
15.	STOCK-BASED COMPENSATION

Under our 2011 Omnibus Stock Incentive Plan (the OSIP), various stock and stock-based awards may be granted to employees and non-employee directors. Awards available under the OSIP include options to purchase shares of common stock, performance awards that vest upon the achievement of an objective performance goal, stock appreciation rights, restricted stock that vests over a period determined by our compensation committee, and dividend equivalent rights (DERs). The OSIP was approved by our stockholders on April 28, 2011. As of December 31, 2014, 13,536,081 shares of our common stock remained available to be awarded under the OSIP.

We also maintain other stock-based compensation plans under which previously granted equity awards remain outstanding. No additional grants may be awarded under these plans.

The following table reflects activity related to our stock-based compensation arrangements (in millions):



	Year Ended December 31,
	2014		2013		2012
Stock-based compensation expense	$	60	$	64	$	58
Tax benefit recognized on stock-based compensation expense	21		22		20
Tax benefit realized for tax deductions resulting from exercises and vestings	64		66		45
Effect of tax deductions in excess of recognized stock-based compensation expense reported as a financing cash flow	47		47		27

Each of our stock-based compensation arrangements is discussed below.

Stock Options

Under the terms of our various stock-based compensation plans, the exercise price of options granted is not less than the fair market value of our common stock on the date of grant. Stock options become exercisable pursuant to the individual written agreements between the participants and us, usually in three equal annual installments beginning one year after the date of grant, with unexercised options generally expiring seven or ten years from the date of grant.

The fair value of stock options granted during 2014, 2013, and 2012 were estimated using the Monte Carlo simulation model, as these options contain both a service condition and a market condition in order to be exercised. The expected life of options granted is the period of time from the grant date to the date of expected exercise or other expected settlement. The expected life for each of the years in the table below was calculated using the safe harbor provisions of SEC Staff Accounting Bulletin No. 107 and No. 110 related to share‑based payments. Because the stock options granted in 2012 and later contain a market condition, historical exercise patterns did not provide a reasonable basis for estimating the expected life. Expected volatility is based on closing prices of our common stock for periods corresponding to the expected life of options granted. Expected dividend yield is based on annualized dividends at the date of grant. The risk-free interest rate used is the implied yield currently available from the U.S. Treasury zero‑coupon issues with a remaining term equal to the expected life of the options at the grant date.

A summary of the weighted-average assumptions used in our fair value measurements is presented in the table below.



	Year Ended December 31,
	2014		2013		2012
Expected life in years	6.0		6.0		6.0
Expected volatility	43.21	%	49.63	%	49.11	%
Expected dividend yield	2.27	%	2.27	%	2.39	%
Risk-free interest rate	1.74	%	1.77	%	0.85	%

A summary of the status of our stock option awards is presented in the table below.



	Number of Stock Options		Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
					(in years)	(in millions)
Outstanding as of January 1, 2014	8,558,093		$	27.88
Granted	126,095		48.57
Exercised	(2,564,125	)	18.64
Expired	(1,449,986	)	66.67
Forfeited	(856	)	17.68
Outstanding as of December 31, 2014	4,669,221		21.48		4.5	$	131

Exercisable as of December 31, 2014	4,315,414		19.99		4.2	127

The following table reflects activity related to our stock options granted (in millions, except per share data):



	Year Ended December 31,
	2014		2013		2012
Weighted average grant-date fair value price per share	$	17.31	$	15.83	$	10.98
Intrinsic value of stock options exercised	85		101		78
Cash received from stock option exercises	47		59		59

As of December 31, 2014, there was $1 million of unrecognized compensation cost related to outstanding unvested stock option awards, which is expected to be recognized over a weighted-average period of approximately two years.

Restricted Stock

Restricted stock is granted to employees and non-employee directors. Restricted stock granted to employees vests in accordance with individual written agreements between the participants and us, usually in equal annual installments over a period of three years beginning one year after the date of grant. Restricted stock granted to our non-employee directors generally vests in three years following the date of grant. A summary of the status of our restricted stock awards is presented in the table below.



	Number of Shares		Weighted- Average Grant-Date Fair Value Per Share
Nonvested shares as of January 1, 2014	2,205,314		$	32.23
Granted	969,671		49.40
Vested	(1,402,753	)	31.90
Forfeited	(14,082	)	32.56
Nonvested shares as of December 31, 2014	1,758,150		41.96

As of December 31, 2014, there was $45 million of unrecognized compensation cost related to outstanding unvested restricted stock awards, which is expected to be recognized over a weighted-average period of approximately two years. The total fair value of restricted stock that vested during the years ended December 31, 2014, 2013, and 2012 was $60 million, $74 million, and $47 million, respectively.

Performance Awards

Performance awards are issued to certain of our key employees and represent rights to receive shares of our common stock upon the achievement by us of an objective performance measure. The objective performance measure is our total shareholder return, which is ranked among the total shareholder returns of a defined peer group of companies. Our ranking determines the rate at which the performance awards convert into our common shares. Conversion rates can range from zero to 200 percent.

Performance awards vest in equal one-third increments (tranches) on an annual basis. Our compensation committee establishes the peer group of companies for each tranche of awards at the beginning of the one year vesting period for that tranche. Therefore, performance awards are not considered to be granted for accounting purposes until our compensation committee establishes the peer group of companies for each tranche of awards. The fair value of each tranche of awards is determined at the time the awards are considered to be granted and is based on the expected conversion rate for those awards and the fair value per share. The fair value per share for awards granted during 2014 is equal to the market price of our common stock on the grant date as these grants include DERs. The fair value per share for awards granted prior to 2014 was equal to the market price of our common stock on the grant date reduced by expected dividends over that tranche’s vesting period as these grants did not include DERs.

A summary of the status of our performance awards considered granted is presented below.



	Nonvested Awards		Vested Awards
Awards outstanding as of January 1, 2014	947,165		—
Granted	225,829		—
Vested	(534,028	)	534,028
Converted	—		(534,028	)
Forfeited	(24,576	)	—
Awards outstanding as of December 31, 2014	614,390		—

There were three tranches of performance awards granted during the year ended December 31, 2014 as follows:



	Awards Granted	Expected Conversion Rate	Fair Value Per Share
Third tranche of 2012 awards	99,023	100%	$	47.47
Second tranche of 2013 awards	76,232	100%	47.47
First tranche of 2014 awards	50,574	100%	48.57
Total	225,829

As of December 31, 2014, there was $11 million of unrecognized compensation cost related to outstanding unvested performance awards, which will be recognized during 2015. The total fair value of performance awards that vested during the years ended December 31, 2014, 2013, and 2012 was $15 million, $12 million, and $3 million, respectively.

Performance awards converted during the year ended December 31, 2014 were as follows:



	Vested Awards Converted	Actual Conversion Rate	Number of Shares Issued
2010 awards	201,422	100%	201,422
2011 awards	227,571	200%	455,142
2012 awards	102,855	200%	205,710
2013 awards	2,180	200%	4,360
Total	534,028		866,634