Quarterly report pursuant to Section 13 or 15(d)

Marketable Securities and Fair Value - Summary of Company's Available-for-Sale Securities (Detail)

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Marketable Securities and Fair Value - Summary of Company's Available-for-Sale Securities (Detail) - USD ($)
$ in Thousands
Mar. 31, 2017
Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis $ 6,164 $ 13,002
Unrealized Gain 0 1
Unrealized Loss (1) (3)
Fair Value 6,163 13,000
Money Market Funds    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 3,102 2,746
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 3,102 2,746
Corporate Debt Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 1,565 4,208
Unrealized Gain 0 0
Unrealized Loss 0 (2)
Fair Value 1,565 4,206
U.S. Government Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 3,200 5,299
Unrealized Gain 0 1
Unrealized Loss (1) (1)
Fair Value 3,199 5,299
Commercial Paper    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 9,245 10,966
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 9,245 10,966
Marketable Securities Including Cash Equivalents    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 17,112 23,219
Unrealized Gain 0 1
Unrealized Loss (1) (3)
Fair Value 17,111 23,217
Less Cash Equivalents    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 10,948 10,217
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value $ 10,948 $ 10,217