Stock-Based Compensation Expense

6 Months Ended

Jun. 30, 2018

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 and six months ended June 30, 2018 and 2017 is as follows (in thousands):

	Three Months Ended						Six Months Ended
	June 30, 2018			June 30, 2017			June 30, 2018			June 30, 2017
Research, development and other related costs	$	3,344		$	3,437		$	6,438		$	6,134
Selling, general and administrative	3,875			5,087			8,189			9,451
Total stock-based compensation expense	7,219			8,524			14,627			15,585
Tax effect on stock-based compensation expense	(1,159		)	(2,359		)	(2,415		)	(4,379		)
Net effect on net income (loss)	$	6,060		$	6,165		$	12,212		$	11,206

Stock-based compensation expense categorized by various equity components for the three and six months ended June 30, 2018 and 2017 is summarized in the table below (in thousands):

	Three Months Ended				Six Months Ended
	June 30, 2018		June 30, 2017		June 30, 2018		June 30, 2017
Employee stock options	$	106	$	586	$	283	$	1,231
Restricted stock awards and units	6,379		7,301		12,810		13,287
Employee stock purchase plan	734		637		1,534		1,067
Total stock-based compensation expense	$	7,219	$	8,524	$	14,627	$	15,585

There were no options granted in the three and six months ended June 30, 2018 and 2017.

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

	February 2018		February 2017
Expected life (years)	2.0		2.0
Risk-free interest rate	2.2	%	1.2	%
Dividend yield	3.6	%	2.0	%
Expected volatility	39.4	%	28.3	%