Stock-Based Compensation Expense (Tables)

3 Months Ended

Mar. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Effect of Recording Stock-Based Compensation Expense

The effect of recording stock-based compensation expense for the three months ended March 31, 2020 and 2019 is as follows (in thousands):

	Three Months Ended
	March 31, 2020			March 31, 2019
Research, development and other related costs	$	3,036		$	3,603
Selling, general and administrative		4,951			4,020
Total stock-based compensation expense		7,987			7,623
Tax effect on stock-based compensation expense		(1,000	)		(1,315	)
Net effect on net income (loss)	$	6,987		$	6,308

Stock-Based Compensation Expense Categorized by Equity Components

Stock-based compensation expense categorized by various equity components for the three months ended March 31, 2020 and 2019 is summarized in the table below (in thousands):

	Three Months Ended
	March 31, 2020		March 31, 2019
Restricted stock awards and units	$	7,294	$	6,934
Employee stock purchase plan		690		621
Employee stock options		3		68
Total stock-based compensation expense	$	7,987	$	7,623

Schedule of Assumptions Used to Value Options Granted

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

	February 2020			February 2019
Expected life (years)		2.0			2.0
Risk-free interest rate		1.4	%		2.5	%
Dividend yield		4.0	%		5.4	%
Expected volatility		45.8	%		53.4	%