Business Combinations and Contingent Consideration - Change in Fair Value of Contingent Consideration Related to Acquisitions (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Talon Therapeutics, Inc. [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
Fair value, Beginning Balance	$ 2,379
Fair value adjustment for the year ended December 31, 2015	(1,002)
Fair value, Ending Balance	1,377
Ligand Pharmaceuticals Inc [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
Fair value, Beginning Balance	4,901
Fair value adjustment for the year ended December 31, 2015	326
Fair value, Ending Balance	$ 5,227