XML 34 R29.htm IDEA: XBRL DOCUMENT v2.4.0.8
Stock-Based Compensation (Tables)
 3 Months Ended
Mar. 31, 2014
Summary of Activity Under Stock Option Plans
A summary of the activity under our stock option plans as of March 31, 2014 and changes during the three month period then ended, is presented below:

 
Options Outstanding
 
Weighted- Average Exercise Price Per Share
 
Weighted-Average Remaining Contractual Life in Years
 
Aggregate Intrinsic Value
Options outstanding at December 31, 2013
893,139

 
$
43.23

 
3.9
 
$
16,403,816

Options granted
—

 
—

 
 
 
 

Options exercised
(235,883
)
 
45.45

 
 
 
 

Options forfeited
(750
)
 
40.70

 
 
 
 

Options outstanding at March 31, 2014
656,506

 
42.44

 
4.1
 
13,184,080

Options exercisable at March 31, 2014
568,073

 
41.97

 
3.6
 
11,670,746

Options vested or expected to vest at March 31, 2014*
654,581

 
42.43

 
4.1
 
13,138,680

* In addition to the vested options, we expect a portion of the unvested options to vest at some point in the future.  Options expected to vest are calculated by applying an estimated forfeiture rate to the unvested options.
Assumptions Used in Calculation of Fair Value
Below are the assumptions used in the Monte Carlo calculation:
 
March 31, 2014
 
March 31, 2013
Expected volatility
33.7%
 
37.1%
Expected term (in years)
3.0
 
3.0
Risk-free interest rate
0.67%
 
0.40%
Expected dividend yield
—
 
—
Performance-Based Restricted Stock [Member]
  
Restricted Stock Activities
 
Performance-Based Restricted Stock Awards
Non-vested awards outstanding at December 31, 2013
71,175

Awards granted
47,200

Stock issued
(12,503
)
Awards forfeited
2,760

Non-vested awards outstanding at March 31, 2014
108,632
Time Based Restricted Stock [Member]
  
Restricted Stock Activities
 
Time-Based Restricted Stock Awards
Non-vested awards outstanding at December 31, 2013
231,026

Awards granted
62,050

Stock issued
(20,952
)
Awards forfeited
(1,755
)
Non-vested awards outstanding at March 31, 2014
270,369
Deferred Stock Units [Member]
  
Restricted Stock Activities
 
Deferred Stock
Units
Awards outstanding at December 31, 2013
31,550

Awards granted
—

Stock issued
—

Awards outstanding at March 31, 2014
31,550