Commitments and Contingencies (Details) $ in Millions		1 Months Ended	12 Months Ended
	Mar. 07, 2018 USD ($) installment	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2017 USD ($)
Other commitments
Accrued settlement liability	$ 11.4		$ 1.4		$ 11.4
Settlement agreement, amount plus applicable interest to be paid in installments	$ 5.3
Settlement agreement, number of equal quarterly installments | installment	4
Settlement amount		$ 1.4	5.3
Settlement agreement installment paid		$ 1.4	$ 10.3
Inventory material
Other commitments
Purchase commitment				$ 7.5
Gene sequencing data analysis commitment
Other commitments
Purchase commitment				0.9
Gene sequencing reagents and kits
Other commitments
Purchase commitment				1.1
Qualified specimen samples
Other commitments
Purchase commitment				0.3
Laboratory instruments
Other commitments
Purchase commitment				11.7
Another supplier | Inventory material
Other commitments
Purchase commitment				6.6
Supplier three | Biological sample processing and storage
Other commitments
Purchase commitment				0.3
Supplier Five | Genetic tests
Other commitments
Purchase commitment				7.2
Securities related claims
Other commitments
Estimate of possible loss				1.5
Commercial general liability claims
Other commitments
Estimate of possible loss				$ 0.3