Balance Sheet Components - Other Accured Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Mar. 07, 2018	Dec. 31, 2017
Balance Sheet Components
Settlement accrued for reimbursement related claims	$ 3,921	$ 3,921				$ 10,062
Reserves for refunds to insurance carriers	8,310	8,310				6,794
Accrued charges for outsourced testing	5,725	5,725				6,566
Testing and laboratory materials from suppliers	2,346	2,346				1,367
Marketing and corporate affairs	1,190	1,190				1,456
Legal, audit and consulting fees	755	755				206
Accrued shipping charges	851	851				198
Sales tax payable	694	694				504
Accrued specimen service fees	1,083	1,083				683
Accrued rent	880	880				856
Clinical trials and studies	551	551				483
Other accrued expenses	4,214	4,214				4,082
Total other accrued liabilities	30,520	30,520				33,257
Accrued settlement liability					$ 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	1,300	1,300
Quarterly installment, separate amount			$ 800
Additional reserves for refunds to insurance carriers	3,300	5,100
Revenue recognized	900	1,800
Overpayments from insurance carriers	1,400	2,700
Insurance reserves based on claims submitted	$ 1,900	$ 2,400