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Stock-Based Compensation
 3 Months Ended
Mar. 31, 2013
Share-based Compensation [Abstract]  
Stock-Based Compensation
Stock-based Compensation
As of March 31, 2013, the Company had four equity plans. Additional information regarding these plans is disclosed in the Annual Report.
Stock-based compensation expense, net of estimated forfeitures, is recognized on a straight-line basis over the vesting period for each stock option.
The fair value of each stock option on the date of grant is estimated using the Black-Scholes-Merton option valuation model.
The following weighted-average assumptions were used for the valuation of stock options granted during the periods presented:

 
 
Quarter ended
 
 
March 31,
2013
 
April 1,
2012
Expected term
 
4.5 years

 
4.3 years

Expected volatility
 
57.1
%
 
59.2
%
Expected dividend yield
 
0.0
%
 
0.0
%
Risk-free interest rate
 
0.9
%
 
0.7
%
Estimated weighted-average fair value per stock option granted
 
$
14.61

 
$
16.03


The assumptions used to calculate the fair value of stock options granted are evaluated and revised, if necessary, to reflect market conditions and the Company’s experience.
A summary of stock option activity for the quarter ended March 31, 2013 is as follows:
 
Options
(in thousands)
 
Weighted
Average
Exercise Price
Weighted
Average
Remaining
Contractual
Term (in years)
Aggregate
Intrinsic Value
(in thousands)
Balance, December 31, 2012
2,199

 
$
38.55

 
 
Granted
109

 
31.42

 
 
Exercised
(10
)
 
22.37

 
 
Canceled
(50
)
 
33.12

 
 
Balance, March 31, 2013
2,248

 
$
38.39

5.56
$
6,297

Vested and expected to vest at March 31, 2013
2,158

 
$
38.51

5.43
$
6,138

Exercisable, March 31, 2013
1,621

 
$
39.07

4.38
$
5,288



A summary of restricted stock unit (RSU) activity for the quarter ended March 31, 2013 is as follows:
 
RSUs
(in thousands)
 
Weighted
Average Grant
Date Fair Value
Weighted
Average
Remaining
Contractual
Term (in years)
Aggregate
Intrinsic Value
(in thousands)
Balance, December 31, 2012
3

 
$
29.67

 
 
Granted
77

 
31.31

 
 
Vested
(2
)
 
31.94

 
 
Canceled
—

 
—

 
 
Balance, March 31, 2013
78

 
$
31.32

2.23
$
2,717

Vested and expected to vest at March 31, 2013
63

 
$
31.32

2.02
$
2,174



The aggregate intrinsic value in the tables above are before applicable income taxes and represent the amount recipients would have received if all stock options had been exercised or RSUs had been released on the last business day of the period indicated, based on the Company’s closing stock price on such date.
The total intrinsic value of stock options exercised during the quarter ended March 31, 2013 was $0.1 million. During the quarter ended March 31, 2013, the total fair value of stock options vested was $1.9 million. As of March 31, 2013, the Company had total unrecognized compensation costs related to unvested stock options and RSUs of $10.6 million, before income taxes. The Company expects to recognize this cost over a weighted average period of 2.9 years for the options and 3.9 years for the RSUs.