STOCKHOLDERS’ EQUITY

Equity-Based Incentive Plans

Our 2009 Equity Incentive Plan (the 2009 Plan) provides for the grant of stock awards, including stock options, RSUs, RSAs, and other stock awards. Shares available for grant as of March 31, 2019 were approximately 14 million.

Restricted Stock Units (RSUs) and Restricted Stock Awards (RSAs)

Time-based RSUs and RSAs generally vest over a four-year term. Performance-based RSUs and RSAs are subject to vesting requirements based on certain financial performance metrics as defined in the grant notice. Actual number of shares earned may range from 0% to 200% of the target award. Awards granted in 2019 and 2018 are based on a single-year performance period subject to subsequent multi-year vesting with 50% of the shares earned vesting in one year after the performance period and the remaining shares in the year after.

The following table summarizes RSU and RSA activity under our equity-based plans for the three months ended March 31, 2019:



	RSUs				RSAs
	Number of Units		Weighted-Average Grant Date Fair Value		Number of Units		Weighted-Average Grant Date Fair Value
Nonvested at December 31, 2018	1,737,554		$	32.83	346,792		$	49.13
Granted	669,415		60.43		—		—
Vested	(297,822	)	28.83		(13,565	)	50.48
Forfeited	(14,908	)	42.79		(11,103	)	49.35
Nonvested at March 31, 2019	2,094,239		$	42.15	322,124		$	49.20

Equity-Based Compensation

Stock-based compensation expense is measured based on the fair value of the stock award on the grant date and recognized over the requisite service period for each separately vesting portion of the stock award. Stock-based compensation expense and other disclosures for stock-based awards made to our employees pursuant to the equity plans was as follows:



	Three Months Ended March 31,
(in millions)	2019		2018
Cost of providing services	$	2	$	2
Sales and marketing	1		2
General and administrative	5		4
Systems development and programming costs	1		1
Total stock-based compensation expense	$	9	$	9
Income tax benefit related to stock-based compensation expense	$	3	$	2
Tax benefit realized from stock options exercise and similar awards	$	2	$	6

Stock Repurchases

In February 2019, our board of directors authorized a $300 million incremental increase to our ongoing stock repurchase program initiated in May 2014. During the three months ended March 31, 2019, we repurchased 782,909 shares of common stock for approximately $38 million. As of March 31, 2019, approximately $337 million remained available for further repurchases of our common stock under all authorizations from our board of directors under this program.