Stockholders' Equity - Warrants Outstanding To Purchase Shares (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Class of Stock [Line Items]
Warrant Exercise Price (in dollars per share) | $ / shares	$ 6.00
Shares Subject to purchase at December 31, 2018 | shares	2,340,828
Warrant 1
Class of Stock [Line Items]
Warrant Exercise Price (in dollars per share) | $ / shares	$ 3.33
Expiration Date	Jun. 23, 2020
Shares Subject to purchase at December 31, 2018 | shares	702,247
Warrant 2
Class of Stock [Line Items]
Warrant Exercise Price (in dollars per share) | $ / shares	$ 9.00
Expiration Date	May 18, 2019
Shares Subject to purchase at December 31, 2018 | shares	1,605,131
Warrant 3
Class of Stock [Line Items]
Warrant Exercise Price (in dollars per share) | $ / shares	$ 10.00
Expiration Date	Nov. 21, 2019
Shares Subject to purchase at December 31, 2018 | shares	33,450