Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] - Myonexus Therapeutics, Inc. [Member] $ in Millions	Feb. 27, 2019 USD ($)
Subsequent Event [Line Items]
Final exercise price	$ 165.0
Additional development milestone payments to be paid	$ 200.0

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration