Stock-Based Compensation (Tables)
 6 Months Ended
Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Schedule of fair value assumptions
The Black-Scholes option-pricing model was used to estimate the fair value of the stock options issued in each period at the grant date. Below is a summary of options granted and the assumptions utilized to derive fair value of the stock options under the Black-Scholes option-pricing model:
 
Six Months Ended June 30,
 
2014
 
2013
Total stock options granted
427,463

 
365,080

Volatility
38.4-39.2%

 
45.4
%
Risk-free interest rate
1.54-1.73%

 
0.81
%
Expected life (in years)
4.5

 
4.5

Dividend yield
—

 
—

Weighted-average grant date fair value
$
15.48

 
$
21.44
Schedule of stock option activity
The table below summarizes the stock options outstanding as of June 30, 2014 under both plans.

 
 
Options Outstanding
 
Weighted Average Exercise Price
 
Unrecognized Compensation Cost
 
Weighted Average Period
 
 
 
 
 
 
(in thousands)
 
 
LTIP
 
1,363,784

 
$
35.92

 
$
10,644

 
2.75
Assumed Plans
 
148,090

 
$
47.05

 
$
2,019

 
3.47
Schedule of restricted stock units activity
The table below summarizes the number of time-based and performance-based RSUs that were granted and outstanding under both plans for the six months ended June 30, 2014:
 
LTIP Plan
 
Assumed Plans
 
Number of Restricted Stock Units
 
Number of Restricted Stock Units
 
Time-Based
 
Performance - Based
 
Weighted Average Grant Date Fair Value Per Unit
 
Time-Based
 
Performance - Based
 
Weighted Average Grant Date Fair Value Per Unit
Granted
300,899

 
392,388

 
$
44.83

 
153,049

 
84,614

 
$
44.44

Outstanding
757,020

 
830,880

 
$
44.55

 
305,008

 
80,046

 
$
46.83
Schedule of unrecognized compensation expenses
The table below summarizes the unrecognized compensation cost related to the outstanding RSUs at June 30, 2014.
 
Unrecognized Compensation Cost
 
Weighted Average Period
 
(in thousands)
 
 
LTIP
$
47,342

 
2.38
Assumed Plans
$
14,823

 
2.97