Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents and Short-Term Investments (Detail) $ in Thousands	Dec. 31, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 12,047
Unrealized Gain	0
Unrealized (Loss)	0
Estimated Fair Value	12,047
Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	671
Unrealized Gain	0
Unrealized (Loss)	0
Estimated Fair Value	671
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,864
Unrealized Gain	0
Unrealized (Loss)	0
Estimated Fair Value	2,864
U.S. Government Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,008
Unrealized Gain	0
Unrealized (Loss)	0
Estimated Fair Value	3,008
Corporate Bonds and Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,504
Unrealized Gain	0
Unrealized (Loss)	0
Estimated Fair Value	5,504
Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Gain	0
Unrealized (Loss)	0
Estimated Fair Value	3,535
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Gain	0
Unrealized (Loss)	0
Estimated Fair Value	$ 8,512