The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

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- Definition

The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

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- Definition

The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Price of a single share of a number of saleable stocks of a company.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 14.D.2)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 14
-Section D
-Subsection 2

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Stock Compensation Plans - Ranges of Underlying Assumptions Used to Determine Fair Value of Stock Options Granted to Employees and Non-Employees (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Feb. 12, 2014	Dec. 01, 2013	Sep. 30, 2013	Sep. 03, 2013	Jun. 30, 2013	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of common stock value (usd per share)		$ 5.93	$ 5.93	$ 11.30	$ 7.55	$ 6.77	$ 10.02	$ 9.94	$ 6.82	$ 6.85
Employees and Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.71%	1.53%	0.76%
Risk-free interest rate, maximum	1.85%	1.89%	1.10%
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility, minimum	73.00%	80.00%	90.00%
Expected volatility, maximum	92.00%	85.00%	100.00%
Employees and Directors [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of options (years)	5 years 9 months 18 days	6 years	5 years
Range of common stock value (usd per share)	$ 4.57	$ 7.55	$ 6.77
Employees and Directors [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of options (years)	6 years	6 years 2 months 12 days	5 years 6 months
Range of common stock value (usd per share)	$ 26.71	$ 24.04	$ 9.94
Non-Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	0.10%	0.11%	0.13%
Risk-free interest rate, maximum	1.93%	1.27%	0.86%
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility, minimum	56.00%	73.00%	90.00%
Expected volatility, maximum	94.00%	85.00%	100.00%
Non-Employees [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of options (years)	3 months 18 days	1 year	1 year
Range of common stock value (usd per share)	$ 4.04	$ 11.31	$ 5.93
Non-Employees [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of options (years)	6 years	4 years	4 years
Range of common stock value (usd per share)	$ 25.01	$ 27.24	$ 9.94