Stock Options And Employee Stock Purchase Plan (Tables)

6 Months Ended

Jun. 30, 2015

The following table represents stock option activity for the six months ended June 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	(127,838	)	23.53
Canceled	—		—
Outstanding at June 30, 2015	659,811		$	28.49	4.4	$	26,032,294
Exercisable at June 30, 2015	544,675		$	24.08	3.6	$	23,891,847
Vested and expected to vest at June 30, 2015	633,034		$	27.26	4.2	$	25,752,888

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



	Six Months Ended June 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 six months ended June 30, 2015 is set forth below:



	Shares		Weighted-Average Grant-Date Fair Value
Nonvested at January 1, 2015	814,050		$	26.57
Granted	147,440		66.04
Vested	(124,683	)	36.69
Canceled	(74,515	)	38.17
Nonvested at June 30, 2015	762,292		$	31.41

Restricted stock unit award activity for the six months ended June 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	10,900
Vested	(13,081	)
Canceled	(7,790	)
Outstanding at June 30, 2015	92,953		1.9	$	6,315,227
Vested and expected to vest at June 30, 2015	71,843		1.7	$	4,880,982