Warrants - Warrant activity (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Warrant Activity
Warrants outstanding, beginning balance	34,682	4,590
Issuances	19,387,761	12,713
Expirations and cancellations	(551)	(722)
Warrants outstanding, ending balance	19,421,892	16,581