Business Combinations and Contingent Consideration - Change in Fair Value of Contingent Consideration Related to Acquisitions (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Talon Therapeutics, Inc. [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
December 31, 2014	$ 2,379
Fair value adjustment for the three months ended March 31, 2015	310
March 31, 2015	2,689
Ligand Pharmaceuticals Inc [Member]
Change in Fair Value of Contingent Consideration [Roll Forward]
December 31, 2014	4,901
Fair value adjustment for the three months ended March 31, 2015	190
March 31, 2015	$ 5,091