STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Grants in Period, Weighted Average Grant Date Fair Value

The weighted average grant date per share fair values of the options awarded to employees were as follows:

	Year Ended
	December 31, 2014		December 31, 2013		December 31, 2012
Weighted average grant date per share fair value	$	9.63	$	6.34	$	5.90

Fair Value of Options, Assumptions Schedule

The fair value of the options was estimated on the date of the grant using a Black-Scholes option pricing model with the following assumptions:

	Year Ended
	December 31, 2014					December 31, 2013					December 31, 2012
Risk-free interest rate	1.51	%	-	1.95	%	0.98	%	-	1.74	%	0.90	%	-	1.10	%
Expected term (years)	5.3		-	6.4		6.1		-	6.4		6
Expected volatility	35.0	%	-	41.0	%	41.0	%	-	44.0	%	44.0	%	-	47.0	%
Expected dividend yield	—%					—%					—%

Summary of Stock Option Activity

Stock option activity during the years ended December 31, 2014, 2013 and 2012 is summarized as follows:  

	Option Shares (thousands)		Weighted average exercise price		Weighted average remaining contractual life (years)	Aggregate intrinsic value (thousands)
Outstanding at December 31, 2011	6,454		$	5.14
Granted	1,228		13.10
Exercised	(1,061	)	1.42
Forfeited	(368	)	9.55
Outstanding at December 31, 2012	6,253		6.99
Granted	1,222		14.78
Exercised	(2,173	)	3.48
Forfeited	(416	)	12.23
Outstanding at December 31, 2013	4,886		10.04
Granted	1,495		23.45
Exercised	(1,263	)	7.71
Forfeited	(264	)	15.33
Outstanding at December 31, 2014	4,854		14.50		7.1	$	45,731
Exercisable at December 31, 2014	2,390		9.08		5.4	35,093
Expected to vest at December 31, 2014	2,464		$	19.76	8.8	$	10,638

Stock Option Compensation Expense and Intrinsic Value Schedule

Compensation expense related to stock options granted to employees and non-employees under the Plans and the intrinsic value of stock options exercised was as follows:

	Year Ended
(In thousands)	December 31, 2014		December 31, 2013		December 31, 2012
Compensation expense related to stock options	$	7,111	$	5,177	$	4,635
Intrinsic value of stock options exercised	20,216		25,034		12,507