Stockholders' Equity - Common Stock Warrant Activity (Details)	9 Months Ended
	Sep. 30, 2021 $ / shares shares
Stockholders' Equity
Outstanding warrants, beginning of period | shares	16,967,828
Exercised | shares	(5,867,198)
Expired | shares	(2,368,400)
Outstanding warrants, end of period | shares	8,732,230
Warrant exercise price per share, beginning of period | $ / shares	$ 1.28
Exercised | $ / shares	$ 0.04
Warrant exercise price per share, expired | $ / shares	1.52
Warrants exercise price per share, end of period | $ / shares	$ 2.04