Share Based Compensation

3 Months Ended

Mar. 31, 2012

Share Based Compensation [Abstract]

Share Based Compensation

4. Share Based Compensation

The Company has Stock Incentive Plans (the Plans) pursuant to which the Company's board of directors may grant stock options or restricted stock to employees. The Company is authorized to issue grants of restricted stock and stock options to purchase up to 26,963,150 shares as of March 31, 2012 and December 31, 2011. There were 2,099,349 additional shares remaining available for grant under the Plans at March 31, 2012.

The table below summarizes the expense recognized related to share-based payments recognized for the three month periods ended March 31 (in thousands):

	Three Months Ended March 31,
	2012		2011
Stock options	$	2,277	$	2,460
Restricted stock		1,557		1,681
Stock-based compensation	$	3,834	$	4,141

The tax benefits recorded on stock based compensation were $1.2 million and $0.7 million for the three month periods ended March 31, 2012 and 2011, respectively.

The following table summarizes the Company's total unrecognized compensation cost related to stock-based compensation as of March 31, 2012 (in thousands):

	Unrecognized Compensation Cost		Weighted Average Period  of Expense Recognition (in Years)
Stock options	$	23,368		2.18
Restricted stock		11,503		1.60
Total	$	34,871

Stock Options

Stock options are granted with an exercise price estimated to be equal to the fair market value on the date of grant as authorized by the Company's board of directors. Options granted have vesting provisions ranging from one to six years. Stock option grants are generally subject to forfeiture if employment terminates prior to vesting.

The following summarizes the changes in the number of shares of common stock under option for the three month period ended March 31, 2012 (shares and aggregate intrinsic value in thousands):

	Shares			Weighted Average Exercise Price		Options Exercisable at End of Period		Weighted Average Exercise Price of Exercisable Options		Weighted Average Fair Value of Options Granted During the Period	Aggregate Intrinsic Value
Outstanding at December 31, 2011		8,341		$	15.51		4,394	$	10.13		$	119,802
Exercised		(1,019	)		7.77							31,607
Forfeited		(30	)		10.00
Outstanding at March 31, 2012		7,292		$	16.61		3,716	$	11.09		$	161,530
Expected to vest as of March 31, 2012		7,292		$	16.61

The aggregate intrinsic value of stock options exercised during the three months ended March 31, 2012 was $31.6 million.

The fair value of stock option awards granted was estimated using the Black-Scholes option pricing model during the three months ended March 31, 2011, with the following weighted-average assumptions for grants during the period.

Risk-free interest rate	1.76	%
Dividend yield	—
Expected volatility	39.27	%
Expected life (in years)	4.0

There were no stock option awards granted in the three months ended March 31, 2012.

The Company considered the retirement and forfeiture provisions of the options and utilized its historical experience to estimate the expected life of the options.

The risk-free interest rate is based on the yield of a zero coupon U.S. Treasury security with a maturity equal to the expected life of the option from the date of the grant. The Company estimates the volatility of the share price of the Company's common stock by considering the historical volatility of the stock of similar public entities. In determining the appropriateness of the public entities included in the volatility assumption the Company considered a number of factors, including the entity's life cycle stage, size, financial leverage, and products offered.

The weighted-average remaining contractual life for options outstanding was 7.08 and 7.00 years at March 31, 2012 and December 31, 2011, respectively.

Restricted Stock

Awards of restricted stock and restricted stock units are independent of stock option grants and are generally subject to forfeiture if employment terminates prior to vesting. Prior to the Company's initial public offering, the vesting of the shares granted in 2010 were contingent on the sale of the Company or a public offering of the Company's common stock, subject to certain other conditions. The vesting of the shares granted in 2012 and 2011 are generally based on the passage of time, performance or market conditions. Shares vesting based on the passage of time have vesting provisions ranging from one to six years.

There were no restricted stock shares granted based on market conditions during the three months ended March 31, 2012. The fair value of restricted stock shares granted based on market conditions during the three months ended March 31, 2011 was estimated using the Monte Carlo option pricing model at the grant date, with the following assumptions.

	Three Months Ended March 31, 2011
Risk-free interest rate		1.25	%
Dividend yield		—
Expected volatility		37.00	%
Expected life (in years)		0.63

The risk-free interest rate and volatility assumptions were calculated consistently with those applied in the Black-Scholes options pricing model utilized in determining the fair value of the stock option awards.

The following table summarizes the changes in the number of shares of restricted stock and restricted stock units for the three months ended March 31, 2012 (shares in thousands):

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2011		840		$	23.15
Granted		41			34.35
Vested		(22	)		29.59
Cancelled		—			—
Unvested at March 31, 2012		859		$	23.52