Warrants - IPO Narrative (Details) $ in Millions		12 Months Ended
	Oct. 16, 2018 USD ($) shares	Dec. 31, 2018 shares	Dec. 31, 2017 shares
Class of Warrant or Right [Line Items]
Warrants to purchase shares of stock (in shares)			280,876
Adjustments to additional paid-in capital related to warrants | $	$ 1.2
Redeemable Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Warrants to purchase shares of stock (in shares)		0	156,550
Redeemable Convertible Preferred Stock | Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Number of warrants converted (in shares)	156,550
Warrants to purchase shares of stock (in shares)			156,550
Common Stock
Class of Warrant or Right [Line Items]
Warrants to purchase shares of stock (in shares)	160,657	118,122	124,326
Series 6 Preferred Stock | Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Warrant conversion ratio		0.9433