Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [Abstract]

Stock Option Activity

The following table summarizes the Company’s stock option activity and related information for the 2011 Plan, the 2000 Plan and the Directors Plan for the six months ended June 30, 2019:

	Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life	Aggregate Intrinsic value (in thousands)
Outstanding at December 31, 2018	466,677		$	61.04	5.7	$	5,003
Granted	132,155		70.46			172
Exercised	(468	)	64.54			(19		)
Canceled	(3,148	)	73.34			—
Outstanding at June 30, 2019	595,216		63.08		6.2	5,168
Exercisable at June 30, 2019	388,634		54.89		5.2	6,558

Share-Based Fair Value of Each Option Grant Weighted-Average Assumptions

The fair value of each option grant is estimated on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

	Six Months Ended June 30,
	2019		2018
Dividend yield	0.66	%	0.31	%
Risk-free interest rate	2.61	%	2.78	%
Stock price volatility	25.8	%	23.9	%
Expected life (years)	5.0		5.0

Restricted Stock Activity and Incentive Stock Awards Activity

The following table summarizes the restricted stock activity and related information for the 2011 Plan, the 2000 Plan and the Directors Plan, and incentive stock units activity for the 2011 Plan and the 2000 Plan with related information for the six months ended June 30, 2019:

	Restricted Stock and Units		Incentive Stock Units		Weighted Average Grant Date Fair Value
Outstanding at December 31, 2018	445,089		415,243		$	75.51
Granted	568,052		258,100		70.48
Vested	(207,656	)	(119,835	)	71.59
Adjustment for incentive stock awards expected to vest	—		43,257		78.82
Canceled	(11,041	)	(38,116	)	74.38
Outstanding at June 30, 2019	794,444		558,649		73.53