Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Mar. 04, 2015	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized loss on debt securities		$ 3,348
Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of debt security		12,658
Unrealized loss on debt securities		$ 3,348
eNeura Note [Member] | eNeura Inc [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Non-refundable fees paid	$ 300
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
eNeura Note [Member] | eNeura Inc [Member] | Convertible Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Principal amount of promissory note	$ 15,000