Stock-Based Compensation Expense

3 Months Ended

Mar. 31, 2017

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

Stock-Based Compensation Expense

STOCK-BASED COMPENSATION EXPENSE

The effect of recording stock-based compensation expense for the three months ended March 31, 2017 and 2016 is as follows (in thousands):

	Three Months Ended
	March 31, 2017			March 31, 2016
Research, development and other related costs	$	2,870		$	1,384
Selling, general and administrative	4,211			2,256
Total stock-based compensation expense	7,081			3,640
Tax effect on stock-based compensation expense	(2,019		)	(1,010		)
Net effect on net income (loss)	$	5,062		$	2,630

Stock-based compensation expense categorized by various equity components for the three months ended March 31, 2017 and 2016 is summarized in the table below (in thousands):

	Three Months Ended
	March 31, 2017		March 31, 2016
Employee stock options	$	645	$	509
Restricted stock awards and units	6,006		2,932
Employee stock purchase plan	430		199
Total stock-based compensation expense	$	7,081	$	3,640

The following assumptions were used to value the options granted:

	Three Months Ended
	March 31, 2017	March 31, 2016
Expected life (in years)	*	*
Risk-free interest rate	*	*
Dividend yield	*	*
Expected volatility	*	*

* There were no options granted in the three months ended March 31, 2017 and 2016.

ESPP grants occur in February and August. The following assumptions were used to value the ESPP shares for these grants:

	February 2017		February 2016
Expected life (years)	2.0		2.0
Risk-free interest rate	1.2	%	0.8	%
Dividend yield	2.0	%	2.4	%
Expected volatility	28.3	%	30.0	%