Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended		3 Months Ended	12 Months Ended
	Mar. 31, 2014 USD ($) $ / shares shares	Feb. 28, 2014 USD ($)	Mar. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) Segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Significant Accounting Policies [Line Items]
Accumulated deficit				$ (193,436,000)	$ (111,259,000)
Working capital				$ 175,800,000
Number of operating segment | Segment				1
Reverse stock split				1-for-11.5
Cash and cash equivalents maturity period				Three months or less
Cash and cash equivalents of restricted cash held for credit cards					100,000
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
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	$ 9,600,000
IPO [Member]
Significant Accounting Policies [Line Items]
Warrants to purchase convertible preferred stock, exercise price | $ / shares	$ 21.00		$ 21.00
Remeasurement [Member]
Significant Accounting Policies [Line Items]
Expense related to change in fair value	$ 2,300,000
Reclassified to additional paid in capital	$ 2,800,000
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%	50.00%