SHARE-BASED AWARDS AND OPTIONS

The following table summarizes share-based compensation expense and the related income tax benefit recognized for our share-based awards and stock options:



	Three Months Ended
	March 31, 2018		March 31, 2017

	(in thousands)

Share-based compensation expense	$	14,898	$	8,816
Income tax benefit	$	3,285	$	3,065

Share-Based Awards

The following table summarizes the changes in unvested restricted stock and performance awards for the three months ended March 31, 2018:



	Shares		Weighted-Average Grant-Date Fair Value
	(in thousands)

Unvested at December 31, 2017	1,226			$78.29
Granted	367		114.68
Vested	(168	)	77.15
Forfeited	(16	)	82.91
Unvested at March 31, 2018	1,409			$87.84

The total fair value of restricted stock and performance awards vested during the three months ended March 31, 2018 and March 31, 2017 was $13.0 million and $0.1 million, respectively.

For restricted stock and performance awards, we recognized compensation expense of $13.8 million and $8.0 million during the three months ended March 31, 2018 and March 31, 2017, respectively. As of March 31, 2018, there was $82.6 million of unrecognized compensation expense related to unvested restricted stock and performance awards that we expect to recognize over a weighted-average period of 2.2 years. Our restricted stock and performance award plans provide for accelerated vesting under certain conditions.

Stock Options

The following summarizes changes in stock option activity for the three months ended March 31, 2018:



	Options		Weighted-Average Exercise Price	Weighted-Average Remaining Contractual Term	Aggregate Intrinsic Value
	(in thousands)			(years)	(in millions)

Outstanding at December 31, 2017	723		$47.79	6.4	$37.9
Granted	103		114.7
Exercised	(23	)	21.89
Outstanding at March 31, 2018	803		$57.11	6.8	$44.0

Options vested and exercisable at March 31, 2018	520		$40.66	5.6	$36.8

We recognized compensation expense for stock options of $0.7 million and $0.6 million during the three months ended March 31, 2018 and March 31, 2017, respectively. The aggregate intrinsic value of stock options exercised during the three months ended March 31, 2018 and March 31, 2017 was $2.1 million and $2.8 million, respectively. As of March 31, 2018, we had $6.3 million of unrecognized compensation expense related to unvested stock options that we expect to recognize over a weighted-average period of 2.4 years.

The weighted-average grant-date fair value of each stock option granted during the three months ended March 31, 2018 and March 31, 2017 was $35.09 and $23.68, respectively. Fair value was estimated on the date of grant using the Black-Scholes valuation model with the following weighted-average assumptions:



	Three Months Ended
	March 31, 2018	March 31, 2017
Risk-free interest rate	2.60%	1.99%
Expected volatility	29%	30%
Dividend yield	0.04%	0.06%
Expected term (years)	5	5

The risk-free interest rate is based on the yield of a zero coupon U.S. Treasury security with a maturity equal to the expected life of the option from the date of the grant. Our assumption on expected volatility is based on our historical volatility. The dividend yield assumption is calculated using our average stock price over the preceding year and the annualized amount of our most current quarterly dividend per share. We based our assumptions on the expected term of the options on our analysis of the historical exercise patterns of the options and our assumption on the future exercise pattern of options.