Balance Sheet Components - Other Accured Liabilities (Details) $ in Thousands		3 Months Ended
	Mar. 07, 2018 USD ($) installment	Mar. 31, 2018 USD ($) installment	Dec. 31, 2017 USD ($)
Balance Sheet Components
Settlement accrued for reimbursement related claims		$ 6,074	$ 10,062
Reserves for refunds to insurance carriers		7,071	6,794
Accrued charges for third party test fees		7,301	6,566
Testing and laboratory materials from suppliers		1,653	1,367
Marketing and corporate affairs		1,223	1,456
Legal, audit and consulting fees		913	206
Accrued shipping charges		482	198
Sales tax payable		947	504
Accrued specimen service fees		1,026	683
Accrued rent		868	856
Clinical trials and studies		557	483
Other accrued expenses		3,408	4,082
Total other accrued liabilities		31,523	33,257
Accrued settlement liability	$ 11,400	7,100	11,400
Accrued settlement liability, current			10,100
Accrued settlement liability, long-term			$ 1,300
Additional reserves for refunds to insurance carriers		1,200
Revenue recognized		900
Other accrued liabilities, current		$ 1,300
Settlement agreement, number of equal quarterly installments | installment	4	4
Settlement agreement, amount plus applicable interest to be paid in installments	$ 5,300	$ 5,300