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Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

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

Schedule of weighted average assumptions

The weighted average assumptions used in the Black-Scholes model for option grants to employees and directors are presented below:

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Risk-free interest rate	2.81%		1.97%		2.73%		2.22%
Expected volatility	71%		73%		72%		73%
Expected life in years	6.1		6.0		6.2		6.0
Dividend yield	—		—		—		—

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- References

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- Definition

Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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