Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Schedule of exercise prices for stock options outstanding and exercisable

Exercise prices for stock options outstanding and exercisable as of December 31, 2018 are as follows:



	Options Outstanding				Options Exercisable
Price Range	Number Outstanding as of December 31, 2018	Weighted- Average Remaining Contractual Term (In Years)	Weighted- Average Exercise Price		Number Exercisable as of December 31, 2018	Weighted- Average Remaining Contractual Term (In Years)	Weighted- Average Exercise Price
$0.00 - $20.00	51,359	2	$	18.74	51,359	2	$	18.74
$20.01 - $25.00	429,306	1	$	20.18	429,306	1	$	20.18
$25.01 - $30.00	3,300	3	$	26.42	3,300	3	$	26.42
$30.01 - $35.00	352,500	4	$	34.22	352,500	4	$	34.22
$35.01 - $40.00	1,985,200	4	$	38.19	1,832,500	3	$	38.09
$40.01 - $45.00	277,000	7	$	43.98	111,400	7	$	44.04
$45.01 - $50.00	766,973	6	$	47.58	577,473	5	$	47.64
$50.01 - $55.00	487,400	7	$	52.24	197,300	6	$	51.99
$55.01 - $60.00	600,000	8	$	56.97	127,000	8	$	56.95
$60.01 and over	60,000	7	$	60.70	28,000	5	$	60.70
	5,013,038	5	$	41.80	3,710,138	4	$	38.59

Schedule of stock option activity

Our stock option activity was as follows:



	For the years ended December 31,
	2018				2017				2016
	Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price		Options		Weighted- Average Exercise Price
Total options outstanding, beginning of period	4,951,256		$	41.42	5,968,763		$	39.30	5,893,241		$	38.38
Granted	215,500		$	51.71	1,262,500		$	57.12	732,000		$	41.86
Exercised	(108,318	)	$	40.67	(1,018,507	)	$	35.84	(453,182	)	$	28.83
Forfeited and canceled	(45,400	)	$	50.21	(1,261,500	)	$	51.63	(203,296	)	$	45.15
Total options outstanding, end of period	5,013,038		$	41.80	4,951,256		$	41.42	5,968,763		$	39.30
Exercisable at end of period	3,710,138		$	38.59	3,143,656		$	36.98	3,551,063		$	35.40

Schedule of restricted stock unit activity

Our restricted stock unit activity was as follows:



	For the years ended December 31,
	2018			2017				2016
	Restricted Stock Units	Weighted- Average Grant Date Fair Value		Restricted Stock Units		Weighted- Average Grant Date Fair Value		Restricted Stock Units		Weighted- Average Grant Date Fair Value
Total restricted stock units outstanding, beginning of period	—	$	—	6,667		$	34.22	57,328		$	42.31
Vested	—	$	—	(6,667	)	$	34.22	(50,661	)	$	43.38
Total restricted stock units outstanding, end of period	—	$	—	—		$	—	6,667		$	34.22

Schedule of allocated non-cash, stock-based compensation expense for all employees

Total noncash, stock-based compensation expense for all of our employees is shown in the following table for the years ended December 31, 2018, 2017 and 2016, respectively, and was assigned to the same expense categories as the base compensation for such employees:



	For the years ended December 31,
	2018		2017		2016
	(In thousands)
Research and development expenses	$	634	$	1,010	$	1,046
Selling, general and administrative expenses	9,356		10,630		9,865
Total stock-based compensation	$	9,990	$	11,640	$	10,911

Schedule of assumptions of Black-Scholes option valuation model

The fair value of each stock option granted for the years ended December 31, 2018, 2017 and 2016 was estimated at the date of the grant using a Black-Scholes option valuation model. The estimated grant-date fair values and related assumptions were as follows:



	For the years ended December 31,
Assumptions:	2018	2017	2016
Risk-free interest rate	2.25% - 2.99%	1.98% - 2.05%	1.10% - 1.87%
Volatility factor	22.77% - 23.28%	24.20% - 26.69%	27.22% - 27.37%
Expected term of options in years	5.7 - 5.8	5.7 - 5.8	5.7 - 5.8
Weighted-average grant-date fair value	$12.38 - $16.23	$15.25 - $16.49	$11.15 - $12.49