Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Liabilities
Unrealized gains on investments	$ 62
Total Deferred Tax Liabilities	62
Deferred Tax Assets
Charitable Contributions	15	$ 13	$ 4
Accrued Expenses	759	498	421
Intangibles	983	477	579
Stock Compensation	10,943	4,395	605
Property, Plant & Equipment	13	9
Unrealized Loss on Investment		92	9
Net Operating Losses	17,635	14,851	9,229
Capitalized R&D	29,364	15,108	8,671
R&D Credit	6,141	3,505	1,901
Total deferred tax assets before valuation allowance	65,853	38,948	21,419
Valuation Allowance	(65,791)	$ (38,948)	$ (21,419)
Total deferred tax assets	$ 62