Organization and Summary of Significant Accounting Policies - Schedule of Company's Revenue by Type (Detail) - USD ($) $ in Millions	3 Months Ended												12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	[1]	Mar. 31, 2018	[1]	Dec. 31, 2017	[1]	Sep. 30, 2017	[1]	Jun. 30, 2019	Jun. 30, 2018	[2]	Jun. 30, 2017	[2]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 215.4	$ 216.6	$ 216.8	$ 202.3	$ 193.9		$ 183.1		$ 187.9		$ 178.8		$ 851.1	$ 743.7	[1]	$ 728.7	[1]
Molecular Diagnostic - Hereditary Cancer Testing [Member]
Disaggregation Of Revenue [Line Items]
Total revenue													479.7	471.4		525.5
Molecular Diagnostic - GeneSight [Member]
Disaggregation Of Revenue [Line Items]
Total revenue													112.6	124.9		78.4
Molecular Diagnostic - Prenatal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue													104.9
Molecular Diagnostic- Vectra [Member]
Disaggregation Of Revenue [Line Items]
Total revenue													48.3	55.2		45.2
Molecular Diagnostic - Prolaris [Member]
Disaggregation Of Revenue [Line Items]
Total revenue													25.5	21.5		11.1
Molecular Diagnostic - EndoPredict [Member]
Disaggregation Of Revenue [Line Items]
Total revenue													10.4	8.8		7.7
Molecular Diagnostic - Other [Member]
Disaggregation Of Revenue [Line Items]
Total revenue													8.0	8.6		11.5
Molecular Diagnostic Testing [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	196.9	200.5	203.0	189.0	180.6		169.3		173.1		167.4		789.4	690.4	[1]	679.4	[1]
Pharmaceutical and Clinical Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 18.5	$ 16.1	$ 13.8	$ 13.3	$ 13.3		$ 13.8		$ 14.8		$ 11.4		$ 61.7	$ 53.3	[1]	$ 49.3	[1]

[1] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements of this report for additional information.

[2] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606)