Stock Option Plan - Fair Value of Option Grant Estimated on Grant Date Using Black-Scholes Option-pricing Model (Details) - $ / shares	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement Assumptions Used To Estimate Fair Values Of Share Options Granted [Line Items]
Estimated dividend yield	0.00%	0.00%	0.00%
Expected volatility	75.08%		102.77%
Expected volatility, minimum		65.96%
Expected volatility, maximum		102.77%
Risk-free interest rate	1.32%		1.88%
Risk-free interest rate, minimum		1.48%
Risk-free interest rate, maximum		1.81%
Expected life of options (in years)	5 years 8 months 19 days		6 years
Weighted-average fair value per share	$ 11.47	$ 6.83
Minimum
Share Based Compensation Arrangement Assumptions Used To Estimate Fair Values Of Share Options Granted [Line Items]
Expected life of options (in years)		5 years 1 month 6 days
Weighted-average fair value per share			$ 6.59
Maximum
Share Based Compensation Arrangement Assumptions Used To Estimate Fair Values Of Share Options Granted [Line Items]
Expected life of options (in years)		5 years 10 months 24 days
Weighted-average fair value per share			$ 7.06

Share Based Compensation Arrangement Assumptions Used To Estimate Fair Values Of Share Options Granted [Line Items]

No definition available.

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- Definition

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.

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- Definition

The estimated measure of the 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.

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

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- Definition

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

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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

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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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 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: 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

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