Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense (in thousands):

	Year ended December 31,
	2014		2013		2012
Employee stock-based compensation in:
Cost of revenue	$	2,359	$	2,411	$	2,828
Research and development expense	4,844		4,431		6,151
Selling, general and administrative expense	10,084		9,160		9,449
Total stock-based compensation in operating expense	14,928		13,591		15,600
Total employee stock-based compensation recognized in income (loss) from continuing operations	$	17,287	$	16,002	$	18,428

Valuation Assumptions for Stock Options

The Company estimated the fair value of all employee stock options using a Black-Scholes valuation model with the following weighted average assumptions:

	Employee Stock Options
	2014		2013		2012
Expected term (in years)	4.70		4.70		4.70
Volatility	40	%	50	%	56	%
Risk-free interest rate	1.7	%	0.9	%	0.9	%
Dividend yield	0.0	%	0.0	%	0.0	%

Employee Stock Purchase Plan

The call option and put option were valued using the Black-Scholes option pricing model with the following assumptions:

	Employee Stock Purchase Plan
	2014		2013		2012
Expected term (in years)	0.50		0.50		0.50
Volatility	32	%	31	%	49	%
Risk-free interest rate	0.1	%	0.2	%	0.2	%
Dividend yield	0.0	%	0.0	%	0.0	%