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Commitments and Contingencies - Additional Information (Detail) $ in Millions		1 Months Ended	12 Months Ended
	Jul. 18, 2019 USD ($)	Dec. 31, 2018 ft²	Jun. 30, 2018 Lease
Commitments and Contingencies [Line Items]
Lease, not yet commenced, description			in December 2018 we entered into a lease agreement for a building yet to be constructed which shall contain approximately 125,000 square feet of additional office space upon completion at our corporate headquarters. Construction began in July 2019 and we anticipate completion of the building during fiscal 2021.
Lease, not yet commenced, area of additional office space agreed to be leased \| ft²		125,000
Myriad RBM [Member]
Commitments and Contingencies [Line Items]
Non-cancelable operating leases			1
Operating leases expiration period			2020
Administrative Functions [Member] \| Minimum [Member]
Commitments and Contingencies [Line Items]
Operating leases expiration period			2019
Administrative Functions [Member] \| Maximum [Member]
Commitments and Contingencies [Line Items]
Operating leases expiration period			2024
Information Technology Equipment [Member]
Commitments and Contingencies [Line Items]
Non-cancelable operating leases			8
Operating leases expiration period			2020
Information Technology Equipment [Member] \| Maximum [Member]
Commitments and Contingencies [Line Items]
Operating leases expiration period			2021
Salt Lake City, Utah [Member]
Commitments and Contingencies [Line Items]
Non-cancelable operating leases			6
Salt Lake City, Utah [Member] \| Minimum [Member]
Commitments and Contingencies [Line Items]
Operating leases expiration period			2022
Salt Lake City, Utah [Member] \| Maximum [Member]
Commitments and Contingencies [Line Items]
Operating leases expiration period			2027
Germany [Member]
Commitments and Contingencies [Line Items]
Non-cancelable operating leases			1
Operating leases expiration period			2022
South San Francisco, California [Member]
Commitments and Contingencies [Line Items]
Non-cancelable operating leases			2
Operating leases expiration period			2025
Mason, Ohio and Toronto, Canada [Member]
Commitments and Contingencies [Line Items]
Non-cancelable operating leases			3
Mason, Ohio and Toronto, Canada [Member] \| Minimum [Member]
Commitments and Contingencies [Line Items]
Operating leases expiration period			2019
Mason, Ohio and Toronto, Canada [Member] \| Maximum [Member]
Commitments and Contingencies [Line Items]
Operating leases expiration period			2024
Subsequent Event [Member] \| Qui Tam Relator [Member]
Commitments and Contingencies [Line Items]
Settlement agreement date	July 18, 2019
Settlement amount \| $	$ 9.1