v3.8.0.1

Development and Other Agreements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 10, 2015
Development Agreements [Line Items]
Issuance of common stock related to Verily Collaboration Agreement				$ 36.5
Development grant and other revenue		$ 0.0	$ 0.0	1.3
Verily Life Sciences [Member] | Collaborative Arrangement [Member]
Development Agreements [Line Items]
Collaborative Arrangement, Royalty Eligible Sales		$ 750.0
Collaborative Arrangement, Commitment Amount, Royalty Eligible Sales Threshold Not Achieved					$ 0.0
Verily Life Sciences [Member] | Collaborative Arrangement [Member] | Collaborative Arrangement, Milestone Payments [Member]
Development Agreements [Line Items]
Collaborative Arrangement, Development & Regulatory Milestones					65.0
Verily Life Sciences [Member] | Collaborative Arrangement [Member] | Initial Payment [Member]
Development Agreements [Line Items]
Collaborative Arrangement, Upfront Fee					$ 35.0
Issuance of common stock related to Verily Collaboration Agreement, shares	404,591
Share Price					$ 90.29
Research and Development Expense [Member] | Verily Life Sciences [Member] | Collaborative Arrangement [Member] | Initial Payment [Member]
Development Agreements [Line Items]
Issuance of common stock related to Verily Collaboration Agreement				$ 36.5

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- Definition

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