following table shows a summary of the performance stock units as of March 31, 2020:

Performance Period	Minimum Shares		Target Shares		Maximum Shares
2018 – 2020		0		119,630		239,260
2019 – 2021		0		195,047		285,950
2020 – 2022		0		231,128		462,256

Summary of Status and Activity of Non-Vested Stock Awards

The following table shows a summary of the status and activity of non-vested stock units for the three months ended March 31, 2020:

	Restricted Stock Units			Performance Stock Units			Total Stock Units			Weighted Average Grant Date Fair Value per Unit
Non-vested at December 31, 2019		343,012			445,186			788,198		$	40.18
Granted		295,873			232,481			528,354		$	16.09
Vested		(102,369	)		(110,168	)		(212,537	)	$	47.19
Forfeited		(23,129	)		(21,694	)		(44,823	)	$	34.21
Non-vested at March 31, 2020		513,387			545,805			1,059,192		$	27.01

Summary of Status and Activity of Stock Options

The following table shows a summary of the status and activity of stock options for the three months ended March 31, 2020:

	Options			Weighted Average Exercise Price per Option		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2019		966,849		$	28.45
Granted		187,701		$	19.63
Expired		(5,129	)	$	31.28
Forfeited		(12,280	)	$	31.03
Outstanding at March 31, 2020		1,137,141		$	26.96		6.42	$	0.0
Exercisable at March 31, 2020		771,153		$	27.29		5.12	$	0.0

Schedule of Stock-based Compensation Expense Recognized

Total stock-based compensation expense recognized under our LTIP and employee stock purchase plan for the three months ended March 31, 2020 and 2019 is as follows:

	Three Months Ended March 31,
	2020		2019
(Dollars in millions)
Stock-based compensation expense recognized:
Selling, general and administrative expenses	$	2.5	$	2.9
Less related income tax benefit		0.8		0.9
Decrease in net income attributable to Koppers	$	1.7	$	2.0

Performance Stock Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options And Performance Award Fair Value Assumptions

We calculated the fair value of the performance stock unit awards on the date of grant using the assumptions listed below:

	March 2020 Grant			March 2019 Grant			May 2018 Grant			March 2018 Grant
Grant date price per share of   performance award	$	19.63		$	26.63		$	39.10		$	41.60
Expected dividend yield per   share		0.00	%		0.00	%		0.00	%		0.00	%
Expected volatility		45.60	%		39.00	%		39.40	%		39.40	%
Risk-free interest rate		0.72	%		2.50	%		2.35	%		2.35	%
Look-back period in years		2.83			2.82			2.84			2.84
Grant date fair value per share	$	11.56		$	40.30		$	44.29		$	47.12