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, 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
Ending Balance at Jun. 30, 2020	$ (36,275)		$ 11	10,116	(46,402)
Ending Balance, Shares at Jun. 30, 2020			1,070
Beginning Balance at Mar. 31, 2020	(32,068)		$ 11	9,826	(41,905)
Beginning Balance, Shares at Mar. 31, 2020			1,070
Contributions from PDL	290			290
Net loss	(4,497)				(4,497)
Ending Balance at Jun. 30, 2020	(36,275)		$ 11	10,116	(46,402)
Ending Balance, Shares at Jun. 30, 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
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
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
Ending Balance at Jun. 30, 2021	$ 61,628		$ 110	129,055	(67,537)
Ending Balance, Shares at Jun. 30, 2021			10,957
Beginning Balance at Mar. 31, 2021	64,329		$ 109	127,395	(63,175)
Beginning Balance, Shares at Mar. 31, 2021			10,933
Issuance of common stock under the 2020 ESPP	170		$ 1	169
Issuance of common stock under the 2020 ESPP, Shares			24
Stock-based compensation	1,491			1,491
Net loss	(4,362)				(4,362)
Ending Balance at Jun. 30, 2021	$ 61,628		$ 110	$ 129,055	$ (67,537)
Ending Balance, Shares at Jun. 30, 2021			10,957