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Stock-Based Compensation - Summary of Options Outstanding and Vested Pricing of Exercise Prices (Detail) - Employee Stock Option	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding	9,811,356
Options Outstanding, Weighted-Average Life (in Years)	7 years 7 months 24 days
Purchase of fully-vested incentive stock option	4,046,009
Weighted Average Remaining Contractual Life, Vested and Exercisable	8 years 2 months 5 days
$0.22
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 0.22
Options Outstanding, Number Outstanding	1,404,060
Options Outstanding, Weighted-Average Life (in Years)	8 years 5 months 16 days
Purchase of fully-vested incentive stock option	987,472
Weighted Average Remaining Contractual Life, Vested and Exercisable	8 years 5 months 16 days
$0.42
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 0.42
Options Outstanding, Number Outstanding	1,115,144
Options Outstanding, Weighted-Average Life (in Years)	8 years 10 months 2 days
Purchase of fully-vested incentive stock option	949,281
Weighted Average Remaining Contractual Life, Vested and Exercisable	8 years 9 months 11 days
$1.76
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 1.76
Options Outstanding, Number Outstanding	1,578,253
Options Outstanding, Weighted-Average Life (in Years)	9 years 2 months 12 days
Purchase of fully-vested incentive stock option	357,420
Weighted Average Remaining Contractual Life, Vested and Exercisable	9 years 2 months 12 days
$2.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 2.00
Options Outstanding, Number Outstanding	2,406,949
Options Outstanding, Weighted-Average Life (in Years)	9 years 4 months 13 days
Purchase of fully-vested incentive stock option	792,673
Weighted Average Remaining Contractual Life, Vested and Exercisable	9 years 4 months 13 days
$2.20
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 2.20
Options Outstanding, Number Outstanding	1,851,500
Options Outstanding, Weighted-Average Life (in Years)	3 years 5 months 23 days
Purchase of fully-vested incentive stock option	231,438
Weighted Average Remaining Contractual Life, Vested and Exercisable	3 years 5 months 23 days
$ 25.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 25.00
Options Outstanding, Number Outstanding	1,455,450
Options Outstanding, Weighted-Average Life (in Years)	6 years 8 months 23 days
Purchase of fully-vested incentive stock option	727,725
Weighted Average Remaining Contractual Life, Vested and Exercisable	6 years 8 months 23 days

X

- Definition

As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

+ 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 (e)(1)



-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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+ References

No definition available.

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- Definition

The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ 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 (c)(1)(i)-(ii)



-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Weighted average remaining contractual term for fully vested and expected to vest options that are exercisable or convertible, 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 (e)(2)



-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

+ 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 (c)(1)(iii)



-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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+ 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 (e)(1)



-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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