Balance Sheet Components - Other Accured Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Mar. 31, 2018	Mar. 07, 2018	Dec. 31, 2017
Balance Sheet Components
Settlement accrued for reimbursement related claims	$ 1,378			$ 10,062
Reserves for refunds to third-party payers	10,012			6,794
Accrued charges for outsourced testing	5,001			6,566
Testing and laboratory materials from suppliers	2,742			1,367
Marketing and corporate affairs	1,306			1,456
Legal, audit and consulting fees	1,058			206
Accrued shipping charges	852			198
Sales tax payable	1,255			504
Accrued specimen service fees	1,378			683
Accrued rent	903			856
Clinical trials and studies	1,694			483
Other accrued expenses	4,863			4,082
Total other accrued liabilities	32,442			33,257
Accrued interest	200
Accrued settlement liability	1,400		$ 11,400	11,400
Accrued settlement liability, current				10,100
Accrued settlement liability, long-term				$ 1,300
Settlement agreement, amount plus applicable interest to be paid in installments		$ 5,300	$ 5,300
Quarterly installments	4,200
Quarterly installment, separate amount	800
Additional reserves for refunds to insurance carriers	10,300
Revenue recognized	$ 3,300