Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Compensation, Restricted Stock Units Award Activity

RSU activity for the six months ended June 30, 2015 is as follows:



	Number of		Weighted-Average Grant-Date
(in thousands, except weighted-average fair value prices)	Shares		Fair Value
Unvested RSUs outstanding at December 31, 2014	1,380		$	27.17
RSUs granted	939		$	35.33
RSUs vested	(627	)	$	24.70
RSUs forfeited	(50	)	$	30.22
Unvested RSUs outstanding at June 30, 2015	1,642		$	32.68

Schedule of Other Share-Based Compensation, Valuation Assumptions [Table Text Block]

The fair values of the 2015 and 2014 awards were estimated using Monte-Carlo simulation with the following weighted-average assumptions:



	For the Six Months Ended June 30,
	2015		2014

Expected dividend yield	—	%	—	%
Risk-free interest rate ⁽¹⁾	0.93	%	0.74	%
Expected volatility ⁽²⁾	24.01	%	27.88	%
Average total stockholder return ⁽²⁾	8.37	%	(0.90	)%


(1)	The risk-free interest rate for the periods within the contractual term of the PBRSUs is based on the U.S. Treasury yield curve in effect at the time of the grant.


(2)	The expected volatility and average total stockholder return is a measure of the amount by which a stock price has fluctuated or is expected to fluctuate based primarily on our and our peers' historical data.

Schedule of Other Share-based Compensation, Activity

PBRSU activity for the six months ended June 30, 2015 is as follows:



	Number of		Weighted-Average Grant-Date
(in thousands, except weighted-average fair value prices)	Shares		Fair Value
Unvested PBRSUs outstanding at December 31, 2014	903		$	22.19
PBRSUs granted	223		$	34.01
PBRSUs vested	(415	)	$	16.51
PBRSUs forfeited	(17	)	$	29.94
Unvested PBRSUs outstanding at June 30, 2015	694		$	29.21

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

The fair values of these stock options were estimated using the Black-Scholes valuation model with the following weighted-average assumptions:



	For the Six Months Ended
	June 30, 2014
Expected dividend yield	—	%
Risk-free interest rate ⁽¹⁾	1.74	%
Expected volatility ⁽²⁾	37.92	%
Expected life ⁽³⁾	5.5


(1)	The risk-free interest rate for the periods within the contractual term of the options is based on the U.S. Treasury yield curve in effect at the time of the grant.


(2)	The expected volatility is a measure of the amount by which a stock price has fluctuated or is expected to fluctuate based primarily on our and our peers' historical data.


(3)	The expected life is the period of time, on average, that participants are expected to hold their options before exercise based primarily on our historical data.

Schedule of Share-based Compensation, Stock Options, Activity

Option activity for the six months ended June 30, 2015 is as follows:



(in thousands, except weighted-average price)	Number of Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term	Aggregate Intrinsic Value
Options outstanding at December 31, 2014	2,562		$	22.32
Options exercised	(461	)	$	23.65
Options canceled	(13	)	$	28.66
Options outstanding at June 30, 2015	2,088		$	21.99	5.0	$	36,970
Options vested and expected to vest at June 30, 2015	2,076		$	21.94	5.0	$	36,847
Options exercisable at June 30, 2015	1,814		$	20.87	4.6	$	34,128

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan

The following table sets forth the stock-based compensation expense recognized for the three and six months ended June 30, 2015 and 2014.



	For the Three Months Ended				For the Six Months Ended
	June 30,				June 30,
(in thousands)	2015		2014		2015		2014
RSUs	$	6,819	$	5,010	$	12,833	$	10,429
PBRSUs	2,272		1,503		4,052		2,746
Stock options	474		1,116		1,037		2,221
Employee stock purchase plan	242		148		617		412
	$	9,807	$	7,777	$	18,539	$	15,808

The above includes $0.8 million and $0.6 million of stock-based compensation expense within cost of services in the accompanying condensed consolidated statements of operations for the three months ended June 30, 2015 and 2014, respectively, and $1.4 million and $1.0 million for the six months ended June 30, 2015 and 2014, respectively. It also includes less than $0.1 million for the three and six months ended June 30, 2014, respectively, of stock-based compensation expense reported within loss from discontinued operations in the accompanying condensed consolidated statements of operations.