Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2015

Stock-Based Compensation

Summary of stock option activity

Presented below is a summary of our stock option activity for the three months ended March 31, 2015 (in thousands, except for weighted average exercise price and weighted average remaining contractual terms):

	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Terms	Aggregate Intrinsic Value
Outstanding at December 31, 2014	4,101		$	18.72
Granted	1,088		16.77
Exercised	(443	)	7.40
Forfeited	(295	)	23.03
Expired	(25	)	24.48
Outstanding at March 31, 2015	4,426		19.06		5.12	$	5,959
Expected to vest at March 31, 2015	2,499		19.78		6.36	4
Exercisable at March 31, 2015	1,871		$	18.06	3.42	$	5,955

Schedule of weighted -average assumptions used for estimating fair value of each stock option grant on the date of grant

	Three months ended March 31,
	2015	2014
Expected dividend yield	—	—
Risk-free interest rate	1.44%	1.65%
Expected volatility	38.29%	37.08%
Expected life	4.88 years	4.81 years

Summary of status of restricted stock units

A summary of the status of our restricted stock units and of changes in restricted stock units outstanding under the 2006 Stock Plan for the three months ended March 31, 2015 is as follows (in thousands, except for weighted average grant date fair value per unit):

	Number of Units		Weighted Average Grant Date Fair Value per Unit
Outstanding balance at December 31, 2014	910		$	22.84
Granted	589		16.76
Vesting of restricted stock units, net of shares withheld for taxes	(88	)	24.03
Shares withheld for taxes	(35	)	24.03
Forfeitures	(83	)	24.96
Outstanding balance at March 31, 2015	1,293		$	19.82