Stock Options And Employee Stock Purchase Plan (Tables)

12 Months Ended

Dec. 31, 2018

Stock option activity for the years ended December 31, 2018, 2017 and 2016 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, 2016	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
Granted	—		—
Exercised	(38,183	)	29.03
Canceled	—		—
Options outstanding at December 31, 2017	375,675		$	31.30
Granted	400,000		75.03
Exercised	(67,898	)	22.68
Canceled	—		—
Options outstanding at December 31, 2018	707,777		$	56.84	5.8	$11,136,166
Exercisable at December 31, 2018	298,577		$	32.15	1.5	$11,117,490
Vested and expected to vest at December 31, 2018	575,851		$	52.68	5.1	$11,134,316

The following table summarizes information concerning outstanding and exercisable options as of December 31, 2018:



	Options Outstanding				Exercisable Options
Range of Exercise Prices	Number Outstanding December 31, 2018	Weighted Average Remaining Contractual Life	Weighted Average Exercise Price		Number Exercisable December 31, 2018	Weighted Average Exercise Price
$17.19	20,000	0.18 years	$	17.19	20,000	$	17.19
21.67	50,040	0.35 years	21.67		50,040	21.67
22.92	84,092	1.35 years	22.92		84,092	22.92
25.09	2,600	3.36 years	25.09		2,600	25.09
29.34	75,585	2.36 years	29.34		75,585	29.34
29.53	9,710	3.17 years	29.53		9,710	29.53
31.07	3,750	2.82 years	31.07		3,750	31.07
67.35	62,000	2.51 years	67.35		52,800	67.35
75.03	400,000	9.00 years	75.03		—	—
$17.19 - $75.03	707,777	5.82 years	$	56.84	298,577	$	32.15

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



	Years Ended December 31,
	2018	2017	2016
Risk-free interest rate	2.4%	—%	—%
Expected term (in years)	6.7	0.0	0.0
Dividend yield	2.2%	—%	—%
Expected volatility	29.2%	—%	—%
Weighted average volatility	29.2%	—%	—%

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



	December 31, 2018			December 31, 2017			December 31, 2016
Underlying stock price at valuation date	$	82.11		$	91.17		$	63.73
Expected volatility	28.4		%	29		%	29.8		%
Risk-free interest rate	2.89		%	2.17		%	1.51		%

Restricted stock award activity for the years ended December 31, 2018, 2017 and 2016 is set forth below:



	Shares		Weighted-Average Grant-Date Fair Value
Nonvested at January 1, 2016	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
Granted	289,230		61.34
Vested	(381,411	)	39.71
Canceled	(7,268	)	76.08
Nonvested at December 31, 2017	605,566		$	51.57
Granted	830,256		63.55
Vested	(157,972	)	61.29
Canceled	(70,839	)	74.84
Nonvested at December 31, 2018	1,207,011		$	64.82

Restricted stock unit activity for the years ended December 31, 2018, 2017 and 2016 is set forth below:



	Number of Shares		Weighted-Average Remaining Contractual Life (in Years)	Aggregate Intrinsic Value
Outstanding at January 1, 2016	56,245
Granted	21,500
Vested	(14,595	)
Canceled	(11,200	)
Outstanding at December 31, 2016	51,950
Granted	11,100
Vested	(16,370	)
Canceled	(8,280	)
Outstanding at December 31, 2017	38,400
Granted	20,044
Vested	(11,540	)
Canceled	(5,673	)
Outstanding at December 31, 2018	41,231		2.0	$	2,860,607
Vested and expected to vest at December 31, 2018	32,809		1.7	$	2,276,290