Stock-Based Compensation

The following table reflects the stock-based compensation expense and the related deferred income tax benefit recognized in income for the three months ended March 31:



(Millions)	2014		2013
Stock options	$	0.3	$	0.4
Performance stock rights	0.5		2.2
Restricted share units	3.1		2.8
Nonemployee director deferred stock units	0.2		0.3
Total stock-based compensation expense	$	4.1	$	5.7
Deferred income tax benefit	$	1.6	$	2.3

No stock-based compensation cost was capitalized during the three months ended March 31, 2014, and 2013.

Stock Options

The fair value of stock option awards granted is estimated using a binomial lattice model. The expected term of option awards is derived from the output of the binomial lattice model and represents the period of time that options are expected to be outstanding. The risk-free interest rate is based on the United States Treasury yield curve. The expected dividend yield incorporates the current and historical dividend rate. The expected stock price volatility is estimated using the 10-year historical volatility of our stock price. The following table shows the assumptions incorporated into the valuation model:



		February 2014 Grant
Expected term		8 years
Risk-free interest rate		0.12% – 2.88%
Expected dividend yield		5.28%
Expected volatility		18%

The weighted-average fair value per stock option granted during the three months ended March 31, 2014, and 2013, was $6.70 and $6.03, respectively.

A summary of stock option activity for the three months ended March 31, 2014, and information related to outstanding and exercisable stock options at March 31, 2014, is presented below:



	Stock Options		Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Life (in Years)	Aggregate Intrinsic Value (Millions)
Outstanding at December 31, 2013	1,550,374		$	50.93
Granted	264,332		55.23
Exercised	(11,504	)	45.45
Outstanding at March 31, 2014	1,803,202		$	51.60	6.6	$	14.5
Exercisable at March 31, 2014	1,114,027		$	49.75	5.1	$	11.0

The aggregate intrinsic value for outstanding and exercisable options in the above table represents the total pre-tax intrinsic value that would have been received by the option holders had they all exercised their options on March 31, 2014. This is calculated as the difference between our closing stock price on March 31, 2014, and the option exercise price, multiplied by the number of in-the-money stock options. The intrinsic value of options exercised was not significant during the three months ended March 31, 2014, and was $1.9 million during the three months ended March 31, 2013. The actual tax benefit realized for the tax deductions from these option exercises was not significant during the three months ended March 31, 2014, and 2013.

As of March 31, 2014, $2.5 million of compensation cost related to unvested and outstanding stock options was expected to be recognized over a weighted-average period of 2.0 years.

Performance Stock Rights

The fair values of performance stock rights are estimated using a Monte Carlo valuation model. The risk-free interest rate is based on the United States Treasury yield curve. The expected dividend yield incorporates the current and historical dividend rate. The expected stock price volatility is estimated using two to three years of historical data. The table below reflects the assumptions used in the valuation of the outstanding grants at March 31:



		2014
Risk-free interest rate		0.34% – 0.57%
Expected dividend yield		5.28% – 5.33%
Expected volatility		15% – 22%

A summary of the activity for the three months ended March 31, 2014, related to performance stock rights accounted for as equity awards is presented below:



	Performance Stock Rights		Weighted-Average Fair Value *
Outstanding at December 31, 2013	85,749		$	46.62
Granted	21,146		44.28
Adjustment for shares not distributed	(45,748	)	43.29
Outstanding at March 31, 2014	61,147		$	48.31


*	Reflects the weighted-average fair value used to measure equity awards. Equity awards are measured using the grant date fair value or the fair value on the modification date.

The weighted-average grant date fair value of performance stock rights awarded during the three months ended March 31, 2014, and 2013, was $44.28 and $48.50, per performance stock right, respectively.

A summary of the activity for the three months ended March 31, 2014, related to performance stock rights accounted for as liability awards is presented below:



	Performance Stock Rights
Outstanding at December 31, 2013	198,904
Granted	84,529
Adjustment for shares not distributed	(39,001	)
Outstanding at March 31, 2014	244,432

The weighted-average fair value of all outstanding performance stock rights accounted for as liability awards as of March 31, 2014, was $38.73 per performance stock right.

No shares of common stock were distributed for performance stock rights during the three months ended March 31, 2014, because the performance percentage was below the threshold payout level for those rights that were eligible for distribution. The total intrinsic value of shares distributed during the three months ended March 31, 2013, was $8.8 million. The actual tax benefit realized for the tax deductions from the distribution of shares during the three months ended March 31, 2013, was $3.6 million.

As of March 31, 2014, $5.2 million of compensation cost related to unvested and outstanding performance stock rights (equity and liability awards) was expected to be recognized over a weighted-average period of 1.6 years.

Restricted Share Units

A summary of the activity related to all restricted share unit awards (equity and liability awards) for the three months ended March 31, 2014, is presented below:



	Restricted Share Unit Awards		Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2013	511,301		$	52.24
Granted	214,953		55.23
Dividend equivalents	6,169		54.45
Vested and released	(204,322	)	49.73
Forfeited	(781	)	54.42
Outstanding at March 31, 2014	527,320		$	54.45

The weighted-average grant date fair value of restricted share units awarded during the three months ended March 31, 2014, and 2013, was $55.23 and $56.00 per unit, respectively.

The total intrinsic value of restricted share unit awards vested and released during the three months ended March 31, 2014, and 2013, was $11.1 million and $11.4 million, respectively. The actual tax benefit realized for the tax deductions from the vesting and release of restricted share units during the three months ended March 31, 2014, and 2013, was $4.4 million and $4.6 million respectively.

As of March 31, 2014, $18.7 million of compensation cost related to unvested and outstanding restricted share units was expected to be recognized over a weighted-average period of 2.5 years.

Nonemployee Directors Deferred Stock Units

Each nonemployee director is granted deferred stock units (DSUs), typically in January of each year. These awards generally vest over one year; therefore, the expense is recognized pro-rata over the year in which the grant occurs. The number of DSUs granted is calculated by dividing a set dollar amount by our closing common stock price on December 31 of the prior year. Nonemployee directors also receive forfeitable dividend equivalents in the form of additional DSU's.