Stock Plans (Tables)

12 Months Ended

Dec. 31, 2015

Summary of Stock Option and RSA Activity

A summary of stock option and RSA activity as of December 31, 2015, and changes during the year is presented below:

	Stock Options			RSAs
(Shares in thousands)	Shares	Weighted-Average Exercise Price		Shares	Weighted-AverageGrantPrice
Outstanding as of December 31, 2014^(a)	13,416	$	44.88	7,874	$	64.48
Granted	301		83.30	3,069		81.99
Exercised/vested	(2,921)		49.96	(3,003)		55.17
Forfeited	(10)		49.22	(507)		75.99
Expired	34		50.04	―		―
Outstanding as of December 31, 2015	10,820		44.60	7,433	$	74.67
Options vested and expected to vest as of December 31, 2015	10,820		44.60	―		―
Options exercisable as of December 31, 2015	9,809	$	41.78	―		―

Outstanding as of December 31, 2014, includes CEO market-based stock options of 687,000 that were previously disclosed separately.

Weighted-average remaining contractual life and aggregate intrinsic value of the Company's stock options outstanding, exerciseable, and vested and expected to vest

The weighted-average remaining contractual life and the aggregate intrinsic value (the amount by which the fair value of the Company’s stock exceeds the exercise price of the option) of the stock options outstanding, exercisable, vested, and expected to vest as of December 31, 2015, are as follows:

	Outstanding		Exercisable		Vested and Expected to Vest
Weighted-average remaining contractual life (in years)		3.4		2.9		3.4
Aggregate intrinsic value (millions)	$	279	$	273	$	279

Weighted Average Assumptions Used

The fair value of each option is estimated on the date of grant using a Black-Scholes-Merton option-pricing model. The following weighted-average assumptions were used for options granted in 2015, 2014 and 2013, the majority of which were options granted in the beginning of each year:

	2015			2014			2013
Dividend yield		1.1	%		1.1	%		1.4	%
Expected volatility^(a)		37	%		38	%		39	%
Risk-free interest rate		1.7	%		2.2	%		1.3	%
Expected life of stock option (in years)^(b)		6.7			6.7			6.3
Weighted-average fair value per option	$	29.20		$	32.36		$	21.11

The expected volatility is based on both weighted historical and implied volatilities of the Company’s common stock price.
In 2015, 2014 and 2013, the expected life of stock options was determined using both historical data and expectations of option exercise behavior.

Summary of Stock Plan Expenses

The components of the Company’s total stock-based compensation expense (net of forfeitures) for the years ended December 31, are as follows:

(Millions)	2015		2014		2013
Restricted stock awards^(a)	$	190	$	193	$	208
Stock options^(a)		12		13		23
Liability-based awards		32		84		119
Total stock-based compensation expense ^(b)	$	234	$	290	$	350

As of December 31, 2015, the total unrecognized compensation cost related to unvested RSAs and options of $214 million and $3 million, respectively, will be recognized ratably over the weighted-average remaining vesting period of 2.1 years and 1.2 years, respectively.
The total income tax benefit recognized in the Consolidated Statements of Income for stock-based compensation arrangements for the years ended December 31, 2015, 2014 and 2013 was $83 million, $104 million and $127 million, respectively.