EQUITY AND SHARE-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2013

EQUITY AND SHARE-BASED COMPENSATION

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

	Three months ended March 31, 2013		Three months ended March 31, 2012
	Black-Scholes	Binomial	Black-Scholes	Binomial
Risk-free interest rate	1.02%–1.13%	0.08%–2.02%	1.16% – 1.17%	0.09% – 2.04%
Expected stock price volatility	36.35%–36.50%	36.40%–36.50%	34.62% – 34.65%	34.50% – 34.60%
Expected dividend yield	—	—	—	—
Expected option life (in years)	6.25	—	6.25	—
Contractual life (in years)	—	14	—	14
Fair value	$31.33–$34.74	$16.12–$30.34	$22.74 – $22.80	$11.65 – $17.27

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

	Three months ended March 31,
(in thousands, except per share amounts)	2013		2012
Weighted-average fair value at grant date per share	$	25.22	$	17.23
Intrinsic value of options exercised	918		8,242
Fair value of options vested	838		275

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, 2012	3,058,309		$	17.69	6.1	$	211,072
Granted	30,000		88.56
Exercised	(16,450	)	27.73
Forfeited	—		—
Outstanding at March 31, 2013	3,071,859		18.32		5.9	159,433
Exercisable at March 31, 2013	2,261,878		12.20		5.3	130,326