Income Taxes - Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 31,302	$ 30,275
Amortization	3,701	11,602
Stock based compensation	2,626	3,577
Accounts receivable	0	53
Fair value contingent consideration	0	264
Orphan drug and R&D tax credit	2,793	0
Other	423	901
Gross deferred tax assets	40,845	46,672
Deferred tax liabilities:
Amortization	0	(172)
Prepaid expenses	(75)	(35)
Other	(890)	0
Gross deferred tax liabilities	(965)	(207)
Less: valuation allowances	(21,624)	(17,038)
Net deferred tax assets	$ 18,256	$ 29,427