Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2014

Presented below is a summary of our stock option activity for the six months ended June 30, 2014 (shares in thousands):

	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Terms	Aggregate Intrinsic Value
Outstanding at December 31, 2013	4,273		$	17.53	4.86	27,099
Granted	58		$	19.96
Exercised	(316	)	$	9.90
Forfeited	(207	)	$	23.50
Expired	(117	)	$	22.69
Outstanding at June 30, 2014	3,691		$	17.72	4.50	$	18,094
Expected to vest at June 30, 2014	1,743		$	22.69	6.03	$	896
Exercisable at June 30, 2014	1,907		$	13.06	3.06	$	17,172

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

	Six months ended June 30,
	2014	2013
Expected dividend yield	—	—
Risk-free interest rate	1.50%	0.67%
Expected volatility	37.27%	40.05%
Expected life	4.81 years	4.47 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 six months ended June 30, 2014 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		Aggregate Intrinsic Value
Outstanding balance at December 31, 2013	636		$	25.50	$	14,429
Granted	247		$	20.22
Vesting of restricted stock units, net of shares withheld for taxes	(52	)	$	25.56
Shares withheld for taxes	(25	)	$	25.56
Forfeitures	(117	)	$	24.96
Outstanding balance at June 30, 2014	689		$	23.71	$	14,057

Summary of status of restricted stock awards

A summary of the status of our restricted stock awards at June 30, 2014 and of changes in restricted stock awards outstanding under the 2006 Stock Plan for the six months ended June 30, 2014 is as follows (in thousands, except for weighted average grant date fair value):

	Shares		Weighted Average Grant Date Fair Value per Share		Aggregate Intrinsic Value
Outstanding balance at December 31, 2013	82		$	10.42	$	1,851
Granted	—		—
Vesting of restricted stock awards	(54	)	$	10.42
Shares withheld for payment of taxes upon vesting of restricted stock awards	(28	)	$	10.42
Forfeitures	—		—
Outstanding balance at June 30, 2014	—				$	—