STOCK-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Compensation expense included in the Company’s Condensed Consolidated Statements of Comprehensive Loss for all stock-based compensation arrangements was as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Cost of sales	$	3,974	$	3,007	$	10,360	$	7,803
R&D		14,257		13,832		43,099		39,973
Selling, general and administrative		18,815		19,064		58,802		58,902
Total stock-based compensation expense	$	37,046	$	35,903	$	112,261	$	106,678

Stock Option Valuation Assumptions

The assumptions used to estimate the per share fair value of stock options granted under the Company’s 2017 Equity Incentive Plan and the Company’s Amended and Restated 2006 Share Incentive Plan were as follows:

	Three Months Ended September 30,		Nine Months Ended September 30,
	2018	2017	2018	2017
Expected volatility	36.8%	38.0 – 39.7%	36.8 – 38.4%	37.6 – 39.7%
Dividend yield	0.0%	0.0%	0.0%	0.0%
Expected life	5.7 years	4.9 – 6.6 years	4.6 – 5.7 years	4.9 – 6.6 years
Risk-free interest rate	2.8%	1.8 – 2.1%	2.3 – 2.8%	1.8 – 2.2%

Summary of Restricted Stock Unit Awards with Performance Conditions

The following table details the base RSUs granted, RSUs earned and expected to vest and the performance multiplier achieved for the RSUs with performance-based vesting conditions for the years ended December 31, 2017, 2016 and 2015, respectively, as well as the base RSUs granted in March 2018:

			Grant Date
Date of Grant	Base RSUs Granted		Fair Value per RSU		Multiplier Achieved	RSUs Earned
March 2018		129,680	$	83.57	(a)	(a)
March 2017		133,250	$	87.42	1.03		132,548
March 2016		130,310	$	83.43	1.03		134,219
March 2015		58,300	$	108.36	1.11		64,713

(a)

The Company’s Compensation Committee is expected to approve the multiplier and total earned RSUs in the first quarter of 2019 based on the Company’s performance against the 2018 managed revenue target. The Company evaluated the 2018 revenue target in the context of its current 2018 revenue forecast, and related confidence level in the forecast, and determined that attainment of the revenue target was probable for accounting purposes commencing in the first quarter of 2018.