Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary and Allocation of Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense recorded for the periods presented and its allocation within the condensed consolidated statements of operations (in thousands):

	Three Months Ended
	March 31, 2016		March 31, 2015
Cost of  product revenues	$	781	$	955
Cost of service revenues		1,111		1,308
Stock-based compensation expense included in cost    of revenues		1,892		2,263
Sales and marketing		3,743		2,613
Research and development		2,029		2,573
General and administrative		3,816		1,783
Stock-based compensation expense included in    operating expenses		9,588		6,969
Stock-based compensation expense related to employee    equity awards and employee stock purchases		11,480		9,232
Tax benefit		2,245		1,529
Stock-based compensation expense related to employee    equity awards and employee stock purchases,    net of tax	$	9,235	$	7,703

Significant Assumptions Used to Estimate Fair Value of Employee Stock Purchase Plan

The fair value of each employee stock purchase right grant is estimated on the date of grant using the Black-Scholes option valuation model and is recognized as expense using the graded vesting method using the following assumptions:

	Three Months Ended
	March 31, 2016		March 31, 2015
Expected volatility	31.85-34.97%		30.04-30.73%
Risk-free interest rate	0.47-0.81%		0.07-0.49%
Expected dividends		0.0%		0.0%
Expected life (years)	0.5-2.0		0.5-2.0