Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Additional Information (Detail)

v3.8.0.1
Fair Value Measurements - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2017
USD ($)
shares
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]  
Warrant liability | $ $ 0
Maximum maturity period of cash and cash equivalents 90 days
Maximum maturity period of short-term investments 1 year
Series A and Series B Warrants issued in July 2014 Financing [Member]  
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]  
Warrants outstanding and exercisable | shares 0
Maximum [Member]  
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]  
Maturity period of securities 1 year