For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Customers Accounted for 10% or More of Total Net Revenues (Detail) - Customer Concentration Risk - Net Revenues	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")
Concentration Risk [Line Items]
Concentration risk percentage	19.00%	29.00%	27.00%
Daiichi Sankyo, Inc ("Daiichi")
Concentration Risk [Line Items]
Concentration risk percentage	16.00%	33.00%	29.00%
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")
Concentration Risk [Line Items]
Concentration risk percentage		22.00%	19.00%
Dermavant Sciences GmbH ("Dermavant")
Concentration Risk [Line Items]
Concentration risk percentage		16.00%	25.00%