Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2018

Stockholders' Equity Note [Abstract]

Schedule of Dividends Paid Previously or Declared

The following table presents the dividends either paid previously or declared by our board of directors for future payment on a per share basis:

	2018		2017
First quarter	$	0.37	0.32
Second quarter	0.37		0.32
Third quarter	0.40		0.32
Fourth quarter			0.32
Total	$	1.14	1.28

Stock Options Granted

The following tables summarize the details of options granted under our stock option plan that were still outstanding as of June 30, 2018, and the assumptions used to value these 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		June 30, 2018
Date of Grant						Options Outstanding	Options Exercisable
January 2, 2018	541,786	$	55.00	$	54.54	528,250	21,185
January 3, 2017	764,789	$	47.00	$	46.95	690,762	—
April 19, 2016	845,440	$	46.00	$	45.74	710,137	—
April 21, 2015	893,220	$	42.00	$	41.26	640,306	136,150
April 22, 2014	955,000	$	56.00	$	50.53	539,500	331,250
April 16, 2013	205,000	$	54.00	$	49.25	98,000	64,257
April 17, 2012	1,235,000	$	54.00	$	49.01	903,313	790,813
April 19, 2011	410,000	$	35.00	$	31.78	54,850	42,350
April 20, 2010	530,000	$	30.00	$	27.13	36,400	36,400
Total	6,380,235					4,201,518	1,422,405

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 per share calculation because they were anti-dilutive:

	Six-month Period		Three-month Period
Reconciliation	2018	2017	2018	2017
Basic weighted average shares outstanding	287,391,614	288,948,734	287,140,426	288,655,020
Weighted shares assumed upon exercise of stock options	167,854	150,582	117,061	133,943
Diluted weighted average shares outstanding	287,559,468	289,099,316	287,257,487	288,788,963

Anti-Dilutive Options Excluded

	Six-month Period			Three-month Period
Summary of Anti-dilutive Options Excluded	2018		2017	2018		2017
Options to purchase shares of common stock	2,790,630		3,603,850	3,056,822		3,897,177
Weighted average exercise price of options	$	52.86	49.81	$	52.18	49.18