Quarterly report pursuant to Section 13 or 15(d)

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

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Fair Value Measurements and Marketable Securities - Summary of Company's Available-for-Sale Securities (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis $ 57,279 $ 74,726
Unrealized Gain 17 38
Unrealized Loss (13) (10)
Fair Value 57,283 74,754
Money Market Funds
    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 6,175 4,285
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 6,175 4,285
Certificates of Deposit
    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 2,554 1,584
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 2,554 1,584
Corporate Debt Securities
    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 33,962 49,001
Unrealized Gain 6 25
Unrealized Loss (12) (7)
Fair Value 33,956 49,019
U. S. Government Securities
    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 20,036 21,722
Unrealized Gain 11 12
Unrealized Loss (1) (3)
Fair Value 20,046 21,731
Municipal Securities
    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 227 2,814
Unrealized Gain 0 1
Unrealized Loss 0 0
Fair Value 227 2,815
Commercial Paper
    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 5,347 2,599
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value 5,347 2,599
Marketable Securities Including Cash Equivalents
    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 68,301 82,005
Unrealized Gain 17 38
Unrealized Loss (13) (10)
Fair Value 68,305 82,033
Less Cash Equivalents
    
Schedule Of Available For Sale Securities [Line Items]    
Cost Basis 11,022 7,279
Unrealized Gain 0 0
Unrealized Loss 0 0
Fair Value $ 11,022 $ 7,279