Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	May 01, 2020 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Significant Accounting Policies [Line Items]
Restricted cash	$ 700,000	$ 800,000
Cash and cash equivalents, restricted cash and restricted cash equivalents	40,740,000	130,426,000	$ 16,399,000			$ 23,789,000
Operating lease right-of-use asset	5,749,000	6,578,000
Total operating liability	5,040,000	6,771,000		$ 9,300,000
Goodwill	8,982,000	8,982,000
Goodwill impairment charges	$ 0	$ 0
Percentage of royalty payments	5.00%
Royalty payment period	10 years
Number of reportable segments | segment	1
Customer concentration risk | Genentech, Inc. | Revenue Benchmark
Significant Accounting Policies [Line Items]
Total gross revenue	100.00%	98.00%	100.00%
Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Operating lease right-of-use asset					$ 1,000,000
Total operating liability					$ 1,100,000