Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Stockholders' Equity Note [Abstract]

Stock Option Plan Activity and Stock Options Granted

A summary of activities under our stock option plans consisted of the following:

	Options Outstanding		Exercise Price(1)		Remaining Life(2)
Outstanding as of January 1, 2018	3,948,908		$	48.28	5.89
Granted	543,968		$	55.00	9.00
Exercised	(310,383	)	$	43.31
Cancelled/forfeited	(182,861	)	$	48.86
Outstanding as of December 31, 2018	3,999,632		$	49.53	5.61
Exercisable as of December 31, 2018	1,554,378		$	51.06	3.69

	Options Outstanding		Exercise Price(1)		Remaining Life(2)
Outstanding as of January 1, 2017	3,757,947		$	46.81	5.85
Granted	764,789		$	47.00	9.00
Exercised	(329,612	)	$	28.59
Cancelled/forfeited	(244,216	)	$	48.22
Outstanding as of December 31, 2017	3,948,908		$	48.28	5.89
Exercisable as of December 31, 2017	1,280,499		$	50.07	3.78

⁽¹⁾ Weighted average exercise price.

⁽²⁾ Weighted average remaining contractual life in years.

The following tables summarize the details of options granted under our stock option plans that were still outstanding as of December 31, 2018, and the assumptions used to value those grants. All such grants were effective at the close of business on the date of grant.

	Options Granted	Option Exercise (Strike) Price		Closing Stock Price on Date of Grant		December 31, 2018
Date of Grant						Options Outstanding	Options Exercisable
January 2, 2018	543,968	$	55.00	$	54.54	524,256	21,185
January 3, 2017	764,789	$	47.00	$	46.95	679,700	—
April 19, 2016	845,440	$	46.00	$	45.74	683,889	194,672
April 21, 2015	893,220	$	42.00	$	41.26	622,301	185,528
April 22, 2014	955,000	$	56.00	$	50.53	511,250	332,250
April 16, 2013	205,000	$	54.00	$	49.25	88,123	54,380
April 17, 2012	1,235,000	$	54.00	$	49.01	812,063	700,813
April 19, 2011	410,000	$	35.00	$	31.78	49,650	37,150
April 20, 2010	530,000	$	30.00	$	27.13	28,400	28,400
Total	6,382,417					3,999,632	1,554,378

Fair Value Assumptions for Options Granted

Date of Grant	Risk-free Interest Rate		Expected Life of Option in Years	Expected Dividend Yield		Expected Stock Volatility		Estimated Fair Value of Stock Option
January 2, 2018	2.2	%	5.00	2.3	%	23.45	%	$	10.03
January 3, 2017	1.9	%	5.00	2.6	%	24.49	%	$	8.40
April 19, 2016	1.3	%	5.00	2.6	%	26.34	%	$	8.18
April 21, 2015	1.3	%	5.00	2.7	%	26.84	%	$	7.35
April 22, 2014	1.8	%	5.00	2.0	%	28.55	%	$	9.57
April 16, 2013	0.7	%	5.00	1.6	%	37.42	%	$	12.66
April 17, 2012	0.9	%	5.00	1.4	%	39.25	%	$	13.69
April 19, 2011	2.1	%	5.00	1.6	%	39.33	%	$	11.20
April 20, 2010	2.6	%	5.00	1.5	%	39.10	%	$	8.14

Reconciliation of Denominators used in Computation of Basic and Diluted Earnings per Share

The following tables present a reconciliation of the denominators used in the computation of basic and diluted earnings per share and a summary of the options to purchase shares of common stock which were excluded from the diluted earnings calculation because they were anti-dilutive:

Reconciliation	2018	2017	2016
Basic weighted average shares outstanding	286,966,917	288,208,435	288,949,525
Weighted shares assumed upon exercise of stock options	195,847	134,298	207,998
Diluted weighted average shares outstanding	287,162,764	288,342,733	289,157,523

Anti-Dilutive Options Excluded

Summary of Anti-dilutive Options Excluded	2018		2017	2016
Options to purchase shares of common stock	1,579,757		3,524,401	3,095,343
Weighted average exercise prices of options	$	55.02	49.85	50.09