Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2018

Stock Option Activity Under Equity-Based Plans

The following table summarizes stock option activity under our 2009 Plan for the six months ended June 30, 2018:



	Number of Shares
Balance at December 31, 2017	1,296,863
Exercised	(469,894	)
Forfeited	(17,846	)
Balance at June 30, 2018	809,123
Exercisable at June 30, 2018	766,294

Restricted Stock Unit and Restricted Stock Award Activity Under Equity-Based Plans

The following tables summarize RSU, performance-based restricted stock unit (PSU), RSA, and PRSA activity under our 2009 Plan for the six months ended June 30, 2018:



	RSUs				PSUs
	Number of Units		Weighted-Average Grant Date Fair Value		Number of Units		Weighted-Average Grant Date Fair Value
Nonvested at December 31, 2017	2,249,661		$	24.83	453,674		$	30.72
Granted	585,484		47.36		23,842		47.61
Vested	(545,292	)	25.09		(82,066	)	33.51
Forfeited	(200,961	)	26.76		(65,557	)	31.60
Nonvested at June 30, 2018	2,088,892		$	30.89	329,893		$	31.08



	RSAs				PRSAs
	Number of Units		Weighted-Average Grant Date Fair Value		Number of Units	Weighted-Average Grant Date Fair Value
Nonvested at December 31, 2017	—		$	—	—	$	—
Granted	116,559		49.12		256,224	48.98
Vested	(4,560	)	47.61		—	—
Nonvested at June 30, 2018	111,999		$	49.81	256,224	$	48.98

Performance Stock Unit and Performance Stock Award Activity Under Equity-Based Plans

The following tables summarize RSU, performance-based restricted stock unit (PSU), RSA, and PRSA activity under our 2009 Plan for the six months ended June 30, 2018:



	RSUs				PSUs
	Number of Units		Weighted-Average Grant Date Fair Value		Number of Units		Weighted-Average Grant Date Fair Value
Nonvested at December 31, 2017	2,249,661		$	24.83	453,674		$	30.72
Granted	585,484		47.36		23,842		47.61
Vested	(545,292	)	25.09		(82,066	)	33.51
Forfeited	(200,961	)	26.76		(65,557	)	31.60
Nonvested at June 30, 2018	2,088,892		$	30.89	329,893		$	31.08



	RSAs				PRSAs
	Number of Units		Weighted-Average Grant Date Fair Value		Number of Units	Weighted-Average Grant Date Fair Value
Nonvested at December 31, 2017	—		$	—	—	$	—
Granted	116,559		49.12		256,224	48.98
Vested	(4,560	)	47.61		—	—
Nonvested at June 30, 2018	111,999		$	49.81	256,224	$	48.98

Stock-based Compensation Expense

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 June 30,				Six Months Ended June 30,
(in millions)	2018		2017		2018		2017
Cost of providing services	$	2	$	2	$	4	$	4
Sales and marketing	2		2		4		3
General and administrative	5		3		9		5
Systems development and programming costs	1		1		2		2
Total stock-based compensation expense	$	10	$	8	$	19	$	14
Income tax benefit related to stock-based compensation expense	$	3	$	3	$	5	$	5
Tax benefit realized from stock options exercised and similar awards	$	7	$	10	$	13	$	16