Business Combinations and Contingent Consideration - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions		1 Months Ended		3 Months Ended	12 Months Ended
	Jul. 17, 2013	Mar. 31, 2016	Mar. 31, 2013	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Apr. 30, 2016	Jul. 31, 2013	Sep. 05, 2012
Business Acquisition [Line Items]
License fees received			$ 3,000,000
Royalties payout percentage on our future net sales of licensed products					20.00%
Ligand Contingent Consideration (Note 10 (b))					$ 0	$ 5,227,000
Acquisition-related contingent obligations					$ (1,300,000)	$ 0	$ 0
IPR&D [Member]
Business Acquisition [Line Items]
Estimated cash flow period					10 years
Estimated cash flow discount rate					25.00%
Milestone Payments [Member]
Business Acquisition [Line Items]
Milestone net sales achievement	$ 5,000,000				$ 60,000,000
Milestone net sales achievement	30,000,000
Ligand Contingent Consideration (Note 10 (b))		$ 6,000,000		$ 6,000,000	7,700,000			$ 6,000,000
Milestone Payment One [Member]
Business Acquisition [Line Items]
Milestone net sales achievement	10,000,000
Milestone net sales achievement	60,000,000
Milestone Payment Two [Member]
Business Acquisition [Line Items]
Milestone net sales achievement	25,000,000
Milestone net sales achievement	100,000,000
Milestone Payment Three [Member]
Business Acquisition [Line Items]
Milestone net sales achievement	50,000,000
Milestone net sales achievement	200,000,000
Milestone Payment Four [Member]
Business Acquisition [Line Items]
Milestone net sales achievement	100,000,000
Milestone net sales achievement	400,000,000
Menadione Topical Lotion [Member]
Business Acquisition [Line Items]
Milestone net sales achievement	5,000,000
Talon Therapeutics, Inc. [Member]
Business Acquisition [Line Items]
Cash consideration	$ 11,300,000
Shares issued in acquisition (shares)	3.0
Common stock value assigned	$ 26,300,000
Common stock value, per share ($ per share)	$ 8.77
Estimated fair value of acquisition	$ 6,500,000
Contingent value rights future cash payments	$ 195,000,000								$ 195,000,000
Talon Therapeutics, Inc. [Member] | Minimum [Member]
Business Acquisition [Line Items]
Contingent value rights expected rate	50.00%
Talon Therapeutics, Inc. [Member] | Maximum [Member]
Business Acquisition [Line Items]
Contingent value rights expected rate	100.00%
Ligand Pharmaceuticals Inc [Member]
Business Acquisition [Line Items]
Ligand Contingent Consideration (Note 10 (b))					6,000,000
Acquisition-related contingent obligations				$ 800,000
Allos Therapeutics, Inc. [Member]
Business Acquisition [Line Items]
Ligand Contingent Consideration (Note 10 (b))					$ 0
Total purchase consideration										$ 205,200,000
Ligand Pharmaceuticals Inc [Member]
Business Acquisition [Line Items]
Milestone net sales achievement		$ 6,000,000