Stock-Based Compensation - Summary of Company's Stock Option Activity and Related Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Shares Available for Grant
Shares Available for Grant, Beginning balance	2,168,391
Shares Available for Grant, Additional options authorized	1,743,247
Shares Available for Grant, Options granted	(2,112,487)
Shares Available for Grant, Options cancelled	34,921
Shares Available for Grant, Ending balance	1,834,072	2,168,391
Number of Stock Options Outstanding
Number of Stock Options Outstanding, Beginning balance	6,127,291
Number of Stock Options Outstanding, Options granted	2,112,487
Number of Stock Options Outstanding, Options exercised	(230,733)
Number of Stock Options Outstanding, Options cancelled	(34,921)
Number of Stock Options Outstanding, Ending balance	7,974,124	6,127,291
Number of Stock Options Outstanding, Vested and exercisable	4,216,526
Number of Stock Options Outstanding, Vested and expected to vest	7,657,935
Weighted- Average Exercise Price
Weighted- Average Exercise Price, Beginning balance	$ 2.60
Weighted- Average Exercise Price, Options granted	5.10
Weighted- Average Exercise Price, Options exercised	0.84
Weighted- Average Exercise Price, Options cancelled	2.71
Weighted- Average Exercise Price, Ending balance	3.31	$ 2.60
Weighted- Average Exercise Price, Vested and exercisable	2.11
Weighted- Average Exercise Price, Vested and expected to vest	$ 3.26
Weighted- Average Remaining Contractual Life (Years)
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	7 years 8 months 12 days	7 years 3 months 19 days
Weighted- Average Remaining Contractual Life (Years), Vested and exercisable	6 years 6 months
Weighted- Average Remaining Contractual Life (Years), Vested and expected to vest	7 years 7 months 6 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 25,264	$ 7,800
Aggregate Intrinsic Value, Vested and exercisable	18,401
Aggregate Intrinsic Value, Vested and expected to vest	$ 24,669