Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of Stock Options Outstanding and Exercised Under Prior and Existing Stock Incentive Plans

The following is a summary of stock options outstanding and exercised under prior and existing stock incentive plans of the Company:

Year Ended December 31	Stock Options/Shares			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term		Aggregate Intrinsic Value (in millions)
2019
Number outstanding at beginning of period		9,115,010		$	34.52
Granted(a)		—			—
Exercised		(3,333,467	)		26.36
Cancelled(b)		(63,287	)		36.74
Number outstanding at end of period(c)		5,718,256		$	39.25		4.4	$	115
Exercisable at end of period		4,869,805		$	37.67		4.0	$	105
2018
Number outstanding at beginning of period		12,668,467		$	32.15
Granted(a)		—			—
Exercised		(3,443,494	)		25.41
Cancelled(b)		(109,963	)		46.72
Number outstanding at end of period(c)		9,115,010		$	34.52		4.3	$	102
Exercisable at end of period		7,372,036		$	31.61		3.5	$	104
2017
Number outstanding at beginning of period		17,059,241		$	29.95
Granted		1,066,188			54.97
Exercised		(5,389,741	)		29.58
Cancelled(b)		(67,221	)		43.31
Number outstanding at end of period(c)		12,668,467		$	32.15		4.5	$	272
Exercisable at end of period		9,647,937		$	27.87		3.3	$	248

(a) The Company did not grant any stock option awards during 2019 and 2018.

(b) Options cancelled include both non-vested (i.e., forfeitures) and vested options.

(c) Outstanding options include stock-based awards that may be forfeited in future periods. The impact of the estimated forfeitures is reflected in compensation expense.

Weighted-Average Estimated Fair Value of Stock Options Granted and Assumptions Utilized by Company for Newly Issued Grants

The following table includes the weighted-average estimated fair value of stock options granted and the assumptions utilized by the Company for newly issued grants for the year ended December 31, 2017:

Year Ended December 31	2017
Estimated fair value	$	14.66
Risk-free interest rates		2.0	%
Dividend yield		2.6	%
Stock volatility factor		.35
Expected life of options (in years)		5.5

Summary of Certain Stock Option Activity

The following summarizes certain stock option activity of the Company:

Year Ended December 31 (Dollars in Millions)	2019		2018		2017
Fair value of options vested	$	10	$	14	$	13
Intrinsic value of options exercised		95		97		127
Cash received from options exercised		88		87		159
Tax benefit realized from options exercised		24		24		49

Stock Options Outstanding Additional Information

Additional information regarding stock options outstanding as of December 31, 2019, is as follows:

	Outstanding Options						Exercisable Options
Range of Exercise Prices	Shares		Weighted- Average Remaining Contractual Life (Years)		Weighted- Average Exercise Price		Shares		Weighted- Average Exercise Price
$23.36—$25.00		236,661		.2	$	23.82		236,661	$	23.82
$25.01—$30.00		1,277,726		1.8		28.65		1,277,726		28.65
$30.01—$35.00		537,881		3.1		33.98		537,881		33.98
$35.01—$40.00		1,251,397		6.1		39.49		885,968		39.49
$40.01—$45.00		1,454,651		4.7		42.42		1,454,068		42.43
$45.01—$50.00		—		—		—		—		—
$50.01—$55.01		959,940		7.1		54.97		477,501		54.97
		5,718,256		4.4	$	39.25		4,869,805	$	37.67

Summary of Company's Restricted Shares of Stock and Unit Awards

A summary of the status of the Company’s restricted shares of stock and unit awards is presented below:

	2019					2018					2017
Year Ended December 31	Shares			Weighted- Average Grant- Date Fair Value		Shares			Weighted- Average Grant- Date Fair Value		Shares			Weighted- Average Grant- Date Fair Value
Outstanding at beginning of period		6,719,298		$	48.17		7,446,955		$	44.49		8,265,507		$	39.50
Granted		3,519,474			50.45		3,213,023			55.03		2,850,927			54.45
Vested		(3,270,778	)		48.69		(3,373,323	)		46.42		(3,295,376	)		40.66
Cancelled		(361,161	)		50.55		(567,357	)		49.07		(374,103	)		43.91
Outstanding at end of period		6,606,833		$	48.99		6,719,298		$	48.17		7,446,955		$	44.49