Common Stock (Tables)

12 Months Ended

Dec. 31, 2017

The following summarizes options activity:


	Years Ended December 31,
	2017					2016					2015
	Number			Average		Number			Average		Number			Average
	of			Exercise		of			Exercise		of			Exercise
	Shares			Price		Shares			Price		Shares			Price
Shares under option at beginning of year		17,439,060		$	54.08		15,430,307		$	59.50		10,881,133		$	61.22
Granted		6,961,041			36.51		3,672,411			28.26		5,746,153			54.74
Forfeited		(1,482,531	)		55.22		(1,517,065	)		49.95		(886,356	)		62.73
Exercised		(445,523	)		29.83		(146,593	)		28.53		(310,623	)		22.56

Shares under option at end of year		22,472,047		$	48.99		17,439,060		$	54.08		15,430,307		$	59.50

Exercisable at end of year		14,309,944		$	55.00		9,828,897		$	61.56		7,498,414		$	60.30

Summary of Stock Option Outstanding Information

The following summarizes information about stock options outstanding at December 31, 2017:


	Weighted-Avg		Options Outstanding				Options Exercisable
	Remaining				Weighted-Avg				Weighted-Avg
Range of Exercise Price	Contractual Life		Shares		Exercise Price		Shares		Exercise Price
$23.94 - $55.00		7.55		15,797,683	$	40.25		7,635,580	$	42.19
$55.01 - $70.00		5.09		4,301,953		66.20		4,301,953		66.20
$70.01 - $77.99		3.59		2,372,411		75.94		2,372,411		75.94

Total		6.66		22,472,047	$	48.99		14,309,944	$	55.00

Assumption Used in Determination of Fair Value of Share Based Payment Awards

The use of the Black Scholes model requires the use of actual employee exercise activity data and the use of a number of complex assumptions including expected volatility, risk-free interest rate, expected dividends and expected term.


	Years Ended December 31,
	2017			2016			2015
Valuation Assumptions:
Expected volatility		36.1	%		48.6	%		49.1	%
Risk-free interest rate		2.2	%		1.2	%		1.5	%
Expected dividend yield		0.6	%		6.5	%		3.4	%
Expected term (in years)		3.0			3.0			3.0

Summary of Information and Changes in Stock Options with Regard to Stock Option Plans

The following summary presents information regarding outstanding options at December 31, 2017 and changes during 2017 with regard to options under all stock option plans:


						Weighted
				Weighted- Average		Remaining Contractual
	Shares			Exercise Price		Term (years)		Aggregate Intrinsic Value
Outstanding at December 31, 2016		17,439,060		$	54.08		5.42	$	6,700,856
Granted		6,961,041		$	36.51
Forfeited		(1,482,531	)	$	55.22
Exercised		(445,523	)	$	29.83

Outstanding at December 31, 2017		22,472,047		$	48.99		6.66	$	34,186,368

Exercisable at December 31, 2017		14,309,944		$	55.00		5.70	$	15,557,324

Summary of Information Regarding Outstanding SARs

The following summary presents information regarding outstanding SARs:


	Year Ended December 31,
	2017					2016
	Number			Average		Number			Average
	of			Exercise		of			Exercise
	Shares			Price		Shares			Price
Shares under SARs at beginning of year		4,341,740		$	28.32		—		$	—
Granted		14,400			38.86		4,618,400			28.32
Forfeited		(283,822	)		28.35		(276,660	)		28.24
Exercised		(2,578,629	)		34.72		—			—

Shares under SARs at end of year		1,493,689		$	28.41		4,341,740		$	28.32

Exercisable at end of year		75,102		$	28.33		—		$	—

Summary of Information Regarding Outstanding Restricted Shares

The following summary presents information regarding outstanding restricted shares:


	Years Ended December 31,
	2017					2016					2015
				Weighted-					Weighted-					Weighted-
	Number			Average		Number			Average		Number			Average
	of			Grant Date		of			Grant Date		of			Grant Date
	Units			Fair Value		Units			Fair Value		Units			Fair Value
Nonvested at beginning of year		4,563,983		$	41.10		1,969,250		$	61.53		1,569,141		$	73.73
Granted		1,738,589			38.74		3,384,325			31.59		954,075			53.27
Vested		(1,018,206	)		34.84		(565,202	)		29.32		(405,327	)		54.30
Forfeited		(394,688	)		55.22		(224,390	)		49.95		(148,639	)		62.73

Nonvested at end of year		4,889,678		$	37.04		4,563,983		$	41.10		1,969,250		$	61.53