Major Category of Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring $ in Thousands	Dec. 31, 2016 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	$ 101,367
Liabilities	6,119
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	81,819
U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	808
Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	18,740
Contingent consideration - short-term
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities	6,119
Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	82,627
Quoted prices in active markets for identical assets (Level 1) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	81,819
Quoted prices in active markets for identical assets (Level 1) | U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	808
Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	18,740
Significant other observable inputs (Level 2) | Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	18,740
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities	6,119
Significant unobservable inputs (Level 3) | Contingent consideration - short-term
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities	$ 6,119