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Acquisitions - Additional Information (Detail) - Counsyl Inc [Member] $ / shares in Units, $ in Millions |  | 3 Months Ended | 18 Months Ended
--- | --- | --- | ---
Jul. 31, 2018 USD ($) $ / shares shares | Dec. 31, 2018 USD ($) | Mar. 31, 2020 USD ($)
Business Acquisition [Line Items] |  |  |
Business acquisition consideration | $ 405.9 |  |
Acquisition costs | 6.8 |  |
Goodwill, working capital adjustment reduction |  | $ (1.1) | $ (1.1)
Acquired intangible assets | 290.0 |  |
Developed Screening Processes [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Acquired intangible assets | $ 290.0 |  |
Intangible assets estimated useful lives | 12 years |  |
Developed Screening Processes [Member] | Measurement Input, Discount Rate [Member] |  |  |
Business Acquisition [Line Items] |  |  |
Estimated net cash flows, discount rate | 12.5 |  |
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 |  |
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 |  |

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