Income Taxes - Effective Tax Rates (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective tax rates differing from U.S. federal statutory rate
U.S. Federal taxes (benefit) at statutory rate	$ (48,226,000)	$ (25,794,000)	$ (26,800,000)
State tax expense	(10,672,000)	(6,607,000)	(4,468,000)
Research and development credits	(3,964,000)	(1,645,000)	(1,164,000)
Stock-based compensation	(23,791,000)	(7,544,000)	(3,148,000)
Mark to market fair value adjustments			865,000
Nondeductible settlement for claims			1,000
Foreign tax	55,000	1,612,000	195,000
Other nondeductible items	9,776,000	1,378,000	690,000
Change in valuation allowance	76,920,000	40,599,000	34,150,000
Provision for income taxes	$ 98,000	$ 1,999,000	$ 321,000
U.S. Federal taxes (benefit) at statutory rate (as a percent)	(21.00%)	(21.00%)	(21.00%)
State tax expense (as a percent)	(4.65%)	(5.38%)	(3.50%)
Research and development credits (as a percent)	(1.73%)	(1.34%)	(0.91%)
Stock-based compensation (as a percent)	(10.36%)	(6.14%)	(2.47%)
Change in federal tax rate	0.00%	0.00%	0.00%
Mark to market fair value adjustments (as a percent)	0.00%	0.00%	0.68%
Nondeductible settlement for claims (as a percent)	0.00%	0.00%	0.00%
Foreign tax differential (as a percent)	0.02%	1.31%	0.15%
Other nondeductible items (as a percent)	4.26%	1.12%	0.54%
Change in valuation allowance (as a percent)	33.50%	33.06%	26.76%
Provision for income taxes (as a percent)	0.04%	1.63%	0.25%
Income tax expense	$ 98,000	$ 1,999,000	$ 321,000
Foreign withholding tax expense		1,900,000
Foreign income tax expense		100,000	200,000
State income tax expense	9,000	$ 40,000.00	$ 100,000
Clinical testing and software licensing
Effective tax rates differing from U.S. federal statutory rate
Foreign income tax expense	$ 100,000