Stock Based Awards and Other Equity Instruments (Tables)

6 Months Ended

Jun. 30, 2013

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Status and Activity for Stock Option Awards Relating to Common Stock

A summary of the status and activity for stock option awards relating to our common stock for the six months ended June 30, 2013, is presented below:

	Options Outstanding		Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life		Aggregate Intrinsic Value
	(In thousands)				(In years)		(In thousands)
Options outstanding at January 1, 2013		8,654	$	31.41
Granted		1,562		46.35
Exercised		875		22.69			$	26,740
Cancelled		321		36.23
Options outstanding at June 30, 2013		9,020	$	34.67		6.0	$	236,321
Exercisable as of June 30, 2013		3,756	$	29.03		3.5	$	119,593
Vested and expected to vest after June 30, 2013		8,439	$	34.12		6.0	$	223,343

Weighted-Average Assumptions of Estimated Fair Value of Stock Option Grants

The fair value of stock option grants under the 2011 Incentive Plan has been estimated at the date of grant using the Black–Scholes model with the following weighted average assumptions for the periods presented below:

	Three months ended June 30,						Six months ended June 30,
	2013			2012			2013			2012
Risk free interest rate		1.07	%		1.05	%		1.07	%		1.05	%
Expected term (in years)		6.25			6.21			6.25			6.21
Expected volatility		51.82	%		53.34	%		51.73	%		53.34	%
Expected dividend yield		0	%		0	%		0	%		0	%

Summary of RSU Activity on Common Stock

The following table presents a summary of RSU activity on our common stock:

	RSUs Outstanding		Weighted Average Grant- Date Fair Value Per Share
	(in thousands)
Unvested RSUs outstanding as of January 1, 2013		446	$	26.11
Granted		994		47.05
Vested and released (1)		306		22.01
Cancelled		40		41.23
Unvested RSUs outstanding as of June 30, 2013		1,094	$	45.13

(1) Inclusive of 117,403 RSUs withheld to satisfy employee minimum tax withholding requirements using net shares settlement method. Total payments for the employees’ tax obligations to the taxing authorities were $5.5 million and $3.0 million for the six months ended June 30, 2013 and 2012, respectively, and are reflected as a financing activity within the consolidated statements of cash flows. RSUs that are withheld to satisfy employee minimum tax withholding requirements remain in the authorized but unissued pool under the 2011 Incentive Plan.

Summary of Unrecognized Compensation Expense, Net of Estimated Forfeitures and Weighted Average Period Remaining

A summary of the unrecognized compensation expense, net of estimated forfeitures, and the weighted average period remaining at June 30, 2013 related to our non-vested stock options and RSU awards is presented below (in thousands, except year information):

	Stock Options		RSUs
Unrecognized compensation expense (net of forfeitures)	$	77,179	$	32,234
Weighted average period remaining (in years)		2.89		3.51