Stockholders' Equity - Warrants (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Number of Warrants
Number of warrants, granted, arosa loan agreement		7,147,147
Weighted Average Exercise Price per Warrant
Weighted average exercise price per warrant, granted, arosa loan agreement
Warrant
Number of Warrants
Warrant or right, outstanding, number, beginning balance	17,818,844	2,618,307
Number of warrants, granted, marathon debt (in shares)	3,379,466	8,053,390
Number of warrants, exercised (in shares)	0	0
Number of warrants, granted, series B preferred stock (in shares)	9,262,500
Number of warrants, granted, other	66,966
Warrant or right, outstanding, number, beginning balance	30,527,776	17,818,844
Weighted Average Exercise Price per Warrant
Weighted average exercise price per warrant outstanding, beginning balance (in usd per share)	$ 1.84	$ 5.28
Weighted average exercise price per warrant, granted, marathon debt (in usd per share)
Weighted average exercise price per warrant, exercised (in usd per share)
Weighted average exercise price per warrant, granted, series B preferred stock (in usd per share)
Weighted average exercise price per warrant outstanding, ending balance (in usd per share)	$ 1.82	$ 1.84