Stock-Based Compensation - Summary of Options Outstanding and Vested Pricing of Exercise Prices (Detail) - Employee Stock Option	12 Months Ended
	Dec. 31, 2016 $ / shares shares
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Outstanding, Number Outstanding	6,307,384
Options Outstanding, Weighted-Average Life (in Years)	6 years 4 months 24 days
Options Outstanding, Number Exercisable	5,210,756
Options Outstanding, Weighted- Average Life (in years)	7 years 3 months 18 days
$0.22
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 0.22
Options Outstanding, Number Outstanding	134,807
Options Outstanding, Weighted-Average Life (in Years)	7 years 2 months 12 days
Options Outstanding, Number Exercisable	134,807
Options Outstanding, Weighted- Average Life (in years)	7 years 2 months 12 days
$0.42
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 0.42
Options Outstanding, Number Outstanding	589,660
Options Outstanding, Weighted-Average Life (in Years)	7 years 10 months 24 days
Options Outstanding, Number Exercisable	589,660
Options Outstanding, Weighted- Average Life (in years)	7 years 10 months 24 days
$1.76
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 1.76
Options Outstanding, Number Outstanding	999,682
Options Outstanding, Weighted-Average Life (in Years)	8 years
Options Outstanding, Number Exercisable	999,682
Options Outstanding, Weighted- Average Life (in years)	8 years
$2.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 2.00
Options Outstanding, Number Outstanding	1,276,285
Options Outstanding, Weighted-Average Life (in Years)	8 years 1 month 6 days
Options Outstanding, Number Exercisable	1,221,126
Options Outstanding, Weighted- Average Life (in years)	8 years 1 month 6 days
$2.20
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 2.20
Options Outstanding, Number Outstanding	1,851,500
Options Outstanding, Weighted-Average Life (in Years)	2 years 2 months 12 days
Options Outstanding, Number Exercisable	810,031
Options Outstanding, Weighted- Average Life (in years)	2 years 2 months 12 days
$ 25.00
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Exercise Prices | $ / shares	$ 25.00
Options Outstanding, Number Outstanding	1,455,450
Options Outstanding, Weighted-Average Life (in Years)	8 years 7 months 6 days
Options Outstanding, Number Exercisable	1,455,450
Options Outstanding, Weighted- Average Life (in years)	8 years 7 months 6 days