SHARE-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2017

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

Compensation Cost Related to Share Based Compensation

The compensation cost that has been included in the statement of comprehensive loss for all share-based compensation arrangements is as follows (in thousands):


	Years Ended December 31,
	2017		2016		2015
Sales, general and administrative expense	$	27,951	$	16,770	$	15,281
Research and development expense		14,571		11,694		13,111

Share-based compensation expense	$	42,522	$	28,464	$	28,392

Weighted-Average Assumptions for Stock Option Grants using Black-Scholes Option-Pricing Model

The estimated fair value of each option award granted was determined on the date of grant using the Black-Scholes option-pricing valuation model with the following weighted-average assumptions for option grants during the three years ended December 31, 2017:


	Years Ended December 31,
	2017			2016			2015
Risk-free interest rate		2.0	%		1.4	%		1.7	%
Expected volatility of common stock		58	%		60	%		66	%
Dividend yield		0.0	%		0.0	%		0.0	%
Expected option term		5.7 years			5.6 years			6.6 years

Summary and Changes in Stock Options Outstanding

A summary of the status of the Company’s stock options as of December 31, 2017, 2016 and 2015 and of changes in options outstanding under the plans during the three years ended December 31, 2017 is as follows (in thousands, except for weighted average exercise price data):


	2017					2016					2015
	Options			Weighted Average Exercise Price		Options			Weighted Average Exercise Price		Options			Weighted Average Exercise Price
Outstanding at January 1		6,112		$	20.01		5,507		$	15.63		5,750		$	9.31
Granted		1,807			46.55		1,077			40.19		1,159			37.21
Exercised		(1,353	)		10.41		(341	)		7.60		(1,315	)		5.01
Canceled		(210	)		43.05		(131	)		34.35		(87	)		46.08

Outstanding at December 31		6,356		$	28.83		6,112		$	20.01		5,507		$	15.63

Summary and Changes in Restricted Stock Units Outstanding

A summary of the status of the Company’s RSUs as of December 31, 2017, 2016 and 2015 and of changes in RSUs outstanding under the plans for the three years ended December 31, 2017 is as follows (in thousands, except for weighted average grant date fair value per unit):


	2017					2016					2015
	Number of Units			Weighted Average Grant Date Fair Value per Unit		Number of Units			Weighted Average Grant Date Fair Value per Unit		Number of Units			Weighted Average Grant Date Fair Value per Unit
Outstanding at January 1		883		$	29.33		910		$	24.23		669		$	15.01
Granted		588			47.21		326			36.73		448			33.62
Cancelled		(41	)		40.62		(69	)		32.50		(16	)		20.83
Converted into common shares		(350	)		24.19		(284	)		20.71		(191	)		14.24

Outstanding at December 31		1,080		$	40.30		883		$	29.33		910		$	24.23