SHARE-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2012

SHARE-BASED COMPENSATION

Schedule of the assumptions used to determine the fair value of options as of the grant date

	June 30, 2012		June 30, 2011
	Black-Scholes	Binominal	Black-Scholes			Binominal
Risk-free interest rate	0.97% – 1.17%	0.08% – 2.04%	2.20		%	0.03% – 3.18%
Expected stock price volatility	34.22% – 34.65%	34.20% – 34.60%	48.00		%	55.90%
Expected dividend yield	—	—	—			—
Expected option life (in years)	6.25	—	6.25			—
Contractual life (in years)	—	14	—			14
Fair value	$19.25 – $22.80	$11.65 – $17.27	$	16.55		$18.09 and $18.76

Summary of the weighted-average fair value of stock options granted, and the total intrinsic value of stock options exercised

	June 30,
(in thousands, except per share amounts)	2012		2011
Weighted-average fair value at grant date per share	$	16.86	$	16.03
Intrinsic value of options exercised	8,339		2,855
Fair value of options vested	973		788

Summary of the activity of the entity's stock options

	Number of options		Weighted average exercise price		Weighted average contractual term (in years)	Aggregate intrinsic value (in thousands)
Outstanding at December 31, 2011	3,243,958		$	14.19	6.7	$	116,755
Granted	198,500		63.14
Exercised	(177,389	)	12.85
Forfeited	(159,095	)	23.75
Outstanding at June 30, 2012	3,105,974		16.50		6.5	$	175,076
Exercisable at June 30, 2012	1,818,151		$	11.16	5.8	$	112,847