Stock Options And Employee Stock Purchase Plan (Tables)

12 Months Ended

Dec. 31, 2016

Stock option activity for the years ended December 31, 2016, 2015 and 2014 is summarized as follows:



	Number of Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (In Years)	Aggregate Intrinsic Value
Options outstanding at January 1, 2014	1,175,657		$	21.08
Granted	—		—
Exercised	(433,008	)	15.70
Canceled	(17,000	)	29.85
Options outstanding at December 31, 2014	725,649		$	24.29
Granted	62,000		67.35
Exercised	(221,221	)	22.41
Canceled	—		—
Options outstanding at December 31, 2015	566,428		$	29.74
Granted	—		—
Exercised	(142,870	)	26.04
Canceled	(9,700	)	26.92
Options outstanding at December 31, 2016	413,858		$	31.09	3.8	$20,988,138
Exercisable at December 31, 2016	353,258		$	26.10	3.1	$19,676,668
Vested and expected to vest at December 31, 2016	402,809		$	30.14	3.7	$20,809,814

The following table summarizes information concerning outstanding and exercisable options as of December 31, 2016:



	Options Outstanding				Exercisable Options
Range of Exercise Prices	Number Outstanding December 31, 2016	Weighted Average Remaining Contractual Life	Weighted Average Exercise Price		Number Exercisable December 31, 2016	Weighted Average Exercise Price
$17.19	24,000	2.18 years	$	17.19	24,000	$	17.19
20.91	45,558	1.34 years	20.91		45,558	20.91
21.67	53,376	2.35 years	21.67		53,376	21.67
21.88	347	0.95 years	21.88		347	21.88
22.92	84,092	3.35 years	22.92		84,092	22.92
24.61 - 28.52	29,200	3.18 years	26.67		23,200	26.79
29.34	75,585	4.36 years	29.34		75,585	29.34
29.53 - 31.07	21,700	5.05 years	30.06		16,700	30.22
32.45	18,000	0.59 years	32.45		18,000	32.45
67.35	62,000	8.35 years	67.35		12,400	67.35
$17.19 - $67.35	413,858	3.82 years	$	31.09	353,258	$	26.10

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



	Years Ended December 31,
	2016	2015	2014
Risk-free interest rate	—%	1.61%	—%
Expected term (in years)	0.0	5.2	0.0
Dividend yield	—%	1.8%	—%
Expected volatility	—%	28.12%	—%
Weighted average volatility	—%	28.12%	—%

The weighted-average fair values of market-based restricted stock awards granted have been estimated utilizing the following assumptions:



	December 31, 2016
Underlying stock price at valuation date	$	63.73
Expected volatility	29.8		%
Risk-free interest rate	1.51		%

Restricted stock award activity for the years ended December 31, 2016, 2015 and 2014 is set forth below:



	Shares		Weighted-Average Grant-Date Fair Value
Nonvested at January 1, 2014	1,178,371		$	17.86
Granted	226,864		45.66
Vested	(546,115	)	15.63
Canceled	(45,070	)	35.55
Nonvested at December 31, 2014	814,050		$	26.57
Granted	234,540		68.11
Vested	(254,871	)	25.16
Canceled	(88,915	)	40.97
Nonvested at December 31, 2015	704,804		$	39.08
Granted	296,414		41.27
Vested	(255,503	)	31.27
Canceled	(40,700	)	63.95
Nonvested at December 31, 2016	705,015		$	41.40

Restricted stock unit activity for the years ended December 31, 2016, 2015 and 2014 is set forth below:



	Number of Shares		Weighted-Average Remaining Contractual Life (in Years)	Aggregate Intrinsic Value
Outstanding at January 1, 2014	109,725
Granted	38,737
Vested	(19,598	)
Canceled	(25,940	)
Outstanding at December 31, 2014	102,924
Granted	18,400
Vested	(23,221	)
Canceled	(41,858	)
Outstanding at December 31, 2015	56,245
Granted	21,500
Vested	(14,595	)
Canceled	(11,200	)
Outstanding at December 31, 2016	51,950		1.8	$	4,249,510
Vested and expected to vest at December 31, 2016	41,163		1.6	$	3,367,103