Balance Sheet Components - Other Accured Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018	Mar. 07, 2018	Dec. 31, 2017
Settlement accrued for reimbursement related claims	$ 2,689	$ 2,689				$ 10,062
Reserves for refunds to third-party payers	8,367	8,367				6,794
Accrued charges for outsourced testing	4,663	4,663				6,566
Testing and laboratory materials from suppliers	1,918	1,918				1,367
Marketing and corporate affairs	1,578	1,578				1,456
Legal, audit and consulting fees	1,132	1,132				206
Accrued shipping charges	878	878				198
Sales tax payable	874	874				504
Accrued specimen service fees	1,308	1,308				683
Accrued rent	891	891				856
Clinical trials and studies	1,238	1,238				483
Other accrued expenses	5,531	5,531				4,082
Total other accrued liabilities	31,067	31,067				33,257
Accrued interest	200	200
Accrued settlement liability	2,700	2,700			$ 11,400	11,400
Accrued settlement liability, current						10,100
Accrued settlement liability, long-term						$ 1,300
Other accrued liabilities, current				$ 1,300
Settlement agreement, amount plus applicable interest to be paid in installments				$ 5,300	$ 5,300
Quarterly installment	2,800	2,800
Quarterly installment, separate amount			$ 800
Additional reserves for refunds to insurance carriers	1,800	6,900
Revenue recognized		700
Overpayments from insurance carriers		4,500
Insurance reserves based on claims submitted		2,400
Reserves from payers
Revenue recognized	$ 700	$ 2,500