Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Compensation Cost and Related Tax Benefits

Compensation cost for the Company’s stock-based awards and the related tax benefits were as follows:

	Three Months Ended March 31,
(in millions)	2019			2018
Stock-based compensation expense	$	4.2		$	2.5
Tax benefit		(0.9	)		(0.5	)
Stock-based compensation expense, net of taxes	$	3.3		$	2.0

Summary of Stock Option Plan Activity

Information on the Company’s stock option activity for the three months ended March 31, 2019 and 2018 is summarized below.

	Three Months Ended March 31,
	2019					2018
(in whole shares and dollars)	Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price
Outstanding, beginning of period		1,099,076		$	85.75		1,062,177		$	75.53
Granted		232,568			95.05		291,390			110.58
Exercised		(64,017	)		75.98		(84,353	)		70.31
Forfeited or cancelled		(3,141	)		95.39		(50,491	)		88.48
Outstanding, end of period		1,264,486			87.93		1,218,723			83.73

Summary of Restricted Stock Activity

The following tables summarize activity information about employee restricted stock units:

	Three Months Ended March 31,
	2019					2018
(in whole shares and dollars)	Shares			Weighted Average Grant Date Fair Value		Shares			Weighted Average Grant Date Fair Value
Time-based restricted stock units:
Outstanding, beginning of period		332,481		$	97.28		298,528		$	83.45
Granted		144,072			117.51		131,290			110.60
Vested		(99,855	)		83.25		(50,810	)		70.24
Forfeited		(8,687	)		97.14		(10,585	)		87.47
Outstanding, end of period		368,011			109.01		368,423			94.83
Performance-based and market-based restricted stock units:
Outstanding, beginning of period		69,838		$	95.58		102,586		$	81.21
Granted		42,119			117.68		29,715			116.82
Vested		(10,089	)		82.74		(14,032	)		70.24
Forfeited		—			—		(7,625	)		81.91
Outstanding, end of period		101,868			105.99		110,644			92.12