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
Sep. 30, 2016
Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis $ 12,953 $ 39,112
Unrealized Gain 4 1
Unrealized Loss (2) (22)
Fair Value 12,955 39,091
Money Market Funds    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 2,841 5,421
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 2,841 5,421
Certificates of Deposit    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 0 696
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 0 696
Corporate Debt Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 3,263 12,578
Unrealized Gain 0 1
Unrealized Loss (2) (8)
Fair Value 3,261 12,571
U.S. Government Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 5,298 21,783
Unrealized Gain 4 0
Unrealized Loss 0 (14)
Fair Value 5,302 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 16,487 6,145
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 16,487 6,145
Marketable Securities Including Cash Equivalents    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 27,889 48,531
Unrealized Gain 4 1
Unrealized Loss (2) (22)
Fair Value 27,891 48,510
Less Cash Equivalents    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 14,936 9,419
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value $ 14,936 $ 9,419