Balance Sheet Components - Other Accured Liabilities (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Mar. 07, 2018	Dec. 31, 2017
Balance Sheet Components
Settlement accrued for reimbursement related claims			$ 1,378
Reserves for refunds to third-party payers		$ 10,897	10,012
Accrued charges for outsourced testing		5,993	5,001
Testing and laboratory materials from suppliers		2,253	2,742
Marketing and corporate affairs		2,112	1,306
Legal, audit and consulting fees		2,082	1,058
Accrued shipping charges		255	852
Sales tax payable		906	1,255
Accrued specimen service fees		1,355	1,378
Accrued rent			903
Clinical trials and studies		1,310	1,694
Operating lease liabilities, current portion		5,339
Other accrued expenses		6,655	4,863
Total other accrued liabilities		39,157	32,442
Accrued settlement liability			1,400	$ 11,400	$ 11,400
Settlement agreement, amount plus applicable interest to be paid in installments				$ 5,300
Additional reserves for refunds to insurance carriers		4,800
Settlement agreement installment paid	$ 1,400		$ 10,300
Revenue recognized		700
Overpayments from insurance carriers		$ 3,900