Share-Based Payments (Tables)

12 Months Ended

Dec. 31, 2017

Share-Based Payments

Schedule of share-based compensation recognized related to the grant of employee and non-employee stock options, SAR, Employee Stock Purchase Plan (ESPP) awards and non-vested stock

Share-based compensation recognized related to the grant of employee and non-employee stock options, SAR, Employee Stock Purchase Plan (ESPP) awards and non-vested stock was as follows, in thousands of dollars:

	Year Ended December 31,
	2017		2016		2015
Research and development	$	1,387	$	1,107	$	874
Selling, general and administrative		7,046		4,819		3,216
Total	$	8,433	$	5,926	$	4,090

Schedule of assumptions used in estimation of fair value of each award option on the date of grant using Black-Scholes option-pricing model

	Year Ended December 31,
	2017	2016	2015
Fair value of common stock	$25.30 - $41.00	$12.98 - $22.80	$9.13 - $21.21
Expected volatility	53.61% - 60.6%	60.9% - 64.5%	60.9% - 64.6%
Dividend yield	0%	0%	0%
Expected term	6.25 years	6.25 years	6.25 years
Risk-free interest rate	1.90% - 2.18%	1.14% - 2.15%	1.54% - 1.74%
Expected forfeiture rate	0%	5%	5%

Summary of stock option and SAR activity

	Number of Options			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)
Outstanding, December 31, 2015		2,699,007		$	8.94		7.92
Granted		1,058,850		$	13.32
Exercised		(85,694	)	$	6.51
Forfeited		(28,075	)	$	12.23
Outstanding, December 31, 2016		3,644,088		$	10.25		7.59
Granted		1,130,155		$	26.57
Exercised		(407,477	)	$	9.31
Forfeited		(86,096	)	$	17.24
Outstanding, December 31, 2017		4,280,670		$	14.50		7.37
As of December 31, 2017:
Vested and expected to vest		4,280,670		$	14.50		7.37
Exercisable		1,952,769		$	9.35		6.16