Income Taxes - Effective Tax Rates (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective tax rates differing from U.S. federal statutory rate
U.S. Federal taxes (benefit) at statutory rate									$ (25,794,000)	$ (26,800,000)	$ (46,206,000)
State tax expense									(6,607,000)	(4,468,000)	(6,559,000)
Research and development credits									(1,645,000)	(1,164,000)	(1,149,000)
Stock-based compensation									(7,544,000)	(3,148,000)	(5,036,000)
Change in federal tax rate											44,701,000
Mark to market fair value adjustments										865,000	(390,000)
Nondeductible settlement for claims										1,000	3,873,000
Foreign tax differential									1,612,000	195,000	153,000
Other nondeductible items									1,378,000	690,000	856,000
Change in valuation allowance									40,599,000	34,150,000	10,211,000
Provision for income taxes	$ (14,000)	$ 44,000	$ 1,895,000	$ 74,000	$ (14,000)	$ 118,000	$ 113,000	$ 104,000	$ 1,999,000	$ 321,000	$ 454,000
U.S. Federal taxes (benefit) at statutory rate (as a percent)									(21.00%)	(21.00%)	(34.00%)
State tax expense (as a percent)									(5.38%)	(3.50%)	(4.83%)
Research and development credits (as a percent)									(1.34%)	(0.91%)	(0.85%)
Stock-based compensation (as a percent)									(6.14%)	(2.47%)	(3.71%)
Change in federal tax rate									0.00%	0.00%	32.89%
Mark to market fair value adjustments (as a percent)									0.00%	0.68%	(0.29%)
Nondeductible settlement for claims (as a percent)									0.00%	0.00%	2.85%
Foreign tax differential (as a percent)									1.31%	0.15%	0.11%
Other nondeductible items (as a percent)									1.12%	0.54%	0.63%
Change in valuation allowance (as a percent)									33.06%	26.76%	7.51%
Provision for income taxes (as a percent)									1.63%	0.25%	0.31%
Income tax expense	$ (14,000)	$ 44,000	$ 1,895,000	$ 74,000	$ (14,000)	$ 118,000	$ 113,000	$ 104,000	$ 1,999,000	$ 321,000	$ 454,000
Foreign income tax expense									1,900,000	200,000	300,000
State income tax expense									41,000	$ 100,000	$ 200,000
Clinical testing and software licensing
Effective tax rates differing from U.S. federal statutory rate
Foreign income tax expense									$ 100,000