Balance Sheet Components - Other Assets (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended		15 Months Ended
	Feb. 28, 2019	Apr. 30, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Apr. 30, 2019	Dec. 31, 2018	Aug. 31, 2017	Aug. 08, 2017
Balance Sheet Components [Line Items]
Agreement term		4 years
Total consideration		$ 3,200
Deferred costs included in other long-term assets			$ 400		$ 400		$ 400		$ 1,000
Amortization of deferred costs							$ 200
Cost of revenues			$ 40,138	$ 39,477	$ 123,125	$ 117,736
Common stock, shares issued			70,850,000		70,850,000		70,850,000		62,083,000
Amortization of debt discount			$ 100	$ 100	$ 336	293
Debt discount			900		900		$ 900
Noncurrent assets			12,679		12,679		12,679		$ 3,317
2017 Term Loan
Balance Sheet Components [Line Items]
Common stock, shares issued								25,000		300,000
Debt instrument, fee amount			3,200		3,200		3,200
Remaining borrowing capacity									$ 50,000	$ 50,000	$ 25,000
2017 Term Loan | Direct reduction from outstanding debt balance
Balance Sheet Components [Line Items]
Debt instrument, fee amount											$ 2,000
2017 Term Loan | Noncurrent assets
Balance Sheet Components [Line Items]
Debt instrument, fee amount			1,200		1,200		1,200			$ 1,200
Health Insurance Carrier Agreement
Balance Sheet Components [Line Items]
Cost of revenues					600	$ 600
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		$ 10,000