Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2012

Stock-based Compensation Expense

 The stock-based compensation expense related to all of our stock-based awards and employee stock purchases for the years ended December 31, 2012, 2011 and 2010 are as follows (in thousands):

	For the Years Ended December 31,
	2012		2011		2010
Cost of revenues	$	1,843	$	1,818	$	1,629
Sales and marketing	5,581		5,495		4,430
General and administrative	10,361		9,096		7,931
Research and development	3,698		2,756		2,082
Total stock-based compensation	$	21,483	$	19,165	$	16,072

Stock Option Activity

Activity for the year ended December 31, 2012, under the stock option plans are set forth below (in thousands, except years and per share amounts):

	Stock Options
	Number of Shares Underlying Stock Options		Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term (in years )	Aggregate Intrinsic Value
Outstanding as of December 31, 2011	6,190		14.23
Granted	—		—
Exercised	(2,844	)	13.03
Cancelled or expired	(70	)	17.14
Outstanding as of December 31, 2012	3,276		$	15.21	4.29	$	41,088
Vested and expected to vest at December 31, 2012	3,252		$	15.18	4.28	$	40,876
Exercisable at December 31, 2012	2,733		$	14.62	4.20	$	35,903

Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Method Used

The following weighted-average assumptions used in the Monte Carlo simulation were as follows:

	Year Ended December 31,
	2012			2011			2010
Expected term (in years)	3.0			3.0			N/A
Expected volatility	54.0		%	58.4		%	N/A
Risk-free interest rate	0.4		%	1.3		%	N/A
Expected dividends	—			—			N/A
Weighted average fair value per share at grant date	$	29.45		$	22.12		N/A

2001 Purchase Plan

Weighted Average Assumptions Used for the Fair Value of Options Component of Purchase Plan Granted Estimated at Grant Date

The fair value of the option component of the Purchase Plan shares was estimated at the grant date using the Black-Scholes option pricing model with the following weighted average assumptions:

	December 31,
	2012			2011			2010
Employee Stock Purchase Plan:
Expected term (in years)	1.2			1.5			1.3
Expected volatility	49.7		%	43.2		%	55.8		%
Risk-free interest rate	0.2		%	0.4		%	0.4		%
Expected dividends	—			—			—
Weighted average fair value at grant date	$	11.10		$	7.29		$	7.22

Stock Option

Weighted Average Assumptions Used for the Fair Value of Options Component of Purchase Plan Granted Estimated at Grant Date

The fair value of stock options granted was estimated at the grant date using the Black-Scholes option pricing model with the following weighted average assumptions:

	2012			2011			2010
Stock options (1):
Expected term (in years)	—			4.4			4.4
Expected volatility	—		%	60.6		%	63.3		%
Risk-free interest rate	—		%	1.7		%	1.9		%
Expected dividends	—			—			—
Weighted average fair value at grant date	$	—		$	10.87		$	9.08

Restricted Stock Units (RSUs)

Summary Of Nonvested Shares

A summary for the year ended December 31, 2012, is as follows (in thousands, except years and per share amounts):

	Shares Underlying  RSUs		Average Grant Date Fair Value Price per Share		Weighted Remaining Vesting Period (in years)	Aggregate Intrinsic Value
Nonvested as of December 31, 2011	1,208		18.71
Granted	897		27.77
Vested and released	(443	)	17.57
Forfeited	(162	)	23.48
Nonvested as of December 31, 2012	1,500		$	23.95	1.34	$	41,632

Market Performance Based Restricted Stock Units

Summary Of Nonvested Shares

The following table summarizes the MSU performance as of December 31, 2012:

	Number of  Shares Underlying MSUs (in thousands)		Weighted  Average Remaining Vesting Period (in years )	Aggregate Intrinsic  Value (in thousands)
Nonvested as of December 31, 2011	128
Granted	198
Vested and released	(18	)
Forfeited	(42	)
Nonvested as of December 31, 2012	266		1.54	$	7,368