Stockholder's Deficit - Schedule of Activity Under Equity Incentive Plan (Details) - 2008 Plan - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Balance, Shares available for grant	409,582
Increase authorization, Shares available for grant	6,250,000
Granted, Shares available for grant	(6,013,312)
Forfeited and expired, Shares available for grant	575,554
Balance, Shares available for grant	1,221,824	409,582
Balance, Number of shares	22,334,508
Granted, Number of shares	6,013,312
Exercised, Number of shares	(445,995)
Forfeited and expired, Number of shares	(575,554)
Balance, Number of shares	27,326,271	22,334,508
Balance, Weighted average exercise price	$ 3.66
Granted, Weighted average exercise price	7.47
Exercised, Weighted average exercise price	3.91
Forfeited and expired, Weighted average exercise price	5.49
Balance, Weighted average exercise price	$ 4.46	$ 3.66
Balance, Weighted average remaining contractual life	6 years 8 months 12 days	6 years 7 months 6 days
Granted, Weighted average grant date fair value per share	$ 3.48