Business Combinations and Contingent Consideration - Change in Fair Value of Contingent Consideration Related to Acquisitions (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($)
Change in Fair Value of Contingent Consideration [Roll Forward]
Beginning	$ 21,352
Ending	14,445
Talon Therapeutics, Inc. [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
Beginning	1,377
Fair value adjustment for the three months ended March 31, 2016	(124)
Ending	1,253
Contingent Consideration [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
Payment to Ligand in April 2016 for FDA approval milestone achievement	(6,000)
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
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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66048111&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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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