Stock Incentive Plans - Summary of Additional Information on Stock Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Number of Options Outstanding, Shares | shares	5,613,057
Options Outstanding Weighted-average Remaining Contractual Life (years)	8 years 11 months 19 days
Options Outstanding Weighted Average Exercise Price	$ 0.83
Number of Option Exercisable, Shares | shares	1,636,664
Options Exercisable Weighted Average Exercise Price	$ 0.93
Range One [Member]
Range of Exercise Prices, Lower	0.31
Range of Exercise Prices, Upper	$ 0.98
Number of Options Outstanding, Shares | shares	4,965,000
Options Outstanding Weighted-average Remaining Contractual Life (years)	8 years 7 months 28 days
Options Outstanding Weighted Average Exercise Price	$ 0.64
Number of Option Exercisable, Shares | shares	1,467,500
Options Exercisable Weighted Average Exercise Price	$ 0.73
Range Two [Member]
Range of Exercise Prices, Upper	$ 1.00
Number of Options Outstanding, Shares | shares	7,000
Options Outstanding Weighted-average Remaining Contractual Life (years)	2 years 10 months 17 days
Options Outstanding Weighted Average Exercise Price	$ 1.00
Number of Option Exercisable, Shares | shares	7,000
Options Exercisable Weighted Average Exercise Price	$ 1.00
Range Three [Member]
Range of Exercise Prices, Lower	1.50
Range of Exercise Prices, Upper	$ 1.80
Number of Options Outstanding, Shares | shares	493,207
Options Outstanding Weighted-average Remaining Contractual Life (years)	8 years 8 months 5 days
Options Outstanding Weighted Average Exercise Price	$ 1.79
Number of Option Exercisable, Shares | shares	134,314
Options Exercisable Weighted Average Exercise Price	$ 1.78
Range Four [Member]
Range of Exercise Prices, Lower	2.60
Range of Exercise Prices, Upper	$ 8.20
Number of Options Outstanding, Shares | shares	135,200
Options Outstanding Weighted-average Remaining Contractual Life (years)	3 years 6 months 7 days
Options Outstanding Weighted Average Exercise Price	$ 2.77
Number of Option Exercisable, Shares | shares	15,200
Options Exercisable Weighted Average Exercise Price	$ 4.48
Range Five [Member]
Range of Exercise Prices, Lower	10.70
Range of Exercise Prices, Upper	$ 22.00
Number of Options Outstanding, Shares | shares	12,650
Options Outstanding Weighted-average Remaining Contractual Life (years)	9 months
Options Outstanding Weighted Average Exercise Price	$ 10.92
Number of Option Exercisable, Shares | shares	12,650
Options Exercisable Weighted Average Exercise Price	$ 10.92