Stockholders' Equity - Common Stock Warrants (Details) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Class of Warrant or Right
Number of Warrants	5,098,916	5,098,916
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
Liability Classified Warrants
Class of Warrant or Right
Number of Warrants	2,368,400	2,368,400
December 2019 Series B1 warrants
Class of Warrant or Right
Number of Warrants	2,368,400	2,368,400
Warrant exercise price per share	$ 1.52	$ 1.52
Equity Classified Warrants
Class of Warrant or Right
Number of Warrants	2,730,516	2,730,516
May 2013 Warrants
Class of Warrant or Right
Number of Warrants	1,949,754	1,949,754
Warrant exercise price per share	$ 0.08	$ 0.08
September 2013 Warrants
Class of Warrant or Right
Number of Warrants	514,756	514,756
Warrant exercise price per share	$ 0.08	$ 0.08
February 2014 Warrants
Class of Warrant or Right
Number of Warrants	266,006	266,006
Warrant exercise price per share	$ 0.08	$ 0.08