Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2020

Stockholders' Equity Note [Abstract]

Stock Option Plan Activity and Stock Options Granted

The following tables summarize the details of options granted under our stock option plans that were still outstanding as of December 31, 2020, 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, 2020
Date of Grant				Options Outstanding	Options Exercisable
January 2, 2020	902,263	$38.00	$37.230	874,112	24,964
January 2, 2019	1,316,924	$26.00	$25.705	1,221,248	25,010
January 2, 2018	1,087,936	$27.50	$27.270	886,679	270,457
January 3, 2017	1,529,578	$23.50	$23.475	988,415	378,747
April 19, 2016	1,690,880	$23.00	$22.870	930,043	589,137
April 21, 2015	1,786,440	$21.00	$20.630	596,622	350,526
April 22, 2014	1,910,000	$28.00	$25.265	337,550	185,050
April 16, 2013	410,000	$27.00	$24.625	32,340	13,602
April 17, 2012	2,470,000	$27.00	$24.505	47,748	47,748
Total	13,104,021			5,914,757	1,885,241

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, 2020	6,807,217	$	24.890	6.09
Granted	902,263	$	38.000	9.00
Exercised	(1,630,664)	$	25.180
Cancelled/forfeited	(164,059)	$	27.640
Outstanding as of December 31, 2020	5,914,757	$	26.730	6.22
Exercisable as of December 31, 2020	1,885,241	$	24.230	4.71

	Options Outstanding	Exercise Price(1)		Remaining Life(2)
Outstanding as of January 1, 2019	7,999,264	$	24.765	5.61
Granted	1,316,924	$	26.000	9.00
Exercised	(2,325,073)	$	25.150
Cancelled/forfeited	(183,898)	$	24.630
Outstanding as of December 31, 2019	6,807,217	$	24.890	6.09
Exercisable as of December 31, 2019	2,164,067	$	24.510	4.30

(1) Weighted average exercise price.

(2) Weighted average remaining contractual life in years.

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, 2020	1.7%	5.00	2.4%	25.70	%	$6.81
January 2, 2019	2.5%	5.00	2.9%	23.96	%	$4.40
January 2, 2018	2.2%	5.00	2.3%	23.45	%	$5.02
January 3, 2017	1.9%	5.00	2.6%	24.49	%	$4.20
April 19, 2016	1.3%	5.00	2.6%	26.34	%	$4.09
April 21, 2015	1.3%	5.00	2.7%	26.84	%	$3.68
April 22, 2014	1.8%	5.00	2.0%	28.55	%	$4.79
April 16, 2013	0.7%	5.00	1.6%	37.42	%	$6.33
April 17, 2012	0.9%	5.00	1.4%	39.25	%	$6.85

Schedule of Common Stock Outstanding Roll Forward

Shares of common stock outstanding were as follows:

	2020	2019	2018
Balance at beginning of year	574,128,911	571,803,838	575,183,072
Stock options exercised	1,630,664	2,325,073	620,766
Purchases of common stock	(1,600,000)	—	(4,000,000)
Balance at end of year	574,159,575	574,128,911	571,803,838

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	2020	2019	2018
Basic weighted average shares outstanding	573,778,761	573,202,152	573,933,834
Weighted shares assumed upon exercise of stock options	1,893,193	1,239,476	391,694
Diluted weighted average shares outstanding	575,671,954	574,441,628	574,325,528

Anti-Dilutive Options Excluded

Summary of Anti-dilutive Options Excluded	2020		2019	2018
Options to purchase shares of common stock	846,041		—	3,159,514
Weighted average exercise prices of options	$	38.00	—	27.51