Summary of Significant Accounting Policies - Anti-dilutive shares (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net Loss per Share
Total anti-dilutive shares outstanding	154,031,304	93,805,180
Stock-based awards
Net Loss per Share
Total anti-dilutive shares outstanding	29,827,858	18,918,008
2023 Notes
Net Loss per Share
Total anti-dilutive shares outstanding	5,224,594	6,672,500
PHC Notes
Net Loss per Share
Total anti-dilutive shares outstanding	65,757,177
2025 Notes
Net Loss per Share
Total anti-dilutive shares outstanding	39,689,142	63,018,091
Warrants
Net Loss per Share
Total anti-dilutive shares outstanding	13,532,533	5,196,581