Balance Sheet Components - Other Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Oct. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Apr. 30, 2019	Jul. 31, 2018	Aug. 31, 2017	Aug. 08, 2017
Balance Sheet Components [Line Items]
Common stock, shares issued	86,223,000	78,005,000		4,791,665	5,714,286			5,263,158	4,500,000
Amortization of debt discount and issuance cost	$ 149	$ 457	$ 391
Noncurrent assets	14,743	12,476
Evercord
Balance Sheet Components [Line Items]
Accounts receivable		5,782				$ 1,000
Estimated consideration		$ 15,377				15,400
Evercord | Contingent consideration
Balance Sheet Components [Line Items]
Total consideration						$ 4,700
Noncurrent assets
Balance Sheet Components [Line Items]
Debt discount	0
Long-term Debt
Balance Sheet Components [Line Items]
Debt discount	900
2017 Term Loan
Balance Sheet Components [Line Items]
Common stock, shares issued		25,000						25,000		300,000
Remaining borrowing capacity		$ 50,000								$ 50,000	$ 25,000
2017 Term Loan | Noncurrent assets
Balance Sheet Components [Line Items]
Debt instrument, fee amount										$ 1,200
BGI Genomics | Sequencing products and services
Balance Sheet Components [Line Items]
Noncurrent assets	$ 10,000						$ 10,000