Major Category of Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring $ in Thousands	Sep. 30, 2016 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	$ 138,792
Liabilities	6,261
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	117,733
U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	2,517
Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	18,542
Contingent consideration - short-term
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities	6,261
Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	119,750
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	117,733
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	2,017
Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	19,042
Significant other observable inputs (Level 2) | U.S. Government and agency securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	500
Significant other observable inputs (Level 2) | Corporate and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets	18,542
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities	6,261
Significant unobservable inputs (Level 3) | Contingent consideration - short-term
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities	$ 6,261