Convertible Preferred Stock Warrant - Fair Value of Convertible Preferred Stock Warrant Liability (Detail)	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Series C Convertible Preferred Stock Warrant
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Expected term (in years)		5 years 3 months 18 days	2 years
Expected volatility		30.00%	30.00%
Risk-free interest rate		1.70%	0.40%
Expected dividend yield		0.00%	0.00%
Common Stock Warrant
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Expected term (in years)	5 years
Expected volatility	31.80%
Risk-free interest rate	1.60%
Expected dividend yield	0.00%

Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

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Risk-free interest rate assumption used in valuing an instrument.

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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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No definition available.

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