Balance Sheet Components - Other Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2019	Oct. 17, 2019	Sep. 30, 2019	Jun. 30, 2019	Apr. 30, 2019	Apr. 26, 2019	Apr. 23, 2019	Mar. 31, 2019	Jul. 31, 2018	Aug. 31, 2017	Aug. 14, 2017	Aug. 08, 2017
Balance Sheet Components [Line Items]
Common stock, shares issued	78,004,669	62,083,000		5,714,286	5,714,286			5,263,158	789,473	5,263,158		4,500,000
Payment for debt issuance costs on long-term debt facility			$ 287
Amortization of debt discount	$ 457	$ 391	$ 154
Noncurrent assets	12,476	3,317
Evercord | Contingent consideration
Balance Sheet Components [Line Items]
Total consideration	4,700
Total consideration						$ 4,700
Noncurrent assets
Balance Sheet Components [Line Items]
Amortization of debt discount	200	100
Debt discount	$ 900
2017 Term Loan
Balance Sheet Components [Line Items]
Common stock, shares issued								25,000					300,000	300,000
Debt discount													$ 2,700
Debt instrument, fee amount													2,400		$ 300
Remaining borrowing capacity		$ 25,000						$ 50,000			$ 50,000		50,000		$ 25,000
2017 Term Loan | Noncurrent assets
Balance Sheet Components [Line Items]
Debt instrument, fee amount													$ 1,200
BGI
Balance Sheet Components [Line Items]
Agreement term	10 years
BGI | Sequencing products and services
Balance Sheet Components [Line Items]
Noncurrent assets	$ 10,000						$ 10,000