Fair Value Measurements - Additional Information (Detail) - eNeura Note [Member] - eNeura Inc [Member] - USD ($) $ in Millions		9 Months Ended
	Mar. 04, 2015	Sep. 30, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Non-refundable fees paid	$ 0.3
Accrued interest on promissory note	8.00%
Maturity description of Promissory note		The eNeura Note will mature on the earlier of (i) March 4, 2019, or (ii) exercise of the Option.
Debt Instrument, Maturity Date		Mar. 04, 2019
Convertible Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Principal amount of promissory note	$ 15.0