Business Acquisitions - Additional Information (Detail) $ / shares in Units, $ in Millions		9 Months Ended	12 Months Ended
	Jul. 31, 2018 USD ($) $ / shares shares	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)
Business Acquisition [Line Items]
Goodwill, working capital adjustment reduction			$ 4.4	$ 1.9
Counsyl Inc [Member]
Business Acquisition [Line Items]
Business acquisition consideration	$ 405.9
Goodwill, working capital adjustment reduction		$ (1.1)	(1.1)
Intangible assets reduction due to assumptions related to contributory asset charges		2.9	2.9
Decrease in deferred tax liabilities		1.9	1.9
Fair value equipment reduction		0.7	0.7
Increase in goodwill			4.4
Acquired intangible assets	$ 290.0
Acquisition costs		$ 6.8	6.8
Revenue contributed by acquired entity			104.9
Operating expenses related to acquired entity			$ 67.6
Counsyl Inc [Member] | Measurement Input, Discount Rate [Member]
Business Acquisition [Line Items]
Estimated net cash flows, discount rate	12.5
Counsyl Inc [Member] | Developed Screening Processes [Member]
Business Acquisition [Line Items]
Acquired intangible assets	$ 290.0
Intangible assets estimated useful lives	12 years
Counsyl Inc [Member] | Agreement and Plan of Merger [Member]
Business Acquisition [Line Items]
Effective date of business acquisition	Jul. 31, 2018
Business acquisition consideration	$ 405.9
Cash payment on business acquisition	278.5
Amount of cash consideration deposited in escrow account	$ 5.0
Counsyl Inc [Member] | Agreement and Plan of Merger [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Business acquisition, shares issued | shares	2,994,251
Business acquisition, shares issued, value	$ 127.4
Business acquisition, per share market closing price | $ / shares	$ 42.53