The cash outflow to acquire asset without physical form usually arising from contractual or other legal rights, excluding goodwill.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

Name:	us-gaap_PaymentsToAcquireIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Subsequent Event (Detail) $ in Millions			9 Months Ended
Subsequent Event (Detail) $ in Millions	Apr. 15, 2019 product	Mar. 01, 2019 product	Dec. 31, 2019 USD ($)
Subsequent Event [Line Items]
Number of products		7
ImmunGene, Inc. [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Number of products	2
Scenario, Forecast [Member] \| ImmunGene, Inc. [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Asset purchase agreement, upfront payment \| $			$ 3.0