Short-Term Investments - Summary of Short-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 6,928	$ 26,656
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(5)	(52)
Total short-term investments, Estimated Fair Value	6,923	26,604
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	6,928	25,557
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(5)	(52)
Total short-term investments, Estimated Fair Value	$ 6,923	25,505
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost		1,099
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Total short-term investments, Estimated Fair Value		$ 1,099