Summary of Stock Option Activity (Detail) - Employee Stock Option - 2013 Equity Incentive Plan and Inducement Plan	6 Months Ended
Jun. 30, 2018 $ / shares shares
Shares Subject to Outstanding Stock Options
Beginning balance \| shares	6,514,538
Options granted \| shares	1,421,928
Options exercised \| shares	(273,477)
Options canceled \| shares	(271,578)
Ending balance \| shares	7,391,411
Weighted-Average Exercise Price Per Share
Beginning balance \| $ / shares	$ 31.36
Options granted \| $ / shares	46.13
Options exercised \| $ / shares	23.76
Options canceled \| $ / shares	40.12
Ending balance \| $ / shares	$ 34.16

The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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