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, 2015
Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis $ 42,708 $ 50,222
Unrealized Gain 7 4
Unrealized Loss (10) (17)
Fair Value 42,705 50,209
Money Market Funds    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 4,867 3,369
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 4,867 3,369
Certificates of Deposit    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 841 2,505
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 841 2,505
Corporate Debt Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 18,136 28,094
Unrealized Gain 2 1
Unrealized Loss (10) (14)
Fair Value 18,128 28,081
U.S. Government Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 17,249 19,123
Unrealized Gain 4 3
Unrealized Loss 0 (3)
Fair Value 17,253 19,123
Municipal Securities    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 1,932  
Unrealized Gain 1  
Unrealized Loss 0  
Fair Value 1,933  
Commercial Paper    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 13,392 5,499
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 13,392 5,499
Marketable Securities Including Cash Equivalents    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 56,417 58,590
Unrealized Gain 7 4
Unrealized Loss (10) (17)
Fair Value 56,414 58,577
Less Cash Equivalents    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 13,709 8,368
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value $ 13,709 $ 8,368