FINANCIAL ASSETS MEASURED AT FAIR VALUE (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	$ 300,602	$ 180,870
Quoted Prices in Active Markets (Level 1)
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	108,904	15,610
Significant Other Observable Inputs (Level 2)
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	191,698	165,260
Significant Unobservable Inputs (Level 3)
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	0	0
Money Market Funds
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	108,904	15,610
Money Market Funds | Quoted Prices in Active Markets (Level 1)
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	108,904	15,610
Money Market Funds | Significant Other Observable Inputs (Level 2)
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	0	0
Money Market Funds | Significant Unobservable Inputs (Level 3)
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	0	0
US Treasury Bills and Notes
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	191,698	165,260
US Treasury Bills and Notes | Quoted Prices in Active Markets (Level 1)
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	0	0
US Treasury Bills and Notes | Significant Other Observable Inputs (Level 2)
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	191,698	165,260
US Treasury Bills and Notes | Significant Unobservable Inputs (Level 3)
Financial Assets Measured at Fair Value [Line Items]
Assets fair value disclosure Recurring	$ 0	$ 0