Estimated Fair Value of Convertible Preferred Stock Warrant Determined Using Black-Sholes Option Pricing Mode (Detail)	5 Months Ended	12 Months Ended
May 22, 2013	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility	79.00%	82.00%
Dividend yield
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.10%	0.30%
Estimated term equal to the remaining contractual term	1 year 8 months 12 days	2 years 1 month 6 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.90%	0.60%
Estimated term equal to the remaining contractual term	3 years 9 months 18 days	4 years 2 months 12 days

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=25499696&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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