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
Jun. 30, 2016
Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis $ 21,184 $ 39,112
Unrealized Gain 7 1
Unrealized Loss (2) (22)
Fair Value 21,189 39,091
Money Market Funds    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 1,857 5,421
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 1,857 5,421
Certificates of Deposit    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 100 696
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 100 696
Corporate Debt Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 4,068 12,578
Unrealized Gain 0 1
Unrealized Loss (1) (8)
Fair Value 4,067 12,571
U.S. Government Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 13,574 21,783
Unrealized Gain 7 0
Unrealized Loss (1) (14)
Fair Value 13,580 21,769
Municipal Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis   1,908
Unrealized Gain   0
Unrealized Loss   0
Fair Value   1,908
Commercial Paper    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 13,987 6,145
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 13,987 6,145
Marketable Securities Including Cash Equivalents    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 33,586 48,531
Unrealized Gain 7 1
Unrealized Loss (2) (22)
Fair Value 33,591 48,510
Less Cash Equivalents    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 12,402 9,419
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value $ 12,402 $ 9,419