Black-Scholes Option-Pricing Model Assumptions to Estimate Fair Value of the Convertible Preferred Stock Warrants (Detail)	5 Months Ended	12 Months Ended
	May 22, 2013	Dec. 31, 2012
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Volatility	79.00%	82.00%
Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [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
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [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