Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Stock-Based Compensation [Abstract]

Weighted Average Assumptions Used to Determine Fair Value for Stock Awards

The fair value for stock awards was estimated at the date of grant using the Black-Scholes option valuation model with the following weighted average assumptions for the years ended December 31, 2019, 2018 and 2017:

	Year Ended December 31,
	2019			2018			2017
Expected life (in years)		6.6			6.2			6.4
Interest rate		2.62	%		2.50	%		2.04	%
Volatility		30.26	%		30.33	%		36.61	%
Expected dividend yield		0.37	%		0.26	%		0.26	%

Summary of Stock Option Activity

The following table summarizes stock option activity for the year ended December 31, 2019:

	Awards			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value (Millions)
Awards outstanding at December 31, 2018		1,054,259		$	54.04
Granted		271,261			54.44
Exercised		(79,686	)		27.26
Canceled		(14,214	)		66.93
Expired		(4,000	)		19.86
Awards outstanding at December 31, 2019		1,227,620		$	55.83		6.20		$	9.2
Awards exercisable at December 31, 2019		788,847		$	51.75		4.90		$	8.3

Non-vested Stock Option Activity

Non-vested stock option activity for the year ended December 31, 2019 is as follows:

	Awards			Weighted Average Grant Date Fair Value per Share
Nonvested awards outstanding at December 31, 2018		365,607		$	68.86
Granted		271,261			54.44
Vested		(189,854	)		61.64
Canceled		(8,241	)		64.19
Nonvested awards outstanding at December 31, 2019		438,773		$	63.15

Summary of Restricted Stock Activity

The following table summarizes the restricted stock activity for the Plan:

	Awards			Weighted Average Grant Date Fair Value per Share
Unvested balance at December 31, 2018		134,578		$	68.64
Granted		116,901			54.51
Vested		(40,776	)		60.79
Canceled		(32,967	)		61.87
Unvested balance at December 31, 2019		177,736		$	62.40