Stock Options And Employee Stock Purchase Plan (Tables)

9 Months Ended

Sep. 30, 2011

Stock Options Activity

	Number of Shares			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at January 1, 2011		3,794,394		$	14.40
Granted		130,819			29.01
Exercised		(1,781,950	)		8.04
Canceled		(41,140	)		24.69
Outstanding at September 30, 2011		2,102,123			20.50	5.8	$	15,655,942
Exercisable at September 30, 2011		1,179,263			19.23	4.3	$	10,587,334
Vested and expected to vest at September 30, 2011		1,959,636		$	20.34	5.6	$	14,970,305

Assumptions To Estimate Fair Value Of Stock Options

	Nine Months Ended September 30,
	2011	2010
Risk-free interest rate	2.39%	2.65%
Expected term (in years)	6.5	6.5
Dividend yield	0%	0%
Expected volatility	42%	44%
Weighted-average volatility	42%	45%

Allocation Of Share-Based Compensation Expense

	Three Months Ended September 30,				Nine Months Ended September 30,
	2011		2010		2011		2010
Cost of revenues	$	246	$	304	$	736	$	963
Operating expenses:
Sales and marketing		350		464		1,049		1,460
Research, development and engineering		110		204		367		645
General and administrative		1,542		1,805		4,532		5,699
Total	$	2,248	$	2,777	$	6,684	$	8,767

Restricted Stock [Member]

Restricted Stock And Restricted Stock Unit Award Activity

				Weighted-Average
				Grant-Date
	Shares			Fair Value
Nonvested at January 1, 2011		816,670		$	19.59
Granted		95,712			28.85
Vested		(152,524	)		20.94
Canceled		(28,675	)		17.61
Nonvested at September 30, 2011		731,183		$	20.60

Restricted Stock Units (RSUs) [Member]

Restricted Stock And Restricted Stock Unit Award Activity

				Weighted-Average
				Grant-Date
	Shares			Fair Value
Nonvested at January 1, 2011		17,500		$	23.59
Granted		2,000			29.21
Vested		(1,000	)		20.72
Canceled		—			—
Nonvested at September 30, 2011		18,500		$	23.75