Summary of Significant Accounting Policies - Additional Information (Detail)		1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 04, 2016 USD ($)	Mar. 31, 2014 USD ($) $ / shares shares	Mar. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) Segment DerivativeContract	Dec. 31, 2015 USD ($) DerivativeContract	Dec. 31, 2014 USD ($)
Significant Accounting Policies [Line Items]
Accumulated deficit				$ (289,253,000)	$ (193,436,000)
Working capital				150,800,000
Proceeds from issuance of common stock in follow-on offering, net of issuance costs	$ 59,100,000			$ 59,136,000	80,209,000
Number of operating segment | Segment				1
Cash and cash equivalents maturity period				Three months or less
Impairments of long-lived assets				$ 0	$ 0	$ 0
Number of securities issued upon exercise of warrants | shares		158,179	158,179
Remeasurement of outstanding warrants | shares		173,910
Warrants to purchase convertible preferred stock, exercise price | $ / shares		$ 5.17	$ 5.17
Reclassification of warrant liability			$ 2,300,000
Convertible preferred stock shares automatically converted into common stock | shares		15,876,104	15,876,104
Series D convertible preferred stock [Member]
Significant Accounting Policies [Line Items]
Remeasurement of preferred stock						9,600,000
IPO [Member]
Significant Accounting Policies [Line Items]
Warrants to purchase convertible preferred stock, exercise price | $ / shares		$ 21.00	$ 21.00
Reclassification of warrant liability						2,752,000
IPO [Member] | Additional Paid-in Capital [Member]
Significant Accounting Policies [Line Items]
Reclassification of warrant liability		$ 2,800,000				$ 2,752,000
Level II Assets [Member]
Significant Accounting Policies [Line Items]
Number of foreign currency derivative contracts outstanding | DerivativeContract				0	0
Minimum [Member]
Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives				3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives				5 years
Percentage for the amount of benefit realized upon ultimate settlement				50.00%