Preferred and Common Stock Warrants - Summary of Outstanding Warrants to Purchase Shares of Common Stock (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	13,656,871	5,146,400
Issuance On August 14, 2015
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	81,228
Exercise Price (in dollars per share)	$ 21.78
Issuance On August 14, 2015 | Series A Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		854,785
Exercise Price (in dollars per share)		$ 2.07
Issuance On August 21, 2015
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	69,603
Exercise Price (in dollars per share)	$ 21.78
Issuance On August 21, 2015 | Series A Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		732,453
Exercise Price (in dollars per share)		$ 2.07
Issuance On October 25, 2016
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	5,155
Exercise Price (in dollars per share)	$ 19.78
Issuance On October 25, 2016 | Series B Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		54,256
Exercise Price (in dollars per share)		$ 1.88
Issuance On November 1, 2017
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	130,609
Exercise Price (in dollars per share)	$ 19.78
Issuance On November 1, 2017 | Series B Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		1,374,435
Exercise Price (in dollars per share)		$ 1.88
Issuance On November 17, 2017
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	8,442
Exercise Price (in dollars per share)	$ 19.78
Issuance On November 17, 2017 | Series B Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		88,845
Exercise Price (in dollars per share)		$ 1.88
Issuance On December 4, 2017
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	5,661
Exercise Price (in dollars per share)	$ 19.78
Issuance On December 4, 2017 | Series B Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		59,576
Exercise Price (in dollars per share)		$ 1.88
Issuance On December 28, 2017
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	6,925
Exercise Price (in dollars per share)	$ 19.78
Issuance On December 28, 2017 | Series B Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		72,875
Exercise Price (in dollars per share)		$ 1.88
Issuance On December 28, 2017
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	115,916
Exercise Price (in dollars per share)	$ 19.78
Issuance On December 28, 2017 | Series B Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		1,219,815
Exercise Price (in dollars per share)		$ 1.88
Issuance On September 12, 2018
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	25,275
Exercise Price (in dollars per share)	$ 19.78
Issuance On September 12, 2018 | Series B Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		265,957
Exercise Price (in dollars per share)		$ 1.88
Issuance On September 12, 2018
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	20,220
Exercise Price (in dollars per share)	$ 19.78
Issuance On September 12, 2018 | Series B Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		212,765
Exercise Price (in dollars per share)		$ 1.88
Issuance On October 19, 2018
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	20,016
Exercise Price (in dollars per share)	$ 19.78
Issuance On October 19, 2018 | Series B Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)		210,638
Exercise Price (in dollars per share)		$ 1.88
Issuance On March 13, 2019
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	5,000
Exercise Price (in dollars per share)	$ 19.80
Issuance On April 16, 2019
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	3,866,154
Exercise Price (in dollars per share)	$ 13.20
Issuance On April 16, 2019
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	2,130,000
Exercise Price (in dollars per share)	$ 11.00
Issuance on November 29, 2019
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	5,416,667
Exercise Price (in dollars per share)	$ 15.00
Issuance on November 29, 2019
Class of Warrant or Right [Line Items]
Class of warrant or right, outstanding (in shares)	1,750,000
Exercise Price (in dollars per share)	$ 12.00