Share-Based Compensation - Schedule of Share-Based Compensation Recognized in Consolidated Statements of Operations (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 7.5	$ 6.9	$ 15.2	$ 13.3	[1]
Molecular Diagnostic Testing Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	0.2	0.2	0.3	0.3
Pharmaceutical and Clinical Services Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	0.0		0.1	0.1
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	1.1	1.2	2.3	2.1
Selling, General, and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 6.2	$ 5.5	$ 12.5	$ 10.8

[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 contained in Part I, Item 1 of this report for additional information.