Basis of Presentation and Summary of Significant Accounting Policies (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Potential shares excluded from diluted net loss per share	26,169,530	19,851,451
Options to Purchase Common Stock [Member]
Potential shares excluded from diluted net loss per share	15,841,000	15,081,000
Convertible Preferred Stock [Member]
Potential shares excluded from diluted net loss per share	4,828,530	4,828,530
Warrants to Purchase Common Stock [Member]
Potential shares excluded from diluted net loss per share	5,500,000	4,500,000
Common Stock Subject to Repurchase [Member]
Potential shares excluded from diluted net loss per share		(507,079)