Summary of Significant Accounting Policies - Net Loss per Share (Details) - USD ($) $ in Millions		3 Months Ended
	Mar. 26, 2020	Mar. 31, 2020	Mar. 31, 2019
Net Loss per Share
Total anti-dilutive shares outstanding		93,805,180	51,606,803
Percentage reduction of workforce	60.00%
Termination benefits		$ 1.6
Stock-based awards
Net Loss per Share
Total anti-dilutive shares outstanding		18,918,008	27,518,174
2023 Notes
Net Loss per Share
Total anti-dilutive shares outstanding		6,672,500	20,017,048
2025 Notes
Net Loss per Share
Total anti-dilutive shares outstanding		63,018,091
Warrants
Net Loss per Share
Total anti-dilutive shares outstanding		5,196,581	4,071,581