Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Summary of Assets Measured at Fair Value (Detail)

v3.10.0.1
Fair Value Measurements - Summary of Assets Measured at Fair Value (Detail) - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value $ 56,213 $ 73,992
Money market funds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 10,134 12,218
Corporate debt securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 46,079 61,774
Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 10,134 12,218
Level 1 [Member] | Money market funds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 10,134 12,218
Level 1 [Member] | Corporate debt securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 0 0
Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 46,079 61,774
Level 2 [Member] | Money market funds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 0 0
Level 2 [Member] | Corporate debt securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 46,079 61,774
Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 0 0
Level 3 [Member] | Money market funds [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value 0 0
Level 3 [Member] | Corporate debt securities [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets fair value $ 0 $ 0