Business Combinations and Contingent Consideration - Change in Fair Value of Contingent Consideration Related to Acquisitions (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Talon Therapeutics, Inc. [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
December 31, 2015	$ 1,377
Fair value adjustment for the three months ended March 31, 2016	269
March 31, 2016	1,646
Ligand Pharmaceuticals Inc [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
December 31, 2015	5,227
Fair value adjustment for the three months ended March 31, 2016	773
March 31, 2016	$ 6,000