Business Combinations and Contingent Consideration - Change in Fair Value of Contingent Consideration Related to Acquisitions (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2016
Change in Fair Value of Contingent Consideration [Roll Forward]
Beginning	$ 18,658
Ending	16,342	$ 14,445
Talon Therapeutics, Inc. [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
Beginning	6,210
Fair value adjustment for the three months ended March 31, 2016	(1,865)
Ending	$ 4,345
Contingent Consideration [Member] \| Ligand Pharmaceuticals Inc [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
Beginning		5,227
Fair value adjustment for the three months ended March 31, 2016		773
Payment to Ligand in April 2016 for FDA approval milestone achievement		(6,000)
Ending		$ 0

Change in Fair Value of Contingent Consideration [Roll Forward]

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- Definition

Amount of gain (loss) recognized on the income statement for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- Definition

Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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