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Collaboration Agreements - Summary of Revenue Recognized Under the Collaboration Agreements - Additional Information 4 (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
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Jun. 30, 2018 | Jun. 30, 2018
Japan [Member] |  |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |  |
Remainder of transaction price, variable consideration from estimated future co-development billing |  | $ 2.6
Europe [Member] |  |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |  |
Remainder of transaction price, variable consideration from estimated future co-development billing |  | 23.9
U.S./RoW and China [Member] |  |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |  |
Remainder of transaction price, variable consideration from estimated future co-development billing |  | 251.3
Astellas Agreement [Member] | Japan [Member] |  |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |  |
Changes in revenue due to prior period adjustment | $ 14.9 | 14.9
Astellas Agreement [Member] | Europe [Member] |  |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |  |
Changes in revenue due to prior period adjustment |  | (0.2)
AstraZeneca Agreements [Member] | U.S./RoW and China [Member] |  |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |  |
Changes in revenue due to prior period adjustment |  | $ (0.3)

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- Definition Amount of revenue recognized arising from contract liability from change in timeframe for performance obligation to be satisfied. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130551-203045 + Details
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- Details
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