Statements of Changes in Stockholders' Deficit - USD ($) $ in Thousands	ATM Agreement Sales [Member] Preferred Stock [Member] Series A Convertible Preferred Stock [Member]	ATM Agreement Sales [Member] Preferred Stock [Member] Series B-1 Convertible Preferred Stock [Member]	ATM Agreement Sales [Member] Preferred Stock [Member] Series B-2 Convertible Preferred Stock [Member]	ATM Agreement Sales [Member] Undesignated Preferred Stock [Member]	ATM Agreement Sales [Member] Common Stock [Member]	ATM Agreement Sales [Member] Additional Paid-in Capital [Member]	ATM Agreement Sales [Member] Retained Earnings [Member]	ATM Agreement Sales [Member]	Deerfield Convertible Notes [Member] Preferred Stock [Member] Series A Convertible Preferred Stock [Member]	Deerfield Convertible Notes [Member] Preferred Stock [Member] Series B-1 Convertible Preferred Stock [Member]	Deerfield Convertible Notes [Member] Preferred Stock [Member] Series B-2 Convertible Preferred Stock [Member]	Deerfield Convertible Notes [Member] Undesignated Preferred Stock [Member]	Deerfield Convertible Notes [Member] Common Stock [Member]	Deerfield Convertible Notes [Member] Additional Paid-in Capital [Member]	Deerfield Convertible Notes [Member] Retained Earnings [Member]	Deerfield Convertible Notes [Member]	Underwriting Public Offering [Member] Preferred Stock [Member] Series A Convertible Preferred Stock [Member]	Underwriting Public Offering [Member] Preferred Stock [Member] Series B-1 Convertible Preferred Stock [Member]	Underwriting Public Offering [Member] Preferred Stock [Member] Series B-2 Convertible Preferred Stock [Member]	Underwriting Public Offering [Member] Undesignated Preferred Stock [Member]	Underwriting Public Offering [Member] Common Stock [Member]	Underwriting Public Offering [Member] Additional Paid-in Capital [Member]	Underwriting Public Offering [Member] Retained Earnings [Member]	Underwriting Public Offering [Member]	Equity Line of Credit [Member] Preferred Stock [Member] Series A Convertible Preferred Stock [Member]	Equity Line of Credit [Member] Preferred Stock [Member] Series B-1 Convertible Preferred Stock [Member]	Equity Line of Credit [Member] Preferred Stock [Member] Series B-2 Convertible Preferred Stock [Member]	Equity Line of Credit [Member] Undesignated Preferred Stock [Member]	Equity Line of Credit [Member] Common Stock [Member]	Equity Line of Credit [Member] Additional Paid-in Capital [Member]	Equity Line of Credit [Member] Retained Earnings [Member]	Equity Line of Credit [Member]	Optional Exchange Principal Amount [Member] Preferred Stock [Member] Series A Convertible Preferred Stock [Member]	Optional Exchange Principal Amount [Member] Preferred Stock [Member] Series B-1 Convertible Preferred Stock [Member]	Optional Exchange Principal Amount [Member] Preferred Stock [Member] Series B-2 Convertible Preferred Stock [Member]	Optional Exchange Principal Amount [Member] Undesignated Preferred Stock [Member]	Optional Exchange Principal Amount [Member] Common Stock [Member]	Optional Exchange Principal Amount [Member] Additional Paid-in Capital [Member]	Optional Exchange Principal Amount [Member] Retained Earnings [Member]	Optional Exchange Principal Amount [Member]	Convertible Notes 2021 [Member] Preferred Stock [Member] Series A Convertible Preferred Stock [Member]	Convertible Notes 2021 [Member] Preferred Stock [Member] Series B-1 Convertible Preferred Stock [Member]	Convertible Notes 2021 [Member] Preferred Stock [Member] Series B-2 Convertible Preferred Stock [Member]	Convertible Notes 2021 [Member] Undesignated Preferred Stock [Member]	Convertible Notes 2021 [Member] Common Stock [Member]	Convertible Notes 2021 [Member] Additional Paid-in Capital [Member]	Convertible Notes 2021 [Member] Retained Earnings [Member]	Convertible Notes 2021 [Member]	Preferred Stock [Member] Series A Convertible Preferred Stock [Member]	Preferred Stock [Member] Series B-1 Convertible Preferred Stock [Member]	Preferred Stock [Member] Series B-2 Convertible Preferred Stock [Member]	Undesignated Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2017																																																					$ 1	$ 107,209	$ (164,726)	$ (57,516)
Net loss																																																							(56,466)	(56,466)
Stock-based compensation expense																																																						6,495		6,495
Issuance of common stock					$ 1	$ 4,827		$ 4,828													$ 1	$ 23,499		$ 23,500
Offering expenses charged to equity																																																						(554)		(554)
Conversion of principal and interest on Deerfield Convertible Note														$ 3,502		$ 3,502																														$ 9,577		$ 9,577
Exercise of stock options																																																						68		68
Balance at Dec. 31, 2018																																																					3	154,623	(221,192)	(66,566)
Net loss																																																							(24,522)	(24,522)
Stock-based compensation expense																																																						4,410		4,410
Issuance of common stock																														$ 5,446		$ 5,446					$ 1	$ 1,199		$ 1,200
Offering expenses charged to equity																																																						(151)		(151)
Conversion of principal and interest on Deerfield Convertible Note																																														$ 3,000		$ 3,000
Change in fair value of embedded conversion feature in connection with debt modification																																																						2,311		2,311
Deferred offering costs																														$ 300		$ 300																						116		116
Balance at Dec. 31, 2019																																																					$ 4	$ 171,254	$ (245,714)	$ (74,456)