SHARE-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 2012

SHARE-BASED COMPENSATION

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

	Nine months ended September 30, 2012				Nine months ended September 30, 2011
	Black-Scholes		Binominal		Black-Scholes		Binominal
Risk-free interest rate	0.87% — 1.17%		0.08% — 2.04%		1.69% — 1.93%		0.04% — 3.03%
Expected stock price volatility	34.22% — 34.65%		34.20% — 34.60%		48.00%		55.70 — 55.80%
Expected dividend yield	—		—		—		—
Expected option life (in years)	6.25		—		6.25		—
Contractual life (in years)	—		14		—		14
Fair value	$	19.25 — $29.80	$	9.98 — $22.76	$	16.33 — $17.85	$	16.91 — $20.39

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

	Nine months ended September 30,
(in thousands, except per share amounts)	2012		2011
Weighted-average fair value at grant date per share	$	20.77	$	17.66
Intrinsic value of options exercised	11,535		4,193
Fair value of options vested	1,491		2,240

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	278,500		69.48
Exercised	(221,615	)	13.00
Forfeited	(179,095	)	28.35
Outstanding at September 30, 2012	3,121,748		18.28		6.3	$	212,188
Exercisable at September 30, 2012	1,936,789		$	11.28	5.6	$	145,205