Stockholders' Equity - Common Stock Warrants (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right
Number of Warrants	5,098,916	2,768,882
Warrant exercise price per share	$ 0.75	$ 0.08
Warrants
Class of Warrant or Right
Warrant exercise price per share	1.52
Preferred stock
Class of Warrant or Right
Warrant exercise price per share	$ 152.00
Liability Classified Warrants
Class of Warrant or Right
Number of Warrants	2,368,400
December 2019 Series B1 warrants
Class of Warrant or Right
Number of Warrants	2,368,400
Warrant exercise price per share	$ 1.52
Equity Classified Warrants
Class of Warrant or Right
Number of Warrants	2,730,516	2,768,882
May 2013 Warrants
Class of Warrant or Right
Number of Warrants	1,949,754	1,977,041
Warrant exercise price per share	$ 0.08	$ 0.08
September 2013 Warrants
Class of Warrant or Right
Number of Warrants	514,756	521,997
Warrant exercise price per share	$ 0.08	$ 0.08
February 2014 Warrants
Class of Warrant or Right
Number of Warrants	266,006	269,844
Warrant exercise price per share	$ 0.08	$ 0.08