Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2013

Stock-based Compensation

Summary of stock option activity

	Shares	Exercise price		Remainingcontractual term(in years)	Aggregate intrinsic value (in thousands)(1)
Balance at December 31, 2012	3,358,408	$	20.39	7.49	$	4,813
Granted	—	—		—	—
Exercised	—	$	—	—	$	—
Forfeited/canceled	—	$	—	—	$	—
Balance at March 31, 2013	3,358,408	$	20.39	7.25	$	29,980
Vested and exercisable as of March 31, 2013	2,238,265	$	20.20	7.23	$	20,421
Vested and exercisable as of March 31, 2013 and expected to vest thereafter(2)	3,353,423	$	20.39	7.25	$	29,934

(1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of our Class A Common Stock as of the respective date.

(2) Options expected to vest reflect an estimated forfeiture rate.

Summary of additional information regarding outstanding and exercisable and vested options

The following table summarizes additional information regarding outstanding and exercisable and vested options at March 31, 2013:

	Options outstanding		Options exercisableand vested
Range of exercise prices	Number ofshares	Weighted-averageremaining life(in years)	Number ofshares	Weighted-averageremaining life(in years)
$20.00	3,208,408	7.21	2,188,265	7.21
$28.80	150,000	8.07	50,000	8.07
$20.00 -$28.80	3,358,408	7.25	2,238,265	7.23

Summary of activities for unvested RSUs

	Unvested Restricted Stock Units
	Number ofshares		Weighted-averagegrant-datefair value
Unvested at December 31, 2012	2,117,510		$	21.38
Granted	139,320		31.53
Vested	(63,899	)	24.65
Forfeited/canceled	—		—
Unvested at March 31, 2013	2,192,931		$	21.95
Expected to vest after March 31, 2013(1)	2,177,818		$	22.16

(1)  RSUs expected to vest reflect an estimated forfeiture rate.