CONDENSED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Beginning Balance at Dec. 31, 2019	$ (30,553)	$ (34)	$ 11	$ 7,621	$ (38,185)	$ (34)
Beginning Balance, Shares at Dec. 31, 2019			1,070
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Contributions from PDL	$ 1,519			1,519
Distributions to PDL	(97)			(97)
Settlement of phantom stock-based awards	783			783
Net loss	(3,686)				(3,686)
Ending Balance at Mar. 31, 2020	(32,068)		$ 11	9,826	(41,905)
Ending Balance, Shares at Mar. 31, 2020			1,070
Beginning Balance at Dec. 31, 2020	$ 67,210		$ 109	125,094	(57,993)
Beginning Balance, Shares at Dec. 31, 2020			10,933
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201912Member
Stock-based compensation	$ 2,301			2,301
Net loss	(5,182)				(5,182)
Ending Balance at Mar. 31, 2021	$ 64,329		$ 109	$ 127,395	$ (63,175)
Ending Balance, Shares at Mar. 31, 2021			10,933