Revenue - Total Revenue by Category and by US versus Rest of World (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenue	$ 156.4	$ 167.3	$ 500.6	$ 529.8
U.S.
Disaggregation of Revenue [Line Items]
Total revenue	135.3	144.4	434.5	464.0
RoW
Disaggregation of Revenue [Line Items]
Total revenue	21.1	22.9	66.1	65.8
Molecular diagnostic testing
Disaggregation of Revenue [Line Items]
Total revenue	156.4	167.3	500.6	505.6
Molecular diagnostic testing | U.S.
Disaggregation of Revenue [Line Items]
Total revenue	135.3	144.4	434.5	439.8
Molecular diagnostic testing | RoW
Disaggregation of Revenue [Line Items]
Total revenue	21.1	22.9	66.1	65.8
Hereditary Cancer
Disaggregation of Revenue [Line Items]
Total revenue	70.5	79.4	220.6	241.5
Hereditary Cancer | U.S.
Disaggregation of Revenue [Line Items]
Total revenue	60.2	68.2	190.6	207.1
Hereditary Cancer | RoW
Disaggregation of Revenue [Line Items]
Total revenue	10.3	11.2	30.0	34.4
Tumor Profiling
Disaggregation of Revenue [Line Items]
Total revenue	30.8	32.9	96.9	94.4
Tumor Profiling | U.S.
Disaggregation of Revenue [Line Items]
Total revenue	20.2	21.3	61.4	63.4
Tumor Profiling | RoW
Disaggregation of Revenue [Line Items]
Total revenue	10.6	11.6	35.5	31.0
Prenatal
Disaggregation of Revenue [Line Items]
Total revenue	22.1	23.6	87.3	76.7
Prenatal | U.S.
Disaggregation of Revenue [Line Items]
Total revenue	21.9	23.5	86.7	76.3
Prenatal | RoW
Disaggregation of Revenue [Line Items]
Total revenue	0.2	0.1	0.6	0.4
Pharmacogenomics
Disaggregation of Revenue [Line Items]
Total revenue	33.0	24.1	95.5	64.3
Pharmacogenomics | U.S.
Disaggregation of Revenue [Line Items]
Total revenue	33.0	24.1	95.5	64.3
Pharmacogenomics | RoW
Disaggregation of Revenue [Line Items]
Total revenue	0.0	0.0	0.0	0.0
Autoimmune
Disaggregation of Revenue [Line Items]
Total revenue	0.0	7.3	0.3	28.2
Autoimmune | U.S.
Disaggregation of Revenue [Line Items]
Total revenue	0.0	7.3	0.3	28.2
Autoimmune | RoW
Disaggregation of Revenue [Line Items]
Total revenue	0.0	0.0	0.0	0.0
Other
Disaggregation of Revenue [Line Items]
Total revenue			0.0	0.5
Other | U.S.
Disaggregation of Revenue [Line Items]
Total revenue			0.0	0.5
Other | RoW
Disaggregation of Revenue [Line Items]
Total revenue			0.0	0.0
Pharmaceutical and clinical services
Disaggregation of Revenue [Line Items]
Total revenue	$ 0.0	$ 0.0	0.0	24.2
Pharmaceutical and clinical services | U.S.
Disaggregation of Revenue [Line Items]
Total revenue			0.0	24.2
Pharmaceutical and clinical services | RoW
Disaggregation of Revenue [Line Items]
Total revenue			$ 0.0	$ 0.0