Stock Options And Employee Stock Purchase Plan (Tables)

9 Months Ended

Sep. 30, 2015

The following table represents stock option activity for the nine months ended September 30, 2015:



	Number of Shares		Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at January 1, 2015	725,649		$	24.29
Granted	62,000		67.35
Exercised	(205,621	)	22.19
Canceled	—		—
Outstanding at September 30, 2015	582,028		$	29.62	4.6	$	24,012,309
Exercisable at September 30, 2015	470,392		$	24.77	3.7	$	21,687,481
Vested and expected to vest at September 30, 2015	557,548		$	28.34	4.4	$	23,718,233

The weighted-average fair values of stock options granted have been estimated utilizing the following assumptions:



	Nine Months Ended September 30,
	2015		2014
Risk-free interest rate	1.61	%	—	%
Expected term (in years)	5.2 years		0.0 years
Dividend yield	1.78	%	—	%
Expected volatility	28.12	%	—	%
Weighted-average volatility	28.12	%	—	%

Restricted stock award activity for the nine months ended September 30, 2015 is set forth below:



	Shares		Weighted-Average Grant-Date Fair Value
Nonvested at January 1, 2015	814,050		$	26.57
Granted	211,040		67.06
Vested	(155,733	)	35.19
Canceled	(84,515	)	40.55
Nonvested at September 30, 2015	784,842		$	34.24

Restricted stock unit award activity for the nine months ended September 30, 2015 is set forth below:



	Number of Shares		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at January 1, 2015	102,924
Granted	15,900
Vested	(17,081	)
Canceled	(37,058	)
Outstanding at September 30, 2015	64,685		1.9	$	4,584,873
Vested and expected to vest at September 30, 2015	49,599		1.6	$	3,515,573