Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

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)	2018			2017
Stock-based compensation expense	$	3.0		$	3.2
Tax benefit		(0.6	)		(1.1	)
Stock-based compensation expense, net of taxes	$	2.4		$	2.1

Summary of Stock Option Activity

Information on the Company’s stock option activity for the three months ended March 31, 2018 and 2017 is summarized below.

	Three Months Ended March 31,
	2018					2017
(in whole shares and dollars)	Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price
Outstanding, beginning of period		1,062,177		$	75.53		1,396,152		$	68.63
Granted		291,390			110.58		417,690			91.18
Exercised		(84,353	)		70.31		(148,529	)		59.71
Forfeited or cancelled		(50,491	)		88.48		(2,334	)		67.62
Outstanding, end of period		1,218,723			83.73		1,662,979			75.10

Summary of Restricted Stock Activity

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

	Three Months Ended March 31,
	2018					2017
(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		298,528		$	83.45		269,063		$	73.91
Granted		131,290			110.60		105,410			91.18
Vested		(50,810	)		70.24		(69,030	)		58.72
Forfeited		(10,585	)		87.47		(3,005	)		82.75
Outstanding, end of period		368,423			94.83		302,438			83.31
Performance-based and market-based restricted stock units:
Outstanding, beginning of period		102,586		$	81.21		115,057		$	78.82
Granted		29,715			116.82		54,751			78.76
Vested		(14,032	)		70.24		(17,042	)		57.99
Forfeited		(7,625	)		81.91		(2,180	)		95.36
Outstanding, end of period		110,644			92.12		150,586			80.92